November 2015

NASA/TM–2015-218979

Mock Certification Basis for an Unmanned 

Rotorcraft for Precision Agricultural Spraying

Kelly J. Hayhurst, Jeffrey M. Maddalon, and Natasha A. Neogi 

Langley Research Center, Hampton, Virginia 

Harry A. Verstynen 

Whirlwind Engineering LLC, Poquoson, Virginia 

Barry Buelow and G. Frank McCormick 

Certification Services, Inc., Eastsound, Washington

 
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Space Administration

Langley Research Center 

Hampton, Virginia 23681-2199

November 2015

NASA/TM–2015-218979

Mock Certification Basis for an Unmanned 

Rotorcraft for Precision Agricultural Spraying

Kelly J. Hayhurst, Jeffrey M. Maddalon, and Natasha A. Neogi 

Langley Research Center, Hampton, Virginia 

Harry A. Verstynen 

Whirlwind Engineering LLC, Poquoson, Virginia 

Barry Buelow and G. Frank McCormick 

Certification Services, Inc., Eastsound, Washington
Available from:

NASA STI Program / Mail Stop 148

NASA Langley Research Center

Hampton, VA 23681-2199

Fax: 757-864-6500

Acknowledgment 

This work is supported by space act agreements between NASA Langley Research Center and 

Dragonfly Pictures, Inc. (SAA1-17902) and the University of North Dakota (SAA1-17878).

The use of trademarks or names of manufacturers in this report is for accurate reporting and does not constitute an 

official endorsement, either expressed or implied, of such products or manufacturers by the National Aeronautics and 

Space Administration.
iii

Table of Contents

Preface .........................................................................................................................................................vi

Executive Summary....................................................................................................................................vii

1. Introduction ............................................................................................................................................1

2. Scope and Research Questions...............................................................................................................3

3. Concept of Operations for Targeted Aerial Application Using a UAS..................................................5

3.1. Operational Objectives and Environment Description .................................................................6

3.1.1. Operational Objectives for Targeted Spray Service ........................................................6

3.1.2. Geography .......................................................................................................................7

3.1.3. Airspace Environment .....................................................................................................7

3.1.4. Agricultural Environment................................................................................................7

3.1.5. Economic Environment ...................................................................................................8

3.1.6. Special Safety Features and Considerations....................................................................9

3.1.7. Operational Scenarios....................................................................................................11

3.2. Operational and Airworthiness-Related Observations Regarding ConOps................................16

3.2.1. Operational and Environmental Influence on UAS Design Variables ..........................16

3.2.2. Business Models............................................................................................................17

3.2.3. Summary of Scenario Differences.................................................................................17

3.2.4. Assumptions Regarding the UAS and Precision Aerial Application Service ...............17

4. Approach ..............................................................................................................................................19

4.1. Task 1: Identifying Hazards........................................................................................................20

4.2. Task 2: Evaluating Applicability of Part 27 ...............................................................................23

4.3. Task 3: Generating UAS-unique Requirements.........................................................................24

5. Mock Type Certification Basis.............................................................................................................25

5.1. G-1U Issue Paper........................................................................................................................26

5.1.1. U-1 Issue Paper: Controllability, Maneuverability, and Stability .................................32

5.1.2. U-2 Issue Paper: Structural Integrity .............................................................................34

5.1.3. U-3 Issue Paper: Powerplant and Supporting Systems..................................................36

5.1.4. U-4 Issue Paper: Containment.......................................................................................38

5.1.5. U-5 Issue Paper: Detect and Avoid Intruder Aircraft....................................................41

5.1.6. U-6 Issue Paper: Detect and Avoid Persons and Objects within the Containment Area...

.......................................................................................................................................43

5.1.7. U-7 Issue Paper: Safety-critical Command and Control Datalinks...............................45

6. Potential Systems and Equipment Implementation..............................................................................48
iv

6.1. DP-14 Unmanned Rotorcraft......................................................................................................48

6.2. Ground Control Station ..............................................................................................................50

6.3. Command and Control Datalinks ...............................................................................................51

6.4. Positioning System .....................................................................................................................51

6.5. Assured Containment System.....................................................................................................51

6.6. Ground-Based Detect and Avoid (GBDAA) System .................................................................52

6.7. Active Obstacle Avoidance System............................................................................................52

6.8. Payload and Spray Equipment....................................................................................................53

6.9. Support Equipment.....................................................................................................................53

7. Conclusions..........................................................................................................................................55

8. References............................................................................................................................................57

Appendix. Rationale for the Mock Type Certification Basis.....................................................................59

List of Figures

Figure 1. Notional Prescription Map Illustrating Zones Requiring Treatment............................................5

Figure 2. Life Cycle Phases in Precision Agriculture ..................................................................................8

Figure 3. Relationship of Containment Zone, Operational Area, and Spray Areas...................................10

Figure 4. Overview of Research Approach................................................................................................19

Figure 5. DP-14 Model Rotorcraft from Dragonfly Pictures, Inc..............................................................48

Figure 6. Unmanned Tandem-Rotor Precision-Spray Aircraft..................................................................49

List of Tables

Table 1. VFR Weather Minima for Rotorcraft ...........................................................................................15

Table 2. Primary Differences in Approach to Meeting Functional Capabilities.........................................17

Table 3. Proposed Definitions of Hazards Categories for UAS..................................................................21

Table 4. Primary Hazards for the Unmanned Precision Agriculture Operations........................................22

Table 5. Disposition of Part 27 Regulations for the Mock Type Certification Basis .................................23

Table A.1. Applicability of Part 27 Paragraphs to an Unmanned Aerial Applicator..................................60
v

Acronyms and Abbreviations

ADS-B Automatic Dependent Surveillance-Broadcast 

AGL Above Ground Level

ATC Air Traffic Control

BVLOS Beyond Visual Line-of-Sight

C2 Command and Control

CFR Code of Federal Regulations

CMS Controllability, Maneuverability, and Stability

ConOps Concept of Operations

CPA Conventionally-Piloted Aircraft

DPI Dragonfly Pictures, Inc.

EASA European Aviation Safety Agency

EPA Environmental Protection Agency

ESF Equivalent Safety Findings

FAA Federal Aviation Administration

FARs Federal Aviation Regulations

ft feet

GBDAA Ground-Based Detection and Avoidance System

GCS Ground Control Station

GPS Global Positioning System

HIRF High Intensity Radiated Fields

IFR Instrument Flight Rules

JARUS Joint Authorities for Rulemaking of Unmanned Systems

lb pound

MOA Military Operations Area

mph miles per hour

MSL Mean Sea Level

NAS National Airspace System

NASA National Aeronautics and Space Administration

NOTAM Notice to Airmen

OSHA Occupational Safety and Health Administration

PPS Powerplant and Supporting Systems

RLOS Radio Line-of-Sight

SI Structural Integrity

SWAP Size, Weight, and Power

TCAS Traffic Collision Avoidance System

UA Unmanned Aircraft

UAS Unmanned Aircraft System

US United States

VFR Visual Flight Rules

VHF Very High Frequency

VLOS Visual Line-of-Sight

Vne Never Exceed Speed

WAAS Wide Area Augmentation System
vi

Preface

As part of NASA’s Unmanned Aircraft Systems (UAS) Integration in the National Airspace System 

(NAS) Project, NASA is conducting research to investigate airworthiness requirements for UAS 

performing low-risk commercial operations. The goal of the research is to help fill the void in standards 

needed to certify UAS to operate routinely and safely in the NAS. Specifically, a case study was

conducted to suggest airworthiness requirements for a midsize unmanned rotorcraft performing precision 

agricultural spraying operations over uninhabited fields. The study considered operations in visual lineof-sight, beyond line-of-sight, and in reduced visibility conditions. This report contains research 

prototypes of some of the documentation needed to support airworthiness certification, including a 

proposed (or mock) type certification basis with design and performance criteria for the unmanned 

rotorcraft, corresponding rationale, a concept of operations, and a hazard list. 

This report presents one view of the extent to which existing airworthiness standards for normal category 

(manned) rotorcraft may apply to a midsize unmanned rotorcraft (i.e., approximately 1000 lb with 

payload). The mock type certification basis includes requirements on subjects including flight, design 

and construction, powerplant, equipment, and operating limitations. A complete and expert treatment of 

all requirements relevant to airworthiness certification of a midsize unmanned rotorcraft, such as those for 

noise and fuel venting, is beyond the scope of this effort. Prototype certification artifacts were 

documented using the FAA’s issue paper format, so that their form would be familiar to certification 

specialists and regulatory authorities. 

The concept of operations, description of hazards, and mock type certification basis and rationale are 

intended collectively to provide a plausible picture of the data that influences airworthiness approvals. 

Because this document covers all of the airworthiness standards for normal category rotorcraft in Part 27

of the Federal Aviation Regulations, the report is substantial. Readers may find some specific sections of 

this report more relevant to their interests than others. For example, readers interested in using UAS in 

agricultural pursuits might find the concept of operations (in Section 3) and hazard analysis (in Section 4) 

most valuable. Regulators and UAS developers may be interested in the mock type certification basis (in 

Section 5), whereas the rationale for the certification basis (in the Appendix) might be of interest only to 

regulators. Researchers may find the description of hazards and the concepts for mitigating them (as 

described in Section 5.1-5.7) most relevant.

As part of the case study, NASA selected a representative UAS platform, namely Dragonfly Pictures’ DP14, to demonstrate the plausibility of the design requirements. NASA evaluated the prototype DP-14 to 

confirm that an existing UAS could likely (a) accomplish the aerial application mission with equipment 

based on existing technology and (b) meet the proposed design requirements in the mock certification 

basis. Ideally, the design requirements in the mock certification basis suggest a reasonable starting point 

for establishing airworthiness requirements for UAS such as the DP-14 and other aircraft. 

The work presented in this report has not been vetted by any regulatory authority. Neither the mock type 

certification basis nor any other part of the report represents US Government or FAA policy or guidance. 

Furthermore, this report in no way represents an intent or application for certification on the part of 

Dragonfly Pictures.
vii

Executive Summary

This technical report presents the results of a case study using a hazard-based approach to develop 

preliminary design and performance criteria for an unmanned agricultural rotorcraft requiring 

airworthiness certification. This case study is one of the first in the public domain to examine design and 

performance criteria for an unmanned aircraft system (UAS) in tandem with its concept of operations. 

The case study results are intended to support development of airworthiness standards that could form a 

minimum safety baseline for midsize unmanned rotorcraft performing precision agricultural spraying

operations under beyond visual line-of-sight conditions in a rural environment. 

This study investigates the applicability of current methods, processes, and standards for assuring 

airworthiness of conventionally piloted (manned) aircraft to assuring the airworthiness of UAS. The 

study started with the development of a detailed concept of operations for precision agricultural spraying 

with an unmanned rotorcraft (pp. 5-18). The concept of operations in conjunction with a specimen 

unmanned rotorcraft were used to develop an operational context and a list of relevant hazards (p. 22). 

Minimum design and performance requirements necessary to mitigate the hazards provide the foundation 

of a proposed (or mock) type certification basis. A type certification basis specifies the applicable 

standards an applicant must show compliance with to receive regulatory approval. 

A detailed analysis of the current airworthiness regulations for normal-category rotorcraft (14 Code of 

Federal Regulations, Part 27) was performed. Each Part 27 regulation was evaluated to determine 

whether it mitigated one of the relevant hazards for the specimen UAS. Those regulations that did were 

included in the initial core of the type certification basis (pp. 26-31) as written or with some simple 

modifications. Those regulations that did not mitigate a recognized hazard were excluded from the 

certification basis. The remaining regulations were applicable in intent, but the text could not be easily 

tailored. Those regulations were addressed in separate issue papers. Exploiting established regulations

avoids the difficult task of generating and interpreting novel requirements, through the use of acceptable, 

standardized language. The rationale for the disposition of the regulations was assessed and captured (pp. 

58-115). The core basis was then augmented by generating additional requirements (pp. 38-47) to 

mitigate hazards for an unmanned sprayer that are not covered in Part 27. 

Findings and Results:

The research produced some of the initial artifacts that would be developed in a traditional aircraft 

certification program. Namely, a mock airworthiness certification basis for a midsize (unmanned 

rotorcraft (approximately 1000 lb with full payload) was derived from an analysis of Part 27, along with 

the generation of UAS-specific requirements, based on hazards identified through operational and 

functional hazard assessment. The certification basis also includes seven supplemental issue papers that 

address new or novel aspects of the unmanned agricultural rotorcraft. 

The type certification basis comprises 67 requirements in its core, plus seven additional issue papers. 

Eleven of these requirements were adopted as written from Part 27’s original 260 regulations. A total of 

119 regulations from Part 27 were outright excluded. Of the residual 130 regulations, 56 had their text 

modified for inclusion in the certification basis, while the remaining 74 had their intent abstracted into 

three special issue papers. These three special issue papers (pp. 32-37) detail high level requirements on 

the subjects of: (1) controllability, maneuverability and stability, (2) structural integrity, and (3) 

powerplant and support systems. The issue papers address these topics in a less prescriptive fashion than 

Part 27. The certification basis also includes four additional issue papers (pp. 38-47) that propose 

requirements for new and novel technology not covered in Part 27. The requirements address (1) vehicle 

containment, (2) detection and avoidance of other aircraft, (3) detection and avoidance of ground-based 

obstacles, and (4) command and control links. Altogether, less than 5% of the Part 27 regulations were

deemed applicable verbatim to the derived mock type certification basis, 22% were suitable with textual 

modifications, and 28% were useful, but required substantial re-interpretation.
viii

These results draw attention to the fact that the application of current airworthiness regulations to UAS is 

not straightforward, even for UAS operating in low-risk environments. Indeed, current airworthiness 

regulations may be insufficient to ensure the safety of UAS, due to novel operational concepts and vehicle 

design types and the unique hazards they pose. Furthermore, many regulations, written as they are today,

may not be appropriate because they are not relevant to UAS or present an undue burden to the 

certification process.

The hazard-based approach employed in this research leads to the recognition that airworthiness 

requirements for a UAS are inseparable from its concept of operations. Any airworthiness assessment of 

UAS must address the hazards unique to that UAS’s design and concept of operations. The following are 

major findings in the report:

1. A clearly defined concept of operations is crucial to developing suitable design and performance 

criteria for airworthiness certification of UAS. The operation and UAS must be considered in tandem 

in order to derive the relevant hazards to be mitigated. 

2. A single regulation may act to mitigate multiple hazards. Any proposed modification of an existing 

regulation from an established set of airworthiness standards must be assessed carefully with respect 

to all identified hazards. 

3. Protection of public safety (i.e., avoidance of harm to people in other aircraft and people on the 

ground) is the key driver of airworthiness considerations for UAS. The absence of people aboard an 

unmanned aircraft means that design criteria for manned aircraft might not be directly relevant to the 

safety of the UAS. For example, many design criteria for manned aircraft are intended to address the 

risk of hull loss. But, loss of the hull might not be unsafe in many concepts of UAS operation such as 

precision agriculture. Consequently, design and performance criteria to ensure that hull loss is 

extremely improbable might not be suitable for many UAS. This point represents a significant shift in 

system safety thinking for civil aircraft certification.

This research forms a basis for interpreting the extent to which some established airworthiness 

certification processes and standards for civil aircraft can be applied to UAS. More specifically, the 

results and supporting artifacts from the mock type certification exercise can provide:

 awareness to the UAS industry about operational parameters and assumptions that should be specified 

through a concept of operations document to support development of a type certification basis;

 an example of airworthiness certification artifacts to help inform the UAS industry about civil 

certification;

 a suitable set of design and performance criteria that could be used by regulators as a starting point 

for establishing airworthiness criteria for unmanned rotorcraft intended for low-risk operations; and

 a preliminary point of departure for establishing design and performance requirements (at the level of 

typical airworthiness standards) for new systems and equipment (e.g., a containment system for 

UAS).

These findings and results are based on the development of a research prototype of a type certification 

basis for a fixed concept of operations (precision agriculture) and UAS type (midsize rotorcraft). 

Extensions of this basis to different vehicle types (e.g., fixed wing), concept of operations (e.g.,

surveillance, delivery, etc.), operational environments (e.g., urban, beyond radio line-of-sight, etc.), and 

levels of autonomy will greatly enhance the applicability of the work.
1. Introduction

Three regulatory actions within the past few years have opened the door in the United States (US) for

commercial use of unmanned aircraft systems (UAS): the Federal Aviation Administration (FAA)

Modernization and Reform Act of 2012 [1], proposed rulemaking for small unmanned aircraft [2], and 

launch of the Section 333 exemption process [3]. These regulatory actions are useful for many 

lightweight UAS that can operate in limited risk settings such as operation within visual line-of-sight

(VLOS), under visual flight rules, at low altitudes, and at relatively slow speeds. The Section 333 

exemptions officially relieve a UAS operator of the need to comply with airworthiness regulations, 

pursuant to multiple conditions and operational limitations. UAS with less restrictive operational 

aspirations, such as operation beyond VLOS (BVLOS), will likely require compliance with design and 

performance standards for airworthiness to operate for commercial use. Standardized airworthiness 

criteria for different UAS design types do not exist yet. 

As part of the Unmanned Aircraft Systems (UAS) Integration in the National Airspace System (NAS) 

Project, NASA is conducting research to explore airworthiness requirements for UAS performing lowrisk commercial operations. This effort aims to determine the extent to which some existing aircraft 

certification processes and airworthiness standards are suitable for UAS, and how, if necessary, they may 

be amended to better fit. This work directly supports the FAA’s incremental approach to gaining 

airworthiness approvals by “developing design standards tailored to a specific UAS application and

proposed operating environment” [4]. This work also supports the European Aviation Safety Agency’s 

(EASA’s) efforts to regulate UAS in the “specific” category [5]. This research aims to lay groundwork to 

facilitate development of airworthiness requirements for UAS that would neither qualify under the 

Section 333 exemption criteria (or the “open” category for EASA) nor have sufficient systems and 

equipment to comply with current civil aircraft standards (EASA’s “certified” category). 

At the heart of this research is a case study to put forward a suggested set of design and performance

standards for an unmanned agricultural rotorcraft operating in a rural environment. This case study 

examines a midsize unmanned rotorcraft (i.e., approximately 1000 lb with payload) used to spot-treat 

crops in a precision agriculture context. Ideally, the concept of spot-treatment or targeted aerial 

application using unmanned aircraft will have a number of benefits, both economic and environmental. 

According to a recent National Research Council report [6], the United States lags behind other countries 

in the commercial use of UAS, particularly in agriculture, despite the large potential market. The Section 

333 process enables commercial use of small UAS for agricultural work, especially for aerial surveillance 

and monitoring. However, routine operation BVLOS with larger UAS would have a significant impact

on the growth of the UAS industry. 

The research reported here takes a hazard-based approach to establishing safety criteria midsize 

unmanned rotorcraft. The approach evaluates existing regulation in the Federal Aviation Regulations 

(FARs) Part 27 for normal category rotorcraft, with the goal of determining the extent to which the 

existing regulations apply to an unmanned rotorcraft operating in a low-risk context. The approach was 

influenced by previous work on UAS certification frameworks [7-9]. Evaluation of regulations was 

influenced by the proposed rules for small UAS [2], regulations for light sport aircraft [10], regulations 

for commercial space operations [11], and recent FAA presentations on UAS certification [12]. This 

report focuses attention on some of the initial artifacts developed in a traditional aircraft certification 

program and how those artifacts may differ when applied to a UAS. The artifacts include a mock type 

certification basis that proposes design and performance criteria for a specimen unmanned rotorcraft and a 

concept of operations (ConOps) that defines the objectives for precision agricultural spraying. The report 

also includes rationale for the derivation of requirements in the mock type certification basis, including 

evaluation of airworthiness standards for normal category rotorcraft [13] and a modified variant produced 

by the Joint Authorities for Rulemaking of Unmanned Systems (JARUS) [14]. 
2

The objectives for this research were to:

 investigate the possibility of specifying suitable design and performance criteria (streamlined in 

comparison to current airworthiness standards) as the starting point for establishing airworthiness 

criteria for a specific combination of UAS and concept of operations,

 examine how UAS unique attributes and features can be described in traditional certification program 

artifacts,

 propose design and performance requirements (at the level of typical airworthiness standards) for new 

systems and equipment that are not addressed in existing airworthiness standards (e.g., a geospatial 

containment system), and 

 provide a representative example of certification artifacts to the UAS community.

This report is organized as follows. Section 2 briefly describes the scope and key research concepts, 

especially relevant to UAS certification. Section 3 introduces the ConOps for aerial application using an 

unmanned rotorcraft. Section 4 provides an overview of the approach used to determine primary hazards

for the specimen unmanned rotorcraft and ConOps. That section discusses how those hazards are used to 

derive the content of the mock type certification basis. Section 5 contains the mock type certification 

basis, documented using the form of an FAA G-1, Certification Basis Issue Paper [15]. Additional Issue 

Papers addressing new and novel aspects of the unmanned rotorcraft are included with the certification 

basis. Section 6 describes one possible UAS configuration, using Dragonfly Pictures’ DP-14 unmanned 

rotorcraft as a reference model, that might meet the requirements specified in the ConOps and in the mock 

type certification basis. Conclusions follow in Section 7. Text for the requirements and their rationale in 

the mock type certification basis are included in the Appendix.
3

2. Scope and Research Questions

Several different certificates or approvals are needed for an aircraft to operate for commercial use in the 

NAS. Certification of an aircraft’s airworthiness, meaning that it conforms to its type design and is in a 

condition for safe operation, is one such approval. FAR Part 21 describes procedural requirements for 

issuing these approvals. Three different certificates are relevant to airworthiness certification: a type 

certificate, a production certificate, and an airworthiness certificate. A type certificate is issued for a 

particular design of a civil aircraft, engine, or propeller insofar as it complies with applicable 

airworthiness requirements. A type certification basis identifies applicable regulation paragraphs and 

subparagraphs, exemptions, equivalent level of safety findings, and special conditions that apply to an 

aircraft certification program. The quality system used for manufacturing aircraft is addressed through 

production certification. An airworthiness certificate signifies approval that an aircraft, as built, complies 

with its type design and is in a condition for safe operation. Type certification applies to all aircraft of the 

same design, whereas airworthiness certification applies on an airframe-by-airframe basis. The same 

design and performance standards, however, are the basis for both certificates. This report focuses on 

what those standards might look like for an unmanned rotorcraft system used for precision aerial 

application, including the potential for trade-offs between operational limitations and type design 

requirements for UAS. This report does not consider issues related to production or airworthiness 

certificates or continuing airworthiness for individual aircraft.

The current design and performance standards for conventionally-piloted aircraft (CPA) are often thought 

to be the logical starting point for determining airworthiness standards for most UAS. Those 

requirements represent time-honored best-practices for safe design and lessons learned from incidents and 

accidents. Existing airworthiness standards for CPA levy requirements on aircraft structure, design and 

construction, powerplant and supporting systems, electrical systems, etc. to safeguard the aircraft, and 

hence, safeguard anyone on board. Compliance with those requirements is intended to ensure that hull 

loss or other aircraft-specific failures that could entail harm to onboard passengers and crew are extremely 

improbable. They also have a secondary effect of protecting persons and property on the ground. Key 

questions for UAS are (1) to what extent do existing airworthiness processes and standards apply, given 

that protection of onboard passengers and crew is not necessary? and (2) to what extent can operational 

limitations be used to offset airworthiness requirements? To answer these questions, it is helpful to look 

at key differences in hazards between CPA and UAS and their operations.

Hull loss is always unacceptable in commercial CPA because those on board are likely to be harmed, 

regardless of the operational context. In contrast, operational context is a significant factor in determining 

the safety-related risk1 posed by a UAS [16]. For example, risk posed by a UAS operating in an urban 

environment is significantly different from risk posed by the same UAS operating in an uninhabited 

environment. A number of potential UAS operations exist wherein hull loss presents negligible risk to 

people, because there are no people on board and because there are no uninvolved people expected in 

proximity to the operation. Operations in the Arctic or over vast stretches of farmland are obvious 

examples. Ensuring that hull loss is extremely improbable in those cases is more of an economic issue 

than a safety concern. This point represents a significant shift in system safety thinking for civil aircraft, 

and has implications for UAS airworthiness requirements. EASA has proposed an operation-centric 

framework for regulating UAS to reflect this shift in thinking [5]. 

The case study of a midsize unmanned rotorcraft used for targeted aerial application examines 

airworthiness standards in light of an operational context where risk to others is limited, but not 

eliminated completely. Risk to persons overflown or to other airspace users is minimized in a number of 

ways in the ConOps, including the following.

 

1 References to risk in this report are specific to safety-related risk, in contrast to other types of risk (e.g., security or economics).
4

 Operations will be conducted only over farmland in rural, agricultural areas. The operation does not 

include transit between locations (from an airport to the application site or from one application site 

to another), but could be adjacent to an aviation activity (e.g., conventional crop dusting).

 Operations will typically be very low-altitude, only a few feet over crop height to minimize dispersal 

of chemicals. The UA will not be flown above 400 ft.

 Operations will be constrained to a pre-defined containment volume over the application site.

Although these operational characteristics reduce risk, they do not eliminate it. Failure of the systems and 

equipment on board the UA, in the ground control station, or associated with the command and control 

(C2) links could pose: 

 harm to people in the operational vicinity, primarily crew, e.g., from release of high energy parts from 

loss of rotor system integrity or explosion;

 harm to people in other aircraft, e.g., from failure to detect and avoid other aircraft, particularly aerial 

applicators (i.e., crop dusters) that enter the operational area;

 harm to people on the ground, e.g., from failure to detect and avoid people who may inadvertently 

enter the operational area; or

 harm to people and property beyond the operational area, e.g., from loss of containment (i.e., flight 

beyond the designated containment volume).

The purpose of airworthiness standards is to provide design and performance criteria to mitigate hazards 

that could lead to the outcomes above. The operational limitations set forth in the ConOps play an 

important role in understanding and evaluating hazards and potential mitigations.
5

3. Concept of Operations for Targeted Aerial Application Using a UAS

This concept of operations (ConOps) describes a UAS performing a relatively low-risk operation, namely, 

targeted aerial application of agricultural chemicals such as fertilizers or pesticides to crops (i.e., crop 

dusting). The general concept is to have an unmanned rotorcraft apply chemicals to relatively small areas 

in a field of crops that have been determined to need treatment. This operation is intended to be 

compatible with precision agriculture: applying the right chemical at the right place at the right time. This 

ConOps describes the entire operation, primarily from the perspective of the people performing the 

operation. The information in this ConOps is used to derive information relevant to type certification and 

could also be used to support operational approvals, pilot training requirements, flight manual, continuing 

airworthiness, etc.

Within this ConOps, targeted aerial application is considered to be spot treatment of distinct areas of a 

field of crops, to a level of accuracy of at least 1 meter in either direction [17]. Crop treatment 

instructions are captured in electronic prescription maps that incorporate information regarding crop 

health, field conditions, and agricultural inputs needed for treatment [18]. Prescription maps can be based 

on Landsat or other imaging data, such as data from manned or unmanned aircraft, or may be developed 

by traditional methods, such as direct inspection of fields. The existence of a prescription map suitable to 

allow the generation of a flight plan for the UAS is assumed. The yellow areas in Figure 1 give an 

example of how areas in a field requiring treatment might appear on a prescription map. 

Figure 1. Notional Prescription Map Illustrating Zones Requiring Treatment

An unmanned, midsize rotorcraft was chosen as the target aerial vehicle for this case study. For aerial 

application, a rotorcraft’s ability to operate at very low speeds supports spot treatment of fields. 

Moreover, a rotorcraft’s ability to take off and land without a runway or airport and ability to quickly 

terminate flight with a minimal landing footprint (compared to a fixed wing aircraft with unknown glide 

path) are important to constraining the operation of the UAS to a defined location. Having the operation 

constrained within a well-defined area, in which there is limited possibility of impact with other aircraft 

or people, is important to limiting operational risk in this ConOps. 
6

The unmanned rotorcraft system includes the UA, ground control station (GCS), sensors, C2 links, and a 

spraying system. All operations are conducted using this equipment. The rotorcraft and all of its 

supporting equipment are transported to the application site by ground vehicle(s). The activities 

associated with the spray operation, including preflight, launch, aerial application, refueling, and 

replenishment of chemicals, are performed at the application site.

The rotorcraft is remotely operated by a pilot in command2from the GCS at the application site. The 

pilot in command is the person who has final authority and responsibility for the operation and safety of 

flight of the UA. Additional crewmembers may be needed to assist with tasks such as launch and 

recovery, refueling, observing air traffic and weather, and monitoring the boundaries. 

Operations are conducted by an aerial application service provider (e.g., a crop dusting service) rather 

than by individual farmers or landowners. The service provider is responsible for meeting operational 

requirements for handling chemicals, including those required by the Environmental Protection Agency 

(EPA), as well as training requirements for the pilot in command and crew, and general operating and 

flight rules that may be levied on UAS, such as those in FAR Parts 61, 91, and 137. Those aspects of the 

operation are beyond the intended scope of this work, which is to examine type certification 

considerations.

3.1. Operational Objectives and Environment Description

The following subsections describe the objectives of the spray operation, the environment (geographic, 

airspace, agricultural, and economic) in which the system is intended to operate, notable safety 

considerations, and expectations for routine operational use. The operational information is provided here 

to help identify important safety concerns and key design and operational features that could mitigate 

those concerns.

3.1.1. Operational Objectives for Targeted Spray Service

Listed below are the objectives for aerial application using an unmanned rotorcraft for this ConOps. 

Specific operational activities throughout the phases of operation (from mission planning to landing) are 

described in Section 3.1.6.

1. The UA should be capable of applying liquid agricultural chemicals (e.g., pesticides, insecticides, 

fungicides, herbicides, rodenticides, attractants, repellents, and fertilizers) to spots designated on a 

prescription map of a field. The prescription map could be based on Landsat data or other geospatial 

information sources.

2. The chemicals should be applied at a level of precision of at least 1 meter in either direction.

3. The UA and supporting equipment should be transportable to the operational area over local 

roadways.

The nominal operational area is a 0.25 square mile block of farmland (160 acres). This area is known as a 

quarter section. The GCS and supporting equipment are located in such a manner as to provide adequate 

VLOS and radio line-of-sight (RLOS) for the targeted quarter section and, where feasible, adjacent 

quarter sections to minimize required movements of vehicles and equipment.

 

2 The pilot in command is responsible for remote operation of the rotorcraft, although direct stick-to-servo control (comparable 

to a model aircraft) is not required for the UA in this case study.
7

3.1.2. Geography

In this ConOps, the focus is on targeted application of chemicals to crops grown in largely rural areas 

with significant stretches of farmland. The Red River Valley region of North Dakota and Minnesota

serves as a good example of such a region. Corn, wheat, and soybeans are common crops in the region, in 

addition to specialty crops such as sugar beets. Although many geographic areas would be suitable for 

this operation, choosing a specific geographic area is helpful in identifying realistic safety and 

airworthiness considerations. 

Farmland in the eastern half of North Dakota including the Red River Valley is generally flat prairie land. 

The elevation of the Red River Valley region ranges from 780 feet above mean sea level (MSL) in the 

north to 962 feet MSL in the south.

Farms in the Red River Valley vary in size, with 1,675 acres being an average farm size [19]. Many 

farms are bordered by “wind breaks” of tall trees, often with creeks, rivers, streams, or ponds sporadically 

situated within the growing sections. In general terms, land in North Dakota is symmetrically organized 

by sections of land as established by the national Public Land Survey System, each measuring 

approximately 1 statute mile wide by 1 statute mile long, or 640 acres in total size. Each section is further 

broken into quarters, providing workable quarter-section fields of 160 acres each. 

There are two significant urban areas in the Red River Valley: Grand Forks and Fargo, ND. Most farms 

where aerial spraying is conducted are located in rural, sparsely populated areas. Some farms, however,

abut housing developments.

North Dakota’s climate is characterized by large temperature variation across all time scales, light to 

moderate irregular precipitation, plentiful sunshine, low humidity, and nearly continuous wind. The 

temperature in the growing season (April–September) ranges from about 30 F to 84 F. Average wind 

speeds during the summer range from 10-13 mph, with up to 20-25 mph gusts.

3.1.3. Airspace Environment

The airspace over the Red River Valley to the north of, and including, Fargo, North Dakota is comprised 

primarily of Class G and Class E airspaces. Points to note relevant to potential airspace hazards include:

 The aeronautical sectional chart indicates the existence of some small obstructions (such as grain 

elevators), most around 1000-1300 ft MSL.

 There are two National Wildlife Refuges in the region: Ardoch and Kellys Slough. Both are wetlands 

with significant numbers of birds. 

 There is no Special Use Airspace in the region, although there are several Military Operations Areas 

(MOAs) to the immediate west (Devil’s Lake East/West MOA, Tiger North/South MOA).

Regional airports include Grand Forks International, Grand Forks Air Force Base, and Fargo Hector 

International, as well as numerous smaller airports. Smaller airports include both towered and nontowered airports, glider fields, crop dusting fields, and private airfields.

3.1.4. Agricultural Environment

Precision can be applied to many aspects of farming and crop production, including improved crop 

assessment through various imaging technologies and improved precision in the application of 

agricultural chemicals, as shown in Figure 2. When used to modify “aerial application” or “crop 

dusting,” the word precision indicates that the application need not be to an entire field or at a uniform 

rate.
8

Figure 2. Life Cycle Phases in Precision Agriculture

Improvements in precision can be made with respect to the timing of specific agricultural actions, the 

geospatial accuracy of actions, and the quantities of agricultural chemicals applied. Although aerial 

application of chemicals may support several phases of the life cycle, the prominent role is likely in the 

growing phase.

During the growing phase (summer months), icing conditions rarely occur near ground level. In the rare 

case when they do occur, there would be no agricultural need to conduct spray operations3. Spray 

operations normally occur during low-wind and low-gust conditions to avoid undesirable drift of 

chemicals into unintended areas. Therefore, operations are not conducted during thunderstorms or other 

high wind situations.

3.1.5. Economic Environment

Ideally, the concept of targeted aerial application of agricultural chemicals has a number of benefits, 

including safety, environmental, and economic benefits. Safety benefits include the elimination of risk to 

the (nonexistent) onboard crew and the reduction of risk to others, arising from the use of smaller, lighterweight aircraft. Environmental benefits include more effective chemical usage and therefore less 

chemical runoff. The ability to reduce the overall amount of chemical being dispersed (and thus cost) 

should lead to quantifiable saving on the part of the agricultural enterprise. Furthermore, there are other 

benefits, which, while not easily quantifiable, are expected to have a positive impact. Precision aerial 

application of agricultural chemicals at the right time, in the right place, could increase the value 

associated with yield per acre by: (1) limiting damage to crops from the infestation being treated, (2) 

limiting the physical damage to crops during the application process, (3) reducing soil compaction, and 

(4) and providing a more optimal mix of dispersed product through rotor-wash action. 

This operation comes with attendant costs, which must then be analyzed in the operational context. 

Limiting factors on economics of the operational concept include: width of the spray rig, area covered, 

cost of chemicals applied, fuel, labor etc., and lifecycle costs of the UAS (purchase, operation, and 

disposal). For economic viability, these costs must be benchmarked with respect to current state of the art 

application processes, such as conventional aerial application and tractor-based dispersal. 

 

3 One could conceive of an agricultural spray operation that would be conducted during icing conditions, such as spraying 

chemicals on fruit trees to prevent damage during a late frost. This usage is not considered in this ConOps.
9

Costs

Direct costs are expenses that can be directly attributed to the production and harvesting of the crops. 

These account for 60% of the operating costs. The major direct costs associated with this operational 

concept of precision spraying are: (1) the cost of chemicals applied, (2) fuel costs (for transport and 

operation of the UAS) and (3) labor costs of operating the UAS. It is unclear which of these costs will 

dominate the operational expenses. Chemical costs impact the cost-benefit analysis most directly, as 

quantifiable savings can be realized through a precise application of less chemical, thereby reducing the 

amount of chemical applied. These cost savings directly depend on the precision of the delivery

mechanism. This will be influenced by the guidance system of the vehicle and by the nozzle delivery 

system. The cost of the fuel consumed in the course of the precision application of chemicals is directly 

related to the prescription map, vehicle guidance, navigation and control algorithms and vehicle engine 

efficiency. Labor costs for the precision application of chemicals under the proposed operational concept 

are the least clearly defined. Labor costs will be incurred for the setup and take-down operations at the 

beginning and end of each day. Each individual flight will require pilot and crew time (including, visual 

observers, if any) to monitor the safe operation of the flight and perform fueling and chemical 

replenishing operations. Regulatory bodies are developing training and qualification requirements for the 

pilot and other crewmembers. Costs associated with those activities would constitute indirect labor costs. 

Key Operational Cost/Benefit Factors

The average operational time depends on the average flight time, the number of flights to complete the 

treatment of the quarter section, the time to reload fuel and resupply chemicals, and the time to perform 

setup and take-down activities. 

From an economic standpoint, the average flight time of the system is one of the key parameters of the 

operational design. Frequent returns for refueling (or chemical resupply) will degrade the operational 

efficiency of the precision application function. Flight time can be divided into two components: the 

average time spent applying chemicals (while in flight) and the average time transiting to the area where 

application needs to occur. The average time in transit is dependent on the prescription map, the initial 

deployment site of the vehicle, and the path-planning algorithm. The average time spent spraying is 

dependent on the vehicle’s speed in translational lift (moving from hover to forward flight), the vehicle’s 

precision in spraying an area, and the variable rate of spray, as well as the prescription map. 

