Iranian investigators have determined that poor maintenance procedures, allowing contamination of hydraulic lines, led to a gear-up landing by a Qeshm Air Fokker 100 earlier this year.
The aircraft had departed Tehran Mehrabad for Mashhad on 16 February but, some 10nm from touchdown, its crew discovered problems with the left-hand main landing-gear.
It executed a missed approach, says the Iranian Civil Aviation Organisation, and entered a holding pattern while the crew attempted to resolve the problem.
Several attempts to recycle the undercarriage were not successful, says the inquiry, and neither was an effort to use the alternate landing-gear deployment procedure.
A low pass over the airport allowed ground personnel to observe that the left-hand gear was only partly extended, and high-load manoeuvring failed to free it.
The crew declared an emergency and, having remained in the hold to burn fuel, conducted an approach to Mashhad’s runway 31R.
As it landed the aircraft veered off the left side of 31R, coming to rest between the parallel runways, suffering left wing structure and flap damage from ground contact. The landing-gear was also damaged.
Occupants were evacuated from the aircraft. None of the 97 passengers or seven crew members was injured, the inquiry says.
Examination of the hydraulic system has concluded that “foreign pollution” entered while C-check maintenance was being carried out on a restrictor valve and hose from the left-hand landing-gear actuator.
A filter near the valve was damaged, it says, and enabled contaminants to block a downstream nozzle, affecting the landing-gear mechanism.
Investigators say that “insufficient surveillance” of the maintenance operation and a “lack” of experience from Qeshm Air maintenance personnel contributed to the situation.
Qeshm Air had “recently” been authorised by the Iranian authorities to perform C-check work, which had previously been conducted by Iran Aseman Airlines at Mashhad. Qeshm carried out the C-check at the facility of maintenance firm Farsco.