What happened
On 8 December 2016, a Cessna 350, registration N1222G, was undergoing a test flight at Seletar Airport, Singapore, following a period of being grounded for repairs. Prior to the flight, the pilot and a mechanic performed a high-speed brake test to bed in new brake linings. Shortly after this test, the pilot attempted a rolling takeoff but aborted the maneuver at approximately 75 knots after the aircraft began veering to the left.
During the aborted takeoff, the pilot applied the brakes at 50 knots, noting they felt sluggish. While taxiing back to the parking area, the pilot experienced a loss of braking capability. The aircraft drifted off the taxiway centerline, narrowly avoiding a parked Cessna 172 and a jet aircraft being towed. Upon coming to a stop, a burning smell was detected in the cockpit, prompting an immediate evacuation. Shortly after the crew exited, the main landing gear caught fire, causing heat damage to the wheels and the lower fuselage.
The investigation
Investigators examined the aircraft's flight controls, engine, and hydraulic systems, finding no mechanical anomalies in those areas. However, the investigation focused on the brake assembly and the thermal conditions of the wheels. The inspection revealed that the brake fluid reservoir was empty and the brake components showed signs of charring and uneven wear. The investigation also reviewed the aircraft's weight and balance, discovering that the takeoff weight of approximately 3,428.5 pounds actually exceeded the maximum gross weight of 3,400 pounds.
Findings
- The fire was likely caused by overheating of the brakes due to insufficient cooling time between the high-speed brake test and the subsequent takeoff attempt.
- The pilot did not allow for the 20-minute cooling period recommended in the Pilot’s Operating Handbook (POH).
- The thermal load was increased by the heavy braking used during the aborted takeoff and subsequent taxiing.
- The aircraft was operating above its maximum gross weight.
- The aircraft's weight and balance documentation had not been updated following a recent weighing.