Date: 201702
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Daylight
Aircraft: Regional Jet 700 ER/LR (CRJ700)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb; Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: APU
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Workload; Troubleshooting; Confusion; Situational Awareness; Communication Breakdown
Anomaly: Aircraft Equipment Problem Less Severe; Deviation - Speed All Types; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action; General Maintenance Action
Contributing factors: Procedure; Aircraft; Company Policy
Primary problem: Aircraft

Narrative: We got an aircraft with a MEL 49-10-XX...'APU door position unknown' with airspeed restricted to 220 kts. We called Maintenance to advise that the door was closed and asked if the deferral could be changed to 49-10-XY to remove the 220 kts restriction. MTC advised that the door could open in flight and that due to the history of the aircraft the MEL could not be changed. After checking 10-07 pages to verify that our next destination had a 'huffer/puffer'; we flew to it uneventfully.We were filed the next leg at FL 270. On climb out just before FL180; Pilot Flying (PF) noticed that in a 220 KIAS climb; the Stall Margin Indicator (Green line) started getting uncomfortably close to the 'speed bucket'. Crew soon realized that 220 KIAS was not a wise choice for climb speed to; and cruise speed at FL270. (Holding speed at FL270; for example; is not less than 250 kts.)Captain and First Officer (FO) discussed a plan of action. Captain suggested that the APU door coming open and damaging the APU was a far more desirable than potentially operating the aircraft close to stall or even stalling the aircraft...FO agreed. We considered maintaining 220kts at a lower altitude; but decided that fuel burn could be a factor.We [set ACARS message to] MTC to advise them what we were doing and that we would generate a write upon arrival. We flew at our normal cruise speed; constantly monitoring any unusual APU door indications. I admit that I knowingly exceeded a MEL limitation. As Pilot in Command (PIC); I had a decision to make and decided that I could exceed the 220kts MEL limitation without jeopardizing passenger safety. In deciding between human life and property damage; I will pick the safety of human life.If I destroy an APU while safely transporting a plane full of passengers...I can accept that. I understand that the people paying for the APU might not be happy about it.The APU door could have blown open and the APU could have been damaged.I should have realized that a 220KIAS at FL270 on a 800+ mile flight was not a good idea. I should have realized that 220 KIAS was way too low a cruise speed at FL270.My decision making was 'fogged' by the fact that we had just flown the aircraft at 11;000 feet with no problem. Then again doing 220 KIAS at 11;000 is not difficult.




Synopsis: CRJ-700 Captain reported being dispatched with and APU DOOR POSITION UNKNOWN MEL and a 220 KT speed restriction. At FL270 the stall margin decreased greatly causing the Captain to fly at normal cruise speed for safety of flight even though the APU may sustain damage.