Average chemical coverage is the average volume of chemical required to treat a quarter section. This is 

determined by the type of chemical, the rate of application, and the prescription map. Average chemical 

coverage directly influences both cost and timeliness of coverage. The ability to spray a given area with 

increased precision increases savings based on the amount of chemicals applied.

3.1.6. Special Safety Features and Considerations

There are a few special safety features and considerations worth highlighting for this ConOps that are a 

consequence of there being no pilot or passengers onboard the aircraft.

3.1.6.1. Containment

A primary safety consideration is that aerial application will be contained or geospatially bounded. For 

this ConOps, containment can be thought of in the simplest case as a virtual, 3-dimensional dome or box 

surrounding the field that constrains the area of operation. In practice, the height of the containment area 

may be variable so as to limit acceptable altitude near the boundaries. Limiting altitude, especially near 

the boundaries, can help to protect persons and property outside of the containment area from high energy 

debris released in the event of rotor system failure or a crash landing. 
10

Procedures prior to and during operation ensure that no people are in the containment zone. The GCS, 

pilot, and crew are not located within the containment zone but are near the boundaries. The operational 

area, shown as a dashed red line in Figure 3, encompasses all of the areas targeted for treatment. Takeoff, 

aerial spraying, and landing all occur within the operational zone. That zone is completely within the 

containment zone, depicted as the green box in Figure 3. The internal navigation and flight control 

system for the UAS is intended to limit operations to the operational area defined in the flight plan and 

limit the spraying to the spray areas (shown in yellow in the figure). 

Figure 3. Relationship of Containment Zone, Operational Area, and Spray Areas

This ConOps assumes the UAS has a high-integrity approach to ensure the UA remains within the 

containment zone. The containment system provides a safety net, intended to limit the exposure of people 

and property outside of the operational area to UA hazards. The containment function only ensures the 

UA stays inside the containment zone. The containment function does not prohibit people or vehicles, 

including other aircraft, from entering the zone. Thus the containment function does not provide air 

traffic separation (see next subsection). Operating predominately at crop height with a low containmentzone ceiling (400 ft), reduces the chance of an aircraft encounter, but does not eliminate the risk. 

Ensuring that the UA will not exit the containment zone is a key safety requirement.

3.1.6.2. Detection and Avoidance of Other Aircraft, Weather, and Obstacles

Without a pilot onboard who can directly observe other aircraft, static or dynamic obstacles, or weather, 

other means are needed to detect and avoid them. One option is to have ground observers watch the 

unmanned aircraft and its surroundings. For some scenarios in this ConOps, operations take place in 

daylight with visibilities of three miles or greater, thus enabling visual line-of-sight (VLOS) operations. 

VLOS refers to visual observation of UA; that is, operations where visual contact can be reliably 

maintained with an unmanned aircraft. The FAA currently defines VLOS to be within 0.5 nautical mile of 

the UA in flight, at a maximum of 400 feet above ground level (AGL) [20]. VLOS operations can use 

trained observers as the primary means of (1) identifying potential intruder aircraft before they enter the 

containment zone, (2) recognizing changes in weather conditions that might necessitate a change in the 

planned activity (e.g., termination or a change in control mode), and (3) identifying obstacles within the 

containment zone (e.g., farm workers who may inadvertently enter the field or farm equipment that was 
11

not identified in flight planning). Permanent obstacles or other terrain features to be avoided in the 

operational area can be accounted for in geographical databases or by other means. 

Other scenarios in this ConOps include non-VLOS operations, such as operating at night or beyond visual

line-of-sight (BVLOS). In those scenarios, ground observers may not be sufficient. Other means of 

mitigating hazards associated with detecting and avoiding other aircraft, weather, and obstacles are 

needed. Those means may include, but are not limited to, onboard automation to detect and avoid other 

aircraft and unanticipated obstacles, or ground-based detection systems, such as those using ground-based 

radars or acoustics.

3.1.6.3. Hull Loss

For manned aircraft operations, hull loss (i.e., a crash) is considered a catastrophic event, because of the 

potential harm to those on board. In this ConOps, crashing within the containment zone, which is 

monitored to ensure no people are present, is largely an economic concern. Hull loss is only a safety 

concern in situations where energetic departure of rotorcraft parts or pieces can cause harm to people or 

property outside of the containment zone (e.g., the pilot or crew). Any spill of agricultural chemicals

caused by the loss of the hopper contents in a hull loss scenario may also be a safety concern, but is 

considered out of scope for this case study.

3.1.7.Operational Scenarios

Operational scenarios describe ways that a system is envisaged to be used through the various phases of 

operation, which include mission planning, take off, flight, landing, inspection and maintenance. Four

operational scenarios are postulated here. The first is a description of daytime operations that occur 

entirely within VLOS in a rural, agricultural area where there is no aviation activity within three miles. 

The other scenarios build on the first scenario by introducing additional challenges for the UAS design. 

For example, the second scenario is similar to the first, except that spray operations are conducted in an 

area within three miles of known aviation activity (e.g., rural airport, glider port, or aerial applicator 

field). The next two scenarios add nighttime and low visibility operations that cannot be conducted using 

current VLOS rules. Each scenario description only addresses considerations that differ from the 

preceding scenario.

All scenarios assume an airworthy rotorcraft at the outset. All scenarios also assume that adequate 

planning and reconnaissance of the planned area of operations is performed prior to the operation. Preoperation activities are assumed to be governed by FAA-approved handbooks approved for the specific 

commercial activity.

3.1.7.1. Scenario 1 – Daytime Operations Away from other Aviation Activities

In this scenario, operations take place (a) during daylight hours, (b) in good visibility conditions 

acceptable for VLOS operations, and (c) at least three miles away from any other aviation activity (e.g., 

nearby airport or crop dusting operation).

Mission Planning

The mission planning phase includes activities that can be done well in advance of the actual spraying 

task, such as assessment of the physical topography of the fields to be sprayed. Mission planning may 

include both onsite and offsite work. For example, planning may include preflight reconnaissance of the 

target fields to identify permanent obstacles, establish “no fly” zones around those obstacles for flight 

planning, and set containment-zone boundaries. Other activities may include long-range weather checks 

and set up and checkout of ground-based support systems (e.g., multi-lateration sensors). Mission 

planning is expected to be done by the service provider’s management personnel or project planners and 
12

schedulers. The number and location of the support personnel is determined by the service provider 

based on preflight reconnaissance, operational needs, and provisions of the operational approvals given 

by the FAA and other relevant authorities.

Prior to dispatching the UAS for the spray operation, the service provider obtains the prescription map 

specifying the locations, densities, and types of chemicals to be applied, and plans the flight paths 

accordingly.

Preflight

The preflight phase includes day-of-flight activities such as transportation to the field, check out of the 

rotorcraft (much like a manned aircraft preflight check), checkout of the observer communication system, 

final weather checks, C2 system checks, and the preflight briefing for all personnel. These activities are 

done by the crew, which includes the pilot in command, support and maintenance personnel, and possibly 

observers and an onsite operations manager. 

Pre-flight begins with deploying the UA, GCS, datalink, and necessary support equipment to the target 

area of operations. Once on site, the GCS and support equipment are set up outside of the containment 

zone, allowing adequate safety margin for the rotors. The UA is positioned within the containment zone, 

allowing adequate clearance from obstacles above and around the vehicle. Positioning would also 

consider local ambient wind field and slope restrictions for the UA. The UA is configured and inspected 

in accordance with specifications in its continuing airworthiness instructions and operations manual. 

Preflight checks of the UAS, including the spray system, are made per the operations handbook, including 

checks to ensure continuity of the C2 links, checks for weight and balance, and checks of the physical 

systems. All necessary flight information, including containment boundaries, location of stationary 

obstacles, flight plan, and local altimeter information are verified and loaded from the GCS.

The UA is provisioned with fuel and the chemicals to be applied. Safety measures that address the 

handling and loading of both the fuel and chemicals are specified in FAA-approved operational 

procedures. 

While the UA and GCS are being prepared for flight, support equipment and personnel are deployed. 

Support equipment may include the transmitters, sensors, and power equipment necessary to support 

operations. Calibrated positioning sensors might be needed to ensure the prescription map corresponds to 

the locations the UA flies with respect to ground truth. Personnel include visual observers to monitor for 

unplanned obstacles, containment boundary violations, and transient low-flying aircraft. The visual 

observers conduct communications checks with the pilot in command and scan for intruder aircraft and 

unexpected persons or obstacles in the containment zone.

Takeoff and Climb

When all elements of the system are ready, the pilot in command clears the vehicle for takeoff. The UA

is given the command to lift to a hover and does so automatically. Final systems checks are conducted to 

confirm stability and flight readiness. When checks are complete, the pilot in command clears the aircraft 

to initiate the preprogrammed navigation path and pressurize the spray system.

Flight (Prescriptive navigation and spraying)

During the flight phase, the UA operates at an altitude consistent with the spraying requirements, 

typically 10-20 ft above the ground. The UA’s navigation system directs the UA to the first spray 

location avoiding obstacles along the way. For the envisaged operation, the pilot cannot fly the UA via 

direct stick-to-servo control. Once at the first spray location, chemicals are applied according to the 

prescription map while the UA maintains an airspeed chosen to control chemical dispersion and reduce 

fuel consumption. By approaching the spray location from downwind, the ground speed of the UA can be

minimized. This helps to control application concentration and reduce overspray. The UA then continues 

to the other spray locations per the flight plan. The vehicle design and operational procedures include 
13

safety measures to ensure that the spray system cannot inadvertently activate or apply chemicals to 

locations other than those designated in the prescription map.

Ensuring that the UA stays within the containment zone is a key safety function that the pilot performs 

with the assistance of the visual observers. The containment function ensures the UA always stays within 

the containment area. If the UA breeches the operational area (see Section 3.1.6.1), visual observers (or 

the pilot) will identify this condition and communicate this to the pilot in command, at which time the 

pilot will take corrective action. The pilot’s command, sent via a dedicated link, will activate an 

independent contingency response system to bring the vehicle down immediately, thus ensuring the UA 

remains in the containment zone. This action may or may not preserve the integrity of the airframe. 

Landing on the crops is assumed to be acceptable. Otherwise, a designated safe landing spot may be 

used. 

The C2 link might fail anytime during flight. To address this possibility, the C2 link is continuously 

monitored. If the link is lost for longer than a defined duration, the independent contingency response 

system is activated. Other failure events that affect the navigation, guidance, control, or safety systems 

will also cause the UA to land at its current location (assuming the absence of obstacles). The 

contingency response system described above may be used at any time to mitigate UA failure conditions, 

such as loss of positioning data.

Detecting other aircraft that may enter the containment zone is an important safety activity accomplished

with the help of visual observers. The observers monitor the local airspace for low-flying aircraft and 

potential obstacles. When another aircraft that could pose a conflict is detected, that information is 

communicated to the pilot in command. The pilot in command then sends a command to the UA to 

execute a preprogrammed avoidance maneuver (e.g., to land or go into a low hover). When the 

conflicting traffic has passed, a command to resume is sent from the GCS. A ground-based aircraft 

detection system could also be designed to automatically send a command to the UA. In that case, the 

pilot would serve as a backup.

Obstacles are avoided during operations in two ways. First, known (static) obstacles are avoided based on

“no fly” zones established during mission planning. Unanticipated obstacles within the containment zone 

are detected by the visual observers or, if available, by an on-board obstacle detection system4. It is 

unlikely that a UAS in a rural environment would need to perform complex obstacle avoidance or returnto-path maneuvers. 

Visual observers also watch for changes in the weather. Observers communicate significant changes in 

weather to the pilot in command, who orders contingency maneuvers if they are warranted.

Descent and Landing

When the UA has completed the programmed path, reached minimum fuel or payload levels, detected an 

onboard failure, or is commanded by the pilot, the UA returns to the designated landing spot. Upon 

arrival, the UA executes an automatic approach and landing to allow refueling and chemical re-supply

and any necessary inspection and maintenance.

3.1.7.2. Scenario 2 – Daytime Operations Near an Aviation Activity

In Scenario 2, daytime operations are conducted within three miles of an airport or aviation activity (e.g., 

aerial chemical application). In this scenario, the required capabilities and protocols are the same as 

Scenario 1 except for communication and notification. Communication and notification involve 

 

4

It may be possible to implement an on-board obstacle detection system using lidar, radar, infrared cameras, or visible light 

detectors, or combinations of sensors as permitted by size, weight, and power (SWAP) and cost constraints.
14

conveying information about the UAS operations to nearby aviators and operators, as well as monitoring 

communications from those activities.

In this scenario, the airport and any other aviators and operators within three miles are notified of the 

planned UAS operations. This might be accomplished by filing a Notice to Airmen (NOTAM) or posting

a notice at a non-towered airport notifying manned aircraft operators of the dates and times of the planned 

UAS operations. The preflight briefing for the pilot and visual observers should include information 

about nearby aviation activities.

During UAS operations, the pilot in command is responsible for monitoring very high frequency (VHF)

communications on the appropriate air traffic frequencies, if available. When operations are in progress, 

the pilot in command maintains a listening watch on the local Unicom or other appropriate frequency and 

notifies manned aircraft if the UAS breaches the containment zone. If the airport has an operating control 

tower, the pilot in command monitors the control tower frequency to be responsive to any 

communications from the tower.

These communications protocols do not substitute for the requirement to detect other aircraft, but do help 

provide “alerted see and avoid” for other airspace uses and remote crew. The procedures to be followed 

in the event of a potential conflict with another aircraft are the same as Scenario 1.

3.1.7.3. Scenario 3 – Nighttime Operations

Aerial spraying operations at nighttime5 have potential benefits and limitations both from an operational 

and agricultural perspective. Winds at night are typically lower, which allows easier and more accurate

aircraft control and positioning for precise spraying. There is substantially less general aviation traffic at 

night and the potential exposure to other low-level aircraft is minimal because of restrictions on nighttime 

aerial work for manned aerial applicators. On the agriculture side, some crops are more amenable to the 

application of certain chemicals at night.

However, it is harder to see aircraft (traditionally piloted or otherwise) at night. The use of strobes on the 

UA can increase the likelihood that other aircraft will see it and that it will be seen by its pilot and 

observers. Noise restrictions may present a challenge for nighttime operations. Detecting ground-based 

obstacles is more difficult at night. Increased emphasis on strategic measures (e.g., mapping of obstacles) 

would be needed to maintain safe separation. 

Scenario 3 involves nighttime operations that may or may not occur near an aviation activity. In this 

ConOps, night operations differ from day operations primarily in three ways. Because the pilot and 

observers may fail at nighttime to notice (1) whether the UA remains in its containment area, (2) whether 

other aircraft have entered the area, and (3) the presence of obstacles on the ground, there must be an 

automated means to mitigate these hazards. The contingency response is largely the same as Scenario 1 

except that the contingency action could be initiated by automation in addition to pilot action. Due to the 

significant safety role of the containment function, all parts of this system, including location sensors,

must operate with high integrity. If the pilot determines that the UA violates the operational area without 

triggering the containment system, the pilot has the means to bring the aircraft down through the 

contingency action. In this case, all operations cease until the cause of failure of the automated 

containment function is determined. 

Using visual observers to detect other aircraft at night is not generally applicable to this scenario. 

Nighttime operations require an additional approach to detecting other aircraft. A low-cost, automated 

detect and avoid system is not currently available for the civil UAS market, though one could be 

developed using existing technology. It is possible to imagine a Ground-Based Detect-and-Avoid System 

 

5 Night, per FAR Part §1.1, means the time between the end of evening civil twilight and the beginning of morning civil 

twilight, as published in the Air Almanac, converted to local time.
15

(GBDAA) that is a small, portable, and radar-based. The GBDAA system could operate continuously 

during flight operations and provide the pilot in command with a distinctive warning if an intruder aircraft 

is detected within a predetermined range of the operation. Given a warning from the GBDAA system, the 

pilot in command would activate the independent contingency response system (e.g., land immediately or 

hover), just as he or she would when warned by a visual observer. Once the intruder has passed, the UA

would be permitted to resume normal operations. 

Finally, day and night operations also differ with respect to active obstacle detection on the ground. 

Ground intruders (e.g., livestock or people) become difficult to detect at nighttime; even if they also 

become less likely. Obstacles such as mobile irrigation systems that might not have appeared on original 

maps of the field are also more difficult to detect at nighttime. For night operations, an approach other 

than visual observers is needed to detect unexpected obstacles in the field. If that approach uses an onboard detection system, the sensor for the system must be shown to be capable of detecting obstacles at 

night. Any ambient light requirements for the sensor to operate should be specified in the operations 

manual as operational limitations.

There are other, more minor, differences between day and night operations. The UA must be equipped 

with position and anticollision lights to permit visual confirmation of UA position and orientation.

Lighting is also needed on the ground to support refueling, reloading, and inspecting the UA.

3.1.7.4. Scenario 4 – Operations Beyond Visual Line-of-sight

Scenario 4 is for operations beyond visual line-of-sight (BVLOS), but within radio line-of-sight (RLOS)

that may or may not be near an aviation activity. BVLOS operations include those where visual contact 

cannot be reliably maintained with an unmanned aircraft due to distance, obstructions, or atmospheric 

conditions. Early morning fog or low lying clouds are examples of low visibility conditions relevant to 

aerial spraying operations. There are some advantages to operating in degraded visual conditions. For 

example, it is unlikely that other aircraft will be operating at low altitudes under visual flight rules (VFR). 

Required capabilities (for detecting and avoiding other aircraft and obstacles and remaining within the 

containment volume) remain the same as in the other scenarios, except the means to provide those 

capabilities cannot rely solely on human vision. 

VFR minima for conventionally-piloted rotorcraft per 14 CFR §91.115, shown in Table 1, differ 

depending on whether operations are conducted in Class D, E or G airspace. 

Table 1. VFR Weather Minima for Rotorcraft

Airspace Flight Visibility Distance from Clouds

Class A None None

Class B 3 statute miles Clear of clouds

Class C 3 statute miles 500 feet below

1,000 feet above

2000 feet horizontal

Class D 3 statute miles

Class E

less than 10,000 MSL 3 statute miles

at or above 10,000 MSL 5 statute miles 1,000 feet below and above

1 statute mile horizontal

Class G

1,200 feet or less AGL

Day .5 statute mile Clear of clouds

Night 1 statute mile 500 feet below

1,000 feet above

2000 feet horizontal

more than 1,200 AGL but less 

than 10,000 MSL

Day 1 statute mile

Night 3 statute miles

more than 1,200 AGL and at or above 

10,000 MSL 5 statute miles 1,000 feet below and above1 statute mile horizontal
16

Agricultural operations will presumably take place in Class G airspace, where air traffic control does not 

provide clearance from other aircraft, but VFR minimums are known by pilots. VLOS operations 

covering quarter sections would require less than one mile visibility. In theory, VLOS operations could 

be conducted in Class G airspace with one mile visibility and clear of clouds except for the requirement to 

detect other aircraft at a range sufficient for the UA to conduct an avoidance maneuver. Procedures for 

operations with visibility below one statute mile are virtually the same as night operations: a means to 

detect other aircraft (such as a GBDAA system) will be needed. 

The active obstacle detection system should be shown to operate successfully in restricted visibilities if 

observers cannot see the boundaries of the operational area. Low visibility operations might also 

necessitate some means to establish when visibility is above or below approved minima.

3.2. Operational and Airworthiness-Related Observations Regarding ConOps

Design parameters and level of automation needed for UAS are strongly influenced by operational, 

environmental, and economic considerations. The subsections below describe how these considerations

for aerial application may impact the design for an unmanned agricultural sprayer. This information 

provides background data for some of the assumptions underlying the type certification basis.

3.2.1. Operational and Environmental Influence on UAS Design Variables

3.2.1.1. Tank Volumes (Fuel and Chemical Capacity)

The fuel and chemical tanks affect the weight, balance, and endurance of the UA, as well as the potential 

energy available to cause damage in case of an accident. The tanks’ contents are part of the vehicle’s 

payload and are subject to weight limits. 

Different fields will have different transit and spray requirements, depending on the size and condition of 

the field. Ideally, the design of the fuel and chemical tanks would allow for variable fuel and chemical 

loadings. An optimal design for the tanks would minimize the number of refueling and resupply 

operations for the targeted fields, while having minimal effect on balance as the fuel and chemical tanks 

are depleted. Ideally, the fuel remaining would be just sufficient to return the UA to the ground transport 

vehicle with appropriate reserves.

3.2.1.2. Guidance and Navigation

The precision with which the chemicals will be applied is a critical factor in the UAS design. Precision 

aerial application will likely require greater navigation accuracy and control than that needed to meet 

safety requirements (e.g., to stay clear of obstacles and boundaries). The guidance, navigation and control 

systems must have sufficient accuracy to navigate to and spray targets with the precision required to 

achieve cost savings and avoid (over-) spraying unnecessary areas. Insomuch as the guidance and 

navigation equipment does not affect safety requirements or constraints, its accuracy and reliability 

impacts only the profitability of the operation (e.g., through repair, lost operational time, wasted 

chemicals, or damaged crops).

3.2.1.3. Visual Observers and Electronic Surveillance

Tradeoffs exist between using visual observers in VLOS conditions and relying upon electronic 

surveillance equipment to ensure that the UA remains in its containment zone and clear of ground 

obstacles and other aircraft. Because the cost of certifying electronic surveillance systems might be 

substantial, the cost to use visual observers (including training costs) might be less burdensome in the 

short term. The cost of employing visual observers will depend on the number needed, duties assigned, 

and the level of training required. If the quality of surveillance provided by visual observers and certified 
17

electronic equipment is equivalent, a straightforward cost-benefit analysis can be made between the two. 

The analysis should take into account that electronic surveillance will enable aerial application at 

nighttime, in inclement weather, and at beyond VLOS maximums (Scenarios 3 and 4). Operating under 

these conditions may provide significant benefits, especially in terms of timeliness of application, and

overall increased yield.

3.2.2. Business Models

The business model impacts UAS design parameters, especially regarding the degree to which the design 

needs to accommodate operators and maintenance personnel at a variety of training and skill levels. This 

ConOps assumes a service-provider model, but an owner-operated model could also be considered. The 

benefit to the farmer of the service provider model is that the farmer does not need to invest the time and 

capital upfront and, perhaps more importantly, does not need to employ skilled workers to operate the 

aerial spray equipment. The advantages of owning the equipment are the elimination of the operator’s 

profit as a cost and (perhaps more importantly) the ability to deploy the equipment on the farmer’s own 

schedule. 

3.2.3. Summary of Scenario Differences

Some scenarios in the ConOps will require automated equipment that is not necessary in other scenarios.

Visual conditions and proximity to other aviation activities affect the level of automation required for the 

UAS. In the VLOS conditions in Scenarios 1 and 2, visual observers may be sufficient for ensuring 

containment and detecting intruder aircraft or ground-based obstacles within the containment zone. The 

limited visibility conditions in Scenarios 3 and 4 (nighttime and low visibility conditions) will require 

automated systems to ensure that the UA stays within its containment zone, to detect intruder aircraft, and 

to detect unanticipated ground-based obstacles. Scenarios 2, 3, and 4 assume the need for an aviation 

radio to communicate with aviators and operators external to the spraying operation. Table 1 summarizes 

differences among the four scenarios. 

Table 1. Primary Differences in Approach to Meeting Functional Capabilities

Functional Capability

Scenario 1

Daytime Operations 

Away from other 

Aviation Activities

Scenario 2

Daytime Operations 

Near an Aviation 

Activity

Scenario 3

Nighttime 

Operations

Scenario 4

Operations Beyond 

Visual Line-of-sight

Ensuring containment Visual observers Visual observers Automated 

containment system

Automated 

containment system

Detecting intruder 

aircraft Visual observers Visual observers Automated detection system (e.g., GBDAA)

Automated detection 

system (e.g., GBDAA)

Detecting ground-based 

obstacles Visual observers Visual observers

Automated detection 

system (e.g., groundbased obstacle 

detection system)

Automated detection 

system (e.g., groundbased obstacle 

detection system)

External communication 

(e.g., with local airport) N/A Aviation Radio Aviation Radio Aviation Radio

3.2.4. Assumptions Regarding the UAS and Precision Aerial Application Service

Understanding the assumptions underlying the operation of a UAS is necessary to properly identify 

potential hazards and requirements necessary to mitigate them. Listed below are the key assumptions 

about the aerial application operation and the unmanned rotorcraft for this ConOps. These assumptions 
18

are derived directly from the information in Section 3.1 and represent key airworthiness-related 

requirements. 

1. The UA will have no people on board.

2. The UA will be capable of safe takeoff, flight and landing in the designated operational environment, 

including the ability to operate in the relevant elevations, winds, wind gusts, and temperatures. 

Operations will not be conducted during high winds, thunderstorms, or icing conditions.

3. Operations will be conducted in rural, agricultural areas. However, these areas might be near some 

human presence (e.g., farmhouse or field in which people are working) or other aviation activities.

4. Chemicals will be applied only to designated areas within the field. The probability of unintended 

application of chemicals on any other agricultural field, or stream, roadway, or populated parcel of 

land will be minimized.

5. The UA will be a rotorcraft with weight and operating characteristics that would preclude operation 

under forthcoming FAA small UAS rules [2].

6. The UA will have only one pilot in command and the pilot in command will only be responsible for 

one UA during a flight. The pilot is required to participate in the management of the flight using the 

GCS. Autonomous operations, defined here as where pilot intervention is not allowed in the 

management of the flight [21], are not permitted.

7. The UA will navigate automatically to the areas designated for spot treatment. The UA will follow a 

flight plan based on the prescription map. Direct stick-to-servo control (comparable to a model 

aircraft) is not required in any mode of operation (e.g., nominal, emergency, etc.).

8. The UA will typically operate a few feet over the crops. Maximum altitude is set at 400 feet above 

ground level, sufficient to avoid ground-based obstacles (e.g., stand of trees).

9. The UA will operate only within a predefined, bounded area or containment zone over the fields to be 

sprayed. The UA will not be required or permitted to operate at airports or in corridors between a 

base location and the application area.

10. The containment zone will be cleared of people prior to operation and monitored to ensure that no one 

enters during the operation.

11. The UA crashing (commonly referred to as hull loss) within the containment zone is not considered a 

safety concern except in instances where energetic departure of any parts, pieces, or chemicals could 

harm people or property outside of the containment zone. 

12. Operations will be conducted initially in daylight with good visibility conditions. With increasing 

experience and maturation of the activity and appropriate equipage, operations may be extended to 

night and in limited visibility conditions.

13. Operations will be conducted only within RLOS. The edges of the containment zone must be within 

RLOS of the GCS. 

14. A means of detecting and avoiding other aircraft, permanent obstacles (e.g., silos or sheds), and other

obstacles, animals or persons on the ground (e.g., livestock and farm equipment) in all operational 

conditions will be needed.

15. Communication and notification about the aerial application operation will be provided as needed 

when operations are conducted in the vicinity of an aeronautical activity (e.g., glider port, aerial 

applicator field, etc.). 

16. Operations will not occur in Class A. Operations will not occur in Class B or C airspace, without an

airspace specific approval. 
19

4. Approach 

Airworthiness standards for new or novel CPA (e.g., a tilt-rotor aircraft) are typically derived from 

applicable parts of existing standards (e.g., FAR Parts 23, 25, 27, 29, and 33) with any additional 

requirements for unique features crafted as special conditions. The standards focus on the aircraft 

systems and equipment, with minimal consideration of the operational context. Operational limitations, if 

any, are typically associated with operational conditions such as icing and oceanic operations. For a 

UAS, however, considering the concept of operations (ConOps) and associated operational limitations 

was unavoidable from the start. The operational context strongly influences the severity of the 

consequence of failure of the UAS, especially for short range operations such as those associated with 

agriculture.

There were three major tasks involved in investigating airworthiness requirements for the specimen 

unmanned aerial applicator, following the development of the ConOps. Figure 4 shows those tasks, the 

products produced by each, and how these products relate to the content of the mock type certification 

basis. Each task is explained in the following subsections.

Figure 4. Overview of Research Approach
20

4.1. Task 1: Identifying Hazards 

The approach to developing content for the mock type certification basis taken here is hazard-based; that 

is, the requirements in the certification basis are largely determined by the hazards and associated risks 

that need to be managed. Hazard and risk assessment processes are, by their nature, subjective. 

Alternative hazard and risk assessment techniques exist, and the discovery of new hazards or safety 

insights could alter the proposed certification basis. 

Identifying hazards associated with the unmanned aerial applicator and its operation is fundamental to the 

approach used here. The first task was to identify hazards that could cause harm to people or property. 

These include UAS-specific hazards associated with the failure of aircraft functions and operational 

hazards associated with the mission and crew. Traditional aircraft hazards such as loss of control and loss 

of navigation were considered. New hazards related to the ConOps, such as loss of containment (i.e., 

exceeding the virtual boundary for the operation) were also considered. 

To the extent possible, conventional system safety processes and tools from the civil aircraft domain were 

used to identify hazards for the unmanned aerial applicator. Guidance for operational safety assessment 

from RTCA DO-264 [22] was used to help identify and classify operational hazards based on the 

ConOps. DO-264 was written to support the use of data communication services such as data link, but its 

guidelines are fitting for UAS operational safety. The standard can be tailored for UAS requirements in a 

straightforward manner. Guidance on functional hazard assessment from SAE ARP 4761 [23] was used 

to help identify failure conditions and functional hazards specific to the UAS. ARP 4761 describes 

various assessment and analysis methods (e.g., functional hazard assessment, preliminary system safety 

assessment, and fault trees) useful for understanding and managing risks on a new aircraft program. 

These methods allow an aircraft developer to systematically examine the aircraft’s functions, classify 

proposed failure conditions according to their severity, and suggest ways to mitigate expected hazards. 

Traditional hazard categories (catastrophic, hazardous, major, minor, and no effect) are defined in FAA 

Advisory Circulars for different aircraft categories (e.g., FAA Advisory Circular 23.1309-1E for general 

aviation aircraft [24]). Because loss of life is a realistic expectation with loss of a CPA, hull loss is 

directly tied to the definition for catastrophic hazards. For UAS, a hull loss event is not necessarily 

catastrophic. Depending on the operational context, hull loss of a UAS may not present a safety risk to 

life at all. Consequently, the severity definitions were tailored for use in this study, as shown in Table 3. 

The severity definitions in Table 3 are similar to those recently offered by JARUS [25] and EASA [26], 

but emphasize the safety role of the pilot and crew and replace emphasis on hull loss with language 

specific to safety margins. Per these definitions, hull loss without consequence to people would not be

considered a loss or reduction of safety margin. Hull loss would be a loss of safety margin in operational 

environments where fatality is possible. Any event that would incapacitate the crew to the extent that they 

could not perform an assigned safety role, such as issuing a command for a contingency maneuver, would 

also be considered catastrophic. 

The goal of the hazard assessment for this research was not a definitive assessment of severity for each 

hazard associated with the UAS, but a broader evaluation of whether the potential consequences of a 

hazard necessitate a design or performance standard comparable to those in Part 27. Only those hazards 

whose consequence was considered major or worse (hazardous or catastrophic) were included on a list of 

hazards that should be mitigated by requirements in a certification basis for an unmanned aerial 

applicator. Those hazards and the rationale for them (based on the severity of their consequence) are 

shown in Table 4. 
21

Table 2. Proposed Definitions of Hazards Categories for UAS

Catastrophic: Failure conditions that are expected to result in: 

1. fatality or fatal injury to any person;

2. complete loss of safety margins (e.g., hull loss for a manned aircraft or fly away6for an unmanned aircraft); 

or 

3. complete loss of the UAS crew’s ability to perform their safety role (e.g., from incapacitation). 

Hazardous: Failure conditions that would reduce the capability of the aircraft or the ability of the crew to cope 

with adverse operating conditions to the extent that there would be the following:

1. serious injury to any person; 

2. a large reduction in safety margins (e.g., loss of separation) or functional capabilities; or

3. serious impairment of the crew’s ability to perform their safety role (e.g., failure inducing a high workload).

Major: Failure conditions that would reduce the capability of the aircraft or the crew’s ability to cope with 

adverse operating conditions to the extent that there would be:

1. physical distress, possibly including injuries, to any person;

2. a significant reduction in safety margins or functional capabilities; or

3. a significant impairment of the crew’s ability to perform their safety role (e.g., failure inducing a significant 

workload).

Minor: Failure conditions that would not significantly reduce aircraft safety and involve crew actions that are 

within their capabilities. Minor failure conditions may include: 

1. discomfort to any person;

2. a slight reduction in safety margins or functional capabilities;

3. a slight reduction in the crew’s ability to perform their safety role (e.g., minor distraction or use of emergency 

procedures).

No Safety Effect: Failure conditions that would have no effect on safety (that is, failure conditions that would not 

affect the operational capability of the aircraft or impact the crew’s ability to perform their safety role).

Because hull loss is not catastrophic under the ConOps, a number of traditional CPA hazards, such as loss 

or degradation of thrust or inadequate fuel, are not considered primary hazards. Hazards relevant to 

security (such as failure to prevent unauthorized access to command/control link), or crew (such as failure 

to verify communication between UAS crew and pilot), were considered beyond the scope of 

airworthiness requirements. The list of hazards and hazard severity definitions strongly influence the 

design and performance criteria specified in the mock type certification basis, but are not explicitly 

included in it, as per Figure 4.

 

6 The term “fly away” is used in this report to mean “an interruption or loss of the control link, or when the pilot is unable to 

effect control of the aircraft and, as a result, the UA is not operating in a predicable or planned manner” [27]. A fly away event 

typically involves a UA that leaves its designated operational boundaries.
22

Table 3. Primary Hazards for the Unmanned Precision Agriculture Operations

Hazard Rationale (for why it should be addressed by regulation)

1. Loss of C2 link used for contingency 

management (e.g., flight termination command 

issued from the ground control station)

Potential for large loss of functional capability and reduction in safety margin.

For example, the pilot will not be able to issue a flight termination command if 

needed. 

2. Loss of or degraded electrical power in the 

ground control station for contingency and 

emergency functions

Potential for large loss of functional capability and reduction in safety margin.

For example, the pilot will not be able to issue a flight termination command if 

needed. 

3. Loss of or degraded electrical power 

subsystems on UA for contingency and 

emergency functions

Potential for large loss of functional capability and reduction in safety margin.

For example, a command for flight termination, if needed, may not be executed 

on the UA. 

4. Loss or degradation of ground control 

station capability (e.g., loss of displays) 

required for contingency and emergency 

functions

Potential for large loss of functional capability and reduction in safety margin.

For example, the pilot will not be able to issue a flight termination command if 

needed. 

5. Loss of UAS position and anti-collision 

lights (loss of means to be seen by other 

aircraft and observers)

Potential for large or complete loss of functional capability affecting safety.

For example, other aircraft may not see and hence, avoid the UA, and the crew 

may not be able to track the UA. Lighting is not relevant for daytime, VLOS 

operations.

6. Loss of or inadequate structural integrity, 

especially of the rotor system

Potential for fatality or fatal injury from high energy parts exiting the 

containment zone.

7. Loss of or degraded communication 

between pilot and crew

Potential for significant loss of functional capability and safety margin. For 

example, observers cannot communicate effectively or promptly with the pilot 

in cases where they need to provide safety alerts (about obstacles, incoming 

aircraft, or breach of boundary, etc.) in VLOS operations.

8. Failure to detect, alert or warn, and avoid 

intruder aircraft

Potential for complete loss of safety margin, leading to fatality or fatal injury. 

This includes observers failing to detect and warn about intruder aircraft, pilots

failing to act to avoid the aircraft, or failure of an automated system to do so.

9. Failure to detect, alert or warn, and avoid 

dynamic or other obstacles on the ground

Potential for complete reduction in safety margin, leading to fatality or fatal 

injury. For example, crew may fail to detect a person or unplanned obstacle 

such as a tractor that may enter field in VLOS operations, or supporting 

onboard instrumentation may fail to detect and avoid obstacles.

10. Failure to recognize and avoid adverse 

environmental conditions (e.g., low visibility

or high winds) beyond operational limits

Potential for large or complete reduction in safety margin. For example, crew 

may be unable to see the UA, intruder aircraft, or ground-based obstacles in 

poor visibility conditions and act as needed to avoid collisions. 

11. Failure or degradation of the flight 

containment function

Potential for complete reduction in safety margin. For example, observers may 

fail to detect and notify pilot of impending violation of the containment 

boundary in VLOS operations or an automated system may fail to detect and 

avoid breach of the containment boundary.

12. Loss of situational awareness by the pilot Potential for large or complete loss of safety margin. For example, without 

appropriate situational awareness, the pilot may not act when needed, or may 

take an inappropriate action. Loss of situational awareness may be due to 

inadequate or misleading flight data. 

13. Interference of spray system with required 

UAS function

Potential for large or complete loss of functional capability or safety margin, 

on the UA or ground control station. For example, the spray system may affect 

the UA’s aerodynamics and controllability.

14. Explosion in the powerplant or fuel system Potential for fatality or fatal injury from high energy parts exiting the 

containment zone.

