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ASN Wikibase Occurrence # 45512
Last updated: 30 November 2021
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Type:Silhouette image of generic RAF2 model; specific model in this crash may look slightly different
RAF 2000
Owner/operator:Raymond D. Denzer
Registration: N435PR
MSN: H2-00-11-455
Fatalities:Fatalities: 1 / Occupants: 1
Other fatalities:0
Aircraft damage: Substantial
Location:PALMER, AK -   United States of America
Phase: Take off
Departure airport:Palmer, AK (PAAQ)
Destination airport:
Investigating agency: NTSB
The private airplane pilot was conducting touch and go landings in a two-seat, wheel-equipped experimental/homebuilt gyroplane. During the takeoff roll, the gyroplane lifted off abruptly, and the main rotor blades struck the runway surface near the location where the gyroplane lifted off. The gyroplane then climbed steeply to an altitude of less than 100 feet above the ground, and went through one or more longitudinal axis pitch oscillations. The main rotor was observed to slow down and strike the tail-mounted rudder. The gyroplane then descended to the runway in a steep nose-down attitude. Examination of the wreckage revealed no evidence of any preexisting mechanical anomalies. The gyroplane kit was purchased by the pilot in April, 2000. It was assembled by the pilot/owner in Alaska, and transported to Alabama in January, 2002. The pilot began receiving flight training in the gyroplane on January 16, 2002, and concluded training on February 2, 2002. On February 3, 2002, the pilot completed an application for a private pilot, rotorcraft gyroplane rating, and the application was endorsed by the pilot's flight instructor. According to the pilot's flight instructor, the pilot planned to travel from Alabama to Alaska, and planned to complete the practical (flight) test portion of the gyroplane rating either enroute or in Alaska. Application for an additional gyroplane rating requires that the applicant accumulate at least 40 hours of flight time that includes at least 20 hours of flight training, and 10 hours of solo flight, and complete a practical test. No additional written test is required. On the application, the pilot listed 42.4 hours in a gyroplane, 32.2 hours of instruction, and 10.2 hours of solo flight. The pilot did not complete the practical test for a rotorcraft gyroplane rating. His last flight in the gyroplane was four months before the accident. A postmortem examination of the pilot attributed the cause of death for the pilot to blunt force injuries. Additionally, the examination found severe (60 to 70 percent) occlusive arteriosclerotic cardiovascular disease. The FAA's Rotorcraft Flying Handbook contains a discussion of pilot-induced oscillation (PIO), and power pushover situations. The handbook notes that gyroplanes experience a slight delay between control input and the reaction of the aircraft. This delay may cause an inexperienced pilot to apply more control input than required, resulting in a greater aircraft response than was desired. Once the error has been recognized, opposite control input is applied to correct the flight attitude. Because of the nature of the delay in aircraft response, it is possible for the corrections to be out of synchronization with the movements of the aircraft and aggravate the undesired changes in attitude. The result is pilot-induced oscillations that can grow rapidly in magnitude. A power pushover, as described in the FAA handbook, may result if rotor force is rapidly removed, producing a tendency to pitch forward abruptly. This is often referred to as a forward tumble, buntover, or power pushover. Removing the rotor force is often referred to as unloading the rotor, and can occur if pilot-induced oscillations become excessive. A power pushover can occur on some gyroplanes that have the propeller thrust line above the center of gravity and do not have an adequate horizontal stabilizer. In this case, when the rotor is unloaded, the propeller thrust magnifies the pitching moment around the center of gravity. This nose pitching action could become self-sustaining and irreversible.
Probable Cause: The pilot's abrupt liftoff during takeoff, and his failure to correct a pilot-induced-oscillation during takeoff initial climb which resulted in the main rotor blades striking the tail mounted rudder, and an in-flight loss of control. A factor in the accident was the pilot's lack of recent experience in a gyroplane.




Revision history:

28-Oct-2008 00:45 ASN archive Added
21-Dec-2016 19:24 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
09-Dec-2017 16:46 ASN Update Bot Updated [Operator, Departure airport, Source, Narrative, Plane category]

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