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
2-3 operating characteristics or design features. You should use this data to develop a flight manual that specifies the aircraft’s performance and defines its operating envelope.
Additionally, the plan should reference the use of checklists to assure that all relevant steps and elements are covered.
2.1.5 T ime Required for Flight Testing Amateur- Built Aircraft. Your original issued experimental certificate should be limited to operation within an assigned flight test area for a minimum of 25 hours when a type certificated (TC) engine/propeller combination is installed. A minimum of 40 hours is required when a non-TC’d engine, propeller, or engine/propeller combination is installed. Furthermore, if the TC’d engine, propeller, or engine/propeller combination installed has been altered in a way that differs from an approved type design in a Type Certificate Data Sheet (TCDS), a minimum of 40 hours will be required.
2.1.6 Task-B ased Flight Test Plan. Comprehensive guidance on flight testing objectives has historically been lacking for amateur-built aircraft, with the only well-known requirement simply being the 25- or 40-hour flight testing requirement found in the operating limitations issued with the aircraft’s experimental certificate. This can lead to gaps in the performance and reliability testing of an aircraft, inadequate documentation of flight characteristics, and also the creation of a hazard for inexperienced pilots attempting to “just fly off” the required hours. Many times, AOHs are not created from the flight tests, resulting in little or no documented aircraft data for operators other than the original builder’s experience with flight testing.
2.1.6.1 U se of a Task-Based Flight Test Plan. The FAA has been shifting to more performance-based rules and policy, which has led to allowances for performance-based criteria in experimental aircraft flight testing. The minimum 25- or 40-hour flight test period has long been considered necessary to ensure that the aircraft and its systems are properly and thoroughly tested, found to be reliable, that the aircraft does not exhibit any undesirable flight characteristics or system flaws, and that it is tested throughout its intended flight regime. This AC creates the ability for builders to utilize a comprehensive, individualized task-based flight test plan to meet the objectives of the flight test, but according to certain completion criteria and possibly less than the typical 25 or 40 hours, depending on the complexity of the aircraft.
2.1.6.2 Expectations. The ability to use the task-based flight test plan as provided in this AC is enabled via the issuance of an operating limitation that allows its use, in lieu of the minimum 25- or 40-hour flight test periods contained in previously issued operating limitations. The FAA will permit the use of a task-based flight test plan based on your use of this AC and adherence to the objectives of the task-based flight test plan, providing the specified logbook entry, and maintaining the AOH on board the aircraft following flight testing.
No formal FAA acceptance process is necessary for the builder to utilize a task-based flight test plan. Issuance of operating limitations with the traditional minimum hourly flight test periods specified for a pilot to flight test
2-4 their aircraft as the sole occupant of the aircraft during Phase I remains for those who choose to do so in accordance with those operating limitations.
There is no requirement to create, submit, or use a formal flight test plan.
However, the FAA strongly encourages amateur builders to develop and utilize an individualized, comprehensive, requirements-based, operationcentric (task-based) flight test plan appropriate for the complexity of the aircraft with specific tasks and objectives. The FAA also encourages builders to utilize the Additional Pilot Program (APP) described in AC 90-116, Additional Pilot Program for Phase I Flight Test. A task-based flight test plan should contain the minimum elements described in this AC, provide aircraft systems reliability and flight envelope testing to ensure that the aircraft is controllable throughout its normal range of speeds and throughout all the maneuvers to be executed, and ensure that the aircraft has no hazardous operating characteristics or design features. The FAA expects that builders follow their flight test plan, including those who utilize a task-based flight test plan.
2.1.7 Task-B ased Flight Testing Criteria. There are three overall considerations for a successful task-based flight test plan:
• A ircraft preparation;
• Flight testing; and
• Development of an aircraft-specific AOH.
2.1.7.1 Documentation and recordkeeping are critical to each of these elements, starting with the builder’s log, continuing with ongoing aircraft maintenance records, and then recording any modifications made to the aircraft during its life. The goals of operational flight testing are to develop the performance and qualitative handling data that will be compiled in the AOH, ensure aircraft systems reliability, determine the aircraft’s flight envelope to ensure that the aircraft is controllable throughout its normal range of speeds and maneuvers, and ensure that the aircraft has no hazardous operating characteristics or design features.