15. Failure to maintain adequate 

controllability, maneuverability, and stability

Potential for a significant loss of functional capability and safety margin, 

especially when operating near the edge of the containment volume. For 

example, loss of controllability may affect the UAs ability to stay within the 

containment boundary. 
23

4.2. Task 2: Evaluating Applicability of Part 27 

The second task was to specify reasonable design and performance criteria for the unmanned aerial 

applicator. The Part 27 standards for normal category rotorcraft and the UAS-tailored version from 

JARUS provided a practical starting point. Ideally, those standards mitigate airworthiness hazards for 

rotorcraft that are similar in many respects to the specimen unmanned rotorcraft. The need to prevent hull 

loss, however, is a significant difference. For this task, each paragraph in Part 27 was evaluated for 

applicability to the unmanned aerial applicator, with respect to the hazards in Table 4. That effort

identified Part 27 regulations that apply “as is” to mitigate the primary hazards, those that apply with 

some simple modifications, and those that may not be applicable at all. As shown in Figure 4, the 

paragraphs accepted “as is” and those that were modified constitute the main set of requirements in the

mock type certification basis for the unmanned rotorcraft. 

Many of the Part 27 paragraphs, however, were not easy to place in one of those three categories. In 

particular, several Part 27 requirements that address controllability, maneuverability, and stability (CMS), 

structural integrity (SI), and powerplant and supporting systems (PPS) seemed applicable to some degree, 

but not as written nor easily modified. In some cases, the original requirement serves primarily to protect 

onboard crew and passengers, but might also protect crewmembers or others on the ground (e.g., from 

high energy debris). In other cases, the original requirement contains details very specific to normal 

category rotorcraft (e.g., limit load factors) that could not be easily modified without subject matter 

expertise and UAS-specific data. To address these issues, the relevant content from Part 27 requirements

for CMS, SI, and PPS was generalized or “rolled up” into broad sets of requirements that focus on 

preservation of the rotor system to prevent harm from release of high energy debris and explosion. Each 

“roll-up” (CMS, SI, and PPS) allows all of the requirements on a topic to be considered in a holistic way 

in the context of the details of the design. The roll-up process resulted in three new technology issue 

papers included in the mock certification basis. Each Part 27 requirement included in one of those issue 

papers is explicitly enumerated in the corresponding issue paper. Requirements may appear in multiple 

new information issue papers.

Table 5 shows the disposition of the Part 27 regulations. 

Table 4. Disposition of Part 27 Regulations for the Mock Type Certification Basis

Part 27 Included as 

Written

Included with 

Simple 

Modifications

Rolled Up Excluded

Subpart A: General 0 0 0 2

Subpart B: Flight 1 1 14 11

Subpart C: Strength Requirements 0 2 10 25

Subpart D: Design and Construction 2 8 20 32

Subpart E: Powerplant 4 7 24 23

Subpart F: Equipment 1 22 1 16

Subpart G: Operating Limitations and Information 1 13 5 8

Appendix A: Instructions for Continued Airworthiness 2 2 0 0

Appendix B: Airworthiness Criteria for Helicopter 

Instrument Flight

0 0 0 1

Appendix C: Criteria for Category A 0 0 0 1

Appendix D: HIRF Environments and Equipment HIRF 

Test Levels

0 1 0 0

TOTAL 11 56 74 119
24

Altogether, of the 260 regulations contained in Part 27, only 11 are included as written in the certification 

basis: 119 regulations from Part 27 are outright excluded. Of the residual 130 regulations, 56 have had 

their text modified for inclusion in the certification basis, while the remaining 74 have had their intent 

abstracted into the three special issue papers for CMS, SI, and PPS. Thus, less than 5% of Part 27 was 

deemed applicable verbatim to the derived mock certification basis, with only an additional 22% suitable 

for textual modification. 

The evaluation process is subjective by nature. As part of the evaluation process, rationale was 

documented for the disposition of each Part 27 paragraph. The rationale attempts to capture the reasoning 

used to determine the applicability of each Part 27 paragraphs to the unmanned rotorcraft with its 

ConOps. Rationale is not typically included in a type certification basis, but is provided with requests for 

exemptions. Here, the rationale helps shed light on why a paragraph was included, modified, or rolled up, 

in addition to reasons why a paragraph was not recommended for inclusion in the certification basis. The 

Appendix contains the rationale.

4.3. Task 3: Generating UAS-unique Requirements 

Lastly, the primary hazard list was reviewed to identify those hazards for which there are no applicable 

requirements from Part 27. The review identified four primary hazards that are not covered by 

paragraphs in Part 27:

 Loss of containment (i.e., a failure causing a fly away event where the UA leaves the operational 

area)

 Failure to detect and avoid people on the ground

 Failure of safety-critical C2 links

 Failure to detect and avoid other aircraft

The first three hazards are not addressed in any of the FARs, but the last hazard is related to standards for 

aircraft operators. FAR Part §91.113 requires an aircraft operator to use vigilance to see and avoid other 

aircraft. Because there is no onboard operator on a UAS, some systems and equipment will be required to 

accomplish that function. Those systems and that equipment would be subject to airworthiness regulation. 

The third task involved drafting new requirements to address the containment system, systems for 

detecting and avoiding people and other aircraft, and for safety-critical datalinks. New Information Issue 

Papers were proposed for each of those and included in the mock type certification basis. Each of those 

issue papers explains why additional guidance is needed, provides background information explaining the 

hazard, and offers a mock regulatory position with high-level requirements aimed at mitigating the 

hazard. Like the G-1U Issue Paper, each of the new information issue papers is intended to serve as a 

starting point for discussion. None of the issue papers represents official FAA guidance.

The content of the mock type certification basis is given in the next Section.
25

5. Mock Type Certification Basis

Type certification is the foundation for most regulatory approvals related to airworthiness. A type 

certificate is issued when the regulator determines that a product’s design complies with applicable 

regulations. The type design of an aircraft product is the engineering definition of the product, including 

(1) drawings and specifications, (2) dimensions, materials, and processes, (3) airworthiness limitations, 

and (4) other data to describe the product design [28]. The regulating body compares design documents 

and processes to determine if the design meets requirements established for the type of equipment. For 

example, FAR Part 27 contains the standards for normal-category rotorcraft. Once the type certificate is 

issued, the aircraft “type” is considered to meet appropriate requirements. Neither standards nor aircraft 

types have been established yet for UAS.

The FAA recommends starting a certification program with a set of plans to foster teamwork and an 

agreement on how product certification will be conducted. This agreement sets out general 

expectations, operating norms, communications protocols, schedule, and required deliverables [29]. The 

type certification process starts when an applicant submits FAA Form 8110-12 (“Application for Type 

Certificate, Production Certificate, or Supplemental Certificate) to the FAA. A UAS certification project 

in the US would likely start in the same way. 

The FAA uses Issue Papers as a means to formally communicate with an applicant about their 

certification program. The Issue Paper process, as described in FAA Order 8110.112 [15], provides a 

means of tracking certification requirements and issues requiring resolution throughout an aircraft 

certification process. There are several different types of issues papers. The most germane to this study 

are the G-1 Certification Basis Issue Paper and New Information Issue Papers. The G-1 Issue Paper

designates the applicable airworthiness and environmental (i.e., noise, fuel venting and exhaust 

emissions) regulations that constitute a type certification basis. New Information Issue Papers address 

new or novel technology that is not covered or covered adequately in existing regulation. 

The mock type certification basis for the unmanned aerial applicator that follows is formatted like a G-1 

Issue Paper with some minor deviations. The issue paper format was adopted because it is familiar to civil 

aircraft certification specialists and regulatory authorities. The mock type certification basis is labeled 

“G-1U” to indicate that the subject aircraft is unmanned. The G-1U includes a brief description of the 

concept of operations. This is atypical of a G-1 Issue Paper, but serves to provide operational information 

pertinent to airworthiness. Because there are no established airworthiness standards specific to UAS, the 

G-1U calls out requirements from Part 27 that apply in part or in whole to the applicant’s aircraft. Text 

for each requirement can be found in the Appendix of this report. New Information Issue Papers are also 

included in the G-1U. These address the rolled-up requirements for CMS, SI, and PPS, and the UASunique systems described in Sections 4.2 and 4.3.

For this mock certification basis, the Acme-XYZ company is the fictitious name of the applicant for the 

type certificate and developer of the specimen unmanned aerial applicator (the AgR-1). The URA-123 is 

the fictitious name for the regulatory approval authority for the UAS. The content of the mock type 

certification basis does not represent the official position of the FAA or any other certification authority.

As a companion to the mock type certification basis, rationale for decisions made regarding the 

applicability of the Part 27 requirements to the AgR-1 was documented and included in the Appendix. 

The Appendix offers informal reasoning about each Part 27 requirement: why it is included in the mock 

type certification basis, why it is modified, why it is “rolled up”, or why it is excluded. The intent, like 

the intent of the mock type certification basis, is to support debate about potential changes to existing 

regulations. 
26

5.1. G-1U Issue Paper 

Project: Acme-XYZ

Model AgR-1

Project No. TBD

Item: G-1U

Stage: 1

Regulatory Reference: 14 CFR §21.17(b), Designation of Applicable Regulations

Date: TBD

National Policy Reference: FAA Order 8110.4C, Type Certification [28]

FAA AC 27-1B, Certification of Normal Category Rotorcraft [30]

FAA, Integration of Unmanned Aircraft Systems into the National 

Airspace System, Concept of Operations, v2.0 [31]

Issue Status: Open

Subject: Type Certification Basis

Branch Action: URA-123 UAS Certification Branch

Compliance Target: Pre-TC

***

TYPE CERTIFICATION BASIS

Statement of Issue

Acme-XYZ submitted an application (FAA Form 8110-12, dated MMDDYYYY, with cover letter AcmeXYZ-xxx-TBD) for Type Certification of the Acme AgR-1 unmanned rotorcraft. Project Number TBD has

been assigned to the AgR-1 program. The following is the URA-123 position on the certification basis of

the AgR-1 and those associated systems required for dispatch and aerial application operations within a 

defined volume of airspace.

In accordance with Title 14 Code of Federal Regulation (CFR) Part 21 requirements, the certification basis

for the Acme-XYZ Model AgR-1 is established within this document. The certification basis, in addition 

to the applicable Federal Aviation Regulations, may include additional Issue Papers, Special Conditions,

Equivalent Safety Findings, Exemptions, additional design requirements associated with any unsafe

conditions operating requirements, and proposed amendments under review by the URA-123 and industry

groups.

This certification basis is tightly coupled with the AgR-1’s concept of operations for aerial application 

within a defined volume of airspace. In that concept, the UA is restricted to operating within a defined

volume of airspace, referred to herein as a containment volume. No people are allowed within the 

containment volume when the UA is in flight. The pilot and other crew are located close to the 

containment volume, but not within it. 
27

In this context, operational and functional hazards differ from those for manned aircraft. Consequently, 

many of the certification requirements in 14 CFR Part 27 for normal category rotorcraft are inappropriate 

as written for the AgR-1 in its intended operational environment. The requirements under this Type 

Certificate are contained in this Issue Paper, which is heavily based on Part 27. Additional issues and 

requirements, to be addressed under the Type Certificate, have been identified in supplemental issue 

papers for novel or unusual systems.

Background

Acme-XYZ has provided the following description of its unmanned aircraft system and its concept of 

operations.

The AgR-1, depicted below, is an unmanned rotorcraft with the following configuration and characteristics.

 Tandem rotors

 Single turbine powerplant

 Physical envelope of 21 feet by 13 feet by 5.5 feet 

 Maximum gross takeoff weight of approximately 1000 pounds (including max payload weight)

 Maximum endurance of 5 hours with no payload, 2.4 hours with 430-pound (maximum) payload

 Maximum airspeed of 100 knots

 Highly automated primary systems, including operator's ground control station

The concept of operations for the AgR-1 is for precision aerial application of chemicals to treat crops. 

The following operational characteristics are relevant to this type certification.

 The rotorcraft will operate only within a pre-defined containment volume.

 Operations will be conducted over farmland in rural, sparsely populated areas.

 The typical operational area will be 1⁄2 mile by 1⁄2 mile.
28

 Operations will typically be conducted only a few feet over crop height. Operation at more than 400 

ft above ground level is prohibited.

 Operations will occur under visibility conditions including daytime, nighttime, and reduced visibility, 

both within and beyond visual line-of-sight.

 Inner loop control and normal outer loop control is provided by onboard automated systems. The 

remote pilot has final authority and responsibility for operation and safety of flight and can override 

outer loop control provided by the autopilot.

 Operations will recognize that other aircraft and people may enter the containment volume. 

Certification schedule

Month Year [ed. note: nominally, application date + three years]

URA-123 Position (Stage 1)

As the applicant, Acme-XYZ is responsible for meeting all regulatory requirements contained in this 

Issue paper. 

Applicable FARs

The following list includes those regulations from Part 27, by number and title, that apply to the Acme 

AgR-1. Some of those regulations have been modified as noted 7to address unique aspects of the AgR-1

with respect to its intended operation. 

Subpart B—Flight

General 

§27.21 Proof of compliance -modified

§27.241 Ground resonance

Subpart C—Strength Requirements

Control Surface and System Loads

§27.411 Ground clearance: tail rotor guard -modified

§27.427 Unsymmetrical loads -modified

Subpart D—Design and Construction

General

§27.601 Design -modified

§27.602 Critical Parts -modified

§27.603 Materials

§27.609 Protection of structure -modified

§27.610 Lightning and static electricity protection -modified

§27.611 Inspection provisions -modified

§27.629 Flutter 

Control Systems

§27.691 Autorotation control mechanism -modified

Fire Protection

§27.861 Fire protection of structure, controls, and other parts -modified

§27.863 Flammable fluid fire protection -modified

 

7 The wording of proposed modifications to the requirements would be included in a type certification basis. To avoid 

replication in this document, the text and modifications are shown in the Appendix.
29

Subpart E—Powerplant

General

§27.903 Engines -modified

§27.907 Engine vibration -modified

Rotor Drive System

§27.917 Design -modified

§27.921 Rotor brake

§27.931 Shafting critical speed

§27.935 Shafting joints

§27.939 Turbine engine operating characteristics -modified

Fuel System

§27.969 Fuel tank expansion space

§27.973 Fuel tank filler connection -modified

§27.975 Fuel tank vents -modified

Oil System

§27.1027 Transmission and gearboxes -modified

Subpart F—Equipment

General

§27.1301 Function and installation -modified

§27.1303 Flight and navigation instruments -modified

§27.1305 Powerplant limitations -modified

§27.1307 Miscellaneous equipment -modified

§27.1309 Equipment, systems, and installations -modified

§27.1317 High-intensity Radiated Fields (HIRF) Protection -modified

Instruments: Installation 

§27.1321 Arrangement and visibility -modified

§27.1322 Warning, caution, and advisory lights -modified

§27.1325 Static pressure systems -modified

§27.1329 Automatic pilot system -modified

Electrical Systems and Equipment

§27.1351 General -modified

§27.1353 Storage battery design and installation -modified

§27.1357 Circuit protective devices -modified

§27.1361 Master switch -modified

§27.1365 Electric cables -modified

§27.1367 Switches -modified

Lights 

§27.1381 Instrument lights -modified

§27.1383 Landing lights -modified

§27.1397 Color specifications

§27.1401 Anticollision light system -modified

Safety Equipment

§27.1411 General -modified

§27.1459 Flight data recorders -modified

§27.1461 Equipment containing high energy rotors -modified

Subpart G—Operating Limitations and Information

§27.1501 General -modified
30

Operating Limitations

§27.1523 Minimum flight crew -modified

§27.1525 Kinds of operations -modified

§27.1527 Maximum operating altitude -modified

§27.1529 Instructions for Continued Airworthiness - modified

Markings and Placards

§27.1541 General –modified

§27.1555 Control markings -modified

§27.1557 Miscellaneous markings and placards -modified

§27.1559 Limitations placard -modified

§27.1561 Safety equipment -modified

§27.1565 Tail rotor

Rotorcraft Flight Manual and Approved Manual Material

§27.1581 General -modified

§27.1583 Operating limitations -modified

§27.1585 Operating procedures -modified

Appendix A—Instructions for Continued Airworthiness

A§27.1 General -modified

A§27.2 Format

A§27.3 Content -modified

A§27.4 Airworthiness Limitations section

Appendix D—HIRF Environments and Equipment HIRF Test Levels -modified

Fuel Venting and Exhaust Emission Requirements for Turbine Powered Aircraft [reworked Part 34, 

through Amendment TBD, as appropriate]

Noise Standards: Aircraft Type and Airworthiness Certification [reworked Part 36, through Amendment

TBD, as appropriate (see also Title 49, USC, Section 44715, “Noise Control Act of 1972”)]

Issue Papers

The following issue papers apply to the AgR-1 type certification:

Issue Paper U-1 Controllability, Maneuverability, and Stability

Issue Paper U-2 Structural Integrity

Issue Paper U-3 Powerplant and Supporting Systems

Issue Paper U-4 Containment

Issue Paper U-5 Detect and Avoid Intruder Aircraft

Issue Paper U-6 Detect and Avoid Persons and Objects within the Containment Area

Issue Paper U-7 Safety-critical Command and Control Datalinks

Special Conditions

Special Conditions will be issued as appropriate in accordance with 14 CFR Part 21, Section 21.16. 

Equivalent Safety Findings

Equivalent Safety Findings (ESFs) will be administered in accordance with 14 CFR Part 21, Section 21.21.

The URA-123 expects Acme-XYZ to submit a request and justification for each proposed ESF after more

detailed design discussions with the URA-123 have taken place. If ESFs are submitted, the URA-123 will

generate subsequent Issue Papers documenting agency findings.
31

Exemptions

Acme-XYZ may petition the URA-123 to grant relief from current regulatory requirements. Petitions are

to be submitted in accordance with 14 CFR Part 11, Sections 11.61 through 11.101.

Voluntary regulatory compliance

Acme-XYZ may request that additional or optional design requirements be included in the AgR-1

certification basis.

Additional Design Requirements and Conditions

Compliance with the established basis for Type Certification notwithstanding, 14 CFR 21.21(b)(2) 

precludes issuance of Type Certificate if any feature or characteristic of the product would make the

product unsafe. Should the URA-123 determine that such an unsafe feature or characteristic exists, 

approval of the Type Certificate will be withheld pending acceptable corrective action by the applicant. 

Unsafe features or characteristics will be identified and resolved using Issue Papers. The requirements or

conditions used to address unsafe features will be identified in the Type Certificate Data Sheet in a section

immediately following specification of the certification basis.

Operating Certificate Requirements

From time to time, amendments to the operating rules of 14 CFR can specify retroactive compliance under

the relevant airworthiness requirements. Compliance with such amendments is mandatory for operation

under the applicable operating rules. If not already included in the above certification basis, any such

applicable airworthiness requirement may be added to the Type Certification Basis of the AgR-1 by

mutual agreement between Acme-XYZ and the URA-123. The applicant should note, however, that

compliance with any such retroactive mandate can affect the AgR-1 operator regardless of the contents of

this G-1U Issue Paper.

Changes to the certification basis

It is the URA-123's intent to define the AgR-1 certification basis by closing this G-1U Issue Paper early in 

the certification program. Any changes to the certification basis due to addition of new Special

Conditions, Equivalent Safety Findings, Exemptions, or additional design requirements will be

coordinated with Acme-XYZ by Issue Paper and added to the G-1U Issue Paper before issuance of the

Type Certificate. The final certification basis will be summarized in the conclusion of this Issue Paper.

Acme-XYZ Position (Stage 1)

TBD
32

5.1.1. U-1 Issue Paper: Controllability, Maneuverability, and Stability

Project: Acme-XYZ

 Model AgR-1

 Project No. TBD

Item: Issue Paper U-1 

Stage: 1

Date: TBD

Regulatory Reference: 14 CFR §21.17(b), Designation of Applicable Regulations

National Policy Reference: FAA Order 8110.4C, Type Certification [28]

FAA AC 27-1B, Certification of Normal Category Rotorcraft [30]

Issue Status: Open

Subject: Controllability, Maneuverability, and Stability

Date: TBD

Branch Action: URA-123 UAS Certification Branch

Compliance Target: Pre-TC

Type of Issue Paper New Information

***

Statement of Issue 

Existing certification requirements in 14 CFR Part 27 for controllability, maneuverability, and stability 

(CMS) of a rotorcraft are inappropriate as written for the AgR-1 in its intended operational environment. 

Modifications to Part 27 are necessary to ensure the requirements related to CMS are appropriate for the 

AgR-1 and its operation under this Type Certificate.

Background

Part 27 is concerned with protection of flight crew and passengers. Conventional airworthiness 

requirements generally relate to such protection, though many requirements relate to protection indirectly. 

For example, traditional focus on vehicle damage and hull loss is invariably a proxy for underlying 

concern with the safety of all occupants aboard an aircraft. The hazards associated with operation of an 

unmanned aerial applicator, however, differ greatly from those addressed by Part 27. In particular, the 

possibility of injury to or death of bystanders from high-energy debris becomes a key concern. 

Several failure conditions can result in high-energy debris. This Issue Paper addresses one family of 

those conditions: inadequate controllability and maneuverability of the UA in circumstances that can lead 

to rotor, hub, or drive system damage and subsequent release of high-energy debris (e.g., rotor blades) 

near humans.

The Type Design must incorporate provisions, design features, and characteristics that reduce to 

acceptable levels the risks associated with, for example, (a) loss of control during takeoff, leading to 
33

vehicle rollover and destruction of the main rotors near ground personnel, or (b) loss of control during 

hover near the containment boundary, leading to uncontrolled descent into terrain near UAS observers or 

even unrelated bystanders outside the containment zone.

URA-123 Position (Stage 1)

As the applicant, Acme-XYZ is responsible for meeting all regulatory requirements, both existing 

requirements and those requirements unique to AgR-1 Type Certification, as agreed to between the URA123 and the applicant. Acme-XYZ must address the concerns expressed in this Issue Paper as they 

pertain to the specified vehicle characteristics.

The applicant must meet the regulatory intent of requirements related to controllability, stability, 

maneuverability, and control system design and installation, notably those requirements embodied in 14 

CFR Part 27, Subparts B and C indicated in Notes 1 and 2. The URA-123 recognizes that tradeoffs exist 

between operational mitigations and traditional handling of functional capabilities, integrity, and design 

assurance, and that improvements in one area can compensate for deficiencies in the other. The URA-123

encourages the applicant to clarify and to make explicit such tradeoffs in its proposed type design.

The applicant must:

(a) establish controllability and maneuverability design margins that prevent (i) contact of the vehicle 

rotors with the ground, other parts of the vehicle structure, or obstacles in normal and non-normal 

operations and (ii) any other condition that could compromise rotor system integrity. The applicant must

demonstrate that the proposed control system design and installation meets or exceeds these requirements. 

Considerations include but are not limited to the following:

 critical values of design parameters including weight, center of gravity, rotor speed, speed, density 

altitude, and height-speed envelope,

 normal operations such as takeoff, landing, and spraying and critical values of operational parameters 

such as winds, slopes, etc. for which operational approval is sought, and 

 non-normal operations such as autorotation and contingency maneuvers.

Note 1: The following requirements from Part 27 are relevant to (a): §27.25, §27.27, §27.33, §27.51, §27.75, 

§27.87, §27.141, §27.143, §27.151, §27.173, §27.175, §27.177, §27.231, §27.321, §27.337, §27.672, §27.1151(a) 

only, §27.1519, §27.1583, §27.1587, and §27.1589.

(b) ensure that flight control commands from all sources (stability augmentation system, autopilot, GCS, 

etc.) are passed to the appropriate flight control surfaces without hazardous flexure, slop, friction, 

jamming, interference or other hazards that would lead to loss of rotor system integrity. This requirement 

must cover all normal and non-normal operational conditions that may reasonably be expected in service. 

This requirement includes the electrical and mechanical aspects of the control system, and includes 

control of engines, rotor brakes, and other elements of the design that involve automated or remote 

operation of the vehicle controls.

Note 2: The following requirements from Part 27 are relevant to (b): §27.307, §27.309, §27.391, §27.395, §27.605, 

§27.607, §27.621, §27.623, §27.625, §27.671, §27.675, §27.679, §27.681, §27.683, §27.685, §27.687, and §27.695.

Acme-XYZ Position (Stage 1):

TBD 
34

5.1.2. U-2 Issue Paper: Structural Integrity

Project: Acme-XYZ

 Model AgR-1

 Project No. TBD

Item: Issue Paper U-2 

Stage: 1

Date: TBD

Regulatory Reference: 14 CFR §21.17(b), Designation of Applicable Regulations

National Policy Reference: FAA Order 8110.4C, Type Certification [28]

FAA AC 27-1B, Certification of Normal Category Rotorcraft [30]

Issue Status: Open

Subject: Structural Integrity

Date: TBD

Branch Action: URA-123 UAS Certification Branch

Compliance Target: Pre-TC

Type of Issue Paper New Information

***

Statement of Issue 

Existing certification requirements in 14 CFR Part 27 for structural integrity of rotor and hub assemblies, 

supporting structure, and drive systems are inappropriate as written for the AgR-1 in its intended 

operational environment. Modifications to relevant paragraphs of Part 27 are necessary to ensure the 

requirements related to structural integrity are appropriate for the AgR-1 rotor, hub, and drive systems.

Background

Part 27 is concerned with protection of flight crew and passengers. Conventional airworthiness 

requirements generally relate to such protection, though many requirements relate to protection indirectly. 

For example, traditional focus on vehicle damage and hull loss is invariably a proxy for underlying 

concern with the safety of all occupants aboard an aircraft.

The hazards associated with operation of an unmanned aerial applicator, however, differ in many respects

from those addressed by Part 27. In particular, the possibility of injury to or death of crew or bystanders 

from high-energy debris becomes a key concern. 

Several failure conditions can result in high-energy debris. This Issue Paper addresses one family of 

those conditions: inadequate structural integrity of the UA’s rotor system in circumstances that can lead to 

rotor, hub, or drive system failure and subsequent release of high-energy debris near humans.
35

URA-123 Position (Stage 1)

As the applicant, Acme-XYZ is responsible for meeting all regulatory requirements, both existing 

requirements and those requirements unique to AgR-1 Type Certification, as agreed to between the URA123 and the applicant. Acme-XYZ must address the concerns expressed in this Issue Paper as they 

pertain to the specified vehicle characteristics.

The applicant must meet the regulatory intent of structural requirements, notably those requirements 

embodied in 14 CFR Part 27, Subpart C (see Note). The URA-123 recognizes that tradeoffs exist 

between operational mitigations and traditional structural requirements, and that improvements in one 

area can compensate for deficiencies in the other. The URA-123 encourages the applicant to clarify and 

to make explicit such tradeoffs, if included, in its proposed type design.

The Type Design must incorporate provisions, design features, and characteristics that provide acceptable 

levels of protection against rotor, hub, and drive system failures. 

The applicant must establish design margins and limitations of the structure of the rotor, hub, and drive

systems to prevent loss of rotor system integrity (including primary load paths affecting the rotor system). 

The design margins and limitations should cover all conditions likely to be encountered in normal and 

non-normal operations. Considerations include but are not limited to static analysis, dynamic analysis, 

and fatigue analysis and testing at critical conditions of weight, center of gravity, engine/rotor speed, 

engine/rotor torque, ground resonance, and sudden stoppage of rotor and hub assemblies due to internal 

failure or seizure of internal components.

Note: The following requirements are relevant: §27.25, §27.27, §27.33, §27.51, §27.75, §27.141, §27.251, §27.307, 

§27.309, §27.321, §27.337, §27.391, §27.547, §27.549, §27.571, §27.605, 27.607, §27.621, §27.623, §27.625, 

§27.653, §27.659, §27.661, §27.663, §27.681, §27.1151 (a only), §27.1193, §27.1509, and §27.1583.

Acme-XYZ Position (Stage 1)

TBD 
36

5.1.3. U-3 Issue Paper: Powerplant and Supporting Systems

Project: Acme-XYZ

 Model AgR-1

 Project No. TBD

Item: Issue Paper U-3

Stage: 1

Date: TBD

Regulatory Reference: 14 CFR §21.17(b), Designation of Applicable Regulations

National Policy Reference: FAA Order 8110.4C, Type Certification [28]

FAA AC 27-1B, Certification of Normal Category Rotorcraft [30]

Issue Status: Open

Subject: Powerplant and Supporting Systems

Date: TBD

Branch Action: URA-123 UAS Certification Branch

Compliance Target: Pre-TC

Type of Issue Paper New Information

***

Statement of Issue

Existing certification requirements in 14 CFR Part 27 for the powerplant and supporting systems (e.g., 

fuel, oil, cooling, exhaust, and induction systems) of a rotorcraft are overly prescriptive for the AgR-1 in 

its intended operational environment. Modifications to Part 27 are necessary to ensure the requirements 

related to the powerplant and supporting systems are appropriate for the AgR-1 under this Type 

Certificate.

Background

Part 27 requires high levels of powerplant reliability in order to protect occupants of the rotorcraft. By 

contrast, hull loss of an AgR-1 operating in accordance with approved operations has no safety effect. 

Thus, correspondingly lower reliability of the powerplant and its associated systems and the absence of an 

autorotation capability are generally acceptable under this type certificate. As such, many of the Part 27 

requirements for the powerplant and supporting systems are not applicable to the AgR-1.

Lower levels of powerplant reliability, however, could expose the ground crew or the general public to 

harm. For example, flying debris might escape the containment area if a powerplant failure or seizure 

causes loss of rotor system integrity near a containment boundary. 14 CFR §27.917 requires the 

incorporation of a unit (e.g., a clutch) to automatically disengage the engine from the main and auxiliary 

rotors if the engine fails. The purpose of this requirement is to protect the rotor drive system, which 

includes any part necessary to transmit power from the engine to the rotor hubs including “gear boxes, 
37

shafting, universal joints, couplings, rotor brake assemblies, clutches, supporting bearings for shafting, 

attendant accessory pads or drives, and any cooling fans that are part of, or attached to, or mounted on the 

rotor drive system.” This Issue Paper assumes the inclusion of this requirement in the Type Certification 

Basis for the AgR-1, and addresses additional requirements on the powerplant and supporting systems 

necessary to preserve rotor system integrity.

URA-123 Position (Stage 1):

As the applicant, Acme-XYZ is responsible for meeting all regulatory requirements, both existing 

requirements and those requirements unique to AgR-1 Type Certification, as agreed to between the URA123 and the applicant. Acme-XYZ must also address the concerns expressed in this Issue Paper as they 

pertain to the specified vehicle characteristics.

The Type Certification Basis for the AgR-1 must include 14 CFR §27.917 requiring a device that 

prevents engine failure or seizure from adversely affecting rotor system integrity. The applicant must also 

meet the regulatory intent of powerplant and supporting systems requirements, notably those 

requirements embodied in 14 CFR Part 27, Subpart E (see Note). The URA-123 recognizes that tradeoffs

exist between operational mitigations and traditional handling of functional capabilities, integrity, and 

design assurance, and that improvements in one area can compensate for deficiencies in the other. The 

URA-123 encourages the applicant to clarify and to make explicit such tradeoffs in its proposed type 

design.

For the rotorcraft powerplant, powerplant installation, and associated systems (e.g., fuel, oil, ventilation, 

exhaust, and air induction systems), including relevant elements of the ground support equipment, the 

applicant:

(a) must provide adequate protection to the ground crew during servicing and inspection of the rotorcraft 

for preflight, postflight, and thru-flight servicing, 

(b) may include credit for ground crew safety equipment, training, and operational procedures, and

(c) may not include credit for ground-based protective barriers that only protect the crew.

Note: The following requirements are relevant: §27.963, §27.993, §27.995, §27.1121, §27.1183, §27.1185, 

§27.1187, §27.1189, §27.1191, §27.1193, §27.1521, and §27.1583.

Acme-XYZ Position (Stage 1):

TBD 
38

5.1.4. U-4 Issue Paper: Containment

Project: Acme-XYZ

 Model AgR-1

 Project No. TBD

Item: Issue Paper U-4

Stage: 1

Date: TBD

Regulatory Reference: 14 CFR §21.16, Special Conditions

National Policy Reference: FAA Order 8110.4C, Type Certification [28]

Issue Status: Open

Subject: Containment 

Date: TBD

Branch Action: URA-123 UAS Certification Branch

Compliance Target: Pre-TC

Type of Issue Paper New Information

***

Statement of Issue

The concept of operations for the Acme AgR-1 is based on the provision of a geospatial containment 

function to confine operations to a defined volume of airspace. Geospatial containment systems are not 

addressed by existing regulation. New requirements are needed.

Background

The applicant has proposed a high-confidence geospatial containment function (that is, a means of 

ensuring that UA operations are confined within defined geospatial boundaries) to address hazards to 

other airspace users and people on the ground, especially in a loss of control event. For manned aircraft, 

highly reliable systems, equipment, and crew are relied upon to mitigate those hazards. Avionics systems 

for many unmanned aircraft do not meet the same levels of reliability or integrity. Consequently, 

alternative approaches to hazard mitigation might be needed to provide an acceptable level of safety. 

When combined with systems and procedures for ensuring that the containment volume remains clear of 

all persons, this approach is expected to provide sufficient mitigation of catastrophic hazards.

Availability and integrity requirements for normal category rotorcraft systems and equipment are 

specified in 14 CFR §27.1309. Paragraphs (a) and (c) of this regulation state: “(a) The equipment, 

systems, and installations whose functioning is required by this subchapter must be designed and installed 

to ensure that they perform their intended functions under any foreseeable operating condition” and “(c) 

The equipment, systems, and installations of single-engine rotorcraft must be designed to minimize 

hazards to the rotorcraft in the event of a probable malfunction or failure.”
39

Commercially available avionics systems that satisfy those requirements do not typically meet the size, 

weight, volume, and power limitations of the AgR-1 design. Consequently, the reliability level of systems 

and equipment on board the AgR-1 might not be sufficient to mitigate hazards, especially those associated 

with a fly-away event, without the addition and proper functioning of an independent, high-confidence

containment system. 

The following definitions relevant to containment apply:

 The containment area is a geographic area over which all UAS flight operations will be conducted.

 The containment boundary is a virtual surface defined around the containment area. The containment 

boundary is defined by the horizontal dimensions of the containment area and by a vertical height. 

Depending on system implementation, this boundary could be a simple geometric shape (e.g., 

cylinder or dome) or a complex multipoint closed surface.

 The containment volume is the volume of airspace enclosed by the boundary.

 The containment system is some combination of people, systems, and equipment used to confine the 

operation of a UA to a defined geospatial area.

Geofencing is a proposed means of confining the operation of a UAS to a defined area. Geofences are 

primarily implemented via software and the UA’s autopilot, using the same sensors, actuators and 

processor as the vehicle’s primary autopilot/control system. Such geofences generally suffer from 

multiple single points of failure, including the autopilot and global positioning system (GPS), making it 

difficult to achieve levels of reliability and design assurance adequate to meet typical airworthiness 

standards. 

URA-123 Position (Stage 1)

The URA-123 recognizes that the applicant may, in order to prevent fly-away events, make trade-offs 

among procedures, operational limitations, and the functional capabilities of systems and equipment. The 

applicant must provide a containment system that addresses hazards associated with fly-away events. 

Any containment system must have the ability to detect impending violations of any containment 

boundary and take timely action to ensure the boundary is not crossed. 

The applicant must provide a means to detect and avoid transgression of any containment boundaries 

established for the operation. This includes the following considerations:

(a) The accuracy of the UAS’s estimation of the UA’s position relative to the containment boundaries 

must be sufficient to ensure that the aircraft will not exit a containment boundary.

(b) Situational awareness of the UA’s location relative to the containment boundaries should be 

maintained at all times during all flight operations.

(c) Failure of infrastructure not part of the UAS (e.g., GPS, cellular telephone) must not significantly 

interfere with the determination of the location of the aircraft.

(d) Means of detection should:

(1) have complete and unobstructed surveillance of any established containment boundaries, at all 

times during all flight operations in all weather conditions (e.g., lighting and visibility conditions) 

for which operations are approved; and

(2) be able to determine impending violations of any established boundary, in sufficient time for 

action to avoid crossing the boundary.

(e) If action by the pilot in command is required to ensure the UA does not cross any established 

containment boundary, quick acting means must be provided to alert the pilot in command.
40

(1) Timing thresholds for alerts should consider the time needed (i) to transmit data via radios or 

other means of communication, (ii) for ground control station processing and annunciation, and 

(iii) for human response, as relevant.

(f) Means of avoidance must be sufficient to ensure the UA remains within the established containment 

boundaries at all times.

(1) Latency and availability of any command and control datalink or other communication links 

required for avoidance should be considered in establishing timing thresholds for avoidance 

maneuvers and shown to be acceptable for ensuring an avoidance maneuver can be executed to 

maintain containment.

(2) Activation of an avoidance maneuver from on board the UA must be communicated to the pilot in 

command in a timely manner.

(3) Confirmation of the completion of any avoidance maneuver must be communicated to the pilot in 

command in a timely manner. 

(g) The containment system design must consider events wherein release of high energy parts may 

constitute a hazard to bystanders outside the containment area.

(h) The performance of the containment system must not be degraded by any form of interference under 

any foreseeable operating condition. Considerations should include, but are not limited to:

(1) electromagnetic interference caused by any other UA systems,

(2) electromagnetic interference external to the UA, and

(3) interference via acoustic, thermal, vibrational, chemical, or metallurgical means.

