Accident Details
The aircraft, registered EP-ABA, departed Mehrabad Airport on 16 April at 0228Z on a charter flight to Yazd and Bandar Abbas. The same day, the return flight reached Shiraz, where an overnight stop was made. On 17 April, EP-ABA left Shiraz at 0245Z to pick up four passengers at Marvdasht. At 0525Z, it departed Marvdasht on a direct flight to Mehrabad Airport, Tehran, with an estimated time of arrival (ETA) of 0800Z.
Last contact was made with Esfahan at 0630Z, reporting the aircraft’s position as 20 miles east of Esfahan, under visual flight rules (VFR) at flight level 150, with an ETA of 0800Z at Mehrabad. This was the final communication received from the aircraft.
Wreckage Discovery
On 19 April, authorities at Mehrabad Airport were informed that the aircraft had crashed on a mountain located 40 km south of Ardestan and 18 km west of Zafarkand Village. The pilot and four passengers were killed, and the aircraft was destroyed.
Probable Cause
The official investigation determined that the pilot was unexpectedly confronted with severe carburetor icing conditions. A loss of engine power from this icing impelled the pilot to descend through the cloud layer, where possibly the icing conditions became considerably worse, rendering quick melting of the carburetor ice problematic. The already serious situation intensified due to breaking cloud over mountainous terrain under conditions of bad visibility. In an effort to avoid the mountain barriers, the pilot endeavored to fly through a narrow gorge and a visible gap at the top. However, due to greatly diminished power from the persistent effects of carburetor icing, combined with imposing turbulence and downdraft effects in the crest area, the attempt failed. The aircraft first struck a protruding rock formation, which presented a further great obstruction at the most critical point of passage.