Narrative:

Operating flight from buf to pit. While waiting at the gate a master warning came on out of the blue indicating a red message, lift dumpers unsafe, along with a 3 bell alert. Maintenance checked the system and could not reset it. Opted to MEL lift dumpers since WX was VFR with no rain and runways were long and dry, well within required specifications for operation without lift dumpers. When maintenance got system labeled as MEL, proceeded with taxi-out for takeoff. When taking the turn onto the runway, we performed the final check with the first officer checking visually the lift dumpers as being retracted and testing the takeoff normal rest button, we received a 3 level alert. By running the power levers up for a quarter the alert definitely came on again and we returned to the gate. The speed at abort was not yet registered on the airspeed indicator nor were brakes used other than normal, but we were on the runway itself and vacated same. Callback conversation with reporter revealed the following information: aircraft equipped with 2 computers versus normal 3. As a result maintenance manual are not complete in so far as wiring diagrams are concerned, had problems trying to de-activate the 'lift dumper' system. After return to the ramp a mechanic more familiar with the aircraft was able to comply with the MEL and the aircraft was flown to pit.

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Original NASA ASRS Text

Title: MEL LIFT DUMPER RESULT IN SECOND WARNING AND TKOF ABORT.

Narrative: OPERATING FLT FROM BUF TO PIT. WHILE WAITING AT THE GATE A MASTER WARNING CAME ON OUT OF THE BLUE INDICATING A RED MESSAGE, LIFT DUMPERS UNSAFE, ALONG WITH A 3 BELL ALERT. MAINT CHKED THE SYS AND COULD NOT RESET IT. OPTED TO MEL LIFT DUMPERS SINCE WX WAS VFR WITH NO RAIN AND RWYS WERE LONG AND DRY, WELL WITHIN REQUIRED SPECS FOR OPERATION WITHOUT LIFT DUMPERS. WHEN MAINT GOT SYS LABELED AS MEL, PROCEEDED WITH TAXI-OUT FOR TKOF. WHEN TAKING THE TURN ONTO THE RWY, WE PERFORMED THE FINAL CHK WITH THE FO CHKING VISUALLY THE LIFT DUMPERS AS BEING RETRACTED AND TESTING THE TKOF NORMAL REST BUTTON, WE RECEIVED A 3 LEVEL ALERT. BY RUNNING THE PWR LEVERS UP FOR A QUARTER THE ALERT DEFINITELY CAME ON AGAIN AND WE RETURNED TO THE GATE. THE SPD AT ABORT WAS NOT YET REGISTERED ON THE AIRSPD INDICATOR NOR WERE BRAKES USED OTHER THAN NORMAL, BUT WE WERE ON THE RWY ITSELF AND VACATED SAME. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: ACFT EQUIPPED WITH 2 COMPUTERS VERSUS NORMAL 3. AS A RESULT MAINT MANUAL ARE NOT COMPLETE IN SO FAR AS WIRING DIAGRAMS ARE CONCERNED, HAD PROBS TRYING TO DE-ACTIVATE THE 'LIFT DUMPER' SYS. AFTER RETURN TO THE RAMP A MECH MORE FAMILIAR WITH THE ACFT WAS ABLE TO COMPLY WITH THE MEL AND THE ACFT WAS FLOWN TO PIT.

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.