What happened
On November 15, 1978, a Cessna 310 R, registration HB-LHK, was conducting an IFR flight from Zurich to Toussus-le-Noble. Due to heavy fog obscuring the Paris region, the pilot decided to divert to Reims-Champagne. During the diversion, air traffic control instructed the pilot to proceed to Reims-Prunay under VFR conditions following an ILS approach at Reims-Champage.
As the aircraft transitioned through a layer of fog, it encountered terrain at the Mont Berru hills. The impact resulted in the deaths of the pilot and two passengers, and the aircraft was destroyed by a post-crash fire.
The investigation
The investigation examined the sequence of communications between the pilot and various air traffic control centers, including Paris-Information and Reims Approach. Investigators established that the pilot was unaware of the specific requirements for the Reims-Prunay arrival and lacked the necessary documentation for that airfield.
Crucially, the investigation looked into the altimetry settings used during the final approach. While the controller used QFE references, the pilot used the term QNH, leading to a likely confusion between the two settings. The investigation also reviewed the meteorological conditions, noting that while conditions were sufficient for a VFR departure from Reims-Champagne, they had degraded rapidly, falling below the published minimums required for the specific procedure being used to reach Reims-Prunay.
Findings
- The direct cause of the accident was a collision with terrain while flying at a low altitude within a fog layer.
- Significant communication ambiguities occurred during the diversion process, specifically regarding the requirement to switch to VFR flight.
- A likely confusion between QFE and QNH altimetry settings prevented the pilot from maintaining a safe altitude above obstacles.
- The pilot had not canceled the original IFR flight plan, which obscured the clarity of the transition to VFR flight.
- Air traffic controllers utilized a flight pattern that, while common, did not align with published procedures and was incompatible with the existing terrain and weather.
- Language barriers, specifically the use of English, contributed to difficulties in transmitting vital information accurately and timely.
- The controller's attempt to assist the pilot by deviating from established regulations contributed to the unsafe flight environment.