Narrative:

This report is submitted in the general or specific safety concern category only. The flight began normally. The push back was being accomplished and engines were being started. The headset that the tug driver used had some static; but was very readable. As we were starting the number one engine; the tug driver stopped the aircraft. I suspected and anticipated that he was about to ask for the parking brake to be set; but there was no communication. Since I was not sure whether he was going to continue the push; I did not set the brake. I called him twice while the number one engine was starting to see if he wanted me to set the brake; but there was no response. Both the first officer and I looked outside to see if the wing walker was giving us the 'apply brakes' hand signal; but the wing walker was not in sight. Shortly thereafter; I saw the tug and tow bar moving away from the nose; and both men were in the tug. I immediately set the parking brake and we continued the flight uneventfully. The aircraft had not moved at all while at idle power; disconnected from the tug; and without the brakes set. There had been no verbal or hand signal communication that the driver wanted me to set the brake; or that the brake was set; and there had been no notification to me that the tow bar had been disconnected; and there was no communication from me to the ground crew to clear them off headset. It is possible that a headset fails during the push; but I doubt that was the case here. It did have some static; but was very readable when we began the push. Ground crews should be more aware of the safety aspects and reasons for procedures and all communications during the push. If the electronic communication fails; hand signals are appropriate to ensure that the brake is set prior to releasing the aircraft from the tow bar. I don't think it is appropriate to disregard the intent of these communications for the sake of convenience.

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Original NASA ASRS Text

Title: A B737 Captain reported that the push back Tug Operator's headset had static but was readable. At some point during the push back he disconnected the headset without saying anything; then disconnected the tug and drove away with no further communications.

Narrative: This report is submitted in the general or specific safety concern category only. The flight began normally. The push back was being accomplished and engines were being started. The headset that the Tug Driver used had some static; but was very readable. As we were starting the number one engine; the Tug Driver stopped the aircraft. I suspected and anticipated that he was about to ask for the parking brake to be set; but there was no communication. Since I was not sure whether he was going to continue the push; I did not set the brake. I called him twice while the number one engine was starting to see if he wanted me to set the brake; but there was no response. Both the First Officer and I looked outside to see if the Wing Walker was giving us the 'apply brakes' hand signal; but the Wing Walker was not in sight. Shortly thereafter; I saw the tug and tow bar moving away from the nose; and both men were in the tug. I immediately set the parking brake and we continued the flight uneventfully. The aircraft had not moved at all while at idle power; disconnected from the tug; and without the brakes set. There had been no verbal or hand signal communication that the driver wanted me to set the brake; or that the brake was set; and there had been no notification to me that the tow bar had been disconnected; and there was no communication from me to the Ground Crew to clear them off headset. It is possible that a headset fails during the push; but I doubt that was the case here. It did have some static; but was very readable when we began the push. Ground Crews should be more aware of the safety aspects and reasons for procedures and all communications during the push. If the electronic communication fails; hand signals are appropriate to ensure that the brake is set prior to releasing the aircraft from the tow bar. I don't think it is appropriate to disregard the intent of these communications for the sake of convenience.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.