Petaluma, CA, USA
N5704L
American AA1B
The aircraft stalled, entered a spin, and descended to ground impact following a loss of engine power in the takeoff initial climb. During the climb out following a touch-and-go, the airplane's engine sputtered and backfired. The airplane made a low and tight downwind turn. The airplane paralleled the runway before it pitched nose up and entered a stall, which was followed by a nose down right-hand spin; the airplane then impacted a grass fairway on a golf course adjacent to the airport. Examination of the airframe revealed that the right-hand fuel tank contained very little fuel while the left fuel tank was half full. The fuel selector valve was positioned to the right-hand fuel tank. The carburetor bowl contained 5 milliliters of fuel, which is consistent with fuel starvation. The fuel selector valve handle was separated from the stem post and the fracture surface of the post at the selector handle interface is consistent with bending overload forces that would have occurred during the airframe's collision with terrain and buckling of the instrument panel. The fuel selector valve had not been lubricated in accordance with the manufacturer's recommended servicing instructions, which resulted in binding. The binding caused the fuel valve to require approximately three times the normal force to operate it.
HISTORY OF FLIGHT On February 9, 2005, at 1600 Pacific standard time, an American AA1B, N5704L, collided with terrain following an uncontrolled descent at the Petaluma Municipal Airport, Petaluma, California. The airplane was operated by the owner under the provisions of 14 CFR Part 91. The commercial pilot was fatally injured and the airplane was destroyed. Visual meteorological conditions prevailed and a flight plan had not been filed. The flight originated at Petaluma airport about 1540. Witnesses reported to the National Transportation Safety Board investigator that the airplane had completed at least one touch-and-go to runway 11. During the climb out following a touch-and-go, they heard the airplane's engine sputter and backfire. The airplane turned towards a downwind direction and was about 100 feet above ground level (agl) and 100 feet offset to the north of the runway. The airplane paralleled the runway before it pitched nose up and entered a nose down vertical descending right turn, impacting the grass fairway of a golf course. No distress call by the pilot was heard on the airport's common advisory frequency. PERSONNEL INFORMATION A review of Federal Aviation Administration (FAA) records revealed that the pilot held a commercial pilot certificate with airplane single engine land and instrument ratings, which was issued on July 30, 1997. The pilot held a second-class medical certificate that was issued on May 5, 2003, that contained the limitation he must wear corrective lenses. An examination of the pilot's logbook indicated that he had accumulated a total of 618.4 flight hours, of those hours, 279 were in the AA1B. A biannual flight review was documented on August 21, 2003. The logbook annotated that the pilot's last four flights were flown since September, all of which were 0.3 hours in duration, and in which three landings were performed. In a majority of the flights since April 2002, the pilot recorded in the remarks section that he had flown in the right seat of the airplane. AIRCRAFT INFORMATION The airplane was an American AA-1B, serial number AA1B-0030, which is a low-wing, fixed landing gear, two-place airplane operating a Lycoming O-320-E2G engine. A review of the airplane's logbooks revealed a total airframe time of 2,083.9 hours at the last annual inspection on May 1, 2004. The engine tachometer examined on scene read 2,095.68 hours. The AA1B service manual contains a comprehensive checklist for the performance of the annual/100 hour inspection. Contained in the checklist is line item 15 under section C (cabin group), "Disassemble, clean, lubricate, and reassemble fuel selector valve every 500 hours." The maintenance logbook review revealed no entry of the fuel valve maintenance performed during the last 991 hours of operation. WRECKAGE AND IMPACT INFORMATION The wreckage was located on the Rooster Run golf course at 38 degrees 15.776 minutes north latitude and 122 degrees 36.686 minutes west longitude, at an elevation of 87 feet mean sea level (msl). The terrain consisted of level ground and short cut fairway grass. The longitudinal axis of the airplane was aligned on a magnetic bearing of 195 degrees. The pilot was located in the right seat. A deceased German shepard dog was also located on the grass outside the cockpit. The airplane was resting upright on its main landing gear with the engine compartment rotated down approximately 80 degrees about the lower firewall. The engine was resting vertically down with the propeller slightly imbedded into the turf. The empennage was vertically buckled about 20 degrees at a location behind the cockpit and rested flat against the turf. The left wing was intact and the right wing laid upside down on the right side of the airplane; the wing spar was fractured at the wing root location. Three feet of the right wing tip structure was crushed aft about 30 degrees from the wing tip leading edge inboard. The right wing also exhibited 45-degree wing skin rippling from inboard to outboard. The tubular wing spar fracture on the right wing exhibited a gray matte colored fracture surface with a 45-degree shear lip all the way around the spar. Both flaps and aileron control surfaces were attached to their respective wings. The flap on the left wing was extended approximately 30 degrees down. The empennage laid flat against the ground behind the cockpit. The vertical and horizontal stabilizers exhibited very little damage except to the fiber glass tip fairings. The rudder and elevator control surfaces were