OK-09-3468

Part23–SmallAirplane

CertificationProcessStudy

RecommendationsForGeneral

AviationForTheNext20Years

July2009
Part 23 – Small Airplane 

Certification Process Study 

A life-cycle study which assesses the 

cumulative certification experience and 

makes recommendations for the next 

twenty years. 

July 2009 

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Table of Contents

Executive Summary................................................................................................................... 6 

Background.................................................................................................................................. 6 

Summary of the Findings and Recommendations ....................................................................... 6 

Continued Airworthiness ............................................................................................................. 7 

Data Management ........................................................................................................................ 8 

Pilot Interface............................................................................................................................... 9 

Introduction.............................................................................................................................. 10 

Background................................................................................................................................ 10 

Team Objective.......................................................................................................................... 12 

Team Approach.......................................................................................................................... 13 

1. Structure and Process of part 23 ................................................................................... 14 

1.1 Finding 1.1 ........................................................................................................................ 14 

2. Design Certification ........................................................................................................ 30 

Overview ................................................................................................................................... 30 

2.1 Finding 2.1 ........................................................................................................................ 30 

2.2 Finding 2.2 ........................................................................................................................ 33 

2.3 Finding 2.3 ........................................................................................................................ 34 

2.4 Finding 2.4 ........................................................................................................................ 34 

2.5 Finding 2.5 ........................................................................................................................ 36 

2.6 Finding 2.6 ........................................................................................................................ 36 

2.7 Finding 2.7 ........................................................................................................................ 36 

3. Continued Airworthiness ............................................................................................... 38 

Overview ................................................................................................................................... 38 

3.1 Finding 3.1 ........................................................................................................................ 39 

3.2 Finding 3.2 ........................................................................................................................ 42 

3.3 Finding 3.3 ........................................................................................................................ 42 

3.4 Finding 3.4 ........................................................................................................................ 43 

3.5 Finding 3.5 ........................................................................................................................ 43 

3.6 Finding 3.6 ........................................................................................................................ 44 

4. Data Management........................................................................................................... 46

Overview ................................................................................................................................... 46 

4.1 Finding 4.1 ........................................................................................................................ 47 

4.2 Finding 4.2 ........................................................................................................................ 48 

4.3 Finding 4.3 ........................................................................................................................ 48 

4.4 Finding 4.4 ........................................................................................................................ 49 

4.5 Finding 4.5 ........................................................................................................................ 50 

4.6 Finding 4.6 ........................................................................................................................ 51 

5. Pilot Interface.................................................................................................................. 52 

Overview ................................................................................................................................... 52 

5.1 Finding 5.1 ........................................................................................................................ 52 

5.2 Finding 5.2 ........................................................................................................................ 63 

Conclusions............................................................................................................................... 65 

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Appendix A - Team Members................................................................................................... 66 

Appendix B - Charter ................................................................................................................ 67 

Appendix C - Suggested Expansion Subjects for 14 CFR 21.3 Requirements ......................... 70 

Appendix D - Accidents Supporting the Pilot Interface Recommendations............................. 75 

Appendix E - List of Acronyms ................................................................................................ 87 

5 
Executive Summary

Background 

The primary objective of the part 23 Certification Process Study (CPS) was to assess the 

adequacy of the current airworthiness standards throughout a small airplane’s service life while 

anticipating future requirements. Working groups comprised of various members of the aviation 

industry were assigned to the five areas of this study to identify issues and develop 

recommendations. The study was not limited to certification standards; study team members 

reviewed other topics affecting general aviation including pilot training, operations, and 

maintenance. 

The study offers a variety of short-term and long-term recommendations. These 

recommendations will serve as the basis for a part 23 regulatory review (currently scheduled for 

FY10). It has been over 20 years since the last part 23 regulatory review. Not only is it time for a 

complete review of part 23, it is also time to review the original assumptions for part 23, 

including operations and maintenance. The airplanes being certified today have changed 

significantly since the inception of part 23 and this evolution will likely continue. 

Summary of the Findings and Recommendations 

Performance Based Standards for part 23 

This section of the report addresses performance-based standards for part 23 airplanes. Part 23 

currently differentiates airplane requirements based on engine type and airplane weight which 

does not address the operational capabilities of today’s high-performance small airplane. 

Historically, part 25 airplanes had technologies that for cost and weight reasons were not 

practical for part 23 airplanes. Smaller part 23 airplanes were typically simple and slow while 

bigger airplanes were more complex and faster. Consequently, the existing approach to standards 

based on weight and engine type was effective. While the existing approach has produced safe 

airplanes for decades, technological advances have changed the original assumptions of the part 

23 divisions. The new small turbine engines, composite airframes, and lightweight digital 

electronics offer part 23 airplanes the operational capability and performance of traditionally 

larger part 25 airplanes. Part 23 standards have evolved beyond their original intent to address 

the increasing performance and complexity. Unfortunately, the slow, simple part 23 airplanes 

have suffered as the standards have shifted towards more complex airplanes. These findings led 

to two major recommendations: 

• Reorganizing part 23 based on airplane performance and complexity versus the 

existing weight and propulsion divisions. 

• Rewriting certification requirements for part 23 airplanes as a top level regulation 

with more detailed implementation methods defined by reference to industry and 

government standards. 

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Design Certification 

This section describes the challenges in meeting procedural requirements for the issue of type 

certificates. It also addresses changes to those certificates and changes affecting the type design 

of type-certified products and aviation articles like avionics. 

The bulk of this section and the associated recommendations address the challenges of keeping 

older airplanes operating safely. This includes upgrading airplanes with better systems (e.g., 

alternators), newer avionics (e.g., NextGen, navigation, information, or redundancy), and safety 

gear (e.g., ballistic parachutes and inflatable restraints). A parallel set of recommendations 

address maintenance of new equipment that the original manufacturer never envisioned being 

installed on their airplane. 

The recommendations from this section include but are not limited to the following: 

• Updating the Approved Model List (AML) Supplemental Type Certificate 

(STC) process to include system interface considerations. 

• Developing training for the AML/STC process. 

• Replacing equipment for “part 23 required equipment” as “approved” 

equipment. 

• Defining major/minor alteration criteria. Developing a regulatory approach to 

evaluate changes to the type design consistent for part 21 though part 43. 

Continued Airworthiness 

This section addresses problems associated with airframes staying in service for half a century or 

more. Considering lengthy service lives, what needs to be done for composites, life-limited parts, 

and increasingly integrated electronic airplanes? A growing concern for owners of older 

airplanes involves knowing the service history of parts and components that are sold as 

airworthy. Few parts have life-limits and even fewer small airplane parts have in-service hours 

tracked. Existing rules and guidance for the maintenance of part 23 airplanes do not account for 

the actual age of the airplanes and how the maintenance needs change as the airplanes age. 

Furthermore, human performance is a dominant factor in general aviation accidents. Accident 

data historically shows that human performance that includes operators and maintenance 

personnel attribute to 70 percent to 80 percent of general aviation (GA) accidents. Updating 

older airplanes with new equipment can address some of these human performance issues, but 

the FAA needs a vehicle to make addressing the thousands of modifications necessary to the 

aging fleet of 200,000 GA airplanes easier. The recommendations from this section include but 

are not limited to the following: 

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• Revising CFR part 23 to include requirements that consider degradation of 

airplanes, airplane parts, and airplane systems in the Instructions for 

Continued Airworthiness (ICA). 

• Issuing policy that would allow the use of accepted industry or government 

standards (ASTM, DOT, etc.) in an alternation or modification of a product 

that exceeds the original standards created under CAR 3. This policy would 

also accept the declaration of the material manufacturer with regard to the 

accepted standard. 

• Amending 43.15 to create a hierarchy for the maintenance data used to 

maintain part 23 airplanes. 

• Reducing repair and modification mistakes by improving the clarity and 

usability of all technical documentation. 

Data Management 

This section focuses on existing data management tools and our involvement in their evolution. 

The Data Management working group built on several existing data efforts. A major safety 

concern is that the average fleet age for part 23 airplanes is already over 40 years old. 

Furthermore, as newer airplanes age, they will include technologies we have no long term 

experience maintaining. These technologies include composite airframes and integrated avionics 

and engine controls that use large numbers of microprocessors. The Service Difficulty Reporting 

(SDR) program needs improvement. Currently, this program has limited success. Unfortunately, 

it was built when technology in aviation was limited. So today, many new critical areas need to 

be added where problems should be reported. 

Additionally, one of the important elements of the FAA Safety Management System (SMS) 

effort is developing better tools to conduct Continued Operational Safety (COS) tasks. The 

Monitor Safety Analyze Data (MSAD) team designed an application to address this need. The 

MSAD tool relies upon various databases such as the SDR database for both maintenance and 

operational in-service data to perform quantitative-based analysis to determine the level of risk 

and appropriate mitigation actions. This requires a more progressive approach to data collection 

and management. The recommendations in this section include greater involvement with these 

and evolving programs. 

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Pilot Interface 

This section addresses sharing information with pilots from both the airplane certification and 

the training and operations disciplines. The Pilot Interface working group was composed of 

representatives from the flight test, flight operations, and flight training segments of the industry 

and FAA. 

As the findings show, this working group uncovered several disconnects between the 

certification and operations world. The recommendations address how to share more pertinent 

information from the flight test process with pilots. The intent is to increase pilot awareness of 

the data provided through flight testing to ensure pilots understand the information and its 

limitations. The recommendations from this section include but are not limited to the following: 

• Clarifying between FAA Aircraft Certification Service (AIR) and Flight 

Standards Service (AFS) the understanding of one engine inoperative (OEI) 

climb performance development and how it is conveyed during training in 

weight/altitude/temperature (WAT) performance limited airplanes. 

• Agreeing on explanatory language between FAA Flight Standards, flight test, 

and structures for pilots to understand published speeds and what protection is 

actually available to the pilot when complying with these airspeeds. 

• Requiring pilot type training to include landing experience on minimum field 

length runways, preferably in the simulator, and expose pilots flying small jets 

to landing on both minimum dry field length and contaminated runways. 

• Re-emphasizing the difference between stall warning and aerodynamic stall. 

Pilots may fly an airplane for years and never stall the airplane or even feel 

the stick pusher. Most small airplanes can not recover from an actual stall 

without pushing the nose down and flying out, which is not currently 

emphasized in type training. 

a. Current FAA training focuses on maintaining pitch attitude and adding power. 

b. Even in high-performance jets, there may be some parts of the envelope where the 

airplane will not recover from the stall with power only. 

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Introduction

This objective of this study was to 

assess, from the part 23 certification 

perspective, the adequacy of the 

current airworthiness standards 

throughout a small airplane’s service 

life. The study was not limited to 

certification standards; study team 

members reviewed other topics 

affecting general aviation, such as 

pilot training, operations, and 

maintenance. 

Courtesy of EAA Background 

Historically, the FAA has hosted regulatory reviews for 14 Code of Federal Regulations (CFR) 

part 23 about every 10 years. The two most recent reviews of part 23 were performed in 1974 

and 1984. In 1990, a regulatory review was done in conjunction with a harmonization program 

between the FAA and the European Joint Aviation Authorities (JAA). It has been over 10 years 

since the last review of part 23. During the preliminary discussions of the part 23 Certification 

Process Study (CPS), it became clear that it is also time to review the original assumptions for 

the basis of part 23, with particular emphasis on operations and maintenance. 

In 2006 there was a meeting between the Small Airplane Directorate and operators of historic 

military airplanes. Some of these airplanes were used in simulated combat maneuvering and had 

suffered several in-flight breakups. It became apparent from this meeting that operators of these 

airplanes did not have a clear understanding of how a certified airplane is designed and how it is 

impacted by fatigue. One operator stated that if the airplane structure was designed for 6Gs, then 

they could “pull 6Gs” all the time, on every flight. The operator had no knowledge of the 

cumulative effects of G-loading on airframe fatigue. This meeting became the impetus for the 

part 23 study. 

This meeting showed a need to evaluate the connection between general aviation airplane 

certification, operation, and maintenance. One task was to identify major “myths” between the 

different areas of certification, maintenance, and operations. For this effort, the team defines 

myths as widespread misunderstandings about how something is done. For example, actual 

structural safety margins versus the certified limits or parts life. Not all CAR 3/part 23 airplane 

structures are designed using the same approach. CAR 3 or older airplanes may have more 

“margin” in their structure than new part 23 airplanes. All three areas overlap and are 

interconnected and that’s where the team started looking for the myths. 

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Maintenance 

Certification Operations 

A similar study for Transport Category airplanes was completed in 2002. This study focused 

only on transport airplanes in part 121 air carrier operations. While that study contained 

valuable findings, many were not applicable to the diverse operations of the general aviation 

community: 

• Owner-flown airplanes to rental fleet airplanes to commercial operations 

• Vintage airplanes to advanced turbojet powered airplanes 

• Private pilots to airline transport pilots with type ratings 

• Small repair shops to large service centers 

• Round dial instruments (steam gauges) to glass cockpits with synthetic vision 

systems 

Beyond the existing fleet, the study team reviewed part 23 airplanes (from a top level 

perspective) and made recommendations based on current and expected future products. 

Specifically, the study team was challenged to determine the future of part 23, given today’s 

current products, and anticipated products twenty years from now. This type of forward 

thinking led to one of the major recommendations from the study: restructure part 23 into 

performance and complexity based divisions. 

This study includes a review of the complete life cycle of part 23 airplanes; including all the 

airplanes in the same weight range that part 23 covers. Airplanes built under the predecessor 

regulations such as CAR 3 are the certification basis for the bulk of the existing GA fleet. 

This report uses the term “part 23” to include all GA airplanes in the same class as those 

covered by part 23. When CAR 3 standards were adopted by the Civil Aeronautics 

Administration, airplane construction methods and operations were narrowly focused; 

likewise, their performance parameters were narrow. As aviation technology progressed, 

construction methods, performance, and complexity have evolved. The Normal, Utility, 

Acrobatic, and Commuter categories have seen remarkable advances in capability, from the 

modern day Legend Cub skimming the wheatfields all the way up to the flight levels in a 

Cessna Citation CJ4. 

 

The 2008 Nall Report indicates the total number of accidents in small airplanes in the United 

States has been on a downward trend since 1998. Additionally, the number of fatal accidents 

has also decreased during this time. The Aircraft Owners and Pilots Association (AOPA) 

Air Safety Foundation’s Technically Advanced Aircraft (TAA), Safety and Training Report 

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shows that the use of new cockpit technologies can further reduce the accident rate. The 

report states that, “TAAs have proportionately fewer accidents compared to the overall GA 

fleet. TAA have experienced reductions in the percentage of takeoff/climb, fuel management, 

and maneuvering accidents, but increases in landing, go-around and weather crashes, as 

compared to the fleet.” For example, no TAA airplanes have had accidents related to fuel 

management. Many TAA airplanes incorporate the use of a low fuel light or fuel range ring 

that displays information directly in front of the pilot. This is just one example where the 

incorporation of technology increases safety. 

Even with current improvements in 

small airplane safety, the FAA 

believes that further safety gains 

may come from examining the 

overall processes applied during 

the airplane’s lifespan and evaluate 

how these activities interrelate 

with in-service operation and 

maintenance of the airplane. As the 

US GA fleet passes an average age 

of 40 years, the processes for 

continued airworthiness will 

become more important. Also, 

almost all new airplane designs incorporate all electric, integrated systems using databus 

architectures. These airplanes will challenge traditional airplane maintenance, training, and 

modifying practices. 

This review, intended as a separate but complimentary effort to Safer Skies, studied the 

processes and procedures that are currently being applied during the various activities 

associated with the airplane airworthiness programs. The team also examined how these 

activities interrelate to the maintenance and operation programs (including training) applied 

in service. 

Team Objective 

The objective of this team was to assess the adequacy of the various operations and 

airworthiness processes currently in place throughout the airplane’s service life, and, if 

appropriate, to identify opportunities for process improvements. 

The team has: 

• Made recommendations for long-term improvements; and 

• Encouraged implementation of near-term, easy to address improvements 

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Team Approach 

This study started with a request for support from both industry and FAA organizations 

representing certification, maintenance, and operations. There was substantial support from 

the different organizations. The effort started with a brainstorming session of the specific 

issues the team members experienced in their respective areas. The team grouped the specific 

issues into categories. These categories, with some refinement, became the major sections of 

this report. 

A working group was established for each category and members were asked to volunteer for 

the working group where they felt they could contribute. In many cases, team members were 

on more than one working group. Each working group compiled their list of issues refining 

them into findings. In addition to representing their own organization’s interests (such as 

avionics installations), the team members brought significant personal experience to the 

study as mechanics, engineers, pilots, instructors, and airplane owners. Thus, it was natural 

that working groups used personal experience as well as interviews, accident studies, and 

surveys to make their findings and recommendations. Over a two-year timeframe, there were 

five face-to-face meetings. In addition to the meetings, the use of telecoms, same-time 

meetings, and internet document exchange ensured that the objectives were met. 

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1. Structure and Process of part 23 

1.1 Finding 1.1 

The structure of part 23 is inadequate for today’s airplanes. In the last several decades 

the part 23 standards have been continuously challenged with the scope of new product 

designs for a number of basic reasons: 

• The products within part 23 have increased to include the widest variation of 

airplanes than any other airplane design certification regulation in the FAA. 

• Part 23 airplanes see the majority of new technologies introduced into 

aviation first. 

• The FAA is only able to promulgate a small number of new regulations each 

year; rulemaking priority favors large transport airplanes (part 25), making 

part 23 rulemaking difficult. 

Courtesy of EAA 

Issue: In order to align part 23 with the broad spectrum of products it reflects and also 

to assure it can remain current, a strategic change to the structure of part 23 is 

appropriate. Sub-dividing part 23 into tiers based upon complexity and performance 

allows the FAA to issue targeted regulations appropriate for each class of airplane. 

Such subdivisions would also allow the FAA to focus oversight on higher performance 

and complex products. This concept would be aligned with risk-based resource 

targeting. 

An additional benefit of 

a tiered structure is the 

ability to leverage the 

industry and 

government standards 

approach for simple 

part 23 airplanes. 

Because so much new 

technology is 

introduced in part 23, a 

structure which can 

leverage industry and 

government standards 

to address new 

technologies as they 

come along alleviates the need for regulating by special conditions and issue papers. 

The FAA would be responsible for the acceptance of the industry and government 

standards, and it would maintain control of certification requirements while leveraging 

the skill and knowledge of the aviation community to develop new methods of 

compliance. 

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Because of high FAA regulatory workload and the diversity of airplanes, systems, and 

components there is an unacceptable burden on many segments of the part 23 

community. To address this certification environment the FAA has relied upon special 

conditions and issue papers to assure safety is maintained in light of regulations that 

have not kept up. But these processes add significant administrative burden to FAA 

staff and applicants alike. A consequence of the difficult regulatory environment has 

been the high cost of certification and a corresponding reduction of new entry level 

products within part 23. 

