What happened
On 29 May 2005, a Pierre Robin HR10/200B, registration G-CBFN, was performing a private flight to Blackbushe Airport. The flight had previously completed an uneventful landing at Perranporth. Upon approaching Runway 25 at Blackbushe, the pilot maintained a speed between 85 and 90 kt with flaps 1 selected.
While the touchdown itself was normal, the pilot found that applying the brakes produced no deceleration. Despite an attempt to have a passenger assist with brake pressure, the aircraft failed to slow down. Approximately 200 m before the end of the runway, the pilot transmitted a brake failure message. Unable to perform a go-around, the aircraft overran the runway and came to rest in a bank of gorse bushes. The 2 occupants escaped the aircraft without assistance, though the aircraft sustained damage to the nose structure, nose landing gear, and the right wing leading edge.
The investigation
Investigators examined the aircraft's braking system and performed metallurgical analysis at QinetiQ. The investigation focused on the condition of the brake pads and the maintenance history of the aircraft. It was noted that the aircraft was fitted with wheel spats, which made pre-flight inspections of the brake condition difficult.
Analysis of the brake pads revealed extensive damage to both sets. Microscopic examination showed that the friction material had been bonded to an oxide layer on the backing plates, which likely created a weak bond. There was also evidence of metal smearing and deformation on the backing plates, suggesting significant heat generation during the braking event.
Findings
- The primary cause of the overrun was the loss of braking effectiveness due to the failure of the brake pads.
- The brake pads installed on G-CBFN were not manufacturer-approved parts; they had been relined by an automotive supplier using an adhesive and heat treatment rather than the manufacturer's specified riveting method.
- Metallurgical evidence indicated the friction material was bonded to an oxide layer, which could have led to disbonding.
- The aircraft's maintenance history showed a pattern of reported braking issues, including a previous runway overrun in 2004.
- The use of wheel spats hindered the ability to perform effective visual inspections of the brake assembly.
Safety action
It is recommended that Apex Aircraft, the manufacturer, provides information to owners and maintenance organisations regarding the updated standard for brake pads, which requires both adhesive and rivets to prevent disbonding.