The first conclusions of the investigation, backed by a preliminary study of the black boxes found in the ATR72 plane that crashed in Iran on February 18, 2018, hints at the responsibility of the pilot.

The ATR72 operated by the company Aseman Airlines was on its way from Tehran to Yasuj and was about to land. It crashed in a mountainous area at about 4.000 meters of altitude, killing the 66 passengers. Heavy snow had suspended the recovery operations for several days.

The flight records show that pilots started their approach towards Yasuj airport by descending at 17.000 feet as demanded by control tower. However, the autopilot was then set down to 15.000, despite the flight plan requirement to maintain an altitude at 17.000. The engines were then manually reduced under the minimum maneuvering speed and the autopilot set to 14.000. Despite the Ground Proximity Warning System, the plane kept descending until impact. It is yet unclear why the pilots set autopilot on 15.000 despite the mountainous area demanding a minimum safe altitude of 15.500 feet.

Iran’s accident investigation bureau (AIB) also stated that the pilot had medical restrictions to flight that were not taken into account by Aseman Airlines.

Another factor that could have had an influence in the crash is ice. The flight data recorder shows that the crew activated the anti-ice system. The ATR72 has precedent of ice-related accidents. The crash of the flight 4184 American Eagle on October 31, 1994, even convinced American companies to stop using the ATR72 in icy regions, despite model modification introduced by the manufacturer after the accident. In Aseman’s case, the accumulation of ice on the plane had led it to stall.

However, that first report is not final and the AIB declared it would need more time to give a final conclusion.