Flight Overview
The aircraft, carrying two pilots and seven passengers, operated a flight from Stuttgart to Toronto with scheduled stops at Shannon, Keflavik, and Frobisher. The flight proceeded routinely until Keflavik. After engine start at Keflavik, the aircraft remained on the ground for 18 minutes before takeoff. Departure occurred at 2131Z on February 27. The flight was conducted at Flight Level 390 against a 30-knot wind component, using a GNS-200 onboard navigation system.
Navigation Difficulties
Navigation was satisfactory until 2352Z, when the aircraft was 285 nautical miles east of Frobisher. At that point, the GNS-200 system became unusable for ten minutes due to a dropout of signals from the very low frequency ground stations on which it depended. The aircraft was tracked by a military radar network until it neared the Canadian coast. Near the coast, the aircraft made a left turn of approximately 20 degrees but did not subsequently turn back to the right toward Frobisher. Radar surveillance was not continued beyond that point.
Descent and Communication
The main high-power non-directional beacon at Frobisher (FY-206 kHz) went off the air at 0010Z and was restored at 0059Z. The standby transmitter failed to operate. At 0013Z, an ATC descent clearance was passed to the aircraft through Frobisher Aeradio; no information was included regarding the status of the radio navigation aids at Frobisher. The clearance was acknowledged at 0014Z, and a descent was commenced. At 0025Z, the flight reported that the radio beacons and DME signals were not being received. The aircraft was at relatively low altitude by then and lost radio contact with Frobisher.
Accident and Findings
At approximately 0040Z, a small jet aircraft, believed to be CF-BRL, was observed circling once at low altitude over the radio beacon at Brevoort Island, 120 nautical miles east of Frobisher, and then departing in the direction of Frobisher. At 0050Z, an overflying airline jet contacted CF-BRL and learned it was at 4,500 feet above sea level. The pilots reported being lost and asked whether the Frobisher beacons were being received. Shortly thereafter, they reported receiving the Frobisher radio range station (FB 263 kHz) and altering course toward it, stating they were low on fuel. At 0056Z, the pilot announced that both fuel lights were on and that they were starting down from 4,500 feet. The aircraft struck the side of a hill at 0058Z. The wreckage was found 120 kilometers southeast of the destination airport. All nine occupants were killed.
Probable Cause
The official findings identified the following: During an attempt to locate Frobisher Airport, the aircraft fuel was exhausted by 30 minutes of low altitude maneuvering. The descent from cruising altitude was made using navigation information from the on-board GNS system; the crew were unaware that this information was erroneous. The main non-directional radio beacon at Frobisher was off the air during a critical phase of the flight; the crew were not informed of this outage prior to commencement of descent. The radio beacon transmitter that failed had been fitted with a 40-ampere circuit breaker rather than a 45-ampere circuit breaker specified. The standby radio beacon transmitter failed to operate because of a faulty interlock switch system. The Frobisher radio range station was operating and suitable for use as a homing beacon; it was not approved for use as a radio range and was not listed on the appropriate Canadian flight navigation charts. A Notice to Airmen (Notam) issued in August 1973 stated that the Frobisher radio range would be decommissioned 'in approximately two months'; this Notam was still valid at the time of the accident. The flight as planned did not comply with the requirements for fuel reserves as expressed in Air Regulation 549.