What happened
On 1 May 1998, a Boeing 767-336, registration G-BNWF, was performing a scheduled passenger flight to London Heathrow. The aircraft landed on runway 09L with a landing weight of 112.2 tonnes. The crew performed a manual landing using flap 30 and level 3 autobrake settings. During the braking phase, the commander noted a slight grab in the right brakes, though performance otherwise appeared normal.
As the aircraft taxied to its stand, the crew observed that the right rear brake temperature had risen significantly, reaching level 5 on the EICAS. Shortly after parking, the crew was alerted that the right brakes were smoking. Simultaneously, the EICAS indicated a low fluid level in the right hydraulic system. There were no injuries to the 10 crew members or 198 passengers during the event.
The investigation
Investigators examined the right main landing gear and discovered that the brake reaction rod at the No 8 wheel had failed at its attachment point to the brake assembly. This failure caused the assembly to rotate with the wheel, which subsequently ruptured the electrical and hydraulic connections, leading to the loss of hydraulic fluid. The failed rod remained attached at the centre bolt of the landing gear leg, trailing along the runway surface.
Data from the Quick Access Recorder (QAR) confirmed that brake pressures on both gears decreased momentarily at a speed of approximately 76 kt. The investigation also revealed that the bushing for the attachment pin in the brake housing had become ovalised, indicating that the component had been subjected to high loads. Analysis of the fracture surface showed an overload failure in tension.
Findings
- The primary cause was the failure of the brake reaction rod at the No 8 wheel due to an overload in tension.
- The failure of the rod led to the rotation of the brake assembly, resulting in the rupture of hydraulic and electrical lines.
- The incident was linked to the dynamic characteristics of carbon/carbon brakes on the Boeing 767 fleet, specifically high loads generated by energetic vibration modes.
- This specific failure mode, involving the failure of the rod end cap, had not been previously recorded.