AC 90-89C

U.S. Department of Transportation Federal Aviation Administration Advisory Circular Subject: Amateur-Built Aircraft and Ultralight Flight Testing Handbook Date: 2/14/23 AC No: 90-89C Initiated by: AFS-300 Change:

ii This advisory circular (AC) provides suggestions and safety-related recommendations primarily to assist amateur-built aircraft and ultralight vehicle builders in developing individualized flight test plans. It also provides guidance for Experimental Light-Sport Aircraft (ELSA) flight testing after modifications to the aircraft. It provides recommendations and suggestions you can combine with other sources on test flying, such as the aircraft plan/kit manufacturer’s flight testing instructions and other flight testing data. This will help you develop a detailed flight test plan, tailored for your aircraft or ultralight vehicle and resources.

This AC attempts to make you aware that test flying an aircraft or ultralight vehicle is a critical undertaking, which you should approach with thorough planning, skill, and common sense. The flight test plan is the heart of all professional flight testing. The plan should account for every hour spent in the flight test phase and you should adhere to it with the same respect for the unknown that all successful test pilots share. The time allotted for each phase of a personalized flight test plan may vary, and each phase may have more events or checks than suggested in this AC, but your goals, should be the same. You should add flight test operational and performance data to the Aircraft Operating Handbook (AOH) so you can reference the data prior to each flight.

This AC also provides criteria for the use of an optional, operationally centric or task-based experimental aircraft flight test plan. This task-based option provides at least the same level of safety and reliability that the existing hourly minimum 25 or 40-hour flight test provides, but with the advantages of having operational completion criteria, a plan to record data for the creation of an AOH, and a flight test report documenting the flight testing results.

The contents of this document do not have the force and effect of law and are not meant to bind the public in any way, and the document is intended only to provide information to the public regarding existing requirements under the law or agency policies. This AC is not mandatory and does not constitute a regulation. This AC describes an acceptable means, but not the only means, to develop flight test plans. However, if you use the means described in the AC, you should follow it in all respects. This AC applies to amateur-built aircraft and ultralight vehicle builders, and individuals involved in flight testing those aircraft and ultralight vehicles.

Mandatory terms used in this AC such as “must” are used only in the sense of ensuring applicability of these particular methods of compliance when the acceptable means of compliance described herein are used.

C aitlin Locke Acting Deputy Executive Director, Flight Standards Service

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CONTENTS Paragraph Page

Chapter 1. Administrative Information1-1

1.1 Purpose of This Advisory Circular (AC)1-1

1.2 Audience1-1

1.3 W here You Can Find This AC1-1

1.4 W hat This AC Cancels1-1

1.5 B ackground1-1

1.6 D efinition s1-2

1.7 R equest for Information1-2

1.8 A C Feedback Form1-3

Chapter 2. Pr eparation2-1

Section 1. Ho mework2-1

2.1 Objective2-1

Section 2. A irport Selection2-12

2.2 Objective2-12

Section 3. E mergency Plans and Equipment2-14

2.3 Objective2-14

Section 4. T est Pilot2-17

2.4 Objective2-17

2.5 General2-17

2.6 Test Pilot Requirements2-17

Section 5. Med ical Facts for Pilots2-19

2.7 Objective2-19

Section 6. T ransporting the Aircraft to the Airport2-21

2.8 Objective2-21

Section 7. A ssembly and Airworthiness Inspection2-22

2.9 Objective2-22

2.10 General2-22

2.11 Fitness Inspection—Airframe2-22

2.12 Field Check2-24

Section 8. W eight and Balance2-27

2.13 Objective2-27

2.14 Determining Empty Weight CG2-29

2.15 Determining Takeoff Weight CG2-30

2.16 Additional Equipment Testing2-31

Section 9. P aperwork2-32

2.17 Objective2-32

Section 10. P owerplant Tests2-34

2.18 Objective2-34

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Section 11. Additional Engine Tests2-39

