PALMER, AK, USA
N435PR
DENZER RAF 2000
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.
HISTORY OF FLIGHT On June 29, 2002, about 0948 Alaska daylight time, a wheel-equipped experimental/homebuilt Denzer RAF 2000 gyroplane, N435PR, sustained substantial damage when it collided with the paved runway surface following a loss of control during initial takeoff climb at the Palmer Municipal Airport, Palmer, Alaska. The gyroplane was being operated as a Title 14 CFR, Part 91 visual flight rules (VFR) local area personal flight when the accident occurred. The gyroplane was operated by the pilot. The private certificated airplane pilot, the sole occupant, received fatal injuries. Visual meteorological conditions prevailed, and no flight plan was filed. The flight originated from the Palmer Airport about 0930. At 0924, the pilot contacted the Federal Aviation Administration (FAA) flight service station specialist at the Palmer Airport via radio. The pilot reported he was at the transient apron, and requested traffic advisories. The flight service specialist indicated the winds were light and variable, southeasterly, 130 degrees at 6 knots. About 0930, the pilot radioed that he was ready to depart runway 16. The gyroplane was observed by the flight service station specialist, and several witnesses around the airport, to conduct two touch and go landings on runway 16. About 0941, the pilot radioed that he was extending his downwind pattern, and was number two behind landing traffic. At 0942, the pilot reported he was on final approach for landing on runway 16. Following the third landing, ground witnesses observed the gyroplane lift off abruptly, climb steeply to an altitude of less than 100 feet above the ground, and then nose over and descend. One witness reported hearing "popping" sounds, and then observed the gyroplane in a steep descent. Other witnesses said the gyroplane went through one or more longitudinal axis pitch oscillations. They saw the main rotor slow down and strike the tail-mounted vertical stabilizer and rudder. The gyroplane then descended to the runway in a steep nose-down attitude. A fixed-based operator at the Palmer Airport utilizes a wide-angle video camera, along with a video recorder, to observe the activity around the business. The camera is pointed toward the south. The operator provided a copy of their video tape to the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) for review. An examination of the video recording revealed that during play-back, it ran at twice normal speed. A barely visible, distant image of the gyroplane was observed on the recording entering the left side of the video screen. The gyroplane made an arching climb and descent path from the runway to impact on the runway. PERSONNEL INFORMATION The pilot held a private pilot certificate with an airplane single-engine land rating that was issued on August 29, 1999. The most recent third-class medical certificate was issued to the pilot on August 15, 2000, and contained the limitation that the pilot shall possess glasses that correct for near vision. The pilot transported the accident gyroplane, via trailer, to Brewton, Alabama, where he began receiving flight training on January 16, 2002, and concluded training on February 2, 2002. On February 3, 2002, the pilot completed an application for an additional private pilot rating, rotorcraft gyroplane, and the application was endorsed by the pilot's flight instructor. 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 (flight) 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. According to the pilot's flight instructor, the pilot planned to return to Alaska with the gyroplane via trailer, and planned to complete the practical test portion of the gyroplane rating from a gyroplane examiner, either en route, or after reaching Alaska. According to the pilot's logbook, his total aeronautical experience consisted of about 204 hours, of which 160 hours were accrued in airplanes, and 44 hours in the accident gyroplane. The last flight the pilot logged in the accident aircraft was on February 28, 2002. The FAA has no record of the pilot taking a practical test for a gyroplane rating. The pilot held a repairman certificate with an experimental aircraft builder rating for the accident aircraft. It was issued on June 2, 2002 by FAA personnel from the Anchorage Flight Standards District Office. AIRCRAFT INFORMATION The RAF 2000 gyroplane design is comprised of a T-shaped box-beam airframe with tricycle gear, a two-seat enclosed cockpit, and a free spinning two-bladed rotor attached at the top of a mast. The gyroplane is equipped with a pre-rotator drive. Behind the seat is an aft-facing gasoline powered, water-cooled, 4 cycle automotive engine modified for use in the gyroplane. The engine is equipped with a three-bladed composite pusher propeller. A vertical tail and rudder, along with about a 6-inch diameter tailwheel, is attached at the aft end of the airframe beam, behind the engine assembly. The gyroplane kit was purchased by the pilot in March, 2000. It was completed by the pilot in Alaska in August 2001, and registered by the pilot with the FAA on September 19, 2001. The gyroplane was transported to Alabama in January, 2002, via trailer, for the purpose of training. Examination of the gyroplane's amateur-built aircraft log book revealed that the pilot certified the aircraft as having been inspected in accordance with the scope and detail of Appendix D, CFR Part 43, on January 7, 2002. The gyroplane was issued a Certificate of Airworthiness on January 9, 2002, by an FAA Designated Airworthiness Representative (DAR) in Alabama. The DAR requested that the FAA issue the pilot/owner a repairman certificate. On the same date, the aircraft was also issued Phase I and Phase II Experimental Operating Limitations by the DAR. At the time of the accident, the