What happened
On August 10, 2019, an ELLIPSE Spirit ultralight aircraft, registration OM-M118, was performing a takeoff from runway 31 at Skuteč airport (LKSK) for a flight to Frýdlant. During the takeoff roll, the aircraft encountered a terrain-induced bump, causing it to momentarily lift approximately one meter off the ground. At this moment, the cockpit canopy locks failed, causing the canopy to partially open.
Despite the canopy opening, the pilot continued the takeoff attempt, intending to perform a left turn to return to the airport. During the turn, aerodynamic forces and a side gust caused the canopy to flap violently and eventually open to its full extent. This movement disrupted the airflow over the tail surfaces, leading to a loss of control and a left-hand spin. The aircraft entered a stall at an altitude of approximately 50 meters and struck trees at the edge of the airfield. The impact caused the aircraft to flip onto its back, resulting in one serious injury to the pilot and the total destruction of the aircraft.
The investigation
The ÚZPLN investigation established that prior to the flight, the pilot had disconnected the linear electromechanical actuator from the canopy to allow maintenance personnel to open the canopy manually. Upon taking possession of the aircraft after maintenance, the pilot failed to reconnect this actuator. Because the actuator was not engaged, it could not provide the necessary secondary support to keep the canopy closed.
Investigators also examined the aircraft's configuration and found that the integrated wing slots had been artificially taped over. This uncertified modification, intended to increase cruise speed, had the negative effect of increasing the stall speed and reducing stability and control effectiveness at low speeds. Additionally, the investigation found that the aircraft's operational documentation had not been updated to reflect the actual state of the aircraft's configuration.
Findings
- The immediate cause of the accident was the opening of the cockpit canopy during takeoff due to the failure of the mechanical canopy locks.
- The following contributing factors were identified:
- The pilot failed to reconnect the electromechanical actuator to the canopy after maintenance.
- The aircraft was being operated with a known structural deficiency in the side canopy locks, with the pilot relying on the electric actuator to hold them closed.
- The pilot did not abort the takeoff after the initial unlatching of the locks.
- The uncertified taping of the wing slots increased the stall speed and degraded maneuverability at low speeds.
- The pilot did not sufficiently familiarize himself with the local terrain for an emergency landing.
- The aircraft's operational documentation was inaccurate.