1.1.1 Recommendation – Reorganize part 23 based on airplane performance and 

complexity verses the existing weight and propulsion divisions. 

1.1.2 Recommendation – Certification requirements for part 23 airplanes should be 

written on a broad, general and progressive level. A team should determine the 

exact number of tiers and which complexity and performance divisions to use 

for segmenting them. 

A. A first tier should contain the requirements for low complexity, 

low-performance airplanes and it should act as a basic starting point for all 

other categories. These basic requirements could be general with 

compliance methods maintained in industry and government standards 

referenced by regulation or policy. The simple product category would 

naturally fall in a lower oversight risk category allowing the FAA to 

perform more oversight on products in more complex, higher performance 

tiers. 

B. The next tier incorporates by reference the requirements of the previous tiers 

and adds unique requirements for medium-complexity, mediumperformance airplanes. These requirements could also be general with 

compliance methods maintained in industry and government standards that 

are referenced by regulation or policy. The next product category would 

naturally fall in a mid oversight risk category which would require a 

moderate level of oversight. 

C. A highest tier incorporates by reference all of the requirements of the 

previous tiers and adds unique regulatory requirements for high-complexity, 

high-performance airplanes. While this tier could leverage industry and 

government standards, this tier would also allow regulations to attain a level 

of priority and reliance on more specific regulations. The highest product 

category would naturally fall in an elevated oversight risk category that 

would require an increased level of oversight as compared to the more 

simple categories. The standard of care for attention to human factors 

related to maintenance and operation also increases as the tier increases. 

1.1.3 Recommendation – Coordinate this proposal internationally with aviation 

regulators to assure it becomes a global standard for the design and certification 

of airplanes weighing 19,000 pounds or less. 

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1.2 Background 

Part 23 evolved from bulletin 7A followed by Civil Airworthiness Regulation 3. 

Bulletin 7A (1934) states “These requirements are based on the present development 

in the science of airplane design. Experience indicates that, when applied to 

conventional types of construction, they will result in airworthy and well proportioned 

airplanes.” The intent of today’s requirements is exactly the same as they were in 1934 

as stated by bulletin 7A. However, over the last decade the science of airplane design 

has outpaced the current requirements. Additionally, in the 70 years since bulletin 7A 

the regulations have continually become more prescriptive in reacting to specific 

design features of the day. The result of the combination of all of these specific rules is 

the loss of the original intent of airworthiness design regulations and a lack of 

flexibility to quickly address today’s airplanes. 

The DC-3 is frequently considered the first production transport airplane. It seated 21 

passengers and had a gross weight of just over 25,000 pounds. During the same era, 

the largest “light twin,” the Beech 18, weighed about 8,000 pounds fully loaded. 

Legend has it that the originators of CAR 3 selected a reasonable weight division of 

13,000 pounds that was roughly between what they considered the largest “small” 

airplane and the smallest “large” airplane. Because 13,000 pounds is an ‘unlucky 

number’ legend goes on to say the originators of CAR 3 selected 12,500 pounds as a 

division point. Whether this legend is accurate or not it has merit in its illustration that 

the division of products by weight may make sense when looking at existing products, 

but the approach loses validity as products evolve beyond what was envisioned. 

In the 40 years following this division of regulations some basic changes came to 

airplane and engine design. Fuselages transitioned from simple tube and fabric designs 

to engineered semi-monocoque aluminum, reducing drag and improving durability and 

maintainability. Engine technology transitioned from radial to horizontally opposed 

designs, significantly reducing drag and weight as well as increasing the reliability of 

airplane propulsion. 

In the 1970’s, a new airplane emerged for the airline feeder routes. That airplane was 

the 19-passenger turboprop. The decision was made to use the certification standards 

for this new class from part 23, supplementing many sections with part 25 Special 

Federal Airworthiness Regulation (SFAR) requirements. After several SFAR 

documents, this new set of “commuter” requirements ultimately ended up in part 23 as 

the commuter category. This was essentially the last fundamental change to the 

regulations and resulted in the part 23 that exist today. From the 1930s to the 1980s the 

basic regulations for airplanes weighing equal to or less than 19,000 pounds have 

served the industry well. 

In 1984 the last part 23 regulatory review was conducted with participation from 

industry. During the time between the regulatory review and the issuance of regulatory 

changes to part 23, the industry experienced a significant downturn and as a result, 

16 
there was limited participation from industry as the recommendations were developed 

into proposed regulations and promulgated into final rules. 

Between 1994 and 1996, approximately 800 rule changes to part 23 were enacted. The 

rule changes ranged from corrections, to harmonization with European rules, to rules 

that addressed new technologies of the time. While these changes addressed the needs 

of more sophisticated part 23 airplanes, they made it more costly to certify a simple 

airplane. Essentially the regulatory scope of part 23 has been shifted to more directly 

address the complex airplanes to the detriment of simple airplanes. The following 

chart illustrates the increased introduction price and corresponding lack of new 4-seat 

entry-level airplanes introduced in the past few decades. There are certainly other 

factors that have driven up the price; however the increased difficulty of certifying 

new entry-level airplanes is clearly one of them. 

In the past two decades, airplane construction, engine design and the expanded use of 

non-mechanical systems has exponentially increased the availability of lightweight 

and relatively low cost technology in part 23 airplanes. General Aviation (GA) is 

seeing fast piston airplanes, slow turbine airplanes and simple single-engine jets, etc. 

As a result the weight and propulsion assumptions used throughout part 23 which have 

carried us through the first 50 years of flight don’t hold true for today’s designs. While 

inefficient, through the selective use of special conditions, issue papers and other 

policy, the FAA has provided an acceptable level of safety as verified by service 

experience. It is time to assure the design standards, from the simplest to the most 

complex, “are based on the science of airplane design” as bulletin 7A so eloquently 

stated. 

17 
1.3 High-Level Structural Issues with part 23 Code 

A number of factors have resulted in part 23 becoming increasingly misaligned with the 

new airplanes being certified. These factors include difficulty in issuing new 

regulations, an extremely diverse mix of airplane types and operations, and new 

technology introduction. This study was an opportunity to review all of part 23 against 

the expected future airplane life cycle issues. 

1.3.1 Issuing New Regulations 

The FAA is an executive federal agency; therefore they follow the 

Administrative Procedures Act (APA) when issuing new regulations. APA 

assures agencies keep the public informed of their procedures and rules, to 

provide for public participation in the rulemaking process and to establish 

uniform standards for the conduct of formal rulemaking and adjudication. The 

APA process includes a significant number of procedural hurdles to protect the 

public and assure new regulations are appropriate. The process also adds a 

significant administrative burden, which means only a select few new 

regulations can be implemented each year. Streamlining the rulemaking process 

would be the best solution to assure that part 23 remains current, however, such 

a change is outside of the scope of the recommendations in this report. 

1.3.2 Diverse Mix of Airplanes and Operations 

The diverse range of products and operations within part 23 make it very 

difficult to create regulations that properly address various segments. The scope 

of products within part 23 has grown significantly since the regulations were 

created. In part 23 production today are fixed-wing airplanes from small singleengine pistons to turbine-powered commuter category airplanes that can weigh 

up to 19,000 lbs. 

18 
Because the new airplane designs within part 23 are so diverse the regulations 

have become complex. The regulatory structure of part 23 makes it difficult to 

create regulations to address the projected target. Often these regulations are 

written in a broad manner and they have unintended consequences on products 

of a different size and complexity. While not impossible, certifying a simple, 

two-place airplane is cumbersome and expensive. At the same time, part 23 

doesn’t completely address very complex high-performance turbine products. 

Today, the FAA utilizes special conditions to address the certification 

requirements of complex high-performance turbine airplanes. A wide range of 

products makes it very difficult to target regulations at the correct population of 

airplanes, and product sub-divisions within part 23 would benefit the 

certification process. 

For the aviation industry to continue to thrive in the United States in the safest 

manner possible, it needs to attract new pilots to general aviation. The Light 

Sport Aircraft (LSA) should help attract new pilots, but LSA airplanes do not 

have the utility available in part 23 airplanes. Pilots wanting more utility than 

LSA are still learning to fly in 30-year-old Cessna’s and Pipers. As pilots 

transition from LSA to part 23 airplanes it is advantageous to start new pilots in 

airplanes using the new safety technologies that have become common. Over 

the last decade the number of active private pilots has been declining and the 

number of new pilot starts hasn’t kept pace. Revitalizing the entry-level airplane 

market can have a beneficial effect on attracting new pilots in the safest manner 

possible. 

19 
Historically, division points such as weight and propulsion type have been used 

to differentiate product types however these differentiators are becoming 

increasingly invalid. It can no longer be said that light weight airplanes are all 

simple with low performance because of improvements in systems design and 

the increasing use of integrated electronic systems. Similarly, the near future 

will see single-engine turbofan airplanes with performance comparable to 

traditional piston twin airplanes. The weight and propulsion type assumptions in 

part 23 are valid on about half of today’s new products. In looking forward to 

the next 20 years, the FAA should move away from historical assumptions and 

base requirements on airplane complexity and performance. 

1.3.3 New Technology Introduction 

The number of new technology devices introduced for part 23 airplanes 

increases every year. This has been going on now for more that a decade. The 

introduction of new technologies such as integrated cockpits, moving map 

displays, and Wide Area Augmentation System (WAAS) Global Positioning 

Systems (GPS) have been credited for significant advances in the safety record 

of general aviation airplanes. 

According to Nick Sabatini, Retired Associate FAA Administrator for Safety, 

addressing the record low number of fatal GA accidents (while holding his FAA 

position), “This record is due to a dedicated commitment to safety by everyone 

in general aviation. In particular, manufacturers are providing sophisticated 

technology like GPS and glass cockpits, and the training to go with them, and 

the FAA is vigorously encouraging adoption of these safety enhancements.” 

20 
Furthermore, according to the AOPA’s Air Safety Foundation (ASF) report, 

“Technologically Advanced Aircraft, Safety and Training” from 2007, airplanes 

incorporating this new technology have proportionally fewer accidents when 

compared to the overall GA fleet. While the number of variables associated with 

GA accidents makes the direct correlation between new technology and fewer 

accidents impossible, some level of correlation is likely. Even with all of the 

available new safety technology, pilots are still blamed for fatal accidents. 

Worth noting is that the ASF report points out that “poor judgment will always 

be poor judgment.” 

It is expected that over the next two decades the introduction of new part 23 

technologies, including additional life saving technologies, will continue to 

accelerate. This is good news for GA, but it increases the FAA oversight 

burden. The FAA must develop new regulatory, policy and guidance materials 

to address such technologies. Continuing to address these items on an 

installation-by-installation basis through issue papers and special conditions will 

delay the introduction of safety enhancing technologies. 

1.4 Recommendations to Change the Structure of part 23 

Restructure part 23 to align it with new designs while maintaining the basic 

requirements within the code today. The assumptions of propulsion and weight have 

become outdated; break part 23 into tiers based on performance and complexity. 

Furthermore, it is unlikely that part 23 rulemaking will be able to keep up with new 

technology, so the new structure should be organized in a way that leverages industry 

and government standards. 

The industry and government standard concept envisioned resembles standards 

developed for part 25 systems and avionics. This system addresses the most critical 

systems and gives the FAA final approval authority. Also, they can be quickly 

21 
developed with the assistance of international regulators and industry experts. A tiered 

structure will also support risk-based resource targeting to assure the FAA can spend 

the majority of its safety resources on oversight in areas where risk is higher. 

1.4.1 Tiered Regulatory Structure 

The FAA’s Small Airplane Directorate standards staff has, on numerous 

occasions, explored the possibility of moving from current requirements to 

standards based on performance and complexity. But the effort has been simply 

too large to undertake without a dedicated team and priority. 

To be most effective, product sub-divisions should be based upon the 

characteristics of complexity and performance as these are the items which have 

a direct effect on safety. Part 23 is so broad that it is difficult for the FAA to 

address one area positively without having negative impact in another area. A 

tiered system based on performance and complexity provides the FAA with 

divisions within which the agency can appropriately address the range of 

products. 

 

Conceptually, a three-tiered system will address the scope of products within 

part 23 that exist today and those envisioned in the next 20 years. The team 

recommends that further study go into determining the optimum number of 

tiers. This study proposes the following: 

• Low Complexity, Low Performance 

• Medium Complexity, Medium Performance 

• High Complexity, High Performance 

It is important to have both complexity and performance differentiators as these 

are the physical items which affect safety and drive unique regulatory 

requirements. Increasing systems and systems integration is directly related to 

complexity and the need for more sophisticated safety analysis requirements. 

Similarly higher performance results in more varied operational environments 

and airframe considerations relating directly to certification requirements. 

For many decades regulators around the world have used weight and propulsion 

type assumptions as a measure of complexity and performance but these 

assumptions are based upon designs of the past and they are no longer valid. As 

an example, we are beginning to see more simple airplanes relying on turbine 

engines. It doesn’t make sense to penalize these simple products in the 

certification requirements because they utilize a propulsion type historically 

used on higher performance airplanes. Basing product sub-divisions on 

complexity and performance can provide a more accurate and reliable way to 

address regulatory intent. 

22 
An additional benefit of tiered regulatory requirements is the ability for the 

FAA and manufacturers to quickly assess what new requirements would apply 

to derivative products. Manufacturers commonly grow a product line based 

upon the certification of derivative airplanes. A tiered system supports this 

activity by clearly differentiating additional requirements as complexity or 

performance increase. 

Finally, a tiered system of regulations would assist the FAA in moving towards 

a risk-based approach to safety oversight. Through this system, products with 

higher design risk fall in higher oversight categories aiding the FAA in riskbased oversight. 

The following tier divisions are offered to convey the tier concept. A thorough 

discussion of past, present and future products should be conducted to 

determine the appropriate number of tiers and also those factors which should 

be used as division points for performance and complexity. Another factor that 

should be considered is the number of passengers. Historically, there has been a 

division between 9 or less and 10 or more. 

1.4.1.1 Part 23 Category A – Low complexity, Low performance 

 “Low complexity, low performance” airplanes resemble the basic 

CAR3 airplanes of the 1940’s and 50’s except they are equipped with 

“plug-in” electronic flight instrument systems (EFIS). A direct result 

of the simplicity of the systems and flight envelope of these products 

results in a low risk associated with the design and certification of 

these products. 

As a starting point to illustrate the features most commonly associated 

with complexity and performance the following chart contains a 

conceptual approach to determining the limits of low-complexity and 

low-performance airplanes: 

Complexity Performance 

Unpressurized Maximum operating alt. - 14,000 

ft. 

Conventional Flight Control 

System (Cables, Pushrods, 

etc.) 

Stall Speed – 61 KCAS or Less 

Conventional Construction 

(Fabric, Metal or Composite) 

Conventional Configurations 

(Monoplane, Biplane, Canard, 

etc.) 

Fixed Gear 

23 
By limiting complexity to conventional flight controls, construction, 

configuration and fixed gear, the FAA can easily identify basic safety 

standards for this product type without complicating the certification 

process with regulations intended to address other products. 

Restricting maximum altitude to 14,000 feet is based on oxygen 

requirements 

and will more 

closely align 

these airplanes 

with operating 

regulations. 

Courtesy of Cessna Aircraft 

Unlike Light 

Sport Aircraft 

(LSA) and 

ultralight 

standards, a 

maximum speed isn’t considered. Limiting the stall speed creates a 

reasonable upper speed limit. Stall speed is the one of the most import 

safety limitations for this class of airplane. Unless a manufacturer 

incorporates a very complex flap or other high lift design, most 

fixed-gear airplanes in this class are only capable of about three times 

the stall speed. 

FAA certification standards should serve as the repository for the 

lessons learned and best industry practices for building small airplanes. 

The part 23 design standards should be the basis for any standard, 

accounting for the escalation of requirements and tests. Even 

considering that requirements seldom meet ideal expectations because 

of external factors, the bulk of the pre-1984 part 23 requirements 

contain the combined wisdom of decades of airplane certification and 

would be a good starting point for the first two classes. The 

requirements would need to be thoroughly reviewed and applied as 

appropriate. Furthermore, thought should be given to how this 

approach might simplify issues where airplane parts are manufactured 

outside the continental United States. 

The first category would allow development of a basic set of 

regulations designed to address this type of product without being 

overly burdensome or complicated. For example, the simplicity of this 

class of airplanes would allow for more simple failure analysis as a 

result of the very simple system interactions and basic characteristics 

that these designs contain. Also, develop best industry design practices 

to replace expensive testing for concerns like lightning protection and 

dynamic seat qualification. 

24 
1.4.1.2 Part 23 Category B – Medium Complexity, Medium performance 

 

A medium-complexity, medium-performance airplane might include 

the following characteristics: 

Complexity Performance 

Conventional Flight Control 

System (Cables, Pushrods, etc.) 

Maximum operating altitude - 

25,000 ft. 

Conventional Construction 

(Fabric, Metal or Composite) 

Maximum Speed, MD – 0.6 M 

Conventional Configurations 

(Monoplane, Biplane, Canard, 

etc.) 

The addition of systems such as retractable gear and pressurization 

raises design complexity and the regulations needed to address these 

issues. Conceptually a category B airplane would meet most (or all) of 

the requirements for a category A airplane plus the additional 

requirements of a category B airplane. Higher speeds and altitude 

capability increase the criticality of failures, so category B airplanes 

would have added requirements to address these capabilities. An 

altitude limitation of 25,000 feet provides a good natural break for 

existing structural requirements for pressurized airplanes. 

Courtesy of Wikipedia 

This category also allows 

more reasonable 

standards for the slower, 

single-engine turboprops 

and jets. The team 

envisions this class of jet 

to offer replacement 

utility for existing light 

twins. This class of jet 

should be easier to fly 

when compared to the 

light twins and that feature alone would offer a safety advantage. 

While any proposed standard would provide a higher level of safety 

than that used for the existing fleet of light twins, it would not be so 

high as to discourage the development and production of single-engine 

jets. 

25 
1.4.1.3 Part 23 Category C – High Complexity, High performance 

The final category would address all airplanes which exceeded 

category A and category B criterion: 

Complexity Performance 

Unlimited Unlimited 

This category allows for all airplanes that have performance greater 

than VD of 0.6M, operational capability above 25,000 feet, and any 

complexity above those of category A and B. This may encompass any 

part 23 airplane, from a 2-place trainer up to a 19-seat, 19,000 pound 

aircraft that does not fall into category A or B. This standard is 

proposed to be the most rigorous and would include most or all of the 

requirements of category 

A and B with additional 

FAA regulations specific 

to this class of airplane. 