2.1.8 M inimum Flight Test Plan Elements . The following elements, at a minimum, should be included in a flight test plan:
1. A complete, detailed flight test plan that will:
a. Ensure the aircraft will be adequately tested and determined to be safe to fly within the aircraft’s flight envelope, and
b. Produce flight test data to develop an accurate and complete AOH and to establish emergency procedures.
2. Aircraft fuel system functional test procedures, fuel flow, and unusable fuel tests.
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3.
A fuel system functional test report. (It is recommended that the fuel system functional test report be included in the AOH. For more information, see Paragraph
2.12.3 , Fuel System.)
4. Provisions for the use of electronic data recordings from electronic flight displays, engine instruments, or other recording devices in development of performance data and AOH information, if the aircraft is equipped with these types of instrumentation.
5. The method that will be used for recordkeeping.
6. The description of the cockpit layout.
7. Weight and Balance (W&B) information and calculations.
8. The aircraft inspection checklist.
9. Engine run and taxi tests.
10. The following flight tests:
a. First flight.
b. Gear and flap operation.
c. Rough pitot-static check.
d. Wings level stalls.
e. Accelerated stalls.
Note: In cases where stalling the specific aircraft type is not recommended, investigating approaches to stall and stall warning in the cited configurations can be substituted if appropriate.
f. Determine best angle of climb (VX) and best rate of climb (VY) speed.
g. Best glide speed.
h. Range and endurance.
i. Takeoff performance.
j. Longitudinal control.
k. Trim effectiveness.
l. Static longitudinal stability.
m. Static directional stability.
n. Static lateral stability.
o. Longitudinal dynamic stability.
p. Runaway electric pitch trim, if applicable.
q. Landing performance.
11. Flight test cards. The task-based flight test plan should contain “flight test cards” that can be used to document results of flight test procedures and provide for the
2-6 collection and recording of flight test data. A sample flight test card is shown in Figure 2-2. Flight test cards should contain at least the following:
a. Date.
b. Aircraft N-Number or serial number.
c. Location (Airport ID) for takeoff and landing.
d. Start time, takeoff time, landing time, and shutdown time.
e. Name of the Builder/Owner Pilot (BP) and Additional Qualified Pilot (QP), if applicable.
f. Flap setting for takeoff and landing, if applicable.
g. Name of observer, if applicable.
h. Takeoff weight and center of gravity (CG).
i. Takeoff fuel quantity.
j. Planned duration of flight.
k. Planned landing fuel quantity.
l. Altimeter setting.
m. Objectives for each flight test element.
n. Risk level or risk designation for each flight test element.
o. Specific procedures for each flight test element:
• Power settings.
• Flap settings, if applicable.
• Landing gear position.
p. Emergency preparedness measures necessary and specific to each element.
q. Acceptable or satisfactory completion criteria or outcomes for each flight test element.
r. Comments and results for each flight test element.
Figure 2-2. Sample Flight Test Card Test Card 1-Engine Run & Taxi Test Risk Designation: LOW Date N Number: Start time: Takeoff Time:
Serial No:
Pilot: Observer: Shutdown Time: Landing Time:
Takeoff Weight: CG: Block Time: Flight Time:
Airport: T/O Trim Setting Takeoff Flap Landing Flap Setting: Setting:
Altimeter Setting: Takeoff Fuel: Landing Fuel:
Procedures Cowl removed Fuel: 20-30 minutes of fuel Observer with fire extinguisher Possible Emergencies: engine start malfunction; fire; emergency shutdown Conduct multiple runs if necessary
2. Engine Stabilized: Record engin Engine Stabilized: Record engine instrument readings when stabilized
3. Engine to Idle speed: Record idle RPM (adjust if necessary)
4. Mixture to Idle: At idle reduce mixture and record rise in RPM (minimum
50)
5. Taxi: straight, left tums, right tums, and note tracking, under-steer/oversteer, and turn radius with and without brake application.
6. Brakes: Wear-in according to the manufacturer's recommendation Shutdown: Normal method (usually retard mixture)
8. Shutdown: Altemate method (usually turn off magnetos)
9. Shutdown: Emergency method (usually select fuel valve to OFF) Stabilized Engine Readings Cy 1 Cyl 2 • Су з Cy 4 Cy 5 Cyl 6 Comments CHT EGT Oil Press Volts Oil Temp Amps Fuel Press Fuel Flow Engine Idle Comments Idle RPM dle Mixture Record RPM rise Taxi Tests Satisfactory? Comments Taxi straight Taxi tums Taxi w/o brakes Brake Wear In Satisfactory? Comments Brake wear-in Shutdown Satisfactory? Comments Nomal (mixture) Note Time Altemate (mags Note Time Emergency (fuel) Note Time Notes 2-7
2-8 OPERATING LIMITATIONS.