Acme-XYZ Position (Stage 1)

TBD 
41

5.1.5. U-5 Issue Paper: Detect and Avoid Intruder Aircraft

Project: Acme-XYZ

 Model AgR-1

 Project No. TBD

Item: Issue Paper U-5

Stage: 1

Date: TBD

Regulatory Reference: 14 CFR §21.16, Special Conditions 

National Policy Reference: FAA Order 8110.4C, Type Certification [28]

Issue Status: Open

Subject: Detect and Avoid Intruder Aircraft 

Date: TBD

Branch Action: URA-123 UAS Certification Branch

Compliance Target: Pre-TC

Type of Issue Paper New Information

***

Statement of Issue

The AgR-1 must comply with the intent of 14 CFR Part §91.111(a), Operating Near Other Aircraft, and 

Part §91.113(b), Right-of-way Rules. Because there is no pilot on board the AgR-1 who can see and 

avoid other aircraft, additional systems, equipment, and procedures may be required to detect and avoid 

other aircraft that might enter the containment volume or come within close proximity to the AgR-1. An 

intruder aircraft detection and avoidance system is not addressed by existing regulation. New 

requirements are needed.

Background

14 CFR Part §91.111 (a) states that no person may operate an aircraft so close to another aircraft as to 

create a collision hazard and Part §91.113(b) states that vigilance shall be maintained by each person 

operating an aircraft so as to see and avoid other aircraft. 

For manned aircraft, the pilotwith the assistance of systems such as air traffic control (ATC) and the 

Traffic Collision Avoidance System (TCAS)is relied upon to keep the aircraft well clear of other 

aircraft. For unmanned aircraft, no equivalently safe and cost-effective civil airborne system exists at this 

time. The applicant has thus proposed a ground-based intruder aircraft detection and avoidance system to 

address hazards to other airspace users. To provide a cost-effective solution, this ground-based detect and 

avoid system might not provide the full functionality of human see and avoid. To compensate for this 

inadequacy, larger safety margins for the detect and avoid function should be provided. Requirements 
42

appropriate for this alternative approach to avoiding other aircraft are needed to provide an acceptable 

level of safety. 

URA-123 Position (Stage 1)

The URA-123 recognizes that the applicant may, in order to ensure separation, make trade-offs among 

procedures, operational limitations, and the functional capabilities of systems and equipment. The 

applicant must provide a system that addresses hazards associated with loss of separation. Any such 

system must have the ability to detect imminent intrusion or close proximity and take timely action to 

ensure separation is not lost. 

The applicant should provide a means to detect and avoid other aircraft that may intrude on the 

containment volume or otherwise pose a threat to loss of separation. All other airborne vehicles, including 

other UA, should be given priority. The AgR-1 is responsible for remaining well clear of all other aircraft. 

(a) Means of detecting other aircraft will: 

(1) be able to detect other airborne vehicles at a sufficient range from the containment area to allow 

time for an avoidance maneuver,

(2) have complete and unobstructed coverage of the containment area, and

(3) be active at all times during all flight operations in all weather, lighting, and visibility conditions 

for which operations are approved.

(b) If action by the pilot in command is required to avoid loss of separation with an airborne vehicle, 

quick acting means must be provided to alert the pilot in command.

(1) Timing thresholds for alerts should consider the time needed (i) to transmit data via radios or 

other means of communication, (ii) for ground control station processing and annunciation, and 

(iii) for human response, as relevant. 

(c) Means of avoidance must be sufficient to ensure the UA maintains sufficient separation from other 

aircraft at all times. 

(1) Latency and availability of any command and control datalink or other communication links 

required for avoidance should be considered in establishing timing thresholds for avoidance 

maneuvers and shown to be acceptable for ensuring an avoidance maneuver can be executed to 

maintain separation.

(2) The avoidance maneuver must maintain separation throughout its execution duration.

(3) Confirmation of any avoidance maneuver must be communicated to the pilot in command.

(4) Clearance distances from containment boundaries should be established and maintained for 

avoidance maneuvers to ensure that no harm is done to persons on the ground.

(5) Operations may only resume when the UA is well clear of all other aircraft. 

(d) The performance of the aircraft detection and avoidance system must not be degraded by any form of 

interference under any foreseeable operating conditions. Considerations include, but are not limited 

to:

(1) electromagnetic interference caused by any other UA systems,

(2) electromagnetic interference external to the UA, and 

(3) interference via acoustic, thermal, vibrational, chemical or metallurgical means.

Acme-XYZ Position (Stage 1)

TBD 
43

5.1.6. U-6 Issue Paper: Detect and Avoid Persons and Objects within the Containment Area

Project: Acme-XYZ

 Model AgR-1

 Project No. TBD

Item: Issue Paper U-6

Stage: 1

Date: TBD

Regulatory Reference: 14 CFR §21.16, Special Conditions

National Policy Reference: FAA Order 8110.4C, Type Certification [28]

Issue Status: Open

Subject: Detect and Avoid Persons and Objects within the Containment Area

Date: TBD

Branch Action: URA-123 UAS Certification Branch

Compliance Target: Pre-TC

Type of Issue Paper New Information

***

Statement of Issue

Although operational procedures are required to clear the containment area prior to flight operations, a 

system for detecting and avoiding people or obstacles within the containment area or that might enter the 

containment area during flight operations is required to avoid injuring persons or causing an impact that 

releases high energy part that could harm others. However, such a system is not addressed by existing 

regulation. New requirements are needed.

Background

Low-altitude flight such as that expected with aerial application operations poses hazards to people who 

might inadvertently enter the containment area defined for those operations. A low-altitude flight path 

might also encounter objects such as livestock or tractors that have been left in the field that could cause 

damage and potential release of high energy parts if struck with a rotorcraft. Because there is no pilot on 

board the AgR-1 who can see and avoid these obstacles, additional operational procedures, systems, and 

equipment not covered in Part 27 are required to monitor the containment area for people and obstacles

and ensure that the AgR-1 does not collide with them.

Static obstacles (e.g., barns or silos) are mapped in advanced and loaded into a database a priori to 

operations for the purpose of path planning. Trajectories that are flown by the UA are designed to avoid 

these static obstacles. The proposed system can compensate for accuracy errors in the static object database 

or in path-following logic. Other obstacles such as mobile irrigation equipment may not be identified in 

static obstacle databases. Collision with sizable obstacles could cause release of high energy parts that 
44

could pose harm to people beyond the containment zone. Unanticipated ground objects that have the 

potential to damage the rotor system of the AgR-1 on impact should be detected and avoided. 

Dynamic objects (e.g., people wandering into the containment area, ground vehicles, livestock, or wildlife) 

cannot be planned for and must be avoided as they are detected.

URA-123 Position (Stage 1)

The URA-123 recognizes that the applicant may, in order to prevent collisions with people or obstacles 

within the containment area, make trade-offs among procedures, operational limitations, and the 

functional capabilities of systems and equipment.

The applicant must provide an appropriate detection and avoidance system that addresses hazards 

associated with harming any third parties resulting from colliding with objects within the containment 

area. Any such system must have the ability to detect persons or objects within the containment area and 

take timely action to ensure the UA does not collide with them or come within sufficient proximity to 

cause harm.

The applicant must provide a means to detect and avoid persons and objects within the defined 

operational area during flight operations.

(a) Means of detection will: 

(1) have sufficient range in the direction of UA travel to permit a simple avoidance maneuver (e.g., 

hovering or landing), and

(2) provide detection during all flight operations in all weather, lighting, and visibility conditions for 

which operations are approved.

(b) If action by the pilot in command is required to avoid collision or remain a safe distance from persons 

or objects to prevent harm, quick acting means will be provided to alert the pilot in command.

(1) Timing thresholds for alerts should consider the time needed (i) to transmit data via radios or 

other means of communication, (ii) for ground control station processing and annunciation, and 

(iii) for human response, as relevant.

(c) Means to suspend operation or provide an otherwise safe state shall be provided.

(1) Latency and availability of any command and control datalink or other communication links 

required for avoidance should be considered in establishing timing thresholds for avoidance 

maneuvers and shown to be acceptable.

(2) Minimum clearances should be established.

(3) Confirmation of any avoidance maneuver should be communicated to the pilot in command in a 

timely manner.

(4) Operations may only resume when the operational area has been cleared.

(d) The performance of the detection and avoidance system must not be degraded by any form of 

interference under any foreseeable operating conditions. Considerations include, but are not limited 

to:

(1) electromagnetic interference caused by any other UA systems,

(2) electromagnetic interference external to the UA, and 

(3) interference via acoustic, thermal, vibrational, chemical or metallurgical means.

Acme-XYZ Position (Stage 1)

TBD
45

5.1.7. U-7 Issue Paper: Safety-critical Command and Control Datalinks

Project: Acme-XYZ

 Model AgR-1

 Project No. TBD

Item: Issue Paper U-7

Stage: 1

Date: TBD

Regulatory Reference: 14 CFR §21.16, Special Conditions

National Policy Reference: FAA Order 8110.4C, Type Certification [28]

Issue Status: Open

Subject: Safety-critical Command and Control Datalinks 

Date: TBD

Branch Action: URA-123 UAS Certification Branch

Compliance Target: Pre-TC

Type of Issue Paper New Information

***

Statement of Issue

Airworthiness of the UAS will be dependent on the quality of the command and control (C2) links. The 

quality of the C2 links is strongly influenced by the operational coverage and the various quality-ofservice parameters of the communication media used. C2 link communications are necessary for a 

remote pilot to command the UA, especially to execute a safety role (e.g., by commanding safety-related 

maneuvers). A safety-critical C2 link is defined as a link which passes commands relevant to safetycritical functions. Currently, safety-critical C2 links are not addressed by existing regulation. New 

requirements are needed.

Background

Within the US, telecommunications services for the purposes of ATC are operated by the FAA. This will 

likely not be the case for UAS operations. Telecommunications services might be furnished by a broad 

variety of service providers. The frequency asset being used might be shared among radio 

communication providers over the operational area and might not be protected against interference (i.e., it 

might not be an aeronautical safety allocation). 

Only UAS with remote pilots are currently eligible for certification consideration. Because C2 links are 

not standard equipment for manned aircraft, Part 27 does not include requirements for them. A UAS 

might include any number of datalinks, but not all datalinks have safety significance. This issue paper 

addresses only those datalinks that have a safety-critical role. As an aircraft’s airworthiness can be rated 

with different capabilities based on the certification of the various components (e.g., for extended oceanic 

operations), it is conceivable that this might hold true with respect to the various types and 
46

implementations of safety-critical C2 links. The URA-123 position is predicated on the following 

assumptions:

 There is a unique pairing between the ground control station and the aerial vehicle. That is, each 

vehicle is controlled by one unique ground control station (no handoffs between ground control 

stations, or simultaneous control over multiple ground control stations), and each ground control 

station only controls one unique vehicle (no control of multiple vehicles by a single ground control 

station or operator).

 The UA is within radio line-of-sight (RLOS) of the ground control station at all times during the 

operation, thus requiring no signal relays or repeaters.

URA-123 Position (Stage 1)

The applicant must include at least one safety-critical C2 link in the design of the AgR-1 for use by the 

pilot to command the UA to a safe state and for providing safety-critical data from the UA to the pilot. 

Any datalink referred to below is assumed to be safety-critical.

(a) The C2 link shall:

(1) be available in all vehicle attitudes under all foreseeable operating conditions throughout the 

containment volume, and 

(2) enable radio line-of-sight communication for safety-critical data at all points throughout the entire 

containment volume. 

(b) Uplink and downlink status shall be indicated to the pilot during all flight operations.

(c) The uplink(s) used to communicate the pilot commands to the UA will: 

(1) adhere to appropriate standards8 of integrity, availability, continuity, reliability, and security;

(2) cause operations to cease if thresholds for latency or for error rates are not met; and

(3) be active at all times during all flight operations, including during all weather, lighting, and 

visibility conditions for which operations are approved.

(d) The downlink(s) used to communicate safety-critical vehicle information to the pilot in command 

will: 

(1) adhere to standards of integrity, availability, continuity, reliability, and security;

(2) meet established standards for error rates; and 

(3) be capable of communicating data from the UA at all times during all flight operations in all 

weather, lighting, and visibility conditions for which operations are approved.

(e) The performance of the C2 link (e.g., availability and quality of service) must not be degraded by any 

form of interference under any foreseeable operating conditions. Considerations include, but are not 

limited to:

(1) electromagnetic interference caused by any other UA system,

(2) electromagnetic interference external to the UA,

(3) ionospheric, atmospheric, or rain attenuation,

(4) malicious interference/spoofing or link takeover,

 

8

Specification of standards for integrity, availability, continuity, reliability, and security are beyond the scope of this effort. 

Such standards may be developed by the FAA or standards groups such as the RTCA.
47

(5) frequency access scheme, link budget, bandwidth characteristics and frequency assignment 

planning criteria of the C2 link,

(6) adjacent or shared frequencies, and 

(7) interference related to shared resources (e.g., power).

Acme-XYZ Position (Stage 1)

TBD 
48

6. Potential Systems and Equipment Implementation

The ConOps and mock type certification basis are useful only if UAS technology exists that can meet the 

objectives of the ConOps and can comply with the proposed design and performance standards. This 

section describes one possible UAS configuration that could meet those requirements. The example 

configuration is based in large part on Dragonfly Pictures’ DP-14 model unmanned rotorcraft. This 

example configuration is used for illustrative purposes only and is not meant as an endorsement in any 

way. The DP-14 is currently under development by DPI. As such, some of the subsystems necessary to 

safely perform the aerial spray application are hypothesized (e.g., the containment system). Details of the 

example implementation are provided here to confirm the feasibility of developing a UAS with existing 

technology that can accomplish the aerial application mission and meet the speculated safety 

requirements. 

The example configuration is described in terms of the following subsystems:

 DP-14 unmanned rotorcraft

 Ground control station

 Command and control datalink

 Positioning system

 Containment system

 Ground-based detect and avoid system 

 Active obstacle avoidance system

 Payload and Spray Equipment

 Support Equipment

6.1. DP-14 Unmanned Rotorcraft

An unmanned, tandem-rotor, turbine-powered aircraft is one possible option for meeting the payload, 

transportability, and maneuverability requirements of the ConOps. The DP-14, shown in Figure 5, is one 

such rotorcraft. The rotorcraft has folding or removable blades to allow transportation by road between 

application sites and external hard points to allow installation of a spray system. An artist’s conception of 

this rotorcraft with spray attachment is shown in Figure 6. The DP-14 is expected to have a payload 

capacity of approximately 430 lb and a total vehicle gross weight of 900 lb.

Figure 5. DP-14 Model Rotorcraft from Dragonfly Pictures, Inc.
49

Figure 6. Unmanned Tandem-Rotor Precision-Spray Aircraft

The systems on the UA are typical of those used on midsize UAS they have limited size, weight, and 

power (SWAP). The UA is equipped with onboard sensors and an autopilot system that allow it to 

operate semi-autonomously. These onboard elements enable onboard position determination, onboard 

guidance computations, automatic stabilization, and fully automatic inner- and outer-loop vehicle control.

Direct operator control of the vehicle is not available as a primary or backup control mode, but the 

operator can intervene via the activation of predetermined commands. 

Automatic takeoff and landing (also referred to as launch and recovery) are required for all modes of 

operation. Automatic takeoffs include a departure from the location of engine start to the first waypoint 

that defines the commencement of the intended spray operation. Automatic landing will return the UA to 

the intended point of landing from the last waypoint of the flight plan. The UA uses a ground-based 

multi-lateration system (see Section 6.4) to determine position and recognizes position relative to predefined containment boundaries (see Section 6.5). The UA’s control system automatically lands if 

impending violation of the containment boundary is detected. The spray system is also disabled during 

such contingency maneuvers to ensure that chemicals are not sprayed outside of the containment zone.

Flight path control is fully automatic in accordance with a preloaded prescription spray map. During 

flight, the UA uses direct height measurement from a radar or laser altimeter to provide precise altitude 

control above the crops in the field. The direct height measurement is bank angle compensated to ensure 

accurate control of altitude during normal maneuvering. The UA includes a backup barometric altimeter 

for contingency management of altitude. The barometric setting for the backup altimeter is set prior to 

flight and updated between flights.

The UA does not carry a transponder, but a low-cost automatic dependent surveillance-broadcast (ADSB)-out unit may be incorporated to provide VFR traffic data to other aircraft (if permitted by SWAP 

limitations and cost). Aircraft position and state data is provided to the ground control station by datalink 

radios operating on frequencies approved for UAS operations or on frequencies approved for commercial 

or farm use, as appropriate. All operations are conducted within RLOS and most operations conducted 

within VLOS. If operations are conducted close to an airport with an operating control tower or other 

FAA facility, the ground control station will incorporate aviation band radios to maintain contact with the 

proximate facilities.

The UA design includes attributes to minimize the possibility of explosion or structural failure that 

releases high-energy parts. This includes the design, fabrication, and installation of fittings, valves, filler 
50

tubes, drains, vents, and supporting structure for the fuel, oil, and other systems containing flammable 

fluids. The turbine engine installation includes containment rings around the turbine and compressor 

sections to ensure that an engine structural failure does not allow high-energy parts to escape from the 

engine compartment. The vehicle design includes a clutch or similar device that allows the rotor system to 

freewheel in the event of engine failure or seizure. Based on these design features, certification of the 

engine under Part 33 of 14 CFR may not be required.

An onboard vehicle health management system is incorporated into the design to automatically monitor 

safety-critical components and command a contingency landing in the event of a failure. The health 

monitor may also activate contingency maneuvers such as a return to takeoff location for less critical 

failures. The pilot is alerted over the datalink of any health monitor interventions. The pilot may also 

activate similar preprogrammed interventions via datalink if there are external indications of a nonnormal state (e.g., smoke) that has not been detected onboard.

In the event of an engine failure or activation of the fuel cutoff valve associated with the contingency 

systems at very low altitudes, the vehicle is designed to descend slowly from spray height, settling to the 

surface in such a manner that the rotors will not impact the ground or any parts of the vehicle. If the 

vehicle must ascend above spray height, the autopilot is programmed to maintain a forward velocity

proportional to altitude consistent with the height-velocity (“deadman’s”) curve [32] established during 

flight testing. This ensures that the vehicle can safely land from any normal operational condition and the 

vehicle and all of its parts will stay within the containment zone.

6.2. Ground Control Station

The ground control station is integral to the ground support vehicles that transport, launch, and recover

the UA. The ground control station is portable so that its location can be optimized with respect to VLOS 

considerations, radio coverage, operational efficiency, and protection by the containment system. The 

ground control station incorporates man-portable displays and controls that allow the pilot in command to 

directly observe the operation of the UA from takeoff through landing when operating within VLOS. 

When operating beyond VLOS (BVLOS), the ground control station includes an enclosure that provides 

controlled lighting, weather protection, and additional displays as required. The enclosed ground control 

station is designed to be compliant with the Occupational Safety and Health Administration (OSHA)

requirements that provide for the safety of its occupants.

The ground control station supports the following:

 downloading and converting the prescription map to an aerial application overlay on a geospatial 

database such as Google Earth,

 converting the geospatial overlay into a series of waypoints that can serve as the basis for a lateral 

navigation plan for loading into the UA’s onboard flight management system/autopilot,

 associating spray commands with each waypoint,

 entering “no-fly” regions into the database or flight plan to protect known obstacles or human 

habitation areas within the operational zone,

 assigning precision altitudes to the waypoint plan to adjust spray distribution patterns or provide 

vertical separation from small obstacles,

 running the flight plan in simulation mode to verify the viability of the plan

 loading the tested flight plan into the UA’s computers and verifying proper loading,

 running diagnostic vehicle tests to validate flight readiness,

 communicating with visual observers (where utilized) dispatched to key locations to clear the airspace 

and the containment zone for the flight,

 activating and monitoring the containment and active obstacle detection systems,
51

 monitoring the progress of the flight visually or electronically, as needed for the operation being 

conducted,

 sending specific commands to the UA that bring it into a safe state (e.g., low hover, land, or return to 

base) if non-normal conditions exist that are not automatically detected and compensated,

 monitoring critical on-board systems of the UA or monitoring commands from the onboard health 

monitoring system, and

 bringing operations to a safe conclusion in the event of a power loss at the ground control station.

6.3. Command and Control Datalinks

The C2 datalinks operate in approved spectrum allocated for UAS conducting commercial agricultural 

operations. Operational frequencies come from spectrum designated for farm operations, UAS operations, 

or other relevant spectrum. Receivers and transmitters are tunable to allow for changing frequency 

requirements in different areas. Bandwidth requirements are minimized by the highly automated design of 

the vehicle.

The datalink operates at a power level appropriate to the range requirements for each mission. The 

datalink is frequency agile to minimize the possible effects of electromagnetic interference and provide 

link security. While operations may be conducted BVLOS, they will not be conducted beyond RLOS to 

avoid the latency and dropout issues associated with satellite relay systems. RLOS covers quarter-section 

fields at the low flight altitudes embodied in this ConOps. Signal strength is tested at startup for each 

operation. 

The UAS will have at least one C2 link for safety-critical information such as commands required for 

contingency maneuvers. Other datalinks may be used for telemetry and other non-safety-critical 

information. The vehicle incorporates automated contingency actions to execute for lost-link events. 

6.4. Positioning System

To achieve the navigation accuracy required by the ConOps, the onboard GPSs are designed to use

proprietary differential signals from a dedicated, high accuracy, ground-based receiver such as those 

typically used in survey applications. If a differential system is already available for use with groundbased farm equipment, that system may also be used for the UA provided the reliability and design of the 

ground system meets the requirements of the type certificate. A real-time kinematic GPS is another 

alternative that can be used to provide the required level of accuracy.

Wide area augmentation system (WAAS)-capable receivers may be used when the required precision for 

a given application job is around 3 meters or greater. The service provider will carry out preflight surveys 

to ensure the availability of WAAS signals.

The differential GPS is monitored from the ground control station and onboard the UA, so that operations 

may be terminated if GPS signals are lost or the required level of accuracy is not available.

6.5. Assured Containment System

An assured containment system is a localization system, independent of the autopilot, that acts to keep the 

UA within given bounds. A containment system comprises sensors to determine the vehicle state 

information, decision logic to detect an anticipated breach of containment, and the means to control the 

breach of containment (e.g., flight termination). The assured part of the concept comes from design 

attributes intended to ensure that the UA will remain in a specified area in the presence of common 

vehicle, autopilot, sensor and actuator failures. The UA design includes an assured containment system in 

part to offset reliability requirements on the UA autopilot. As posited here, an assured containment 
52

system can be realized by a smaller set of functions than a typical autopilot provides. Keeping the system 

simple facilitates certification-quality safety arguments. 

An assured containment system is not currently available on the market, though one could be developed 

using existing technology. For this application, the containment system would incorporate an 

independent system for determining the location of the UA based on three or more low power transmitters 

prepositioned to provide good multi-lateration geometry over the operational area. The UA would contain 

two receiver/processors preloaded with lateral and vertical containment boundaries, including buffers as 

necessary to allow for operation at and near boundaries. The receiver/processors would receive signals

from antennas on the vehicle and continuously triangulate to determine current lateral and vertical 

position. The current position would be differentiated to determine a velocity vector. The position and

velocity data would be processed to determine a projected time to crossing of the boundary. If the UA

does not take action to adjust its path or speed to stay within the boundaries, the containment system 

would force the vehicle to land by closing an emergency fuel shutoff valve. The valve would operate 

independently of the ship’s systems, autopilot, and primary and backup power sources. An activation 

signal would be sent to the operator via datalink and the operator would back up the automatic action with 

a command to close the normal fuel shutoff valve.

A number of alternative system designs can provide independent positioning capability: eLoran, radars, 

acoustic systems, and people who serve as spotters. An automated system was proposed to support

BVLOS operations. Ideally, automation reduces staffing requirements and error from fallible human 

judgments of positions, speeds and boundary locations.

6.6. Ground-Based Detect and Avoid (GBDAA) System

Some capability to detect and avoid other aircraft is needed despite the fact that most aerial application 

will occur just above crop height. During VLOS operations, the pilot in command and visual observers 

can provide the detect and avoid function. To support BVLOS operations, a system that can detect aircraft 

by non-visual means will be needed. An automated detect and avoid system is not currently available on 

the market, though one could be developed using existing technology. One possible option is a system 

that includes a portable ground or radar-based detect and avoid system to provide the pilot in command

with a warning if another aircraft approaches the containment area. Upon notification of an intruder, a 

signal would be sent to the UA automatically or by the pilot in command (or both) that initiates a

contingency response such as an immediate landing or low hover. A GBDAA system could be reset 

remotely by the pilot in command to resume UA operations once the hazard has passed. The GBDAA 

system would only be required to detect intruder aircraft, not compute avoidance maneuvers. For the 

ConOps, the avoidance maneuver is a single pre-programmed response that can be initiated by a single 

command from the ground control station.

A GBDAA system might use a variety of sensors such as acoustic detectors and various forms of radar. 

A particularly interesting option is a commercial-off-the-shelf marine radar modified to detect low flying 

aircraft at a minimum range of 5 miles. This range requirement supports a buffer around the planned area 

of operations of about 3 miles, assuming the radar is centrally located. This range provides sufficient time 

for the UA to execute a contingency action. The system could operate in the background and send 

automatic commands to the UA and alerts to the pilot in command when a conflict is detected. The 

system would not capable of providing resolution maneuvers but only detection alerts. 

6.7. Active Obstacle Avoidance System

The primary responsibility for avoiding known obstacles (e.g., barns or silos in the field) is functionally 

allocated to the onboard precision navigation system. The locations and boundaries of known obstacles
53

are determined during pre-mission planning and entered into the UA flight management system. The 

flight path of the UA is compared to these locations and adjusted to provide clearance from them.

To avoid unknown or dynamic obstacles as required by the ConOps, the pilot in command and visual 

observers can provide the detect and avoid function during VLOS operations. For BVLOS operation, an 

active onboard obstacle detection and avoidance system would need to be included in the system design. 

Such a system is not currently available on the market, though one could be developed using lidar, 

acoustics, radar, or other technologies. For this application, the hypothetical system could use an 

adaptation of an automotive camera-based pattern recognition system such as those produced by

Mobileye, Inc. [33] to keep cost and power requirements low. When an obstacle is detected, the 

avoidance system would send a command to the autopilot and thrust systems to execute a contingency 

landing and power down the vehicle. After any contingency landing, a crew member would be required 

to clear the hazard and reset the system.

6.8. Payload and Spray Equipment

The hypothetical system design assumes that the agricultural spray system is a permanent part of the 

vehicle and, as such, the certification of the spray system is included in the vehicle type certification. 

Agricultural requirements established by 14CFR Part 137 are not considered in this assessment.

The hypothetical system is designed to dispense liquid chemicals using a pressurized spray system. The 

available fuel and payload tankage is such that full loads of both will exceed maximum gross weight 

limitations. Thus, the amounts of fuel and chemical payload carried are chosen such that the vehicle’s 

mission endurance in fuel and payload are proportionate for each mission. The design and operation of 

the vehicle leaves adequate fuel reserves to return to the landing location any time during the mission 

with adequate margins of safety.

The vehicle structure, control systems, and spray system design take into consideration the stiffness of the 

spray booms and takeoff, landing, and maneuvering requirements. Height and bank angle compensation, 

or coordination, is provided to ensure that the spray system does not contact the ground during low 

altitude spraying just above the crop canopy. Spraying at low altitude is a necessary design requirement to 

minimize overspray resulting from wind and rotor wash entrainment.

As a safety consideration, the spray system design includes two methods of shutting off the spray. The 

primary shutoff is operated by the normal spray system and allows activation and deactivation of all or 

individual nozzles according to the requirements of the prescription map. A second independent shutoff 

system is capable of emergency shut off of all spray regardless of the status of the primary system. Such 

a system allows positive shut off by on-board or off-board activation of the containment or other 

contingency systems.

6.9. Support Equipment

The vehicle design includes support vehicles that are needed for transportation, launch, servicing, and 

recovery of the UA, as well as providing support for the agricultural service (e.g., loading chemicals). The 

specimen configuration includes one vehicle capable of transporting the UAS over roads and highways in 

the U.S., including secondary roads typically found in rural farm areas. The vehicle design complies with 

all federal and state motor vehicle regulations regarding weight and size and incorporates required safety 

features. The transport vehicle also incorporates leveling and rotor wash protection features that allow it 

to serve as the initial launch and final recovery platform. A separate vehicle with off-road capabilities 

provides a capability to retrieve the UA from a field in the event of a contingency landing that does not 

allow continued flight. This vehicle is also used to deploy observers and any necessary field equipment. 

Another vehicle carries fuel, oil, and chemical supplies to allow field replenishment of the vehicle and 
54

spray system. This vehicle incorporates safety features for fire and explosion suppression consistent with 

the liquids being carried.
55

7. Conclusions

This report provides an example of the first major product in a civil aircraft’s type certification process, 

namely, the type certification basis—in this case, for an unmanned rotorcraft performing an aerial 

application operation. The purpose of this effort is to determine, in a general sense, plausible 

airworthiness requirements for an unmanned rotorcraft in a low-risk operation. Due to the narrow scope 

of this effort—a specific UA performing a specific type of operation—this work does not provide 

definitive information applicable to all UAS in all possible operational contexts. The narrow scope, 

however, allows for serious, in-depth consideration of real-world concerns, peculiarities, and special 

mitigations for a particular UA and operation. If a larger variety of vehicles had been chosen or a wider 

range of operations, then this work would either have been either too general to be useful or, since all 

potential hazards must be mitigated, too restrictive to be a practical/economic operation. The intent was 

to suggest a strawman set of design and performance requirements, based on Part 27, to use as a starting 

point for establishing a reasonable certification basis for similar UA performing similar low-risk 

operations. Approximately 25% of the regulations in Part 27 were directly applicable to this type 

certification basis without significant modification. In total, approximately 55% of the regulations in Part 

27 were useful in addressing primary hazards associated with the UAS and its operation.

One key observation from this activity is that there is a fundamental connection between the aircraft, its 

ConOps, and the safety of the system. Regulatory requirements for most CPA are developed implicitly 

around an operational model of transporting people and cargo from one point to another. No specific 

documentation of that operation is required in the aircraft certification process. Many UAS operations do 

not fit the CPA transportation model. UAS operations for tasks like surveillance, inspection, and 

agriculture, involve taking off and landing from the same point, while other UAS operations involve 

significant time loitering in a designated area—all different from the transportation model. Different 

operational models have the potential to introduce different hazards that affect requirements for UA 

systems and equipment. By providing details about the operation, special considerations inherent to the 

safety of the UA are revealed. In this case study, for example, operation within a defined geospatial 

containment volume that contains no people is a special consideration that significantly impacts design 

and performance considerations. Other operations may have different hazards, necessitating different 

safety considerations. In any case, the operation and operational environment have a non-trivial effect on 

design requirements. So, for UAS, documentation of the ConOps may become an essential artifact for 

type certification. 

Another key observation of this work is that one hazard may mask a secondary hazard. Consequently, 

efforts to mitigate a hazard must ensure that secondary hazards are also mitigated. For example, a crash 

of an unmanned aerial applicator, in a field cleared of people, would not be considered by most to be a 

safety concern. Such a crash would have economic implications, but no direct safety implications. 

Further consideration of such an event, however, resulted in identifying hazards related to (a) detecting 

people who may enter the field during the operation and (b) release of high-energy parts that could exit 

the containment area. Hazards, especially those relevant to people on the ground, might be different from 

those on a typical CPA project, and might not be obvious at first glance. 

The final key observation is that hazards in UAS might be best identified by considering ways in which 

the public (i.e., people on the ground or in other aircraft) might be injured. The transitive notion of safety, 

that is, the idea that protecting the aircraft will, in turn, protect the public, is neither necessary nor 

sufficient for many UAS and their intended operations. For agricultural operations and perhaps many 

other UAS operations, the regulations need only be concerned with protecting the public. For many UAS 

operational models, economic considerations and insurance, not airworthiness regulation, will become 

primary drivers for requirements to protect the UA from hull loss. 
56

Further work in the form of additional case studies and operational experience is needed to substantiate or 

refute these observations and provide data needed to inform the development of regulatory policy and 

standards for different UAS types and operations.
57

8. References

[1] United States House of Representative, FAA Modernization and Reform Act of 2012, Report 

112-381, 112th Congress, 2d Session, Conference Report to accompany H.R. 658, February 1, 

2012.

[2] Department of Transportation, Notice of Proposed Rulemaking, Operation and Certification of 

Small Unmanned Aircraft Systems, Docket No.: FAA-2015-0150; Notice No. 15-01, Issued 

February 15, 2015.

[3] Federal Aviation Administration, Section 333, [Online]. Available: 

https://www.faa.gov/uas/legislative_programs/section_333/

[4] Federal Aviation Administration, Integration of Civil Unmanned Aircraft Systems (UAS) in the 

National Airspace System (NAS) Roadmap, First Edition, November 2013. 

[5] European Aviation Safety Agency, Introduction of a Regulatory Framework for the Operation of 

Drones, Advanced Notice of Proposed Ammendment, 2015-10, July 2015.

[6] National Research Council, Autonomy Research for Civil Aviation: Toward a New Era of Flight, 

Committee on Autonomy Research for Civil Aviation, The National Academies Press, 

Washington D.C., 2014.

[7] Oztekin, Ahmet, Flass, Cynthia, and Lee, Xiaogong, Development of a Framework to Determine 

a Mandatory Safety Baseline for Unmanned Aircraft Systems, Journal of Intelligent and Robotic 

Systems 65, No. 1-4, pp. 3-26, 2012.

[8] Clothier, Reece A., Palmer, Jennifer L., Walker, Rodney A., and Fulton, Neale L., Definition of 

an Airworthiness Certification Framework for Civil Unmanned Aircraft Systems. Safety Science, 

2011.

[9] Clothier, Reece A., Williams, Brendan P., Coyne, James, Wade, Mark, and Washington, Achim, 

Challenges to the Development of an Airworthiness Regulatory Framework for Unmanned 

Aircraft Systems, 16th Australian Aerospace Congress, Melbourne, Australia, February 23-24, 

2015. 

[10] Federal Aviation Administration, FAA Order 8130.2H, Airworthiness Certification of Products 

and Articles, Section 6. Light Sport Aircraft Category Airworthiness Certifications, February 4, 

2015.

[11] United States Government, (undated), Title 14 Code of Federal Regulations, Electronic Code of 

Federal Regulation, Chapter III—Commercial Space Transportation.

[12] Ryan, Wes, UAS Certification, The Path to 21.17(b) Type Certification & Design Standards), 

Briefing given February 20, 2014.

[13] United States Government, (undated), Title 14 Code of Federal Regulations, Eletronic Code of 

Federal Regualtion, Part 27—Airworthiness Standards: Normal Category Rotorcraft, [Online], 

Available: http://www.ecfr.gov/cgi-bin/ECFR?page=browse

[14] Joint Authorities for Rulemaking of Unmanned Systems (JARUS) Working Group -3 

Airworthiness, Certification Specification for Light Unmanned Rotorcraft Systems (CS-LURS), 

Version 1.0, October 30, 2013.

[15] Federal Aviation Administration, FAA Order 8110.112, Standardized Procedures for Usage of 

Issue Papers and Development of Equivalent Levels of Safety Memorandums, June 15, 2010.
58

[16] Hayhurst, Kelly J., Maddalon, Jeffrey M., Neogi, Natasha A., and Verstynen, Harry A., A Review 

of Current and Prospective Factors for Classification of Civil Unmanned Aircraft Systems, 

NASA/TM-2014-218511, August 2014.

[17] DigitalGlobe Press Release “DigitalGlobe Announces Second 30-Centimeter Satellite to Launch 

in Mid-2016”, issued 31 July 2014. [Online]. Available: 

http://investor.digitalglobe.com/phoenix.zhtml?c=70788&p=RssLanding&cat=news&id=195390

4

[18] Virginia Cooperative Extension, Precision Farming Tools: Variable-Rate Application, Publication 

442-505, 2011.

[19] Ali, Mir B., Characteristics and Production Costs of U.S. Sugarbeet Farms, United States 

Department of Agriculture, Statistical Bulletin No. 974-8, October 2004.

[20] FAA Operational Approval Notice N 8900.1 Volume 16, Unmanned Aircraft Systems, 

[21] International Civil Aviation Organization, Unmaned Aircraft Systems (UAS), Cir 328, 2011.

[22] RTCA SC-189, Guidelines for Approval of the Provision and Use of Air Traffic Services 

Supported by Data Communications, RTCA DO-264, December 14, 2000.

[23] Society of Automotive Engineers (SAE), SAE ARP 4761, Guidelines and Methods for 

Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment, December 

1996.

[24] Federal Aviation Administration, System Safety Analysis and Assessment for Part 23 Airplanes, 

FAA Advisory Circular 23.1309-1E, November 11, 2011.

[25] Joint Authorities for Rulemaking of Unmanned Systems, AMC RPAS.1309: Remotely Piloted 

Aircraft Systems, Systems Safety Assessment, Working Group 6: UAS Systems Safety Analysys 

(1309), Issue 1, January 2014.

[26] European Aviation Safety Agency, Special Condition: Equipment, Systems, Installations, SCRPAS.1309-01, July 24, 2015.