Development of this 

category should include a 

review of the FAA’s 

cancelled part 24 standard 

for jets up to 50,000 

pounds because many of the ongoing issues are discussed in that 

document. Also, the development of this 

category should include discussions with the 

FAA’s Flight Standards Service so that relevant 

operating requirements are considered. 

Courtesy of Cessna Aircraft 

The European operating rules don’t differentiate 

between private and commercial jets. This means 

that current jet projects have a disconnect 

between operations in the United States and in 

Europe, and manufacturers are having to design 

to two standards. Also, in the current U.S. 

operating rules, all part 121 operations have to use part 25 airplanes. 

The proposed high-performance category should be developed to 

include requirements to will allow airplanes in this category to be 

acceptable for part 121 operations. This should also allow 

harmonization with foreign airworthiness authorities, benefiting 

manufacturers in that they only have to make one airplane. 

26 
1.4.2 Better Utilization of Recognized Industry and Government Standards 

It is unlikely that part 23 will be able to keep up with the rapidly evolving 

technology in the GA market. Industry develops and maintains standards with 

resources from regulators around the world alongside of international industry 

experts. This allows for the rapid development of standardized compliance 

methods for new technologies. The FAA should consider using high-level, 

performance-based regulatory requirements to approve the use of specific 

industry and government standards to address the detailed implementation of 

specific technological solutions. 

Today, the FAA utilizes similar industry standards through policy and guidance 

documents. Many part 25 avionics and systems are approved using industry and 

government standards. Setting high-level requirements that are implemented 

through industry and government standards allows the FAA to have total control 

over design requirements while giving the agency flexibility and quick 

adaptation to address new product developments. Through such an approach, 

the FAA would always maintain control of the approval to use the standards and 

compliance methods. The FAA would also determine if future revisions are 

applicable. Maximizing the use of acceptable industry and government 

documents also keeps in line with pubic law 104-113, which requires 

government agencies to make use of public standards where ever possible.

It’s important to note that the use of industry and government standards is not 

abdication of the regulations by the FAA. The FAA must continue to maintain 

control over part 23. It is not envisioned that manufacturer’s would be allowed 

to self-certify their part 23 airplane. Until the FAA approves the use of the 

industry and government standards, it is simply a documented process which 

has no regulatory credibility. 

The need for individual issue papers and special conditions to address new 

technology will certainly remain; however, the use of industry and government 

standards should reduce the need for repetitive special conditions and issue 

papers. Timely revision of industry and government standards should eliminate 

a significant administrative burden. 

Over the last several decades the use of industry and government standards has 

grown by regulators around the world because they represent a quick way to 

develop safe methods of design compliance for new technologies. The FAA has 

an opportunity to formalize the use of industry and government standards in the 

part 23 regulations thereby increasing the agencies flexibility to adapt the future 

changing environment of part 23. 

27 
1.4.3 Risk Based Oversight 

In addition to setting the design requirements for the certification of new 

airplanes, the FAA also performs oversight of the manufacturers to assure the 

design requirements are being met in a consistent and correct manner. It is the 

goal of the FAA to focus more heavily on areas where compliance is more 

complicated and where it provides the biggest safety benefit. Through the 

development of a tiered set of regulations the FAA would have more flexibility 

determining which products should have higher levels of oversight and which 

should have more basic levels of oversight. 

In the proposed tiered system, the FAA would focus more oversight time and 

effort on the tier with the highest complexity/performance airplanes when all 

other factors were equal. Certainly applicant experience, level of delegation and 

uniqueness of design would play a role in such a determination. 

1.4.4 International Coordination 

Today, aviation products certified and manufactured in the United States are 

nearly always sold internationally, and when this occurs, the designs must be 

certified (or validated) in the country where the design will be sold. Similarly, 

when airplanes made by foreign manufacturers come into the United States, the 

FAA must approve those airplane designs before they can be registered here. As 

a result of this global environment, there is a tremendous benefit in working 

toward regulatory similarity around the world. 

In order for a restructuring of part 23 to be successful, it must involve the 

aviation regulatory agencies from around the world. This will assure the part 23 

changes are readily accepted internationally. Furthermore, such coordination 

assures the FAA can easily review airplanes certified by foreign authorities to 

assure they meet similar safety requirements. 

 

1.5 Conclusion 

In recent decades the part 23 standards have not kept pace with the scope of new 

product designs for a number of basic reasons: 

• The products within part 23 have increased to include the widest variation of 

any other airplane design certification part. 

• Part 23 airplanes are first to see the majority of new technologies being 

introduced into aviation. 

• The FAA is only able to promulgate a small number of new regulations each 

year and rulemaking priority favors large transport airplanes (part 25), making 

part 23 rulemaking difficult. 

28 
In order to align part 23 with the broad spectrum of products it reflects and also to 

assure it can remain current, a strategic change to the structure of part 23 is appropriate. 

Sub-dividing part 23 into tiers based upon complexity and performance allows the FAA 

to issue targeted regulations appropriate for each class of airplane. Such subdivisions 

would also allow the FAA to focus oversight on higher performance and complex 

products. This concept would be aligned with risk based resource targeting. An 

additional benefit of a tiered structure is the ability to leverage the industry and 

government standards approach for simple part 23 airplanes. 

Since so much new technology is introduced in part 23, a structure that leverages 

industry and government standards to address new technologies as they come along 

reduces the need for regulating by special conditions and issue papers. The FAA would 

still have responsibility for regulatory acceptance of industry and government 

standards. The FAA would maintain control of certification requirements while 

leveraging the skill and knowledge of the aviation community to develop new methods 

of compliance. 

This recommendation will potentially have ramifications across multiple regulations 

and disciplines. It will likely affect parts 21, 23, 91, and 135. The FAA, when 

considering the implication of this recommendation, should include all of the 

organizations that could benefit from the part 23 restructuring. 

29 
Courtesy of EAA 

2. Design Certification

Overview 

This section describes the challenges in meeting procedural requirements for the issue of 

type certificates. It also addresses changes to those certificates and changes affecting the 

type design of type-certified products and aviation articles like avionics. 

The bulk of this section and 

the associated 

recommendations address 

the challenges of keeping 

older airplanes operating 

safely. This includes 

upgrading airplanes with 

better systems (e.g., 

alternators), newer avionics 

(e.g., NextGen, navigation, 

information, or 

redundancy), and safety 

gear (e.g., ballistic 

parachutes and inflatable 

restraints). A parallel set of 

recommendations address maintenance of new equipment that the original 

manufacturer never envisioned being installed on their airplane. 

2.1 Finding 2.1 

There are numerous shortcomings in the Approved Model List (AML) Supplemental 

Type Certificate (STC) process that need correcting. 

Issue: The traditional approach to modifying an airplane is to use the STC process. More 

recently the FAA’s Small Airplane Directorate published guidance for modifying large 

numbers of airplanes. That process is called the Approved Model List (AML)-STC. This 

process was not intended to diminish the safety requirement of each modification but to 

capitalize on the commonality of large numbers of part 23 airplanes. The intent of the 

AML was to safely streamline the STC process and speed up installation of new, safety 

enhancing equipment. Unfortunately, there is a lack of understanding by FAA and 

industry concerning the amount of FAA involvement and the requirement for various 

types of AML-STCs. 

 An STC is the FAA’s approval of a major change in the type design of a previously type 

certified product. An STC is classified as either “one-only” or “multiple.” The traditional 

STCs are classified as “one-only” STCs for modification of a specific serial numbered 

aircraft, aircraft engine, or propeller, and “multiple” STCs when the applicant intends to 

modify two or more aircraft, aircraft engines, or propellers. 

30 
 STC approvals using the AML process have the same data requirements as standard STCs 

for a single airplane model. Traditional avionics installations relied on “field approvals” 

using this data from the single STC for multiple approvals where similarity can be clearly 

shown. However, the additional approvals were often carried out with little or no followon ACO involvement, which may only be suitable for simple installations where part 43 

“acceptable data” clearly addresses differences between the existing approval and the 

follow-on installation. 

 

 For more complex avionics installations the AML process requires the applicant to 

address interface considerations to existing equipment upfront for each proposed model. 

This listing of interfaced equipment has typically been contained in the text of the STC. 

This includes items that are recommended, acceptable and prohibited interfaces. 

STCs are issued for a make of airplane; multiple STCs list “applicable models.” The 

AML process takes this concept one step further and lists approved make/model of 

airplane. While the AML process is intended to streamline large STCs, it is not easy to 

make additions of approved/compatible interfaced equipment with previously installed 

avionics components. 

Furthermore, the listing and limitations of equipment interfaces is not always obvious to 

the installer. There are a number of cases where avionics equipment is connected to 

existing equipment by the avionics shop but the STC applicant had not validated the 

equipment combination. These situations resulted in the altered airplane being subjected 

to operating limitations. 

An example of this is where a technician connected a horizontal situation indicator (HSI), 

which was not validated by the STC applicant, with a new GNSS/WAAS receiver. The 

glide slope indicator appeared to work, but did not display proper glide slope trajectory or 

position. The result was a limitation against using the glide slope for GPS until the 

situation was corrected. 

 

2.1.1 Recommendation: 

The FAA needs to amend the AML-STC process to add an Approved Interface 

List separate from the STC but similar to the AML list. The manufacturer will 

develop this list and include any critical system. For example, an audio panel is 

probably not a critical interface, but ADS-B, autopilot, GPS, etc. would probably 

be considered critical depending on the input criteria. For example, generic 

interface criteria for the STC text would address it; for prescriptive product 

interface the approved interface list would address it. 

• The FAA needs to amend the AML-STC process to develop procedures for 

installers and manufacturers to amend equipment to the approved interface 

list. 

31 
• The FAA needs to amend the AML-STC process to develop procedures for 

installers to install equipment not listed in approved interface list. This is to 

address situations where the deviations from the installation are minor. 

2.1.2 Recommendation 

The AML-STC installation manual should list when and where the STC-holder 

expects the installer to augment the STC with acceptable data. For the majority of 

installations addressed by an AML-STC process, an example of acceptable data 

would be AC 43.13. 

Issue: The AML-STC is a hybrid STC unique to equipment in part 23 airplanes. The 

original concept of the AML-STC bridged the gap between the traditional avionics 

installation approach of utilizing an initial OEM generated one and using an STC 

followed by field installations using a follow-on “field approval.” The original follow-on 

installation was approved at the FAA field inspector level using the field approval 

process. This AML-STC process bridged the gap between lack of ACO oversight of 

follow-on installations and the redundant paperwork approval at the Aviation Safety 

Inspector (ASI) level without value added. 

 

When originally envisioned, the AML-STC process was for simple stand alone avionics 

of the late 1990 rather than the fully integrated systems of the early 2000’s. Unlike the 

current multi-model STC which is completely prescriptive, the AML-STC was designed 

to be prescriptive where necessary while being general where flexibility is permitted to 

better serve the diverse GA fleet. The AML process is key to addressing the volume of 

modifications needed to keep the existing fleet of part 23 airplanes operating safely. The 

differences between the traditional STC processes and the flexibility of the AML process 

require a training program developed for FAA and industry to prevent the mistakes of the 

past. 

2.1.3 Recommendation 

Develop and implement ACO, industry, and installer (and any other appropriate 

group) training for the use and issuance of AML STCs. 

• FAA Engineers need to complete an internal training program before 

receiving AML-STC issuance authority similar to Flight Standards required 

training for issuing field approvals. 

• Flight Standards needs to develop training for AML-STC installation 

oversight. 

• FAA should encourage industry to continue public education on AML-STC 

installation and usage. 

• FAA should incorporate training for the use of AML STCs into the FAA 

Safety Team (FAAST) Airworthiness Training agenda and at FAA DER 

seminars 

32 
Issue: Flight Standards policy on field approvals does not address follow-on field 

approvals based on AML-STCs. There are instances where a specific airplane 

might not be listed on the AML. The data may be acceptable and applicable for a 

specific alteration but needs to be approved for a major alteration. The flight 

standards ASI should be able to perform a field approval utilizing data just like 

any other follow-on field approval to an STC. 

2.1.4 Recommendation 

 An AML-STC is still an STC. The small airplane directorate needs to work with 

flight standards to develop policy to address “follow-on” field approvals to 

AML-STCs that can be handled just like would be done for an STC. 

Issue: The AML-STC process (AC 23-22) assumes that the installer will make nonsafety critical amendments to the STC data package utilizing FAA acceptable data. The 

FARs do not support this mixing of data for major alterations. Section 65.95 allows the 

holder of an A & P with an inspection authorization to inspect and approve for return to 

service any airplane after a major repair or major alteration provided the work was done 

in accordance with “approved” technical data. 

 

The AML-STC utilizes “approved” specific data as part of the STC and allows for the 

generic use of “acceptable” data to allow for broader applicability of the AML-STC to 

the variability of general aviation fleet. 

 

The FARs currently do not recognize the use of hybrid (partially approved – partially 

accepted) data. 

2.1.5 Recommendation 

The regulations (either part 43 or part 65/145) need to be amended to allow for the 

use of these hybrid data. 

2.2 Finding 2.2 

Today, replacement equipment is not required by regulation to have a TSO, PMA, or 

FAA approval. For example, an attitude indicator could be replaced by any device that 

resembles the attitude indicator in form, fit, and function but does not meet any design 

standard. This was not the intention of the rules, and required equipment should meet a 

known standard. Replacements for required equipment under part 23 need to be 

“approved” per part 21. 

Issue: “Required equipment” by definition is required for safety. The installer who is 

installing replacement equipment does not have the ability to adequately address 

performance “function” with respect to “non-approved” replacement equipment. This 

recommendation is intended to address equipment as listed in 23.1303, 23.1305, and 

23.1307 and not to impact the mechanic’s ability to make minor repairs. 

33 
2.2.1 Recommendation: 

Replacement equipment for “part 23 required equipment” should be “approved” 

as defined in 21.305.

2.3 Finding 2.3 

The FAA requires ICA’s for original equipment (21.50) and ICA’s for modifications. The 

FAA does not require changes to the original ICA that result from the modifications to 

the original equipment. 

Issue: Issuance of STCs not compatible with the original operations and maintenance of 

the specific airplane being modified. The changes do not adequately 

address the altered airplane or systems ICA. 

For example, the BRS installations in the baggage 

compartment of C-172 that limit the access to the aft 

fuselage/tail section. This affects the inspection of 

avionics, batteries, flight control cables, and corrosion 

control of the aft fuselage section. 

The BRS ICA addresses the continued airworthiness of the BRS system but does not 

address the changes necessary to continue to maintain the altered airplane or systems. 

2.3.1 Recommendation: 

Add the requirement to evaluate the affect of an alteration on the existing 

ICA/maintenance programs as a function of developing amended ICAs. 

2.3.2 Recommendation: 

The FAA should consider a process for developing, managing, and approving a 

supplemental ICA/ICA supplement process similar to what is done today for a 

supplemental AFM/AFM supplement. 

2.4 Finding 2.4 

There are alterations listed in part 43 appendix A that exceed the minimum criteria 

requiring an STC in part 21 section 21.113. 

 

Issue: The definition of Major Change in Type design (21.95) is the same as a Major 

Alteration (part 1) resulting in conflicting application of approval of alterations. The list 

of alterations that are a major alteration (part 43, Appendix A) are in conflict with the 

criteria requiring an STC (21.113). 

In-service airplanes are modified regularly and there’s a history of modifications being 

done under field approvals that should have been done as an STC. These airplanes are 

modified legally under part 43, but these part 43 modifications would have required an 

34 
STC had they been modified against part 21. There are thousands of staff hours spent 

processing field approvals and records of major alterations because the lack of clarity of 

the definition of a minor alteration. 

The criteria for major alterations dates back to the Civil Aeronautics Regulations (CARs) 

with little updating since the early 1950s. A major alteration is a change to the original 

(or properly altered) type design. The Small Airplane Directorate should review and 

manage the items listed in part 43 designating a major alteration. 

FAA Order 8110.46 (Major Alterations, 09/30/2002) defined the criteria of the six 

critical elements of major change to a type design (which corresponds to six criterion of 

major alteration). But the order was rescinded when the FAA issued the field approval 

guidance under Order 8300.10. Order 8300.10 has now been incorporated into the Flight 

Standards Information Management System (FSIMS) (Order 8900.1, effective date 

9/13/2007). The words defining the scope of the six critical criterions only reside in this 

rescinded document. The new order used a matrix based on the intent of the words. The 

old list was more useful in the field and needs to be brought back. 

2.4.1 Recommendation 

The FAA needs to assemble a team to review the conflicts as described in the 

issue. This team needs to review the following: 

• Certification standards and validation of conformity rests with 

certification. But Flight Standards is responsible for part 43 which is the 

primary guidance for modifications to an airplane. Certification should be 

providing the information for what is considered major in part 43. 

• Develop a regulatory approach to evaluating changes to the type design 

that is consistent from part 21 though part 43. This allows for an 

evaluation for a change (alteration) from the highest level of certitude 

(STC) to the lowest level (minor alteration). 

• Amend part 43, Appendix A, to eliminate conflict with part 21.93. 

2.4.2 Recommendation 

The FAA should re-assign oversight responsibility for alteration regulatory 

criteria (part 43, Appendix A) to the certifying directorate. 

2.4.3 Recommendation 

Use the definitions from Order 8110.46 in a new document or reissue the 

applicable portion of the order in a document like Order 8300.10 (NOTE - Order 

8300.10 has now been incorporated into the FSIMS (Order 8900.1, effective date 

9/13/2007). 

35 
2.5 Finding 2.5 

There is no procedure for removing a flight manual supplement after equipment has been 

removed. Once that supplement has been approved as part of the AFM, the document can 

not be legally changed, i.e. the supplemental can not be removed without subsequent 

approval. 

Issue: Current policy adequately addresses the requirement to “add” data to the flight 

manual. There is no guidance on amendments to the flight manual when a component is 

removed, (i.e. avionics). 

2.5.1 Recommendation 

Need a working group to develop policy procedures to address the 

revision/removal of AFM supplemental material and to define alterations that 

would require supplements. (ref. FAR 23.1581) 

2.6 Finding 2.6 

In-service installers are being held to a higher standard of Airplane Flight Manual 

Supplement (AFMS) approval than the original aircraft manufacturer. 

Issue: Section 23.1581 allows for “acceptability” of non-limitation sections of a flight 

manual; however, field level AFMS are treated to the same level of review and approval. 

AC 23-8 describes the process for submission, review and acceptance of flight manual 

supplements. These procedures require explicit review and acceptance – i.e. approval. 

2.6.1 Recommendation 

AC 23-8 should be revised for flight manual supplements for equipment 

(23.1585) to allow for the “acceptability” as allowed for in 23.1581 (b). 

2.7 Finding 2.7 

Airplane Flight Manual Supplement (AFMS) are being added for non-essential 

equipment. 

