What happened
On August 9, 2006, a Diamond DA 20-A1 (registration OK-BLB) was performing a training flight at Prague-Letňany Airport (LKLT). The pilot intended to practice an aborted takeoff on runway 05P, followed by a departure from runway 23L toward Senec (LKHS).
After engine start, the pilot taxied to the heliport to perform engine warm-up and a ground run. Following the successful completion of these checks, the aircraft taxied to the takeoff position. As the aircraft reached takeoff RPM and had traveled approximately 5 to 10 meters along the runway, the pilot experienced intense engine vibrations. The pilot immediately responded by shutting down the engine and stopping the aircraft.
Upon inspection by the crew, damage was identified on one propeller blade, with fragments of composite material found in the grass nearby. There were no injuries to the crew or passengers.
The investigation
The ÚZPLN investigation focused on the structural integrity of the propeller and the environmental conditions at the time of the incident. The investigation established that the aircraft's maintenance was up to date, with the last maintenance performed approximately 35 hours prior to the event. The pilot held a valid ATPL and medical certification, and the pre-flight inspection had revealed no defects.
Investigators examined the damaged propeller blade (HOFMAN Proppeller, type HOV352F) and found that the edge of the second blade showed no signs of impact with the runway surface or foreign objects. The investigation also confirmed that the runway surface was clear of debris and that the weather conditions (CAVOK, calm winds) were not a contributing factor.
Findings
- The takeoff was aborted due to severe engine vibrations caused by the separation of the composite surface from the wooden core of one propeller blade.
- The loss of rotating mass from the propeller blade led to the imbalance and subsequent vibration.
- There was no evidence of impact with ground objects or foreign object damage (FOD).
- The aircraft and engine mounts remained undamaged by the event.