Jon Thornburgh

Light Aircraft Manufacturers Association - Exemption/Rulemaking http://www.regulations.gov/fdmspublic/component/main? main=DocketDetail&d=FAA-2008-0737 Docket No. FAA-2008-0737 Document ID: FAA-2008-0737-0008 Dear Sir: I strongly support the LAMA petition to allow manually feathering propellers on light-sport aircraft motorgliders. I am a flight instructor and Designated Pilot Examiner for light-sport aircraft gliders. I use an Urban Air Lambada for instruction. The Lambada was originally equipped with a manual feathering system, which has been disabled in accordance from an Urban Air directive in order to conform to the criteria applicable to motorgliders under the definition of "Light-Sport Aircraft" in 14 CFR 1.1. Prior to the disabling of the manual feathering system my students had absolutely no difficulty whatsoever in manually feathering the propeller. The feather can be manually feathered by pulling a lever immediately after the engine is shutdown. The propeller can be unfeathered immediately after engine startup by simply returning the feathering lever back to the "unfeathered" position. An interlock prevents the engine from running if the propeller is in the feathered position. Since the feathering mechanism has been disabled the Lambada must now glide with the propeller in the unfeathered flat pitch position. The rate of descent in calm air has increased from 230 feet per minute to 450 feet per minute. This is a large increase in sink, and significantly degrades the aircraft's glide ratio. If the engine did not restart after losing lift while soaring the pilot would have to glide, possibly to an off-field landing, with the propeller in the fixed-pitch position. This could be a considerable detriment to safety. In addition, if the engine quit on takeoff, it would be more difficult to make a 180-degree turn to landing with the propeller in fixed pitch. In addition to the Lambada I have flown the Grob and Taifun motorgliders. Neither of these gliders had an automatic feathering system. 14 CFR 1.1 does not define "autofeathering." I interpreted the word to mean that the propeller is automatically capable of being feathered immediately after the engine is shutdown. In other words, the pilot need not do anything before pulling the feathering lever, such as toggling the starter to nudge the propeller into a specific horizontal or vertical direction before feathering it. Under Part 1.1, "Light-sport aircraft," item (8) states, "A fixed or autofeathering propeller system if a powered glider." After extensive inquiry I have been unable to determine how the "autofeathering" requirement was ever considered by the ASTM consensus committee. The "autofeathering" option a very strange criterion for motorgliders and so is the option of a "fixed" propeller. Neither option is a traditional motorglider configuration. A hydraulic, spring-loaded, or electric autofeathering system is far more complex and requires more maintenance than a simple manual feathering system. It does not enhance safety because the autofeathering system could malfunction and fail to feather when the engine is shutdown. In addition, the pilot would be unable to unfeather the propeller unless the engine is running. This would preclude him from the option of increasing drag to accomplish an off-field landing if he were approaching the landing spot at excessive altitude. Also, an autofeatering system would presumably feather the propeller every time the engine was shutdown after landing. The pilot might then be unable to start the engine for the next flight if the automatic unfeathering interlocks malfunctioned. A malfunctioning autofeathering/unfeathering system would also prevent the pilot from having the option to unfeather the propeller and start the engine by high- speed wind milling. The definition of "light-sport aircraft" precludes a sport pilot from operating a single engine land airplane that has an adjustable propeller or retractable gear. This requirement is presumably to decrease the workload of a sport pilot who receives his certificate with potentially only 20 hours of flight time (Part 61.313.) However, there is a retractable gear exception for light-sport seaplane pilots and glider pilots. There is also a different Vne requirement for glider pilots than airplane pilots. Seaplane pilots can fly an aircraft with a higher gross weight than land pilots. It is apparent, therefore, that the FAA recognizes the need for flexibility for sport pilots who fly different types of light-sport aircraft. In the spirit of maintaining this common-sense flexibility, I urge the FAA to amend Part 1.1, "Light-sport aircraft," paragraph (8) to read, "A fixed, autofeathering, or manual feathering propeller system if a powered glider." Sincerely, Jon Thornburgh FAA Flight Instructor and Sport Pilot Examiner Jon@JonThornburgh.com