2.19 Objective2-39

Section 12. P ropeller Inspection2-43

2.20 Objective2-43

2.21 Recommendations for All Propellers2-44

2.22 Propeller Tracking Check2-45

2.23 Metal Propeller Inspection2-45

2.24 Wood Propeller Inspection2-47

2.25 Composite Propeller Inspection2-48

Chapter 3. Taxi Tests3-1

Section 1. Lo w-Speed Taxi Tests3-1

3.1 Objective3-1

3.2 Taxi Tests3-1

Section 2. High-S peed Taxi Tests3-2

3.3 Objective3-2

Chapter 4. The Fir st Flight4-1

Section 1. G eneral4-1

4.1 Objective4-1

4.2 General4-1

4.3 Recommendations4-1

4.4 First Flight Inspection4-2

Section 2. T he Role of the Chase Plane4-3

4.5 Objective4-3

4.6 General4-3

Section 3. E mergency Procedures4-4

4.7 Objective4-4

4.8 General4-4

Section 4. F irst Flight4-5

4.9 Objective4-5

Section 5. F irst Flight Procedures4-7

4.10 Objective4-7

Chapter 5. The Firs t 10 Hours5-1

Section 1. T he Second Flight5-1

5.1 Objective5-1

Section 2. Th e Third Flight5-1

5.2 Objective5-1

5.3 General5-1

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Section 3. Hours 4 Through 105-2

5.4 Objective5-2

5.5 General5-2

5.6 Gear Retraction5-2

5.7 Climbs and Descents5-3

5.8 Airspeed In-Flight Accuracy Check5-4

Chapter 6. Expanding the Envelope6-1

S

ection 1. Gen eral6-1

6.1 Objective6-1

Section 2. Hour s 11 Through 206-1

6.2 Objective6-1

6.3 Stalls6-3

Section 3. Hour s 21 Through 35: Stability and Control Checks6-6

6.4 Objective6-6

6.5 General6-6

6.6 Definitions6-7

Section 4. A Wo rd or Two About Flutter6-11

6.7 Objective6-11

6.8 Description6-11

Section 5. Spi ns6-13

6.9 Objective6-13

6.10 Caution6-13

6.11 Planning the Flight6-14

Section 6. Accel erated Stalls6-1

6.12 Objective6-1

Chapter 7. Putti ng It All Together: 36 Hours to —————?7-1

Section 1. Maxi mum Gross Weight Tests7-1

7.1 Objective7-1

Section 2. S ervice Ceiling Tests7-2

7.2 Objective7-2

Section 3. N avigation, Fuel Consumption, and Night Flying7-3

7.3 Objective7-3

Chapter 8. Thoughts on Testing Canard Type Amateur-B uilt Aircraft8-1

Section 1. Canards8-1

8.1 Objective8-1

Section 2. Flight Test Considerations.8-3

8.2 General8-3

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Chapter 9. Ultralight Airframe Inspection9-1

Section 1. Di fferences9-1

9.1 Objective9-1

9.2 Definition9-1

Section 2. The Test Pilot9-2

9.3 General9-2

Section 3. Pre flight Airframe Inspection9-3

9.4 General9-3

9.5 Checklist9-3

Chapter 10. Ultra light Engine/Fuel System Inspection10-1

Section 1. Engi ne Inspection10-1

10.1 Objective10-1

Section 2. Fue l Systems10-3

10.2 General10-3

Chapter 11. Ultra light Test Flying Recommendations11-1

Section 1. Th ree Recommendations11-1

11.1 Objective11-1

11.2 Recommendations11-1

Section 2. Airp ort Selection11-2

11.3 Objective11-2

Section 3. Ta xiing11-2

11.4 General11-2

Section 4. Firs t Flight Differences11-2

11.5 Use of Power11-2

11.6 Control Feel11-3

11.7 Stalls11-3

11.8 Steep Turns11-3

Section 5. Emer gency Procedures11-3

11.9 Engine Failures11-3

11.10 Loss of Control11-3

11.11 Catastrophic Failure11-4

Appendix A. Sa mple Checklist for a Condition InspectionA-1

Appendix B. So urces for Accident/Incident InformationB-1

Appendix C. Ad ditional References on Flight TestingC-1

vii List of Figures Figure 2-1. Cumulative Portion of Phase I E- AB Accidents With Less Than

