Iranian investigators have yet to disclose why a Boeing 707-320C attempted to land at a general aviation airport with a short runway, during which it careered into a residential area.
The aircraft, part of the Iranian air force fleet, overran runway 31L on 14 January and crashed through a perimeter wall located almost immediately beyond the runway surface.
It came to rest in a residential area, having travelled some 300m beyond the end of the displaced opposite-direction threshold of runway 13R.
Iran’s official aeronautical information publication lists Fath airport as being located at an elevation of around 4,000ft, with the length of 31L given as 1,300m.
The distance between the displaced thresholds is around 1,000m.
Investigators have not confirmed the landing weight of the aircraft, which was carrying only a light crew load.
But Boeing performance data for the 707-320C indicates that, even at a minimal landing weight of just over 70t the aircraft would require – in dry conditions – a runway distance of close to 1,500m at 4,000ft elevation.
Fath airport, situated 10km south-east of the larger Karaj Payam airport, is used for general aviation and helicopter traffic.
Investigators have not explained why the 707 landed at Fath, and whether the crew deliberately selected the airfield.
But the larger Payam airport’s main runway 30 – which is some 3,660m long – has a similar alignment to that of Fath’s runway 31L and the two runways’ centrelines almost coincide.
This raises the possibility that the crew misidentified Fath as Payam.
Iran’s Civil Aviation Organisation recently detailed an incident involving a Taban Airlines Boeing MD-88, bound for Payam, which twice attempted an approach to Fath following a service from Mashhad in November last year.