What aircraft was involved and where did it happen?

The accident on 2017-04-21 involved a Cessna 350 Corvalis, registration OK-WSM, at LKVP, CZ.

What was the probable cause of the accident?

The accident was caused by a loss of directional control during the takeoff roll, resulting from the pilot's failure to perform necessary pre-flight preparations—specifically the removal of frost from the aircraft—and the failure to utilize the correct flap settings for the runway conditions.

Loss of Control During Takeoff at Velké Poříčí Aerodrome

A Cessna 350 Corvalis veered off the runway and sustained significant damage after the pilot failed to clear frost from the aircraft and used incorrect flap settings during takeoff.

What happened

On April 21, 2017, at approximately 04:35 UTC, a Cessna 350 Corvalis, registration OK-WSM, was attempting a takeoff from the grass runway 27R at Velké Poříčí Aerodrome (LKPV). The aircraft had been parked outside the hangar overnight, leaving it exposed to freezing temperatures.

During the takeoff roll, the aircraft initially drifted slightly to the left due to propeller torque. As the aircraft reached a speed of approximately 60 knots, it experienced a sharp deviation to the left of about 30 degrees. The pilot attempted to correct the deviation using the rudder but was unable to maintain the centerline. The pilot subsequently decided to abort the takeoff and applied the brakes.

During the aborted takeoff, the aircraft veered off the airfield perimeter, crossing a furrow in the ground. While traversing this uneven terrain, the nose gear collapsed, leading to a skid and subsequent impact of the aircraft's nose and wings with the ground. There were no injuries to the pilot.

The investigation

The ÚZPLN investigation examined the aircraft's condition, the meteorological environment, and the pilot's actions. Investigators found that the aircraft was covered in frost and rime ice, which had not been removed prior to departure. Furthermore, the investigation established that the pilot performed the takeoff with the flaps in the retracted position, rather than the 12-degree takeoff setting required for short-field operations as specified in the flight manual.

Physical evidence from the runway showed no signs of braking by the pilot, and the tracks left in the frozen grass indicated the aircraft was traveling at a significant speed when it deviated. The investigation also noted that the pilot had not flown this specific type of aircraft regularly, with his last flight on the model occurring several months prior.

Findings

The aircraft was operated with accumulated frost and ice on the airframe, which negatively impacted takeoff performance.
The pilot failed to extend the flaps to the recommended takeoff position.
The pilot did not sufficiently compensate for the leftward yawing moment caused by propeller torque during the takeoff roll.
The pilot overestimated his ability to control the aircraft under the prevailing conditions and failed to abort the takeoff in a timely manner.
The takeoff attempt was conducted on a frozen, slippery grass surface that required a much longer runway than was available due to the improper configuration and icing.