Incident Overview
On a calibration flight originally planned from Mehrabad Airport in Tehran to Kish Island Airport, an aircraft operated by Iran Aseman Airline (AOC No. FS-102) crashed into the sea during an approach cycle. The flight was carrying eight persons initially: three pilots, four ground technicians, and a security guard. After landing, the four ground technicians disembarked, and refueling was performed. The aircraft then departed on a calibration mission, performing multiple approach and climb cycles for navigation-aids inspection. During the eighth cycle, while turning to the final approach before the runway threshold, the aircraft crashed into the sea and was destroyed. All four remaining occupants were killed.
Flight Sequence
The flight departed Mehrabad Airport from Runway 29L at 15:03 local time, climbing to cruise altitude FL270. It landed at Kish Island Airport on Runway 09L at 16:44 local time. After the four ground technicians left and refueling was completed, the aircraft took off from Runway 27R at 17:44 local time. The crew requested to join a right downwind leg at 1,000 feet and 8 miles from the airport. Over the next hour, the aircraft performed seven full approach and climb cycles for calibration purposes. At approximately 18:45 local time, during the eighth cycle, while turning onto the final approach segment before the runway threshold, the aircraft struck the sea and was destroyed.
Probable Cause and Contributing Factors
The official investigation determined the probable cause as pilot fatigue, which led to an inability to adapt to flight conditions and resulted in spatial disorientation (illusion). This error prevented the pilots from avoiding the crash into the sea. Contributing factors identified in the report include a malfunction of the aircraft's radio altimeter, flight crew fatigue, and a lack of adequate supervision over flight calibration operations.