B737 flight crew rejected takeoff for a fire warning bell although no fire was in evidence once the aircraft stopped.
Synopsis
B737 flight crew rejected takeoff for a fire warning bell although no fire was in evidence once the aircraft stopped.
Narrative
The preflight; engine start; and taxi out were all normal. The takeoff was planned as flaps 15 bleeds off; max power takeoff. We were cleared for takeoff; the Captain pushed the power up; and all engine indications were normal. At approximately 70 KTS; the fire warning bell sounded; accompanied by the red; Fire Warning lights on the glareshield. The Captain immediately started closing the throttles and rejecting the takeoff. We guessed top speed to be just short of 80 KTS. The autobrake rejected takeoff function did not activate as our speed was so low. We cleared the runway and evaluated the cause of the warning. I can't remember now if we canceled the fire warning; or if it silenced itself; but we had no lights in any fire handle; or cargo compartment panel. We quickly tested all fire warning systems; and they tested normal; with no latent warning. CFR was called to evaluate the aircraft while the Captain made a quick PA. With the absence of a fire indication; we evaluated brake energy while the Fire and Rescue Crew checked the aircraft for signs of a fire. Brake energy was not a concern; and the Fire Department found no signs of fire or smoke. We elected to taxi to the gate; followed by the Fire Department; and deplane normally. However; we decided that in the event the warning had been caused by a cargo compartment fire; we would wait until all passengers had deplaned before having the cargo doors opened under the supervision of the Fire Department. When ground power was selected on; it failed and APU power was subsequently selected. Somewhere in that process; the master fire warning sounded; and the glareshield lights illuminated again very briefly (less than one second); with no lights in fire handles or on the cargo fire panel. The Fire Department found no indication of fire in the cargo compartment or engines/APU; and Maintenance was unable to duplicate the indications prior to our departure in a new aircraft.
Second reporter narrative
It was a bleeds off; flaps 15 takeoff. Shortly after thrust was set the Master Fire warning and bell activated. We rejected the takeoff immediately; at approximately 70 KIAS; prior to the '80 KTS' callout. It was manual brakes only since the autobrakes did not activate and we did not to deploy speedbrakes or reversers due to aircraft already being slowed to taxi speed.We were directed by the Tower to immediately clear the runway for an aircraft on a short final. There was no associated; illuminated fire light (engine; APU; or cargo bay) with the Master Fire warning. We completed the remainder of the Rejected Takeoff Checklist; did not set the parking brake; and evaluated the brake cooling at 75 KIAS; which called for normal cooling at the gate.We called for ARFF to inspect the aircraft and did a lights test to ensure there was no associated fire light with the Master Warning and bell. We briefed the Flight Attendants; made a PA to the Passengers; and notified the Company of our reject and plan to return to the gate if cleared by ARFF that it was safe to taxi. We coordinated on the Ground frequency with ARFF as they checked the aircraft for heat; smoke and/or fire. They determined there was no fire or smoke coming from any part of the aircraft. After all the passengers deplaned and we were cleared again by ARFF; the cargo bins were opened and no smoke or fire was present. We did a visual inspection of the aircraft; APU; and cargo bins and no smoke/or fire was evident.Of note; when shifting from aircraft to ground power at the gate; prior to engine shutdown; we received another momentary fire warning and bell. We suspect a faulty fire warning system.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.