Amateur-built Stewart N551X accident near Ocala, Florida

Probable cause

A loss of engine power due to contamination and clogging of the fuel system by a post-assembly fuel tank sealant.

NTSB analysis

About 6 years before the accident, the owner/pilot purchased the disassembled experimental amateur-built airplane from its builder, who had flown the airplane on multiple occasions. The pilot reassembled the airplane, and spent several months attempting to resolve fuel leaks in the airplane's integral wing tanks. Subsequent to the pilot's use of a slosh sealant in the fuel tanks, the engine lost power during two separate high-speed taxi tests, due to clogged fuel screens. The day prior to the accident, the pilot conducted his first flight in the airplane, which lasted about 18 minutes. During his second flight in the airplane, the pilot was fatally injured when the airplane impacted trees and terrain about 11 miles from his home airport, and a post-crash fire ensued. Many witnesses reported that the airplane was low, and that the engine sounded unusual. Five witnesses reported that the engine had stopped. Several witnesses reported that the airplane banked sharply in order to avoid a 500-foot-tall cell phone tower located about 500 feet from the impact location. Airplane assembly guidance specified the use of a commercial sealant called "Pro-Seal" during fuel tank assembly, but did not specify or prohibit the use of a slosh sealant, which was intended to be used after assembly. The technical information for the slosh sealant that was found in the pilot's hangar stated that the condition and cleanliness of the surface can affect sealant adhesion. Examination of the wreckage revealed that the interior surfaces of the wing bays that were used to contain fuel exhibited a charred brown/black material consistent with a fire-damaged internal tank coating. One in-tank fuel pickup finger screen was partially occluded by the material, but the pre-accident condition of the finger screen could not be determined.

Text from the NTSB. Open the NTSB docket for ERA09LA184 for the full record.