Hughes 500D N134SH accident near Delta Junction, Alaska

Probable cause

A total loss of engine power for undetermined reasons, which necessitated an emergency hovering autorotation, during which the helicopter impacted trees and terrain.

NTSB analysis

The pilot was transporting sections of water hose to a remote site via a 100-ft-long external load line that was attached to the helicopter’s belly-mounted cargo hook. While the helicopter was hovering about 100 ft over the intended site and about 5 to 10 ft above trees while facing into a hill, the engine lost all power. The pilot then initiated an emergency hovering autorotation and turned the helicopter left in an attempt to face it downhill. Subsequently, the helicopter settled into trees, during which the main rotor blades impacted several of them, followed by it impacting terrain hard and rolling onto its right side, which resulted in substantial damage to the main rotor drive system, tailboom, and fuselage.

During a postaccident examination, about 60 lbs of fuel were drained from the helicopter’s fuel cell; thus, fuel exhaustion did not cause the loss of power. During an engine test-run, the engine produced full-rated power at various power settings. Postaccident examination of the helicopter revealed no preaccident mechanical malfunctions or failures that would have precluded normal operation. Based on the available information, the reason for the loss of engine power could not be determined.

Text from the NTSB. Open the NTSB docket for ANC13LA074 for the full record.