A First Officer reports they departed with their CRJ-200 APU deferred due to the Electronic Control Unit (ECU) was completely fried. Upon landing APU Inlet door was found in the open position. Maintenance raised concerns about the fuselage structural integrity at the Inlet door area and APU Turbine windspeed exceeding 300 knots. Aircraft flew at approximately 330 knots.
Synopsis
A First Officer reports they departed with their CRJ-200 APU deferred due to the Electronic Control Unit (ECU) was completely fried. Upon landing APU Inlet door was found in the open position. Maintenance raised concerns about the fuselage structural integrity at the Inlet door area and APU Turbine windspeed exceeding 300 knots. Aircraft flew at approximately 330 knots.
Narrative
While at the gate; with passengers loaded and APU running; we received a R PACK OVERTEMP caution. We disabled the pack and called for Maintenance. Shortly before Maintenance showed up; the APU shut down. After several minutes the Mechanics stated that the APU's Electronic Control Unit (ECU) was completely fried; and they were going to defer it. I believe the Mechanic stated he was going to wire the door shut. The Mechanics returned shortly; and informed us the APU was deferred and we were good to go. After getting a new release; we flew to our destination.After landing late; we informed the next crew of what had happened in ZZZ. The next First Officer noticed on his walkaround that the APU door was now open. Maintenance did not know if the door was secured before leaving ZZZ; so they were concerned about the airplane's structural integrity.We should have completed a walkaround after Maintenance performed their deferral; but due to time pressure; and the fact that the only thing that had changed was the APU door; we left as soon as we could; without a walkaround. The MEL procedures for flight crew with an APU deferral does not state to verify the door is closed; but possibly should.
NASA callback
Reporter stated the APU Inlet door opens and raises up into the airstream on the aft left fuselage above the left engine. The MEL Maintenance action procedures requires the APU Inlet door be Safety wired in the door closed position. But after the next First Officer noticed the APU door was actually open during his Walk around; no one was certain if the APU door was ever wired closed.Reporter stated that Mechanics in ZZZ were not sure if the Electronic Control Unit (ECU) had become super hot from an Air Conditioning duct leaking hot air in the Aft Equipment Bay onto the ECU; or an electrical short within the ECU had caused the Unit to fry.Reporter stated their Mechanics concern for structural damage to the CRJ-200's fuselage and APU itself was based on the APU Inlet door was not suppose to open; or be open; above 280 Knots. Also the APU Turbine windspeed was limited to approximately 300 Knots. They were flying at 330 Knots.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.