[27] Federal Aviation Administration, Notice 8900.227, Unmanned Aircraft Systems (UAS) 

Operational Approval, Effective 7/30/2013 through 7/30/2014.

[28] Federal Aviation Administration, FAA Order 8110.4C, Type Certification, October 26, 2005.

[29] AIA, GAMA, and the FAA Aircraft Certification Service, The FAA and Industry Guide to 

Product Certification, second edition, Secptember 2004, Online. Available: 

https://www.faa.gov/aircraft/air_cert/design_approvals/media/CPI_guide_II.pdf. 

[30] Federal Aviation Administration, FAA Advisory Circular 27-1B, Certification of Normal 

Category Rotorcraft, July 25, 2014.

[31] Federal Aviation Administration, Integration of Unmanned Aircraft Systems into the National 

Airspace System, Concept of Operations, V2.0, September 28, 2012.

[32] Johnson, Wayne, Helicopter Theory, Dover Publication, revised edition, October 6, 1994.

[33] Mobileye, Processing Platforms, [Online], Available: http://mobileye.com/enen/technology/processing-platforms/
59

Appendix. Rationale for the Mock Type Certification Basis

Just as the intent behind a regulation is not always obvious, neither is the reasoning for why a requirement 

might or might not be considered applicable in a different context. The rationale provided in Table A.1

attempts to provide insight into the assessment of each of the Part 27 requirements for applicability to the 

AgR-1 and inclusion in the mock type certification basis. Table A-1 lists each of the Part 27 requirements

and indicates whether each requirement is included in the mock type certification basis, excluded from the 

mock type certification basis, or “rolled up” into one of the supplemental issue papers (CMS, SI, or PPS). 

For requirements included in the mock type certification basis, the text of the proposed requirement is 

given, along with rationale for why it is included or modified. Additions to the original text are indicated 

in blue italic face and deletions are indicated by striking through the text. For requirements that are rolled 

up, a brief summary of the requirement is given, along with rationale for why it has been rolled up. 

The rationale, by its nature, is subjective. The intent is to offer a starting point for discussing potential 

changes to existing regulations to better define the desired safety characteristics of a UAS and its 

ConOps. A few common themes appear in the rationale, including the following reasons for excluding a 

requirement from the type certification basis:

(1) Out of vehicle scope. This means that the Part 27 requirement is intended for a rotorcraft whose 

characteristics are not consistent with those of the AgR-1, e.g., piston engines and multiple engines. 

Vehicles with tandem rotors and a single turbine engine and vehicles with a single rotor, a tail rotor, 

and a single turbine engine are in scope. 

(2) Out of ConOps scope. This means that the operational aspects specified in the Part 27 requirement 

are not relevant to the ConOps; e.g., icing conditions, lightning, operation beyond radio line-of-sight, 

presence of a manual reversion mode (.e.g., stick-to-surface control), taxiing, and skis and floats.

(3) Does not map to a hazard. This means that the Part 27 requirement is not directly relevant to a 

primary (catastrophic, hazardous, or major) hazard identified in the hazard analysis. For example, an 

event resulting in hull loss is not a hazard under the ConOps. There are, however, hazards associated 

with loss of rotor system integrity; e.g., shedding of high energy parts. 

(4) Not UAS relevant. This means that the Part 27 requirement is irrelevant to a UAS by the design or 

operational characteristics of unmanned vehicles. For example, requirements related to crew or 

occupant protection, such as seat belts, are not UAS relevant.

(5) Secondary hazard. This means that the hazard that underlies the Part 27 requirement is relevant to the 

AgR-1 under its ConOps, but not to the same degree as for a Part 27 rotorcraft. For example, engine 

seizure is not catastrophic unless coupled with the failure of a disconnect device for the rotor system.

(6) Mitigated by other regulation. For some systems (e.g., the rotor system) for the provision of a device 

to protect the system obviates the need for other regulations. For example, loss of fuel pressure 

causing engine flameout is not catastrophic even if a hull loss occurs as long as the device that 

disconnects the engine from the drive system protects the drive system integrity.

The rationale in Table A.1 is intentionally informal and uses a shorthand description of the common 

themes. The terms “crew” and “crewmember” used herein include pilots, sensor/payload operators, 

visual observers, and other persons as appropriate or required to ensure safe operation and maintenance of 

the aircraft
60

Table A.1. Applicability of Part 27 Paragraphs to an Unmanned Aerial Applicator

Part 27 

Paragraph

Action Paragraph text or Summary

Rationale for Action

Subpart A—General

§27.1 

Applicability

Excluded Summary: This paragraph describes the types of rotorcraft subject to Part 27. 

Rationale: Out of vehicle scope. Out of ConOps scope. The UAS and ConOps are 

different from conventional Part 27 rotorcraft.

§27.2 

Special 

retroactive 

requirements

Excluded Summary: This paragraph describes special considerations for (a) rotorcraft 

manufactured after Sept 16, 1992 related to seats and (b) type certified prior to October 

18, 1999.

Rationale: Not UAS relevant. The UAS will not need seats. Furthermore, any vehicle 

operating under the G-1U will be certified after October 18, 199.

Subpart B—Flight

General

§27.21

Proof of 

compliance

Modified Each requirement of this subpart G-1U 

Issue Paper must be met. at each 

appropriate combination of weight and 

center of gravity within the range of 

loading conditions for which certification 

is requested. This must be shown

(a) Bby tests upon a rotorcraft of the type 

for which certification is requested, or by 

calculations based on, and equal in 

accuracy to, the results of testing; and 

(b) By systematic investigation of each 

required combination of weight and center 

of gravity if compliance cannot be 

reasonably inferred from combinations 

investigated.

Rationale: “Subpart” was changed to “issue 

paper” because the original subpart, as a 

whole, is not applicable. The intent of this 

paragraph is that requirements included in 

the issue paper must be verified by testing 

and analysis of the rotorcraft as applicable. 

Only those loading conditions that could 

lead to loss of structural integrity of the 

rotor system are of concern. The 

requirement for test and/or analysis for all 

of the weight and center of gravity 

combinations called for in Part 27 was 

simplified because the unmanned rotorcraft 

has fewer loading conditions that are safety 

critical. Therefore, language requiring test 

and/or analysis at all weight/cg 

combinations was deleted.

Furthermore, weight and center of gravity 

are not the only important parameters that 

may affect loading conditions. The 

applicant should determine which 

parameters, including weight and center of 

gravity, are critical to structural integrity of 

the rotor system and demonstrate through 

test and analysis that the aircraft can handle 

these parameters with adequate safety 

margins. Weight and center of gravity are 

rolled up along with other critical 

parameters in separate issue papers for 

structural integrity and for controllability, 

maneuverability, and stability. 
61

§27.25 

Weight limits

Rolled up 

to CMS(a) 

& SI

Summary: This paragraph establishes requirements for determining maximum, 

minimum, and total weights including jettisonable payloads for manned helicopters. 

Rationale: Weight, weight distribution, and inflight changes in weight can affect vehicle 

moments of inertia and control margins, affecting CMS. For a single purpose UAS 

design, detailed establishment of all of the weights called for in Part 27 might be 

unnecessary. The CMS rollup requires that the applicant determine which weight and 

loading conditions are critical to vehicle CMS and to demonstrate that the vehicle 

control system can handle these weights with adequate safety margins.

These weights also have a direct effect on structural strength requirements for the rotor 

system, the drive system, and supporting structure. The SI rollup requires that the 

applicant determine which weight and loading conditions are critical to vehicle 

structural requirements, affecting rotor system integrity, and demonstrate that the 

vehicle design and fabrication can handle these weights with adequate safety margins.

§27.27 

Center of 

gravity limits

Rolled up 

to CMS(a) 

and SI

Summary: This paragraph requires the applicant to establish various centers of gravity, 

especially at the extremes (forward, aft, lateral).

Rationale: The requirements of this paragraph are reasonable for a UAS design in a 

restricted operational context. However, because the requirements are tied to the 

weights established under §27.25, this paragraph was rolled up with §27.25. The 

generalized requirement is for the applicant to establish which center of gravity limits 

are critical and ensure that the vehicle is safely controllable and maneuverable for this 

range of values.

Because the loading on each rotor of a tandem rotor design is affected by center of 

gravity locations and the center of gravity is generally related to the weights established 

under §27.25, a generalized requirement was included in the SI rollup for the applicant 

to establish which center of gravity limits are critical and ensure that the vehicle design 

provides adequate safety margins for this range of values.

§27.29 

Empty weight 

and 

corresponding 

center of 

gravity

Excluded Summary: This paragraph requires establishing empty weight and center of gravity used 

for stability analysis.

Rationale: Does not map to a hazard. Loss of the vehicle within containment is not 

hazardous.

§27.31 

Removable 

ballast

Excluded Summary: This paragraph allows the use of removable ballast to help with center of 

gravity

Rationale: Out of vehicle scope.

§27.33 

Main rotor 

speed and pitch 

limits

Rolled up 

to CMS(a) 

and SI

Summary: This paragraph requires the applicant to establish main rotor speed and pitch 

limits used in determining centripetal, bending, and other critical loads applied to the 

rotors.

Rationale: Main rotor speed and pitch limits relate primarily to structural integrity 

requirements of the rotor system and are rolled up in the issue paper on structural 

integrity. However, main rotor speed and pitch limits can also affect CMS

considerations at limiting conditions, such as at max gross weights, takeoffs and 

landings at max slope limits, and at the never exceed speed (Vne). This paragraph was 

rolled up into the CMS issue paper to require the applicant to consider these factors in 

designing the vehicle control and stabilizations systems.

Performance

§27.45

General 

Excluded Summary: This paragraph prescribes how performance requirements are to be 

interpreted.

Rationale: Does not map to a hazard. Not UAS relevant.
62

§27.49 

Performance at 

minimum 

operating 

speed

Excluded Summary: This paragraph requires an applicant to determine performance at minimum 

operating speed.

Rationale: Out of ConOps scope. Does not map to a hazard.

§27.51 

Takeoff 

Rolled up 

to CMS(a) 

and SI

Summary: This paragraph establishes minimum requirements for controllability and 

performance of the vehicle during takeoff with critical values of weight and center of 

gravity. 

Rationale: While the controllability requirement is stated in terms of pilot skill 

requirements, that are not applicable for the UAS, the requirement that the takeoff not 

require exceptionally favorable conditions is applicable to the UAS autopilot design. 

Therefore this requirement was included in the rollup. Subparagraph (b) that requires

that the vehicle be capable of a safe landing following an engine failure during the 

takeoff profile also was deemed applicable but only where the inability to land safely 

represents a risk to persons or property on the ground. The rollup includes language that 

makes clear that requirements such as this paragraph are only applicable under some 

circumstances, thus opening the door for operational or other mitigations to the hazards 

to persons and property on the ground.

§27.65 

Climb: all 

engines 

operating

Excluded Summary: This paragraph requires an applicant to establish the steady rate of climb 

under various conditions.

Rationale: Does not map to a hazard. Note: Requirements for avoiding obstacles are in 

the Detect & Avoid Dynamic Obstacles issue paper included in the G-1U.

§27.67 

Climb: one 

engine 

inoperative

Excluded Summary: This paragraph, applicable to multiengine rotorcraft, requires establishing 

steady rate of climb with one engine out.

Rationale: Out of vehicle scope.

§27.71 

Autorotation 

performance

Excluded Summary: This requires the establishment of the best angle of glide and minimum rate 

of sink speeds in autorotation.

Rationale: Out of ConOps scope. Does not map to a hazard.

§27.75 

Landing

Rolled up 

to CMS(a) 

and SI

Summary: This paragraph, similar in intent to paragraph §27.51, requires the vehicle to 

be capable of being landed smoothly without exceptional pilot skill or exceptionally 

favorable conditions during both a normal approach and an autorotative approach. 

Rationale: Using the same logic as the takeoff case, the pilot skill requirement does not 

apply since there is no direct inner loop control by a pilot, but the requirement that a 

smooth landing be made without exceptionally favorable conditions may be directly 

applicable to the autopilot design. The general sense of the paragraph was included in 

the CMS rollup.

§27.87 

Height-speed 

envelope

Rolled up 

to CMS(a) 

Summary: This paragraph requires that any combinations of height and forward speed 

for which a safe landing cannot be made must be established for the relevant power 

failure condition. This limiting condition is sometimes known as the “Dead Man’s 

Curve”. 

Rationale: Engine failure from a height/speed combination that does not allow a 

successful autorotation would likely result in destruction of the rotor system and release 

of high energy parts. This paragraph, especially (b)(1) which requires full autorotation 

for a single engine helicopter, was included in the rollup as one of the critical conditions 

that the applicant must identify and mitigate.
63

Flight Characteristics

§27.141

General

Rolled up 

to CMS(a) 

and SI

Summary: This paragraph requires that the vehicle be capable of maintaining any 

required flight condition and be able to transition smoothly between flight conditions 

without exceptional pilot skill and without danger of exceeding limiting load factors. A 

list of parameters for which critical conditions must be tested, including weights, center 

of gravity, altitudes, temperatures, engine failure conditions, etc., are specified. 

Rationale: While the exceptional piloting skill requirement would not be applicable to a

vehicle with no provisions for inner loop pilot control, the same requirements would 

apply to the autopilot design and implementation. Subparagraph (c) also requires that 

the vehicle possess any required flight characteristic necessary for night or instrument 

flight, if certification for such conditions is requested. Since the ConOps includes night 

and limited visibility operations, this subparagraph was included in the CMS and SI 

rollups.

§27.143

Controllability 

and maneuverability 

Rolled up 

to CMS(a)

Summary: This paragraph requires that the vehicle be safely controllable and 

maneuverable for a specified set of normal operations, such as takeoff, landing, and 

steady flight, and for non-normal conditions, such as autorotation (if implemented) and 

power-on recoveries. The paragraph also specifies that adequate control margins exist at 

Vne for critical values of relevant parameters. The paragraph further specifies wind and 

density altitudes for which the vehicle must be safely controllable and maneuverable and 

critical values of other parameters. 

Rationale: Under the ConOps, neither Vne, nor 7000 ft will likely be reached. However, 

the general requirement that the vehicle be safely controllable and maneuverable over a 

relevant set of conditions with critical values of other parameters, such as weight, center 

of gravity, rotor speed, and power condition would be a necessary precondition for 

maintaining rotor system integrity. 

§27.151

Flight controls 

Rolled up 

to CMS(a)

Summary: This paragraph sets limits on breakout forces, friction, and preloads, and 

requires that the control system be designed and installed such that the vehicle responds 

directly and smoothly to control system inputs. 

Rationale: Although the UAS has no inner-loop control by a human operator, this 

requirement may be applicable to the autopilot design and was included in CMS(a).

§27.161

Trim control 

Excluded Summary: This paragraph requires that the rotorcraft be trimmable for the longitudinal, 

lateral, and collective controls.

Rationale: Out of vehicle scope. Since the AgR-1 inner loop is controlled exclusively 

by an autopilot, trim forces are not relevant.

§27.171

Stability: 

general

Excluded Summary: This paragraph requires an applicant to consider pilot fatigue and strain in 

designing stability characteristics.

Rationale: Not UAS relevant, because the remote pilot would not be subject to stability 

characteristics.

§27.173

Static 

longitudinal 

stability 

Rolled up 

to CMS(a)

Summary: This paragraph specifies requirements for design and testing for static 

longitudinal stability throughout the full range of altitude allowed under the rotorcraft’s 

certification. 

Rationale: There should be no requirements on static stability for a completely 

automatic control system. The requirement for testing across the full range of altitude is 

overly burdensome. However, this requirement may be applicable to the autopilot 

design and testing should be considered with §27.175 and §27.177 for CMS.
64

§27.175

Demonstration 

of static 

longitudinal 

stability 

Rolled up 

to CMS(a)

Summary: This paragraph specifies requirements for testing static longitudinal stability 

in different phases of flight, under different conditions.

Rationale: Same logic as §27.151. There should be no requirements on static stability 

for a completely automatic control system. However, this requirement may be 

applicable to the autopilot design and demonstration and considered for CMS. 

§27.177

Static 

directional 

stability 

Rolled up 

to CMS(a)

Summary: This paragraph relates to sense and direction of motion of the vehicle in 

response to movement of the directional controls.

Rationale: There should be no requirements on static directional stability for a 

completely automatic control system. However, this requirement may be applicable to 

the autopilot design and considered for CMS.

Ground and Water Handling Characteristics

§27.231

General 

Rolled up 

to CMS(a)

Summary: This paragraph relates primarily to “handling characteristics.” Most handling 

characteristics are pilot perceptions of the controllability and maneuverability of the 

vehicle.

Rationale: Handling characteristics are not applicable to a UAS that is not under direct 

control of a human operator. However, the paragraph also states that the vehicle must be 

free from uncontrollable tendencies in any condition expected in operation. This may be 

a relevant requirement for protecting rotor system integrity and was included in the 

rollup.

§27.235 

Taxiing 

condition 

Excluded Summary: This paragraphs deals with withstanding loads related to taxiing the 

rotorcraft.

Rationale: Out of ConOps scope.

§27.239 

Spray 

characteristics 

Excluded Summary: This paragraph deals with mitigating the possibility of spray (from water 

operation) that can obscure a pilot’s vision.

Rationale: Out of ConOps scope.

§27.241 

Ground 

resonance 

As is The rotorcraft may have no dangerous 

tendency to oscillate on the ground with 

the rotor turning.

Rationale: This paragraph was included 

because of potential hazards from ground 

resonance to the (ground) crew in proximity 

during takeoff and landing.

Miscellaneous Flight Requirements

§27.251 

Vibration 

Rolled up 

to SI

Summary: This paragraph requires that the vehicle be free of excessive vibration for 

applicable speed and power conditions. 

Rationale: While vibration can affect structural strength and fatigue requirements the 

requirement is of interest only as it might affect rotor system integrity. Since the 

relationship between vibration and rotor system structural integrity might have many 

dimensions, including inspection types and frequencies, lifetime limits on parts, etc., this 

requirement would best be addressed as a part of the overall considerations to ensure 

rotor system integrity.

Subpart C—Strength Requirements

General

§27.301 

Loads 

Excluded Summary: This paragraph requires loads affecting structural strength requirements to be 

in equilibrium with inertia forces.

Rationale: Does not map to a hazard.

§27.303 

Factor of 

safety 

Excluded Summary: This paragraph specifies the factor of safety to be used with loads.

Rationale: Does not map to a hazard. The requirement in §27.602 addresses design 

requirements for critical parts.
65

§27.305 

Strength and 

deformation 

Excluded Summary: This paragraph requires tests to ensure that structure does not permanently 

deform or fail under load conditions.

Rationale: Does not map to a hazard.

§27.307 

Proof of 

structure 

Rolled up 

to CMS(b) 

& SI

Summary: This paragraph requires that an applicant show by analysis or other tests that 

the structure meets the strength and deformation requirements of the subpart. 

Rationale: Since the requirements specifically include limit load tests of the control 

system including control surfaces, this paragraph was rolled up into the CMS issue 

paper.

§27.309 

Design 

limitations 

Rolled up 

to CMS(b) 

and SI

Summary: This paragraph sets values for parameters considered critical for showing 

compliance with the structural requirements. 

Rationale: Parameters such as rotor speed and forward, rearward, and sideward speeds, 

affect the control system requirements and should be considered in the rolled up CMS

requirements. The roll-up allows the applicant to establish which parameters are critical, 

as opposed to specifying them in the requirement.

Flight Loads

§27.321 

General

Rolled up 

to CMS(a) 

and SI

Summary: This paragraph specifies assumptions about flight load factors and provides 

general guidance for complying with flight load requirements in Part 27. 

Rationale: Since load factors are induced by control movements, the general 

requirement to address flight loads with respect to controllability and structural integrity 

should be considered. This may drive design requirements on the autopilot. This 

requirement was included in the CMS and SI rollups.

§27.337 

Limit 

maneuvering 

load factor 

Rolled up 

to CMS(a) 

and SI

Summary: This paragraph specifies a range of limiting load factors in terms of the 

probability of being exceeded as shown by analysis and flight tests. 

Rationale: Since load factors are induced by control movements this may be considered 

as a design requirement on the autopilot and thus was included in the rollups.

§27.339 

Resultant limit 

maneuvering 

loads.

Excluded Summary: This paragraph describes assumptions about how loads from limit 

maneuvering load factors should act and defines a rotor tip speed ratio. 

Rationale: This paragraph provides supporting information for §27.337. Because 

§27.337 may be interpreted or applied in different ways for UAS, this paragraph is not 

necessary for the type certification basis.

§27.341 

Gust loads

Excluded Summary: This paragraph requires rotorcraft to withstand loads from vertical wind 

gusts.

Rationale: Out of ConOps scope. Secondary hazard.

§27.351 

Yawing 

conditions

Excluded Summary: This paragraph specifies requirements for designing for loads under various 

conditions in unaccelerated flight with zero and maximum achievable yaw.

Rationale: Out of ConOps scope. Secondary hazard.

§27.361 

Engine torque

Excluded Summary: This paragraph specifies minimum values for limit torque for different 

engine types to protect the engine from mechanical overload.

Rationale: Secondary hazard.

Control Surface and System Loads

§27.391 

General 

Rolled up 

to CMS(b) 

& SI

Summary: This paragraph establishes what elements of the control system fall under 

subsequent paragraphs which specify design requirements. 

Rationale: The elements specified (auxiliary rotors, fixed or movable control surfaces, 

and each system operating any flight control) might apply in some form and thus were 

rolled up to CMS(b) and SI.
66

§27.395 

Control system 

Rolled up 

to CMS(b)

Summary: This paragraph establishes the maximum loads that the control system must 

be designed to handle. 

Rationale: The requirements are expressed primarily in terms of pilot-applied loads, 

which would not be relevant but the requirements also covers loads from power 

actuators and these are relevant. The paragraph also specifies other conditions that must 

be considered in control system design. These include friction, jamming, fatigue, 

inertias, and gusts, which would be relevant to maintaining the integrity of the rotor 

control system. This paragraph was rolled up into the CMS Issue Paper to ensure that 

the applicant addresses power actuator loads and the various other design requirements 

that would ensure rotor system integrity.

§27.397 

Limit pilot 

forces and 

torques 

Excluded Summary: This paragraph specifies limit pilot forces.

Rationale: Not UAS relevant.

§27.399 

Dual control 

system 

Excluded Summary: This paragraph places requirements on dual flight control systems to 

withstand loads associated with specified pilot forces.

Rationale: Not UAS relevant.

§27.411

Ground 

clearance: tail 

rotor guard 

Modified For rotorcraft with tail rotors:

(a) It must be impossible for the tail rotor 

to contact the landing surface during a 

normal landing. 

(b) If a tail rotor guard is required to show 

compliance with paragraph (a) of this 

section—

(1) Suitable design loads must be 

established for the guard; and 

(2) The guard and its supporting structure 

must be designed to withstand those loads.

Rationale: This paragraph was modified to 

increase the applicability of the type 

certification basis to non-tandem rotorcraft. 

Impact of the tail rotor with the ground may 

lead to loss of integrity of the tail rotor and 

result in high energy parts being ejected 

from the containment zone. 

Additionally, the crew is in proximity to the 

rotorcraft during landing. Thus a loss of 

rotor hub integrity may result in crew 

impact from any ejected parts (high energy 

or not). Furthermore, since there is likely a 

physical connection between the tail rotor 

and the main rotor, damage to the tail rotor 

might cause damage to the main rotor, 

leading to a further ejection of high energy 

parts. 

§27.427

Unsymmetrical 

loads 

Modified For rotorcraft with tail rotors:

(a) Horizontal tail surfaces and their 

supporting structure must be designed for 

unsymmetrical loads arising from yawing 

and rotor wake effects in combination with 

the prescribed flight conditions.

(b) To meet the design criteria of paragraph 

(a) of this section, in the absence of more 

rational data, both of the following must be 

met:

(1) One hundred percent of the maximum 

loading from the symmetrical flight 

conditions acts on the surface on one side 

of the plane of symmetry, and no loading 

acts on the other side.

(2) Fifty percent of the maximum loading 

from the symmetrical flight conditions acts 

Rationale: This paragraph was modified to 

increase the applicability of the type 

certification basis to non-tandem rotorcraft. 

(a) Given the critical loading profile 

determined in §27.21 and/or CMS(a) and 

(b), a demonstration of structural integrity 

of the rotor hub under maximal loading 

applied at both full and half moments of 

inertia for the rotor disc is regarded as being 

sufficient to prevent the frequent ejection of 

high energy parts from the containment area 

under asymmetric loading conditions.

(b) Given the critical loading profile 

determined in §27.21 and/or CMS(a) and 

(b), empennage tail rotor surfaces must 
67

on the surface on each side of the plane of 

symmetry but in opposite directions.

(c) For empennage arrangements where the 

horizontal tail surfaces are supported by 

the vertical tail surfaces, the vertical tail 

surfaces and supporting structure must be 

designed for the combined vertical and 

horizontal surface loads resulting from 

each prescribed flight condition, 

considered separately. The flight 

conditions must be selected so the 

maximum design loads are obtained on 

each surface. In the absence of more 

rational data, the unsymmetrical horizontal 

tail surface loading distributions described 

in this section must be assumed.

further assure structural rotor hub integrity 

under combined longitudinal and lateral 

maximal loading profiles for each critical 

flight condition, unless it can be 

demonstrated that lower values are only 

ever achieved. This will sufficiently 

mitigate the ejection of high energy parts 

from the containment area under maximal 

lateral and longitudinal loading conditions.

Ground Loads

§27.471 

General 

Excluded Summary: This paragraph provides general guidance for what is meant by limit ground 

loads (external loads), and guidance for selecting critical centers of gravity with respect 

to maximum load on the landing gear.

Rationale: Secondary hazard.

§27.473 

Ground 

loading 

conditions and 

assumptions 

Excluded Summary: This paragraph sets requirements for establishing design maximum weight

used in determining strength requirements for ground loads.

Rationale: Secondary hazard.

§27.475 

Tires and 

shock 

absorbers 

Excluded Summary: This paragraph states assumptions on tire and shock absorber positions for 

landing, to be used in determining strength requirements.

Rationale: Secondary hazard.

§27.477 

Landing gear 

arrangement 

Excluded Summary: This paragraph specifies how the wheels of a landing gear should be arranged 

with respect to the center of gravity for paragraphs related to taxiing and some load 

characteristics.

Rationale: Secondary hazard.

§27.479 

Level landing 

conditions 

Excluded Summary: This paragraph specifies landing load conditions to be considered in 

establishing strength requirements.

Rationale: Secondary hazard.

§27.481 

Tail-down 

landing 

conditions 

Excluded Summary: This paragraph specifies tail down landing conditions to be considered in 

establishing strength requirements.

Rationale: Secondary hazard.

§27.483 

One-wheel 

landing 

conditions 

Excluded Summary: This paragraph specifies one wheel landing conditions to be considered in 

establishing strength requirements.

Rationale: Secondary hazard.
68

§27.485 

Lateral drift 

landing 

conditions 

Excluded Summary: This paragraph specifies lateral drift landing conditions to be considered in 

establishing strength requirements.

Rationale: Secondary hazard.

§27.493 

Braked roll 

conditions 

Excluded Summary: This paragraph specifies braked roll conditions to be considered in 

establishing strength requirements.

Rationale: Secondary hazard.

§27.497 

Ground 

loading 

conditions: 

landing gear 

with tail 

wheels 

Excluded Summary: This paragraph specifies ground loading conditions for rotorcraft with tail 

wheels.

Rationale: Secondary hazard.

§27.501 

Ground 

loading 

conditions: 

landing gear 

with skids 

Excluded Summary: This paragraph specifies ground loading conditions for rotorcraft with 

landing gear with skids.

Rationale: Secondary hazard.

§27.505 

Ski landing 

conditions 

Excluded Summary: This paragraph specifies ground loading conditions for rotorcraft with skis.

Rationale: Out of ConOps scope.

Water Loads

§27.521 

Float landing 

conditions

Excluded Summary: This paragraph specifies loading conditions for rotorcraft certificated for 

float operation.

Rationale: Out of ConOps scope.

Main Component Requirements

§27.547 

Main rotor 

structure 

Rolled up 

to SI

Summary: This paragraph specifies conditions and values for which each main rotor 

system must be designed. 

Rationale: The specific conditions and values should be screened with respect to the 

specific risks associated with an unmanned vehicle in an agricultural application in rural 

areas, especially given that the safety issue is limited to rotor system integrity under a 

very narrow set of operating conditions. Thus, the paragraph was relegated to the issue 

paper where critical conditions related to rotor system integrity could be substituted for 

the specific requirements of the paragraph.

§27.549 

Fuselage, 

landing gear, 

and rotor pylon 

structures 

Rolled up 

to SI

Summary: This paragraph specifies conditions and values for which the fuselage, 

landing gear, and rotor pylons must be designed by reference to numerous other 

paragraphs. 

Rationale: As in §27.547, Specific conditions and values should be screened with 

respect to the specific risks associated with an unmanned vehicle in an agricultural 

application in rural areas, especially given that the safety issue is limited to rotor system 

integrity under a very narrow set of operating conditions. Thus, the paragraph, like 

§27.547, was relegated to the issue paper.
69

Emergency Landing Conditions

§27.561 

General

Excluded Summary: This paragraph specifies load factors that must be considered in structural 

design to protect rotorcraft occupants during emergency landings.

Rationale: Not UAS relevant. Does not map to a hazard.

§27.562 

Emergency 

landing 

dynamic 

conditions 

Excluded Summary: This paragraph specifies many factors related to occupants seats and 

restraints that must be considered in structural design to protect occupants during 

emergency landings.

Rationale: Not UAS relevant. Does not map to a hazard.

§27.563 

Structural 

ditching 

provisions 

Excluded Summary: This paragraph describes factors that must be considered in structural design 

during emergency landings that take place in water (ditching).

Rationale: Out of ConOps scope.

Fatigue Evaluation

§27.571 

Fatigue 

evaluation of 

flight structure 

Rolled up 

to SI

Summary: This paragraph establishes requirements for the elements of the flight 

structure that must be identified and evaluated with respect to fatigue considerations, 

including rotor system and drive components. The paragraph further specifies 

procedures and measurement techniques that must be used to determine loads and 

stresses and fatigue tolerances. 

Rationale: While fatigue considerations were considered important in ensuring the rotor 

system integrity, the specifics of this paragraph were considered too detailed to be 

applicable as written to an unmanned rotorcraft in a very limited operational 

circumstance. Thus, the requirements of the paragraph were rolled up to SI.

§27.573 

Damage 

Tolerance and 

Fatigue 

Evaluation of 

Composite 

Rotorcraft 

Structures 

Rolled up 

to SI

Summary: This paragraph specifies requirements and methodology for evaluating 

composite rotorcraft structures for with damage tolerance standards.

Rationale: The ConOps requires flying very low over crops. The possibility of 

entrainment of ground debris into the rotor wake and subsequent impingement on 

rotorcraft structure must be considered. The specifics of this paragraph were considered 

too detailed to be applicable as written to an unmanned rotorcraft in a very limited 

operational circumstance. Thus, the requirements of the paragraph were rolled up into 

the more general statement of requirements in the issue paper.

Subpart D—Design and Construction

General

§27.601

Design 

Modified (a) The UAS rotorcraft may have no design 

features or details that experience has 

shown to be hazardous or unreliable. 

(b) For each questionable design detail 

whose failure could adversely affect safety, 

the suitability of each questionable design 

detail and part must be established by tests. 

Rationale: The entire system (i.e., the GCS 

and other components, not just the UA) 

must be free from hazardous features and

details. A feature is hazardous if, during 

operations as described in the ConOps, it 

could lead to death of serious injury of any 

person or lead to a large reduction in safety 

margin. UAS design details that may be 

deemed conventionally questionable, such 

as the unqualified use of commercial-offthe-shelf components, pedigreed sensors 

and actuators etc., must only be considered 

with respect to their safety effects. 

§27.602

Critical Parts

Modified (a) Critical part. A critical part is a part, the 

failure of which could have a catastrophic 

effect upon the rotorcraft UAS, and for 

which critical characteristics have been 

Rationale: A critical part is one whose 

failure results in a catastrophic failure for 

the UAS. Critical parts might be found in

the containment system, ground control 
70

identified which must be controlled to 

ensure the required level of integrity.

(b) If the type design includes critical parts, 

a critical parts list shall be established. 

Procedures shall be established to define 

the critical design characteristics, identify 

processes that affect those characteristics, 

and identify the design change and process 

change controls necessary for showing 

compliance with the quality assurance 

requirements of part 21 of this chapter.

station, receivers, etc. A critical parts list 

should include those parts whose failure is

considered catastrophic, for example 

because it would result in the ejection of 

high energy parts from containment area or 

a fly away event.

§27.603

Materials

As is The suitability and durability of materials 

used for parts, the failure of which could 

adversely affect safety, must—

(a) Be established on the basis of 

experience or tests; 

(b) Meet approved specifications that 

ensure their having the strength and other 

properties assumed in the design data; and 

(c) Take into account the effects of 

environmental conditions, such as 

temperature and humidity, expected in 

service.

Rationale: Only safety critical systems 

need to meet this standard (all other systems 

need not comply and/or degrade gracefully). 

The provision that this only applies “for 

parts, the failure of which could adversely 

affect safety” is part of the Part 27 text. 

This phrase is included elsewhere since it is 

particularly relevant to this G-1U issue 

paper.

§27.605 

Fabrication 

methods 

Rolled up 

to CMS(b) 

and SI

Summary: This paragraph relates primarily to production methods, requiring methods 

that produce consistently sound structures and a test program to substantiate those 

methods. 

Rationale: This requirement is felt to be applicable to control system fabrication as well 

as other structures and so is included in the CMS rollup.

§27.607 

Fasteners

Rolled up 

to CMS(b) 

and SI

Summary: This paragraph establishes a requirement for locking devices for bolts, 

screws, nuts, pins, etc. used in any critical application that could jeopardize safe 

operations. 

Rationale: This paragraph was felt to be particularly applicable to control systems and 

so was rolled up into the CMS Issue Paper to force consideration of fasteners and their 

role in maintaining rotor system integrity.

§27.609

Protection of 

structure

Modified Each part of the structure, whose failure 

could adversely affect safety, must—

(a) Be suitably protected against 

deterioration or loss of strength in service 

due to any cause, including—

(1) Weathering; 

(2) Corrosion; and 

(3) Abrasion; and 

(b) Have provisions for ventilation and 

drainage where necessary to prevent the 

accumulation of corrosive, flammable, or 

noxious fluids.

Rationale: Only parts of the UAS structure 

that affect overall UAS system safety need 

meet this standard. However, parts of the 

system other than the UA might also affect 

safety and thus need to be considered.

Safety considerations should include effects 

on the crew.

§27.610

Lightning and 

static 

electricity 

protection 

Modified (a) The rotorcraft must be protected against 

catastrophic effects from lightning.

(b) For metallic components, compliance 

with paragraph (a) of this section may be 

shown by—

(1) Electrically bonding the components 

Rationale: The ConOps does not allow for 

operations during conditions in which 

lightning occurs.

(a-c) are not applicable as the lightning 

strike hazard is controlled operationally.

(d) is mostly kept because details relevant 
71

properly to the airframe; or

(2) Designing the components so that a 

strike will not endanger the rotorcraft.

(c) For nonmetallic components, 

compliance with paragraph (a) of this 

section may be shown by—

(1) Designing the components to minimize 

the effect of a strike; or

(2) Incorporating acceptable means of 

diverting the resulting electrical current so 

as not to endanger the rotorcraft.

(d) The electrical bonding and protection 

against lightning and static electricity 

must—

(1) Minimize the accumulation of 

electrostatic charge;

(2) Minimize the risk of electric shock to 

crew, passengers, and service and 

maintenance personnel using normal 

precautions;

(3) Provide an electrical return path, under 

both normal and fault conditions, on 

rotorcraft having grounded electrical 

systems; and

(4) Reduce to an acceptable level the 

effects of static electricity on the 

functioning of essential electrical and 

electronic equipment.

to static electricity must be considered. 

Static electricity can electrocute a 

crewmember, so buildup must be mitigated. 

Neither lightning nor passengers need to be 

considered in (d).

§27.611

Inspection 

provisions 

Modified There must be means to allow the close 

examination of each part, whose failure 

could adversely affect safety, that 

requires—

(a) Recurring inspection; 

(b) Adjustment for proper alignment and 

functioning; or 

(c) Lubrication.

Rationale: Only safety-critical UAS parts 

need meet this standard (all other systems 

parts need not comply).

§27.613 

Material 

strength 

properties and 

design values 

Rolled up 

to SI

Summary: This paragraph specifies the materials and structural strength required for the 

vehicle.

Rationale: Material strength would likely be a factor in maintaining rotor system 

integrity. This paragraph was included in the SI roll-up.

§27.619 

Special factors 

Excluded Summary: This paragraph increases the factor of safety prescribed for bearings, fittings 

and castings for parts whose strength is variable, uncertain, or likely to deteriorate in 

service before normal replacement.

Rationale: Secondary hazard. The requirement in §27.602 addresses design 

requirements for critical parts. 

§27.621 

Casting factors 

Rolled up 

to CMS(b) 

and SI

Summary: This paragraph establishes manufacturing, inspection, and testing 

requirements for critical castings. 

