B777-200
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Situational Awareness; Communication Breakdown
Ground Event / Encounter Other / Unknown
Flight Crew FLC complied w / Automation / Advisory
Human Factors; Procedure
After shutting down both engines in the gate we got a 'LWR AFT CARGO' fire warning. We ran the checklist and discharged the fire suppressant. I then asked ramp personnel if there was any sign of fire or smoke near the lower aft cargo door. They said no. I was then informed that one of the ramp workers had opened the lower aft cargo door; placed an insecticide spray bottle in the bay; and then closed the door. The resulting mist is what set off the fire alarm. There was never any actual smoke or fire. I then notified Maintenance and wrote up the AML.Placing an activated insecticide spray bottle in the cargo compartment; which tricked the system into thinking there was smoke in the bay; when in fact it was simply the mist from the insecticide bottle.Have the ramp agents tell the crew they are about to place an activated insecticide spray bottle in the cargo compartment; and might get a fire alarm. The crew can then monitor the EICAS for any alarms. If an alarm occurs; the crew can then verify with ramp personnel there is no actual smoke emanating from the lower aft cargo bay; and decide whether or not to run the checklist and discharge the fire suppressant.
B777 Captain reported responding to a LWR AFT CARGO fire warning by discharging extinguishing agent into the cargo bay while parked at the gate. Crew was advised the warning was triggered by Ground Personnel placing an insecticide spray bottle in the compartment.