Issue: AFMS are being approved by FAA Flight standards for simple devices like a tach, 

ELT, or new fuel pump. This particular issue ends up taking more time and resources, 

both FAA and installer, than all the other recommendations in this section. This problem 

may have started with GPS installations because they didn’t include many of the basic 

limitations that the Airman’s Information Manual (AIM) originally had for traditional 

avionics. This particular problem creates no-value-added paperwork and workload for 

FAA and industry. 

36 
2.7.1 Recommendation 

AFMS should only be required for “essential equipment” and should not be 

required for information already contained in the AIM. 

37 
Courtesy of AEA 

3. Continued Airworthiness

Overview 

Aircraft certification standards create a set of parameters within which an airplane will 

have predictable flight 

and structures 

performance. These 

standards are created 

using technical data 

obtained through 

research, including 

measurable lessons 

learned from the 

previous design and 

operational history of 

airplanes. 

Certification 

standards create a 

level of design safety 

acceptable to the operator, maintainer, and public safety. 

The first priority and most important function of any safety management system is to 

prevent accidents. Continued airworthiness is a principal component of safety 

management. By periodic inspections and regular and preventive maintenance and, the 

airplane is judged to meet its type design and remains in a safe condition for flight, thus it 

is considered airworthy. 

Overseeing the continued airworthiness of the existing fleet of airplanes serves key 

concerns. These include identifying, analyzing, and providing mitigation for specific 

safety issues. The continued airworthiness process is also important for validating the 

certification requirements themselves. Lessons learned in conducting the responsibilities 

of continued airworthiness improve regulations and standards for type certification. 

Improving the continued airworthiness process is critical to improving safety in the short 

term. It is also important for long-term improvements to the certification requirements 

benefiting future designs. 

It is important to note that often the work of certification has more resources than 

continued airworthiness. A better balance is needed to guarantee the continued 

improvement of the safety record of the GA fleet. FAA Aviation Safety Engineers 

typically are assigned both certification and continued airworthiness responsibilities. 

These responsibilities should be assigned to engineers with appropriate background, 

experience, and training in either certification or continued airworthiness. 

Many of the findings related to continued airworthiness apply to other areas defined by 

this Process Review. In reviewing the findings included in this section, it was felt that 

38 
their impact related to Continued Airworthiness was their primary reason for being 

included, thus they were placed in this section. All of the findings in this section can be 

linked to airworthiness standards and operating standards and should be reviewed for 

impact when the final part 23 certification rule is revised/created. 

3.1 Finding 3.1 

Existing rules and guidance for the maintenance of part 23 airplanes do not account 

for the actual age of the airplane and how its maintenance requirements change as 

the airplane ages (both calendar age and cycles, as well as the type of operational 

use). Current Instructions for Continued Airworthiness (ICAs) assume the 

airplane’s condition is static (factory new). While a condition close to that initial 

condition is optimal, ICAs need to take into account airframe and systems 

degradation associated with aging. ICAs should also explain probable degradation 

areas to the maintenance professional and owner/operator. 

Issue: Current CFR part 23 requirements only address new products, and are not 

required to take into account long-term maintenance and inspection requirements. 

3.1.1 Recommendation 

Revise CFR part 23 to include requirements that consider degradation of 

aircraft, aircraft parts, and aircraft systems in the ICA. A team of subject 

matter expert should review this recommendation. 

Issue: Historically, ICA & Maintenance manuals are based on engineering 

assumptions of operational longevity. Industry and the FAA are concerned about 

aging airplane issues because airplanes are in service for longer than originally 

expected. Going forward there is an opportunity to assure that new products do not 

have the same issue. Inspections are currently based on a flat line (no accounting for 

airframe hours) approach to continued airworthiness to address the extended life of 

modern airplanes. 

A new approach to ICA is necessary. Type clubs are an invaluable resource in 

understanding the maintenance evolution of an airframe. Also, enhancing the 

process for mechanic’s reporting of airframe and engine issues will add to the data 

needed to create accurate maintenance instructions.

3.1.2 Recommendation 

Form a working group to develop an advisory circular that will address 

aging airplane inspection criteria. The FAA/industry booklet “Best Practices 

Guide” for additional areas to inspect as airplanes get older is a good start 

for this issue. 

39 
3.1.3 Recommendation 

The working group should also consider if implementing a Limit of 

Validity is appropriate in ICAs developed for new products. A Limit of 

Validity is when an ICA covers the continued airworthiness up to a time 

limit or service limit. (This is not the same thing as a life limit.) This is 

intended to drive design requirements that will allow for this type of 

significant inspection, without inducing maintenance or inspection related 

damage. 

Issue: The current 43.15 (c), Annual and 100 hour inspections currently reads as 

follows: 

(1) Each person performing an annual or 100 hour inspection shall use a checklist 

while performing the inspection. The checklist may be of the person's own design, 

one provided by the manufacturer of the equipment being inspected, or one 

obtained from another source. This checklist must include the scope and detail of 

the items contained in Appendix D to this part and paragraph (b) of this section. 

 

As currently written, 43.15 encourages a culture which allows the maintainer to 

ignore the recommendations of the manufacturer for doing basic maintenance. 

3.1.4 Recommendation 

Amend 43.15 to create a hierarchy for the maintenance data being used to 

maintain part 23 airplanes. The team recommends the following revision 

to 43.15 (c) Annual and 100 hour inspections: 

 (1) Each person performing an annual or 100 hour inspection shall use a 

checklist while performing the inspection. The annual or 100 hour 

checklist shall be the checklist incorporated in the Instructions for 

Continued Airworthiness (ICA) of the equipment being inspected. For 

airplanes manufactured prior to 1981 if the manufacturer of the 

equipment being inspected has not provided a checklist, the checklist may 

be of the person's own design, or one obtained from another source. This 

checklist must include the scope and detail of the items contained in 

Appendix D to this part and paragraph (b) of this section. 

(a) The annual or 100 hour inspection shall also include any inspection 

item included in an Instruction for Continued Airworthiness required for 

the continued airworthiness of an alteration. 

 Issue: A mechanic's task training as required by 65.81 is not currently 

documented. As airplanes become more complicated and systems become more 

integrated there is increased need for enhanced mechanic training documentation. 

 

40 
3.1.5 Recommendation 

§ 65.81 General privileges and limitations should be reorganized to read as 

follows to better capture the type of activities performed by mechanics. In 

addition, the new (a)(4) adds a record keeping requirement to verify 

compliance with (a)(1) thru (a)(3). 

(a)(1) A certificated mechanic may perform the maintenance, preventive 

maintenance or alteration of an aircraft or appliance, or a part thereof, 

for which he is rated (but excluding major repairs to, and major 

alterations of, propellers, and any repair to, or alteration of, instruments), 

and may perform additional duties in accordance with §§ 65.85, 65.87, 

and 65.95. 

(a)(2) A certificated mechanic may supervise the maintenance, preventive 

maintenance, or alteration of, any aircraft or appliance, or part thereof, 

for which he is rated after he has satisfactorily performed the work under 

the supervision of a qualified licensed mechanic at an earlier date. If he 

has not so performed that work at an earlier date, he may show his ability 

to do it by performing it to the satisfaction of the Administrator or under 

the direct supervision of a certificated and appropriately rated mechanic, 

or a certificated repairman, who has had previous experience in the 

specific operation concerned. 

(a)(3) A certificated mechanic may approve and return to service any 

aircraft or appliance, or part thereof, following maintenance, preventive 

maintenance, or alteration of, for which he is rated after he has 

satisfactorily performed the work under the supervision of a qualified 

licensed mechanic at an earlier date. If he has not so performed that work 

at an earlier date, he may show his ability to do it by performing it to the 

satisfaction of the Administrator or under the direct supervision of a 

certificated and appropriately rated mechanic, or a certificated 

repairman, who has had previous experience in the specific operation 

concerned. 

 (a)(4) A certificated mechanic must maintain a record of individual task 

training and qualifications. 

(b) A certificated mechanic may not exercise the privileges of his 

certificate and rating unless he understands the current instructions of the 

manufacturer, and the maintenance manuals, for the specific operation 

concerned. 

41 
3.2 Finding 3.2 

The FAA needs to develop a process to capture operational utilization data for high 

airframe stress operations like pipeline patrol and flight training. 

 Issue: The operational regulations address commercial service of the aircraft in 

Subchapter G including recordkeeping requirements. However, many of the high 

stress flight operations are not regulated by Subchapter G and therefore fall under 

the general operating rules of part 91. As a result, the operational data for high 

stress flight operations is grouped together with recreational and business flight 

operations masking the data. 

3.2.1 Recommendation 

 

A team should review this issue in more detail to develop metrics 

to account for high stress flight operations, in particular on older 

airframes. Included in this consideration is the adoption of a 

definition of aerial work. 

3.3 Finding 3.3 

The FAA needs a means to make addressing the thousands of modifications necessary to 

the aging fleet of 200,000 GA airplanes easier. This is not only to make safety related 

modifications more affordable and feasible, but also to remove the many delays 

associated with certified airplanes. 

Issue: An example of this finding is seat fabric in today’s automobiles meet a 

standard that exceeds the flame retardant capability of early CAR 3 

airplanes. The auto standard should be an acceptable replacement standard. 

Proposed AC 23-27 discusses this issue. 

42 
3.3.1 Recommendation 

The Small Airplane Directorate should issue a policy that would allow the 

use of accepted industry or government standards (ASTM, DOT, etc.) in 

the alternation or modification of a product if that standard exceeds the 

original standard created under CAR 3. This policy should also accept the 

declaration by the material manufacturer that this product meets the 

accepted standard. 

Issue: We don’t need to make manufacturer’s meet HIRF and Lightning 

protection for equipment whose failure does not have a safety impact. 

3.3.2 Recommendation 

Develop a list of equipment that actually needs HIRF and Lighting protection 

based on the failure mode or criticality. 

3.4 Finding 3.4 

Airplanes are being repaired by replacing major airframe components with salvage parts. 

These parts rarely have associated hour/operation history. 

Issue: The parts, with an unknown hour/operation history, adopt the hours of the 

products that they are installed on. We need to ensure that those components at the end of 

their life, salvage parts for example, do not get transferred to other “in-service” airplanes 

without regard to the part’s operational history. 

3.4.1 Recommendation 

A working group needs to look at possible ways to track airframe hours as 

airframe components progress through a disassembly, salvage, reassembly 

cycle. 

3.5 Finding 3.5 

Replacement and repair part acceptability for installation on type certified airplanes 

seems to be a confusing area for maintenance personnel. This is especially true for legacy 

airplanes when the OEM is no longer in business or no longer supporting certain models 

and part and material availability is limited. 

Issue: FAA and maintenance personnel should be instructed in the proper procedures to 

determine the acceptability of any part (including documentation) that is used to maintain 

a type certified product. This should include acceptable parts, approved parts, ownerproduced parts, standard parts, parts fabricated by maintenance personnel, and validation 

of commercial off-the-shelf products. 

43 
3.5.1 Recommendation

Develop and implement ACO, Flight Standards, industry, and installer 

(and any other appropriate group) instructions in the proper procedures 

to determine the acceptability of any part that is used to maintain a type 

certified product. 

• Flight Standards/Small Airplane Directorate needs to develop 

training for oversight for the acceptability of parts installations. 

• FAA should encourage industry to continue public education 

on the acceptability of parts installation and usage. 

• FAA should incorporate training for the acceptability of parts 

installation into the FAA Safety Team (FAAST) Airworthiness 

Training agenda and at FAA DER seminars 

• Part 147 maintenance schools should add a section on 

instructing maintenance personnel on the important 

responsibility of using ”acceptable for installation” parts to 

maintain certified products. Basis of training should include as 

a minimum the following: 

o Advisory Circular 21-29C 

o Advisory Circular 43-18 

o Advisory Circular 20-62D 

3.5.2 Recommendation 

Develop and implement instructions for the documentation and 

recordkeeping of any acceptable part used to maintain a type certified 

product. 

3.6 Finding 3.6 

Human Performance is a dominant factor in GA accidents. One important aspect of the 

human performance issue is airplane maintainability. 

Issue: Design techniques, safety assessments, and regulations do not adequately address 

the subject of human error in design and maintenance. Better human based designs in 

new airplanes have the potential to make the maintenance aspects of airplane repair more 

people friendly. Attention to human factors issues should be scaled to the performance 

and complexity of the airplane. That said, don’t overlook simple designs. “Simple” 

airplanes also contribute to the GA accident numbers and good design may help reduce 

the accidents. 

44 
3.6.1 Recommendation 

The FAA should consider maintenance human factors (e.g., design for 

maintainability and usability of technical documentation) in aircraft 

certification processes. This requires an increased level of attention to 

the significance of maintenance processes in terms of the life cycle of 

airplanes. 

45 
4. Data Management 

Overview 

Courtesy of AEA 

Data management is defined to 

include the collection, 

organization, and analysis of 

safety data, including the 

implementation of appropriate 

corrective action(s) to mitigate 

the safety risk. Feedback is used 

to ensure that actions taken 

mitigated the risks effectively. 

The Data Management working 

group built on several existing 

data efforts. A major safety 

concern is that the average fleet 

age for part 23 airplanes is already over 40 years old. Furthermore, as newer airplanes 

age, they will include technologies that industry has no long term experience maintaining. 

These technologies include composite airframes and integrated avionics and engine 

controls that use large numbers of microprocessors. One program that the team felt was 

very important to improve is Service Difficulty Reporting (SDR). There is limited 

success with this program today. Unfortunately, it was built when technology in aviation 

was limited. So today, many new critical areas need to be added where problems should 

be reported. 

There are currently numerous data management systems used by both the FAA and 

industry for collecting, organizing, and storing data. Many, if not most of these systems, 

are not coordinated or compatible with other systems. This makes these systems much 

less effective, some to the point of their having little value when targeting continued 

airworthiness. Poor data quality and difficulties in data interpretation caused even more 

systems to be ineffective in their usefulness. 

Many of these systems are not capable of identifying hazards associated with the data nor 

do they offer any acceptable type of risk analysis capabilities or methodology. In order 

for a system to proactively manage system safety, it must focus on identifying precursor 

criteria from the incident data it collects. 

The FAA supports the International Civil Aviation Organization (ICAO) harmonization 

efforts to develop SMS world-wide dictates improving aviation safety data management. 

Another part of this effort is to develop more quantitative risk analysis methodologies. 

Improving risk analysis is directly associated with improving aviation safety. To meet the 

demand of quantitative risk analysis, adequate useable data are required. 

46 
One of the important elements of the FAA SMS effort is developing better tools to 

conduct Continued Operational Safety (COS) tasks. The Monitor Safety Analyze Data 

(MSAD) team is designing an application to address this need. The MSAD tool relies 

upon various databases such as the SDR database for both maintenance and operational 

in-service data to perform quantitative based analysis to determine the level of risk and 

appropriate mitigation actions. This requires a more progressive approach to data 

collection and management. The MSAD program is well underway and it offers a more 

quantifiable approach to Continued Operational Safety 

4.1 Finding 4.1 

General aviation in-service data records only a small fraction of the actual inservice (operational and maintenance) events occurring. 

Issue: As the FAA continues to evolve to more quantitative analysis methods to 

support risk assessment of in-service issues, more detailed data sources will 

improve the risk assessment of general aviation. Estimates by AFS-620 indicate that 

possibly less than 10 percent of in-service issues are reported by maintenance 

providers. 

4.1.1 Recommendation 

Revise 14 CFR 21.3 to include a much broader list of detail failure 

modes for system, structures, and flight handling characteristics. 14 CFR 

21.3 lacks many of the new technology-based system issues that may 

have a critical effect on safety. Appendix C contains suggested 

expansion subjects for 14 CFR 21.3 requirements. 

4.1.2 Recommendation 

Revise 14 CFR 91 to mandate that general aviation maintenance 

providers submit service difficulties as required by 14 CFR 21.3 and 14 

CFR 135.415 reporting requirements to the FAA’s Service Difficulty 

Reporting (SDR) system. This recommendation would dramatically 

improve the availability of pertinent safety related data that will improve 

the quantitative risk analysis process required by MSAD. 

47 
4.1.3 Recommendation 

FAA should educate the maintenance community through outreach such 

as presentations at inspection authorization seminars, newsletters, and 

other industry related outlets on the importance of the content of SDR 

submissions. This will not only encourage more participation but will 

also validate the importance of the reporting of in-service issues. 

4.2 Finding 4.2 

There is a lack of accurate information regarding the fleet times of general aviation 

aircraft. 

Issue: The lack of accurate service times for the general aviation fleet makes it 

difficult to determine total fleet times when considering corrective action such as 

airworthiness directives, special airworthiness information bulletins, etc. Accurate 

service times are also important when calculating the risk of any given safety issue 

as it is a key component in determining probability component of the risk that 

exists. 

4.2.1 Recommendation 

FAA should mandate requirements for reporting of GA product times in 

service on an annual basis. This requirement should be relative easy to 

perform by the maintenance provider as part of the normal paperwork 

associated with required periodic inspections. 

4.3 Finding 4.3 

The review and analysis of GA data can be improved to derive more detailed 

information to direct mitigation actions to reduce unacceptable risk with specific 

make/model aircraft. 

Issue: The GA in-service data collected are often not evaluated or analyzed to 

determine if safety issues exist that may be above acceptable risk levels. To meet 

the current Safety Management System philosophies dictated by AIR-1, better data 

evaluation will be mandated through the MSAD process. This process will also rely 

upon quality in-service data requirements. 

4.3.1 Recommendation 

Develop viable tools that allow improved filtering, searching, and trending 

of the aviation data bases. 

48 
4.3.2 Recommendation 

The FAA should develop and train data management specialist assigned to 

analyzing and sorting GA data to better assess safety issues. Specialist 

would also work with industry data sources to augment FAA collected 

data. 

4.3.3 Recommendation 

AIR COS personnel should meet with their appropriate counterparts within 

AFS on a periodic basis with the purpose of improving the collection and 

analysis of aviation safety data and their sources. 

4.4 Finding 4.4 

The SDR system is underutilized by GA maintenance personnel as a source for inservice safety issues specific to make/model aircraft. 

Issue: The FAA SDR database collects in-service data to allow maintenance 

personnel, owner/operators, and the FAA to view and analyze safety data for GA 

products. The data can be used to identify specific areas of concern that 

maintenance personnel should be aware of when maintaining and inspecting 

specific make/model aircraft. Also, some data submissions are of low value due to 

the fact that the concern is not safety related or not properly communicated. 

4.4.1 Recommendation 

Revise 14 CFR 145 to include SDR training requirements and how SDR 

type data are used to improve safety in FAA approved maintenance 

school syllabuses. 

4.4.2 Recommendation 

Improve search and sort functions of the SDR database to better facilitate 

maintenance personnel using the SDR database to locate specific 

make/model in-service issues. 