Rationale: Since any castings used in the control system would likely be critical to 

maintaining rotor system integrity, this paragraph was included in the CMS rollup.
72

§27.623 

Bearing factors 

Rolled up 

to CMS(b) 

and SI

Summary: This paragraph specifies requirements for parts which have clearances and 

are subjected to pounding or vibration. 

Rationale: Rotorcraft are known to have such forces in their control systems and the 

bearing surfaces are also known to require specific clearances to control friction and 

binding in the system. The requirements of this paragraph were rolled up to CMS(b) and 

SI Issue Papers.

§27.625 

Fitting factors 

Rolled up 

to CMS(b) 

and SI

Summary: This paragraph establishes a fitting factor of 1.15 and specifies the parts to 

which the factor applies if strength is not established in other acceptable ways. 

Rationale: Because the control system requires fitting of parts but the exact fitting 

factor may be different, this requirement was rolled up.

§27.629 

Flutter

As Is Each aerodynamic surface of the rotorcraft 

must be free from flutter under each 

appropriate speed and power condition.

Rationale: Flutter must not impact rotor 

system integrity. 

Rotors

§27.653 

Pressure 

venting and 

drainage of 

rotor blades 

Rolled up 

to SI

Summary: This paragraph establishes requirements for rotor blade pressure relief and 

drainage for rotor blades that are not sealed. 

Rationale: This paragraph relates to rotor system integrity and could be relevant 

depending on rotor blade design.

§27.659 

Mass balance 

Rolled up 

to SI

Summary: This paragraph establishes requirements (1) for rotor mass balance to 

prevent excessive vibration at speeds out to the maximum forward speed and (2) for 

substantiation of the structural integrity of the mass balance. 

Rationale: Rotor mass balance affects structural integrity, but the definitions of 

“excessive” and “maximum forward speed” for a UAS under the ConOps may differ 

from Part 27 rotorcraft. The paragraph was included in the more generalized 

requirements of the SI Issue Paper.

§27.661 

Rotor blade 

clearance

Rolled up 

to SI

Summary: This paragraph establishes a requirement that the rotor blades not contact 

any part of the structure during any operating condition. 

Rationale: While this requirement relates to maintaining rotor system integrity under 

most conditions, there might be exceptions related to autorotations away from the 

operational boundaries where the vehicle could sustain damage or loss without hazard to 

persons or property. The requirement was included in the rollup to allow discussion of 

tailoring the requirement to the specific design and operations of the UAS.

§27.663 

Ground 

resonance 

prevention 

means 

Rolled up 

to SI

Summary: This paragraph establishes requirements on the means incorporated in the 

rotorcraft design to avoid ground resonance and a requirement that failure of any single 

means will not cause ground resonance. 

Rationale: Avoidance of ground resonance was considered an important aspect of 

maintaining rotor system integrity, particularly near (ground) crewmembers involved in 

the servicing the vehicle. The requirements for establishing the reliability of such 

systems, however, might be different for unmanned vehicles than for manned vehicles, 

so the paragraph was rolled up.

Control Systems

§27.671 

General 

Rolled up 

to CMS (a 

and b)

Summary: This paragraph establishes requirements on smoothness of the control 

systems and a requirement that they be designed or marked to minimize probability of 

incorrect assembly. 

Rationale: Requirements for smoothness of the control system are dictated by the 

design and power of the automatic control system and its servos, which must satisfy the 

flight requirements of CMS(a). The design and marking requirements to minimize 

incorrect assembly are covered in CMS(b).
73

§27.672 

Stability 

augmentation, 

automatic, and 

poweroperated 

systems 

Rolled up 

to CMS(a)

Summary: This paragraph requires that any automatic stabilization or automatic control 

systems must be able to continue to a safe landing after any single failure in the system. 

The paragraph further specifies that the controllability and maneuverability 

requirements previously specified continue to be met within a “practical operational 

envelope”. Other parts of the paragraph relate to warning systems and pilot skill and 

strength requirements.

Rationale: Although pilot-related requirements are not applicable under this ConOps, 

the requirements for controllability and maneuverability were rolled up with the 

expectation that the applicant and regulatory authority will determine the applicable 

requirements for the automatic flight control system of the AgR-1.

§27.673 

Primary flight 

control 

Excluded Summary: Defines what a primary flight control is relative to a pilot.

Rationale: Out of ConOps scope. Pilot does not have inner-loop control.

§27.674 

Interconnected 

controls 

Excluded Summary: Ensures that safe flight can continue after a jam or other malfunction of an 

auxiliary interconnected flight control.

Rationale: Out of vehicle scope. AgR-1 does not use interconnected auxiliary controls.

§27.675 

Stops 

Rolled up 

to CMS(b)

Summary: This paragraph specifies that the control system must contain stops that limit 

the range of control motion and conditions that must be considered in setting the stops. 

Rationale: While a UAS will not have traditional pilot controls and thus the need for

stops to limit pilot control inputs, there still exists a requirement to ensure that the 

control system actuators cannot produce commands that would cause a failure condition 

in the control system and thus jeopardize rotor system integrity. This requirement 

generally applies and was included in the CMS(b).

§27.679 

Control system 

locks 

Rolled up 

to CMS(b)

Summary: This paragraph establishes requirements for control system locks if they are 

part of the design. 

Rationale: Although the operational concept would not likely dictate a requirement for 

control system locks, the requirement for ground transportability could possibly dictate a 

requirement and was included in the rollup.

§27.681 

Limit load 

static tests 

Rolled up 

to CMS(b) 

and SI

Summary: This paragraph establishes the conditions under which compliance with 

control system limit loads must be shown. 

Rationale: Since the integrity of the control system is essential to maintaining the 

integrity of the rotor system, this paragraph may be generally applicable and was 

included in the rollup for CMS(b).

§27.683 

Operation tests

Rolled up 

to CMS(b)

Summary: This paragraph specifies that the control system must be free of jamming, 

excessive friction, and excessive deflection when operated from the pilot compartment 

to the loads specified for the system. 

Rationale: While the UAS does not have an on board pilot compartment, the spirit of the 

rule is that the control system be free of the specified characteristics when operated by 

power actuators. What constitutes “excessive” might vary for an automatic control 

system compared with a manual control system and would probably be limited by 

required control system performance.

§27.685 

Control system 

details 

Rolled up 

to CMS(b)

Summary: This paragraph specifies a number of miscellaneous requirements for control 

system functioning to prevent jamming, chafing, and interference from cargo, 

passengers, loose objects or the freezing of moisture. This applies primarily to pulley 

and cable systems. Special design factors for push-pull and cable systems are also 

specified. 

Rationale: The general intent that the control system design should consider jamming, 

chafing and interference applies in general. Applicability of the specific details in the 

paragraph will depend on implementation of the control system.
74

§27.687 

Spring devices 

Rolled up 

to CMS(b)

Summary: This paragraph requires that spring devices whose failure could compromise 

safe flight need to be reliable and must be shown as such by demonstrations simulating 

service conditions. 

Rationale: Failure of spring devices in the control system could result in flutter or other 

unsafe conditions and thus could represent a threat to control system and rotor system 

integrity. The paragraph was rolled up to ensure that the applicant considers the 

requirements on spring devices to the extent they are included in the design.

§27.691

Autorotation 

control 

mechanism 

Modified If autorotation capability is implemented, 

each main rotor blade pitch control 

mechanism must allow rapid entry into 

autorotation after power failure

Rationale: The autorotation function may 

not be required by the ConOps (e.g., max 

altitude restrictions and acceptability of hull 

loss).

§27.695 

Power boost 

and poweroperated 

control system 

Rolled up 

to CMS(b)

Summary: This paragraph specifies requirements for an alternate control system to 

provide continued safe flight in the event of a failure of a power actuator or any of the 

elements supporting the actuator, such as pumps, valves, and lines. The paragraph 

includes requirements on the reliability of mechanical parts and actuators. 

Rationale: The requirements of this paragraph are generally applicable given the use of 

servos in the primary flight control system of the AgR-1, although only to the extent that 

failure to meet the requirements would jeopardize rotor system integrity. The paragraph 

was rolled up in CMS(b) as a consideration in control system design and installation.

Landing Gear

§27.723 

Shock 

absorption 

tests

Excluded Summary: This paragraph describes conditions for executing the required shock 

absorption tests.

Rationale: Secondary hazard.

§27.725 

Limit drop test 

Excluded Summary: This paragraph describes the impulsive load the landing gear is capable of 

withstanding without collapse.

Rationale: Does not map to a hazard.

§27.727 

Reserve energy 

absorption 

drop test

Excluded Summary: This paragraph describes the amount of impact energy the landing gear must 

be capable of absorbing without collapse.

Rationale: Does not map to a hazard.

§27.729 

Retracting 

mechanism

Excluded Summary: This paragraph describes the requirements for retractable landing gear.

Rationale: Does not map to a hazard. This assumes there are no other hazards 

associated with retractable landing gear beyond ground resonance

§27.731 

Wheels

Excluded Summary: This paragraph describes wheel requirements for the landing gear.

Rationale: Does not map to a hazard.

§27.733 

Tires

Excluded Summary: This paragraph describes the performance requirements of the tires in the 

landing gear.

Rationale: Does not map to a hazard.

§27.735 

Brakes

Rolled up 

to CMS(a)

Summary: This paragraph establishes functional requirements for the brakes including 

design requirements related to startup, shutdown, landing, and while parked on a 10 

degree slope.

Rationale: If equipped with a wheel system, this requirement mitigates the hazard of 

the vehicle unintentionally moving under the required conditions. 

§27.737 

Skis

Excluded Summary: This paragraph describes limit loading for landing on skis.

Rationale: Out of ConOps scope.
75

Floats and Hulls

§27.751 

Main float 

buoyancy

Excluded Summary: This paragraph describes buoyancy requirements on the vehicle.

Rationale: Out of ConOps scope.

§27.753 

Main float 

design

Excluded Summary: This paragraph describes design requirements on buoyancy elements.

Rationale: Out of ConOps scope.

§27.755 

Hulls

Excluded Summary: This paragraph describes the buoyancy requirements on the vehicle in the 

case of hull damage.

Rationale: Out of ConOps scope.

Personnel and Cargo Accommodations

§27.771 

Pilot 

compartment

Excluded Summary: This paragraph deals with the accommodations necessary for an onboard 

pilot.

Rationale: Does not map to a hazard.

§27.773 

Pilot 

compartment 

view

Excluded Summary: This paragraph deals with the accommodations necessary for an onboard 

pilot.

Rationale: Does not map to a hazard.

§27.775 

Windshields 

and windows

Excluded Summary: This paragraph deals with the accommodations (windshields and windows) 

necessary for an onboard pilot to see outside of the aircraft.

Rationale: Does not map to a hazard.

§27.777 

Cockpit 

controls

Excluded Summary: This paragraph deals with the accommodations (cockpit controls) necessary 

for an onboard pilot to control the aircraft.

Rationale: Does not map to a hazard.

§27.779 

Motion and 

effect of 

cockpit 

controls

Excluded Summary: This paragraph deals with the accommodations necessary for motion relevant 

to cockpit controls for an onboard pilot.

Rationale: Does not map to a hazard.

§27.783 

Doors

Excluded Summary: This paragraph deals with external doors necessary for onboard persons to 

safely exit the aircraft.

Rationale: Does not map to a hazard.

§27.785 

Seats, berths, 

litters, safety 

belts, and 

harnesses

Excluded Summary: This paragraph deals with the seating accommodations (e.g., seatbelts, seats, 

or harnesses) necessary for onboard persons.

Rationale: Does not map to a hazard.

§27.787 

Cargo and 

baggage 

compartments

Excluded Summary: This paragraph deals with the cargo and baggage compartments to stow 

articles for onboard persons.

Rationale: Does not map to a hazard.

§27.801 

Ditching

Excluded Summary: This paragraph deals with the accommodations necessary for the safety 

onboard persons in the event of ditching.

Rationale: Does not map to a hazard.
76

§27.805 

Flight crew 

emergency 

exits

Excluded Summary: This paragraph deals with the accommodations necessary for emergency 

exits (onboard) for the flight crew.

Rationale: Does not map to a hazard.

§27.807 

Emergency 

exits

Excluded Summary: This paragraph deals with the accommodations necessary for emergency 

exits for onboard passengers.

Rationale: Does not map to a hazard.

§27.831 

Ventilation

Excluded Summary: This paragraph deals with the accommodations necessary for the ventilation 

system to prevent fuel fumes and carbon monoxide from harming onboard persons.

Rationale: Does not map to a hazard.

§27.833 

Heaters

Excluded Summary: This paragraph requires approval of any combustion heaters necessary for the 

accommodation of onboard persons.

Rationale: Does not map to a hazard.

Fire Protection

§27.853 

Compartment 

interiors

Excluded Summary: This paragraph deals with onboard fire protection for compartments used by 

crew or passengers.

Rationale: Does not map to a hazard.

§27.855 

Cargo and 

baggage 

compartments

Excluded Summary: This paragraph deals with onboard fire protection for cargo and baggage 

compartments.

Rationale: Does not map to a hazard.

§27.859 

Heating 

systems

Excluded Summary: This paragraph deals with onboard fire and carbon monoxide protection 

related to heating systems.

Rationale: Does not map to a hazard.

§27.861 

Fire protection 

of structure, 

controls, and 

other parts

Modified Each part of the structure, controls, rotor 

mechanism, and other parts essential to 

preventing loss of containment or ejection 

of high energy parts a controlled landing

that would be affected by powerplant fires 

must be fireproof or protected so they can 

perform their essential functions for at least 

5 minutes under any foreseeable 

powerplant fire conditions.

Rationale: Need fire protection sufficient to 

mitigate safety-critical hazards. The time 

requirement may need further consideration.

§27.863

Flammable 

fluid fire 

protection 

Modified (a) In each area where flammable fluids or 

vapors might escape by leakage of a fluid 

system, there must be means to minimize 

the probability of ignition of the fluids and 

vapors, and the resultant hazards if ignition 

does occur. 

(b) Compliance with paragraph (a) of this 

section must be shown by analysis or tests, 

and the following factors must be 

considered: 

(1) Possible sources and paths of fluid 

leakage, and means of detecting leakage. 

(2) Flammability characteristics of fluids, 

including effects of any combustible or 

absorbing materials. 

(3) Possible ignition sources, including 

electrical faults, overheating of equipment, 

Rationale: The control of the flammable 

fluid hazard is not related to the act of fire

protection for onboard crew and passengers 

of the rotorcraft, but instead centered 

around fire protection for the UAS crew and 

bystanders. Hence, subparagraph (b)(4) 

was kept because it pertains to having 

sufficient means for fire control (equipment, 

access to electrical cutoffs, operational 

procedures etc.) available to UAS crew.

The loss of hull integrity of the rotorcraft 

within the containment region is not a 

hazard, so the rotorcraft structure itself need 

not be protected from flammable fluid 

ignition.
77

and malfunctioning of protective devices. 

(4) Means available for controlling or 

extinguishing a fire, such as stopping flow 

of fluids, shutting down equipment, 

fireproof containment, or use of 

extinguishing agents provided either by the 

type design or through operational 

requirements and provisions. 

(5) Ability of rotorcraft components that 

are critical to safety of flight to withstand 

fire and heat. 

(c) If action by the flight crew is required 

to prevent or counteract a fluid fire (e.g. 

equipment shutdown or actuation of a fire 

extinguisher) quick acting means must be 

provided to alert the crew. 

(d) Each area where flammable fluids or 

vapors might escape by leakage of a fluid 

system must be identified and defined.

External Loads

§27.865 

External loads.

Excluded Summary: This paragraph deals with the requirements for attaching external loads to 

the vehicle.

Rationale: Out of vehicle scope. Secondary hazard. The spray system is assumed to be 

an external load (but not a jettisonable one). 

Miscellaneous

§27.871 

Leveling 

marks

Excluded Summary: This paragraph requires marking in order to level the rotorcraft to affect 

stability (for loading conditions)

Rationale: Does not map to a hazard.

§27.873 

Ballast 

provisions

Excluded Summary: This paragraph requires preventative measures so that ballast does not shift 

in flight

Rationale: Does not map to a hazard.

Subpart E—Powerplant

General

§27.901

Installation 

Excluded Summary: This paragraph defines powerplant installation and establishes high-level 

safety requirements for continued operations between inspections/overhauls, electrical 

connections, accessibility, etc., and requires installation in accordance with Part 33 

requirements.

Rationale: Out of vehicle scope. Secondary hazard. The high-level safety requirements 

were, in part, established to provide safety for onboard occupants, which would not 

apply to a UAS. Use of a Part 33 certified engine is not required, and thus Part 33 

installation requirements would not apply. Minimum safety requirements relevant to the 

UAS powerplant are covered adequately in other paragraphs and the PPS rollup.

§27.903

Engines

Modified (a) Engine type certification. Each engine 

must have an approved type certificate. 

Reciprocating engines for use in 

helicopters must be qualified in accordance 

with §33.49(d) of this chapter or be 

otherwise approved for the intended usage. 

(b) Engine or drive system cooling fan 

blade protection. (1) If an engine or rotor 

Rationale: Subparagraph (a) is deleted 

because a certified engine is not required, as 

hull loss inside the containment region is 

not catastrophic.

Subparagraph (b) is deleted because the 

unmanned rotorcraft does not need to be 

protected if a fan blade fails, as hull loss in 

the containment area is not catastrophic.
78

drive system cooling fan is installed, there 

must be a means to protect the rotorcraft 

and allow a safe landing if a fan blade fails. 

This must be shown by showing that—

(i) The fan blades are contained in case of 

failure; 

(ii) Each fan is located so that a failure will 

not jeopardize safety; or 

(iii) Each fan blade can withstand an 

ultimate load of 1.5 times the centrifugal 

force resulting from operation limited by 

the following: 

(A) For fans driven directly by the 

engine—

(1) The terminal engine r.p.m. under 

uncontrolled conditions; or 

(2) An overspeed limiting device. 

(B) For fans driven by the rotor drive 

system, the maximum rotor drive system 

rotational speed to be expected in service, 

including transients. 

(2) Unless a fatigue evaluation under 

§27.571 is conducted, it must be shown 

that cooling fan blades are not operating at 

resonant conditions within the operating 

limits of the rotorcraft. 

(c) Turbine engine installation. For turbine 

engine installations, the powerplant 

systems associated with engine control 

devices, systems, and instrumentation must 

be designed to give reasonable assurance 

that those engine operating limitations that 

adversely affect turbine rotor structural 

integrity will not be exceeded in service.

(d) Restart capability: A means to restart 

any engine in flight must be provided.

(1) Except for the in-flight shutdown of all 

engines, engine restart capability must be 

demonstrated throughout a flight envelope 

for the rotorcraft.

(2) Following the in-flight shutdown of all 

engines, in-flight engine restart capability 

must be provided.

Subparagraph (c) is kept because it helps 

mitigate hazards associated with high 

energy parts exiting the containment area. 

Subparagraph (d) is deleted because restart 

capability is not required as hull loss in the 

containment area is not catastrophic.
79

§27.907 

Engine 

vibration

Modified (a) Each engine must be installed to 

prevent the harmful vibration of any part of 

the engine or rotorcraft. 

(b) The addition of the rotor and the rotor 

drive system to the engine may not subject 

the principal rotating parts of the engine to 

excessive vibration stresses. This must be 

shown by a vibration investigation. 

(c) No part of the rotor drive system may 

be subjected to excessive vibration 

stresses.

Rationale: Subparagraphs (a) and (b) were 

deleted because engine integrity itself is not 

needed.

Subparagraph (c) was kept because rotor 

drive integrity must be protected from 

destructive vibration, as this may lead to the 

hazard of high energy parts being ejected 

from the containment area.

Rotor Drive System

§27.917

Design 

Modified (a) Each rotor drive system must 

incorporate a unit for each engine to 

automatically disengage that engine from 

the main and auxiliary rotors if that engine 

fails. 

(b) Each rotor drive system must be 

arranged so that each rotor necessary for 

control in autorotation will continue to be 

driven by the main rotors after 

disengagement of the engine from the main 

and auxiliary rotors. 

(c) If a torque limiting device is used in the 

rotor drive system, it must be located so as 

to allow continued control of the rotorcraft 

when the device is operating.

(bd) The rotor drive system includes any 

part necessary to transmit power from the 

engines to the rotor hubs. This includes 

gear boxes, shafting, universal joints, 

couplings, rotor brake assemblies, clutches, 

supporting bearings for shafting, any 

attendant accessory pads or drives, and any 

cooling fans that are a part of, attached to, 

or mounted on the rotor drive system.

Rationale: Subparagraphs (a) and (d) are 

kept because rotors must be protected from 

engine seizures/failures to prevent high 

energy parts from being ejected from the 

containment area.

Subparagraphs (b) and (c) were deleted 

because neither autorotation nor a torque 

limiting device are required functions, and

this hazard may be mitigated via operational 

means (e.g., limited altitude).

§27.921 

Rotor brake

As is If there is a means to control the rotation of 

the rotor drive system independently of the 

engine, any limitations on the use of that 

means must be specified, and the control 

for that means must be guarded to prevent 

inadvertent operation.

Rationale: A rotor brake engaging

inadvertently could lead to rotor integrity 

being compromised.

§27.923 

Rotor drive 

system and 

control 

mechanism 

tests 

Excluded Summary: This paragraph establishes specific hourly or cycle requirements for testing 

of rotor systems and associated components.

Rationale: Multiengine requirements of this paragraph are Out of vehicle scope. Other 

testing requirements would not be directly applicable to the AgR-1 and ConOps given 

that hull loss is acceptable under some circumstances. 
80

§27.927 

Additional 

tests

Excluded Summary: This paragraph defines additional rotor system tests that apply if the torque 

going from the engine to the transmission is not under direct pilot control and other 

conditions specific to multi-engine turbine installations.

Rationale: Out of vehicle scope. Mitigated by other regulation. This paragraph was 

excluded because multiple engines are out of scope and additional tests are 

unnecessarily burdensome for the operational context.

§27.931

Shafting 

critical speed

As is (a) The critical speeds of any shafting must 

be determined by demonstration except 

that analytical methods may be used if 

reliable methods of analysis are available 

for the particular design. 

(b) If any critical speed lies within, or close 

to, the operating ranges for idling, power 

on, and autorotative conditions, the stresses 

occurring at that speed must be within safe 

limits. This must be shown by tests. 

(c) If analytical methods are used and show 

that no critical speed lies within the 

permissible operating ranges, the margins 

between the calculated critical speeds and 

the limits of the allowable operating ranges 

must be adequate to allow for possible 

variations between the computed and 

actual values.

Rationale: This requirement is important to 

maintain rotor drive shaft system integrity. 

§27.935

Shafting joints

As is Each universal joint, slip joint, and other 

shafting joints whose lubrication is 

necessary for operation must have 

provision for lubrication.

Rationale: This requirement is important to 

maintain rotor drive shaft system integrity.

§27.939 

Turbine engine 

operating 

characteristics

Modified (a) Turbine engine operating characteristics 

must be investigated in flight to determine 

that no adverse characteristics (such as 

stall, surge, or flameout) are present, to a 

hazardous degree, during normal and 

emergency operation within the range of 

operating limitations of the rotorcraft and 

of the engine.

(b) The turbine engine air inlet system may 

not, as a result of airflow distortion during 

normal operation, cause vibration harmful 

to the engine.

(c) For governor-controlled engines, it 

must be shown that there exists no 

hazardous torsional instability of the drive 

system associated with critical 

combinations of power, rotational speed, 

and control displacement.

Rationale: Subparagraphs (a) and (b) were 

excluded because they do not relate to a 

hazard. However, subparagraph (c) is 

relevant because the hazard of over-torque 

of the transmission/rotor system from loss 

of governor control should be mitigated to 

prevent loss of rotor system integrity.

Fuel System

§27.951

General 

Excluded Summary: This paragraph establishes requirements for fuel system design and 

installation to ensure continued operation of the engine.

Rationale: Mitigated by other regulation. 
81

§27.952 

Fuel system 

crash 

resistance 

Excluded Summary: This paragraph establishes design and testing requirements for fuel tanks.

Rationale: Secondary hazard. The fuel tank does not need to meet crashworthiness 

requirements for manned vehicles.

§27.953 

Fuel system 

independence 

Excluded Summary: This paragraph establishes requirements for single and multiple fuel tanks in 

multiengine rotorcraft.

Rationale: Out of vehicle scope.

§27.954 

Fuel system 

lightning 

protection 

Excluded Summary: This paragraph establishes requirements for fuel system protection from 

lightning strikes.

Rationale: Out of ConOps scope. The ConOps assumes no operations in thunderstorms. 

Risk associated with the possibility of a lightning strike on the ground and potential 

harm to the crew should be considered in operational procedures.

§27.955 

Fuel flow 

Excluded Summary: This paragraph establishes requirements to ensure stable fuel flow to the 

engine.

Rationale: Mitigated by other regulation.

§27.959 

Unusable fuel 

supply 

Excluded Summary: This paragraph establishes requirements to determine minimum usable fuel.

Rationale: Mitigated by other regulation.

§27.961 

Fuel system 

hot weather 

operation 

Excluded Summary: This paragraph establishes requirements for fuel system operations at fuel 

temperature up to 110 deg. F.

Rationale: Mitigated by other regulation.

§27.963 

Fuel tanks: 

general 

Rolled-up 

to PPS

Summary: This paragraph establishes general requirements for fuel tank design, 

construction and installation, including such features as baffling, vibration resistance, 

inertia and fuel loading structural requirements, and ventilation requirements. 

Rationale: These requirements are necessary in some form to mitigate a possible 

explosion hazard should fuel escape from the fuel tank during operations. The 

requirements were rolled up into a general statement that the applicant determines safety 

critical conditions including consideration of fuel tank design, construction, and 

installation.

§27.965 

Fuel tank tests 

Rolled-up 

to PPS

Summary: This paragraph specifies conditions under which fuel tanks must be tested to 

show structural integrity, including pressures, times, vibrations, etc. 

Rationale: As in §27.963, this paragraph relates to ensuring explosion resistance of the 

fuel tank installation and was rolled up into the generalized requirements for the 

powerplant and supporting systems.

§27.967 

Fuel tank 

installation 

Rolled up 

to PPS

Summary: This paragraph requires that fuel tanks be installed in such a way that they 

are properly supported and provided adequate protection against expected loads. 

Rationale: This paragraph was rolled up for the same reasons as §27.963 and §27.965.

§27.969

Fuel tank 

expansion 

space

As is Each fuel tank or each group of fuel tanks 

with interconnected vent systems must 

have an expansion space of not less than 2 

percent of the tank capacity. It must be 

impossible to fill the fuel tank expansion 

space inadvertently with the rotorcraft in 

the normal ground attitude.

Rationale: Fuel tank should not be 

overfilled, because this might lead to 

possible inadvertent ignition.

§27.971 

Fuel tank sump 

Excluded Summary: This paragraph establishes requirements for a drainable fuel sump and sets 

minimum size to minimize possibility of water or sediment in the fuel which could lead 

to engine malfunction.

Rationale: Mitigated by other regulation.
82

§27.973

Fuel tank filler 

connection 

Modified (a) Each fuel tank filler connection must 

prevent the entrance of fuel into any part of 

the rotorcraft other than the tank itself 

during normal operations and must be 

crash resistant during a survivable impact 

in accordance with §27.952(c). In 

addition—

(1) Each filler must be marked as 

prescribed in §27.1557(c)(1);

(2) Each recessed filler connection that can 

retain any appreciable quantity of fuel must 

have a drain that discharges clear of the 

entire rotorcraft; and

(3) Each filler cap must provide a fuel-tight 

seal under the fluid pressure expected in 

normal operation and in a survivable 

impact.

(b) Each filler cap or filler cap cover must 

warn when the cap is not fully locked or 

seated on the filler connection.

Rationale: Fuel must stay in the fuel tank to 

avoid possible inadvertent ignition. This

protects the ground crew (e.g., when the 

rotorcraft is landing or taking off). Fuel 

tank filler connections need not preserve 

hull integrity during a crash because the fuel 

system itself is not required to be crash 

resistant. 

Subparagraph (3) was kept because fuel 

vapors leaking from a loose or faulty fuel 

cap could be an inflight or ground fire or 

explosion hazard. Thus the filler cap should 

be required to provide a fuel-tight seal.

Subparagraph (b) was kept because ground 

crew must be warned if the filler cap is not 

properly locked or seated on the filler 

connection, in order to preserve ground 

crew safety.

§27.975

Fuel tank vents 

Modified (a) Each fuel tank must be vented from the 

top part of the expansion space so that 

venting is effective under all normal flight 

conditions. Each vent must minimize the 

probability of stoppage by dirt or ice. 

(b) The venting system must be designed to 

minimize spillage of fuel through the vents 

to an ignition source in the event of a 

rollover during landing or ground 

operation, or a survivable impact.

Rationale: Venting is required to preserve 

ground crew safety. Design for survivable 

impact is not necessary because there are no 

humans on board.

§27.977 

Fuel tank 

outlet

Excluded Summary: This paragraph establishes requirements for fuel outlets and strainers that 

relate to maintaining fuel flow to the engine.

Rationale: Secondary hazard.

Fuel System Components

§27.991 

Fuel pumps

Excluded Summary: This paragraph establishes failure conditions that must not jeopardize 

compliance with §27.955.

Rationale: Mitigated by other regulation. The requirements of §27.955 were also 

excluded.

§27.993 

Fuel system 

lines and 

fittings

Rolled up 

to PPS

Summary: This paragraph sets requirements for fuel lines and fittings that safely 

accommodate high temperatures, vibration, and relative motion of components. 

Rationale: Failure to comply with the spirit of these requirements in some form could 

result in a fuel system explosion hazard, but the requirement as written might be too 

restrictive for an unmanned system design that could tolerate hull losses under some 

conditions. Thus, the requirement was rolled up as part of the more general requirements 

for the powerplant and supporting systems.
83

§27.995 

Fuel valves

Rolled up 

to PPS

Summary: This paragraph establishes requirements for the locations, responsiveness, 

and controls for fuel valves. 

Rationale: As in §27.993, failure to comply with the spirit of these requirements in 

some form could result in a fuel system explosion hazard, but the requirement as written 

might be too restrictive for an unmanned system design that could tolerate hull losses 

under some conditions. The requirement was rolled up under the more general 

requirements of the powerplant and supporting systems.

§27.997 

Fuel strainer or 

filter

Excluded 

except for 

(c), which 

is rolled 

up to PPS

Summary: This paragraph establishes requirements for fuel strainers and filters. 

Subparagraph (c) establishes requirements for structural mounting of any fuel strainer or 

filter installed. 

Rationale: Failure of the fuel filter/strainer mounting (if installed) could lead to a failure 

to contain fuel within the fuel system and an explosion hazard. Subparagraph (c) was 

rolled up into PPS.

§27.999 

Fuel system 

drains.

Excluded 

except for 

(b)(2),

which is

rolled up 

to PPS

Summary: This paragraph establishes requirements on fuel system drains. 

Subparagraph (b)(2) establishes requirements for positive closure of fuel system drains.

Rationale: Since leaking fuel from a fuel system drain could represent an explosion 

hazard, this subparagraph was rolled up to PPS for consideration during powerplant and 

supporting systems design.

Oil System

§27.1011 

Engines: 

General

Excluded Summary: This paragraph establishes design requirements for engine oil system(s) that 

ensure adequate oil supply to the engine under continuous operations.

Rationale: Mitigated by other regulation. 

§27.1013 

Oil tanks

Rolled up 

to PPS

Summary: This paragraph establishes general requirements for oil tank design, 

construction and installation. 

Rationale: These requirements may be necessary in some form to mitigate a possible 

explosion hazard should oil escape from the oil tank during operations. The 

requirements were rolled up into the general requirements of the PPS Issue Paper.

§27.1015 

Oil tank tests

Rolled up 

to PPS

Summary: This paragraph specifies conditions under which oil tanks must be tested to 

show structural integrity. 

Rationale: As in §27.965 for fuel tank testing, this paragraph was considered to relate to 

ensuring explosion resistance of the oil tank installation and was rolled up into the 

generalized requirements for the powerplant and supporting systems.

§27.1017 

Oil lines and 

fittings

Rolled up 

to PPS

Summary: This paragraph sets requirements for oil lines and fittings that safely 

accommodate high temperatures, vibration and relative motion of components. 

Rationale: Similar to the reasoning for §27.997 for fuel system lines and fittings, failure 

to comply with the spirit of these requirements in some form could result in an oil 

system explosion hazard. Thus, this requirement was rolled up as part of the more 

general requirements for the powerplant and supporting systems.

§27.1019 

Oil strainer or 

filter

Excluded Summary: This paragraph establishes requirements for oil strainers, filters, and 

bypasses that ensure uninterrupted flow of oil to the engine.

Rationale: Mitigated by other regulation. 

§27.1021 

Oil system 

drains

Rolled up 

to PPS

Summary: Similar to the requirements of §27.999 for fuel system drains, this 

requirement establishes requirements for positive closure of oil system drains. 

Rationale: Since leaking oil from an oil system drain could represent an explosion 

hazard, this subparagraph was rolled up to PPS for consideration during powerplant and 

supporting systems design.
84

§27.1027

Transmission 

and gearboxes 

Modified (a) The lubrication system for components 

of the rotor drive system that require 

continuous lubrication must be sufficiently 

independent of the lubrication systems of 

the engine(s) to ensure lubrication during 

autorotation.

(b) Pressure lubrication systems for 

transmissions and gearboxes must comply 

with the engine oil system requirements of 

§§27.1013 (except paragraph (c)), 27.1015, 

27.1017, 27.1021, and 27.1337(d). 

(c) Each pressure lubrication system must 

have an oil strainer or filter through which 

all of the lubricant flows and must—

(1) Be designed to remove from the 

lubricant any contaminant which may 

damage transmission and drive system 

components or impede the flow of 

lubricant to a hazardous degree; 

(2) Be equipped with a means to indicate 

collection of contaminants on the filter or 

strainer at or before opening of the bypass 

required by paragraph (c)(3) of this 

section; and 

(3) Be equipped with a bypass constructed 

and installed so that—

(i) The lubricant will flow at the normal 

rate through the rest of the system with the 

strainer or filter completely blocked; and 

(ii) The release of collected contaminants 

is minimized by appropriate location of the 

bypass to ensure that collected 

contaminants are not in the bypass 

flowpath. 

(d) For each lubricant tank or sump outlet 

supplying lubrication to rotor drive systems 

and rotor drive system components, a 

screen must be provided to prevent 

entrance into the lubrication system of any 

object that might obstruct the flow of 

lubricant from the outlet to the filter 

required by paragraph (c) of this section. 

The requirements of paragraph (c) do not 

apply to screens installed at lubricant tank 

or sump outlets. 

(e) Splash-type lubrication systems for 

rotor drive system gearboxes must comply 

with §§27.1021 and 27.1337(d).

Rationale: Subparagraph (a) was kept 

because lubrication of the rotor drive 

system must continue independently of 

engine lubrication system in order to 

maintain rotor drive system integrity and 

prevent high energy parts from exiting the 

containment area.

Other than this, lubrication of the 

transmission and gearboxes need not be 

required to maintain hull integrity.
85

Cooling

§27.1041 

General

Rolled up 

to PPS

Summary: This paragraph establishes requirements that the cooling system be capable 

of maintaining the temperatures of powerplant components, including rotor system 

components, within established temperature limits under critical surface and flight 

operating conditions. 

Rationale: Since compliance with the general requirements of this paragraph could 

affect rotor system integrity the requirement was rolled up for consideration in the 

generalized requirements of the PPS Issue Paper.

§27.1043 

Cooling tests

Excluded Summary: Along with §27.1045, this paragraph establishes conditions and requirements 

for conducting cooling tests on engines.

Rationale: Specific tests for cooling are excluded in deference to the general proof of 

compliance requirements in §27.21.

§27.1045 

Cooling test 

procedures

Excluded Summary: Along with §27.1043, this paragraph establishes conditions and requirements 

for conducting cooling tests on engines.

Rationale: Specific test procedures for cooling are excluded in deference to the general 

proof of compliance requirements in §27.21.

Induction System

§27.1091 

Air induction

Rolled up 

to PPS

Summary: This paragraph establishes requirements for air induction systems. In 

particular, if fuel can accumulate in the system, the system must have drains that 

discharge fuel clear of the rotorcraft and out of the path of exhaust flames. Additionally, 

for turbine powered rotorcraft, the paragraph requires that there must be means to 

prevent hazardous quantities of fuel leakage or overflow from drains. 

Rationale: Since compliance with some of the provisions of this paragraph could relate 

to the mitigation of an explosion hazard, the requirement was rolled up into the 

generalized requirements of the PPS Issue Paper.

§27.1093 

Induction 

system icing 

protection

Excluded Summary: This paragraph establishes induction icing requirements for reciprocating 

and turbine engines and test conditions for demonstrating compliance. Preventing 

induction icing helps prevent damage to the engine and loss of performance. 

Rationale: Secondary hazard. For this application, damage to engine and loss of 

performance may be acceptable under some conditions.

Exhaust System

§27.1121 

General

Rolled up 

to PPS

Summary: This paragraph establishes requirements for the design and installation of the 

rotorcraft exhaust system to prevent ignition of flammable fluids or vapors and 

accommodate vibration, expansion, and other physical characteristics of the rotorcraft 

environment. 

