Oklahoma City, OK, USA
N6KT
Stevens KB-2
The amateur built gyroplane was flying on the downwind leg for runway 17L, approximately 250 feet downwind from a group of deciduous trees and a row of aircraft hangars, while at an estimated altitude of 100-150 feet above ground level (agl). Near the midfield point, the gyroplane suddenly pitched to a nose down angle of approximately 60 degrees and subsequently impacted the ground. About 30 minutes earlier, a weather observation facility located 12 nautical miles southeast from the site of the accident was reporting, wind from 190 degrees at 21 knots gusting to 24 knots. Inspection of the wreckage did not reveal any mechanical failure/malfunction which would have resulted in the loss of control; however, the investigation did reveal that this was the pilot's first flight after removing the gyroplane's horizontal stabilizer.
HISTORY OF FLIGHT On February 18, 2007, about 1620 central standard time, a Stevens KB-2 single-engine gyroplane, N6KT, was substantially damaged when it collided with terrain while on the downwind leg of the traffic pattern at the Clarence E Page Municipal Airport (F29), near Oklahoma City, Oklahoma. The commercial pilot, the sole occupant, sustained fatal injuries. The gyroplane was registered to and operated by the pilot. Visual meteorological conditions prevailed and no flight plan was filed for the 14 Code of Federal Regulations Part 91 personal flight. The local flight originated approximately 1555. According to witnesses at the airport, the pilot initially departed runway 17L and completed one circuit around the traffic pattern. While approaching the north end of runway 17L the pilot appeared to "hover" into the wind and performed several "rudder turns." The pilot then proceeded to perform a touch-and-go maneuver and started around the traffic pattern a second time. The witnesses further reported that while on the downwind leg of the traffic pattern, the gyroplane appeared to fly straight and level at an estimated altitude of 100-150 feet above ground level (agl). About half way along the downwind leg of the traffic patern, the gyroplane suddenly pitched to a nose down attitude and subsequently impacted the ground. One witness reported that the gyroplane descended with an approximate nose down angle of 60 degrees "while rolling left and right." PERSONNEL INFORMATION The pilot, age 46, held an airline transport pilot certificate with ratings for airplane single-engine land, multi engine land and rotorcraft helicopter. The pilot also held a commercial pilot certificate for airplane single engine sea and rotorcraft gyroplane. In addition, the pilot held a certified flight instructor certificate with ratings for airplane single-engine land, multi-engine land, rotorcraft, rotorcraft gyroplane, instrument airplane, and instrument rotorcraft. His last Federal Aviation Administration (FAA) second-class medical was issued on October 2, 2006, with the limitation of "MUST WEAR CORRECTIVE LENSES." An examination of the pilot's logbook indicated an estimated total flight time of 12,251 hours; of which 160 hours were in gyroplanes. The pilot logged 15 hours in the last 30 days of which 3 hours were in gyroplanes. His last noted flight review was completed January 12, 2007. AIRCRAFT INFORMATION The 2004-model Stevens KB-2, serial number 001, was a amateur built single engine gyroplane, configured for one occupant. The gyroplane was powered by an air-cooled, normally aspirated, direct drive, horizontally opposed, carbureted, four-cylinder engine. The engine was a Great Plains 1835, rated at 60 horsepower at 3,400 rpm, and was driving a two-bladed fixed pitch Tennessee wooden propeller. According to the combined airframe and engine logbook, the gyroplane's most recent annual condition inspection was completed on November 26, 2006, with an airframe total time of 140 hours. At the time of the accident, the airframe and engine had accumulated approximately 142 hours and 2 hours since the last inspection. METEOROLOGICAL INFORMATION At 1552, the weather observation facility at the Will Rogers World Airport (OKC), near Oklahoma City, Oklahoma, located 12 nautical miles southeast from the site of the accident was reporting, wind from 190 degrees at 21 knots gusting to 24 knots, visibility 10 statute miles, few clouds at 20,000 feet, temperature 60 degrees Fahrenheit, dew point 25 degrees Fahrenheit, and a barometric pressure setting of 30.11 inches of Mercury. AIRPORT INFORMATION Clarence E Page Municipal Airport (F29), was a non towered airport operating under class E classification airspace. The field elevation was 1,353 feet mean sea level (msl). Runway 17L was a 3,502-foot-long by 75-foot-wide concrete runway. WRECKAGE AND IMPACT INFORMATION The wreckage was located in a grassy area adjacent to an asphalt road approximately 250 feet east of a group of deciduous trees and a row of aircraft hangars. The debris field encompassed an area about 80-feet long and approximately 20-feet wide, on a magnetic heading of 335 degrees. Ground scars were consistent with the gyroplane impacting the ground while in a tail low and inverted position. All major components of the gyroplane were accounted for at the accident site with the exception of the horizontal stabilizer. The horizontal stabilizer was later located in the pilot's hangar. The gyroplane was found fractured in seven separate sections. The sections were as follows: forward airframe including the front wheel and instrument console, center airframe section with the lower mast and about three fourths of the landing gear with right wheel attached, aft airframe with vertical stabilizer and rudder partially attached, fuel tank/seat and upper mast, remainder of the landing gear with left wheel attached, engine with propeller hub, and the rotor head with attached rotor blades. Continuity was established from the rudder pedals to the rudder and from the cyclic stick to the rotor. One main rotor blade exhibited trailing edge compressions and a gradual downward bend and the other blade remained nearly straight with little damage. Both blades remained attached to the hub, but separated from the mast. The gyroplane's seat doubled as a fuel tank. Although the fuel tank was found compromised, it contained a blue liquid consistent with 100 low lead aviation fuel. The engine was suspended from a lift, and the spark plugs and valve covers were removed. Investigators manually rotated the engine via the propeller hub. Valve train continuity was established to each cylinder and thumb compression was established. The spark plug electrodes were light grey in color and did not contain lead deposits. Due to impact damage, spark could not be established from the engine's ignition system. The propeller hub remained attached to the engine crankshaft flange. Both of the wooden propeller blades were found splintered and spread throughout the wreckage site. The examination of the airframe and engine revealed no evidence of preimpact mechanical failure/malfunction. MEDICAL AND PATHOLOGICAL INFORMATION According to the Office of the Chief Medical Examiner, Oklahoma City, Oklahoma, the cause of death was blunt force trauma. The FAA's Civil Aerospace Medical Institute performed forensic toxicology on specimens from the pilot and no drugs of abuse were detected. ADDITIONAL INFORMATION According to FAA publication, Rotorcraft Flying Handbook (FAA-H-8083-21), "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." The handbook further states, "an adequate horizontal stabilizer slows the pitching rate and allows time for recovery." Investigators were able to establish that this was the pilot's first flight since removing the gyroplane's horizontal stabilizer.
The pilot's failure to maintain control of the gyroplane while in the traffic pattern. Contributing to the accident was the high wind with terrain induced turbulence and the absence of the gyroplane's horizontal stabilizer.
Source: NTSB Aviation Accident Database
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