What happened
During the takeoff roll, the tread of the right nose landing gear tire separated from the casing. This mechanical failure inflicted significant damage to several surrounding components, including the ground shift mechanism, the nose gear door, the taxi light assembly, and the equipment compartment door. The flight crew elected to return to the departure airport for a safe landing.
Upon touchdown, the aircraft's anti-skid system was engaged. However, no braking action was available from the main wheel brakes. The pilot successfully brought the aircraft to a halt using reverse thrust alone.
The investigation
A thorough examination of the aircraft revealed that the damaged ground shift mechanism had sent an erroneous signal to the anti-skid control unit. This faulty input caused the system to incorrectly interpret the aircraft's status as airborne, thereby placing the brake system into an "airborne" mode where braking is disabled.
Inspection of the failed tire showed that a liner repair had been stitched over a cut area. Evidence indicated that the cut originated from a puncture wound in the tire structure.
Findings
The investigation determined that the root cause was the improper repair of the tire. Aviation guidance AC145-4, which covers the inspection and repair of aircraft tires, generally advises against attempting to repair cuts extending through more than 40% of the ply. Crucially, it explicitly states that tires with punctures are non-repairable. The presence of a stitched liner over a puncture site violated these safety standards.
The mechanical damage caused by the tire failure led to a secondary system failure in the braking controls. The combination of an unrepairable tire and the resulting false signal to the anti-skid system created a hazardous situation where primary braking means were unavailable during landing.