On April 14, 1986, a Bell UH-1B (registration N4242T) operated by Colony Helicopters was involved in an aviation accident near North Port, FL. Investigators recorded the probable cause as: Loss of two turbine blades due to pre-existing cracks, as evidenced by burning at the failure points. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter experienced an engine failure at approximately 8 feet AGL shortly after takeoff, resulting in a hard landing with substantial damage. Post-accident inspection revealed loss of two turbine blades due to pre-existing cracks.
Incident Overview
A helicopter sustained substantial damage following a hard landing after an engine failure occurred at an altitude of approximately 8 feet above ground level shortly after takeoff. The flight experienced a sudden loss of power, leading to the hard landing.
Post-Accident Inspection
A detailed post-accident inspection of the engine revealed that the power turbine wheel had lost two turbine blades. This loss caused the turbine section of the engine to seize, which in turn sheared the drive shaft connecting to the compressor section. The failure points of the two turbine blades exhibited burning, indicating the presence of pre-existing cracks prior to the incident.
Findings
The engine failure was traced to the structural failure of the turbine blades. The burning observed at the fracture surfaces is characteristic of cracks that existed before the flight. No other contributing factors were identified in the source material.
Probable cause
Loss of two turbine blades due to pre-existing cracks, as evidenced by burning at the failure points.