Date: 201511
Local time of day: 1801-2400
Location: LAX.Airport, CA
Flight conditions: VMC
Light: Night
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ground LAX
Aircraft component: APU Pneumatic System & Ducting
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Confusion
Second reporter function: Pilot Not Flying; Captain
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Dispatch
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Aircraft; Human Factors
Primary problem: Aircraft

Narrative: Day three of a three day trip. First flight of day for crew. We pushed back from gate in LAX. Planned on starting both engines. During first engine start (#2 engine) noticed that N2 rotation slower than normal; APU bleed supply was fluctuating after start valve opening. Engine 2 did start; however during engine 1 start same issue with bleed supply. N2 never accelerated past 5%. Elected to abort engine start. At this point; push back crew was ready to disconnect; we were in the alleyway. Captain called MX Control to discuss issue; while I informed ramp of our maintenance situation. There was one outbound aircraft behind us in the alley that we were blocking as well as two inbound aircraft waiting to enter alleyway. Maintenance informed Captain that they wanted us to return to gate. I called Operations to update them of our situation and that we would need to return to a gate. Ops responded that they would work on it. While I was on the operations frequency; maintenance asked me if we had attempted a crossbleed start. Since if we returned to gate most likely the outcome would be an APU bleed deferral and we would have to do a crossbleed start anyway. I responded that no; we had not due to congestion in alley but that I would mention it to Captain. Captain and I decided to have ground crew disconnect from aircraft and we would single engine taxi out of alleyway (aircraft weight was approximately 151.0) so as not to block traffic any longer and this would give us time to evaluate situation away from alleyway. Contacted ground for taxi - ATC issued instructions to taxi B; C3; C; hold short of C4. Advanced power to taxi; however it felt as if we in a rut and could not get aircraft to move. Cancelled taxi clearance with ground; called ramp; and called operations to request a tug crew to move us from depression in asphalt. Tug crew came out and moved aircraft approximately five feet forward. After ground crew disconnected; called LAX Ground again and received same taxi instructions as earlier. During taxi; I asked Captain if he had gotten an opportunity to make a PA to the passengers to keep them informed; and he answered in the affirmative. Arrived at C holding short of C4. After crew discussion and notification to ATC ground; we elected to do a crossbleed start of #2 engine. Our reasoning was partly to troubleshoot issue: maintenance was inclined to think issue was due to APU bleed; as well as since planning to return to gate our preference was to have both engines operating to reduce jetblast potential during parking.Complied with FM procedure and accomplished successful crossbleed start. Per FOM Captain contacted MX Control again to discuss further action. At this point; Maintenance felt that it was the APU bleed and that since both engines were operating normally we were good to proceed with flight. I had several issues that I communicated to Captain: 1) Since we had a known defect prior to dispatch release (takeoff roll) my FOM understanding was that we needed to enter a maintenance log write up 2) I wanted to make sure that Dispatch had been informed and was in agreement3) If APU pneumatics are deferred; does the destination City Operations have equipment for us to do an airstart. The Captain listened to my concerns and specifically asked MX Control what our maintenance status was. The response was that as far as he was concerned we were 'Good to Go' and to make a log book entry enroute. He also stated that he was checking with destination Operations to be sure that they are equipped to handle us and that he was speaking to Dispatch as well. Despite my feeling that this didn't seem correct; I thought perhaps that this was unique to this fleet versus the procedures that I was more familiar with. After further discussion with Captain and noting fuel on board (we had approximately 15.3; planned fuel at gate 15.7); we felt that it was safe to proceed with flight and that all procedures had been complied with. About 10 minutes after takeoff; ATC notified us to call company. Operations was surprised that we were airborne; as apparently it had not been communicated to them. Dispatch sent us an ACARS message indicating that he felt that maintenance should have made the deferral prior to departure and suggested filing a report.


Second narrative: [Report narrative contained no additional information.]


Synopsis: B737 flight crew experienced difficulty starting the second engine after pushback due to fluctuating APU bleed air pressure. Local maintenance advised the crew to use a crossbleed start and write the APU up enroute. After takeoff the crew was asked to contact Dispatch and was informed that the APU should have been deferred prior to takeoff.