What happened
The helicopter experienced a sudden failure of its number two engine during a hover maneuver for landing while carrying an external load.
The investigation
A post-accident examination of the failed engine revealed significant internal damage. All turbine blades were found to be bent, broken, or missing. Additionally, the engine case was severed into two parts immediately adjacent to the plane of rotation of the power turbine. However, the power turbine disc itself remained intact.
Findings
The engine had accumulated a total time of 2058 hours at the time of the failure. The manufacturer's recommended Time Between Overhaul (TBO) was 1800 hours. The operating company utilized a military TBO extension, which had been approved by the Federal Aviation Administration (FAA), allowing operations up to 2100 hours.
Safety message
The engine failure occurred within the bounds of an FAA-approved extension but exceeded the original manufacturer's TBO. This highlights the critical importance of adhering to established maintenance intervals and understanding the limits of any approved extensions.