Ask the DAR

Know your limitations, continued.


Last month we discussed the first two paragraphs of the operating limitations for an Experimental/Amateur-Built aircraft. Let’s see what else is interesting.

(3) This aircraft must be operated for at least __ hours in the assigned geographic area.

Well, that sounds simple enough. What number is in this space on your limitations? Twenty-five? Forty? More? The FAA requires a minimum of 25 hours of flight testing for an aircraft with a type-certificated engine and prop combination. A minimum of 40 hours is required when a non-type-certificated engine, propeller or engine/prop combination is installed. Inspectors may assign a longer flight-test period when it is necessary to determine compliance with 91.319(b). Note that the combination of engine and prop must be type-certificated. Also of importance is that any modification of the engine such as an aftermarket ignition system and/or fuel-injection system will likely void the type-certificate compliance and force the builder into the 40-hour Phase I.

(4) All test flights, at a minimum, must be conducted under day VFR only. Guidance concerning the scope and detail of test flights can be found in AC 90-89. Following satisfactory completion of the required number of flight hours in the flight test area, the pilot must certify in the records that the aircraft has been shown to comply with 91.319(b). Compliance with 91.319(b) must be recorded in the aircraft records with the following, or a similarly worded statement. "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 Vso__, Vx__, and Vy__, and the weight__ and CG location__ at which they were obtained.

This paragraph tells us that Phase I flight testing must be done in daytime VFR conditions. It refers to FAA Advisory Circular 90-89 for testing guidance. It also tells how to sign off the flight-testing phase in the logbook, including certain flight parameters. This assures that we don’t fly for 40 hours with no testing whatsoever. It also establishes the gross weight of the aircraft.

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(5) Except for takeoffs and landings, this aircraft may not be operated over densely populated areas or in congested airways.

This is issued in accordance with paragraphs 135b(1) and (2) of order 8130.2, which gives the inspector guidance for proper airport selection. If the proposed airport is completely surrounded by densely populated area and lacks any acceptable approach/departure corridor, the FAA must deny the airworthiness certificate and process the denial with the FAA in Oklahoma. The aircraft applicant must be advised to relocate the aircraft by other means to a suitable airport.

(6) This aircraft is prohibited from operating in congested airways or over densely populated areas unless directed by air traffic control, or unless sufficient altitude is maintained to effect a safe emergency landing in the event of a power unit failure, without hazard to persons or property on the ground.

This limitation applies after the aircraft has satisfactorily completed all requirements for Phase I flight testing, has the proper endorsement in the logbook and maintenance records, and is operating in Phase II. It "puts the monkey on your back" in that it is your responsibility to assure that you can always make a safe emergency landing if needed without danger to anyone else.

Please send your questions for DAR Asberry to with Ask the DAR in the subject line.

Mel Asberry is an experienced Designated Airworthiness Representative specializing in Experimental/Amateur-Built aircraft. He and his wife, Ann, have built seven amateur-built airplanes including two ultralight types, a Moni Motorglider, a Dragonfly Mk2, two RV-6s and a Zenair CH 601HDS. They are currently building a scratch-built biplane.


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