Amateur-built T-51 MUSTANG N551RD accident near Lakeland, Florida

Probable cause

The builder’s use of inadequate material for the exhaust manifold adapters resulting in heat damage and chafing of the crankshaft synchronizer and timing wires that rendered an inoperative ignition system and loss of engine power.

NTSB analysis

During the initial climb, the engine of the amateur built airplane lost all power. Attempts to restore the engine power by the pilot were not successful as he maneuvered the airplane for a forced landing to a field. A postaccident examination of the airplane’s engine compartment revealed that the left and right exhaust manifold adapters were made of inadequate aluminum material. In particular, the right exhaust manifold was found loosely attached to its adaptor by only two bolts (upper) that were not secured with safety wire. The lower two bolts of the adaptor appeared to have completely vibrated loose and each of the four threaded bolt holes were found stripped. The adaptor material had various degrees of thermal damage and erosion which allowed exhaust impingement onto the crankshaft synchronizer and timing wires that were located directly below the damaged manifold adaptor. The wires’ insulation was found heat damaged and chafed leaving the wire conductors exposed. The orientation of the chafing of the exposed wire conductors was in a straight line, nearly perpendicular to the wire’s length and consistent with having contact with the right lower longeron.

Operational testing of the synchronizer and timing sensors system using the airplane’s battery power and the heat damaged synchronizer and timing wires was satisfactory. The engine was then rotated through several rotations using the starter and the ignition system appeared to be operational. With battery power applied, the chafed electrical wires with the exposed conductors were then placed against the right lower longeron and the ignition system became inoperative.

Text from the NTSB. Open the NTSB docket for ERA10LA229 for the full record.