Background
A Douglas C-54A passenger aircraft was operating a non-scheduled international flight from Manston, England, to Perpignan, France. The aircraft took off at 17:31 hours GMT and climbed to cruising altitude FL90.
Flight History
At 19:48 hours, the crew contacted Marseille Control and reported crossing the FIR boundary. At 20:25 hours, they reported over Mende at FL90, estimating abeam Montelimar at 20:44 hours. Marseille Control questioned this, noting Montelimar is nearly on the same parallel as Mende. The aircraft then corrected to abeam Montpellier at 20:44 hours and estimated arrival at Perpignan at 21:10 hours. Calculation suggested the ETA was inconsistent without a speed reduction or approach time allowance. At 20:33 hours, Marseille Control requested ETA confirmation; the flight replied 22:10 hours then corrected to 21:10 hours.
At 20:43 hours, the aircraft reported abeam Montelimar instead of Montpellier and estimated reaching Papa 3 (entry point at Narbonne) at 20:52 hours, making the 21:10 hours ETA even less plausible. At 20:50 hours, the aircraft corrected its ETA over Papa 3 to 20:51 hours, confirmed Perpignan ETA at 21:10 hours, and requested descent. Marseille Control cleared descent to FL70 and directed to contact Perpignan Approach.
At 20:52 hours, the aircraft contacted Perpignan Approach, confirmed ETA, and reported descending to FL70. Perpignan Approach provided QFE, QNH, and temperature, asking for a call on passing FL70. At 20:55 hours, the aircraft reported approaching FL70 descending to FL50; five minutes later it reported approaching FL50. Perpignan Approach asked if the aerodrome was in sight; the aircraft replied "Roger, we'll advise, field in sight." Perpignan Approach then instructed to report downwind for runway 33 and reported calm wind.
At 21:04 hours, Perpignan Approach asked for flight level; the aircraft reported 4000 ft and stated it would be with them in about five minutes. When asked if it had the field in sight, the aircraft replied at 21:05 hours "Yankee Kilo negative at this moment." The controller repeated in a questioning tone, and the aircraft replied "that is affirmative," which the controller misunderstood as having the field in sight. The controller again instructed to report downwind. A few seconds later, the aircraft requested QDMs (magnetic bearings); Perpignan Approach asked for repetition, but no further replies were received.
The Accident
The aircraft impacted a mountain in the Pyrenees at an elevation of 1160 m. The wreckage was found in a ditch at 940 m on the slope of Mount Canigou, after the aircraft struck the Dent du Lion with one wing. The aircraft was totally destroyed, and none of the 88 occupants survived.
Investigation Findings
The Commission determined the accident resulted from a collision with the mountainside, directly due to a series of crew errors: failure to use all available radio navigation means, error in dead reckoning, descent from an inadequately identified point, failure to observe safe altitudes on the company flight plan, and possible identification mistakes via visual ground reference. The commission also suggested that this irrational conduct could be explained by carbon monoxide intoxication from a defective heating system. Additionally, misunderstandings between the aircraft and Perpignan controller due to language difficulties and lack of standard phraseology, along with failure to check the aircraft's magnetic bearing using D/F equipment at 20:55 hours, were considered possible aggravating circumstances.