APU MALFUNCTION RESULTING IN FIRE WARNING AND REPLANNING FLT TO DESTINATION AT A LOWER ALT.

Narrative

SOP CALLS FOR APU SHUTDOWN PRIOR TO TKOF; WAS COVERED IN PRETKOF CHKLIST; APPEARED ACCOMPLISHED. HOT AIR SMELL; ELEVATED APU EGT (CA 330 DEG C) AND FIRE WARNING LIGHT/BELL DURING CLB INDICATING APU MIGHT NOT HAVE SHUT DOWN NORMALLY; AS INDICATED BY ZERO VOLTS/FREQ ON APU GENERATOR; APU FUEL VALVE LIGHT OUT; APU EGT DROPPING. S/O ACCOMPLISHED EMER SHUTDOWN BY PULLING FIRE SHUT OFF; DID NOT DISCHARGE FREON FOR FEAR OF FURTHER CABIN AIR CONTAMINATION; EVEN THOUGH AGENT DISCHARGE IS REQUIRED IN PROC. FLT CONTINUED AT LOWER THAN PLANNED ALT. AFTER ODOR/SMOKE CLRED; AND APU EGT HAD DROPPED IMMEDIATELY. CONCLUSION: EVEN THOUGH AGREEING NOT TO DISCHARGE AGENT IMMEDIATELY; I FEEL NOW IT SHOULD HAVE BEEN DONE TO ASSURE IMMEDIATE COOLING IN POTENTIALLY HOT AREAS NOT INDICATED BY APU EGT TEMP GAUGE. WOULD LIKE TO SEE SOP REQUIRING NOT JUST EGT DROP TO VERIFY SHUTDOWN PRIOR TO TKOF; BUT A DEFINITIVE ESTABLISHED EGT VALUE INDICATED TO ASSURE APU SHUTDOWN PRIOR TO TKOF. SPECIFY IN APU FIRE PROC THAT APPLIED STEPS ARE SAME FOR AIRBORNE WARNING; IF FOUND TO BE APPROPRIATE; OR AT LEAST ADD NOTE AS TO DIFFERENCE IN PROC IF AIRBORNE WARNING OCCURRED; IF DEEMED NECESSARY. NOTE: ON ARR AT DEST APU FOUND COMPLETELY OUT OF OIL. NO OIL QTY OR PRESS INDICATION IN COCKPIT. AN AUTO-SHUTDOWN IS PROVIDED FOR LOW OIL PRESS; AS IS AUTO-SHUTDOWN FOR FIRE IF ARMED (ON GND). NOT SURE IF PROVIDED WHEN AIRBORNE. SUPPLEMENTAL INFO FROM ACN 85564. PRIOR TO TKOF AT ORD THE APU SHUT DOWN WITH ACCOMPANYING APU EGT DROP AND ZERO VOLTS AND FREQ ON THE APU. CALLBACK CONVERSATION WITH RPTR REVEALED FOLLOWING. DISCUSSED WITH MGMNT AND NO MENTION WAS MADE AT THE HEARING OF LOW OIL QTY. CONVINCED MGMNT FEELS APU WAS NOT SHUT DOWN PRIOR TO TKOF. RPTR HAS COMPLETE CONFIDENCE IN THE S/O AND THAT SOP PROC WERE COMPLIED WITH. FEELS AS A RESULT OF THE LOW OIL; SYSTEMS IN THE CIRCUITRY WERE ACTIVATED THAT PREVENTED THE FUEL VALVE FROM CLOSING RESULTING IN THE APU TO CONTINUE RUNNING AT IDLE. APU OPERATED NORMALLY DURING THE GND STOP AND GAVE NO INDICATION OF MALFUNCTION. SURE THAT MAINT FAILED TO SVC THE OIL SYS DURING THE WALK-AROUND INSPECTION.