What happened
On August 27, 2014, at Warsaw-Babice airport (EPBC), an incident occurred in front of the Warsaw Aero Club hangar involving a Jak 12A. Following the replacement of the aircraft's carburetor, the engine was started to perform a functional test. During this process, the aircraft suddenly surged forward. Despite the pilot immediately cutting the ignition to shut down the engine, the aircraft struck another aircraft that was parked nearby.
The investigation
The investigation, conducted by the operator's commission, established that the engine reached maximum RPM immediately upon startup due to the incorrect connection of the throttle lever on the carburetor. The investigation also found that wheel chocks had not been placed under the wheels during the engine test.
Furthermore, the investigation determined that the pneumatic wheel brakes were ineffective at preventing the movement of the aircraft. This lack of braking effectiveness was caused by low air pressure in the system, which had been depleted by multiple previous engine start attempts. The investigation also noted that the proximity of the parked aircraft was a factor, as it had been positioned too close to the aircraft undergoing the test.
Findings
- The primary cause of the incident was the incorrect connection of the throttle control lever.
- The crew was operating under significant time pressure, attempting to complete the engine test and move aircraft into the hangar before an approaching thunderstorm.
- This haste led to several contributing errors, including the failure to use wheel chocks and the improper positioning of the nearby aircraft.
- Low air pressure in the pneumatic braking system reduced the effectiveness of the brakes during the surge.
Safety action
- The incident was reviewed with the personnel involved to highlight the errors committed during the procedure.