WASHINGTON (CN) – The Federal Aviation Administration has issued an airworthiness directive for an unsafe condition in Turbomeca Arriel 2S1 turboshaft engines, used in utility helicopters such as the Sikorsky S-76C.
France’s aviation authority identified a loss of automatic control on an engine, when it accelerated due to the helicopter’s recording that the second engine was slowing. The second engine slowed due to “the untimely reset of its digital electronic control unit.”
Operators of helicopters with these engines are to upgrade the digital electronic control unit software to Modification TU 109 within 350 operating hours of March 23, the effective date of this directive. The directive cautions that both engines on a twin-engine helicopter must have the same upgrade.