What happened
A freight operation traveling from Kuwait to Tehran experienced a fatal accident shortly after departing for its destination. The flight was being conducted as part of a route from Beirut to Tehran via Kuwait. During the leg between Kuwait and Tehran, a check pilot was performing various test maneuvers to evaluate the proficiency of the pilot in command and the co-pilot as part of their license renewal process.
While the Avro York was in its initial climb phase, the aircraft became uncontrollable. The plane impacted the ground 11 km southeast of Karaj, west of Tehran, resulting in a massive explosion. The impact caused the total destruction of the airframe. There were four fatalities among the crew members on board.
Findings
Investigation into the accident focused on the engine configuration and propeller settings at the moment of impact. Evidence regarding the position of the propellers suggested that an emergency situation occurred involving the number 3 and number 4 engines. Specifically, it appeared that power was lost on the number 4 engine, which led to a sequence where the number 3 engine was feathered and then unfeathered.
Another possibility considered by investigators was that the crew may have accidentally manipulated the feathering switches during the flight training maneuvers, leading to a loss of power on the starboard engines. Because the Avro York was operating at a low altitude following its departure from Mehrabad Airport—which sits at an elevation of 3,900 feet—the crew lacked the necessary altitude to recover the aircraft once the engine power issues developed.