With 166 souls onboard an Airbus A310-308 was operating a scheduled flight from Tehran (Iran) to Istanbul (Turkey) on this day in aviation history 2015.
The aircraft in its final position (Source; www.airporthaber.com © Unknown)
After an unremarkable flight, the aircraft approached Runway 5 at Istanbul Atatürk International Airport in good weather;
Wind - Variable at 02 Knots
Temperature - 10ºC
Humidity - 6ºC
QNH - 1031 hPa
Following an uneventful landing, the crew contacted the Ground Controler at 06.28 UTC for their taxi instructions. Unbeknown to the crew, a leak in the Yellow Hydraulic System caused the pressure in the brake accumulators of that system to deplete. Normal braking action was not affected, as the normal braking system operates on the green hydraulic system. After several taxi route instructions, the aircraft approached its parking stand S6, across from terminal A. Upon reaching the correct parking position the crew stopped the aircraft using the normal brakes, followed by applying the parking brake. However, with the yellow hydraulic system depleted the parking brake did not activate. without the crew noticing the aircraft started rolling forward, colliding with a concrete barrier with a metal railing. This caused the nose landing gear to fail, and be folded backwards, this resulted in the nose section of the aircraft collapsing onto a bus, driving on the road opposite the barrier on a recessed road. At 06.37:57 UTC the crew contacted the Ground Controler stating;
"We have now problem with the breaking system. The aircraft not stopped at the system and unfortunately with the landing gear is collapsed, request safety service to be check up the aircraft"
Close-up of the nose landing gear folded backwards
(Source; www.airporthaber.com © Unknown)
The emergency services responded, and as requested assessed the situation. It was deemed not necessary to perform an emergency evacuation of the aircraft. The passengers were informed by the crew that a hydraulic failure had occurred. There were no injuries amongst the passengers and crew of the Airbus A310, also the bus driver escaped the accident without injuries. Both the Airbus and the Groundbus sustained serious damage. The passengers disembarked the aircraft via the righthand rear service door and were bussed to the terminal. After temporary repairs were completed the aircraft was ferried back to Tehran from Istanbul on the 26th of February 2016. It returned to service 4 weeks later on the 3rd of March 2016.
The accident was investigated by the UEIM (Turkish Accident Investigation Board). In their report (available in Turkish at the end of this blog) they concluded that the probable causes for the accident were:
After successful landing on runway 05 during taxi an intense leak in the yellow hydraulic system occurred causing the loss of the brake accumulators.
The aircraft continued taxiing with the green hydraulic system in normal braking mode.
The crew can not monitor the availability of the parking brake mode provided by the yellow system, and the pressure in the park brake accumulators can not be adequately observed.
After arriving at the stand the aircraft was stopped with the green hydraulic system and park brake applied.
The main reason for the accident was the cockpit crew not applying brake pedal pressure as set in the standard operating procedures when the aircraft began to move despite the parking brake being set.
A contributing factor was a defect in the PBOV (parking brake operating valve).
The aircraft in its final position (Source; www.airporthaber.com © Unknown)
The accident report (in Turkish);
** Editorial note **
V2 Aviation - Training & Maintenance has not been able to obtain an investigation report in English on this accident. This blog is therefore based on several internet sources. Should there be inconsistencies in the blog don't hesitate to get in touch with us. There are two possibilities to do that, via the comments function at the bottom of this page or via the contact page of the website.