Investigation Summary
The accident was triggered by a non-essential detour requested by a passenger to view the SS Norway. To facilitate the sightseeing, the Proteus crew cancelled their IFR flight plan and switched to VFR, which shifted the responsibility for separation from Air Traffic Control to the pilots (See and Avoid). During a 360 degree turn around the ship, the Beechcraft's cockpit ergonomics and the blind spots created by the turn prevented the crew from seeing the Cessna 177, which was also operating in the area. The Cessna was not visible on the Lorient approach controller's radar because its transponder was switched off, a practice that was technically permitted under contemporary French VFR regulations. Furthermore, the Beechcraft's TCAS had been uninstalled because the specific model was not yet approved for operation in France. The investigation noted that if the Cessna's transponder had been active and the Beechcraft's TCAS had been installed, the collision would likely have been avoided by approximately 300 feet.
Final Conclusions
The BEA concluded the primary causes were the Proteus crew's decision to cancel IFR for a sightseeing detour, their failure to maintain an effective visual lookout during the turn, and the Cessna pilot's decision to fly with an inactive transponder. The lack of TCAS on the Beechcraft and the Cessna's invisibility to ground radar due to the transponder status were major contributing factors.
Video Analysis
Mid-air Collision of Proteus Airlines Flight 706 and a Cessna 177 — Analysis of the 1998 collision over Quiberon Bay caused by a flight path deviation to view a cruise ship. The investigation highlights visual lookout failures and the impact of an inactive transponder.
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Systems & Failure Modes
Transponder
The Cessna's transponder was inactive, which prevented ATC from seeing the aircraft and relaying traffic information to the Beechcraft.
TCAS
The Traffic Collision Avoidance System on the Beechcraft had been uninstalled; if active, it could have provided a resolution advisory even with the Cessna's transponder off (if the Cessna had a Mode C transponder) or if both were equipped.
See and Avoid
The primary VFR separation method failed due to cockpit blind spots and the focus of the crew on the ocean liner.
Interesting Facts
- 01The Cessna 177's transponder was switched off, making it invisible to secondary radar.
- 02The Beechcraft 1900D's TCAS had been removed because it was not yet approved for use in France.
- 03The Proteus crew cancelled their IFR flight plan specifically to perform a sightseeing detour.
- 04The collision occurred in clear weather conditions under Visual Flight Rules.
- 05All 14 people on the Beechcraft and the lone pilot of the Cessna were killed.
Safety Actions & Advisories
IFR Cancellation Policy
The BEA recommended that pilots should only cancel IFR flight plans when absolutely necessary for the safety or completion of the flight, rather than for convenience or sightseeing.
Transponder Usage
Regulations were reviewed to clarify and encourage the use of transponders by VFR aircraft to ensure visibility to ATC and other TCAS-equipped aircraft.