4.4.3 Recommendation 

FAA should improve communications with the maintenance community 

on COS and to educate them on the types of issues that should be 

reported through the SDR system. The FAA needs to show the 

maintenance community that their SDR submissions are valuable. 

49 
4.4.4 Recommendation 

Wider distribution of FAA Advisory Circular 43.16A, Aviation 

Maintenance Alerts, and information on the same level of the previously 

named information. This should include encouraging aircraft type clubs 

to include appropriate AC 43.16A information in their publications to 

their members. 

4.4.5 Recommendation 

Modify the SDR database to accept digital attachments to SDR and 

Malfunction & Defect report submissions. 

4.5 Finding 4.5 

Submission of 14 CFR 21.3 mandatory reporting is done through various forms and 

methods including written reports and telephone conversations. The use of these 

valuable data by data management tools is reduced by the lack of a consistency and 

database usable method. 

Issue: Valuable 21.3 safety data are often submitted in forms not compatible with 

electronic database management systems. The data are then often not included in 

electronic database functions such as search and trending. By standardizing the 

reporting and requiring electronic submission, the safety data could then be better 

utilized in making better continued airworthiness decisions. 

4.5.1 Recommendation 

Update 14 CFR part 21.3 requirements to include a standardized data form 

or template that is electronically submitted to the FAA and is compatible 

with other databases. 

4.5.2 Recommendation 

Invoke industry standard taxonomy, such as Commercial Aviation Safety 

Team/International Civil Aviation Organization Common Taxonomy Team, 

to standardize the text of SDR submissions to provide improved search 

capability of the system. 

50 
4.6 Finding 4.6 

General aviation does not access valuable data that manufacturers and/or type 

design holders may have that would improve continued airworthiness efforts. 

Issue: Manufacturers and/or type design holders hold valuable data that could be 

important information to continued airworthiness decision making. The data should 

be collected by the FAA and protected to gather real-world information regarding 

how type designs are meeting in-service expectations. 

4.6.1 Recommendation 

Develop a program for the FAA to collect certain types of in-service data 

from each manufacturer/model on an annual basis. Examples of data would 

include: 

• Top ten repair parts being used (does not include consumables) 

• Percentage of back orders vs. in stock parts (are repair parts 

available) 

• Service centers participating in training 

• Holdup of type designs in different types of operational 

environments (training, air charter, cargo, etc.) 

• Types of operational issues (design vs. operations) 

• What types of recurring in-service issues are experienced by a type 

design 

• Is adequate tooling/test equipment available 

• Quality of service related data 

51 
5. Pilot Interface

Overview 

The Pilot Interface 

Working Group 

was composed of 

representatives 

from the flight 

test, flight 

operations, and 

flight training 

segments of the 

industry and FAA. The working group shared information during discussions from both 

the aircraft certification discipline and the training and operations disciplines. The 

approach to operating an airplane differs between the two disciplines but not as much as 

the working group members were initially concerned they would. 

The findings show the flight test methods used to determine speeds, procedures, and 

aircraft performance sometimes differ from actual operational practices. The methods 

used in flight test have been developed over decades, and, while they may not reflect 

normal operations, they allow for consistency and standardization across manufacturers. 

In some cases, the method used in flight test should relate to the pilot community so they 

can adequately understand why there are performance and airplane limitations or how to 

interpret and apply performance data. 

Historical data from the National Transportation Safety Board (NTSB) Aviation Accident 

database and also from the AOPA Air Safety Foundation accident database is included in 

this section (found in Appendix D) to support the recommendations. The ten years 

between 1998 and 2007 were selected for the source of the data except where noted. Part 

25 accident data was used where the airplanes and part 91 operations were very similar to 

part 23 jets and their associated operations. 

 

5.1 Finding 5.1 

A number of disconnects exist between the FAA and aircraft operators due to an 

inadequate level of information sharing between the FAA Aircraft Certification 

Service (AIR) and the FAA Flight Standards Service (AFS). Improved 

communication between AIR and AFS could help eliminate these disconnects.

Issue: Air transport pilot (ATP) and type rating stall training. AFS stall related 

practical test standards (PTS) for ATP and type rating certification for pilots only 

require demonstration of recovery from an impending stall with no requirement for 

the demonstration of recovery from an aerodynamic stall or stick-pusher activation. 

On the approach to a stall, the PTS requires the pilot to maintain altitude until stall 

warning activates, and, on the recovery, the pilot must demonstrate a minimum 

52 
altitude loss that is frequently interpreted by examiners to an altitude loss of 100 

feet or less. The current ATP and type rating recovery standards from stall warning 

essentially require adding power and maintaining or increasing pitch attitude by 

pulling back on the elevator control in an effort to minimize altitude loss. Fatal 

accidents may have occurred in the last few years where pilots have applied these 

same techniques in attempting to recover from an unexpected full aerodynamic stall 

or a low-speed, stick-pusher activation condition. The technique of attempting to 

recover from a stall using the minimum altitude loss recovery technique required in 

ATP and type rating training from stall warning (not actual stall) are inappropriate 

for recovery from an actual aerodynamic stall and from stall warning in many 

situations. 

The AIR type certification process for stall recovery is inconsistent with the AFS 

training and pilot ATP and type rating certification requirements in that no part 23 

requirement exists to define a maximum altitude loss during stall recoveries from 

stall warning activation or from aerodynamic stall or pusher activation. The amount 

of altitude loss will vary depending on airplane configuration and airplane altitude. 

At low altitudes, rapidly adding power and pulling back on the elevator control in 

attempting to hold altitude can cause extreme pitch attitudes in some airplanes and 

aggravate the stall conditions. At high altitudes, this technique will not even work 

for stall recoveries from stall warning; where the pilot will have to lower the nose 

and pick up speed. 

5.1.1 Recommendation 

Re-emphasize the difference between stall warning and aerodynamic stall. 

Pilots may fly an airplane for years and never stall the airplane or 

experience stick-pusher activation. Most small airplanes, including small 

jets, can not recover from an aerodynamic stall or stick-pusher activation 

without pushing the nose down and flying out. Even in high-performance 

jets, there are parts of the envelope where the airplane will not recover 

from the stall or at stall warning with power only. 

The FAA should eventually require aerodynamic and/or stick-pusher (if 

applicable) stall recovery training on all ATP checks and on type rating 

training and certification. This could be accomplished in a simulator or in 

an actual airplane. It is anticipated that the majority of this training will be 

in simulators, which are currently not properly programmed to reflect 

airplane flight characteristics below stall warning. 

Until training simulators are programmed to more closely reflect the actual 

stall/pusher characteristics of the individual airplane: 

• Stall recovery techniques for ATP and type rating training and 

certification should be confined to recovery from stall warning. 

53 
• A stall recovery technique that requires lowering the nose of the 

airplane (reducing the angle of attack) should be utilized at stall 

warning (stick shaker) activation (or other impending stall cues) 

with application of power sufficient enough to maintain/reestablish airspeed and control of the airplane. 

• The altitude loss during stall recovery from stall warning should 

not be bounded by an arbitrary and possibly unachievable number 

of feet but should be based on the characteristics of the individual 

airplane involved (based on data obtained during the airplane type 

certification program). 

Issue: There is some confusion in the field on how to use the climb gradient and 

distant obstacle clearance data published in the performance section of the airplane 

flight manual (AFM) for commuter category airplanes and for jets over 6,000 

pounds. This climb data provides airplane performance information for the oneengine-inoperative (OEI) situation. Part 23 jets and commuter category airplanes 

are weight/altitude/temperature (WAT) limited airplanes. This means their weight 

limits are based on their climb performance OEI meeting a minimum climb 

gradient. This minimum climb gradient may be different from operationally 

required climb gradients and distant obstacle climb requirements. 

Continuing the OEI performance information, the FAA “Pilots Handbook of 

Aeronautical Knowledge” (FAA-H-8083-25A) pages 9-35 states that the first 

segment climb starts when aircraft becomes airborne. This interpretation is 

consistent with part 23.67(c) (1), which states that the first segment climb gradient 

requirement is measured at the takeoff surface. Second segment climb follows first 

segment in that the airplane is in the same configuration as the first segment 

(takeoff thrust and takeoff flaps) except that the landing gear is up. The second 

segment gradient is measured at the end of the segment, 400 feet above ground 

level (AGL). Second segment climb is followed by the enroute climb gradient 

measured at 1,500 feet AGL, again at the end of the climb segment. The second 

segment OEI gross climb gradient generally determines the maximum takeoff 

weight allowed in this category of airplane. 

The minimum required OEI climb gradient is a different performance measure from 

the development of takeoff flight path performance development. Even though the 

two performance issues differ, there is confusion about how to address each 

operationally. Advisory Circular "FLIGHT TEST GUIDE FOR CERTIFICATION 

OF PART 23 AIRPLANES" (AC 23-8B) page 41 states that "The takeoff flight 

path begins 35 feet above the takeoff surface at the end of the takeoff distance 

determined in accordance with § 23.59." The published takeoff flight path data are 

generally those that create confusion in actual operations. Pilots understand how to 

use the OEI climb data. The AFM chart or table clearly shows if the airplane can 

meet the minimum climb gradient for the current weight and temperature. But 

relating the AFM data to the flight path is not as clearly understood. 

54 
5.1.2 Recommendation

FAA Aircraft Certification Service (AIR) and Flight Standards Service 

(AFS) should work jointly to clarify the understanding of climb 

performance development and how it is conveyed during training in 

weight/altitude/temperature (WAT) limited airplanes. 

It is recommended that the 

FAA address the following 

questions concerning climb 

performance and disseminate 

the information to the 

appropriate pilot community. 

The questions most 

frequently asked by pilots 

regarding climb gradients 

are: 

Courtesy of Cessna Aircraft 

• How should the AFM takeoff flight path and associated net climb 

gradient data actually be used in service? 

• How are the data used in part 91 operations versus part 135 

operations relative to distant obstacle clearance and minimum 

climb requirements expressed in feet per nautical mile? 

• How are the data used in IFR operations versus VFR operations? 

• How do the requirements apply to all engines versus engine out 

situations?

Issue: There is confusion within the pilot community on what maneuvering speed 

(VA) actually means in terms of protection from airframe failure. Maneuvering 

speed is defined in the FAA Airplane Fling Handbook (FAA-H-8083-3A) as "The 

maximum speed where full, abrupt control movement can be used without 

overstressing the airframe." The text provides a better explanation and states that 

the aircraft will stall first before the airframe structure is damaged. The same 

definition is found in FAA-H-8083-25A. 

These are the "official" FAA definitions and the way pilots are taught. While the 

"official" definition implies that you can deflect any of the flight controls, it is only 

in pitch (up) that the "full, abrupt" deflection of the controls can occur without 

structural failure. The FAA introduced the speed term VO intending to correct this 

issue. VO is supposed to be the speed that protects the whole structure and not just 

the wings. Unfortunately, VO has become more confusing than VA. Applicants are 

also confused and making VO equal to VA based on the structural definition, 

defeating the whole purpose of VO. A recent example of what can happen with full 

deflection control inputs above VA is the November 12, 2001, Airbus Industries 

55 
A300-605R crash in Belle Harbor, NY resulting in the separation of the airplane's 

vertical stabilizer and rudder in flight. The FAA Air Transportation Division (AFS 

200) issued guidance via a Safety Alert for Operators (SAFO) 05002 (10/25/05) on 

the subject of multiple full deflection, alternating flight control inputs. 

5.1.3 Recommendation 

FAA flight standards, AIR flight test, and AIR structures need to agree on 

explanatory language for pilots to understand VA and what protection is 

actually available to the pilot when complying with these airspeeds. VA, 

maneuvering speed, is considered the speed where it is safe for the pilot to 

input full control deflections without damaging the airplane. Beyond VA, 

full control deflections can result in structural failures as related in the 

accidents listed under this section in Appendix D. Further, it is 

recommended that the FAA delete the requirements for VO and increase the 

structural design criteria for VA to a more robust state. 

Issue: Similar to the general understanding of VA is the pilot’s understanding of 

limit loads i.e., the maximum G-loading accounted for in the airplane’s structural 

design criteria. An airplane designed to pull 3.8, 4.4, or 6 “gs” is only expected to 

be exposed to those structural load levels periodically throughout the airplane’s life. 

It is not intended that the airplane can be repeatedly flown to limit load. Repetitive 

excursions to load limits will shorten the airplane’s structural fatigue life. 

5.1.4 Recommendation 

It is recommended that FAA Flight Standards include clear and direct 

information about load limits to pilots and aircraft operators via training 

materials, the AIM and AFM. The information should identify that 

repetitively operating aircraft to load limits will deteriorate the airplane’s 

structural fatigue life. 

Issue: Approach Speeds (VREF) greater than the AFM published speed can result in 

runway overruns on minimum length fields. We understand that training 

organizations may teach pilots to fly VREF+5 because some FAA examiners will fail 

pilots for going slower than VREF. This approach, if taught, leads to speeds that are 

too high to match the AFM landing distance. Furthermore, it assures runway 

overruns at airports with minimum length runways. Pilots should be informed or 

understand that AFM landing distance data are the best or shortest distance that a 

pilot could expect using the most aggressive technique that is safe while 

approaching the runway at VREF. Current part 23 standards assure adequate airplane 

controllability at all speeds down to VREF -5. Therefore, flying at VREF, or slightly 

under VREF, is not unsafe. For reference, Air Transport Pilot (ATP) standards are 

VREF +5 / -5. 

56 
5.1.5 Recommendation 

The FAA should reconsider establishing VREF training and operational 

check ride margins to encourage pilots to fly at VREF or slightly slower 

instead of the current VREF -5/+5 especially when operating on minimum 

length fields. Training to VREF+5 for operations on minimum length fields 

should stop. VREF is the pilot’s target speed and allowable drift should be 

controlled to speeds slightly below VREF i.e., VREF -5. 

Supporting historical data: 

Of the 50 runway overruns contained in accident data, during the ten years 

between 1998 and 2007, thirteen involved relatively small jets and were 

attributed, in whole or in part, to excessive airspeed on final. The data 

includes single events involving a Cessna Citation 525A and the Hawker 

Beechcraft Premier, both aircraft being certified under part 23. We are 

including all of the part 25 aircraft accidents because of the similarity 

between aircraft and operations. Furthermore, we consider this to be a more 

significant problem for part 23 because of the desire to use smaller airports 

with shorter runways for our operations. 

The following accident charts give a breakdown of accident categories, 

including runway overruns, broken down by business jet (bizjet), 

turboprops, and piston twin aircraft. The business jet accident data came 

from the May 2004 Flight Safety Digest article entitled “Controlled Flight 

into Terrain Takes Highest Toll in Business Jet Operations.” The accident 

series for turboprops is from FAA-NASDAC compilation of NTSB 

accidents for the Beech 90, 200, 300 and 1900, and the Cessna 425 and 

441, series airplanes. The accident data for the reciprocating twins is from 

the same source and includes the Models Beech B-58, Cessna 310 and 320, 

and Piper Aerostar airplanes. The NTSB data spans the years 1994 through 

2003. 

Courtesy of pilotoutlook.com 

57 
Bizjet Accidents - Serious Injury

Autopilot Upset/Disconnect

8%

CFIT 

8%

Elevator/Trim Jam or Loss

8%

Collision w ith Object - Ground

8%

Turbulence

31%

Ran Off Runw ay 

37%

Bizjet Accidents - Minor Injury

Ran Off Runway 

54%

Loss of Control 

23%

Landed Short of 

Runway

23%

58 
Turboprop Accidents - Serious Injury

Fuel Starvation

15%

Loss of Control - Stall 

15%

CFIT 

8%

Fuel Exhaustion 

8%

Ran Off Runw ay 

8%

Gear Failure Hard Landing

8%

Passenger Fell While Deplaning

23%

Collision w ith Object - Ground

15%

Piston Twin Accidents - Minor Injury

Elevator/Trim Jam or Loss

CFIT 3%

3%

Engine Fire

3%

Pilot Incapatation

3%

Landed Hard - Damage

3%

Collision w ith Object - Ground

3%

Collision w ith Object - Airborne

3%

Fuel Exhaustion 

7%

Fuel Starvation

10%

Loss of Control - Stall / Departure

13%

Ran Off Runw ay

21%

Engine Failure - Forced Landing

14%

Gear Failure / Up / Retracted

14%

59 
Issue: Pilot’s lack of understanding on how AFM landing distances are determined 

can indirectly result in runway overruns on minimum length fields. Landing 

overruns on minimum length fields could be prevented by providing information in 

each airplane AFM explaining how landing distance will increase when: 

• Flying at speeds in excess of VREF 

• Flying at an altitude greater than 50 foot over the end of the runway 

• Finessing the controls for a smooth landings by increasing the landing 

flare time 

• Maximum braking capability is not used 

5.1.6 Recommendation 

Provide information to pilots in the AFM regarding landing distance 

performance determination methods for type certification, for each specific 

airplane model. Also publish information explaining how different 

techniques can affect landing distance. These can be simple “rules-ofthumb” or calculated analytically. However provided, pilots need to be 

aware that successful minimum field length landings are controlled hard 

landings and most normal landings will require more runway. 

Issue: The lack of adequate type rating and recurrent training by pilots on minimum 

length field operations (both dry and contaminated) may contribute to the numerous 

runway overruns on small jet airplanes. Landing distance overruns continue to be a 

large percentage of the non-fatal small jet accidents including part 23 jets. The 

Takeoff and Landing Performance Assessment (TALPA) Aviation Rule-making 

Committee (ARC) is currently discussing additional runway performance data 

requirements to help mitigate overrun accidents. 

It is the opinion of the working group that if pilots could see how the airplane 

decelerates / performs on a minimum length field they would be more conservative 

in their selection and determination of an acceptable landing runway. Also, the 

rejected landing procedures for a minimum length field should be reviewed before 

landing in the event that a brake failure is experienced. 

5.1.7 Recommendation 

Type training for small jets does not expose the pilot to minimum field 

length runways, dry or wet. Pilot type training should require landing 

experience on minimum field length runways, preferably in the simulator, 

but if not, then on an actual runway. Ideally, a runway with distance 

markers should be used to allow the instructor and pilot to relate actual 

distances to the AFM data. 

The working group recommends placing more emphasis on landing 

distances for other than dry runway so that pilots are aware of how much 

60 
longer landing distances can be with contamination like rain or snow. At a 

minimum, provide factors for the different surfaces and contaminants. 

The landing distance factors recommended in the FAA Flight Test Guide 

for grass runways comes from research on grass runways done by the 

British CAA. These factors are considered conservative. Some 

manufacturers do include wet runway data in the form of a conservative 

landing distance factors. Conservative factors are a safe approach because 

the problem with providing data for wet, rain, snow, and ice is 

differentiating the precise amount of each contaminant there is on the 

runway. Landing distances vary significantly based on the type and amount 

of contaminant on the runway. Lack of information on how runway 

contaminants affect landing distance would adversely impact the pilots risk 

management and aeronautical decision making (ADM) capabilities. It 

should be noted that turbine-powered aircraft greater than 6000 MTOW are 

limited to operations on tested and approved types of runways for that 

specific aircraft. This includes paved runway, gravel runway, or sod 

runway operations. 

