Ms. Margaret Gilligan October 24 , 2013

Associate Administrator for Aviation Safety
Federal Aviation Administration 800 Independence Avenue Washington, DC 20591

Mr. David Grizz le Chief Operating Officer for Air Traffic Organization
Federal Aviation Administration 800 Independence Avenue Washington, DC 20591

Dear Ms

. Gilligan and Mr. Grizzle

The Unmanned Aircraft System s Aviation Rulemaking Committee (UAS ARC) is pleased to
submit the enclosed recommendations for inclusion of UAS language into 14 CFR § 91.113 (b) for your consideration . This body of work represents the UAS ARC’s 91.113 Working Group
evaluation and review process . This team is made up of subject matter experts from within both the UAS community and the great er aviation community at large.

The 91.113 Working Group assessed terminology currently published in 14 CFR as well as other

FAA and ICAO publication s for inclusions in this work. They also leveraged the UAS ARC’s Terminology and C lassification Action Team ’s (TCAT) recommendations. Whenever possible, they reviewed and update d existing t erminology to better represent the current state of the

UAS terminology nationally and internationally

.

The UAS industry will benefit from the FAA’s formal recognition of the UAS ARC ’s 91.113
recommendations for UAS Detect and Avoid language . This recognition will facilitate the operational use of UAS in the NAS a nd be the cornerstone for regulatory work on Detect and
Avoid

.

The UAS ARC appreciates your continued support of its activities and invites you to discuss any aspects of these recommendations at your earliest convenience. The UAS ARC respectfully
requests the FAA to provide us wit h a formal response. T he members and constituents of UAS

ARC will support FAA actions to develop and implement this recommendation.

Sincerely,

Robert Scott Dann
Chairman Unmanned Aircraft Systems Aviation Rulemaking Committee1



# Unmanned Aircraft System (UAS)

A viation Rulemaking Committee ( ARC )

Part 91 Working Group

Recommendations for 14 CFR 91.113 on Right of Way Rules for Unmanned Aircraft

August 20132



### Table of Contents

1. Overview

................................ ................................ ................................ ................................ ................. 3

2. Background

................................ ................................ ................................ ................................ ............. 3

3. Discussion

................................ ................................ ................................ ................................ ................ 4

4. Definitio ns

................................ ................................ ................................ ................................ ............... 6

5. References

................................ ................................ ................................ ................................ ............... 7

6. Acronyms

................................ ................................ ................................ ................................ ................. 73



### 1. Overview

The Federal Aviation Administration ( FAA ) currently requires a Certificate of Waiver or Authorization (COA) for public , civil, or commercial Unmanned Aircraft System (UAS) operations in the National Airspace System (NAS)

. 1 These special authorizations are required , at least in
part because 14 CFR 91 rules were written for aircraft with a pilot in the cockpit onboard the
aircraft. Specifically § 91.113 discusses right

- of

- way rules

, and requires vigilance to be
maintained by each person operating an aircraft so as to “ s ee and a void ” other aircraft. The

UAS ARC Part 91 Working Group recommend s the addition of a sentence under Part 91 Subpart

B

— Flight Rules § 91.113 (b) that specifically addresses UAS. The recommended language is (underlined language is new):

Part 91 Subpart B

— Flight Rules § 91.113 (b) General. When weather conditions permit, regardless of whe ther an operation is conducted under instrument flight rules or visual flight rules, vigilance shall be maintained by each person operating an aircraft so as to see and avoid other aircraft , except as noted in paragraph (b)(1) of this section

. When a rule of this section gives another aircraft the right

of

- way, the pilot shall give way to that aircraft and ma y not pass over, under, or ahead of it
unless well clear. (1) For a UAS, vigilance shall be maintained so as to detect and avoid other aircraft.



### 2. Background

The guiding principles provided to the Part 91 WG by the UAS ARC steering group in development of this new language were to maintain the current level of safety in the NAS and to not impact the interpretation of the current language for manned aviation . The steering

group acknowledged that some reference to a new exception may be required in § 91.113 (b)

, but directed that no other deletion, modification

, or additional words to the existing § 91.113 (b) be made

. Adding the reference to the end of the first sentence reduces any confusion that the exception in § 91.113 (b) (1) only applies to the first sentence, and the second sentence would apply to all aircraft including UAS. The intent of th e new rule language i s to enable an alternate means of compliance without requiring an exemption to the current rule . Th e steering group also advised the WG that the new rule must apply to all classes of airspace, and
that it should enable technology expansion without requiring future rule revisions. To focus the

WG on this first phase, the steering group directed attention to the portion of the paragraph that states “vigilance shall be maintained by each person operating an aircraft so as to see and
avoid other aircra ft” in association with both avoid ing collisions and remaining well clear. The

WG will look to address other portions of § 91.113 and other Part 91 rules in the second phase.

