On January 12, 1995, a Hughes 269C (registration N796) was involved in an aviation accident near Dumont, TX. Investigators recorded the probable cause as: THE LOSS OF ENGINE POWER DUE TO OVERSTRESS FRACTURES OF THE #3 CYLINDER CONNECTING ROD CAP BOLTS. THE ORIGIN OF THE FRACTURES COULD NOT BE DETERMINED. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter experienced catastrophic engine failure at 40 feet during wildlife control activities. The pilot attempted to regain power but the helicopter impacted ground, bounced 13 feet forward, and rolled right.
Incident Overview
During wildlife control operations, a helicopter experienced a catastrophic engine failure at an altitude of 40 feet above ground level. The pilot attempted to regain engine power by performing a technique described as "milking the collective." Subsequently, the helicopter impacted the ground in a level attitude without flaring. Following the initial impact, the helicopter bounced 13 feet forward and rolled onto its right side.
Engine Examination
A detailed examination of the engine revealed that the #3 cylinder connecting rod cap bolts had fractured, resulting in a catastrophic failure of the bearing cap and piston. The safety board conducted a metallurgical examination of the fractured bolts.
Metallurgical Findings
The metallurgical examination indicated that the fracture features at the center of each bolt were the result of overstress separations. However, the fracture features adjacent to the outside diameter of each bolt contained mechanical damage that obliterated the original fracture features.