35 Airframe Hours2-2

Figure 2-2. S ample Flight Test Card2-7

Figure 2-3. S ample Maintenance Record Entry2-9

Figure 2-4. R unway Length Chart2-13

Figure 2-5. E mpty Weight CG2-29

Figure 2-6. T akeoff CG2-30

Figure 2-7. A dditional Equipment Added2-31

Figure 2-8. 100 H p Fuel Flow Rate Chart2-42

Figure 2-9. P ropeller Tracking2-45

Figure 6-1. C limb Airspeed and Altitude Graph6-4

Figure 6-2. B est Rate of Climb Speed Graph6-5

Figure 6-3. S tatic Stability6-7

Figure 6-4. T ime6-8

1-1 CHAPTER 1. ADMINISTRATIVE INFORMATION

1.1 Purpose of This Advisory Circular (AC). This AC provides suggestions and safety-related recommendations primarily to assist amateur-built aircraft and ultralight vehicle builders in developing individualized flight test plans. It also provides guidance for Experimental Light-Sport Aircraft (ELSA) flight testing after modifications to the aircraft. It provides recommendations and suggestions you can combine with other sources on test flying, such as the aircraft plan/kit manufacturer’s flight testing instructions and other flight testing data. This will help you develop a detailed flight test plan, tailored for your aircraft or ultralight vehicle and resources. The contents of this document do not have the force and effect of law and are not meant to bind the public in any way, and the document is intended only to provide information to the public regarding existing requirements under the law or agency policies.

1.2 Audience. This AC applies to amateur-built aircraft and ultralight vehicle builders, owners, and operators developing individualized aircraft flight test plans. It also provides guidance to owners and operators of ELSAs performing flight testing after making modifications to the aircraft.

1.3 Where You Can Find This AC. You can find this AC on the Federal Aviation Administration’s (FAA) website at https://www.faa.gov/regulations_policies/advisory_cir culars and the Dynamic Regulatory System (DRS) at https://drs.faa.gov.

1.4 What This AC Cancels. AC 90-89B, Amateur-Built Aircraft and Ultralight Flight Testing Handbook, dated April 27, 2015, is canceled.

1.5 Background. We, the FAA, along with the Experimental Aircraft Association (EAA), and the United States Ultralight Association (USUA), are concerned and committed to improving the safety record of amateur-built aircraft and ultralight vehicles. Past FAA Administrator, T. Allen McArtor, and past EAA President, Paul H. Poberezny, signed a Memorandum of Agreement (MOA) on August 1, 1988, addressing the need for educational and safety programs to help amateur builders test fly their aircraft. This AC lists guidelines for flight testing amateur-built aircraft, using suggestions in the MOA.

We have revised this AC to include flight testing recommendations for canard type aircraft and ultralight vehicles as part of our continuing efforts to improve the safety record of all types of general aviation aircraft. In 2012 the first Loss of Control Working Group (LOCWG) investigated the causal factors behind fatal accidents arising from a loss of control during the approach and landing phases of flight. Loss of control is the leading cause of fatal accidents in general aviation. From a study of a random sample of 90 fatal accidents fitting this profile over the past decade the Working Group recommended 27 safety enhancements (SE), 23 of which were approved. SE-23 is implemented into this AC. As a result of SE-23, there are two major additions to this AC.

• The Type Club Coalition (TCC) coordinated by the EAA developed a best practices guide for when flight tests should be done following a modification to an amateur-built aircraft.

• Testing for center-of-gravity (CG) limits, including lateral, was added to this AC.

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1.5.1 Two informational FAA updates were added.

• Light-sport aircraft (LSA) flight testing after a modification is mentioned where appropriate within this AC.

• All references to two seat ultralights have been removed.

1.6 Definitions. The following terms are defined for use in this AC.

1.6.1 Aircraft. In this AC, refers to an amateur-built aircraft, special light-sport category aircraft (SLSA), or ELSA.

1.6.2 A mateur -Built Aircraft. An aircraft issued an Experimental Certificate under the provisions of Title 14 of the Code of Federal Regulations (14 CFR) part 21, § 21.191(g).

1.6.3 Experimental Light-Sport Aircraft (ELSA). An aircraft issued an Experimental Certificate under the provisions of § 21.191(i).

1.6.4 L ight- Sport Aircraft. An aircraft that meets the parameters of the definition of light-sport aircraft specified in 14 CFR part 1, § 1.1.