Rationale: The requirements are applicable, but only to mitigate hazards to 

crewmembers during servicing and loading operations. The requirement was rolled up 

into the general requirements to PPS.

§27.1123 

Exhaust piping

Rolled up 

to PPS

Summary: This paragraph establishes requirements for exhaust system design, 

including requirements that the exhaust system must prevent local hot spots and exhaust 

gases must discharge clear of fuel system components and drains. The paragraph also 

requires that exhaust system parts with a surface hot enough to ignite flammable fluids 

or vapors must be located or shielded so that leakage from any system carrying 

flammable fluids or vapors will not result in a fire. 

Rationale: Since this paragraph relates to design features that could prevent explosions,

it was rolled up under the generalized requirements of the PPS Issue Paper.
86

Powerplant Controls and Accessories

§27.1141 

Powerplant 

controls: 

general

Excluded 

except for 

(d) and 

(e), which 

are rolled

up to PPS

Summary: This paragraph establishes requirements for design and operation of 

powerplant controls to ensure continued safe operations.

Rationale: Subparagraph (d) is rolled up because verification of fuel valve position can 

be relevant to the pilot’s safety roll. Subparagraph (e) is rolled up to ensure that loss of 

governor control for a turbine engine cannot jeopardize transmission or rotor system 

integrity due to over-torque.

§27.1143 

Engine 

controls

Excluded Summary: This paragraph establishes design requirements for fuel shutoffs and controls 

for multiple engines.

Rationale: Out of vehicle scope.

§27.1145 

Ignition 

switches

Excluded Summary: This paragraph establishes design requirements to prevent inadvertent

activation of ignition switches and gang operation of multiple ignition switches.

Rationale: Out of vehicle scope.

§27.1147

Mixture 

controls

Excluded Summary: This paragraph establishes requirements to be able to control mixtures for 

multiple engines both separately and together.

Rationale: Out of vehicle scope.

§27.1151 

Rotor brake 

controls

Rolled (a) 

up to 

CMS(a) 

and SI

Summary: Subparagraph (a) requires that it must be impossible to apply the rotor brake 

inadvertently in flight and that crew notification occur if a rotor brake is not released 

before takeoff

Rationale: Inadvertent application of the rotor brake in flight while torque is being 

applied to the rotor would be a significant hazard to rotor system integrity. Thus, 

subparagraph (a) is a requirement on the design of the control system and is rolled up. 

Subparagraph (b) is excluded because a warning system is not required in the ground 

control station.

§27.1163 

Powerplant 

accessories

Rolled up 

to PPS

Summary: This paragraph establishes requirements for mounting accessories to prevent 

damage to the engine or dragging on rotor system.

Rationale: Requirements related to engine protection are not applicable. Subparagraph 

(b) establishes accessory drive requirements that relate to protecting the transmission 

and rotor system from excessive accessory drive loads. This requirement is rolled up.

Powerplant Fire Protection

§27.1183 

Lines, fittings, 

and 

components

Rolled up 

to PPS

Summary: This paragraph establishes requirements for fire resistance and fire proofing 

for fuel lines, fittings, and components. These requirements relate directly to preventing 

onboard fires and/or explosions.

Rationale: The requirements as written may be too specific for an unmanned vehicle 

where hull losses can be tolerated under some conditions, so the requirements were 

rolled up into the more general language of the issue paper.

§27.1185 

Flammable 

fluids

Rolled up 

to PPS

Summary: This paragraph establishes design and installation requirements for firewalls, 

fuel tanks, and fuel system components in areas where flammable fluids are present. 

Rationale: The requirements as written may be too specific for an unmanned vehicle 

where hull losses can be tolerated under some conditions, so the requirements were 

rolled up into the more general language of the issue paper.

§27.1187 

Ventilation and 

drainage

Rolled up 

to PPS

Summary: This paragraph establishes requirements for ventilation and drainage for any 

compartment that contains part of the powerplant installation so as not to create a fire 

hazard. 

Rationale: The details of the paragraph were considered to be too specific for an 

unmanned aircraft, but there still exists a requirement to protect crew when servicing the 

helicopter. Lack of compliance with the spirit of the paragraph could create an 

explosion hazard, so the specific requirements of this paragraph were rolled up into the 

more general language of the issue paper.
87

§27.1189 

Shutoff means

Rolled up 

to PPS

Summary: This paragraph establishes requirements for a means to shut off each line 

carrying flammable fluids into the engine compartment, with a number of exceptions 

listed. 

Rationale: The details of the paragraph were considered too specific for an unmanned 

aircraft, but a lack of compliance with the spirit of this paragraph could present a hazard 

to crew when servicing the helicopter. The specific requirements of this paragraph were 

rolled up into the more general language of the issue paper.

§27.1191 

Firewalls

Rolled up 

to PPS

Summary: This paragraph establishes requirements for firewalls, or equivalents, to 

protect personnel compartments, structures, controls, rotor mechanisms, etc. 

Rationale: While there are no personnel compartments in the UAS to protect, the 

destruction of systems that could lead to a loss of rotor system integrity were considered 

relevant. The details of the paragraph were considered too specific for an unmanned 

aircraft, so the specific requirements of this paragraph were rolled up into the more 

general language of the issue paper.

§27.1193 

Cowling and 

engine 

compartment 

covering

Rolled up 

to PPS and 

SI

Summary: This paragraph establishes requirements for engine compartment covers that 

minimize fire hazards and protect rotor system components in the event of structural or 

mechanical failure of the normal retention means. 

Rationale: The requirements of the paragraph were considered relevant to protecting the 

integrity of the rotor system and relevant to protecting UAS crew during servicing. The 

paragraph was rolled up into the requirements of the issue paper.

§27.1194 

Other surfaces

Excluded Summary: This paragraph requires fire resistance on surfaces aft of the engine 

compartment.

Rationale: Does not map to a hazard. 

§27.1195 

Fire detector

systems

Excluded Summary: This paragraph requires fire detectors in engine compartments that cannot be 

readily seen by the pilot.

Rationale: Does not map to a hazard. Fire detection and warning systems are not 

required because engine fire is not a primary hazard.

Subpart F—Equipment

General

§27.1301

Function and 

Installation 

Modified Each item of installed equipment, whose 

failure could adversely affect safety,

must—

(a) Be of a kind and design appropriate to 

its intended function; 

(b) Be labeled as to its identification, 

function, or operating limitations, or any 

applicable combination of these factors; 

(c) Be installed according to limitations 

specified for that equipment; and 

(d) Function properly when installed

Rationale: Since loss of vehicle may not 

have safety implications, this requirement is 

limited to only those pieces of equipment 

whose failure would affect safety.

§27.1303

Flight and 

navigation 

instruments

Modified The applicant must demonstrate that 

sufficient information is provided to the 

pilot to monitor and control the flight path 

of the rotorcraft within the approved 

operational envelope.

The following are the required flight and 

navigation instruments: 

(a) An airspeed indicator. 

(b) An altimeter. 

(c) A magnetic direction indicator.

Rationale: The original requirements 

presuppose that a pilot will have the ability 

to “hand-fly” the rotorcraft. This mode is 

not available with the operating limits of the 

AgR-1. The requirement is rewritten to 

ensure that sufficient information is 

provided to the pilot to monitor and control 

the flight path. We expect that the dominant 

role of the pilot is to monitor and not 

control the flight path.
88

§27.1305

Powerplant 

limitations 

Modified The following are the required powerplant 

instruments: 

(a) A carburetor air temperature indicator, 

for each engine having a preheater that can 

provide a heat rise in excess of 60 °F. 

(b) A cylinder head temperature indicator, 

for each—

(1) Air cooled engine; 

(2) Rotorcraft with cooling shutters; and 

(3) Rotorcraft for which compliance with 

§27.1043 is shown in any condition other 

than the most critical flight condition with 

respect to cooling. 

(c) A fuel pressure indicator, for each 

pump-fed engine. 

(d) A fuel quantity indicator, for each fuel 

tank.

(e) A manifold pressure indicator, for each 

altitude engine.

(af) An oil temperature warning device to 

indicate when the temperature exceeds a 

safe value in each main rotor drive gearbox 

(including any gearboxes essential to rotor 

phasing) having an oil system independent 

of the engine oil system. 

(bg) An oil pressure warning device to 

indicate when the pressure falls below a 

safe value in each pressure-lubricated main 

rotor drive gearbox (including any 

gearboxes essential to rotor phasing) 

having an oil system independent of the 

engine oil system. 

(ch) An oil pressure indicator for each 

engine. 

(di) An oil quantity indicator for each oil 

tank. 

(ej) An oil temperature indicator for each 

engine. 

(fk) At least one tachometer to indicate the 

r.p.m. of each engine and, as applicable—

(1) The r.p.m. of the single main rotor; 

(2) The common r.p.m. of any main rotors 

whose speeds cannot vary appreciably with 

respect to each other; or 

(3) The r.p.m. of each main rotor whose 

speed can vary appreciably with respect to 

that of another main rotor. 

(l) A low fuel warning device for each fuel 

tank which feeds an engine. This device 

must—

(1) Provide a warning to the flightcrew 

when approximately 10 minutes of usable 

fuel remains in the tank; and 

Rationale: Subparagraphs (a-e) were 

removed because they are not relevant to 

the turbine engine on the AgR-1. 

Subparagraphs (f-k,n,r,v) were retained 

since these conditions can result in 

structural failure of the engine, which 

relates to the rotor system integrity hazard. 

Subparagraphs (l-q,s) were removed 

because these requirements were provided 

to avoid in-flight engine shutdowns. The 

designated operation does not consider an 

in-flight engine shutdown a hazard. 
89

(2) Be independent of the normal fuel 

quantity indicating system. 

(m) Means to indicate to the flightcrew the 

failure of any fuel pump installed to show 

compliance with §27.955.

(gn) A gas temperature indicator for each 

turbine engine. 

(o) Means to enable the pilot to determine 

the torque of each turboshaft engine, if a 

torque limitation is established for that 

engine under §27.1521(e). 

(p) For each turbine engine, an indicator to 

indicate the functioning of the powerplant 

ice protection system. 

(q) An indicator for the fuel filter required 

by §27.997 to indicate the occurrence of 

contamination of the filter at the degree 

established by the applicant in compliance 

with §27.955.

(hr) For each turbine engine, a warning 

means for the oil strainer or filter required 

by §27.1019, if it has no bypass, to warn 

the pilot of the occurrence of 

contamination of the strainer or filter 

before it reaches the capacity established in 

accordance with §27.1019(a)(2). 

(s) An indicator to indicate the functioning 

of any selectable or controllable heater 

used to prevent ice clogging of fuel system 

components.

(t) For rotorcraft for which a 30-second/2-

minute OEI power rating is requested, a 

means must be provided to alert the pilot 

when the engine is at the 30-second and the 

2-minute OEI power levels, when the event 

begins, and when the time interval expires.

(u) For each turbine engine utilizing 30-

second/2-minute OEI power, a device or 

system must be provided for use by ground 

personnel which—

(1) Automatically records each usage and 

duration of power at the 30-second and 2-

minute OEI levels;

(2) Permits retrieval of the recorded data;

(3) Can be reset only by ground 

maintenance personnel; and

(4) Has a means to verify proper operation 

of the system or device.

(iv) Warning or caution devices to signal to 

the flight crew when ferromagnetic 

particles are detected by the chip detector 

required by §27.1337(e).
90

§27.1307 

Miscellaneous 

equipment 

Modified The following is the required

miscellaneous equipment if its whose 

failure could adversely affect safety: 

(a) An approved seat for each occupant. 

(b) An approved safety belt for each 

occupant.

(ac) A master switch arrangement. 

(bd) An adequate source of electrical 

energy, where electrical energy is 

necessary for operation of the rotorcraft. 

(ce) Electrical protective devices for those 

items with safety effects.

Rationale: This miscellaneous equipment is 

only required if its failure would affect 

safety. Since there are no vehicle occupants, 

there is no need for seats or seat belts. 

Ground control station operators are not 

located in moving vehicles. Electrical 

protective devices (e.g., fuses) are required 

to protect safety-critical systems. Electrical 

protection devices might benefit other 

electrical devices (e.g., spray equipment) 

but are not required for the rotorcraft to be 

airworthy.

§27.1309

Equipment, 

systems, and 

installations 

Modified (a) The equipment, systems, and 

installations whose functioning is required 

by this G-1U Issue Paper by this 

subchapter must be designed and installed 

to ensure that they perform their intended 

functions under any foreseeable operating 

condition. 

(b) The equipment, systems, and 

installations of a multiengine rotorcraft 

must be designed to prevent hazards to the 

rotorcraft in the event of a probable 

malfunction or failure.

(c) The equipment, systems, and 

installations of single-engine rotorcraft 

must be designed to minimize hazards to 

the rotorcraft in the event of a probable 

malfunction or failure.

Rationale: Subparagraphs (a) and (c) apply. 

Subparagraph (b) was deleted because 

multiengine rotorcraft are beyond the scope 

of this issue paper.

§27.1316 

Electrical and 

electronic 

system 

lightning 

protection

Excluded Summary: This paragraph requires electronic components to continue to function 

correctly in the presence of lightning.

Rationale: Out of ConOps scope.

§27.1317

High-intensity 

Radiated 

Fields 

Protection

Modified (a) Except as provided in paragraph (d) of 

this section, Each electrical and electronic 

system that performs a function whose 

failure could adversely affect safety would 

prevent the continued safe flight and 

landing of the rotorcraft must be designed 

and installed so that they comply with 

HIRF considerations (TBD) determined to 

affect UAS.

(1) The function is not adversely affected 

during and after the time the rotorcraft is 

exposed to HIRF environment I, as 

described in appendix D to this part;

(2) The system automatically recovers 

normal operation of that function, in a 

timely manner, after the rotorcraft is 

exposed to HIRF environment I, as 

described in appendix D to this part, unless 

Rationale: The text in subparagraph (a) was 

generalized to make clear that any HIRFinduced effects that could cause safety 

issues must be mitigated; however, the 

expected level of HIRF environmental 

conditions is not known at this time. 

Subparagraphs (a)(1-4), (b), (c), and (d) 

were excluded for this reason.
91

this conflicts with other operational or 

functional requirements of that system;

(3) The system is not adversely affected 

during and after the time the rotorcraft is 

exposed to HIRF environment II, as 

described in appendix D to this part; and

(4) Each function required during operation 

under visual flight rules is not adversely 

affected during and after the time the 

rotorcraft is exposed to HIRF environment 

III, as described in appendix D to this part.

(b) Each electrical and electronic system 

that performs a function whose failure 

would significantly reduce the capability of 

the rotorcraft or the ability of the 

flightcrew to respond to an adverse 

operating condition must be designed and 

installed so the system is not adversely 

affected when the equipment providing 

these functions is exposed to equipment 

HIRF test level 1 or 2, as described in 

appendix D to this part.

(c) Each electrical and electronic system 

that performs a function whose failure 

would reduce the capability of the 

rotorcraft or the ability of the flightcrew to 

respond to an adverse operating condition, 

must be designed and installed so the 

system is not adversely affected when the 

equipment providing these functions is 

exposed to equipment HIRF test level 3, as 

described in appendix D to this part.

(d) Before December 1, 2012, an electrical 

or electronic system that performs a 

function whose failure would prevent the 

continued safe flight and landing of a 

rotorcraft may be designed and installed 

without meeting the provisions of 

paragraph (a) provided—

(1) The system has previously been shown 

to comply with special conditions for 

HIRF, prescribed under §21.16, issued 

before December 1, 2007;

(2) The HIRF immunity characteristics of 

the system have not changed since 

compliance with the special conditions was 

demonstrated; and

(3) The data used to demonstrate 

compliance with the special conditions is 

provided.
92

Instruments: Installation 

§27.1321

Arrangement 

and visibility 

Modified (a) Each flight, navigation, and powerplant 

instrument for use by any pilot required for 

the pilot by this G-1U Issue Paper must be 

easily visible to him. 

(b) For each multiengine rotorcraft, 

identical powerplant instruments must be 

located so as to prevent confusion as to 

which engine each instrument relates. 

(c) Instrument panel vibration may not 

damage, or impair the readability or 

accuracy of, any instrument.

(d) If a visual indicator is provided to 

indicate malfunction of an instrument or 

system, it that indicator must be effective 

under all probable cockpit lighting

operating conditions.

Rationale: Subparagraph (a) was kept 

because instruments required by the UAS 

pilot should be easily visible. 

Subparagraph (b) was deleted because 

requirements for multiengine aircraft are 

beyond the scope of this issue paper. 

Subparagraph (c) was deleted because the 

instrument panel is not located inside the 

vehicle; any vibration of the instrument 

panel is incidental. Thus, no specific 

requirement is provided.

Subparagraph (d) was kept. The pilot 

displays are located in a ground control 

station. The design and operation at this 

station must accommodate different lighting 

and operating conditions.

§27.1322

Warning, 

caution, and 

advisory lights 

Modified If warning, caution or advisory lights are 

installed in the cockpit, required by the 

type design are installed in the ground 

control station, they must, unless otherwise 

approved by the Administrator, be—

(a) Red, for warning lights (lights 

indicating a hazard which may require 

immediate corrective action): 

(b) Amber, for caution lights (lights 

indicating the possible need for future 

corrective action); 

(c) Green, for safe operation lights; and 

(d) Any other color, including white, for 

lights not described in paragraphs (a) 

through (c) of this section, provided the 

color differs sufficiently from the colors 

prescribed in paragraphs (a) through (c) of 

this section to avoid possible confusion.

Rationale: Text was modified because the 

warning, caution, and advisory lights, if 

any, will be located in the ground control 

station instead of a cockpit.

§27.1323 

Airspeed 

indicating 

system

Excluded Summary: This paragraph provides various requirements for calibration of airspeed 

instruments.

Rationale: Out of ConOps scope. The UAS pilot does not have inner loop control of 

vehicle, so an airspeed indicator is not required. A vendor could provide an airspeed 

indicator, but it is not required for continued safe flight and landing.

§27.1325

Static pressure 

systems 

Modified (a) If a static system is installed, each 

instrument with a static air sensor case 

connections must be vented so that the 

influence of rotorcraft speed, the opening 

and closing of windows, airflow variation, 

and moisture or other foreign matter does 

not seriously affect its accuracy. 

(b) Each static pressure port must be 

designed and located in such manner that 

the correlation between air pressure in the 

static pressure system and true ambient 

atmospheric static pressure is not altered 

Rationale: Some UAS may be designed 

without the need for a system to determine 

static pressure. Protection of static air 

sensors is related to maintaining 

controllability and stability, which is related 

to maintaining rotor system integrity (see 

CMS Issue Paper). Subparagraph (b) was 

removed because this requirement only 

applies in icing conditions that are outside 

the defined operational limits. 

Subparagraphs (c) and (d) were removed 

because the vehicle under consideration 
93

when the rotorcraft encounters icing 

conditions. An anti-icing means or an 

alternate source of static pressure may be 

used in showing compliance with this 

requirement. If the reading of the altimeter, 

when on the alternate static pressure 

system, differs from the reading of the 

altimeter when on the primary static 

system by more than 50 feet, a correction 

card must be provided for the alternate 

static system. 

(c) Except as provided in paragraph (d) of 

this section, if the static pressure system 

incorporates both a primary and an 

alternate static pressure source, the means 

for selecting one or the other source must 

be designed so that—

(1) When either source is selected, the 

other is blocked off; and 

(2) Both sources cannot be blocked off 

simultaneously. 

(d) For unpressurized rotorcraft, paragraph 

(c)(1) of this section does not apply if it 

can be demonstrated that the static pressure 

system calibration, when either static 

pressure source is selected is not changed 

by the other static pressure source being 

open or blocked.

does not have multiple static pressure 

sources.

§27.1327 

Magnetic 

direction 

indicator

Excluded Summary: This paragraph provides various requirements for a magnetic director 

indicator (compass).

Rationale: Out of ConOps scope. The UAS pilot does not have inner loop control of 

vehicle, so a magnetic direction indicator is not required. A vendor could provide a 

magnetic direction indicator, but it is not required for continued safe flight and landing.

§27.1329

Automatic 

pilot system

Modified (a) Each automatic pilot system must be 

designed so that the automatic pilot can—

(1) Be sufficiently overpowered by one 

pilot to allow control of the rotorcraft; and

(2) Be readily and positively disengaged by 

each pilot to prevent it from interfering 

with control of the rotorcraft.

(b) Unless there is automatic 

synchronization, each system must have a 

means to readily indicate to the pilot the 

alignment of the actuating device in 

relation to the control system it operates.

(c) Each manually operated control for the 

system's operation must be readily 

accessible to the pilots.

(d) The system must be designed and 

adjusted so that, within the range of 

adjustment available to the pilot, it cannot 

produce hazardous loads on the rotorcraft 

or create hazardous deviations in the flight 

Rationale: The requirements in §27.1329 

presuppose a pilot is interacting with the 

autopilot to control the rotorcraft. The 

designated operation does not allow direct 

pilot control of rotorcraft servomechanisms; 

therefore, there is no need for requirements 

related to manual control of rotorcraft.

The phrase “hazardous deviations of flight 

path” is interpreted to mean hazards to the 

vehicle itself (e.g., hazard of the vehicle 

ejecting high-energy parts) and it does not 

include hazards of the flight path itself (e.g., 

a vehicle exiting the containment region). 

Thus, the inclusion of this requirement does 

not mandate any particular architecture of 

the containment system or other parts of the 

UAS.
94

path under any flight condition appropriate 

to its use, either during normal operation or 

in the event of a malfunction, assuming 

that corrective action begins within a 

reasonable period of time.

(e) If the automatic pilot integrates signals 

from auxiliary controls or furnishes signals 

for operation of other equipment, there 

must be positive interlocks and sequencing 

of engagement to prevent improper 

operation.

(f) If the automatic pilot system can be 

coupled to airborne navigation equipment, 

means must be provided to indicate to the 

pilots the current mode of operation. 

Selector switch position is not acceptable 

as a means of indication.

§27.1335 

Flight director 

systems

Excluded Summary: This paragraph provides a requirement to indicate the mode of the flight 

director to the crew.

Rationale: Out of ConOps scope. The UAS pilot does not have inner loop control of 

vehicle, so a flight director is not needed. A vendor could provide a flight director, but 

it is not required for continued safe flight and landing.

§27.1337 

Powerplant 

instruments

Rolled up 

to PPS

Summary: This paragraph provides requirements for powerplant instruments, especially 

fuel flow and oil-related instruments.

Rationale: Monitoring of some powerplant systems may be necessary to avoid 

explosion hazards, so this paragraph was rolled up. Subparagraphs (a2), (d), and (e) are 

especially relevant.

Electrical Systems and Equipment 

§27.1351

General 

Modified (a) Electrical system capacity. Electrical

equipment whose failure could adversely 

affect safety must be adequate for its 

intended use. In addition—

(1) Electric power sources, their 

transmission cables, and their associated 

control and protective devices must be able 

to furnish the required power at the proper 

voltage to each load circuit essential for 

safe operation; and 

(2) Compliance with paragraph (a)(1) of 

this section must be shown by an electrical 

load analysis, or by electrical 

measurements that take into account the 

electrical loads applied to the electrical 

system, in probable combinations and for 

probable durations. 

(b) Function. For each safety-critical

electrical system, the following apply: 

(1) Each system, when installed, must be—

(i) Free from hazards in itself, in its method 

of operation, and in its effects on other 

parts of the rotorcraft; and 

(ii) Protected from fuel, oil, water, other 

Rationale: Loss of electrical power does 

not necessarily lead to a hazardous event. 

Proper functioning of the electrical system 

is only required on the parts of the system 

needed to maintain safety (e.g., the 

independent power source for the 

containment system needs to meet this 

requirement).
95

detrimental substances, and mechanical 

damage. 

(2) Electric power sources must function 

properly when connected in combination or 

independently. 

(3) No failure or malfunction of any source 

may impair the ability of any remaining 

source to supply load circuits essential for 

safe operation. 

(4) Each electric power source control 

must allow the independent operation of 

each source. 

(c) Generating system. There must be at 

least one generator if the system supplies 

power to load circuits essential for safe 

operation. In addition—

(1) Each generator must be able to deliver 

its continuous rated power; 

(2) Generator voltage control equipment 

must be able to dependably regulate each 

generator output within rated limits; 

(3) Each generator must have a reverse 

current cutout designed to disconnect the 

generator from the battery and from the 

other generators when enough reverse 

current exists to damage that generator; 

and 

(4) Each generator must have an 

overvoltage control designed and installed 

to prevent damage to the electrical system, 

or to equipment supplied by the electrical 

system, that could result if that generator 

were to develop an overvoltage condition. 

(d) Instruments. There must be means to 

indicate to appropriate crewmembers the 

electric power system quantities essential 

for safe operation of the system. In 

addition—

(1) For direct current systems, an ammeter 

that can be switched into each generator 

feeder may be used; and 

(2) If there is only one generator, the 

ammeter may be in the battery feeder. 

(e) External power. If provisions are made 

for connecting external power to the 

rotorcraft, and that external power can be 

electrically connected to equipment other 

than that used for engine starting, means 

must be provided to ensure that no external 

power supply having a reverse polarity, or 

a reverse phase sequence, can supply 

power to the rotorcraft's electrical system.
96

§27.1353

Storage battery 

design and 

installation 

Modified For equipment whose failure could 

adversely safety:

(a) Each storage battery must be designed 

and installed as prescribed in this section. 

(b) Safe cell temperatures and pressures 

must be maintained during any probable 

charging and discharging condition. No 

uncontrolled increase in cell temperature 

may result when the battery is recharged 

(after previous complete discharge)—

(1) At maximum regulated voltage or 

power; 

(2) During a flight of maximum duration; 

and 

(3) Under the most adverse cooling 

condition likely to occur in service. 

(c) Compliance with paragraph (b) of this 

section must be shown by test unless 

experience with similar batteries and 

installations has shown that maintaining 

safe cell temperatures and pressures 

presents no problem. 

(d) No explosive or toxic gases emitted by 

any battery in normal operation, or as the 

result of any probable malfunction in the 

charging system or battery installation, 

may accumulate in hazardous quantities 

within the rotorcraft. 

(e) No corrosive fluids or gases that may 

escape from the battery may damage 

surrounding structures or adjacent essential 

equipment. 

(f) Each nickel cadmium battery 

installation capable of being used to start 

an engine or auxiliary power unit must 

have provisions to prevent any hazardous 

effect on structure or essential systems that 

may be caused by the maximum amount of 

heat the battery can generate during a short 

circuit of the battery or of its individual 

cells. 

(g) Nickel cadmium battery installations 

capable of being used to start an engine or 

auxiliary power unit must have—

(1) A system to control the charging rate of 

the battery automatically so as to prevent 

battery overheating; 

(2) A battery temperature sensing and 

over-temperature warning system with a 

means for disconnecting the battery from 

its charging source in the event of an overtemperature condition; or 

(3) A battery failure sensing and warning 

system with a means for disconnecting the 

Rationale: Loss of battery power does not 

necessarily lead to any identified hazard. 

Therefore proper functioning of the 

batteries is only required where the battery 

supplies the parts of the system needed to 

maintain safety (e.g., the containment 

system).
97

battery from its charging source in the 

event of battery failure. 

§27.1357 

Circuit 

protective 

devices 

Modified For equipment whose failure could 

adversely affect safety:

(a) Protective devices, such as fuses or 

circuit breakers, must be installed in each 

electrical circuit other than—

(1) The main circuits of starter motors; and 

(2) Circuits in which no hazard is presented 

by their the omission of protective devices. 

(b) A protective device for a circuit

essential to flight safety may not be used to 

protect any other circuit. 

(c) Each resettable circuit protective device 

(“trip free” device in which the tripping 

mechanism cannot be overridden by the 

operating control) must be designed so 

that—

(1) A manual operation is required to 

restore service after tripling [sic]; and 

(2) If an overload or circuit fault exists, the 

device will open the circuit regardless of 

the position of the operating control. 

(d) If the ability to reset a circuit breaker or 

replace a fuse is essential to safety in flight, 

that circuit breaker or fuse must be located 

and identified so that it can be readily reset 

or replaced in flight. 

(e) If fuses are used, there must be one 

spare of each rating, or 50 percent spare 

fuses of each rating, whichever is greater.

Rationale: This change is strictly 

unnecessary given the caveat in 

subparagraph (a)(2). However, this change 

emphasizes the point that only systems that 

can create hazards must include such 

protective devices.

§27.1361 

Master switch 

Modified For equipment whose failure could 

adversely affect safety:

(a) There must be a master switch 

arrangement to allow ready disconnection 

of each electric power source from the 

main bus. The point of disconnection must 

be adjacent to the sources controlled by the 

switch. 

(b) Load circuits may be connected so that 

they remain energized after the switch is 

opened, if they are protected by circuit 

protective devices, rated at five amperes or 

less, adjacent to the electric power source. 

(c) The master switch or its controls must 

be installed so that the switch is easily 

discernible and accessible to a 

crewmember in flight.

Rationale: A master switch is necessary to 

ensure the safety of crewmembers before 

takeoff and after landing.

§27.1365

Electric cables 

Modified For equipment whose failure could 

adversely affect safety:

(a) Each electric connecting cable must be 

of adequate capacity. 

(b) Each cable that would overheat in the 

Rationale: Electrical cable failure (e.g., 

short circuit, open circuit) does not 

necessarily lead to any identified hazard. 

Therefore proper functioning of the 

electrical cables is only required on the 
98

event of circuit overload or fault must be at 

least flame resistant and may not emit 

dangerous quantities of toxic fumes. 

(c) Insulation on electrical wire and cable 

installed in the rotorcraft must be selfextinguishing when tested in accordance 

with appendix F, part I(a)(3), of part 25 of 

this chapter.

parts of the system needed to maintain 

safety.

§27.1367 

Switches 

Modified For equipment whose failure could 

adversely affect safety:

Each switch must be—

(a) Able to carry its rated current; 

(b) Accessible to the crew; and 

(c) Labeled as to operation and the circuit 

controlled.

Rationale: Proper functioning of safetyrelevant switches is necessary to ensure the 

safety of crewmembers before takeoff and 

after landing.

Lights 

§27.1381

Instrument 

lights

Modified The instrument lights For each display or 

other presentation of data required for 

systems whose failure adversely affects 

safety, that display or presentation must—

(a) Make each instrument, switch, and 

other devices for which they are provided

relevant device, display, or presentation

easily readable; and 

(b) Be installed so that—

(1) Their direct rays are shielded from the 

pilot's eyes; and 

(2) Nno objectionable reflections or 

illumination levels render required data 

unintelligible to the pilot in normal 

operations are visible to the pilot

Rationale: In general, the instruments 

(displays) in the ground control station will 

provide their own lighting. Instrument 

lights in a cockpit are required for the pilot 

to perform safety-related tasks.

§27.1383

Landing lights 

– and 

supplemental 

lighting for 

night 

operations

Modified (a) Each required landing or hovering light

landing or hovering light or supplemental 

ground or airborne required for approved 

night rotorcraft operations must be 

approved. 

(b) Each landing light must be installed so 

that—

(1) No objectionable glare is visible to the 

pilot; 

(2) The pilot is not adversely affected by 

halation; and 

(3) It provides enough light for night 

operation, including hovering and landing. 

(c) At least one separate switch must be 

provided, as applicable—

(1) For each separately installed landing 

light; and 

(2) For each group of landing lights 

installed at a common location.

Rationale: This requirement was reworded 

since landing lights may not be located only 

on the rotorcraft, but may be provided by 

ground support equipment.
99

§27.1385 

Position light 

system 

installation

Excluded Summary: This paragraph provides position light requirements.

Rationale: Out of ConOps scope. Mitigated by other regulation. Per the ConOps, the 

unmanned rotorcraft will yield right-of-way. Due to the reduced size of the vehicle

(compared with Part 27 rotorcraft), use of position lights may not enhance situational 

awareness for pilots of other aircraft.

§27.1387 

Position light 

system 

dihedral 

angles.

Excluded Summary: This paragraph provides requirements specific to the dihedral angle of the 

position lights.

Rationale: Out of ConOps scope. Secondary hazard. Per the ConOps, the unmanned 

rotorcraft will yield right-of-way. Due to the reduced size of the vehicle (compared with 

Part 27 rotorcraft), use of position lights may not enhance situational awareness for 

pilots of other aircraft.

§27.1389 

Position light 

distribution 

and intensities

Excluded Summary: This paragraph provides requirements specific to the intensities of position 

lights.

Rationale: Out of ConOps scope. Secondary hazard. Per the ConOps, the unmanned 

rotorcraft will yield right-of-way. Due to the reduced size of the vehicle (compared with 

Part 27 rotorcraft), use of position lights may not enhance situational awareness for 

pilots of other aircraft.

§27.1391 

Minimum 

intensities in 

the horizontal 

plane of 

forward and 

rear position 

lights

Excluded Summary: This paragraph sets minimum requirements for position light intensities in 

the horizontal plane.

Rationale: Out of ConOps scope. Secondary hazard. Per the ConOps, the unmanned 

rotorcraft will yield right-of-way. Due to the reduced size of the vehicle (compared with 

Part 27 rotorcraft), use of position lights may not enhance situational awareness for 

pilots of other aircraft.

§27.1393 

Minimum 

intensities in 

any vertical 

plane of 

forward and 

rear position 

lights

Excluded Summary: This paragraph sets minimum requirements for position light intensities in 

the vertical plane.

Rationale: Out of ConOps scope. Secondary hazard. Per the ConOps, the unmanned 

rotorcraft will yield right-of-way. Due to the reduced size of the vehicle (compared with 

Part 27 rotorcraft), use of position lights may not enhance situational awareness for 

pilots of other aircraft.

§27.1395 

Maximum 

intensities in 

overlapping 

beams of 

forward and 

rear position 

lights

Excluded Summary: This paragraph sets maximum intensities for position lights.

Rationale: Out of ConOps scope. Secondary hazard. Per the ConOps, the unmanned 

rotorcraft will yield right-of-way. Due to the reduced size of the vehicle (compared with 

Part 27 rotorcraft), use of position lights may not enhance situational awareness for 

pilots of other aircraft.

§27.1397

Color 

specifications

As is Each position light color must have the 

applicable International Commission on 

Illumination chromaticity coordinates as 

follows:

(a) Aviation red—

y is not greater than 0.335; and 

z is not greater than 0.002.

(b) Aviation green—

x is not greater than 0.440−0.320y; 

x is not greater than y−0.170; and 

Rationale: These requirements are 

maintained to ensure compatibility with the 

expected colors by other airspace users.
100

y is not less than 0.390−0.170x.

(c) Aviation white—

x is not less than 0.300 and not greater than 

0.540; 

y is not less than x−0.040” or yc−0.010, 

whichever is the smaller; and 

y is not greater than x+0.020 nor 

0.636−0.400x; 

Where yc is the y coordinate of the 

Planckian radiator for the value of x

considered.

§27.1399 

Riding light

Excluded Summary: This paragraph provides requirements for riding lights (used in water 

applications).

Rationale: Out of ConOps scope. Water operations are not part of the ConOps.

§27.1401

Anticollision 

light system 

Modified (a) General. If certification for night 

operation is requested, the rotorcraft must 

have an anticollision light system that—

(1) Consists of one or more approved 

anticollision lights located so that their 

emitted light will not impair the crew's 

vision or detract from the conspicuity of 

the position lights; and 

(2) Meets the requirements of paragraphs 

(b) through (f) of this section. 

(b) Field of coverage. The system must 

consist of enough lights to illuminate the 

vital areas around the rotorcraft, 

considering the physical configuration and 

flight characteristics of the rotorcraft. The 

field of coverage must extend in each 

direction within at least 30 degrees below 

the horizontal plane of the rotorcraft, 

except that there may be solid angles of 

obstructed visibility totaling not more than 

0.5 steradians. 

(c) Flashing characteristics. The 

arrangement of the system, that is, the 

number of light sources, beam width, speed 

of rotation, and other characteristics, must 

give an effective flash frequency of not less 

than 40, nor more than 100, cycles per 

minute. The effective flash frequency is the 

frequency at which the rotorcraft's 

complete anticollision light system is 

observed from a distance, and applies to 

each sector of light including any overlaps 

that exist when the system consists of more 

than one light source. In overlaps, flash 

frequencies may exceed 100, but not 180, 

cycles per minute. 

(d) Color. Each anticollision light must be 

aviation red and must meet the applicable 

requirements of §27.1397. 

Rationale: A small addition was made to 

this requirement in subparagraph (g) to 

emphasize that the pilot must be able to turn 

off the anti-collision lights to ensure other 

crewmembers can perform their safety role 

during takeoffs and landings.
101

(e) Light intensity. The minimum light 

intensities in any vertical plane, measured 

with the red filter (if used) and expressed 

in terms of “effective” intensities, must 

meet the requirements of paragraph (f) of 

this section. The following relation must be 

assumed: 

View or download PDF

where:

Ie=effective intensity (candles). 

I(t)=instantaneous intensity as a function of 

time. 

t2−t1=flash time interval (seconds). 

Normally, the maximum value of effective 

intensity is obtained when t2 and t1 are 

chosen so that the effective intensity is 

equal to the instantaneous intensity at t2

and t1.

(f) Minimum effective intensities for 

anticollision light. Each anticollision light 

effective intensity must equal or exceed the 

applicable values in the following table:

Angle above 

or below the 

horizontal 

plane

Effective 

intensity 

(candles)

0° to 5° 150

5° to 10° 90

10° to 20° 30

20° to 30° 15

(g) A means must be provided for the pilot 

to deactivate the anticollision lights in any 

flight phase.

