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An medium large transport on a test flight in cruise at FL350 declared an emergency and diverted due to an APU fire warning caused by an improperly installed APU exhaust tailpipe.
| Attributes | |
| ACN | 404398 |
| Time | |
| Date | 199806 |
| Day | Mon |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : zzz |
| State Reference | US |
| Altitude | msl bound lower : 35000 msl bound upper : 35000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zzz |
| Operator | general aviation : corporate |
| Make Model Name | Any Unknown or Unlisted Aircraft Manufacturer |
| Operating Under FAR Part | Part 91 |
| Navigation In Use | Other Other |
| Flight Phase | cruise other other other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | Other |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 75 flight time total : 8000 flight time type : 50 |
| ASRS Report | 404398 |
| Person 2 | |
| Affiliation | Other |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : commercial |
| Events | |
| Anomaly | aircraft equipment problem : critical non adherence : far non adherence : published procedure other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | flight crew : declared emergency other |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
Narrative:
This was a routine production test flight, originating at manufacturer's ZZZ facility. An APU start at cruise altitude is standard practice. At FL350, in medium large transport, after a failed APU start, APU fire indication occurred. Fire handle was pulled, indication ceased immediately, extinguisher bottle was discharged per non-normal checklist. No other evidence of fire existed. We flew the aircraft to home base, approximately 45 mins away. We declared an emergency but the return was uneventful. Callback conversation with reporter revealed the following information: the reporter stated the cause of the APU fire warning was an APU tailpipe mismatch with the APU exhaust port allowing hot exhaust gas to escape around the heat shield, triggering the fire warning loop. The reporter said, while no evidence of fire was present, the exhaust gas is very hot and could cause damage. The reporter stated the APU fire warning system tested ok and the APU was used for engine start with no fire warning.
Original NASA ASRS Text
Title: AN MLG ON A TEST FLT IN CRUISE AT FL350 DECLARED AN EMER AND DIVERTED DUE TO AN APU FIRE WARNING CAUSED BY AN IMPROPERLY INSTALLED APU EXHAUST TAILPIPE.
Narrative: THIS WAS A ROUTINE PRODUCTION TEST FLT, ORIGINATING AT MANUFACTURER'S ZZZ FACILITY. AN APU START AT CRUISE ALT IS STANDARD PRACTICE. AT FL350, IN MLG, AFTER A FAILED APU START, APU FIRE INDICATION OCCURRED. FIRE HANDLE WAS PULLED, INDICATION CEASED IMMEDIATELY, EXTINGUISHER BOTTLE WAS DISCHARGED PER NON-NORMAL CHKLIST. NO OTHER EVIDENCE OF FIRE EXISTED. WE FLEW THE ACFT TO HOME BASE, APPROX 45 MINS AWAY. WE DECLARED AN EMER BUT THE RETURN WAS UNEVENTFUL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE CAUSE OF THE APU FIRE WARNING WAS AN APU TAILPIPE MISMATCH WITH THE APU EXHAUST PORT ALLOWING HOT EXHAUST GAS TO ESCAPE AROUND THE HEAT SHIELD, TRIGGERING THE FIRE WARNING LOOP. THE RPTR SAID, WHILE NO EVIDENCE OF FIRE WAS PRESENT, THE EXHAUST GAS IS VERY HOT AND COULD CAUSE DAMAGE. THE RPTR STATED THE APU FIRE WARNING SYS TESTED OK AND THE APU WAS USED FOR ENG START WITH NO FIRE WARNING.
Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.