What happened
On 26 November 2005, a Boeing 737-8AS, registration EI-DAP, was parked at Stand 4 of Glasgow Prestwick Airport. The flight crew were performing standard shutdown procedures, which included connecting ground power and opening the front cargo hold door. During this process, an Avia Lift baggage belt vehicle was being maneuvered toward the front of the aircraft.
As the vehicle approached, the driver attempted to apply the footbrake, but the pedal traveled to the floor without providing any deceleration. The driver attempted to use the handbrake, but it failed to function. In an effort to avoid the open cargo hold, the driver steered the vehicle to the right, causing the conveyor belt—which overhangs the front of the vehicle—to strike the aircraft fuselage. The impact caused a minor dent in the fuselage and broke the radar antenna. There were no injuries to the 181 passengers or 6 crew members on board.
The investigation
The investigation examined the mechanical condition of the baggage vehicle and the maintenance protocols of the airport authority. It was discovered that the vehicle's footbrake system was a non-assisted single-circuit hydraulic system. Post-accident inspections revealed that the hydraulic pipe leading to the front offside wheel cylinder had fractured, resulting in an immediate loss of brake fluid pressure. Furthermore, the front section of the parking brake cable, which had been replaced only months prior, was found to be seized.
Findings
- The primary cause of the collision was a failure in the hydraulic pipe system for the brakes.
- The driver had no prior warning of the impending failure because the hydraulic leak caused an immediate loss of pressure.
- The parking brake was unavailable due to a seized cable, a defect that could have been identified during a daily inspection.
- The vehicle's automatic transmission featured a 'park' setting that, if used regularly, might have reduced the wear and frequency of use of the parking brake, potentially preventing the cable seizure.
- A delay in reporting the incident occurred; the aircraft captain was not notified of the impact until after he had opened the flight deck window, and the official 'Aircraft Ground Incident' was not declared until approximately 20 minutes after the collision.
Safety action
Following the incident, the airfield management recommended reviews of the ground vehicle fleet, maintenance reporting processes, and the frequency of servicing schedules. The AAIB issued a Safety Recommendation to the Civil Aviation Authority, advising that airport Safety Management Systems should ensure that rigorous maintenance and usage standards are applied to all mobile ground equipment operating near aircraft.