What happened
On May 17, 2012, a Shorts SD3-60 aircraft, registration N617FB, was taxiing toward runway 8R at George Bush Intercontinental Airport in Houston, Texas. The flight, operated by Air Cargo Carriers LLC, was scheduled for a cargo flight to Austin, Texas.
The flight crew reported that the aircraft was approximately 6 and 60 pounds over its maximum takeoff weight. Due to the long taxi distance to the assigned runway, the crew decided to reduce the aircraft's weight by burning fuel during the taxi. To achieve this, they utilized higher-than-normal engine power settings while simultaneously applying the wheel brakes to maintain a controlled taxi speed.
During the taxi, the tires on both the left and right main landing gear deflated after the fusible plugs in the wheels blew out due to overheating. A fire subsequently ignited in the right wheel housing. The crew felt the aircraft yaw during the deflation and were alerted by a following aircraft via radio that the right wheel was on fire. The crew stopped the aircraft, evacuated, and attempted to use handheld fire extinguishers on the fire. Airport firefighting personnel eventually extinguished the flames using foam suppressant. There were no injuries to the flight crew or ground personnel.
The investigation
Post-accident inspections conducted by the FAA, the NTSB, and the operator's maintenance personnel found no evidence of mechanical malfunction or abnormalities within the wheel and brake systems. The investigation confirmed that the fusible plugs on both main wheels functioned as designed by blowing out to prevent further hazards during severe overheating.
However, the fire caused substantial damage to the right main gear housing, which is part of the stub wing assembly structure and includes the attachment fitting for the wing strut. The operator determined that the structural damage was too extensive to make repairs practical.