Courtesy: Dutch Safety Board
Turkish Airlines, Crashed during approach, Boeing 737-800, Amsterdam Schiphol Airport [pdf]
A Boeing 737-800 (flight TK1951) operated by Turkish Airlines was flying from Istanbul Atatürk Airport in Turkey to Amsterdam Schiphol Airport, on 25 February 2009. As this was a Line Flight Under Supervision, there were three crew members in the cockpit, namely the captain, who was also acting as instructor, the first officer who had to gain experience on the route of the flight and who was accordingly flying under supervision, and a safety pilot who was observing the flight. There were also four cabin crew members and 128 passengers on board. During the approach to runway 18 Right (18R) at Schiphol airport, the aircraft crashed into a field at a distance of about 1.5 kilometres from the threshold of the runway. This accident cost the lives of four crew members, including the three pilots, and five passengers, with a further three crew members and 117 passen- gers sustaining injuries.
Shortly after the accident, the initial investigation results indicated that the left radio altimeter sys- tem had passed on an erroneous altitude reading of -8 feet to the automatic throttle control system (the autothrottle). In response to this, the Board had a warning sent to Boeing on 4 March 2009. This asked for extra attention to be paid to the Dispatch Deviation Guide for the Boeing 737-
800, which is a manual of additional procedures and warnings for maintenance crews and pilots to consult before the aircraft is flown. This warning, which was added in 2004, states that with radio altimeter(s) inoperative, the associated autopilot or autothrottle must not be used for the approach and landing. The Board asked Boeing to investigate whether this procedure should also apply during the flight itself. With regard to the content of the Dispatch Deviation Guide, Boeing has answered that a provision such as this did not lend itself for inclusion in a defects checklist in the Quick Reference Handbook – the handbook containing the checklists for normal and abnormal procedures during the flight. On the one hand because a non-normal checklist must be based on a readily identifiable failure that is identified by an alert or a fault-warning, which was not the case with this radio altimeter failure. On the other hand because of the complexity of the fault, it is not practical to develop a non-normal checklist that would address all possible situations. Furthermore incorporating the procedure in the Quick Reference Handbook would unnecessarily remove airplane system functionality. This means that as an aircraft has two identical systems, one system is also
a back-up for the other system. When one of these systems does not work prior to dispatch no back-up system is available and the flight should not be dispatched or the systems should not be used. If however during the flight one of the systems should fail the other system, the back-up, will take over and that is what it is meant for. Not using a system anymore at that moment should be too big a restriction for the operations. On the same date, 4 March 2009, following consultation with the Dutch Safety Board, Boeing did sent a notice to all companies flying with the Boeing 737 regarding the facts of the accident flight, as they were known at that point.