Supporting historical data: 

Nine overruns by small jets were primarily attributed to runway 

contamination; none caused deaths or serious injuries. Three of them also 

involved inoperative equipment or systems failures. In addition to the 

overruns, at least two jets lost directional control on snowy or slushy 

runways, a Dassault Falcon 20 and a Citation 551. 

Actual accident narratives are included in Appendix D under this 

recommendation number. 

Issue: Pilots of commuter category turboprops and multiengine jets may not be 

aware of the heat and subsequent brake fire that can result from a maximum 

performance stop such as in a rejected takeoff. Certification requirements only 

require that the brakes stop the airplane and burn slow enough to allow the 

occupants to get out of the airplane. Section 21(b)(6) of AC23-8B states “Following 

the stop at the maximum kinetic energy level demonstration, it is not necessary for 

the airplane to demonstrate its ability to taxi.” It also states “A satisfactory afterstop condition is defined as one in which fires are confined to tires, wheels, and 

brakes, and which would not result in progressive engulfment of the remaining 

airplane during the time of passenger and crew evacuation. The application of fire 

fighting means or artificial coolants should not be required for a period of five 

minutes following the stop.” Not understanding the fire risk from a maximum 

performance stop could affect the pilots risk management and aeronautical 

decision-making. Additionally, fires have occurred on smaller part 23 airplanes. 

Pilots may not be aware that if the conditions are just right, they could have a brake 

fire. 

61 
5.1.8 Recommendation 

For commuter category turboprops and multiengine jets, provide pilots 

information during type training and document the information in the AFM 

explaining that in an extremely high energy rejected takeoff situation that 

there is a potential for a wheel, tire and/or brake fire. It should be made 

clear to pilots that a wheel, tire and/or brake fire is possible if not highly 

probable following a maximum energy rejected takeoff. Also, the AFMs 

for all part 23 airplanes should include some discussion that under the right 

conditions they could have a brake fire and that care should be exhibited by 

the pilots to avoid those conditions. 

Issue: Many pilots are not aware of the specific regulatory requirements that result 

in center of gravity (CG) and weight limitations nor are they aware of the 

consequences of not observing these limitations. There may also be some belief 

among pilots that there is conservatism built into the CG limits. This is a disconnect 

between flight test and operations because there is not any conservatism in the CG 

limits developed from flight test. Pilots should have a general understanding of how 

weight and CG limitations are determined and what they mean (i.e., the reasons for 

aft and forward CG limits, the reasons for a maximum takeoff weight, and the 

reasons for a maximum landing weight.). Generally, controllability is the issue that 

limits the most forward CG and stability the issue that limits the most aft CG. The 

maximum takeoff weight and landing weights may be limited by structural and/or 

aircraft performance requirements. 

5.1.9 Recommendation 

Develop training discussions to explain how CG limitations are based on 

part 23 stability and control requirements, and how performance and 

structural requirements are associated with the limits of takeoff and landing 

weights. The training also needs to emphasize the consequences of not 

observing these limits. 

Supporting historical data: 

Accidents attributed primarily to out-of-limits CG are rare; almost all 

accidents that contain the NTSB code for “aircraft weight and balance” 

refer to aircraft being operated over certified maximum gross weight. Of 

150 accidents in certified airplanes between 1998 and 2007, only 6 are 

included in Appendix D. In those six accidents, CG was the primary 

accident cause or played a major role in the accident such as the disastrous 

crash of a Beech 1900D on take-off that was caused by the combination of 

an aft CG and a rigging error that severely limited elevator travel. 

62 
Worth mentioning (although outside of the 10 year historical data period) is 

the 1987 crash of a Homer Alaska crash of a Raytheon (Beechcraft) 1900C 

that resulted in 18 fatalities. On November 23, 1987, the Beechcraft 1900C, 

on approach to land, crashed short of the runway. The CG was 8 to 11 

inches aft of the allowable aft limit. The aft CG was deemed to be one of 

the probable causes of the accident. (NTSB number DCA88MA005) 

The future direction:

Actual accident narratives are included in Appendix D under this 

recommendation number. 

5.2 Finding 5.2 

Avionics and 

aircraft systems in 

part 23 airplanes are 

offering more 

features and 

integration of these 

features. There is a 

broad range of 

system complexities 

offered in part 23; some intuitive and others 

non-intuitive for pilots. 

Courtesy of Garmin 

Not all airplane and avionics designers have considered the pilot-machine interface 

by using good human factors practices. General aviation needs airplanes that are 

intuitive to operate, requiring as little training as possible. 

Issue: The majority of part 23 airplanes are single pilot. Furthermore, most part 23 

airplanes operate under part 91 and don’t require airplane specific training or 

equipment specific training. As new integrated systems continue to add features, the 

pilot usability gets harder. Some manufacturers improve each new system or system 

update so that they are getting easier to use. In other cases, equipment designed for 

two-person crew, part 25 airplanes is installed on single-pilot part 23 airplanes. 

While not all part 25 equipment is hard to use, part 25 equipment manufacturers 

take advantage of required training to mitigate poor human factors designs. Since 

part 23 does not have the training requirement, part 25 designed equipment should 

not automatically be accepted in part 23. 

Installing part 25 equipment could result in a high workload for single-pilot 

operations. An adequate minimum crew determination may find that with the same 

equipment, as on two-crew airplanes, some part 23 single-pilot airplanes could also 

result in the need to require two pilots. 

63 
5.2.1 Recommendation 

Improve the minimum crew determination requirements to provide clear 

discriminators for pilot workload. These discriminators would be used 

when performing the part 23 evaluations for single-pilot minimum crew 

operations. 

Issue: Human performance is a dominant factor in GA accidents. Design 

techniques and safety assessments do not always adequately address the subject of 

human error in operations. We can have the biggest influence on safety by 

designing error tolerant systems. 

5.2.2 Recommendation 

Incorporate better human-performance based designs in new airplanes or 

new avionics to make airplane operation more error tolerant. 

 

Issue: Humans will continue to push buttons when they don't see any signs that the 

machine recognized their first button push. This happens all the time with 

computers, sometimes causing the computer to lock-up. Pilot/airplane interfaces 

should be required to provide immediate feedback to the pilot that the system is 

working on the pilot’s action. Pilots should never be in the position of waiting to 

see if the system took their request. 

5.2.3 Recommendation 

There should be an obvious cue for the pilot any time the pilot pushes a 

button or switch and expects a resulting operation to occur. If the system 

doesn’t respond in a timely manner, the aircraft should display an 

appropriate alert or warning so the pilot knows the requested operation did 

not occur. The pilot could subsequently follow proper abnormal or alternate 

procedures for the resulting condition. 

64 
Conclusions

The objective of the part 23 Certification Process Study was to assess, from the part 23 

certification perspective, the adequacy of the current airworthiness standards throughout a small 

airplane’s service life. The study was not limited to certification standards. Study team members 

reviewed other areas affecting general aviation, such as pilot training, operations, and 

maintenance. 

The study offers a variety of short term and long term recommendations. These 

recommendations serve as the basis for the upcoming part 23 Regulatory Review (currently 

scheduled for FY10). It has been over 20 years since the last part 23 regulatory review. Not only 

is it time for a complete review of part 23, it is time to review the original assumptions for part 

23, including operations and maintenance. The airplanes being certified today have changed 

significantly since the inception of part 23 and this evolution will likely continue. 

The study identified 22 findings from five categories: 

• Performance Based Standards 

• Certification 

• Continued Airworthiness 

• Data Management 

• Pilot Interface 

Given that the general aviation fleet comprises over 200,000 airplanes, the majority of the 

recommendations from this study focus on keeping the existing fleet safe. This includes 

upgrading and maintaining airplanes with better systems (alternators for example), newer 

avionics (for NextGen, navigation, information, or redundancy), and safety gear (ballistic 

parachutes and inflatable restraints). Furthermore, as airplanes continue to operate past the halfcentury point, lack of parts or used parts and their airworthiness becomes a significant issue. 

Several recommendations address this issue. 

Beyond the existing fleet, the study team was asked to review part 23 (from a top level 

perspective) and make recommendations based on current and expected future products. 

Specifically, the study team was challenged to determine what part 23 should look like, given 

today’s current products, and projecting out twenty years from now. The teams thinking led to 

one of the major recommendations from the study: restructure part 23 into performance and 

complexity based divisions instead of today’s weight and propulsion based divisions. 

65 
Appendix A - Team Members 

Name Organization 

Arnold Spinelli FAA-AEG-KC 

Barry Ballenger ACE-110

Bob Stegeman ACE-111 structures 

Cora Byrd Working Group Lead ACE-113 COS

David Kenny Air Safety Foundation 

Dennis Beringer FAA CAMI 

Dr. Bill Johnson FAA AIR-100 

Eli Cotti NBAA 

Gerald Baker ACE-117W test pilot

Greg Bowles GAMA 

H. G. Frautschy Working Group Lead EAA Vintage Aircraft 

J.J. Greenway Air Safety Foundation 

James Brady ACE-111 systems

Jeffrey S. Gruber Professional Aviation 

Maintenance Association 

John Hopkins EAA Vintage Aircraft 

Leisha Bell Working Group Lead AOPA 

Lowell Foster Team Lead ACE-111 flight test 

Marty Bailey AFS-340 

Mike Lenz AFS – 810 

Pat Mullen ACE-111 Manager

Paul Nguyen ACE-117W COS 

Pete Rouse ACE-111 propulsion

Ric Peri Working Group Lead AEA 

Rick Baldwin ACE-113 COS 

Stan Mackiewicz Consultant 

Tausif Butt ACE-111 Propulsion 

Terry Pearsall AFS-350 

Tom Glista AFS-800 

Walter Desrosier GAMA 

66 
Appendix B - Charter

Small Airplane Certification Process Review Team Charter 

Team Sponsor: John Colomy, Standards Office manager, ACE-110 

Background 

The number of small airplane accidents in the US has finally started a downward trend after 

years of being essentially flat. This improvement in safety is probably the result of new 

equipment and information available to the pilot as well as aggressive pilot information 

dissemination and training programs. Changes in the FAA’s small airplane certification and 

operation were a direct result of the Safer Skies safety initiative in the late 1990’s and early 

2000’s. This initiative reviewed past accident types for root causes, future safety hazards, and 

addressed specific safety interventions to be implemented. Current downward trends may be 

related to the implementation of those safety interventions. 

Even with current improvements in small airplane safety, the FAA believes that further safety 

gains may come from examining the overall processes that are being applied during the 

airplane’s airworthiness activities, and evaluate how these activities interrelate of the in-service 

operation and maintenance of the airplane. As the US general aviation fleet passes the average 

age of 40 years, the processes for continued airworthiness will become more important. Also, 

almost all new airplane designs incorporate all electric, integrated systems using databus 

architectures. These airplanes will challenge traditional airplane maintenance, training, and 

modifying practices. 

This review, intended as a separate but complimentary effort to Safer Skies, will study the 

processes and procedures that are currently being applied during the various activities associated 

with the airplane airworthiness programs, and to examine how these activities interrelate to the 

maintenance and operation programs (including training) that are being applied in service. 

Objective 

The objective of this team is to assess the adequacy of the various operations and airworthiness 

processes that are currently in place throughout the airplane’s service life, and, if appropriate, to 

identify opportunities for process improvements. 

The team will: 

• Make recommendations for long-term improvements; and 

• Encourage implementation of near-term, easy to address improvements 

67 
Team Tasks 

The team’s tasks are broken down into three phases. 

Phase One – Information Gathering 

• Identify all of the major airworthiness processes, procedures, and policies that are being 

applied throughout the entire small airplane lifecycle. 

• Identify major “myths” between the different areas of certification, maintenance, and 

operations. For this effort, myths are widespread misunderstandings about how 

something is done. For example, actual structural safety margins verses the certified 

limits or parts life. Not all CAR 3/part 23 airplane structures are designed using the same 

approach. CAR 3 or older airplanes may have more “margin” in their structure than new 

part 23 airplanes. The question is could this effect how these airplanes are maintained in 

the future? 

• Identify all relevant general aviation safety/accident studies that the team can use and 

determine if any additional studies need to be done. 

Phase Two – Information Analysis 

Analyze the information from phase one: 

• To evaluate the various processes, how they interrelate with different organizations from 

a functional and objective standpoint. Include the AD process and the QMS process. 

• To identify areas where process improvements may be justified. 

• To look at changes in the GA accident profile, if any, and try to assess what new things 

work and what new things could be improved. 

• To evaluate the various processes and identify those where there is not a good safety 

return on the investment, and propose recommendations. 

Findings from these studies will be evaluated relative to current processes and practices 

implemented after the earlier studies were conducted. 

Phase Three – Report Writing 

• Document the analysis, findings, and observations associated with the certification and 

continued airworthiness processes applied during a small airplane’s life cycle. 

• Make recommendations in areas where the team’s findings and observations indicate a 

need or opportunity for process improvement. 

68 
Product 

The final deliverable is a report, to be submitted to the Associate Administrator for Aviation 

Safety, AVS-1, documenting the analysis, findings, and observations of the team’s review. 

Membership 

The Small Airplane Certification Process Study team will include representatives with 

appropriate technical background from the FAA and the US aviation industry. The FAA will 

serve as chairman of the study team and will functionally report to the Manager of the Small 

Airplane Directorate. 

Schedule 

The team will commence their study in February 2008. The team will deliver an interim draft 

report on their study in August 2008. 

69 
Appendix C - Suggested Expansion Subjects for 14 CFR 21.3 Requirements 

System Description

This is a system that the design/production approval holder uses to monitor, share 

information, and manage the safety performance of their civil certified products 

throughout the entire service cycle of the product. The system also is a measurement 

mechanism that provides visibility into the health of the entire design, fabrication, 

certification and operation of the product in real-time. 

A. General 

1. An event, failure, or condition (or combination of events failures, or conditions 

occurring in a single flight) that resulted in, or could have resulted in a hazardous 

or catastrophic effect on an airplane. 

2. For flight critical redundant systems, an event, failure, or condition (or 

combination of events, failures, or conditions occurring in a single flight) that 

resulted in a loss of more than one layer of protection in the system, or that 

resulted in only one remaining layer of protection in the system must be reported. 

3. Any aircraft operation or related event where serious injury or death occurs. 

4. Any incident or accident known by to be under investigation by the National 

Transportation Safety Board or a foreign government. 

5. Any event where the airplane departs a runway or taxiway including a failure 

occurring during any previous phase of flight. 

6. Unannunciated fire protection system failures (latent failures of fire detection 

systems, extinguishing systems, firewalls or fire seals, drain lines, fluid shut-offs, 

etc). 

7. Incorrect, misleading, or confusing flight deck indications that could have hazardous 

effects. 

B. Airplane Handling Characteristic

"Unusual" airplane handling characteristics, not in concert with 14 CFR part 

23 requirements and/or the Airplane Flight Manual (AFM) 

• Controllability (including airplane-pilot coupling) 

• Maneuverability 

• Trim 

• Stability 

• Stall warning/characteristics 

• Vibration and buffeting 

Significant pitch, roll or yaw upset/uncommanded motion, not to include 

"normal" turbulence or wake vortex encounter. 

70 
Significant degradation in airplane handling characteristics during or following flight in 

icing conditions. 

C. Airplane Performance 

An airplane performance shortfall relative to the AFM level in one of the following areas: 

• Stall speeds/warning/maneuvering capability 

• Takeoff 

• Accelerate stop 

• Climb 

• Landing 

Significant degradation in airplane performance, relative to the icing certification basis, 

during or following flight in icing conditions. 

D. Structures 

1. The following occurrences must be reported as provided in 14 CFR 21.3(a) and (b). 

A significant defect or failure in aircraft primary structure caused by any 

autogenous condition (fatigue, under-strength, corrosion, etc.). 

i. An occurrence of corrosion, a crack, structural damage or failure of 

primary structure that is the subject of a service bulletin (SB) or 

airworthiness directive (AD), and is outside the scope of those documents 

or indicates that the inspections or modifications described by those 

documents are not adequate. 

ii. An occurrence of corrosion, a crack, multi-site damage, structural damage 

or failure of primary structure which is not covered by a SB or AD, and 

which, to maintain the safety of every airplane in the fleet, may require 

action to ensure that all airplanes are inspected for the condition. In making 

this decision, it must be considered that other airplanes in the fleet may 

have the same condition, and that, without fleet action, routine maintenance 

may not detect the condition for every airplane in the fleet. 

iii. Fuselage cracks, corrosion, or failures which result in sudden 

decompression. 

b. Any structural damage, defect, corrosion, cracks, or failures that result in 

departure of significant components from the airplane: 

i. Loss of engines. (§ 21.3 (c)) 

ii. Loss of components for which engine ingestion is possible. 

iii. Loss of flight control or high lift devices. 

iv. Loss of items of significant size or mass (e.g., landing gear doors, nacelle 

components). 

71 
c. Any abnormal vibration or buffeting caused by a structural or system 

malfunction, defect, or failure. 

E. Occupant Safety 

1. Conditions that would result in failure or delay of door/exit opening 

2. Potential for cargo or passenger door/exit opening during flight 

3. Conditions resulting in serious injury to operator personnel or passengers 

4. Seat failures that may result in serious injury or incapacitation of occupants 

5. Seat belt failure 

6. Uncommanded movement of pilot seats 

7. Under-strength monuments (i.e. galleys, lavatories) 

8. Failure of oxygen mask deployment 

F. Mechanical Systems 

1. Any event where multiple systems have been involved that intended to be 

independent and isolated. 

2. Duct or equipment rupture/burst that impact airplane or personnel safety. 

3. Uncontained high energy rotor failures. 

4. High Lift and Drag Control, Powered Flight Control Systems 

a. Any flight control system malfunction, defect, or failure which causes an 

interference with normal control of the aircraft for which derogates the flying 

qualities. 

5. Cargo Movement 

a. Unplanned operation of Power Drive Units in flight or on the ground. 

b. Incidents where the system activated without command or failed to restrain 

cargo as intended. 

6. Hydraulic Power 

a. Diversion due to multiple hydraulic system failure. 

b. A complete loss of more than one hydraulic power system during a given 

operation of the airplane. (21.3 item) 

7 Landing Gear Actuation and Steering 

a. Failure which prevents the extension or retraction of the landing gear. 

b. Failure of the landing gear uplock or downlock. 

