Narrative:

APU operating stable with egt 650 degrees C. Pilot's afm states egt 630 degrees C is maximum operating APU egt. It was written up after arriving at the gate. The captain went to get paperwork for the next flight. Upon return; maintenance had cleared the write-up stating; observed within limits of operating range; returned to service. I looked at the egt -- again it was operating at 650 degrees C -- so I wrote it up again. The maintenance technician came out with the maintenance page in his hand to show me the MD80 APU operating limits; and repeated the maintenance clearing of the item. I told him our operating limit out of the afm was 630 degrees C; and he stated 'I don't care what your manual says; you can take the airplane as is; or refuse it;' upon which I called maintenance control and told them I would not take the airplane in the present condition. 2 points: 1) the maintenance manual is being interpreted to mean the APU can operate between 630-663 degrees C forever. If you look at the maintenance logbook; you will find the write-ups say the APU is operating normally between the allowed 630-650 degrees C. 2) the pilot manual limits APU stable operation to 630 degrees C. Which is it? There is no procedure for pilots to operate the APU above 630 degrees C. We're not troubleshooters. After considering the matter for 45 mins; maintenance MEL'ed the aircraft. 1) change the pilot afm. 2) change the maintenance interpretation of their chart. 3) there's a similar situation with an engine start. Pilots use 475 degrees maximum; maintenance uses 500 degrees maximum. Since that's not in our afm; I can't remember what to do other than keep writing it up; just like I did with the APU. 4) install an idiot light so pilots shut down the APU on the ground with red light on. This will take us out of the equation; and maintenance can adjust the light to come on where they set the temperature.

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Original NASA ASRS Text

Title: AN MD80 CAPT RPTS DIFFERENT APU OPERATING LIMITS IN FLT MANUAL AND MAINT MANUAL. FLT MANUAL 630 DEGS MAX LIMIT. MAINT MANUAL LIMIT 663 DES. CAUSES CONFLICT.

Narrative: APU OPERATING STABLE WITH EGT 650 DEGS C. PLT'S AFM STATES EGT 630 DEGS C IS MAX OPERATING APU EGT. IT WAS WRITTEN UP AFTER ARRIVING AT THE GATE. THE CAPT WENT TO GET PAPERWORK FOR THE NEXT FLT. UPON RETURN; MAINT HAD CLRED THE WRITE-UP STATING; OBSERVED WITHIN LIMITS OF OPERATING RANGE; RETURNED TO SVC. I LOOKED AT THE EGT -- AGAIN IT WAS OPERATING AT 650 DEGS C -- SO I WROTE IT UP AGAIN. THE MAINT TECHNICIAN CAME OUT WITH THE MAINT PAGE IN HIS HAND TO SHOW ME THE MD80 APU OPERATING LIMITS; AND REPEATED THE MAINT CLRING OF THE ITEM. I TOLD HIM OUR OPERATING LIMIT OUT OF THE AFM WAS 630 DEGS C; AND HE STATED 'I DON'T CARE WHAT YOUR MANUAL SAYS; YOU CAN TAKE THE AIRPLANE AS IS; OR REFUSE IT;' UPON WHICH I CALLED MAINT CTL AND TOLD THEM I WOULD NOT TAKE THE AIRPLANE IN THE PRESENT CONDITION. 2 POINTS: 1) THE MAINT MANUAL IS BEING INTERPED TO MEAN THE APU CAN OPERATE BTWN 630-663 DEGS C FOREVER. IF YOU LOOK AT THE MAINT LOGBOOK; YOU WILL FIND THE WRITE-UPS SAY THE APU IS OPERATING NORMALLY BTWN THE ALLOWED 630-650 DEGS C. 2) THE PLT MANUAL LIMITS APU STABLE OP TO 630 DEGS C. WHICH IS IT? THERE IS NO PROC FOR PLTS TO OPERATE THE APU ABOVE 630 DEGS C. WE'RE NOT TROUBLESHOOTERS. AFTER CONSIDERING THE MATTER FOR 45 MINS; MAINT MEL'ED THE ACFT. 1) CHANGE THE PLT AFM. 2) CHANGE THE MAINT INTERP OF THEIR CHART. 3) THERE'S A SIMILAR SITUATION WITH AN ENG START. PLTS USE 475 DEGS MAX; MAINT USES 500 DEGS MAX. SINCE THAT'S NOT IN OUR AFM; I CAN'T REMEMBER WHAT TO DO OTHER THAN KEEP WRITING IT UP; JUST LIKE I DID WITH THE APU. 4) INSTALL AN IDIOT LIGHT SO PLTS SHUT DOWN THE APU ON THE GND WITH RED LIGHT ON. THIS WILL TAKE US OUT OF THE EQUATION; AND MAINT CAN ADJUST THE LIGHT TO COME ON WHERE THEY SET THE TEMP.

Data retrieved from NASA's ASRS site as of January 2009 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.