Introduction
A flight operating under a VFR on top IFR clearance encountered a mountain wave condition while flying on a dark moonless night, resulting in a crash into a lake. The accident sequence was captured by radar data, and the subsequent wreckage examination found no evidence of in-flight breakup or preexisting malfunctions.
Accident Sequence
The pilot was flying on a VFR on top IFR clearance when he inadvertently encountered a mountain wave condition. The radar data showed that the airplane began a descent at 612 feet per minute for 1,000 feet. Following the descent, the aircraft abruptly climbed 300 feet before its transponder code disappeared from the sector controller's radar screen. During the entire accident sequence, the pilot did not make any radio transmissions.
The airplane crashed in a vertical nose-down attitude into a lake. Upon impact, the aircraft was buried approximately 20 feet in the muddy silt terrain of the lakebed.
Wreckage Examination
A thorough examination of the wreckage revealed no evidence of an in-flight breakup. Additionally, no preexisting airplane malfunctions or failures were identified. The aircraft appears to have remained structurally intact until impact.
Conclusion
The accident involved a mountain wave encounter during night VFR-on-top operations, with no radio communications from the pilot and a sudden loss of radar contact. The wreckage showed no mechanical or structural issues.