Incident Overview
On May 17, 2012, at approximately 0715 central daylight time, a Shorts SD3-60, registration N617FB, operated by Air Cargo Carriers LLC as a Part 135 cargo flight, was substantially damaged by a wheel brake fire during taxi at George Bush Intercontinental Airport in Houston, Texas. The airline transport pilot and commercial co-pilot were not injured. Visual meteorological conditions prevailed, and a flight plan was filed. The flight was taxiing for takeoff from runway 8R, destined for Austin, Texas.
Sequence of Events
The flight crew reported that the aircraft was about 60 pounds over its maximum takeoff weight. Because the taxi to the assigned runway was long, they decided to burn off fuel by using higher-than-normal engine power settings while maintaining some braking to control speed. During the taxi, the right and left main landing gear tires deflated when the fusible plugs in the wheels blew out due to overheating, and a fire ignited in the right wheel housing. The crew felt the aircraft yaw as the tires deflated and were informed by radio from a following aircraft that their right wheel was on fire. They stopped the aircraft on the taxiway, evacuated, and attempted to extinguish the fire with two handheld fire extinguishers.
Firefighting and Damage
Airport firefighting personnel arrived and extinguished the fire using foam suppressant. The fire resulted in substantial damage to the wing support structures. No injuries occurred to the flight crew or ground personnel. Postaccident examination by an FAA inspector, an NTSB investigator, and the operator's maintenance personnel showed no evidence of mechanical malfunction or abnormalities with the wheel and brake system.
Aircraft and System Details
The Shorts SD3-60 is a twin turboprop, strutted, high-wing aircraft. Each main wheel is equipped with fusible plugs designed to blow out in the event of severe wheel overheating. Inspection after the accident confirmed that the plugs on both main wheels operated as designed. The fire caused severe damage to the right main gear housing, part of the stub wing assembly structure that includes the attachment fitting for the wing strut. The operator's maintenance department determined that the fire caused substantial structural damage, making repair impractical.
Crew and Operator Actions
The operator submitted in NTSB Form 6120 that both crew members stated they had been trained not to ride the brakes while taxiing. The captain stated he did not realize the risk of blowing tires or causing a fire otherwise he would not have attempted to burn off fuel while taxiing. The operator revised its training program to highlight the hazards of excessive brake use during ground operations, emphasized the purpose of fusible plugs, and planned to use photographs of this event in future training classes on the brake system.