Large Transport; Low Wing; 2 Turbojet Eng
Flight Crew Last 90 Days 140; Flight Crew Total 16000; Flight Crew Type 5865
Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Other / Unknown
Airport; Procedure
From the gate; our flight was cleared to push into the alley; with clearance to disconnect at the 'North' Spot. This is the alley between Terminals 7 and 8. The Tug Driver stopped us on the marked centerline and disconnected. The pushback was performed with proper communication verbiage and per SOP. We started both engines; anticipating the need for both engines at idle thrust to begin our taxi from the North spot.After taxi clearance was received from Ramp Control; the Captain released the parking brake and was unable to make the aircraft move under its own power at 40% N1 on both engines. Thinking that perhaps the brakes had not released properly; the Captain cycled the brake handle; but still was not able to get the aircraft to move forward at the breakaway thrust of 40% N1. The aircraft was definitely settled into a rut at the North spot. We coordinated with Ramp Control via radio to verify that there was no equipment or personnel congested behind the aircraft. We coordinated with Ramp Control the use of engine thrust above Breakaway (40% N1); while referencing guidance in Flight Manual. It took 52% N1 on both engines to get the aircraft to roll forward out of the rut. The remainder of our taxi and flight was uneventful. Just as the tug finished pushing us into our final position at the North spot it felt like the tug's driver made an abrupt stop. The jolt was noticeable throughout the cabin.  We now realize that what must have occurred was the aircraft settling into the rut in the asphalt just as the slack on the towbar pulled against the tug. I believe this hazard needs to be repaired and corrected. I recommend a repair to the rut; but in the short term I recommend advising the push crews to stop the pushback at a spot several feet prior to the rut; so as to avoid the problems we had.
An air carrier aircraft was pushed back from LAX to the North Spot where its main gear tires settled into a rut which then required 52% N1 to break away for taxi.