Alameda, CA, USA
N91472
NORTH AMERICAN NAVION A
A pilot-rated witness reported that the airplane’s initial climb was normal and that the engine sounded good; however, as the airplane continued to climb, the engine lost power as if the throttle had been retarded or the mixture control placed in the idle cutoff position. The witness further reported that the airplane began a descending left turn and continued to descend until he lost sight of it. Another pilot reported hearing “emergency emergency” transmitted on the control tower frequency shortly after the accident airplane was cleared for takeoff. Examination of the accident site revealed that the airplane impacted terrain in a steep nose-down attitude. Postaccident examination of the airframe and engine revealed no evidence of any preaccident mechanical malfunctions or failures that would have precluded normal operation. The airplane was equipped with auxiliary wing tip fuel tanks, and the five-point positive lock fuel selector valve was found in the right tip tank position. The fuel selector rotated freely and flow continuity was confirmed for each position. The left and right auxiliary tip tanks were separated from the wing tips and contained fuel; the left and right main tanks were breached; and the main auxiliary tank was intact and contained fuel. The flight manual supplement for the tip tanks stated that the auxiliary tip tank fuel was to be used in level flight only. However, it could not be determined if the fuel selector valve’s position as found resulted in fuel starvation to the engine and the subsequent loss of engine power. The flight path observed by the witness and the damage to the airplane were consistent with the pilot maneuvering the airplane for an emergency landing and allowing the airspeed to decay, which resulted in an aerodynamic stall.
HISTORY OF FLIGHT On April 3, 2011, about 1537 Pacific standard time, a North American Navion A, N91472, collided with the ground while maneuvering after takeoff in the vicinity of Alameda, California. The certificated private pilot, the sole occupant of the airplane, was fatally injured. The airplane was registered to the pilot, and operated as a personal flight under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no flight plan was filed for the local flight that originated from the Metropolitan Oakland International Airport (OAK), Oakland, California, about 1536. A pilot rated witness reported that the airplane’s initial climb was normal and the engine sounded good. He reported that shortly thereafter, about 200 feet above the ground, the engine shutdown as if the throttle had been retarded or the mixture control pulled to idle cutoff position. He reported that the airplane began a descending left turn and continued to descend beyond the witness’s vantage point. Witnesses reported hearing “emergency emergency” transmitted on the Oakland tower frequency shortly after the accident airplane was cleared for takeoff from runway 33. There was no further radio communications from the pilot of the accident airplane. AIRCRAFT INFORMATION The airplane, a Navion A model, serial number NAV-4-279, was manufactured in 1946 and was powered by a Continental IO-470 engine. The airplane was equipped with a constant speed propeller and Osborne 20-gallon wing tip fuel tanks. Review of maintenance records showed that the airplane’s most recent annual inspection was completed on August 5, 2010. The airframe total time at inspection was 2,676 hours. The engine’s total time at inspection was 2,023 hours (938 hours since major overhaul). Maintenance records indicated that the airplane was retrofitted with an American Navion Society ANS3 fuel selector valve concurrent with the August 5, 2010, annual inspection. WRECKAGE AND IMPACT INFORMATION An airworthiness inspector from the Federal Aviation Administration (FAA) responded to the accident site shortly after the accident occurred and reported that the airplane came to rest within a tidal estuary approximately 0.5 miles northwest of the departure runway. The airplane was partially buried below mud and water and the fuselage and wing assembly sustained extensive structural damage. The inspector reported that both main wing fuel tanks were breached and had leaked an unknown amount of fuel into the bay. The auxiliary fuel tank under the aft seat was intact and contained fuel. Both wing tip fuel tanks were separated from the wings and imbedded within the mud. The tip tanks were recovered the following day; both tanks contained an undetermined amount of fuel. TESTS AND RESEARCH A postaccident examination of the airframe and engine was conducted after the airplane was moved to a storage facility. The engine compartment and forward section of the airframe was fragmented and extensive aft crushing was noted. The cockpit and cockpit controls sustained extensive impact related damage, and deformation was noted throughout. All flight control surfaces were located within the recovered wreckage. The forward section of the fuselage and cockpit were crushed aft. A majority of the cockpit components and instrumentation was fragmented and extensive deformation was noted. Extensive leading edge aft crushing was noted to the wings. The flap assemblies remained attached to the wing structure. The ailerons were in place and bending damage was noted to the outboard end of the left aileron. The empennage remained attached to the airframe during the impact sequence, but was removed to facilitate transportation of the wreckage. All flight control surfaces remained attached and continuity was confirmed via the control cables, from the aerodynamic surfaces to the points where the cables were cut to facilitate wreckage transportation. The five point positive lock fuel selector was found in the right tip tank position. The fuel selector moved freely, to and from each position, and flow continuity was confirmed for each position. The engine was removed from the airframe to facilitate the exam. Extensive impact related damage was noted throughout the engine, engine accessories and propeller assemblies. The propeller assembly was partially separated from the crankshaft propeller flange. The spinner was removed and the propeller assembly broke away from the crankshaft flange. The top spark plugs were removed and the cylinders were borescoped; the combustion chambers and piston heads were undamaged. Mud and debris were found in the combustion areas. The crankshaft was rotated from the upper left accessory drive. Cylinder compression was obtained in cylinders 2, 3, 4, 5 and 6 by manually rotating the crankshaft. The oil sump was removed and the camshaft and lifters were visible and undamaged. The No. 6 cylinder was removed from the engine and mud was found in the combustion chamber. The crankcase internal components as viewed from the No. 6 cylinder bay were lubricated and no mechanical damage or thermal discoloration was noted. The magnetos were in place and no external damage was noted. The right magneto drive manually rotated freely with impulse coupling engagement. Spark was not obtained and the magneto was disassembled. The internal components were water soaked. The left magneto drive could not be rotated and was disassembled. The internal components were not damaged. The internal components were water soaked. The examination of the engine revealed no preaccident mechanical malfunctions or failures that would have precluded engine operations. ADDITIONAL INFORMATION The airplane was equipped with Osborne 20-gallon wing tip fuel tanks. The Osborne Airplane Flight Manual Supplement, Procedures Section, stated in part, that the auxiliary tip tank fuel only be used in level flight to preclude the possibility of overflowing the main fuel tank due to excessive fuel return from the fuel delivery system. The fuel selector valve in the accident airplane was not placarded with the before mentioned tip tank flight procedures. It was not determined if the position of the fuel selector valve contributed to the pilot’s in-flight emergency and accident sequence.
The pilot’s failure to maintain airspeed while maneuvering for an emergency landing, which resulted in an aerodynamic stall. Contributing to the accident was the loss of engine power for undetermined reasons during initial climb.
Source: NTSB Aviation Accident Database
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