8. Oxygen Systems and Equipment 

a. Chafing of electrical wiring on oxygen lines, bottles, and/or generators. 

b. Evidence of or potential for electrical current in oxygen lines. 

c. Un-annunciated loss of or potential loss of crew or passenger supplemental 

oxygen system. 

d. Failure of an oxygen system to function properly. 

9. Potable, Grey and Waste Water 

a. Rupture of potable wafer tank or waste tank. 

b. Leakage from water and waste system that may result in electrical failures, 

i.e., leakage from forward lavatory/galley into the E/E Bay or electrical 

connectors/components/wiring. 

72 
c. Leakage from the water and waste system that may result in ice formation 

that interferes with normal control of the airplane, such as ice on flight 

control cables/mechanisms. 

d. Leakage from the water and waste system that may result in formation of ice 

on the exterior of the airplane or in the service panel, where the ice may 

depart the airplane and pose a hazard to the airplane or persons/property on 

the ground. 

10. Tires, Wheels, Brakes, Braking Control, Antiskid 

a. Tire failures which result in system failures, occur after retraction of the 

landing gear, or result in separation of the wheel rims from the wheel body. 

b. Wheel fractures which result in tire pressure loss. 

c. Failure of the parking brake. 

11. Pneumatic Power 

a.Diversion due to pneumatic system failure. 

12. Air Conditioning, Ventilation, Ozone 

a. Inability to control the environmental temperature in the crew compartment or 

passenger cabin that impacts airplane or personnel safety during operation. 

This includes in-flight malfunctions that result in complete loss of fresh air 

ventilation for more than 30 minutes, crew compartment or cabin air 

temperatures exceeding 90 °F for more than 30 minutes, or impairment of 

flight crew or passenger injury. 

13. Electrical/Electronic (E/E) Cooling 

a. Complete loss of Electrical Equipment (E/E) Cooling airflow. 

14. Pressurization 

a. Cabin altitude exceeds 12,000 feet and/or the Oxygen masks automatically 

deploy. 

15. Fire/Smoke Detection, Extinguishing/Suppression, Penetration and Smoke 

Evacuation 

a. A bleed air duct leak not detected by the duct leak detection system. 

b. Failure to clear smoke from the cockpit 

c. Fire/smoke detection, extinguishing or prevention system failures which are 

undetected by BITE, system fault indications, or flight crew procedures. 

d. Failure of any air conditioning/ventilation system to properly 

reconfigure/shutdown during a fire event. 

16. Ice and Rain Protection/Detection 

Any known design latent failure of the anti ice system which is found. 

G. Electrical Systems 

1. Any failure or condition that results in uncommanded movement of any flight 

control surface or uncommanded flight control system or automatic flight 

system mode changes. 

2. Any failure or condition that results in loss of control of any flight control surface. 

3. Any failure or condition that results in a complete loss of more than one electrical 

power generating system during a given operation of the airplane. 

4. Any failure or condition that results in total loss of VHF communication. 

73 
H. Propulsion Systems 

1. Environmental, operational, or (common cause) failure conditions that adversely 

affected more than one engine, or that adversely affected one engine and could have 

adversely affected more than one engine. (However, bird strike events need not be 

reported under this item.) 

2. Failures or conditions that resulted in or could have resulted in an ignition source in a 

fuel tank. 

3. Engine separation, loss of thrust, loss of thrust control, uncommanded thrust 

change (including engine surge), engine flameout, or engine shutdown other 

than normal shutdowns at the end of an operation. (21.3 item) 

4. Failures that could significantly affect usable fuel, such as large fuel leaks or 

multiple boost pump failures. 

5. Failures or conditions that may significantly reduce propulsion system 

reliability or that may otherwise affect the safety of extended range missions. 

6. For thrust reverser systems, any event or condition (including those discovered 

during maintenance) which resulted from a failure or malfunction of more than one 

component in the system. 

74 
Appendix D - Accidents Supporting the Pilot Interface Recommendations

5.1.3 Supporting historical data for maneuvering speed and limit load understand issues 

In the ten years between 1998 and 2007, historical data contains eleven accidents in part 23 

aircraft, two in part 25 aircraft, and one in a manufacturer’s demonstrator kitplane advertised 

to be designed to part 23 standards in which excessive speed might have contributed to 

structural failures. Nine of the twelve accidents in small airplanes were fatal, but there were 

no casualties in either of the accidents in part 25 airplanes. 

There were also two accidents in which wings separated from high-time Beechcraft T-34s 

being used in simulated dogfights, though speed does not seem to have been implicated as a 

root cause of the event as much as the cumulative G-loading experienced during a long 

history of high-energy maneuvering, and the in-flight break-up of a Beechcraft Baron whose 

pilot attempted to roll the airplane with four passengers on board. The following list of events 

also excludes accidents in which excessive airspeed was secondary to a loss of aircraft 

control due to spatial disorientation or pilot incapacitation. 

Part 23 Airplanes 

• On June 7, 1998, a Mooney M20A broke up in flight while the VFR-only pilot 

attempted to dive through a hole in an undercast layer to make a visual approach. The 

pilot was killed; he had just purchased the airplane and had not yet obtained a 

complex endorsement. (NTSB number SEA98FA089) 

• On April 13, 1998, a Beechcraft B35 Bonanza experienced tail flutter at an indicated 

airspeed of 180 mph, causing damage to the right stabilizer and right ruddervator. A 

subsequent Airworthiness Directive (AD) reduced the Never Exceed Speed (VNE) for 

this and several similar models to 144 mph. (NTSB number CHI98LA125) 

• On May 5, 1998, a Mooney M20K, attempting to avoid thunderstorms and icing, 

attained ground speeds above 240 knots during descent. VNE for this airplane was 196 

knots. “The elevators fluttered and separated from the airplane. Thereafter, the 

stabilizers departed, the nose pitched downward, and both wings failed in a negative 

direction.” The pilot was killed. (NTSB number LAX98FA154) 

• On May 24, 1998, a RV-8 being used as a factory demonstrator lost the outboard 

section of the left wing during a demonstration flight; both occupants were killed. The 

narrative notes that “The kit was designed to meet the design standards of 14 CFR 

part 23.” The accident was attributed to damage suffered during an earlier flight; the 

flight testing regimen included aerobatics, but none were performed on the accident 

flight. The aircraft was within weight and CG limits but above the maximum weight 

for aerobatic maneuvers, and its maximum speed was almost 50 knots above VA. 

(NTSB number LAX98FA171) 

75 
• On July 30, 2000, a Beechcraft A35 suffered tail flutter after exceeding the revised 

VNE of 144 mph in a smooth-air descent. The AD had been complied with and the 

required placard and airspeed red-line had been installed. All four corners of the FS 

256.9 bulkhead were cracked, with consequent damage to the fuselage and 

empennage. The ruddervators were subsequently found to be out of balance. (NTSB 

number CHI00LA238) 

• On March 31, 2002, a Piper PA34-200 broke up during high-speed maneuvering 

while attempting to capture the localizer for an ILS approach. Ground speed reached 

211 knots, while VNE was 195 knots. The pilot and passenger were both killed. 

(NTSB number ATL02FA069) 

• On April 11, 2002, after aggressive maneuvering at speeds about 30 knots above VA, 

including a 90-degree bank, the tail of a Beechcraft G35 Bonanza separated from the 

airplane, followed by the left wing and the engine. The pilot and passenger were 

killed. (NTSB number LAX02FA134) 

• On December 25, 2002, a Beechcraft F-35 Bonanza experienced vibration while 

exceeding VNE during descent, slowed, and landed without incident. Structural 

damage was discovered after landing. (NTSB number ATL03LA031) 

• On March 21, 2003, one wing separated from a Cessna 172 Skyhawk during a 

high-speed descent at a roughly 45-degree nose-down attitude. The Certificated Flight 

Instructor (CFI) and student pilot were both killed. Insufficient radar data was 

available to estimate the airplane’s speed at the time of the break-up, but examination 

of the wreckage found fracture surfaces consistent with overstress, and no evidence of 

significant wear or corrosion. (NTSB number ATL03FA064) 

• On July 5, 2003, a Beechcraft F-35 Bonanza broke up while maneuvering around 

clouds for a visual approach. Data extracted from a handheld GPS showed that 

airspeed increased to 211 knots during the maneuvers, almost 40 knots above the 

published VNE of 173 knots. The pilot and passenger were killed. (NTSB number 

NYC03FA148) 

• On October 15, 2006, an Aero Commander 690A broke up in moderate turbulence 

during cruise flight at FL 230. Radar data suggested that it was flying 15-20 knots 

faster than the placarded maximum speed for moderate turbulence. All four on board 

were killed. (NTSB number DFW07FA004) 

• On December 8, 2007, a Cessna T210N broke up in flight during a descending turn, 

banked 40 to 50 degrees, at speeds 20 knots above its maximum structural cruising 

speed (but below VNE). The pilot and passenger were killed. The airplane was 

probably in Visual Meteorological Conditions (VMC) until just before the break-up, 

but the NTSB did not rule out the possibility of spatial disorientation. (NTSB number 

MIA08FA027) 

76 
Part 25 airplanes

• On December 01, 2006, a Learjet 36 lost its right elevator during maneuvering in 

which it reached 70 degrees of bank, 50 degrees nose down, and 380 KIAS. The 

airplane remained controllable afterwards and landed without further incident. (NTSB 

number LAX07TA051) 

• On January 10, 2007, the captain of a Learjet 35A attempted an aileron roll while 

descending through FL 200 and lost control of the aircraft, entering a nose-down 

unusual attitude. Excessive airspeed and G loads caused substantial damage to the left 

wing and elevator. (NTSB number CHI07CA058) 

5.1.5 and 5.1.6 Supporting historical data for understanding landing distance performance 

data 

Of 50 long landings contained in historical data during the ten years between 1998 and 2007 

attributed, in whole or in part, to excessive airspeed on final, thirteen involved relatively 

small jets. The said data includes single events involving a Cessna Citation 525A and the 

Hawker Beechcraft Premier, both aircraft being certified under part 23. Part 25 accidents are 

included because of the similarity between aircraft and operations. Furthermore, the team 

considers short runway operations to be a more significant problem for part 23 operators than 

part 25 operators because of operators wanting to use smaller airports with shorter runways. 

Part 91 operators who fly part 23 jets do not have additional runway length requirements that 

part 135 and 121 operators must meet. They may also fly to airports near their final 

destination and these airports may have shorter runways. 

Part 23 aircraft: 

• On October 7, 2002, following an unstabilized approach, the owner-flown Cessna 

Citation 525A touched down 22 knots fast with a 7-knot tailwind on a 3,009-foot 

runway. Examination of the landing runway revealed five distinct sets of skid marks; 

initial touchdown, three additional touchdowns on the runway, and the final set of 

skid marks as the airplane departed the runway. The configuration of the skid marks 

suggested that the aircraft may have landed with the brakes already applied. (NTSB 

number NYC03FA002) 

 

• On May 27, 2004, following an unstabilized approach the Hawker Beechcraft 390 

Premier I touched down 17 knots faster than the recommended approach speed. 

Wind conditions were 70 to 130 degrees off the runway centerline at 12 knots 

gusting to 18. Touchdown occurred about 650 feet from the approach end of the 

runway, and the airplane came to rest 735 feet beyond the departure end after going 

through a chain-link fence. Post-accident analysis suggested that the required 

landing distance at that speed was at least 500 feet greater than the runway length. 

(NTSB number DCA04MA049) 

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Part 25 aircraft:

• On January 06, 1998, the pilot in command (PIC) of the Cessna Citation 500 

described final approach speed as 20 knots above VREF; the SIC said it was 30 

above. The SIC claimed that it touched down prior to the 3,000-feet-remaining mark, 

but control tower staff said it was still airborne with less than 2,500 feet remaining. 

(NTSB number NYC98FA060) 

• On March 04, 1998, the flight data recorder (FDR) of the Citation 650 showed that 

the aircraft touched down at VREF +6 following a VOR approach over snowcovered terrain in one-mile visibility. Touchdown occurred 3,100 to 3,200 feet down 

the 5,502-foot runway. (NTSB number CHI98LA100) 

• On February 16, 1999, “During the descent from 8,000 feet, and within 13 miles of 

the airport, the airplane [a Gulfstream II] reached speeds over 300 knots and attained 

descent rates in excess of 4,000 feet per minute. At 1.5 miles from the runway and 

700 feet above the airport elevation, the airplane was descending at 3,000 feet per 

minute and flying over 200 knots. The reference speed was 138 knots with flaps 20 

during the approach and 125 knots for landing.” It touched down with about 3,400 

feet of an 8,001-foot runway remaining and continued for another 1,072 feet beyond 

the end before coming to rest. (NTSB number LAX99FA101) 

• On May 1, 2002, the captain of the Beech 400A was distracted by problems with the 

FMS and ignored two suggestions by the first officer that they go around because 

they were “VREF plus 40”. The airplane crossed the runway threshold 150 feet AGL 

at 166 knots and touched down with about 1,000 feet of runway remaining. (NTSB 

number IAD02FA047) 

• On September 19, 2003, the Learjet 25B maintained a groundspeed of 190 knots, or 

VREF +74, on a visual approach to a 5,000-foot runway. Touchdown occurred in the 

last 2,000 feet of the runway; tire marks indicated that the anti-skid system was 

operative. The airplane was not equipped with thrust reversers. The captain was 

killed and the first officer was seriously injured. (NTSB number FTW03FA229) 

• On January 24, 2006, the Cessna Citation 560 flew the final approach at about VREF 

+30 and touched down 1,500 feet beyond the target zone of the 4,897-foot runway 

with a 6-knot tailwind. The pilot did not attempt to go around until asked about it by 

the first officer; the aircraft lifted off prior to the end of the paved overrun but struck 

a localizer antenna platform 304 feet beyond the departure end, causing four 

fatalities. (NTSB number SEA06MA047) 

• On July 10, 2006, the pilot of the Cessna Citation 560 increased the approach speed 

to VREF +10 to counter perceived wind gusts and flew a flatter than usual descent 

path. Touchdown was at or beyond the halfway point of the 4,200-foot runway. 

Prevailing winds were five knots or less, and neither the witnesses present nor the 

archived METARs reported significant gusting. (NTSB number SEA06LA138) 

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• On January 24, 2007, the Cessna Citation 550 remained on glideslope and localizer 

after breaking out of the clouds on an ILS approach to a 4,801-foot runway. 

Witnesses described it as “high and fast,” and data from the Enhanced GroundProximity Warning System (EGWS) indicated that it touched down at about 140 

knots, or VREF +30. The runway was covered in about a half inch of loose snow; 

braking action was reported “fair”. The AFM prescribed a landing distance of 5,800 

feet on a snowy runway at 110 knots, 7,800 feet at 120. (NTSB number 

NYC07FA058) 

• On March 23, 2007, the crew of the Dassault Falcon 900C reported flying the 

glideslope at VREF +10 below 1,000 feet. A performance study suggested that it 

crossed the threshold at VREF +22 and touched down 2,300 feet down the wet 

runway, which also sloped downwards 1.25 percent. The accident narrative noted 

that 12 business jets have had overruns on that runway since 2001, all but one in wet 

conditions. However, the others did not turn up in a search for codes indicating 

excessive airspeed. (NTSB number DEN07LA078) 

Only the late go-around in the Cessna Citation 560 and the extremely fast approach in the 

Lear 25B caused fatalities, and only one of the 37 accidents in piston aircraft was fatal. 

Detailed airspeed data is generally not available for the piston accidents, but most of the 

pilots admitted to being “high and fast”. These overruns represent less than 1% of all 

landing accidents over the ten-year period. 

5.1.7 Supporting historical data for understanding landing distance performance data for 

wet and contaminated runways 

Nine overruns by light jets and two in commuter turboprops during this period do not 

appear to have been primarily due to either excessive airspeed on final or contaminated 

runway surfaces. All four of those in part 23 aircraft (two CitationJet II, a Jetstream 4101, 

and a Beechcraft 1900D) were purely pilot-induced; four in part 25 aircraft involved 

possible or definite mechanical failures (with excess speed also a possible factor in one of 

those). Another involved a long landing on a runway that was also slippery from snow. 

Included in this section are five accidents that occurred in the 2008 – 2009 timeframe. 

Although outside the ten years between 1998 and 2007 used for the majority of the 

supporting historical data, the five accidents were deemed to be important examples of 

runway overruns on both dry and contaminated runways. 

Part 23 aircraft: 

• On December 29, 2000, a Jetstream 4101 touched down on speed about 1,900 feet 

past the threshold of a 6,001-foot runway. The captain moved the power levers into 

the reverse range, but when a red BETA light illuminated, he inadvertently moved 

them past the BETA range to flight idle, producing positive thrust. Braking power 

was insufficient to stop the airplane on the runway. (NTSB number IAD01FA021) 

79 
• On February 7, 2002, following a GPS approach, the pilot of the Cessna Citation 

525A touched down about one-third of the way down a 3,300-foot runway with a 

quartering tailwind gusting to 17 knots. He deployed ground flaps and spoilers 

braked hard, and then decided to go around after concluding that the airplane was 

not decelerating normally. He applied full power for the go-around but neglected to 

retract the flaps and spoilers, and the airplane went off the end of the runway into a 

ravine. Cessna estimated that the distance required to land with a 10-knot tailwind 

was 3,400 feet. (NTSB number LAX02FA075) 

• On May 15, 2005, following a low pass over the runway, the Cessna Citation 525A 

touched down 1,000 feet beyond the threshold of a 2,948 runway with a 10-knot 

tailwind. Landing performance charts indicated that it required 3,000 feet of landing 

distance with no wind and 3,570 feet with a tailwind component of 10 knots. The 

published airport diagram (found attached to the pilot’s control column) and the 

A/FD both noted that the airport was closed to jet traffic. (NTSB number 

NYC05LA085) 

• On Wednesday, June 20, 2007, a Beechcraft 1900D crossed the threshold of the 

6,303-foot runway “one dot high” and about 4 knots above VREF. It touched down 

about 2,500 feet past the threshold, bounced, and touched down again about 1,000 

feet further along. The captain held the nose wheel off the runway for what struck 

the first officer as an unusually long time before lowering it and beginning to brake. 

