What happened
On August 17, 2015, a Falcon 90 0LX, registration TC-AOM, was performing a final approach to runway 05 at Geneva Airport (LSGG). The aircraft, operated by Setair Hava Taşımacılığı ve Hizmetleri A.Ş, was carrying two pilots and a technician who was conducting a technical inspection as part of an aircraft sale. During the approach, the "FIRE REAR COMP" alarm activated in the cockpit.
In response to the alert, the pilot discharged the relevant fire extinguishing bottle, which caused the alarm to cease several seconds later. The crew continued the approach and landed the aircraft normally. After exiting the runway via taxiway Y, the aircraft stopped at the Yankee holding bay. Airport fire services inspected the rear compartment using a thermal camera, but they found no evidence of fire, overheating, or abnormal temperatures. The aircraft was subsequently towed to a hangar for further investigation.
The investigation
The investigation focused on the rear compartment fire detection system, which utilizes two "Pinpoint" type detectors located on the left and right sides of the compartment. Under normal operating conditions, these detectors trigger an audible alarm and a red light on the overhead panel if temperatures reach between 130 and 210 °C.
Testing conducted by a technician revealed that the right-side fire detector was malfunctioning. Specifically, the detector was triggering an alert at a temperature of just below 100 °C, which is significantly lower than the required threshold. Following the discovery, both detectors were replaced as a precaution. Subsequent pneumatic leak tests performed with all three engines running confirmed that the pneumatic and detection systems were functioning correctly.
Findings
- The primary cause of the incident was a defective right-side fire detector (12WG) that triggered at temperatures below 100 °C.
- The pilot's action of discharging the fire extinguishing bottle did not actually suppress a fire; rather, the alarm ceased because the temperature in the compartment dropped below the faulty detector's erroneous threshold.