What happened
Three months prior to the accident, a mechanic performed repairs on the left magneto of the aircraft. Upon reinstallation, the mechanic timed the left unit with the right magneto. Following the incident, examination of the components revealed that both magnetos had been set to advanced timing positions. Internal inspection further identified discrepancies within the units that would likely lead to electrical breakdown.
After takeoff, the engine experienced a backfire. The pilot in command attempted what appeared to be a backup autorotation maneuver intended for a run-on landing. Examination of the crash site indicated that while the vertical descent was arrested upon touchdown, forward velocity was not sufficiently reduced. Following initial contact, the helicopter slid through a ditch. A collision with the far side of the ditch generated fatal impact forces transmitted to the pilot in command.
The investigation
Mechanical analysis focused on the ignition system and the dynamics of the crash sequence. Investigators found that the magnetos were improperly timed, contributing to engine malfunction. The crash site examination confirmed that the pilot successfully arrested vertical descent but failed to dissipate forward momentum before striking the ditch's far side.
Findings
The primary factors included improper maintenance of the ignition system and the inability to control forward speed during a forced landing. The electrical breakdown caused by advanced timing led to engine failure, while the subsequent impact with the ditch structure proved fatal.