Aircraft and Flight Information
A privately owned Cessna A185F Skywagon (registration HA-SVH) operated by a private individual was involved in a serious incident on 28 May 2014 at Krosno Airport (EPKR). The six-seat, single-engine aircraft was performing a parachute jump flight. The pilot, a 38-year-old male holding a valid CPL(A) license and medical certificate, began taxiing for runway 16 at 19:18 LMT for the second parachute flight of the day. Weather conditions had no influence on the occurrence.
Incident Sequence
After taxiing approximately 300 meters, a loud bang was heard. The pilot observed the left main wheel tire flying toward the rotating propeller. The tire struck the propeller, was thrown forward and left about 30 meters. The pilot immediately reduced engine RPM, shut down the engine, turned off magnetos, electrical power, and lights, and closed the fuel valve. The aircraft continued about 2.5 meters, veering left about 20 degrees before stopping. All six occupants (pilot and parachutists) disembarked uninjured.
Damage and Examination
Examination revealed that the retaining clamp for the left main wheel tire had separated from the hub. The clamp, along with three attaching bolts, was found nearby. A small fragment of the hub near one threaded hole had chipped off, and threads in all six hub holes for the clamp bolts were stripped. The bolt threads were undamaged but carried debris from the stripped hub threads. The propeller had two bent blades; one blade’s root had broken seal rings and excessive play. There was no ground contact with the propeller.
Cause
The investigation determined that the bolts securing the wheel rim clamp to the hub had been overtightened. The aluminum hub’s lower strength compared to the steel bolts caused thread failure in the hub when excessive torque was applied. The exact circumstances leading to the overtightening could not be conclusively established, but it most likely occurred during the last tire replacement on the left main wheel.
Preventive Measures
The aircraft owner was notified of the finding. The report was also forwarded to the Hungarian accident investigation authority as the owner was Hungarian.