gyroplane had accumulated a total time in service of 56.9 hours. METEOROLOGICAL INFORMATION At 0953, an Aviation Routine Weather Report (METAR) at Palmer was reporting, in part: Wind, variable at 4 knots; visibility, 10 statute miles; clouds and sky condition, few at 7,500 feet; temperature, 59 degrees F; dew point, 48 degrees F; altimeter, 29.54 inHg. COMMUNICATIONS The pilot communicated with the inflight position of the Palmer Flight Service Station (FSS). A transcript of the air to ground communications between the gyroplane and the Palmer FSS facility is included in the public docket of this accident. AERODROME AND GROUND FACILITIES The Palmer Airport is equipped with a hard-surfaced runway on a 160/340 degree magnetic orientation (runway 16/34), a parallel gravel-surfaced runway on a 140/320 degree magnetic orientation (runway 14/32), and a hard-surfaced runway on a 090/270 degree magnetic orientation (runway 9/27). On the day of the accident, runway 16 was in use. It has a displaced threshold of 500 feet, and is 6,000 feet long and 60 feet wide. WRECKAGE AND IMPACT INFORMATION The NTSB IIC examined the airplane wreckage at the accident site on June 29, 2002. Four lateral gouge marks, perpendicular to the centerline of the runway surface, were the first impact marks located along the centerline of runway 16 at the Palmer Airport. The gouge marks began about 300 feet south of the runway's 4000 feet remaining sign. The first gouge mark was 13 inches long, just east of the runway centerline. The second gouge mark was 12 inches long, and 12 feet, 5 inches south of the first mark. The third mark was 26 inches long, and 11 feet, 9 inches south. The last mark was 23 inches long, and 11 feet, 2 inches south of the third mark. These gouge marks were followed by broken portions of the gyroplane's propeller blades, and portions of the rudder and vertical stabilizer that were located along the west side of the runway centerline. The gyroplane's main point of impact with the runway was located about 311 feet south of the last gouge mark. At the point of rest, the gyroplane was lying on its left side. The aft end of the airframe beam with the tailwheel assembly was sheared at the rear engine support bracket, and was located about 30 feet north of the fuselage point of rest. The nose wheel was broken away from the airframe and was located west of the runway centerline, to the west and north of the fuselage point of rest. The rudder bellcrank assembly, separated from the airframe, was found on the runway east of the centerline, just prior to the main fuselage point of rest. The center core of the rudder structure was broken away from the bellcrank assembly. The two-bladed rotor assembly, consisting of the teetering hinge, rotor hub bar, pre-rotator drive and cable, the control pushtubes and torque tube assembly, was separated at its attach point to the rotor mast. The upper end of the rotor mast was bent slightly to the right. The rotor blades remained attached to the rotor hub bar. One rotor blade was bent upward mid-span about 15 degrees. The second rotor blade had downward, span-wise bending. Flight control system continuity was established from the cockpit to the torque tube assembly. The continuity of the rudder control cables was established from the cockpit area to the point of separation from the rudder bellcrank. The ends of the separated rudder cables had a broom straw appearance. The three-bladed composite propeller assembly remained connected to the engine crankshaft. The outboard ends of each blade were sheared on about a 45 degree angle from the leading edge, inboard toward the trailing edge. Each blade was sheared progressively closer toward the inboard end of the blades. The engine was not damaged by impact. The crankshaft could be rotated by movement of the starter ring gear. The bottom manifold of the radiator was fractured and separated from the radiator. Fuel was present in fuel lines to the point of separation at the fuel filter. Two plastic jug-type containers of sand, tied together, were located on the runway, adjacent to the main wreckage. MEDICAL AND PATHOLOGICAL INFORMATION A postmortem examination of the pilot was conducted under the authority of the Alaska State Medical Examiner, 4500 South Boniface Parkway, Anchorage, Alaska, on July 1, 2002. The examination revealed the cause of death for the pilot was attributed to blunt force injuries. Additionally, the examination found severe (60 to 70 percent) occlusive arteriosclerotic cardiovascular disease. A toxicological examination was conducted by the FAA's Civil Aeromedical Institute (CAMI) on August 26, 2002, and was negative for any alcohol or drugs. ADDITIONAL INFORMATION The FAA's Rotorcraft Flying Handbook contains seven chapters pertaining to the gyroplane. Chapter 21, Gyroplane Emergencies, includes, among others, a discussion of pilot-induced oscillation (PIO), and power pushover situations. The FAA handbook states, in part: "As with most other rotor-wing aircraft, 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, causing 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, states, in part: "...the stability of a gyroplane is greatly influenced by rotor force. If rotor force is rapidly removed, some gyroplanes have 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, if extremely turbulent conditions are encountered, or the nose of the gyroplane is pushed forward rapidly after a steep climb. 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. Unless correction is made, this nose pitching action could become self-sustaining and irreversible." The Safety Board did not take custody of the wreckage. No parts or components were retained by the Safety Board.
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.
Source: NTSB Aviation Accident Database
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