Swedish investigators have revealed how an inquiry into an Iranian Airbus departure incident at Stockholm Arlanda was delayed by several months as a result of US Government sanctions against Iran.

The Iran Air A300-600's left-hand General Electric CF6-80 engine suffered a violent internal failure 300m (980ft) into the twinjet's take-off roll on runway 19. The A300 veered to the left and came off the runway, becoming embedded in soft ground.

But while the incident occurred on 16 January 2010, the Swedish investigation commission SHK states that the examination of the engine could not begin until November.

"Due to the US embargo on the state of Iran, there was however a considerable delay, whereby Lufthansa and General Electric were obliged to request dispensations to be issued by the USA in respect of the investigation," it says.

Lufthansa Technik had been recruited to the inquiry as an authorised servicing company for the affected powerplant.

Initial indications suggest that the failure sequence began in a small space between the rear of the diffusor housing and the first-stage turbine disk.

"Parts were thrown out into the primary air duct and struck the first-stage turbine blades," says SHK. "Parts that were broken off from these blades, in turn, damaged the blades and guide vanes in the subsequent turbine stages in an expanding cone whereby major resultant damage was caused."

SHK states that it is performing metallurgical analysis of parts including shattered fragments of the aft diffuser seal, which had been previously repaired.

The incident occurred in wintry conditions and the runway was wet, with frost. As the A300 veered left, the crew reduced the power on both engines and applied full rudder about one second after the failure. Braking was also applied, but no reverse thrust.

Information from the flight-data recorder shows the left engine's speed dropped from 102% of N1 to 40% of N1 in just two seconds, whereas the right engine - which was throttled back manually - took 12 seconds to fall to the same level.


Source: Air Transport Intelligence news