Narrative:

Upon my arrival at the gate for an originating flight; the aircraft was in the process of being towed from a remote parking spot. I reviewed the release and noticed an MEL APU inoperative. However; when the aircraft arrived at the gate; the APU was running. It had been started in error by the ramper riding the brakes. I reviewed the logbook and the APU write-up was 2 days old. It indicated that the oil low pressure light remained illuminated and frequency and voltage readings read zero. Additionally; there was a sticker at the switch and a sticker inside the front cover of the logbook. However; at this time; the APU was performing as it was supposed to; the low oil pressure light was out and the frequency and voltage readings were correct. The ramper had xferred power to the generator busses. Bottom-line; the APU was not inoperative. I did not notice any historical write-ups in the logbook that concerned the APU (there may have been some; I did a fairly quick scan). I called dispatch to inform them that it appeared the write-up may be in error. I was told that it would cost too much to correct it in ZZZ and he would pass the information to maintenance and it would be addressed when we arrived at our first destination. The dispatcher indicated that the APU should not have been started. I agreed but since it had been and was working appropriately; I elected to use it. In retrospect; I probably should have just shut it down and pressed on without it. In-flight I messaged maintenance requesting someone meet me at the gate to address the situation. Upon arrival; I was met by a mechanic who said that; 'maintenance was a bit up in arms that we had used the APU. It had a history of low oil pressure problems.' he pulled a circuit breaker to ensure it could not be started and made an addition to the sp portion of the write-up. We continued on. A. My part (2 things): 1) I did a fairly quick scan of the logbook after I found the original write-up. It's possible there may have been history. I did not notice any; but neither can I say with absolute certainty that there wasn't any. I need to be more thorough in my review. 2) a more conservative approach by me may be warranted next time. I'll just return the aircraft to its MEL'ed status until the write-up is actually cleared. B. Ramp personnel: the person that started the APU in the first place needs to be refreshed on the need for logbook review and sticker observance (there was a sticker by the APU switch). C. Maintenance -- 2 things: 1) maybe a better write-up would have helped prevent this type of event. APU inoperative didn't really tell the correct story; it wasn't inoperative it just had some problems that required it to not be used. 2) since maintenance was riled up that I used the APU; my guess is that the dispatcher passed the word to them concerning our conversation. If the problem was such that it excited them; maybe they or dispatch could have let me know about their concerns before I reached the maintenance base (I'm thinking the APU is good -- if some type of event had required its use; I would have used it). Further; since it was important enough an issue that they eventually pulled a circuit breaker to prevent future starts; maybe that should be an initial precautionary measure in APU problems like this. Sum: I am not aware of any significant problem that resulted from this event. However; it is a good example of how contributions from different entities can lead to a potentially bad situation. If the ramper hadn't started the APU there would have been no problem. If the logbook entry had provided some more enlightening information or maintenance concerns had been relayed; I'd have shut it down without reservation and there would have been no subsequent problems. If I'd have taken a more conservative approach and shut it down; again there would have been no subsequent problems. If the circuit breaker had been pulled in the first place; there would have been no problem. In my case -- lesson learned.

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Original NASA ASRS Text

Title: B737 CAPT REPORTS ACFT WITH MEL'ED APU IS TOWED TO GATE WITH APU RUNNING. APU IS USED TO START ENGINES.

