What happened
On 2 January 1998, a Cess0421C, registration N6315X, was performing a private VFR flight from Dublin to Denham Aerodrome. During the landing phase on Runway 06, the aircraft touched down at approximately 90 kt with a 15 to 16 kt crosswind. The aircraft was at an operating weight of 6,650 lb.
Upon applying the brakes, the aircraft began to slide along the wet asphalt. Realising the aircraft would not stop within the remaining runway length, the pilot deployed the flaps and shut down the engines. The aircraft subsequently overran the end of the paved surface at an estimated speed of 19 kt, eventually coming to a halt on a minor public road located beyond the aerodrome boundary. There were no injuries to the pilot or the two passengers on board, though the aircraft sustained severe damage to the right wing, flap, aileron, landing gear strut, propeller, and tailplane.
The investigation
The investigation examined the environmental conditions and the aircraft's performance capabilities. At the time of the accident, a low-pressure system was moving northeast, bringing rain or drizzle to the area. The surface wind was recorded at 300 degrees at 20 kt, with gusts reaching 25 to 30 kt.
Technical analysis of the aircraft's performance data was conducted. For an operating weight of 6,600 lb, the manual specifies a target speed of 96 kt at 50 feet. While the manual provides ground roll distances for a dry runway, it does not provide specific corrections for wet surfaces. Notably, the calculated hydroplaning speed for the aircraft, assuming standard tyre pressure of 80 psi, was determined to be 80.5 kt.
Findings
- The aircraft landed on a wet runway surface during periods of rain or drizzle.
- The pilot experienced a loss of braking effectiveness, which may have been caused by aquaplaning.
- The aircraft's calculated hydroplaning speed of 80.5 kt was lower than the touchdown speed of 90 kt.