Waco UPF 7 N29909 accident near Ocklawaha, Florida

Probable cause

A failure of both magnetos due to multiple deficiencies, which resulted in a total loss of engine power.

NTSB analysis

The commercial pilot stated that, while maneuvering during the local flight, the engine magneto indicator illuminated and one of the engine's magnetos failed, followed shortly after by the other magneto, which resulted in a total loss of engine power. The pilot landed the airplane in a stand of trees before it nosed over, fell 60 ft to the ground, and came to rest on its nose with the tail section in the air; the airplane sustained damage to the top and bottom wings and the firewall.

Postaccident examination of the magnetos revealed that both magnetos had "bad (out of range on impedance)" secondary windings on the coil. The points exhibited a white powder, consistent with the capacitor in the secondary windings of each magneto failing or having failed. Both rotors were cracked, and the pencil springs in both distributor caps were rusted. Damage was also noted to several of the ignition leads (the left magneto had three faulty leads, and the right magneto had one faulty lead). An automotive ignition harness was installed on the magnetos as part of an approved automotive conversion kit; the examination representative indicated that the auto ignition wire has a higher amount of resistance that the magnetos were not designed to handle. Thus, it is likely that some combination of these deficiencies ultimately resulted in the in-flight failure of the magnetos and the subsequent loss of engine power.

Text from the NTSB. Open the NTSB docket for ERA17LA340 for the full record.