1.6.5 Special Light-Sport Aircraft (SLSA). An aircraft issued a Special Airworthiness Certificate in the light-sport category under the provisions of § 21.190.

1.6.6 Ultralight Vehicle. A vehicle that meets the requirements of 14 CFR part 103, § 103.1.

1.7 Request for Information. We have designed this AC as a reference document to help prepare a flight test plan for an amateur-built aircraft or ultralight vehicle. The suggestions and recommendations in Chapters 2 through 7 are for conventionally designed aircraft with an air-cooled, 4-cycle, reciprocating engine developing less than 200 horsepower (hp) and with a fixed-pitch propeller.

• Chapter 8 deals with flight testing recommendations for canard aircraft.

• Chapters 9 through 11 address flight testing considerations for ultralight vehicles under part 103.

1.7.1 Because of many existing amateur-built aircraft/ultralight vehicle designs and new designs being introduced each year, we encourage public participation in updating this document. Send comments, suggestions, or information about this AC to the following address:

U.S. Department of Transportation Federal Aviation Administration Flight Standards Service General Aviation Group (AFS-340) 5th Floor, 950 L’Enfant Plaza, S.W.

Washington, DC 20024

1-3 Note: After a review, appropriate comments, suggestions, and information may be included in the next revision of this AC.

1.8 AC Feedback Form. For your convenience, the AC Feedback Form is the last page of this AC. Note any deficiencies found, clarifications needed, or suggested improvements regarding the contents of this AC on the Feedback Form.

2-1 CHAPTER 2. PREPARATION S ECTION 1. HOMEWORK

2.1 Objective. A planned approach to flight testing.

2.1.1 Phased Flight Testing. After the Special Airworthiness Certificate and operating limitations have been issued, the builder of an amateur-built aircraft shows compliance with Title 14 of the Code of Federal Regulations (14 CFR) part 91, § 91.319(b), that the aircraft is controllable throughout its normal range of speeds and throughout all the maneuvers to be executed and that the aircraft has no hazardous operating characteristics or design features. This is accomplished through a “phased” flight test approach (Phase I and Phase II). In Phase I operations, the aircraft undergoes flight testing to ensure the proper operation and reliability of aircraft systems and to develop the aircraft’s flight envelope. After the completion of Phase I, the aircraft enters Phase II where it will normally reside for the remainder of its operational life, unless modifications are made to the aircraft, in which case it re-enters Phase I testing. The aircraft then re-enters Phase II upon completion of that further testing. This cycle continues for the life of the aircraft.

2.1.1.1 The data gathered during flight testing should be used to develop an accurate and complete Aircraft Operating Handbook (AOH) and to establish emergency procedures. Additional guidance on the development of the AOH can be found in Federal Aviation Administration (FAA) Advisory Circular (AC) 60-6, Airplane Flight Manuals (AFM), Approved Manual Materials, Markings, and Placards – Airplanes, and AC 25.1581-1, Airplane Flight Manual.

2-2 Note: Industry-developed task-based test manuals may assist aircraft builders through the testing process, such as the Experimental Aircraft Association (EAA) Flight Test Manual referred to in Appendix C, Additional References on Flight Testing.

2.1.2 The First Few Hours Pose t he Highest Risk. In 2011, the National Transportation Safety Board (NTSB) issued a report on the safety trends in amateur-built aircraft, noting that the principal causes of accidents lie in pilot loss of control or engine failures and, interestingly, not from builder quality of construction issues. Furthermore, FAA data shows the highest rate of accidents occurs in the first 8 hours of Phase I flight testing and then decreases dramatically. This highlights the importance of a detailed, comprehensive flight test plan of adequate or appropriate length.

Figure 2-1. Cumulative Portion of Phase I E-AB Accidents With Less Than 35 Airframe Hours

2.1.3 Develop a Flight Test Plan. Y our most important task is to develop a comprehensive flight test plan. You should tailor this plan to define the aircraft’s specific level of performance, so it’s important that the entire flight test plan be developed and completed before the aircraft’s first flight.

Note: As part of the comprehensive flight test plan, the test pilot should read and c omprehend this entire AC before proceeding in accomplishing any suggested task.

2.1.4 Objective of a Flight Test Plan. T he objective of a flight test plan is to determine the aircraft’s controllability throughout all the maneuvers and to detect any hazardous