Narrative: UPON MY ARR AT THE GATE FOR AN ORIGINATING FLT; THE ACFT WAS IN THE PROCESS OF BEING TOWED FROM A REMOTE PARKING SPOT. I REVIEWED THE RELEASE AND NOTICED AN MEL APU INOP. HOWEVER; WHEN THE ACFT ARRIVED AT THE GATE; THE APU WAS RUNNING. IT HAD BEEN STARTED IN ERROR BY THE RAMPER RIDING THE BRAKES. I REVIEWED THE LOGBOOK AND THE APU WRITE-UP WAS 2 DAYS OLD. IT INDICATED THAT THE OIL LOW PRESSURE LIGHT REMAINED ILLUMINATED AND FREQ AND VOLTAGE READINGS READ ZERO. ADDITIONALLY; THERE WAS A STICKER AT THE SWITCH AND A STICKER INSIDE THE FRONT COVER OF THE LOGBOOK. HOWEVER; AT THIS TIME; THE APU WAS PERFORMING AS IT WAS SUPPOSED TO; THE LOW OIL PRESSURE LIGHT WAS OUT AND THE FREQ AND VOLTAGE READINGS WERE CORRECT. THE RAMPER HAD XFERRED PWR TO THE GENERATOR BUSSES. BOTTOM-LINE; THE APU WAS NOT INOP. I DID NOT NOTICE ANY HISTORICAL WRITE-UPS IN THE LOGBOOK THAT CONCERNED THE APU (THERE MAY HAVE BEEN SOME; I DID A FAIRLY QUICK SCAN). I CALLED DISPATCH TO INFORM THEM THAT IT APPEARED THE WRITE-UP MAY BE IN ERROR. I WAS TOLD THAT IT WOULD COST TOO MUCH TO CORRECT IT IN ZZZ AND HE WOULD PASS THE INFO TO MAINT AND IT WOULD BE ADDRESSED WHEN WE ARRIVED AT OUR FIRST DEST. THE DISPATCHER INDICATED THAT THE APU SHOULD NOT HAVE BEEN STARTED. I AGREED BUT SINCE IT HAD BEEN AND WAS WORKING APPROPRIATELY; I ELECTED TO USE IT. IN RETROSPECT; I PROBABLY SHOULD HAVE JUST SHUT IT DOWN AND PRESSED ON WITHOUT IT. INFLT I MESSAGED MAINT REQUESTING SOMEONE MEET ME AT THE GATE TO ADDRESS THE SITUATION. UPON ARR; I WAS MET BY A MECH WHO SAID THAT; 'MAINT WAS A BIT UP IN ARMS THAT WE HAD USED THE APU. IT HAD A HISTORY OF LOW OIL PRESSURE PROBS.' HE PULLED A CIRCUIT BREAKER TO ENSURE IT COULD NOT BE STARTED AND MADE AN ADDITION TO THE SP PORTION OF THE WRITE-UP. WE CONTINUED ON. A. MY PART (2 THINGS): 1) I DID A FAIRLY QUICK SCAN OF THE LOGBOOK AFTER I FOUND THE ORIGINAL WRITE-UP. IT'S POSSIBLE THERE MAY HAVE BEEN HISTORY. I DID NOT NOTICE ANY; BUT NEITHER CAN I SAY WITH ABSOLUTE CERTAINTY THAT THERE WASN'T ANY. I NEED TO BE MORE THOROUGH IN MY REVIEW. 2) A MORE CONSERVATIVE APCH BY ME MAY BE WARRANTED NEXT TIME. I'LL JUST RETURN THE ACFT TO ITS MEL'ED STATUS UNTIL THE WRITE-UP IS ACTUALLY CLRED. B. RAMP PERSONNEL: THE PERSON THAT STARTED THE APU IN THE FIRST PLACE NEEDS TO BE REFRESHED ON THE NEED FOR LOGBOOK REVIEW AND STICKER OBSERVANCE (THERE WAS A STICKER BY THE APU SWITCH). C. MAINT -- 2 THINGS: 1) MAYBE A BETTER WRITE-UP WOULD HAVE HELPED PREVENT THIS TYPE OF EVENT. APU INOP DIDN'T REALLY TELL THE CORRECT STORY; IT WASN'T INOP IT JUST HAD SOME PROBS THAT REQUIRED IT TO NOT BE USED. 2) SINCE MAINT WAS RILED UP THAT I USED THE APU; MY GUESS IS THAT THE DISPATCHER PASSED THE WORD TO THEM CONCERNING OUR CONVERSATION. IF THE PROB WAS SUCH THAT IT EXCITED THEM; MAYBE THEY OR DISPATCH COULD HAVE LET ME KNOW ABOUT THEIR CONCERNS BEFORE I REACHED THE MAINT BASE (I'M THINKING THE APU IS GOOD -- IF SOME TYPE OF EVENT HAD REQUIRED ITS USE; I WOULD HAVE USED IT). FURTHER; SINCE IT WAS IMPORTANT ENOUGH AN ISSUE THAT THEY EVENTUALLY PULLED A CIRCUIT BREAKER TO PREVENT FUTURE STARTS; MAYBE THAT SHOULD BE AN INITIAL PRECAUTIONARY MEASURE IN APU PROBS LIKE THIS. SUM: I AM NOT AWARE OF ANY SIGNIFICANT PROB THAT RESULTED FROM THIS EVENT. HOWEVER; IT IS A GOOD EXAMPLE OF HOW CONTRIBUTIONS FROM DIFFERENT ENTITIES CAN LEAD TO A POTENTIALLY BAD SITUATION. IF THE RAMPER HADN'T STARTED THE APU THERE WOULD HAVE BEEN NO PROB. IF THE LOGBOOK ENTRY HAD PROVIDED SOME MORE ENLIGHTENING INFO OR MAINT CONCERNS HAD BEEN RELAYED; I'D HAVE SHUT IT DOWN WITHOUT RESERVATION AND THERE WOULD HAVE BEEN NO SUBSEQUENT PROBS. IF I'D HAVE TAKEN A MORE CONSERVATIVE APCH AND SHUT IT DOWN; AGAIN THERE WOULD HAVE BEEN NO SUBSEQUENT PROBS. IF THE CIRCUIT BREAKER HAD BEEN PULLED IN THE FIRST PLACE; THERE WOULD HAVE BEEN NO PROB. IN MY CASE -- LESSON LEARNED.

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