Safety Equipment

§27.1411

General

Modified (a) Required safety equipment to be used 

by the crew in an emergency, such as flares 

and automatic liferaft releases, must be 

readily accessible.

(b) Stowage provisions for required safety 

equipment must be furnished and must—

(1) Be arranged so that the equipment is 

directly accessible and its location is 

obvious; and 

(2) Protect the safety equipment from 

Rationale: The particular examples of 

safety equipment may not be relevant for 

unmanned rotorcraft operations; however, 

the pilot and other crewmembers may need 

some safety equipment (e.g., fire 

extinguishers) that must be readily 

available.
102

damage caused by being subjected to the 

inertia loads specified in §27.561.

§27.1413 

Safety belts

Excluded Summary: This paragraph requires seat belts to have a metal latching device.

Rationale: Does not map to a hazard.

§27.1415 

Ditching 

equipment

Excluded Summary: This paragraph provides requirements for ditching equipment (e.g., life 

rafts).

Rationale: Does not map to a hazard.

§27.1419 

Ice protection

Excluded Summary: This paragraph provides requirements for operation in icing conditions.

Rationale: Out of ConOps scope.

§27.1435 

Hydraulic 

systems

Excluded Summary: This paragraph provides requirements for design, test, and installation of 

hydraulic equipment.

Rationale: Does not map to a hazard. Ejection of high energy parts from a rupture of the 

hydraulic system was considered sufficiently inconsequential.

§27.1457 

Cockpit voice 

recorders

Excluded Summary: This paragraph provides requirements for cockpit voice recorders.

Rationale: It is not clear what cockpit (or ground control station) voice recording would 

serve. The expectation is that accident investigation (if necessary) will not need voice 

recordings. Flight data (as per §27.1459) is assumed to be more relevant for 

determining accident cause.

§27.1459

Flight data 

recorders 

Modified (a) Each flight recorder required by the 

operating approval associated with the 

vehicle specified in this type design must 

meet the data recording requirements 

specified by the Administrator.

rules of Subchapter G of this chapter must 

be installed so that: 

(1) It is supplied with airspeed, altitude, 

and directional data obtained from sources 

that meet the accuracy requirements of 

§27.1323, §27.1325, and §27.1327 of this 

part, as applicable; 

(2) The vertical acceleration sensor is 

rigidly attached, and located longitudinally 

within the approved center of gravity limits 

of the rotorcraft; 

(3)(i) It receives its electrical power from 

the bus that provides the maximum 

reliability for operation of the flight data 

recorder without jeopardizing service to 

essential or emergency loads.

(ii) It remains powered for as long as 

possible without jeopardizing emergency 

operation of the rotorcraft.

(4) There is an aural or visual means for 

preflight checking of the recorder for 

proper recording of data in the storage 

medium; 

(5) Except for recorders powered solely by 

the engine-driven electrical generator 

system, there is an automatic means to 

simultaneously stop a recorder that has a 

data erasure feature and prevent each 

Rationale: It is not clear exactly what 

purpose a flight data recorder would serve 

for an unmanned rotorcraft, nor is it clear 

that an unmanned aircraft needs the detailed 

survivability requirements as described in 

this paragraph. The ground control station 

may provide all necessary data recording. 

The language was changed to allow more 

generic requirements for data recording. 
103

erasure feature from functioning, within 10 

minutes after any crash impact; and

(6) Whether the cockpit voice recorder and 

digital flight data recorder are installed in 

separate boxes or in a combination unit, no 

single electrical failure external to the 

recorder may disable both the cockpit 

voice recorder and the digital flight data 

recorder.

(b) Each nonejectable recorder container 

must be located and mounted so as to 

minimize the probability of container 

rupture resulting from crash impact and 

subsequent damage to the record from fire. 

(c) A correlation must be established 

between the flight recorder readings of 

airspeed, altitude, and heading and the 

corresponding readings (taking into 

account correction factors) of the first 

pilot's instruments. This correlation must 

cover the airspeed range over which the 

aircraft is to be operated, the range of 

altitude to which the aircraft is limited, and 

360 degrees of heading. Correlation may 

be established on the ground as 

appropriate. 

(d) Each recorder container must: 

(1) Be either bright orange or bright 

yellow; 

(2) Have a reflective tape affixed to its 

external surface to facilitate its location 

under water; and 

(3) Have an underwater locating device, 

when required by the operating rules of this 

chapter, on or adjacent to the container 

which is secured in such a manner that they 

are not likely to be separated during crash 

impact. 

(e) When both a cockpit voice recorder and 

a flight data recorder are required by the 

operating rules, one combination unit may 

be installed, provided that all other 

requirements of this section and the 

requirements for cockpit voice recorders 

under this part are met.

§27.1461

Equipment 

containing 

high energy 

rotors 

Modified (a) Equipment whose failure adversely 

affects safety and contains high energy 

rotors must meet paragraph (b), (c), or (d) 

of this section. 

(b) High energy rotors contained in 

equipment must be able to withstand 

damage caused by malfunctions, vibration, 

abnormal speeds, and abnormal 

temperatures. In addition—

Rationale: The requirement was rewritten 

to emphasize that not all equipment with 

high-energy rotors that fails is capable of 

causing harm. Furthermore, this 

requirement recognizes that non-engine 

related components might contain highenergy rotors.
104

(1) Auxiliary rotor cases must be able to 

contain damage relevant to Paragraph (a) 

of this section and caused by the failure of 

high energy rotor blades; and 

(2) Equipment control devices, systems, 

and instrumentation must reasonably 

ensure that no operating limitations 

affecting the integrity of high energy rotors 

will be exceeded in service. 

(c) It must be shown by test that equipment 

containing high energy rotors can, without 

directly causing one or more of the failure 

conditions addressed in Paragraph (a) of 

this section, contain any failure of a high 

energy rotor that occurs at the highest 

speed obtainable with the normal speed 

control devices inoperative. 

(d) Equipment containing high energy 

rotors must be located where rotor failure 

will neither endanger the occupants nor not

adversely affect continued safe flight.

Subpart G—Operating Limitations and Information

§27.1501

General 

Modified (a) Each operating limitation required by 

the Administrator specified in §27.1503 

through §27.1525 and other limitations and 

information necessary for safe operation 

must be established and

(b) The operating limitations and other 

information necessary for safe operation 

must be made available to the 

crewmembers as prescribed in §27.1541 

through §27.1589.

Rationale: References to specific 

subparagraphs that specify operating 

limitations for Part 27 rotorcraft were 

deleted because operating limitations 

relevant to an unmanned rotorcraft 

operating in a confined area have not yet 

been established. The reference was 

changed to a more general reference to 

operating limitations established by the 

FAA Administrator. Those operating 

limitations should still be made available to 

crewmembers.

Operating Limitations

§27.1503 

Airspeed 

limitations: 

general

Excluded Summary: This paragraph requires identifying an operating speed range, especially for 

establishing speed limitations.

Rationale: Does not map to a hazard. Operating at the UA’s speed limitations is not 

directly linked to a hazard, so it is necessary to know what the limits are. For the most 

part, operating at the speed limits is not likely under the ConOps.

§27.1505 

Never-exceed 

speed

Excluded Summary: This paragraph establishes conditions on the never-exceed speed.

Rationale: Does not map to a hazard. It is not necessary to establish a never-exceed 

speed related to the structural limits of the vehicle, because exceeding that limit does not 

map directly to a hazard.

§27.1509 

Rotor speed

Rolled up 

to SI

Summary: This paragraph establishes ranges of values for maximum and minimum 

rotor speeds under power-off and power-on conditions. 

Rationale: While maximum and minimum rotor speeds are clearly related to 

maintaining rotor system integrity, it is not known whether the specific ranges required 

for manned rotorcraft are directly applicable to an unmanned rotorcraft with different 

risk profiles. The paragraph was relegated to the rollup where the applicant and the 

regulator could determine the appropriate ranges of values.
105

§27.1519 

Weight and 

center of 

gravity

Rolled up 

to CMS(a)

Summary: This paragraph requires that weight and center of gravity limitations be 

established. 

Rationale: Since these are critical parameters affecting controllability and 

maneuverability, this requirement was added to the CMS rollup.

§27.1521 

Powerplant 

limitations

Rolled up 

to PPS

Summary: This paragraph specifies a requirement to establish relevant powerplant 

limitations, such as torque, temperature, speed, and other parameters, under a variety of 

conditions and for various time limits. 

Rationale: The requirement to establish powerplant limitations was considered relevant 

to protecting rotor system integrity, but the specific conditions and times were 

considered too detailed. So, the general requirement for powerplant limitations was 

retained but rolled up into the more general language of the issue paper.

§27.1523

Minimum 

flight crew 

Modified The minimum flight crew must be 

established so that it is sufficient for safe 

operation, considering—

(a) The workload on and safety roles of

individual crewmembers; and 

(b) The accessibility and ease of operation 

of necessary controls by the appropriate 

crewmember; and

(c) The kinds of operation authorized under 

§27.1525.

Rationale: The word “flight” was deleted as 

a modifier to crew, since it is not 

appropriate for UAS (given the definition of 

crew). Wording was added in subparagraph 

(a) to include consideration of the crew’s 

safety role in determining the minimum size 

of the UAS crew. 

Words related to accessibility and ease of 

operation of controls were deleted in 

subparagraph (b), assuming that the original 

text referred to the accessibility of onboard 

controls to onboard crew, and that more 

general language about workload is desired 

because accessibility and ease of operation 

are only 2 of a larger set of attributes that 

affect the crew’s ability to perform their 

safety role.

§27.1525

Kinds of 

operations

Modified The kinds of operations (such as VFR, IFR, 

day, night, or icing) for which the 

rotorcraft UAS is approved are established 

by demonstrated compliance with the 

applicable certification requirements and 

by the installed equipment.

Rationale: The approved operation includes 

capabilities of the whole UA system, 

including the vehicle, the ground control 

station, datalinks, etc.

§27.1527

Maximum 

operating 

altitude 

Modified The maximum altitude up to which 

operation is allowed, as limited by flight, 

structural, powerplant, functional, safety,

or equipment characteristics, must be 

established.

Rationale: The word “safety” was added to 

the list of considerations for establishing 

maximum altitude because operating 

limitations on altitude are an explicit 

limitation on the operation to help mitigate 

safety concerns when operating at altitudes 

where air traffic is expected (e.g., above 

500 ft).

§27.1529

Instructions for 

Continued 

Airworthiness

Modified The applicant must prepare Instructions for 

Continued Airworthiness in accordance 

with this G-1U issue paper, Aappendix A 

to this part that are acceptable to the 

Administrator. The Iinstructions may be 

incomplete at type certification if a 

program exists to ensure their completion 

prior to delivery of the first rotorcraft or 

issuance of a standard certificate of 

airworthiness, whichever occurs later.

Rationale: Instructions for continued 

airworthiness are applicable. Editorial 

changes were made to make it clear that the 

relevant instructions for continued 

airworthiness are those specified in the G1U issue paper. 
106

Markings and Placards

§27.1541

General 

Modified (a) The rotorcraft UAS must contain—

(1) The markings and placards specified in 

this G-1U Issue Paper §27.1545 through 

§27.1565, and 

(2) Any additional information, instrument 

markings, and placards required for the 

safe operation of rotorcraft UAS with 

unusual design, operating or handling 

characteristics. 

(b) Each marking and placard prescribed in 

paragraph (a) of this section—

(1) Must be displayed in a conspicuous 

place; and 

(2) May not be easily erased, disfigured, or 

obscured.

Rationale: In (a), “rotorcraft” was changed 

to “UAS” (in 2 places) because markings 

and placards may be located in the ground 

control station or on other equipment in 

addition to the rotorcraft. A UAS may need 

markings and placards for safe operation 

that are not usually needed for manned 

rotorcraft (e.g., markings for landing zone 

of vehicle). 

References to specific paragraphs that 

specify markings and placards in (1) were 

deleted in favor of a more general reference 

to the requirements for markings and 

placards identified in this G-1U Issue Paper

(e.g., 27.1557, any of the special issue 

papers, etc.).

§27.1543 

Instrument 

markings: 

general

Excluded Summary: This paragraph addresses alignment of markings on cockpit instruments that 

have glass covers.

Rationale: Does not map to a hazard. Not UAS relevant. Instruments with glass covers 

(like those found in a cockpit) are not expected in a UAS ground control station.

§27.1545 

Airspeed 

indicator

Excluded Summary: This paragraph describes the markings necessary on an airspeed indicator.

Rationale: The requirements for an airspeed indicator was excluded, so requirements 

for markings are not needed.

§27.1547 

Magnetic 

direction 

indicator

Excluded Summary: This paragraph describes placards necessary for magnetic direction 

indicators.

Rationale: The requirements for a magnetic direction indicator was excluded, so 

requirements for placards are not needed.

§27.1549 

Powerplant 

instruments

Excluded Summary: This paragraph specifies required markings on powerplant instruments.

Rationale: The requirements for powerplant instruments were excluded, so 

requirements for markings are not needed

§27.1551 

Oil quantity 

indicator

Excluded Summary: This paragraph requires markings on oil quantity indicators.

Rationale: The requirements for an oil quantity indicator were excluded, so 

requirements for markings are not needed.

§27.1553 

Fuel quantity 

indicator

Excluded Summary: This paragraph specifies requirements for markings relative to unusable fuel 

level.

Rationale: The requirements for a fuel quantity indicator were excluded, so 

requirements for markings are not needed.

§27.1555 

Control 

markings

Modified (a) Each cockpit control, other than 

primary flight controls or control whose 

function is obvious, must be plainly 

marked as to its function and method of 

operation.

(b) For powerplant fuel controls—

(1) Each fuel tank selector control must be 

marked to indicate the position 

corresponding to each tank and to each 

existing cross feed position;

(2) If safe operation requires the use of any 

tanks in a specific sequence, that sequence 

Rationale: Requirements for controls, as 

described in this paragraph, have been 

excluded because the pilot does not have 

inner-loop control. However, subparagraph 

(d)(2) for marking emergency controls in 

red applies to emergency controls that the 

pilot would use to cause the rotorcraft to 

hover or land in emergency situations.
107

must be marked on, or adjacent to, the 

selector for those tanks; and

(3) Each valve control for any engine of a 

multiengine rotorcraft must be marked to 

indicate the position corresponding to each 

engine controlled.

(c) Usable fuel capacity must be marked as 

follows:

(1) For fuel systems having no selector 

controls, the usable fuel capacity of the 

system must be indicated at the fuel 

quantity indicator.

(2) For fuel systems having selector 

controls, the usable fuel capacity available 

at each selector control position must be 

indicated near the selector control.

(d) For accessory, auxiliary, and 

emergency controls—

(1) Each essential visual position indicator, 

such as those showing rotor pitch or 

landing gear position, must be marked so 

that each crewmember can determine at 

any time the position of the unit to which 

it relates; and

(2) Each emergency control must be red 

and must be marked as to method of 

operation.

(e) For rotorcraft incorporating retractable 

landing gear, the maximum landing gear 

operating speed must be displayed in clear 

view of the pilot.

§27.1557

Miscellaneous 

markings and 

placards 

Modified (a) BaggagePayload, and cargo 

compartments, and ballast location. Each 

baggage and cargo payload compartment, 

and each ballast location must have a 

placard stating any limitations on contents, 

including weight, that are necessary under 

the loading requirements. 

(b) Seats. If the maximum allowable 

weight to be carried in a seat is less than 

170 pounds, a placard stating the lesser 

weight must be permanently attached to the 

seat structure. 

(c) Fuel and oil filler openings. The 

following apply: 

(1) Fuel filler openings must be marked at 

or near the filler cover with—

(i) The word “fuel”; 

(ii) For reciprocating engine powered 

rotorcraft, the minimum fuel grade; 

(iii) For turbine engine powered rotorcraft, 

the permissible fuel designations; and 

(iv) For pressure fueling systems, the 

Rationale: “Baggage” and “cargo” were 

replaced in subparagraph (a) with “payload” 

because the UAS in an agricultural concept 

of operations is not intended to convey 

baggage or cargo, but will convey payload, 

such as agricultural chemicals or cameras or 

sensors for surveying fields. 

Subparagraph (b) was deleted because seats 

are not needed aboard the UAS. Any seats 

in the ground control station are not 

considered critical to safety of flight.

Subparagraph (c, 1, ii) was deleted because 

this G-1U was not intended to apply to 

rotorcraft with piston engines

Subparagraph (d) was deleted because there 

are no people on board the UAS, hence 

there is no need for emergency exit placards 

on the rotorcraft. We are assuming that 

OSHA requirements would necessitate exit 

placards for any indoor areas of a ground 

control station. 
108

maximum permissible fueling supply 

pressure and the maximum permissible 

defueling pressure. 

(2) Oil filler openings must be marked at or 

near the filler cover with the word “oil”. 

(d) Emergency exit placards. Each placard 

and operating control for each emergency 

exit must be red. A placard must be near 

each emergency exit control and must 

clearly indicate the location of that exit and 

its method of operation.

§27.1559

Limitations 

placard 

Modified There must be a placard in clear view of 

the pilot that specifies the kinds of 

operations (such as visual line-of-sight, 

beyond visual line-of-sight, VFR, IFR, day, 

night, or icing) for which the UAS

rotorcraft is approved.

Rationale: Visual line-of-sight and beyond 

line-of-sight operations are different from 

typical operations for Part 27 rotorcraft. 

They were added to the list of example 

operations because it is important for a 

UAS pilot to be aware of the sight-line 

limitations for approved UAS operations. 

§27.1561

Safety 

equipment 

Modified (a) Each required safety equipment control 

to be operated by the crew in emergency, 

such as controls for automatic liferaft 

releases, must be plainly marked as to its 

method of operation. 

(b) Each location, such as a locker or 

compartment, that carries any fire 

extinguishing, signaling, or other life 

saving equipment, must be so marked.

Rationale: The example of life rafts as 

safety equipment was deleted since there is 

no need for life rafts on UAS. The word 

“required” was added to safety equipment 

to indicate that not all safety equipment for 

a UAS may necessarily be considered 

required (e.g., a fire extinguisher in the 

ground control station should not need a 

placard). If it is required, it should be 

marked appropriately. 

§27.1565

Tail Rotor

As is Each tail rotor must be marked so that its 

disc is conspicuous under normal daylight 

ground conditions.

Rationale: If the unmanned rotorcraft has a 

tail rotor, then it should be marked as 

described. 

Rotorcraft Flight Manual and Approved Manual Material

§27.1581

General

Modified (a) Furnishing information. A Rotorcraft 

Flight Manual must be furnished with each 

rotorcraft, and it must contain the 

following: 

(1) Information required for UAS functions 

whose failure could adversely affect safety, 

and by §27.1583 through §27.1589.

(2) Other information that is necessary for 

safe operation because of design, 

operating, or handling characteristics. 

(b) Approved information. Each part of the 

manual listed in §27.1583 through 

§27.1589, that is appropriate to the 

rotorcraft, must be furnished, verified, and 

approved under its associated type 

certificate, and must be segregated, 

identified, and clearly distinguished from 

each unapproved part of that manual. 

(c) [Reserved] 

Rationale: A flight manual is important. 

References to Part 27 paragraphs specifying 

content of the flight manual were replaced 

with a more general requirement that the 

flight manual should provide information 

on safety-critical functions. Not all of the 

original paragraphs referenced were 

considered applicable to this issue paper.
109

(d) Table of contents. Each Rotorcraft 

Flight Manual must include a table of 

contents if the complexity of the manual 

indicates a need for it.

§27.1583 

Operating 

Limitations

Modified A Rotorcraft Flight Manual must contain 

operating limitations for each of the 

following, as relevant to safety-critical 

functions, including, but not limited to:

(a) Airspeed and Rrotor limitations. 

Information necessary for the marking of 

airspeed and rotor limitations on, or near, 

their respective indicators, must be 

furnished. The significance of each 

limitation and of the color coding must be 

explained.

(b) Powerplant limitations. The following 

information must be furnished:

(1) Limitations necessary to maintain 

powerplant integrity required by §27.1521.

(2) Explanation of the limitations, when 

appropriate.

(3) Information necessary for marking the 

instruments, required by §§27.1549 

through 27.1553.

(c) Weight and loading distribution. The 

weight and center of gravity limits required 

by §§27.25 and 27.27, respectively, must 

be furnished. If the variety of possible 

loading conditions warrants, instructions 

must be included to allow ready 

observance of the limitations specifically 

for takeoffs.

(d) Flight UAS crew. When a flight crew 

of more than one is required, the number 

and functions of the minimum flight crew 

determined under §27.1523 must be 

furnished.

(e) Kinds of operation. Each kind of 

operation for which the rotorcraft and its 

equipment installations are approved must 

be listed.

(f) [Reserved]

(g) Altitude. The altitude established under 

§27.1527 and an explanation of the 

limiting factors must be furnished.

Rationale: Operating limitations should be 

documented in the flight manual. 

Modifications were made to generalize

some of the requirements and delete 

references to Part 27 requirements that were 

not included in this issue paper.

§27.1585 

Operating 

procedures 

Modified (a) Parts of the manual containing 

operating procedures must have 

information concerning any normal and 

emergency procedures and other 

information necessary for safe operation, 

including takeoff and landing procedures 

and associated airspeeds. The manual must 

contain any pertinent information 

Rationale: Subparagraph (a) was kept 

because the kind of information specified is 

relevant.

Subparagraph (b) was deleted because 

multiengine rotorcraft were considered 

beyond the scope of the issue paper.

In subparagraph (c), the reference to 

§27.1505(c) (for a stabilized power-off 
110

including—

(1) The kind of takeoff surface used in the 

tests and each appropriate climbout speed; 

and

(2) The kind of landing surface used in the 

tests and appropriate approach and glide 

airspeeds.

(b) For multiengine rotorcraft, information 

identifying each operating condition in 

which the fuel system independence 

prescribed in §27.953 is necessary for 

safety must be furnished, together with 

instructions for placing the fuel system in a 

configuration used to show compliance 

with that section. 

(c) For helicopters for which a VNE (poweroff) is established under this G-1U Issue 

Paper §27.1505(c), information must be 

furnished to explain the VNE (power-off) 

and the procedures for reducing airspeed to 

not more than the VNE (power-off) 

following failure of all the engines. 

(d) For each rotorcraft showing compliance 

with §27.1353 (g)(2) or (g)(3), the 

operating procedures for disconnecting the 

battery from its charging source must be 

furnished. 

(e) If the unusable fuel supply in any tank 

exceeds five percent of the tank capacity, 

or one gallon, whichever is greater, 

information must be furnished which 

indicates that when the fuel quantity 

indicator reads “zero” in level flight, any 

fuel remaining in the fuel tank cannot be 

used safely in flight. 

(f) Information on the total quantity of 

usable fuel for each fuel tank must be 

furnished.

(g) The airspeeds and rotor speeds for 

minimum rate of descent and best glide 

angle as prescribed in §27.71 must be 

provided.

VNE) was deleted because it is not included 

in this G-1U Issue Paper. The vehicle’s 

ability to hold together under high speed 

conditions is not relevant to the concept of 

operations. 

In subparagraph (g), the reference to §27.71 

(Autorotation performance) was deleted

because there is no mandated requirement 

for autorotation. If autorotation is 

implemented, the airspeeds, rate of descent 

and glide angle curves are required.

§27.1587 

Performance 

information

Rolled up 

to CMS(a)

Summary: This paragraph specifies that the flight manual must include enough 

information to determine the height-speed envelope relative to a number of different 

parameters. Other information required by the paragraph (e.g., the requirement to 

establish altitudes, temperatures, and winds at which the vehicle can be safely hovered)

also relates to controllability and maneuverability.

Rationale: Since the requirement to establish the height-speed envelope (§27.87) were 

rolled up to CMS(a), this paragraph was also rolled up. 
111

§27.1589 

Loading 

information

Rolled up 

to CMS(a)

Summary: This paragraph requires instructions to be included in the Flight Manual for 

all possible loading conditions that can cause the center of gravity to be exceeded.

Rationale: Loading information is important to maintaining control margins that allow 

the vehicle to be safely controllable and maneuverable. This requirement is rolled up 

because only those loading conditions that affect controllability, maneuverability and 

stability needed to ensure rotor system integrity are needed. 

Appendix A—Instructions for Continued Airworthiness

A§27.1

General

Modified (a) This appendix specifies requirements 

for the preparation of Instructions for 

Continued Airworthiness as required by 

§27.1529. 

(b) The Instructions for Continued 

Airworthiness for each UAS rotorcraft must 

include the Instructions for Continued 

Airworthiness for each engine and rotor 

(hereinafter designated ‘products’), for 

each appliance required by this chapter, 

and any required information relating to 

the interface of those appliances and 

products with the UAS rotorcraft. If 

Instructions for Continued Airworthiness 

are not supplied by the manufacturer of an 

appliance or product installed in the UAS

rotorcraft, the Instructions for Continued 

Airworthiness for the UAS rotorcraft must 

include the information essential to the 

continued airworthiness of the UAS

rotorcraft. 

(c) The applicant must submit to the FAA a 

program to show how changes to the 

Instructions for Continued Airworthiness

made by the applicant or by the 

manufacturers of products and appliances 

installed in the UAS rotorcraft will be 

distributed

Rationale: Continued airworthiness 

considerations should apply to an 

unmanned rotorcraft that requires 

airworthiness certification just as they apply 

to a manned aircraft. The only change was 

to make it clear that the requirements apply 

to the UAS as a whole. So, “rotorcraft” was 

replaced with “UAS.”

A§27.2

Format

As is (a) The Instructions for Continued 

Airworthiness must be in the form of a 

manual or manuals as appropriate for the 

quantity of data to be provided. 

(b) The format of the manual or manuals 

must provide for a practical arrangement.

Rationale: Instructions for continued 

airworthiness should be in a usable form.

A§27.3

Content

Modified The contents of the manual or manuals 

must be prepared in the English language. 

The Instructions for Continued 

Airworthiness must contain the following 

manuals or sections, as appropriate, and 

information: 

(a) UAS rotorcraft maintenance manual or 

section.

(1) Introduction information that includes 

an explanation of the UAS’s rotorcraft

features and data to the extent necessary 

for maintenance or preventive 

Rationale: The same basic information for 

continued airworthiness applies to an

unmanned rotorcraft. The only change was 

to make it clear that the requirements apply 

to the UAS as a whole. So, “rotorcraft” was 

replaced with “UAS.”
112

maintenance. 

(2) A description of the UAS rotorcraft and 

its systems and installations including its 

engines, rotors, and appliances. 

(3) Basic control and operation information 

describing how the UAS rotorcraft

components and systems are controlled and 

how they operate, including any special 

procedures and limitations that apply. 

(4) Servicing information that covers 

details regarding servicing points, 

capacities of tanks, reservoirs, types of 

fluids to be used, pressures applicable to 

the various systems, location of access 

panels for inspection and servicing, 

locations of lubrication points, the 

lubricants to be used, equipment required 

for servicing, tow instructions and 

limitations, mooring, jacking, and leveling 

information. 

(b) Maintenance instructions. 

(1) Scheduling information for each part of 

the UAS rotorcraft and its engines, 

auxiliary power units, rotors, accessories, 

instruments and equipment that provides 

the recommended periods at which they 

should be cleaned, inspected, adjusted, 

tested, and lubricated, and the degree of 

inspection, the applicable wear tolerances, 

and work recommended at these periods. 

However, the applicant may refer to an 

accessory, instrument, or equipment 

manufacturer as the source of this 

information if the applicant shows the item 

has an exceptionally high degree of 

complexity requiring specialized 

maintenance techniques, test equipment, or 

expertise. The recommended overhaul 

periods and necessary cross references to 

the Airworthiness Limitations section of 

the manual must also be included. In 

addition, the applicant must include an 

inspection program that includes the 

frequency and extent of the inspections 

necessary to provide for the continued 

airworthiness of the UAS rotorcraft. 

(2) Troubleshooting information describing 

problem malfunctions, how to recognize 

those malfunctions, and the remedial action 

for those malfunctions. 

(3) Information describing the order and 

method of removing and replacing 

products and parts with any necessary 

precautions to be taken. 
113

(4) Other general procedural instructions 

including procedures for system testing 

during ground running, symmetry checks, 

weighing and determining the center of 

gravity, lifting and shoring, and storage 

limitations. 

(c) Diagrams of structural access plates and 

information needed to gain access for 

inspections when access plates are not 

provided. 

(d) Details for the application of special 

inspection techniques including 

radiographic and ultrasonic testing where 

such processes are specified. 

(e) Information needed to apply protective 

treatments to the structure after inspection. 

(f) All data relative to structural fasteners 

such as identification, discarded 

recommendations, and torque values. 

(g) A list of special tools needed.

A§27.4

Airworthiness 

Limitations 

section

As is The Instructions for Continued 

Airworthiness must contain a section, titled 

Airworthiness Limitations that is 

segregated and clearly distinguishable from 

the rest of the document. This section must 

set forth each mandatory replacement time, 

structural inspection interval, and related 

structural inspection procedure required for 

type certification. If the Instructions for 

Continued Airworthiness consist of 

multiple documents, the section required 

by this paragraph must be included in the 

principal manual. This section must 

contain a legible statement in a prominent 

location that reads: “The Airworthiness 

Limitations section is FAA approved and 

specifies inspections and other 

maintenance required under §43.16 and 

91.403 of the Federal Aviation Regulations 

unless an alternative program has been 

FAA approved.”

Rationale: The same basic requirement to 

specify information on airworthiness 

limitations applies to an unmanned 

rotorcraft.

Appendix B 

Airworthiness 

Criteria for 

Helicopter 

Instrument 

Flight

Excluded Summary: This appendix specifies the design and installation requirements for 

operation under instrument flight rules.

Rationale: Out of ConOps scope.

Appendix C –

Criteria for 

Category A

Excluded Summary: This Appendix specifies paragraphs under Part 29 that must be met in 

addition to Part 27 for Category A operation (for multi-engine rotorcraft)

Rationale: Out of vehicle scope.
114

Appendix D 

HIRF 

Environments 

and Equipment 

HIRF Test 

Levels

Modified This appendix specifies the HIRF 

environments and equipment HIRF test 

levels for electrical and electronic systems 

under §27.1317. The field strength values 

for the HIRF environments and laboratory 

equipment HIRF test levels must be 

established (TBD).are expressed in rootmean-square units measured during the 

peak of the modulation cycle.

(a) HIRF environment I is specified in the 

following table:

Table I.—HIRF Environment I

Frequency

Field strength

(volts/meter)

Peak Average

10 kHz-2 MHz 50 50

2 MHz-30 MHz 100 100

30 MHz-100 MHz 50 50

100 MHz-400 MHz 100 100

400 MHz-700 MHz 700 50

700 MHz-1 GHz 700 100

1 GHz-2 GHz 2,000 200

2 GHz-6 GHz 3,000 200

6 GHz-8 GHz 1,000 200

8 GHz-12 GHz 3,000 300

12 GHz-18 GHz 2,000 200

18 GHz-40 GHz 600 200

In this table, the higher field strength 

applies at the frequency band edges.

(b) HIRF environment II is specified in the 

following table:

Table II.—HIRF Environment II

Frequency

Field strength

(volts/meter)

Peak Average

10 kHz-500 kHz 20 20

500 kHz-2 MHz 30 30

2 MHz-30 MHz 100 100

Rationale: Specific requirements for HIRF 

environments and equipment HIRF test 

levels were deleted and a placeholder 

inserted indicating that HIRF environments 

and equipment HIRF test levels need to be 

established for UAS. There is insufficient 

evidence, to date, to establish whether HIRF 

requirements specified in Part 27, Appendix 

D are applicable as is to UAS and to their 

intended operational environments. It is 

possible, given that agricultural UAS are 

expected to fly slow and close to the surface 

that HIRF environments different from 

those for Part 27 rotorcraft may be 

encountered.
115

30 MHz-100 MHz 10 10

100 MHz-200 MHz 30 10

200 MHz-400 MHz 10 10

400 MHz-1 GHz 700 40

1 GHz-2 GHz 1,300 160

2 GHz-4 GHz 3,000 120

4 GHz-6 GHz 3,000 160

6 GHz-8 GHz 400 170

8 GHz-12 GHz 1,230 230

12 GHz-18 GHz 730 190

18 GHz-40 GHz 600 150

In this table, the higher field strength 

applies at the frequency band edges.

(c) HIRF environment III is specified in the 

following table:

Table III.—HIRF Environment III

Frequency

Field strength

(volts/meter)

Peak Average

10 kHz-100 kHz 150 150

100 kHz-400 MHz 200 200

400 MHz-700 MHz 730 200

700 MHz-1 GHz 1,400 240

1 GHz-2 GHz 5,000 250

2 GHz-4 GHz 6,000 490

4 GHz-6 GHz 7,200 400

6 GHz-8 GHz 1,100 170

8 GHz-12 GHz 5,000 330

12 GHz-18 GHz 2,000 330

18 GHz-40 GHz 1,000 420

In this table, the higher field strength 

applies at the frequency band edges.

(d) Equipment HIRF Test Level 1.

(1) From 10 kilohertz (kHz) to 400 

megahertz (MHz), use conducted 
116

susceptibility tests with continuous wave 

(CW) and 1 kHz square wave modulation 

with 90 percent depth or greater. The 

conducted susceptibility current must start 

at a minimum of 0.6 milliamperes (mA) at 

10 kHz, increasing 20 decibels (dB) per 

frequency decade to a minimum of 30 mA 

at 500 kHz.

(2) From 500 kHz to 40 MHz, the 

conducted susceptibility current must be at 

least 30 mA.

(3) From 40 MHz to 400 MHz, use 

conducted susceptibility tests, starting at a 

minimum of 30 mA at 40 MHz, decreasing 

20 dB per frequency decade to a minimum 

of 3 mA at 400 MHz.

(4) From 100 MHz to 400 MHz, use 

radiated susceptibility tests at a minimum 

of 20 volts per meter (V/m) peak with CW 

and 1 kHz square wave modulation with 90 

percent depth or greater.

(5) From 400 MHz to 8 gigahertz (GHz), 

use radiated susceptibility tests at a 

minimum of 150 V/m peak with pulse 

modulation of 4 percent duty cycle with a 1 

kHz pulse repetition frequency. This signal 

must be switched on and off at a rate of 1 

Hz with a duty cycle of 50 percent.

(e) Equipment HIRF Test Level 2.

Equipment HIRF test level 2 is HIRF

environment II in table II of this appendix 

reduced by acceptable aircraft transfer 

function and attenuation curves. Testing 

must cover the frequency band of 10 kHz 

to 8 GHz.

(f) Equipment HIRF Test Level 3. (1) From 

10 kHz to 400 MHz, use conducted 

susceptibility tests, starting at a minimum 

of 0.15 mA at 10 kHz, increasing 20 dB 

per frequency decade to a minimum of 7.5 

mA at 500 kHz.

(2) From 500 kHz to 40 MHz, use 

conducted susceptibility tests at a 

minimum of 7.5 mA.

(3) From 40 MHz to 400 MHz, use 

conducted susceptibility tests, starting at a 

minimum of 7.5 mA at 40 MHz, 

decreasing 20 dB per frequency decade to a 

minimum of 0.75 mA at 400 MHz.

(4) From 100 MHz to 8 GHz, use radiated 

susceptibility tests at a minimum of 5 V/m.
117
REPORT DOCUMENTATION PAGE Form Approved

OMB No. 0704-0188

2. REPORT TYPE 

Technical Memorandum

 4. TITLE AND SUBTITLE

Mock Certification Basis for an Unmanned Rotorcraft for Precision 

Agricultural Spraying 

5a. CONTRACT NUMBER

 6. AUTHOR(S)

Hayhurst, Kelly J.; Maddalon, Jeffrey M.; Neogi, Natasha A.; Verstynen, 

Harry A.; Buelow, Barry; McCormick, G. Frank

 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

NASA Langley Research Center

Hampton, VA 23681-2199

 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Washington, DC 20546-0001

 8. PERFORMING ORGANIZATION

 REPORT NUMBER

L-20611

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NASA

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Unclassified - Unlimited

Subject Category 03

Availability: NASA STI Program (757) 864-9658

19a. NAME OF RESPONSIBLE PERSON

STI Help Desk (email: help@sti.nasa.gov)

14. ABSTRACT

As part of NASA’s Unmanned Aircraft Systems (UAS) Integration in the National Airspace System (NAS) Project, NASA is 

conducting research to investigate airworthiness requirements for UAS performing low-risk commercial operations. The goal 

of the research is to help fill the void in standards needed to certify UAS to operate routinely and safely in the NAS. 

Specifically, a case study was conducted to suggest airworthiness requirements for a midsize unmanned rotorcraft performing 

precision agricultural spraying operations over uninhabited fields. The study considered operations in visual line-of-sight, 

beyond line-of-sight, and in reduced visibility conditions. This report contains research prototypes of some of the 

documentation needed to support airworthiness certification, including a proposed (or mock) type certification basis with 

design and performance criteria for the unmanned rotorcraft, corresponding rationale, a concept of operations, and a hazard 

list.

15. SUBJECT TERMS

Aircraft reliability; Certification; Line of sight; Spraying; Systems integration; Visibility

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128

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(757) 864-9658

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