What happened
On October 17, 1998, a homebuilt PIK-21 Super Sytky, registration OH-XME, was performing its first flight under the control of its owner at Nummelan aerodrome. The aircraft had been constructed by the owners and had completed six previous test flights, all conducted by an experienced test pilot.
During the takeoff from the unpaved portion of runway 22, the aircraft initially exhibited some lateral instability before stabilizing. As the aircraft approached rotation speed, the pilot experienced significant longitudinal instability. The aircraft began to bank sharply to the right and entered a series of unstable oscillations. At an altitude of approximately three meters, the aircraft struck the ground on its landing gear, causing the gear and portions of the fuselage to detach. The aircraft subsequently overturned, and the engine and fuel tank were torn from the airframe. The pilot sustained minor injuries, specifically facial trauma, after striking the instrument panel.
The investigation
The investigation focused on the aircraft's handling characteristics, the pilot's recent flying experience, and the installation of safety equipment. Investigators noted that while the pilot had been briefed on the aircraft's sensitive controls, the degree of sensitivity was much higher than anticipated, with control movements as small as 0.5 cm causing significant response.
Furthermore, the investigation examined the installation of the four-point safety belts. It was discovered that the shoulder harnesses were attached too low on the cockpit bulkhead, near the pilot's hip level. This improper positioning failed to restrain the pilot's upper body, allowing his head to strike the instrument panel during the impact.
Findings
- The immediate cause of the accident was the overcontrolling of the aircraft due to its exceptionally sensitive flight controls.
- The underlying cause was the pilot's lack of recent flying experience and very limited experience operating taildragger-type aircraft, having only flown approximately 2 hours and 50 minutes in the two years prior to the accident.
- The aircraft's controls were noted to be highly sensitive, particularly the rudder and elevator, which lacked sufficient tactile feedback.
- The improper installation of the seatbelts allowed the pilot's torso to pitch forward during the crash.
Safety action
- It is recommended that aircraft inspections and inspections of experimental aircraft place greater emphasis on the correct installation and functional safety of seatbelts, specifically recommending the use of center-locking type harnesses.
- A recommendation was made for the Finnish Aero Club (Suomen Ilmailuliitto) to establish an advisory organization to assist homebuilt aircraft builders in evaluating their readiness for first flights and providing guidance on necessary type-specific training.