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On August 16, 2006, about 1300 Pacific daylight time, an Extra Flugzeugbau GMBH EA-300, N12DW, impacted flat desert terrain about 175 yards outside of the airport perimeter fence (northeast) at Mojave Airport (MHV), Mojave, California. The pilot/owner operated the airplane under the provisions of 14 CFR Part 91 as a personal flight. The airplane was substantially damaged. The pilot, the sole occupant, was seriously injured. Visual meteorological conditions prevailed for the local area aerobatic flight, and no flight plan had been filed.
According to the pilot's written statement, he was practicing torque rolls at the time of the accident. He identified how the maneuver was performed; the airplane was flown in a vertical line and when the airspeed dissipated to near 0 knots, the torque of the engine moves the airplane in a roll orientation. The airplane begins to "fall backward" and flight controls are used to keep the airplane in a vertical orientation with the nose pointed straight up. At a certain point in the descent, directional and longitudinal stability cause the airplane to swap ends and a return to a normal forward trajectory of flight. The airplane's nose is now pointed towards the ground, and as the airspeed increases, the pilot pulls back to level flight. The pilot stated that an altitude check is monitored throughout the maneuver (fall) to assure that sufficient altitude is available for recovery. He stated that he normally maintains an altitude of 1,000 feet above ground level (agl) for the maneuver, at which time he normally initiates a recovery to level flight.
On the accident maneuver, the pilot stated that as he started to pull level, he felt that something had jammed the elevator control in a position that would not allow him to pull the stick in the aft position. He thought there was either a mechanical failure in the elevator circuit or something had jammed the control. He "wiggled the stick, but received no response." He felt that he was too low to use the parachute and continued to pull back on the stick with only limited elevator effectiveness/response. He stated that the airplane struck the ground at a low angle of attack.
A Federal Aviation Administration (FAA) airworthiness inspector responded to the accident site. He reported that the debris field was elongated, about 100 yards in length. The debris path was along a north/south orientation, and the airplane came to rest upright on a magnetic heading of 060 degrees. He indicated that the impact appeared to be at a very high velocity and hard impact, with several divots found along the length of the debris path. He located the first identified point of contact (FIPC) as the tail wheel; as well as, multiple "deep" propeller blade strikes in the hard dirt. Both wings separated and a post impact fire started at the right wing root area, but was extinguished by responding fire department personnel. The FAA inspector further reported that the engine came to rest about 10 yards past the fuselage.
The FAA inspector interviewed a helicopter emergency medical services (HEMS) crew that witnessed the accident. The HEMS crew was located at the airport, about 1 1/2 miles away from the accident site. They watched the airplane complete several "tail slide" maneuvers, and then saw it flat spin and hit the ground. They responded to the accident site, assisted with the extrication of the pilot from the airplane, and then transported the pilot to a local area hospital.
The FAA inspector also interviewed a tower controller. The controller reported that he had cleared the pilot for takeoff to work in the aerobatic box, and had no further contact with the pilot. The controller further reported that he did not witness the accident.
The National Transporation Safety Board investigator-in-charge (IIC) interviewed several witnesses about 2 nm from the accident site at the National Test Pilot School. The witnesses reported observing the accident airplane performing low-level aerobatics. They watched the airplane complete one practice run, which included a maneuver that they thought was a Cuban 8. They stated that as the airplane came out of the bottom of the maneuver, the nose was pitched up, about 30 degrees, and the airplane appeared to stall (no forward velocity), which they thought was intentional. The airplane started its second run and was performing this maneuver when the airplane dropped below their vantage point due to a parked MD-11 commercial jetliner that was about 0.5 nm from the school. The airplane had the same nose up attitude. They did not see the airplane contact the ground, but estimated the height above the ground as 100 feet agl before it dropped behind the MD-11. The witnesses observed a column of brown dust and heard the engine "run-up" after they lost sight of the airplane. Witnesses reported that the engine sounded "strong and normal."
Other witnesses identified by the Safety Board IIC were located at the XCOR Aerospace Facility. They reported that the pilot had been performing low-level aerobatics all week. The witnesses stated that due to the linear distance of the airplane, height estimation was difficult to ascertain, but appeared to be "uncomfortably low." Witnesses reported that on the downside of the loop the airplane appeared to transition from a nose down attitude to nearly horizontal flight, but still descending before their view was obstructed by a parked commercial jetliner as the airplane dropped below it.
TEST AND RESEARCH
The Safety Board IIC, Extra Aircraft, and Textron Lycoming, parties to the investigation, inspected the airplane and engine at Aircraft Recovery Service, Littlerock, California, on August 30, 2006. There were no discrepancies noted with either the airframe or the engine.
Engine continuity was established through manual rotation of the engine. Thumb compression was obtained in proper firing order on all six cylinders, with mechanical and valve train continuity observed. Magneto-to-engine timing could not be achieved due to impact damage and displacement of both the left and right magnetos from their respective mounting pads. A functional test of the left magneto produced spark at all of its leads. The right magneto sustained damage that rendered the magneto inoperative, and a functional check could not be performed. There were no mechanical anomalies that would have precluded normal operation.
Investigators established flight control continuity from the cockpit to the ailerons, elevator, and rudder. The elevator counterweight was intact and in place. The elevator trim system was also inspected and found to be intact. Elevator travel was limited due to deformation of the belly and collapsed rear seat. The main torque tube remained intact, but the manufacturer's representative noted it was severely bent and displaced from the forward attachment. There were no foreign objects found in the tube assembly. All flight control deformations and breaks were attributed to impact forces. The airplane was equipped with the old style rudder pedal secondary stops; however, those remained intact and in place. The bottom closing rib of the rudder assembly sustained damage after the tail spring contacted it. The airframe manufacturer attributed the damage to the impact. Chaffing marks were noted at the top of the vertical fin where the rudder counterweight had impacted it. The G-meter was pegged negative and showed 8 G positive, which the airframe representative indicated was most likely the load on the airplane at the time of impact.
The tail gear had separated from its attachment assembly in an upward bending motion. The propeller assembly and spinner remained attached to the engine. The three-bladed MT propeller had splintered after it contacted the ground; however, varying lengths of propeller blades remained attached to the propeller hub.
The Safety Board IIC and Extra Aircraft traveled to the accident site on August 30, 2006. Investigators took the separated tail wheel landing gear with them to the accident site. Investigators were able to determine that the airplane impacted in slight nose high, tail low attitude. The tail wheel had left a divot in the ground and forward of the divot was a flattened displaced area similar in dimension to the empennage and fuselage of the airplane. About 21 feet from the tail wheel was a portion of engine cowl. In that same location on either side of the debris field centerline, were pieces of debris identified by the airframe manufacturer as being wing structure. Investigators measured 27 feet 6 inches from the debris centerline to the end of the wing structure debris. The airframe manufacturer reported that the wingspan of the airplane is 26 feet 3 inches. Investigators also found three parallel slash marks in the hard desert terrain that were about 10 inches apart from each other. These marks were just forward of the initial crater. To the left of the debris path was debris identified as propeller material.