Dutch Safety Board: SID confusion causes serious airprox event

Citation N666MX at Rotterdam, November 2006 and B737-700 PH-XRV (Photos: Harro Ranter)

The Dutch Safety Board published the investigation report into a serious airprox event in November 2006. A Cessna Citation departing from Rotterdam Airport (EHRD) and an approaching Boeing 737 had a traffic conflict due to the misconception of ATC that the Cessna Citation followed a different standard instrument departure procedure than it had actually been cleared for.

N666MX, a Cessna 560XL Citation Excel, executed a charter flight from Rotterdam Airport to Cannes Mandelieu (LFMD). The aircraft was cleared by the tower controller for a “Woody1B” departure after take-off from runway 24. When N666MX was handed over to Rotterdam Approach, the approach controller assumed that the aircraft was cleared for a “Refso1B” departure and would fly in westerly direction. Approach instructed N666MX to climb to FL50 to pass overhead the inbound PH-XRV.

PH-XRV, a Transavia Boeing 737-7K2, came from a westerly direction. It was instructed to descend to FL45 and to
fly to beacon RTM. When the aircraft was handed over to Approach, it was cleared to descend further to 3000 feet for a radar vectors approach to runway 24 of EHRD. Because N666MX turned left to follow the “Woody 1B” departure and PH-XRV levelled off at about 5100 feet instead of 3000 feet, the separation between both aircraft diminished. Although several clues were available, the approach controller did not notice the impending traffic conflict.

When N666MX turned to the left to follow the “Woody1B” departure, the airplane would cross the intended flight path of PH-XRV. Both aircraft received a TCAS2 resolution advisory (TCAS RA); PH-XRV was instructed to climb and N666MX was instructed to descend by TCAS. Almost at the same time the conflict was noticed by the approach controller who instructed N666MX to turn right to heading 330.

As a result of all instructions, (TCAS RA and the instructions of the approach controller) the conflict was solved and both aircraft continued the flight without problems. The closest distance between both aircraft was 0.4 nm horizontally and 900 feet vertically. The crew of both aircraft had visual contact with the other aircraft during the conflict.

The most probable cause of this serious incident was the misconception of approach control about the standard instrument departure flown by N666MX. A possible mid air collision was prevented by TCAS and the instructions of approach control.

Contributing factors in this occurrence are:

  • The non optimal physical and mental condition of the controller possibly caused by fatigue.
  • The suboptimal conditions for controllers from Rotterdam Airport to perform approach control duties in the common IFR room at Schiphol Oost.
  • Not reacting of the ATC instruction to descend to 3000 feet by the crew of PH-XRV.
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