Accident Overview
On 28 February 2020, at 1522 UTC, an Airbus A300B4-203F freighter, registered UP-A3003 and operated by Sigma Airlines, collided with a ground support vehicle while parking at Sharjah International Airport, United Arab Emirates. The aircraft had just returned from Juba Airport, South Sudan, with five crew members on board.
Sequence of Events
The aircraft landed at 1515 UTC and taxied to the cargo apron. The commander stated that the descent, approach, landing, and taxi were uneventful. After stopping in front of the cargo hangar, the commander maintained manual brakes while the crew began the parking checklist. The commander then realized the aircraft was moving forward. He repeatedly applied manual brakes and set the parking brake, but the aircraft did not stop. He steered left to avoid the cargo hangar, and the left engine collided with a parked tug in the equipment area.
Damage and Injuries
There were no injuries. The aircraft's left engine, pylon, and wing attachment were substantially damaged. The tug was also damaged.
Hydraulic System Failure
During the descent, moderate turbulence caused the yellow hydraulic system fluid level to drop rapidly, and the HYDRAU light illuminated. The flight crew executed the checklist for hydraulic system loss and continued with the autopilot disconnected. They did not inform air traffic control or ground staff about the issue. The investigation found that the loss of the yellow hydraulic system resulted from a fractured high-pressure filter housing. For reasons the investigation could not determine, a secondary failure also depressurized the system accumulators and disabled the parking brake function. The aircraft moved forward due to engine idle thrust.
Contributory Factors
The investigation found that the commander's decision to select the parking brake without sufficient yellow hydraulic system pressure and before the nose wheels were chocked was a contributing factor. The marshaller was not prepared to chock the aircraft after it arrived at the parking bay and could not react in time to stop its movement.
Manufacturer Awareness
Airbus became aware that the design of the high-pressure filter head, apart from inadequate attachment bolts, was another contributor to fractures at the head flange. Airbus issued a service bulletin for replacement of the attachment bolts and communicated the filter head design issue to operators in technical documents and during a technical symposium.