All WG members agree to this approach ; however, there is some difference of opinion on the specif ic words and definitions to be used. The WG attempted to keep the changes simple so as to minimize addition of new terms and definitions, but to ensure the language satisf ies the guiding principles provided by the steering group. The WG recognizes this is a recommendation4

to the FAA and is not th e final rule, so every attempt is made to capture in this paper the
rationale for all options and alternatives.



### 3. Discussion

In the existing language of § 91.113 (b)

, the first part of the paragraph references “ when weather conditions permit, regardless of whether an operation is conducted under instrument flight rules or visual flight rules

. ” All WG members agreed that the new § 91.113 (b) (1) specific to UAS would omit this language with the rationale that the individual UAS operations manual would specify under what weather conditions the UAS could operate. This position was reinforced by feedback from the steering group

.

For the new s entence, a term is needed to identify the type of aircraft the new rule applies to.
The two terms in prevailing use today are “ Unmanned Aircraft System ( UAS ) ” and “ Remotely Piloted Aircraft System (RPAS). ” There was about a 50/50 split within the WG on whether to
use the term s UAS/UA or RPAS/RPA. The WG’s discussion of these terms and an option for avoiding both terms is summarized below . In addition, an alternative sen tence in l ieu of the
recommend ed sentence is provided for each term.

a) The term “ UA/UAS ” is described in the FAA Modernization and Reform Act of 2012, which states, “The term ‘unmanned aircraft’ means an aircraft that is operated without the possibility of direct human intervention from within or on the aircraft. The term
‘unmanned ai rcraft system’ means an unmanned aircraft and associated elements (including communication links and the components that control the unmanned aircraft) that are required for the pilot in command to operate safely and efficiently in the national airspace sy stem

. ” 2 UAS is the more encompassing term that allows for various levels of automation. By using the term UAS in the language now, we allow for technology expansion and preclude having to re

- write the r ule if autonomous aircraft are accepted at some point in the future

. E very U A will be under some level of

automation

, which must be included in the UAS definition . As automation increases,
the balance of flight operation duties shift s from the pilot to the UAS

. The FAA UAS Concept of Operations Version 2.0 uses the term UAS, but also states the p ilot in

c ommand will have full control or override authority to assume control at all times during normal operations and that routine autonomous operatio ns are not permitted. In addition, the UAS ARC Terminology and Classification Action Team ( TCAT )
recommended UAS as an over

- arching term that includes both RPAS and autonomous
aircraft

. The recommended rule language would allow for future expansion of UAS

automation

. An alternative to the recommend ed rule language would be to add the following words : “by each person operating a UA

. ” This alternative would focus the rule
on the requirement of the pilot to r emain vigilant

, but may limit future expansion. (1) For a UAS, vigilance shall be maintained by each person operating a UA so as to detect and avoid other aircraft.5

b) The term “ RPA/RPAS ” is defined in the International Civil Aviation Organization ( ICAO )

Annex 2

. For “ RPA ” the definition is : “An unmanned aircraft which is piloted from a remote pilot station

. ” 3 The term “ RPAS ” is defined as : “ A remotely piloted aircraft, its associated remote pilot station(s), the required command and control links and any other components as specified in the type desig n

. ” 3 These definitions make clear the
involvement of a pilot . This involvement may include some supervisory role even if the aircraft performs some lower

- level automation which the pilot only oversees. The ICAO

defined R PAS term is now widely accepted on a global basis

. Focusing the rule change on RPAS, which always involves a pilot

, may expedite the FAA’s rulemaking process. Broadening the scope of the rule to UAS which includ es autonomous aircraft may complicate the approval process. The UAS ARC Terminology and Classification Action Team (TCAT) in Aug ust 2012 recommended the ICAO Circular 328 term RPA to make clear the involvement of the pilot and harmonize with the in ternational community.
ICAO Circular 328 define d RPA as: “An aircraft where the flying pilot is not on board the
aircraft. Note : This is a subcategory of unmanned aircraft.” 4 An alternative to the
recommend ed rule language using the term RPA/RPAS would focus solely on the p ilot in

c ommand and not allow for expansion to autonomous aircraft. (1) For a RPAS, vigilance shall be maintained by each person operating a RPA so as to
detect and avoid other aircraft.

c) T o avoid the issue of using UAS or RPA S

, the WG discussed an alternative to describe the

intent. The intent of the WG is that the UAS , including when possible the UAS pilot

, must maintain vigilance so as to detect and avoid other aircraft. (1) Aircraft without the pilot in command onboard shall maintain vigilance so as to detect and avoid other aircraft.

