History of Flight
On December 18, 2020, at 1322 eastern standard time, a Piper PA-28-140 airplane, registration N6978W, was destroyed in an accident near Tampa, Florida. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The flight instructor, student pilot, and a passenger (the airplane owner) sustained serious injuries.
The airplane departed Tampa International Airport (TPA) at about 0900 for Zephyrhills Municipal Airport (ZPH). Before departing ZPH to return to TPA, the airplane was fully fueled. It departed ZPH at about 1307 with the student pilot at the controls in the left seat. The flight instructor reported that the engine ran smoothly during the flight to TPA.
During the approach to TPA, the instructor taught the student to set the fuel pump on, carburetor heat in, mixture rich, flaps to 10°, and throttle to 1,700 rpm. The flight was cleared to land on runway 1R. The passenger, seated in the back seat and videotaping, noted that the student pilot adjusted his seat on final approach, causing the camera to "wiggle." Shortly after, the instructor observed the airplane's descent path becoming low and advised the student to add power. The student attempted to add power, but the engine did not respond. The instructor assumed control, established best glide speed, and attempted to restore engine power. He noted a momentary 200 rpm increase when cycling the throttle but could not restore power, with the engine "basically at idle."
The instructor declared an emergency to air traffic control, stating an engine failure. Realizing the airplane would not reach the runway, he attempted a forced landing on a small road, maneuvering to avoid obstacles. Surveillance video showed the airplane struck a utility pole and power lines in a parking lot about 0.6 nautical miles from the runway threshold. The airplane caught fire upon impact with the power lines, spun counterclockwise, fell to the ground, and came to rest upright next to the parking lot.
The passenger noticed the fuel pressure showed zero just before impact. The fuel selector was found in the wreckage fully in the OFF position. The instructor stated he did not direct the student to move the fuel selector to OFF during the approach or forced landing and did not observe him doing so. The student had no recollection of moving the fuel selector and would have taken action if he had noticed it inadvertently moved.
Aircraft Information
The accident airplane's fuel selector valve was the original four-position design in an "X" pattern, mounted on the left sidewall near the pilot's left leg. The lower two detents were both OFF positions, and the forward and aft upper detents selected right and left tanks, respectively. The valve and bezel allowed rotation to any position without stops or safety measures, including OFF.
The manufacturer subsequently modified the fuel selector bezel and handle twice. The second-generation design had three positions: OFF (fully counterclockwise), right (clockwise), and left (intermediate). The third-generation added a spring-loaded stop to prevent inadvertent OFF selection, requiring depression of the stop and rotation of the lever.
Examination of the airplane's logbook revealed that the fuel selector was replaced during the last annual inspection on September 15, 2020. The entry stated "Removed and replaced fuel selector with new," with no reference to Service Bulletin (SB) 840A, "Fuel Selector Valve Cover Replacement," dated November 7, 2013. The manufacturer considered compliance with this SB mandatory because the cover assembly would reduce "the possibility of pilot mismanagement of the fuel system through inadvertent selection to the OFF position." The invoice for the replacement included a certificate of conformity confirming the valve had the same part number (491-947) as in the illustrated parts catalog, which referenced the SB.
Wreckage and Impact
Photographs from first responders indicated that most of both wings and the fuselage were consumed by fire. The empennage remained intact, but the forward horizontal stabilator and vertical stabilizer showed thermal discoloration. The right horizontal stabilator was bent upward at midspan. The engine remained partially attached to the firewall, and the cowling was consumed. The propeller remained attached, and the spinner was crushed aft due to impact.
Examination revealed the engine was thermally damaged, with all accessories destroyed. Spark plugs were removed, and crankshaft rotation via the propeller established thumb compression and valve train continuity in all cylinders. Crankshaft and camshaft continuity was verified to the rear gears. No mechanical anomalies that would have precluded normal operation were found.
The upper carburetor and throttle valve remained attached. The carburetor bowl, floats, fuel hose, and fuel inlet screen were destroyed by fire. Throttle and mixture control cables remained attached to their arms. The engine-driven fuel pump was destroyed by fire.
The fuel selector handle was intact, and its OFF position (as found) was confirmed during a field test with low-pressure air. Thermal damage prevented movement of the selector's control lever.
Additional Information
The airplane manufacturer issued Service Letter No. 588 on September 3, 1971, to replace the existing fuel selector valve cover assembly with a "new and improved" cover. It also notified operators of an optional service kit to upgrade from second- to third-generation design. The Federal Aviation Administration (FAA) issued Airworthiness Directive (AD) 71-21-08 in 1971, requiring operators of airplanes with second-generation fuel selector covers and handles to comply with Service Letter 588, but not requiring upgrades for airplanes with original covers and handles.
On August 20, 2013, the FAA proposed a revision of AD 71-21-08 to include first-generation fuel selectors. However, on July 10, 2014, the FAA issued Special Airworthiness Information Bulletin CE-14-22, which stated that "the fuel selector valve can be inadvertently switched off and/or may bind when switching fuel tanks and can cause a loss of power in flight" and recommended "the installation of a fuel selector valve cover designed to prevent inadvertently selecting the off position and the maintenance of fuel selector valves to prevent their binding." The FAA noted that special airworthiness information bulletins are "information only. Recommendations aren't mandatory."