Aircraft and Flight Details
The aircraft involved was a Cessna 421C, registration N6315X, built in 1981. It was powered by two Continental GTSIO-520-D piston engines. The flight was a private VFR journey from Dublin, Ireland, to Denham Aerodrome in Middlesex, United Kingdom. On board were the pilot, who held a US Commercial Pilot's Licence (age 39, with 1,600 hours total experience, including 650 hours on type), and two passengers. No injuries were reported.
Accident Narrative
Landing on the wet, hard-surfaced Runway 06 at Denham, the pilot reported an operating weight of 6,650 lb and a normal approach speed of 90 kt. The touchdown occurred just before the runway designator numbers, with a crosswind of 15 to 16 kt. Upon applying the brakes, the aircraft began to slide. When it became apparent that the aircraft would not stop within the remaining runway, the pilot raised the flaps and shut down the engines. The aircraft overran the paved surface at an estimated speed of 19 kt and came to rest on a minor public road beyond the aerodrome boundary. The occupants exited the aircraft normally.
Weather and Runway Conditions
The pilot noted that the surface wind backed from 030° at 20 kt during approach to 360° at 20 kt at landing. A meteorological aftercast indicated a depression of approximately 975 mb centered over The Fens, moving northeast, producing occasional rain or drizzle at Denham. Cloud cover was scattered at 500 ft and 1,200 ft, broken at 3,500 ft. Visibility was 15 to 20 km, mean sea level pressure was 983 mb, surface wind was from 300° at 20 kt gusting 25 to 30 kt, and temperature was +6°C. Runway 06 at Denham is asphalt, 779 m in total length with a displaced threshold giving a Landing Distance Available of 701 m.
Performance Data
According to the Cessna 421C Pilot's Information Manual, at an operating weight of 6,600 lb and using full flap with maximum effective braking on a dry runway, the ground roll is approximately 600 ft (183 m) and the total distance to clear a 50 ft obstacle is about 2,170 ft (661 m). No corrections are provided for a wet runway surface. The calculated hydroplaning speed for the normal tyre pressure of 80 psi is 80.5 kt. The pilot considered that aquaplaning may have occurred on the wet surface.