present on their hinges. The flight control cables were traced from their cockpit attachment points to their respective bell cranks and control tubes. The cockpit canopy structural frame was bent around the right side of the fuselage and its Plexiglas windscreen was shattered and strewn about the north side of the wreckage field. The cockpit seats were in the aft area of the cockpit and the instrument panel was twisted and fractured with many of the instruments not in place. The fuel selector knob was not present on the fuel valve post, and the valve was dislocated from its normal alignment with the center console and associated fuel selector position markings. The master switch was in the "on" position and the ignition key was in the "both" position. The elevator trim indicator was centered in the upper area of the green "TO" arc. The flap switch was in the middle position and the flap indicator showed down. The throttle and mixture knobs were both extended 1/2-inch. The carburetor heat was "in" and the primer knob was locked. The Hobbs meter read 1452.4 and the engine tachometer read 2095.68. Clear bluish fluid was identified in the left wing fuel tank. The left wing fuel sight gauge indicated half full. The right wing fuel tank was breached at the wing root. No fluid was identified in the right wing fuel sight gauge. The grass below right fuel tank was green and flush. First responders to the accident reported that there was no odor of fuel at the accident site upon their arrival. The right fuel tank outlet suction screen was intact and clear of debris. Air was passed through the right fuel tank sight gauge inlet tube with no airflow restrictions identified. The right fuel tank sight gauge and associated tubing was disassembled and found to be clear and free of debris. The engine was attached to the firewall and the firewall was hinged downward about 80 degrees along its bottom lateral axis. The carburetor airbox was crushed and the carburetor control connections were all connected, bolted, and cotter keyed. The engine control cables were traced from the carburetor to the throttle, mixture, and carburetor-heat knobs in the cockpit. The engine exhaust was shaped in a flattened oval. The fixed pitch propeller had a 2-foot blade section bent aft approximately 15 degrees. The propeller exhibited no leading edge damage or chordwise scoring. The engine was examined on scene. The engine data plate identified it as a Lycoming O-320-E2G, serial number RL46828-27A. The spark plugs, Autolight URE-M40E's, were dark gray in color, similar gaps, round electrodes, and had no mechanical damage. The engine was rotated and thumb compression was achieved on all cylinders. All valves lifted the appropriate amount and in firing order. Both Slick magnetos were hand rotated and achieved sparks on all posts. The carburetor was disassembled. No debris was found in the carburetor fuel finger screen. Five milliliters of fluid was found in the carburetor bowl. The metal carburetor floats retained their manufactured form and exhibited no hydrodynamic deformation. The fuel line leading from the electric boost pump to the engine driven fuel pump contained 2 ml of fluid. The gascolator bowl and fuel totalizer contained no fluid. No fluid was found in the engine driven fuel pump. Using Kolorcut water detection paste, all fluid collected tested negative for water. MEDICAL AND PATHOLIGICAL INFORMATION The Sonoma County Sheriff-Coroner completed an autopsy of the pilot. The FAA Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicological testing of specimens obtained during the autopsy. The results of the analysis on the specimens were negative for carbon monoxide, cyanide, ethanol, and listed drugs. TESTS AND RESEARCH Fuel System The cockpit fuel tank selector valve was removed from the wreckage and tested by passing air through the valve. The valve is a three position valve; "left 11 gal", "right 11 gal", and "both off" positions. The valve has a left inlet and right inlet, with a center outlet. Air passed through the right inlet to the outlet and did not pass through the left inlet to outlet. Approximately 4 ml of bluish fluid with a petroleum odor was found in the fuel line leading from the right fuel tank to the fuel selector valve. The fuel selector handle was not identified in the wreckage or recovered during the on scene examination of the airplane. The fuel selector valve was brought to the Safety Board office in Los Angeles and examined in more detail. The valve selector knob/lever was not present on the valve post. The valve post end was examined under a microscope. It exhibited a bright matte surface with no discolorations, and 45-degree shear lips extending on one side of the cup shaped fracture, which is consistent with a bending overload failure. A green stain was identified in one quadrant of the fracture surface that is consistent with a condition occurring post fracture. Using vice grips on the stem and a spring scale, the torque required to rotate the valve selector post was measured between 18.62- to 21.28-inch pounds. The valve was disassembled, which revealed a shiny brass colored interior cup and a solid plastic valve plug. No debris or cracks were identified in the valve mechanism. An exemplar fuel valve of the same design, material, and configuration as the accident airplane's valve was obtained and the torque required to rotate the valve was measured as 8-inch pounds.
The pilot's failure to maintain an adequate airspeed above the stall speed (Vso) while maneuvering to a landing area that resulted in a stall-spin. Factors in the accident were the fuel starvation induced loss of engine power due to the pilot's fuel system mismanagement, and the mechanical binding of the fuel selector valve due to inadequate maintenance.
Source: NTSB Aviation Accident Database
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