Covering form of preliminary or final report

 

On 13 August 2019, the AAII received an air accident notification in relation to the collision of two gliders in flight. The pilots of both gliders were participants of the international competition of historical gliders, the 18th year of HOP 2019, held by the Aeroclub Hronov at the airport in Velké Poříčí.

 

During the flight, the gliders collided when the pilot of the VT 16 Orlík, OK-3405, glider was flying in circles in the upward airstream, and the pilot of the VT 116 Orlík II, OK-7410, glider wanted to fly into the considered upward airstream in front of him. Due to the collision, the rear fuselage and the tailplanes of the OK-3405 glider were destroyed and detached. Having lost controllability, the glider crashed on the ground in an uncontrolled fall in the maize field approx. 3 km NW of the centre of Trutnov. The glider pilot died. The glider was destroyed.

After the collision, the pilot of the OK-7410 glider checked whether the glider was controllable and as he was able to continue flying, he landed with his damaged glider on the area of Trutnov ARV. The pilot was not hurt.

Both pilots were fit to fly, experienced and both had previous experience with competitive flights. Both were familiar with flight characteristics of the VT 16 Orlík and VT 116 Orlík II gliders.

Prior to the collision, OK-7410 was flying directly in the southern direction in order to join an upward airstream based on observation of the cloud base in the area and of other gliders circling. Subsequently, he changed the course of the flight to approx. 160°. In front of him, to the left, the OK-3405 glider was already circling, and slightly to the right another glider (OK-6922).

The pilot of OK-3405 during circling NW of Trutnov performed approximately four and a half 360° turns of different diameters during which he kept moving in the direction of the upward airstream to NE (at approx. 253°). Concerning his manoeuvre, it was possible to expect him most likely to continue circling.

Based on the data regarding the movement of both the gliders, as well as according to the explanation provided by the OK-7410 pilot, the collision took place in the trajectory segment between 13:39:38 and 13:38:44. Both the gliders were turning left and the pilot of OK-7410 already lost the OK-3405 glider from his field of view. The flight data fixation time interval was 6 s in OK-3405, and 5 s in OK-7410. Without more accurate data regarding the positions of both the gliders on their respective trajectories they were flying in the given interval, it was possible to determine the probable relative position at the moment of collision only on the basis of the damage found on the gliders.

The extent of the damage and the paint scuffs on the OK-7410 glider, and the tail fragments from the OK-3405 glider prove with a high degree of probability that the collision took place between the OK-3405 lower fuselage end part and the upper part of the leading edge of the left half of the OK-7410 wing. Forces generated in the collision resulted in the OK-3405 tail part integrity damage.

The cause of the air accident was the destruction of the glider tail part and subsequent loss of controllability as the result of a collision caused by the pilots’ inability to discern the danger of collision in time sufficient enough in order to effectively avoid it.

AAII issues no safety recommendations.

Attached final report in PDF file is in original Czech language.