N15321Piper PA-28-140 · 1972

On December 22, 2018, about 1622 Pacific standard time, a Piper PA28-140, N15321, was substantially damaged when it was involved in an accident near Santa Ana, California. The flight instructor and student pilot were not injured. The airplane was operated as a Title 14 Code of Federal Regulations (CFR) Part 91 instructional flight.

The instructor stated that the student was flying the airplane during takeoff from runway 20L. After they reached about 250 ft above ground level, the engine lost total power. The instructor took the airplane controls and began to look for a landing site. He declared an emergency and initiated a return to the airport with the intention of landing on runway 2R. The instructor stated that, just before landing, the airplane encountered a strong wind shear, and they landed hard on an intersecting taxiway. The airplane sustained substantial damage to both wings and the forward fuselage.

Evidence of 100 low-lead aviation gasoline was found in the fuel supply system. All fuel lines were intact at their respective fittings, and all filters and screens were free of debris. The engine’s internal drivetrain was intact and there was no evidence of catastrophic failure. Both magnetos produced sparks when tested. The spark plugs exhibited dark grey deposits and wear signatures consistent with a short service life. The throttle, mixture, and carburetor heat controls were intact, and their linkages were continuous through to their respective cabin controls.

The airplane was equipped with an MA-4SPA carburetor. Removal and examination of the carburetor revealed that two of the four screws that mounted the carburetor bowl to the throttle body (aft, data tag side) were loose, and although lock-tab washers were installed, the screws could still be turned by hand, and the bowl could be moved. The bowl-to-body contact surface and corresponding area of the bowl gasket were dark in color, and evidence of fluid flow was present on the lower outer surfaces of the bowl.

Maintenance records indicated that the engine was last overhauled in August 2011, about 1,568 flight hours before the accident. The records indicated that the carburetor had been overhauled at that time, and there were no entries indicating any work had been performed on the carburetor in the 7 years leading up to the accident. The last documented maintenance inspection event was an annual inspection on December 19, 2017, 42.2 flight hours before the accident.

Service Bulletin SB-17 dated August 12, 2010, issued by Marvel-Schebler Aircraft Carburetors, LLC., with a subject of, "Body to Bowl Fuel Leaks," directed an inspection of the carburetor every 100 hours of engine operation. The bulletin described reports of loose body-to-bowl joints, with resulting leakage past the body-to-bowl gasket. Compliance required a visual inspection of the carburetor for evidence of movement, with remedial repairs should such evidence be found.

Lycoming Mandatory Service Bulletin SB 366C, dated June 2, 2016, also directed a similar inspection of the carburetor every 50 hours of engine operation.

Maintenance records did not specifically state that SB-17 or SB 366C had ever been performed; however, compliance with service bulletins is not mandatory for aircraft operated under 14 CFR Part 91.