CH147204 Chinook - B - Epilogue

Report / January 18, 2009 / Project number: CH147204 - B Category

Location: Kandahar Airfield, Afghanistan
Date: 18 Jan 2009
Status: Investigation Complete

Aircraft CH147204 was on a training mission out of Kandahar airfield. Subsequent to its departure, an aft rotor fixed droop stop was found on the ramp near where CH147204 was previously parked. A check of other aircraft determined the missing droop stop came from CH147204. Operations advised the occurrence crew of the situation and recalled the aircraft. Using a coalition partner’s emergency shutdown procedure; a ramp was built to minimize aircraft damage, the crew set the parking brakes, secured the flight controls in place and exited the aircraft. After the engines stopped, due to fuel exhaustion, the rotors began slowing down until they eventually impacted the ramp, causing damage to the rotor blade system and fuselage. There were no injuries.

The droop restraint system supports the weight of the rotor blades on startup and shutdown to prevent them from striking the fuselage.

The investigation revealed that the aft fixed droop stops were installed improperly causing metal fatigue of the attachment bolts that resulted in one of the aft fixed droop stops falling off and subsequent damage to the aircraft by the rotor blades on shutdown. Contributing factors were the markings “AFT ROTOR BOTTOM” having been applied to the wrong surface, the difficult visual differences between the large and small chamfers (the two bevelled edges of the droop stop block) and ambiguous technical instructions. The lack of a rotor brake system also contributed to the degree of aircraft damage.

Safety recommendations include the development of CF procedures for droop stop failures applicable to the CH147D Chinook and amendments to the operator’s manual, checklist and technical instructions. A review of the droop stop painting process, and the communication of the results of this investigation with CF coalition partners is also recommended.