Narrative:

Aircraft at gate in lax, ready for pushback. First officer called lax ground control for pushback clearance. After a few mins, I could see that he was having difficulty getting a response from the controller stating that the frequency was extremely congested. I was communicating with ground personnel to inform them that we were ready for pushback but had not yet received a clearance to do so. The first officer informed me that he was having trouble with controller communications but that we were cleared to push. I then monitored ground control frequency and heard the controller tell him that she had already answered him and to 'stand by.' he insisted that she had cleared us for pushback on his initial contact with her. I asked him to confirm and allowed the ground personnel to begin the pushback. While I was busy communicating with them I did not notice that he was able to verify the clearance as I had requested him to do. Once we were in the alleyway the ground controller informed us that we had not been cleared to push and to return to the gate immediately. I advised the ground personnel to return the aircraft to the gate at once as we were blocking 2 inbound aircraft. At that time the tug apparently ran out of fuel and we were stranded in the alley. I contacted the ground controller and informed her of the situation at which time she became very upset. Another tug was summoned and the aircraft was moved so that both aircraft could pass within about 2-3 mins. I once again requested pushback clearance and was cleared to do so. The ground controller admonished me for not verifying what I understood the clearance to be. Rather than argue with her or try to explain that we had attempted to do so over a badly congested radio frequency, I apologized and followed her instructions. Upon requesting taxi clearance, I was ordered to hold for about 5 mins and finally instructed to taxi to runway 24L via taxiway east. No further exchange with ground control was initiated, we departed normally. I feel this situation was in part caused by over-congestion on the ground control frequency at lax. It was apparent that the controller was under a great deal of stress and perhaps not using completely standard phraseology. The first officer's exuberance to get the aircraft underway on time may have also contributed to the situation. I believe the ground controller could have instructed the first officer upon initial contact to 'hold position.' this would have removed any ambiguity in his mind. There was definitely some confusion as to whether we were cleared to move the aircraft or not, the first officer being convinced that we were. The most important factor, however, was my allowing the aircraft to be moved without being 100% certain of the clearance. I should have made certain the first officer did indeed follow my instruction to verify what he thought the clearance to be before allowing the pushback to continue. Perhaps a discrete pushback frequency on the north side of the lax terminal similar to what is implemented on the south side would have alleviated this problem.

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Original NASA ASRS Text

Title: FREQ CONGESTION AND CLRNC CONFUSION RESULT IN BLOCKED ALLEYWAY AT LAX.

Narrative: ACFT AT GATE IN LAX, READY FOR PUSHBACK. FO CALLED LAX GND CTL FOR PUSHBACK CLRNC. AFTER A FEW MINS, I COULD SEE THAT HE WAS HAVING DIFFICULTY GETTING A RESPONSE FROM THE CTLR STATING THAT THE FREQ WAS EXTREMELY CONGESTED. I WAS COMMUNICATING WITH GND PERSONNEL TO INFORM THEM THAT WE WERE READY FOR PUSHBACK BUT HAD NOT YET RECEIVED A CLRNC TO DO SO. THE FO INFORMED ME THAT HE WAS HAVING TROUBLE WITH CTLR COMS BUT THAT WE WERE CLRED TO PUSH. I THEN MONITORED GND CTL FREQ AND HEARD THE CTLR TELL HIM THAT SHE HAD ALREADY ANSWERED HIM AND TO 'STAND BY.' HE INSISTED THAT SHE HAD CLRED US FOR PUSHBACK ON HIS INITIAL CONTACT WITH HER. I ASKED HIM TO CONFIRM AND ALLOWED THE GND PERSONNEL TO BEGIN THE PUSHBACK. WHILE I WAS BUSY COMMUNICATING WITH THEM I DID NOT NOTICE THAT HE WAS ABLE TO VERIFY THE CLRNC AS I HAD REQUESTED HIM TO DO. ONCE WE WERE IN THE ALLEYWAY THE GND CTLR INFORMED US THAT WE HAD NOT BEEN CLRED TO PUSH AND TO RETURN TO THE GATE IMMEDIATELY. I ADVISED THE GND PERSONNEL TO RETURN THE ACFT TO THE GATE AT ONCE AS WE WERE BLOCKING 2 INBOUND ACFT. AT THAT TIME THE TUG APPARENTLY RAN OUT OF FUEL AND WE WERE STRANDED IN THE ALLEY. I CONTACTED THE GND CTLR AND INFORMED HER OF THE SIT AT WHICH TIME SHE BECAME VERY UPSET. ANOTHER TUG WAS SUMMONED AND THE ACFT WAS MOVED SO THAT BOTH ACFT COULD PASS WITHIN ABOUT 2-3 MINS. I ONCE AGAIN REQUESTED PUSHBACK CLRNC AND WAS CLRED TO DO SO. THE GND CTLR ADMONISHED ME FOR NOT VERIFYING WHAT I UNDERSTOOD THE CLRNC TO BE. RATHER THAN ARGUE WITH HER OR TRY TO EXPLAIN THAT WE HAD ATTEMPTED TO DO SO OVER A BADLY CONGESTED RADIO FREQ, I APOLOGIZED AND FOLLOWED HER INSTRUCTIONS. UPON REQUESTING TAXI CLRNC, I WAS ORDERED TO HOLD FOR ABOUT 5 MINS AND FINALLY INSTRUCTED TO TAXI TO RWY 24L VIA TXWY E. NO FURTHER EXCHANGE WITH GND CTL WAS INITIATED, WE DEPARTED NORMALLY. I FEEL THIS SIT WAS IN PART CAUSED BY OVER-CONGESTION ON THE GND CTL FREQ AT LAX. IT WAS APPARENT THAT THE CTLR WAS UNDER A GREAT DEAL OF STRESS AND PERHAPS NOT USING COMPLETELY STANDARD PHRASEOLOGY. THE FO'S EXUBERANCE TO GET THE ACFT UNDERWAY ON TIME MAY HAVE ALSO CONTRIBUTED TO THE SIT. I BELIEVE THE GND CTLR COULD HAVE INSTRUCTED THE FO UPON INITIAL CONTACT TO 'HOLD POS.' THIS WOULD HAVE REMOVED ANY AMBIGUITY IN HIS MIND. THERE WAS DEFINITELY SOME CONFUSION AS TO WHETHER WE WERE CLRED TO MOVE THE ACFT OR NOT, THE FO BEING CONVINCED THAT WE WERE. THE MOST IMPORTANT FACTOR, HOWEVER, WAS MY ALLOWING THE ACFT TO BE MOVED WITHOUT BEING 100% CERTAIN OF THE CLRNC. I SHOULD HAVE MADE CERTAIN THE FO DID INDEED FOLLOW MY INSTRUCTION TO VERIFY WHAT HE THOUGHT THE CLRNC TO BE BEFORE ALLOWING THE PUSHBACK TO CONTINUE. PERHAPS A DISCRETE PUSHBACK FREQ ON THE N SIDE OF THE LAX TERMINAL SIMILAR TO WHAT IS IMPLEMENTED ON THE S SIDE WOULD HAVE ALLEVIATED THIS PROB.

Data retrieved from NASA's ASRS site as of July 2007 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.