No matter which term is used, the loss of the command and control (C2) link will require an
automated mode for safe UAS operation. The c onsensus of the WG was that a significant loss
of the C2 link (definition and criteria to be determined in Phase 2) is considered an emergency
condition and is covered under § 91.113 (c) “In distress

. An aircraft in distress has the right

- of

way over all other air traffic. ” Subpart B of Part 91 is focused on the pilot ’s responsibility and Subpart C of Part 91 is focused on the equipage. Therefore

, the topic of lost C2 link must be addressed in another section of Part 91, if it is not already adequately addressed in § 91.113 (c).

The other part of the paragraph that need s to be addressed is the word “ s ee” in the phrase

“ s ee and a void” in the existing § 91.113 (b). S everal words , including “sense”, “detect”, and “be
aware of” were considered as substitute for the word “ s ee

. ” The WG members all agreed on
the term “detect” as the best word to use

. The rationale for this word choice is summarized
below in Section 4.6



### 4. Definitions

There is additional work in Phase 2 of this WG to include definitions of the terms introduced in this paper , but we wanted to include the discussions of the WG and the intent of the terms
used

. Though the WG agreed on the term “detect and avoid

, ” there was a split on how the

term should be defined in the glossary (i.e.

, not included in § 91.113 (b)), which can then be
referenced in § 9 1.113 (b) as well as other portions of 14 CFR Part 91.

The recommended definition is “ D etect and avoid is the capability to see, sense or detect other aircraft and take the appropriate action to remain well clear from and to avoid
collisions with other aircraft

. ”

The WG agreed that “s ee and a void” mean s more than collision avoidance, so the new term
must work for other functions such as maintaining situational awareness and determin ing right
of way. The WG also agreed that the definition chosen should be harmonized with the terms used by RTCA SC

- 228, esp ecially if avoiding other hazards is included in the definition.

However

, half the WG believes we should directly adopt the ICAO language and show alignment with the international community while the other half prefers to modify the ICAO language replacin g the phrase “conflicting traffic or other hazards” with simply “other aircraft” and add specific actions.

The definition in ICAO Annex 2 is : “ The capability to see, sense or detect conflicting traffic or other hazards and take the appropriate action. ” 3

Based on the Sense and Avoid (SAA) for UAS Workshop report

, the WG agreed on the intent of
the definition for SAA. The definition is: “ SAA is the capability of a UA to rema in well clear from
and avoid collisions with other airborne traffic. SAA is the combination of UAS Self

- Separation plus Collision Avoidance as a means of compliance with 14CFR Part 91, §91.111 and §91.113.” 5

This brings into discussion three topics to consider for the definition of “detect and avoid

. ” In
the general glo ssary definition :

a) Does a ll traffic need to be detected, or just the conflicting traffic ? The new proposed

sentence in § 91.113 (b) (1) states “to detect and avoid other aircraft” where the last two words are a direct lift from the existing language in §91.113 (b). Therefore

, the current language does not limit this funct ion to only those aircraft in conflict. The WG’s

r ecommendation is to use the term “other aircraft

. ”

b) Should the UAS just avoid aircraft or other hazards (e.g.

, ground obstacles) as well ? The current language in § 91.113 (b) does not specify the need to detect and avoid other
hazards. The WG’s r ecommendation is to not include “other hazards” in the definition.

c) Do we leave open to interpretation what the appropriate action for the avoidance maneuver is, or should we furth er define the actions to be taken? The ICAO initially7

established ICAO Circular 328 in 2011 prior to the approval of the Annex 2 language that had the additional, “ and take the appropriate action to comply with the applicable rules of flight. ” 4 The WG’s recommendation is to specify avoidance actions in relation to remaining well clear and avoiding collisions recognizing the definition may have to be
modified later if the term “detect and avoid” is to be used elsewhere in Part 91 . This also aligns with the guidance provided by the steering group.



### 5. References

1 FAA NOTICE N 8900.227, 30 Jul 2013.

2 FAA Modernization and Reform Act of 2012, 14 Feb 2012

. 3 International Standards, Annex 2 to the Convention on International Civil Aviation, Tenth Edition July 2005 Amendment 43, 15 Nov 2012.

4 International Civil Aviation Organization Circular 328, Mar 2011.

5 Sense and Avoid (SAA) for Unmanned Aircraft Systems (UAS) Workshop report, 9 Oct 2009.



### 6. Acronyms

ARC Aviation Rulemaking Committee

COA Certificate of Waiver or Authorization

FAA Federal Aviation Administration

ICAO International Civil Aviation Organization

NAS National Airspace System

RPA Remotely Piloted Aircraft

RPAS Remotely Piloted Aircraft System

TCAT Terminology and Classification Action Team

UA Unmanned Aircraft

UAS Unmanned Aircraft System

WG Working Group