What happened
On Thursday, August 21, 2003, at 18:30, a Cessna 172 Q Skyhawk, registration G-YSPY, was performing a local flight at Avranches Aerodrome. During the landing sequence, the pilot executed a normal approach and touchdown. As the aircraft taxied along the unpaved runway, the pilot retracted the flaps and applied braking. During this rollout, the aircraft encountered a sandy embankment located in the middle of the runway. The impact caused the aircraft to nose over, eventually coming to rest on its back. The pilot and one passenger were able to evacuate the aircraft following the accident. There were no fatalities among the two occupants.
The investigation
The investigation focused on the runway conditions at Avranches, an aerodrome located in the tidal flats of the Mont Saint-Michel Bay. The terrain at this location consists of short grass growing over a mixture of sand and silt known as tangue. This environment is subject to significant changes due to high tides, which frequently redistribute materials across the airfield.
While the aerodrome typically undergoes maintenance to replenish the runway with tangue early in the year to allow grass to regrow before the busy season, the investigation found that a significant lack of rainfall during the preceding period had prevented the grass from establishing itself. Consequently, the newly deposited material remained exposed and unstable. At the time of the accident, no specific access restrictions had been implemented for the airfield despite these conditions.