Flight Crew Air Transport Pilot (ATP)
Communication Breakdown
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Overcame Equipment Problem
Human Factors; Incorrect / Not Installed / Unavailable Part; MEL
Flight was scheduled to depart on time but ended up being late. As stated in previous write-ups; the aircraft's APU was placarded inoperative due to random non-commanded shutdowns. The parts for repair were ordered. I lost count but either four or five air start carts were brought to the airplane for engine start. Some could not be started and others ran for short periods of time then ceased operating. What I was told was all available air start carts at the airport were now inoperative because of fuel freezing. Unless something else was done the flight probably would have cancelled.I thought I would ask maintenance if a mechanic would come to the airplane for a supervised start of the APU long enough to get an engine running. The mechanic who placarded the APU on the overnight thought it would be okay. He ran the APU for about two hours during overnight maintenance before it shut itself down. He came to the airplane to supervise the start. Thanks to maintenance the engine was started and we went on our way. What I learned later through the flight department and through legal advice from the pilots union that what we did was wrong. We operated the APU while on placard. Both departments highly suggested that a report be filed.
[Report narrative contained no additional information.]
Air carrier flight crew elected to start a placarded component; the APU; in order to start engines. All available ground carts were inoperative due to extreme cold weather.