Amateur-built THUNDER MUSTANG N695HR accident near Spanish Springs, Nevada

Probable cause

A complete loss of engine power during climb for reasons that could not be determined due to the severity of postcrash fire damage to the airplane.

NTSB analysis

The builder/owner/pilot completed the kit-built composite airplane in 2011 and had flown it about 178 hours. The day before the accident, he made an uneventful flight from his home airport to another airport; the following morning, he and his passenger departed on a long cross-country flight. The pilot reported that the takeoff and initial climbout were normal, but as the airplane was climbing through an altitude of about 10,000 feet, the engine lost power suddenly and completely. The pilot described the engine failure as "immediate," without a gradual onset, or any prior symptoms. Although the propeller continued to windmill after the loss of power, the pilot was unable to effect a successful re-start and conducted a forced landing on a two-lane road. During the landing rollout, the airplane impacted a truck and a highway sign, resulting in substantial damage to the airplane, and a postaccident fire consumed a significant portion of the airplane. Although the airplane was equipped with multiple electronic devices, including two electronic engine control units (ECUs), that recorded data about the operation of the engine and airplane, fire damage precluded the recovery of any of that data.

The custom V-12 engine was based on an automotive design and relied on the twin ECUs to control fuel injection and ignition. Each ECU was dedicated to a separate cylinder bank, and each was powered by an independent electrical system. As a result of this system architecture, the engine was completely dependent on electrical power to and proper functioning of both ECUs for normal operation. Loss of one ECU would have resulted in the engine running in a degraded mode on one bank of cylinders.

The continued windmilling of the propeller subsequent to the power loss indicated that the engine maintained its mechanical integrity. This was confirmed by postaccident examination of the engine, which did not reveal evidence of any malfunctions or failures that would have resulted in the power loss. The lack of evidence of a mechanical failure combined with the rapidity and finality of the power loss suggested an underlying electrical problem or event that simultaneously disabled both ECUs. However, the damage to the airplane and destruction of electronic data due to the fire, precluded determination of the reason(s) for the engine power loss.

Text from the NTSB. Open the NTSB docket for WPR14LA312 for the full record.