What happened
On June 3, 2007, a Zenair 701 ultralight aircraft, registration OK-BUU 25, crashed into hilly, partially forested terrain near Nová Ves u Nepomuku. The flight originated from the Chotěšov airfield with the intention of landing at Strakonice.
During the flight, the aircraft entered an area of low visibility and low cloud base where meteorological conditions no longer met the requirements for Visual Flight Rules (VFR). The aircraft struck the ground at a steep angle of approximately 60 degrees. The impact was severe, destroying the forward fuselage and causing the airframe to break at the trailing edge of the wing. A subsequent fire broke out at the crash site. Both the pilot and the passenger sustained fatal injuries and died shortly after the impact.
The investigation
The ÚZPLN investigation established several critical factors regarding the aircraft's configuration and the pilot's state. Analysis of the aircraft's weight revealed that the maximum takeoff weight (MTOW) had been exceeded by approximately 56 kg, primarily due to the combined weight of the pilot and passenger.
Investigators examined the aircraft's instruments and found that the altimeter had been set to a pressure of 965–970 hPa, despite the actual local pressure (QNH) being approximately 1020–101 HPa. This incorrect setting resulted in an indicated altitude that was nearly 450 meters lower than the actual altitude.
Medical examinations of the pilot revealed a blood alcohol concentration of 0.72 g/kg. While the pilot was found to be conscious and actively attempting to control the aircraft until the moment of impact, the presence of alcohol was noted as a factor that could have impaired psychomotor and sensory functions. The investigation also confirmed that the aircraft's mechanical systems, including the engine and flight controls, were fully functional prior to the impact.
Findings
- The pilot made the decision to continue the flight despite encountering meteorological conditions unsuitable for VFR flight.
- The aircraft was operating in a state of exceeding the maximum takeoff weight.
- The pilot was operating the aircraft under the influence of alcohol.
- The pilot likely lost spatial orientation after entering clouds (IMC).
- An incorrect altimeter setting contributed to the loss of situational awareness regarding terrain clearance.