Aviation Safety Letter 2/2004

From The Investigator's Desk: Navigational Error - Convair 580

An Aviation Safety Advisory from the Transportation Safety Board of Canada (TSB)

On 18 June 2003, while on a ferry flight to New Zealand, a Convair 580 aircraft inadvertently deviated substantially to the east of its track and the crew became lost. Two global positioning systems (GPS) were in use as the sole source of navigation. The aircraft was located and provided with navigational assistance by a United States Air Force (USAF) C 141 aircraft. While the aircraft landed safely in Gisborne, N.Z., only about 359 lbs of fuel remained, sufficient, for only a few minutes of flight. The investigation (A03F0114) is ongoing.

In accordance with standard aviation safety procedures and practices, the Company Operations Manual (COM) Section 3 A - International Long Range Procedures contains procedures to be utilized when conducting operations in oceanic airspace. Section 3 A.2.1 - Pre-flight, mandates in part that during the pre-flight check of the long range navigation system (LRNS) the flight crew shall enter and confirm the planned route of flight. The section goes on to state:

"If not stored as a standard route, waypoints for Operational Flight Plan (OFP) route must be entered into the GPS. Whether stored or not, both the pilot flying (PF) and pilot not flying (PNF) will verify the entered route during the pre-flight checks prior to departure confirming both waypoint designator and LAT/LONG of the waypoint."

COM Section 3 A.2.3 - Waypoint Passage, mandates in part that approaching each en route waypoint the crew shall verify present position and confirm next waypoint, desired track, and distance.

The investigation to date has revealed that the last six waypoints of the last leg had been entered with west longitude coordinates, instead of the correct east longitude coordinates. For the three legs between Canada and New Zealand, none of the waypoints as entered in the two GPS were verified against the computer-generated flight plan. The bearings and distances between waypoints were not checked either. The incorrect entries remained undetected until the flight path substantially deviated and the crew became lost.

A search of the TSB Aviation Safety Information System (ASIS) database revealed 174 instances of navigational errors between 1 January 1980 and 1 November 2003, of which 18 involved confirmed and 20 involved suspected data entry errors into LRNS.

Although the aircraft landed safely, the fact that the crew did not detect the waypoint position errors resulted in the fuel being almost totally exhausted and there was a potential for serious injury to the crew members. Historical data indicates this is not an isolated occurrence of this type. The procedure in the COM requiring cross checking of GPS data against hard copy flight plan data provided a defence against the risk of the crew failing to detect GPS data entry errors. Unfortunately, this defence was not used.

The advisory letter concluded by suggesting that Transport Canada (TC) may wish to use this occurrence to remind flight crews of the risks of not verifying waypoint data when using navigation equipment such as GPS.

In its response to the Advisory, TC stated that it believes that the regulatory provisions relating to long range navigation are adequate and that if the flight crew in this instance had followed their company's Operations Manual (OM), the error would have been detected and corrected. Transport Canada also believes that safety education and promoting adherence to Standard Operating Procedures (SOP) will be more effective than regulatory action in reducing the risks associated with navigational data entry. To this end, this Aviation Safety Advisory is the subject of this article in the Aviation Safety Letter. Later this year, TC will consider the need for further promotional activity.

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