What happened
On July 14, 2004, at approximately 11:23 UTC, a Zlin Z 226 MS, registration OK-KMT, departed from runway 29 at Havlíčkov Brod (LKHB) for its tenth training flight of the day. The aircraft was performing a glider tow operation for members of the Prague-Letňany Aero Club, pulling an L 13 glider, registration OK-2824.
During the initial climb, the flight crew was engaged in training maneuvers. The instructor in the glider was actively correcting the student pilot's deviations to maintain the correct position behind the tug. While climbing at an altitude of between 50 and 100 meters, the aircraft encountered a strong thermal turbulence gust. From the perspective of the glider instructor, the tug suddenly veered sharply to the right and banked left at an angle of approximately 20 to 30 degrees, entering a rapid descent.
In an attempt to prevent the glider from overshooting the tug during the sudden drop, the instructor applied air brakes and attempted to release the tow cable. After several attempts, the instructor successfully disconnected the glider, which subsequently performed a safe landing in a potato field near Šmolovy. However, the Zlin Z 226 MS was unable to recover from its steep descent and struck the ground in a grain field near Poděbaby. The impact caused the fuel tanks to rupture, and the aircraft immediately caught fire. The pilot of the tug sustained fatal injuries during the impact.
The investigation
The ÚZPLN investigation examined the flight sequence, the meteorological conditions, and the technical state of the aircraft. The investigation established that the weather at the aerodrome was CAVOK with light winds, which was suitable for the intended flight activities. The technical inspection of the Zlin Z 226 MS confirmed that the aircraft was fully airworthy and that its maintenance was up to date; no mechanical failures were found in the flight controls or the engine, which was noted to have been operating until the moment of impact.
Findings
- The primary cause of the accident was the pilot's failure to maintain proper piloting technique.
- The pilot of the tug likely failed to maintain the minimum required climb speed necessary to safely tow the glider, especially considering the nature of the training flight and the presence of thermal turbulence in the surface layer.
- The low altitude of the flight provided insufficient margin to recover from the steep descent caused by the loss of airspeed.
- The instructor in the glider was preoccupied with correcting the student pilot's steering errors, which prevented him from reacting in time to the deteriorating flight conditions of the tug aircraft.