What happened
The pilot was attempting to land a Hughes 260B helicopter when they encountered dust and reduced visibility at the landing site. The pilot decided to abort the landing and began a climbout. While flying at approximately 140 feet above the ground and at a speed of 50-60 mph, the engine experienced a rapid loss of power.
The pilot attempted an autorotation landing; however, the airspeed and altitude conditions during the maneuver were slightly outside the limitations specified by the height-velocity diagram. This resulted in a hard landing.
The investigation
Post-crash examination of the engine identified that the #1 cylinder fuel injector line had separated approximately one inch outboard of the injector unit. Metallurgical analysis determined this separation was caused by fatigue. Engine logs indicated that this was the second instance of a #1 cylinder fuel injector line separation in recent history.
Further inspection revealed that three hold down bolts for the #3 cylinder had also separated due to fatigue. Investigators noted that the flange for the #3 cylinder was coated with primer paint measuring between 0.0014 inch and 0.0028 inch in thickness. This exceeded the maximum allowable thickness of 0.0005 inch specified in Textron Lyंत्रिकी Service Bulletin 271A.
Both cylinder hold down plates exhibited evidence of fretting and rubbing damage. Engine records showed the engine underwent a major overhaul on July 8, 1994, during which the engine was painted while assembled and delivered to Cascade Airframe Repair. While the #3 cylinder was later removed and honed, the specific date when the flange was painted could not be determined.