Primary finding
Probable cause
The ramp agent misjudging the clearance between the airplane and gpu. A factor was: unavailability of proper ground assistance.
Investigator assessment
Analysis narrative
After starting the no. 2 engine, the captain signalled the ramp agent to disconnect the ground power unit (gpu). The agent signalled the captain the gpu had been disconnected and the captain verified this by observing the 'ext pwr' annunciator light had extinguished and there was no voltage to the external power selector on the voltmeter. After starting the no. 1 engine, the captain signalled the ramp agent he was ready to taxi. The agent gave an all clear signal and directed him to make a hard right turn. As the airplane was pivoting right, the aft portion of the airplane struck the gpu, rupturing the pressure vessel. The captain said the disconnected gpu was not visible from the cockpit.
Source record
Factual narrative
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