What happened
On 20 August 2002, a BAe.ATP, registration G-MANG, was operating a public transport flight from Glasgow to Belfast. While cruising at FL100, the crew received a warning light indicating an overheat in the right-hand landing gear bay. Following established procedures, the crew lowered the landing gear, which caused the warning light to extinguish. However, the subsequent checklist instructions required the crew to perform an engine fire in flight drill, leading to the shutdown of the right engine.
The crew declared a MAYDAY and diverted to Prestwick Airport. The aircraft landed on Runway 31 using only a single engine. Although a cabin crew member inspected the engine and saw no issues, the airfield fire service observed small flames and smoke emerging from the area between the two right main wheels once the aircraft had stopped. Following an emergency evacuation, the commander and the fire chief inspected the aircraft and found no physical damage. Due to a lack of available towing equipment, the crew restarted the left engine and taxied the aircraft away from the runway.
Four days later, during a ferry flight from Glasgow, the same landing gear bay overheat warning recurred, necessitating another return to Glasgow and a second engine shutdown.
The investigation
The investigation focused on the cause of the overheat warnings and the adequacy of the emergency procedures. An engineer from Glasgow inspected the aircraft and suggested the flames seen at Prestwick might have been caused by a heat pack fire. Following the incident, the brake control valve and the No 3 Maxaret unit were replaced. Crucially, investigators discovered that manipulating the electrical wiring loom for the overheat sensors could trigger the warning, and they identified a chafed and damaged cable within the system.
Findings
- The primary cause of the overheat warnings was a damaged and chafed electrical cable in the overheat sensor wiring loom.
- The aircraft's checklist at the time required an engine shutdown because the sensor used for landing gear bay overheat detection was also used to detect engine torching.
- The aircraft had not yet been fitted with a flame guard modification, which allows for the detection of torching flames via a separate system, thereby avoiding the need for an in-flight engine shutdown.