What happened
On 17 June 2003, a Convair 580, registration C-GKFJ, was conducting a ferry flight from Pago Pago, American Samoa, to Palmerston North, New Zealand. The aircraft, operated by Kelowna Flightcraft Air Charter Ltd., was being delivered to new owners in New Zealand. During the flight, the crew encountered heavy thunderstorm activity, which necessitated several deviations from the planned track.
After passing the waypoint AUTEL, the aircraft began to deviate significantly to the east of its intended path. The crew eventually became lost, approximately 300 nautical miles east of Gisborne, New Zealand. As fuel levels plummeted, the crew realized they were unable to establish communication with air traffic control via VHF or HF radio, partly due to the ongoing thunderstorm activity. With less than 2,000 pounds of fuel remaining, the crew declared a Mayday.
A US Air Force C-141 aircraft responded to the distress call and used TCAS to locate the drifting aircraft. Following track corrections provided by the C-141, the crew managed to navigate toward Gisborne. The aircraft landed safely at Gisborne with approximately 360 pounds of fuel remaining, leaving only minutes of flight time left.
The investigation
The investigation focused on why the aircraft deviated so far from its intended track despite the crew having a paper flight plan. It was discovered that the last six waypoints of the flight leg had been entered into the aircraft's two GPS units with west longitude coordinates instead of the correct east longitude. This error caused the GPS to direct the aircraft toward positions east of the 180° meridian.
Investigators also examined the configuration of the Apollo 820 GPS units. At the time, North American data cards were inserted in both units. This had the effect of deactivating the internal databases for airports and VORs, leaving the crew only with the manually entered (and incorrect) user-defined waypoints. The crew was unaware that removing these cards would have reactivated the internal New Zealand databases, which could have helped them identify their true position.
Findings
- The primary cause of the navigational error was the incorrect entry of longitude coordinates (west instead of east) for the final six waypoints into the GPS units.
- The flight crew failed to verify the GPS data against the printed flight plan during pre-flight checks or during waypoint passage, which would have revealed the discrepancy.
- The use of North American data cards deactivated the GPS internal databases, limiting the crew's ability to use known landmarks or airports for position verification.
- The crew lacked specific training on the Apollo 820 GPS and had not received a briefing on long-range navigation procedures for this specific flight.
- Heavy thunderstorm activity and the resulting need for course deviations likely masked the growing discrepancy between the GPS track and the intended flight plan.