Process. Builders may utilize a task-based flight test plan without approval or submission to the Flight Standards District Office (FSDO) or Manufacturing Inspection District Office (MIDO).
FAA acceptance will be conveyed by issuance of the Experimental Certificate and corresponding operating limitations. Any change to the hourly requirements for flight testing will also be reflected in the aircraft’s operating limitations.
Required Operating Limitation. In order to utilize a task-based flight test plan, the operating limitations for the aircraft need to reference this AC. The limitation that authorizes the use of the task-based flight test plan is worded as, or worded similarly to, the following:
All flights must be in this geographical area: [The area must be described by radius, coordinates, navigational aids, and/or landmarks. The size of the area and airports must be that required to safely conduct the anticipated maneuvers and tests.] Unless operating in accordance with the task-based flight test program described in Advisory Circular (AC) 90-89, Amateur-Built Aircraft and Ultralight Flight Testing Handbook, chapter 2, section 1, during Phase I flight testing, this aircraft must be operated for at least _____ hours with at least_____ takeoffs and landings.
2.1.9 Failure to Meet Flight Testing Criteria. If at any time during the flight testing of the aircraft, the aircraft, its systems, or operational elements are unable to meet the completion criteria originally prescribed in the task-based flight test plan, make repairs as needed and repeat the procedure until completion criteria is met or test for the full 25 or 40 hours, as appropriate, according to the applicable operating limitations. Operating limitations generally will not be reissued. The desired outcome is to ensure 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.
2.1.10 E xit Criteria —Aircraft Maintenance Record Documentation of Completion of Requirements-Based Phase I Flight Test. The builder should make a maintenance record entry attesting that the flight test has been completed, and the data has been recorded.
This ensures that the flight test was completed based on the prepared plan and also allows retention of the flight test data in the AOH for a particular aircraft.
2-9 Figure 2-3. Sample Maintenance Record Entry The logbook entry documenting completion of the flight test will correspond to the following:
Completion of task-based flight test:
“I certify that all requirements of the task-based flight test plan have been completed in accordance with AC 90-89 and the aircraft is controllable throughout its normal range of speeds and throughout all maneuvers to be executed, has no hazardous operating characteristics or design features, and is safe for operation. An AOH has been developed and placed in the aircraft. The following aircraft operating data has been demonstrated during the flight testing:
speeds VS0 ______, VX ______, and VY ______, and the weight ______ and CG location ______ at which they were obtained.”
Printed Name Signature Hours-based flight test completion only:
“I certify that the prescribed flight test hours have been completed and the aircraft is controllable throughout its normal range of speeds and throughout all maneuvers to be executed, has no hazardous operating characteristics or design features, and is safe for operation. The following aircraft operating data has been demonstrated during the flight testing: speeds VS0 ______, VX ______, and VY ______, and the weight ______ and CG location ______ at which they were obtained.”
Printed Name Signature
2.1.11 Time Required for Flight Testing Experimental Light-Sport Aircraft (ELSA). If you own an ELSA certificated under 14 CFR part 21, § 21.191(i)(2), and it has not been modified, conduct a test flight as per the operations manual in an assigned flight test area for a minimum of 5 hours. This applies for all categories and classes of light-sport aircraft (LSA) to determine aircraft controllability throughout its design limits.
2.1.12 B est Practices for Flight Testing After Modifying an Experimental Amateur- Built (E-AB) Aircraft. Before considering any modification to an aircraft previously issued an experimental certificate for the purpose of operating amateur-built aircraft, there are two things you need to consider. First is the level of modification; the other is the corresponding flight testing required for the modification. When considering the level of modification, you should first check the E-AB operating limitations. They will detail what, if any, reporting requirements there are for a given modification. This is especially important when the E-AB modification approaches the same level of a major change to the type design of a type certificated aircraft as defined in § 21.93. Usually the owner of the E-AB aircraft is required by the aircraft operating limitations to notify the responsible