On February 29, 1984, an Enstrom 280C (registration N51715) was involved in an aviation accident near Middleton, ID. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During a test flight, an aircraft was seen to rotate 180 degrees about its vertical axis, go nose-low, and descend vertically. Witnesses heard a sputter or tone change. Post-accident inspection found a loose magneto and a puncture in the engine case.
Accident Sequence
The accident occurred while the aircraft was performing a test flight. According to witnesses, the aircraft yawed 180 degrees around its vertical axis, then pitched nose-down and descended vertically to the ground. During this maneuver, witnesses noted a change in engine noise, which they described as either a sputter or a change in tone. The aircraft subsequently struck the terrain.
Post-Accident Inspection
Following the accident, a detailed inspection of the engine was conducted. The magneto was found to be loose; it could be rotated radially about its drive shaft by nearly 60 degrees. Additionally, a puncture was discovered in the engine case directly below the lower swash plate assembly. Except for these two findings, no other discrepancies were identified.