Narrative:

We were on a visibility approach for psp, runway 30, right downwind, descending through 6000' and 210 KTS when I (copilot) activated the APU (final item on descent checklist). The light off on the start seemed to have a normal temperature acceleration momentarily, then the gauge pegged to 730 degrees C, a hot start, but within starting limits. A low oil pressure light was also initially observed momentarily, however it extinguished after a second. 2 or 3 seconds after the RPM and temperature of the APU had stabilized we got an APU fire light and bell. I then proceeded with our emergency drill for APU fire, by shutting off the APU and pressing the APU fire extinguisher switch. The fire light went out. We then proceeded with the abnormal checklist and completed that on final approach. The captain called the tower for fire trucks to standby and notified the F/a's of our problem. After T/D the fire trucks observed the aircraft externally and reported no fire or smoke visible from the tail. After the passenger were deboarded, the mechanics determined the likely cause of the fire was a fuel line leak.

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Original NASA ASRS Text

Title: EMERGENCY IN FLT, APU STARTUP ON APCH (CHECKLIST ITEM), OVER TEMPERATURE, THEN FIRE LIGHT AND WARNING BELL.

Narrative: WE WERE ON A VIS APCH FOR PSP, RWY 30, RIGHT DOWNWIND, DSNDING THROUGH 6000' AND 210 KTS WHEN I (COPLT) ACTIVATED THE APU (FINAL ITEM ON DSCNT CHKLIST). THE LIGHT OFF ON THE START SEEMED TO HAVE A NORMAL TEMP ACCELERATION MOMENTARILY, THEN THE GAUGE PEGGED TO 730 DEGS C, A HOT START, BUT WITHIN STARTING LIMITS. A LOW OIL PRESSURE LIGHT WAS ALSO INITIALLY OBSERVED MOMENTARILY, HOWEVER IT EXTINGUISHED AFTER A SECOND. 2 OR 3 SECS AFTER THE RPM AND TEMP OF THE APU HAD STABILIZED WE GOT AN APU FIRE LIGHT AND BELL. I THEN PROCEEDED WITH OUR EMER DRILL FOR APU FIRE, BY SHUTTING OFF THE APU AND PRESSING THE APU FIRE EXTINGUISHER SWITCH. THE FIRE LIGHT WENT OUT. WE THEN PROCEEDED WITH THE ABNORMAL CHKLIST AND COMPLETED THAT ON FINAL APCH. THE CAPT CALLED THE TWR FOR FIRE TRUCKS TO STANDBY AND NOTIFIED THE F/A'S OF OUR PROB. AFTER T/D THE FIRE TRUCKS OBSERVED THE ACFT EXTERNALLY AND RPTED NO FIRE OR SMOKE VISIBLE FROM THE TAIL. AFTER THE PAX WERE DEBOARDED, THE MECHS DETERMINED THE LIKELY CAUSE OF THE FIRE WAS A FUEL LINE LEAK.

Data retrieved from NASA's ASRS site as of August 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.