Iranian investigators probing a gear-up landing involving an Iran Air Fokker 100 believe a failure in one of the aircraft’s two main hydraulic systems led to the accident.
The aircraft had been operating flight iR215 from Qeshm on 19 March, and had been conducting an approach to Tehran Mehrabad at around 19:07 when the crew discovered that the landing-gear would not deploy.
Iran’s Civil Aviation Organisation states that the System 1 hydraulic circuit on the aircraft had failed. This system is connected to various flight-control surfaces but is also linked to the landing-gear and nose-wheel steering.
The aircraft (EP-IDG) entered a holding pattern to burn fuel while the crew attempted to free the undercarriage, but only managed to deploy the nose-gear.
As a result the aircraft was forced to carry out a landing on Mehrabad’s runway 29L with its main landing-gear retracted.
It stopped safely on the runway at 21:35, with emergency services preventing the sparks from friction developing into a fire, and passengers were evacuated. There were no injuries among the 24 passengers and nine crew members.
Although the runway was closed, the airport maintained operations by using the parallel runway 29R, says the Civil Aviation Organisation. Using military equipment, recovery personnel moved the aircraft to the southern apron of the airport where it was jacked and inspected.
Investigators state that the aircraft – which was originally delivered to Iran Air new in April 1991 – had logged 49,489h and 51,036 cycles by February this year.
The inquiry has noted that, on 16 March, hydraulic problems were encountered which led to engine tests. It adds that the aircraft was also involved in a subsequent incident in which the aircraft departed Mehrabad but returned to the airport and conducted an overweight landing, before subsequently being returned to service for the Tehran-Qeshm-Tehran flight.
“Technical failure of the hydraulic system occurred again and led to the accident,” says the inquiry.
It states that preliminary examination indicates that mechanical linkages in the system for deploying the landing-gear may have resulted in problems for the pilots when they attempted to use the landing-gear lever in the cockpit.
But the situation requires a full inspection of the landing-gear, it says, adding that the doors of the undercarriage have been badly damaged.
Flight recorders have been retrieved from the aircraft and the inquiry is to be assisted by investigators from the Dutch Safety Board and the UK Air Accidents Investigation Branch, as representatives of the states of design and manufacture of the aircraft and landing-gear.