What happened
On June 22, 2000, at 17:35 local time, a Jak-52 aircraft, registration LY-AHT, was performing aerobatic training maneuvers above the Kaunas Dariaus ir Girėno Aerodrome. The flight began under visual flight rules in good weather conditions. After climbing to 4,000 feet, the pilot initiated an aerobatic sequence, during which the elevator trim became restricted. The pilot attempted to recover the aircraft from a stall and transition into level flight; however, the aircraft continued to oscillate and struggle with stability.
During the attempt to manage the situation, the connection between the pilot's headset and the aircraft radio disconnected, preventing the transmission of an emergency signal to air traffic control. As the pilot transitioned into a backflight maneuver to steer away from the city, the engine failed at approximately 700 feet. Due to the limited fuel capacity available during inverted flight, the engine ceased operation. The pilot successfully exited the aircraft via parachute. The Jak-52 impacted the ground near a roadside embankment by the highway between Garliava and Kaunas, striking near a petrol station and catching fire. There were no fatalities.
The investigation
The investigation focused on why the elevator trim became restricted during maneuvers. Investigators discovered that a bracket used for mounting a barograph had been removed from the aircraft in late May. This bracket was not used in the installation of new smoke-generation equipment but was left unsecured in the cockpit area.
While both the pilot and an engineer had inspected the interior of the aircraft prior to the flight, the small metal component remained undetected. The investigation established that the bracket had migrated into the fuselage and eventually became lodged between the elevator trim tab and its guide.
Findings
- A barograph mounting bracket was left unsecured in the aircraft following maintenance/equipment installation.
- The loose bracket migrated into the fuselage and jammed the elevator trim mechanism during aerobatic maneuvers.
- An electrical disconnection between the pilot's headset and the radio prevented the pilot from notifying air traffic control of the emergency.
- The engine failure occurred because the flight duration in an inverted position exceeded the fuel supply available in the inverted-flight tank.