Accidents

Turkish Airlines A330

Inaccurate navigation data, relating to runway location, led to touchdown with left main gear off the paved surface. Aircraft written off.

During March 2015, an Airbus A330-303, operated by THY Turkish Airlines, suffered a runway excursion  accident upon landing at Kathmandu-Tribhuvan Airport (KTM), Nepal.

Flight TK726 was a regular passenger service from Istanbul-Atatürk International Airport (IST) to  Kathmandu, Nepal. The flight was the first international flight to arrive that morning. After descending  from cruising altitude, it entered a holding pattern. It was subsequently cleared for a VHF Omnidirectional  Range (VOR) / Distance Measuring Equipment (DME) approach to Runway 02.

This approach was abandoned at about the Missed Approach Point at 1DME and the aircraft performed a  go around. The aircraft circled and positioned for a second approach to Runway 02. The aircraft touched  down to the left of the runway centre line with the left hand main gear off the paved runway surface. It ran  onto soft soil and the nose landing gear collapsed. Following the accident the aircraft was written off.

The aircraft touched down to the left of the centreline because the Flight Management Guidance System  (FMGS) navigation database contained threshold coordinates for a proposed displacement of the Runway  02 threshold. This was later withdrawn through a Notice To Airmen (NOTAM), but had not been updated  by the airline in the database. Additionally, the coordinates that were initially published were inaccurate,  causing the threshold coordinates to be offset to the left of the actual threshold. This had been noticed  and reported by a previous Turkish Airlines flight on March 2. The changes had not been performed by the  time TK726 landed at Kathmandu.

Among the safety recommendations stated in the accident report were:

• “The operator must ensure that the correct navigation data are uploaded on Flight Management Guidance System”;
• “The operator should establish a system of verifying the quality of charts prepared by the service provider”;
• “The operator should establish a system of checking the validity of the Flight Management System database”; and
• “Civil Aviation Authority of Nepal must ensure that raw aeronautical information/data are provided by the aerodrome authorities taking into account of its accuracy and integrity requirements for  aeronautical data as specified by ICAO Annex 15 and its Aeronautical Information Service Manual.”

This incident highlights the importance of three Data Properties, specifically: accuracy; timeliness; and  verifiability. All of these apply to data describing the runway’s location.

Links

• http://www.tourism.gov.np/downloadfile/TURKISH_AIRLINE_Final_Report_finalcopy4.pdf
  (accessed 29 November 2017 — no longer available from this location, but on 9 January 2019 was still available  through archive.org).