What happened
On the morning of 24 May 1999, a BAe 146-200 aircraft, registration EI-CMS, was positioned at Stand 42A at Dublin Airport preparing for a scheduled flight to Paris. While the aircraft was undergoing pre-departure inspections and the loading of baggage was underway, an equipment tow tractor used for baggage handling lost traction and struck the aircraft.
The impact occurred at approximately 06:44 hours. As the tug was maneuvering toward the rear of the aircraft with a loaded trolley attached, it slid into the starboard side of the rear fuselage. The collision caused a 2-foot long score mark along the fuselage skin, which included a puncture measuring approximately 4.25 inches in length and 0.4 inches in depth. There were no injuries to the 40 passengers or 4 crew members on board, but the aircraft was declared unserviceable for flight following the incident.
The investigation
The AAIU investigation examined the environmental conditions, the mechanical state of the ground equipment, and the operational procedures in place at the time. The investigator noted that while the concrete at the stand was dry during the inspection, there was clear evidence of recent rainfall, leaving the ground wet.
Technicians inspected the electric tow tractor and found its three independent braking systems—including hydraulic drum brakes and regenerative electric braking—to be fully functional. However, the investigation focused on the vehicle's tires. While the rear tires featured a fine thread, the front tires were a different "block" tread type. The manufacturer's specifications recommended 23 X 5 pneumatic tires, but the investigation found the tractor was fitted with "Super-Cushioned" solid rubber tires on the front axle.
Findings
- The primary cause of the contact was that the tug was being driven too close to the aircraft given the wet surface conditions.
- The use of coarse-tread block-type tires on the front of the tractor likely reduced the available grip on the damp ground compared to the manufacturer-recommended pneumatic tires.
- The ground handler assisting with the loading was positioned inside the rear baggage hold during the maneuver; had they been outside the aircraft to act as a guide, the risk might have been mitigated.
Safety action
- It is recommended that the manufacturer-specified tire size and type should be used on tugs whenever they are commercially available.
- The Handling Agent should consider strengthening their safety regulations to mandate that aircraft must not be approached unless a competent guide person is present and available.