Date: 202006
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Aircraft: Q400
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Aircraft component: APU
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Communication Breakdown; Troubleshooting; Time Pressure
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Aircraft In Service At Gate
Result: General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Weather; Procedure; Airport; Aircraft
Primary problem: Aircraft

Narrative: I was the Captain on flight XXXX from ZZZ to ZZZ1. We arrived to our airplane at Gate XX. It had been sitting for a few hours and the cabin temperature was 89. So we immediately wanted to get the APU running to begin cooling the airplane. The APU failed twice. It didn't fail to start twice; it flat out failed while it was running; twice. We called Maintenance and they came out and MEL'd the APU. Not a huge deal but we were at a spot that was not authorized to use a PCA (Preconditioned Air unit). The OAT was 85 and the cabin temperature was now 90 and climbing. We were able to get the cabin temperature down a few degrees in the short time we were able to use the APU but it quickly began climbing again once the APU failed for the second time.After Maintenance MEL'd the APU I met with a Ramp Manager and a team captain. I told them that I needed a PCA connected to the airplane before I was going to board passengers. The cabin temperature was now 94 and still climbing. I told the Ramp Manager that I was not comfortable only flash cooling the airplane. Experience has shown me that we need a constant flow of cool air while passengers are onboard so anything short of that was not going to be acceptable (I've seen the cabin temperature rise 15 [degrees] in 5 min between disconnecting the PCA to the time we started engines). We discussed the situation and came up with these two options.[Our first option would be to] flash cool the airplane (putting the PCA hose physically inside the airplane) then board passengers once the cabin is at an appropriate temperature. Cabin temperature [would] come down relatively quickly. [However the] hose has to be pulled once passengers begin to board which means no cool air coming into the airplane which means cabin temperature rapidly rising to an unsafe temperature before being able to start the engines (given the current conditions). [Or we could] swap airplanes.Ultimately we ended up with a hybrid of both options. ZZZ did not approve us to use a PCA at Spot XX so it was decided that we would tow the airplane from Spot XX to Spot XY which was a spot approved for a PCA. While the ramp [agents] were waiting to tow the airplane; the Ramp Manager flash cooled the airplane and then towed the airplane but even after that the cabin was still 82. Once it was towed into Spot XY. We were able to get the PCA hooked up and brought the cabin temperature down to a safe level before boarding passengers. We departed ZZZ with no further issues.We need to do better. While I was able to effectively work with Station Management to work through the situation; this could have been avoided. We need to work with ZZZ to get approval to use a PCA; upon request; at all spots; not just the currently approved spots. ZZZ claims that the PCA is too close to the service road. We need to come up with an alternate placement of the PCA so we can properly cool the airplane in situations like this. Ideally; we could put the PCA where the fuel truck parks but would obviously need to wait till fueling is complete. I understand this might not always be ideal but we also don't have this problem frequently. If we need to shorten the hoses on the PCA's to accommodate this for PCA placement then that's what needs to be done. This situation also could have been avoided had we been able to swap to a new airplane. We discovered this issue well outside an hour prior to departure. We released the brake 1 hour and 20 minutes passed our scheduled departure time. 3 hours to remedy an inoperative APU is absurd. The unfortunate part about this whole thing is this simple issue ended up cascading into the next day. We were on a min rest overnight so we had to schedule a new show time for the next day ultimately causing a STAR flight to depart late and cause passengers to miss connections. All because of an inoperative APU.




Synopsis: Air carrier Captain reported APU failures to cool aircraft and other procedural obstacles to cool aircraft before boarding.