A320 flight crew reported loss of aircraft control during pushback procedure.
Synopsis
A320 flight crew reported loss of aircraft control during pushback procedure.
Narrative
We had no APU so had to start engine at the gate. Proceeded to push back and was informed by ramp crew to set brakes. I set brakes. After about a minute the ramp crew informed me that they were having trouble disconnecting the tow bar and requested I release brakes. I released brakes and the plane moved forward; backward there was a pause and the plane began to move forward again. I hear in a frantic voice 'set brakes; set brakes' I set the brakes and ask what happened and they responded that they tried to disconnect tow bar and the airplane rolled up onto the tow bar. Maintenance came out and I verified with them that the brake light on nose gear was working. Maintenance eventually lowered the tow bar and removed it. They found a new tow bar and towed us back to the gate. On initial contact with tug driver; another person had to step in and talk on the interphone. I feel that there was training involved in the pushback and that lack SOP's and inexperience played a factor in the incident.Suggestions: Make sure that ramp crew follows SOP's; takes there time and know that they can verify brakes are set by the light on nose gear.
Second reporter narrative
Preflight duties for Aircraft X were normal. After briefing the supplemental procedures; we started the left engine at the gate using an external air start unit (APU MEL). The push procedure was normal till after the push was completed and the parking brake was set as directed by the ground crew. Flight crew was notified that the ground crew was unable to disconnect the tow bar; and the Captain was asked to release parking brakes. I forget the wording the ground crew used; but my recollection is that they needed to adjust the tow truck position to be able to disconnect the tow bar. After the parking brake was released; the ground crew moved the aircraft forward and aft a few inches several times. The flight crew did not receive a command to set the parking brake before a grinding noise was heard on the flight deck. Right after the noise was heard; the ground crew repeated 'set parking brake' several times in a frantic voice. The Captain immediately set the parking brake. Flight crew was notified the aircraft had rolled on top of the tow bar and that the tow bar was stuck under the nose gear. Ramp Control and Maintenance were notified of our status. Flight attendants and passengers were briefed several times as information was passed to flight crew from Ramp and Maintenance personnel through the ground intercom. After approximately an hour; the tow bar was dislodged; and the aircraft was successfully towed back to the originating gate where passengers were deplaned.The Captain and First Officer were directed to submit to alcohol and drug tests; which we did.The parking brake light on the nose gear was verified operational during my walk around inspection before the flight.My impression was that the ground crew pushing the aircraft was inexperienced. I base that on the way their communication with the flight deck was conducted. Not directing the parking brake to be set and not verifying the light on the nose gear being illuminated before disconnecting the tow bar were contributing to the event.Suggestions: Having two persons from the ground crew independently verifying the parking brake being set before disconnecting the tow bar would mitigate the risk of this event happening again. It was dark on the ramp and I'm unsure whether ground crew had proper illumination while disconnecting the tow bar. If not; that may have helped mitigate risk as well.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.