The right propeller hit an electrical box as the captain attempted to make a highspeed turn onto the last taxiway to avoid running off the end of the runway. (NTSB 

number DEN07LA101) 

• On February 12, 2008, the Beech 390 Premier I touched down at 100 knots near the 

threshold of the 5,500-foot runway. Braking action was initially adequate but 

decreased to nil by mid-field, and the airplane departed the left side of the runway 

and hit a drainage ditch. The runway was covered in black ice with a thin layer of 

water; airport staff had neither treated the ice nor reported it by NOTAM. (NTSB 

number NYC08LA099) 

 

• On April 19, 2008, the Cessna 510 Mustang crossed the threshold about 15 knots 

fast and touched down more than halfway down the 4,897-foot runway. Rather than 

allow it to run off the end of the runway, the pilot attempted a 180-degree turn, 

causing a ground loop and collapsing the main landing gear. The pilot later reported 

being fatigued from hand-flying the airplane for about 45 minutes following failure 

of both the autopilot and the electric pitch trim. (NTSB number LAX08FA117) 

80 
• On July 30, 2008, the Eclipse EA-500 was, in the pilot’s words, “a little high” and “a 

little fast” on approach to the displaced threshold of a runway with a usable length of 

3,097 feet. The airplane began to skid under full braking and went off the end of the 

runway, down a 40-foot embankment, and across a service road before hitting a 

chain-link fence and trees. Skid marks began 868 feet from the threshold and 

continued for the remaining 2,229 feet of the pavement. The runway was dry asphalt 

in good condition; the pilot held an airline transport pilot’s certificate with type 

ratings for three models of business jets including the EA-500 and about 6,300 flight 

experience. (NTSB number NYC08FA261) 

Part 25 aircraft: 

• On May 23, 1998 a hydraulic leak caused the braking system of the Learjet 24B to 

fail during the landing roll. The first officer made repeated applications of the 

emergency brake rather than maintaining steady pressure, causing evacuation of the 

nitrogen. The airplane ran off the end of the runway and collided with the ILS backcourse antennae. (NTSB number ATL98LA078) 

• On February 18, 1999, following a circling VOR/DME approach, the Mitsubishi 

MU-300 overshot the turn to final approach and banked sharply to recover position, 

then landed more than 3,000 feet down a snowy 5,680-foot runway. The runway had 

just been plowed, but braking action was reported as “poor”. (NTSB number 

CHI99LA093) 

• On April 17, 1999 the Beechcraft Beechjet 400A touched down about one-third of 

the way down a 5,000-foot runway, but the captain was unable to move the thrust 

reverser lever past the “deploy idle” position. Maximum braking failed to stop the 

aircraft before the end of the runway and it slid down an embankment. The crew had 

deliberately increased their approach speed out of concern for strong, gusty winds. 

(NTSB number NYC99FA091) 

• On May 2, 2002, a Cessna Citation 560 touched down about 2,100 feet beyond the 

threshold of a 3,975-foot runway and slid off the departure end after the right tire 

began sliding. Total required landing distance (air and ground) was estimated at 

2,955 feet. (NTSB number FTW02LA136) 

• On August 13, 2002, a Citation 550 touched down hard about halfway down a 

5,260-foot runway with an 8-knot tailwind. Witnesses and passengers said it 

porpoised repeatedly before going off the end of the runway. (NTSB number 

LAX02LA252) 

• On August 30, 2002, a Learjet 25C touched down 1,000 to 1,500 feet down the 

7,033-foot runway. Required landing distance was calculated to be 3,400 feet with 

anti-skid inoperative. The captain was unable to deploy the thrust reversers, and the 

CVR suggested that he may have inadvertently increased thrust for a few seconds. 

Toe brakes and emergency brakes failed to stop the airplane before the end of the 

81 
runway. One passenger was killed; the second passengers and all three crew 

members were seriously injured. (NTSB number NYC02FA177) 

• On February 17, 2004, damage to the hydraulic system of a Learjet 25B caused by 

improper maintenance prevented the flaps from extending beyond 8 degrees and 

rendered the brakes inoperative. The airplane landed about halfway down a 6,001-

foot runway. The first officer was unable to deploy the drag chute, but neither pilot 

attempted to use the nitrogen-charged emergency brakes. The airplane was not 

equipped with thrust reversers. (NTSB number ANC04FA026) 

• On June 24, 2006, following an unstabilized approach at night, a Cessna 560 flown 

by the owner of the charter company touched down about 1,400 feet along a 

3,864-foot runway at his home field and overran the departure end by 851 feet. 

Witnesses heard the thrust reversers deploy and then stow again. Subsequent 

performance calculations suggested that the aircraft needed a further 765 to 2,217 

feet of runway to reach a full stop. One passenger died from injuries sustained in the 

accident. (NTSB number LAX06FA211) 

Several overruns on contaminated runways also involved excessive airspeed on final 

approach and are listed under 5.2.3 above: See NYC07FA058 and DEN07LA078 above. 

Nine overruns by small jets were primarily attributed to runway contamination; none caused 

deaths or serious injuries. Three of them also involved inoperative equipment or systems 

failures. Only one of these airplanes appears to have been certified under part 23. In addition 

to the overruns, at least two jets lost directional control on snowy or slushy runways, a 

Dassault Falcon 20 and a Citation 551. 

Part 23 aircraft: 

• On July 17, 2005, the runway was wet, it sloped downwards 0.6% and a displaced 

threshold reduced the available landing distance to 3,194 feet. The Citation 525 

touched down about one-third of the way down, and, after failing to decelerate, 

attempted a go-around with about 1,000 feet remaining. At 107 knots, the airplane 

would have required 3,550 feet to stop on a level wet runway, and it may also have 

been fast: The pilot claimed that he flew the final approach at 115 knots slowing to 

108, but data from the EGWS suggested that the airplane was traveling at 133 knots 

0.1 nm from the threshold. The aircraft overran the runway during the failed 

go-around attempt. (NTSB number IAD05LA099) 

On December 21, 2008, the Dassault Falcon 20 overran the end of an icy 5,299-foot 

runway and stopped about 100 feet into the overrun area after the nose gear hit a 

snow berm. A NOTAM reported “patchy snow and ice;” the pilot described the 

runway as “ice-covered” and reported braking action to be nil. (NTSB number 

ERA09LA282) 

82 
• On December 23, 2008, the Beech 390 Premier I touched down at 110 knots on a 

wet 4,370 feet runway. The brake anti-skid system appeared to be working, but the 

airplane was unable to stop and went off the south end of the runway, over an 

embankment, and stopped next to a levee. The flight manual estimated that 3,400 

feet would be needed to land on a wet runway at a reference speed of 111 knots. 

(NTSB number CEN09LA100) 

Part 25 aircraft: 

• On July 01, 1999, during gear extension, the Learjet 60’s left and right HYDR 

PRESS lights illuminated due to a leaking main gear actuator hose. The crew chose 

to land on the wet 5,425-foot runway at their original destination rather than 

diverting. The brakes, thrust reversers, and captain’s emergency brake all proved 

inoperative; the first officer was able to engage his emergency brake just after the 

captain announced a go-around. The AFM stated that calculated landing distance 

should be tripled if flaps, spoilers, thrust reversers, and anti-skid were unavailable; in 

this case, that would have been more than 11,000 feet. (NTSB number 

NYC99LA151) 

• On January 27, 2000, during an instrument approach in moderate clear icing, the 

horizontal stabilizer heat of the Mitsubishi MU-300 failed. In accordance with the 

abnormal procedures checklist, the pilot configured the airplane for a touchdown 

speed of 120 knots with 10 degrees of flaps. It touched down about 1,500 feet down 

a slushy, 7,753-foot runway and slid another 3,000 feet before obtaining any braking 

effectiveness or anti-skid. The remaining 3,253 feet was 192 feet shorter than the 

distance required to land on a dry runway. (NTSB number FTW00LA084) 

• On March 12, 2000, the Learjet 60 landed on an icy 6,299-foot runway sloping 0.6% 

downhill with its thrust reversers disabled due to a maintenance discrepancy. The 

captain used the emergency brakes, which disabled the anti-skid system, and the 

airplane ran off the end of the runway into two feet of snow. (NTSB number 

DEN00LA057) 

• On March 17, 2000, the Dassault Falcon 900 touched down about 2,640 feet down a 

5,425-foot runway covered in snow and patchy ice with a tailwind component 

estimated at 20 knots. A Cessna 402 had reported braking action as “poor”. The 

AFM gave the maximum allowable tailwind component as 10 knots, and estimated 

the distance required to land on an icy runway with a 10-knot tailwind as 10,800 

feet. (NTSB number NYC00FA092) 

• On March 9, 2001, following an ILS approach, the Hawker-Siddeley HS-125-3A 

landed with about 3,200 feet of the 4,677-foot runway remaining. All surfaces were 

covered with thin wet snow, but braking action was reported as “good”. Toe brakes, 

emergency brakes, and the parking brake all failed to slow the aircraft significantly 

even though no mechanical anomalies were found after the accident. (NTSB number 

NYC01FA084) 

83 
• On February 26, 2001, the Citation 500 touched down one-third of the way down an 

ice-covered, 5,235-foot runway. Braking action had been reported as “nil.” After the 

airplane fish-tailed near midfield, the pilot attempted to go around but was unable to 

lift off before the airplane went off the end of the runway into the snow and down a 

small cliff. (NTSB number CHI01LA094) 

• On February 10, 2002, the 5,101-foot runway was covered in a thin layer of snow; a 

Hawker jet reported braking action as “poor”. The Mitsubishi MU-300 touched 

down with about 2,233 feet of runway remaining. Required landing distance on a dry 

runway was calculated to be 2,720 feet and proceeded to overrun. (NTSB number 

NYC02FA059) 

• On March 25, 2002, the MU-300 slid off the end of a 5,401-foot runway 

contaminated by snow and ice. A snowplow had reported braking action as “fair to 

poor,” but after the accident the captain claimed it was “nil”. In post-accident 

statements, both crew members reported a stabilized approach, but radar data 

indicated airspeed in excess of 200 knots between the final approach fix and the 

threshold, with a full-scale deviation from the localizer 5.5 nm from the localizer 

antenna. The CVR tape appeared to have been manually erased. (NTSB number 

CHI02FA097) 

• On July 19, 2004, following a short positioning flight, a Learjet 55 ran off a 4,000 

foot runway attempting to land in a developing thunderstorm that had reached VIP 

Level 5 by the time of touchdown. Reported conditions on the field included wet 

runways and a 25-knot wind shear. (NTSB number MIA04FA107) 

• On January 28, 2005, a Learjet 35A with inoperative thrust reversers slid off the end 

of a 7,002-foot runway on which about one quarter of an inch of snow had 

accumulated since plowing. The crew had calculated total landing distance as 5,400 

feet. A Cessna 210 had reported braking action as “moderate,” which the tower 

translated as “fair”. (NTSB number CHI05FA059 

• On December 05, 2004, the Dassault Falcon 20 landed about 2,450 feet down a wet 

5,998-foot runway. The captain reported hydroplaning, with no cycling of the antiskid system, and no evidence of braking was found on the runway. The airplane was 

not equipped with thrust reversers, and the drag chute was not deployed. (NTSB 

number DFW05LA030) 

• On October 17, 2005, the crew of the North American T-39A calculated takeoff and 

landing distances for a wet runway and crossed the threshold at 125 knots. Braking 

action seemed normal until the last 3,000 feet of the runway, after which the brakes 

became ineffective. NOTE: Since this is a military-model aircraft, I don’t know 

whether civilian certification standards applied; however, a civilian version has been 

certified. (NTSB number LAX06LA017) 

84 
Note: About 180 piston and turboprop airplanes ran off contaminated runways during the 

same 10 year period. This represents a little over 4% of all landing accidents during that time 

frame. A number of runway loss of control (RLOC) accidents also occurred on contaminated 

runways; in most years, RLOCs for all causes were seven to eight times as common as 

overruns. 

• On December 21, 2008, the Dassault Falcon 20 overran the end of an icy 5,299-foot 

runway and stopped about 100 feet into the overrun area after the nose gear hit a 

snow berm. A NOTAM reported “patchy snow and ice;” the pilot described the 

runway as “ice-covered” and reported braking action to be nil. (NTSB number 

ERA09LA282) 

• On December 23, 2008, the Beech 390 Premier I touched down at 110 knots on a wet 

4,370 feet runway. The brake anti-skid system appeared to be working, but the 

airplane was unable to stop and went off the south end of the runway, over an 

embankment, and stopped next to a levee. The flight manual estimated that 3,400 feet 

would be needed to land on a wet runway at a reference speed of 111 knots. (NTSB 

number CEN09LA100) 

5.1.9 Supporting historical data for CG related accidents: 

Accidents attributed primarily to out-of-limits CG are rare but notable. Of 150 accidents in 

certified airplanes between 1998 and 2007 that were reviewed under the NTSB code “aircraft 

weight and balance” most were related to weight or other contributing factors. A handful of 

these accidents, however, do highlight the potential severe nature of these accidents. 

Worth mentioning (although falling outside of the 10 year historical data period) is the 1987 

crash of a Homer Alaska crash of a Raytheon (Beechcraft) 1900C which resulted in 18 

fatalities. On November 23, 1987the Beechcraft 1900C was on approach to land, crashed 

short of the runway. The CG was 8 to 11 inches aft of the allowable aft limit. The aft CG was 

deemed to be one of the probable causes of the accident. (NTSB number DCA88MA005) 

Part 23 aircraft: 

• On March 31, 2001, a de Havilland DHC-3 Otter with 21 skydivers on board stalled 

upon take-off from a short, wet grass strip. The pilot blamed a dust devil, but the 

nearest weather observation facility reported clear skies and calm conditions. The 

airplane, which was placarded for a maximum of 9 passengers, was 1,118 pounds 

over its maximum gross weight with a CG almost 10 inches aft of limits. The pilot 

stated that the 9-passenger limit did not apply because skydivers were not considered 

passengers. (NTSB number FTW01LA091) 

85 
• On April 19, 2001, a Cherokee Six with four passengers on board had difficulty 

climbing after an intersection departure, and eventually stalled at about 300 feet agl. 

The airplane was estimated to be 8 pounds below its certified maximum gross weight, 

but the CG was at least four inches ahead of the forward limit; the forward baggage 

compartment, which was restricted to no more than 100 pounds, was loaded with 244 

pounds of cargo. (NTSB number MIA01FA126) 

• On September 25, 2002, a Pitts S-2C practicing aerobatics entered a tail slide no more 

than 2,500 feet AGL and entered an inverted spin, hitting the ground before it could 

complete a recovery. The airplane was estimated to be about 125 pounds overweight, 

with a CG about 1.3 inches aft of limits. (NTSB number CHI02FA294) 

• On January 08, 2003, a Beech 1900D crashed shortly after take-off, killing all 21 on 

board and causing minor injuries to one person on the ground. The accident 

investigation concluded that (a) inadequacies in the standard weight-and-balance 

calculations resulted in the airplane exceeding its MGTOW by 300 – 700 pounds with 

a CG aft of limits by 3.5 – 7.5% MAC, and (b) misrigging of the elevator control 

cables during a recent heavy maintenance deprived the airplane of sufficient elevator 

travel to counteract the resulting nose-up pitching moment. (NTSB number 

DCA03MA022) 

• On December 29, 2002, a Piper Cherokee Six that had been modified under an STC 

that restricted it to skydiving operations took off with three passengers and two dogs 

but only two passenger seats. Its CG was estimated to be 2.33 inches aft of limits. The 

airplane hit rising terrain at an elevation of 9,527 feet and a density altitude of 10,200 

feet after flying up a canyon with a 14- to 18-knot tailwind. (NTSB number 

DEN03FA028) 

Part 25 aircraft: 

• On February 02, 2005, Bombardier CL-600 was unable to stop on the runway after a 

rejected take-off and traveled through the airport fence, hit a vehicle while crossing a 

six-lane highway, and penetrated a building. The crew had never computed the 

aircraft’s CG. Calculations made during the investigation suggested that the CG was 

at about 12.47% MAC, significantly forward of the limit of 16% MAC. (NTSB 

number DCA05MA031) 

86 
Appendix E - List of Acronyms

AOPA Aircraft Owners and Pilots Association 

A/FD Digital Airport/Facility Director 

AC Advisory Circular 

ACO Aircraft Certification Office 

AD Airworthiness Directive 

ADM Aeronautical Decision Making 

ADS-B Automatic Dependent Surveillance Broadcast 

AEA Aircraft Electronics Association 

AEG Aircraft Evaluation Group 

AFM Airplane Flight Manual 

AFS Flight Standards Service 

AGL Above Ground Level 

AIM Airman's Information Manual 

AIR Aircraft Certification Service 

AML Approved Model List 

APA Administrative Procedures Act 

ARC Aviation Rulemaking Committee 

ASTM American Society for Testing and Materials 

ATP Air Transport Pilot 

BITE Built In Test Equipment 

BRS Ballistic Recovery System 

CAA Civil Aviation Authority 

CAMI Civil Aerospace Medical Institute 

CAR Civil Aeronautics Regulation 

CAR Civil Airworthiness Regulation 

CFI Certificated Flight Instructor 

CFIT Controlled Flight Into Terrain 

CFR Code of Federal Regulations 

CG Center of Gravity 

COS Continued Operational Safety 

CPS Certification Process Study 

CVR Cockpit Voice Recorder 

DER Designated engineering Representative 

DOT Department of Transportation 

E/E Electrical Equipment 

EAA Experimental Aircraft Association 

EFIS Electronic Flight Information systems 

ELT Emergency Locator Transmitter 

EMI Electromagnetic Interference 

FAA Federal Aviation Administration 

FAASTEAM Federal Aviation Administration Safety Team 

FAR Federal Aviation Regulation 

FDR Flight Data Recorder 

FSB Flight Standardization Board 

GA General Aviation 

GAMA General Aviation Manufacturers Association 

GNSS Global Navigation Satellite System 

87 
GPS Global Positioning System 

HF High Frequency 

HIRF High Intensity Radio Frequency 

HIS Horizontal Situation Indicator 

ICA Instructions for Continued Airworthiness 

ICAO International Civil Aviation Organization 

IPC Illustrated Parts Catalog 

KCAS Knots Calibrated Airspeed 

LOV Limited of Validity 

LSA Light Sport Aircraft 

MAC Mean aerodynamic chord 

Md Dive speed in Mach 

MSAD Monitor Safety Analyze Data 

MTOW Maximum Take-off Weight 

NBAA National Business Aviation Association 

NTSB National Transportation Safety Board 

OEI One Engine Inoperative 

OEM Original Equipment Manufacturers 

PIC Pilot in Command 

QMS Quality Management System 

R & D Research and Development 

RLOC Runway Loss of Control 

SAD Small Airplane Directorate 

SAFO Safety Alert for Operations 

SB Service Bulletin 

SDR Service Difficulty Reporting 

SMS Safety Management System 

STC Supplemental Type Certificate 

TALPA Takeoff and Landing Performance Assessment 

U.S. United States 

VA Maneuvering speed 

VD Dive speed in knots 

VHF Visual Metrological Conditions 

VO Normal operating speed 

VOR VHF (Very High Frequency) Omni-directional Radio-range 

VHF Omni-Directional Radio-Range/Distance-Measuring 

VOR/DME Equipment 

VREF Reference Landing Speed 

WAAS Wide Area Augmentation System 

WAT Weight/Altitude/Temperature 

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OK-09-3468