On 28 February 2020 at 04:50 UTC an Airbus A300B4-203F freighter aircraft, registration UP-A3003, departed Sharjah International Airport (OMSJ), the United Arab Emirates, destined for Juba Airport (HSSJ), South Sudan. There were five crewmembers onboard comprising the captain, the copilot and the flight engineer on the flight deck, together with a loadmaster and an aircraft engineer who were seated in the galley area. The flight was uneventful and the Aircraft landed at 08:45 UTC at HSSJ. Prior to departure, after one hour and 35 minutes on the ground, the captain and the aircraft engineer completed the transit check. The captain noticed oil dripping from the lower fuselage. The aircraft engineer advised the captain that four days before the green hydraulic system tank had been replaced and that the oil was most likely residue from this maintenance action. He assured the captain that the aircraft would be cleaned on arrival in Sharjah. The aircraft departed HSSJ at 10:20 UTC for OMSJ. The departure and flight were uneventful until when at FL350 in the Muscat flight information region (FIR), the captain requested a flight level change due to moderate turbulence. According to his statement, immediately after starting the descent, he received a report from the flight engineer that the fluid level in the yellow hydraulic system had rapidly decreased and the “HYDRAU” light had illuminated on the master warning panel, followed by an autopilot disconnect. The checklist items for the hydraulic system loss from the Quick Reference Handbook (QRH) were followed and the flight continued manually with the captain as the pilot flying (PF). According to the captain, Air Traffic Control (ATC) was not informed of the hydraulic system loss, but that the flight crew prepared for an extended landing distance of 1.2 times the normal landing distance. The aircraft landed at 15:15 UTC at OMSJ on runway 30 and exited on the high-speed taxiway B7. The captain stated that the descent, approach, landing and taxiing to the cargo apron were uneventful, and that the brakes functioned normally. The captain followed the marshaller’s instructions and stopped the aircraft at the assigned A300 position mark on parking stand 57, in front of the cargo hangar. The captain stated that once the aircraft came to a stop, he applied manual brakes and set the parking brake. While the crew started the parking checklist, the copilot prepared to shut the engines down. When the captain looked up, he realized that the aircraft was moving forward and he applied manual brakes but the aircraft did not stop. He stated that he then steered to the left to avoid the cargo hangar in front of the aircraft but the aircraft continued to move until the No.1 engine collided with a tug which was parked in the equipment area, approximately 36 meters beyond the A300 position mark. An inspection identified that the yellow hydraulic system high-pressure filter housing, located in the lower fuselage, had fractured and leaked hydraulic fluid. Causes The Air Accident Investigation Sector of the United Arab Emirates determines that the causes of the Aircraft collision with a parking tow tug and the consequent substantial damage were: (a) The uncontrolled movement of the Aircraft by engine idle thrust beyond the parking stop line. (b) The Aircraft could not be maintained at rest after the initial stop because the selected parking brake was not operational due to a leak from a fracture in the yellow hydraulic system high-pressure filter head, and a failure of the accumulator system of the parking brake that could not be determined during the Investigation. (c) The Aircraft could not be stopped by manual braking because that the ‘Manual’ brake was disabled after the flight crew selected the ‘Parking’ brake without prior confirmation that adequate parking pressure was available. 3.4 Contributing Factors to the Accident The Investigation identified that the following were contributing factors to the Accident: (a) Airbus had identified the design of the high-pressure filter head as one of two contributors to fractures developing at the head flange, but did not address this issue with equal priority. (b) The marshaller was not prepared to place wheel chocks on the Aircraft’s arrival at the parking bay and was therefore unable to react timely to obstruct the movement of the Aircraft.