AD 2010-04-07
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Aviat | Various | Airworthiness Directives; Turbomeca Arriel 2S1 Turboshaft Engines |
| engine | Turbomeca | Arriel 2S1 | Airworthiness Directives; Turbomeca Arriel 2S1 Turboshaft Engines |
Unsafe Condition
Loss of steps of the stepper motor controlling the fuel metering valve inside the HMU during acceleration up to OEI 30-second rating, leading to in-flight loss of full automatic control of the engine.
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Required Actions
Upgrade the digital electronic control unit (DECU) software to version 11.01 to implement modification TU 109 within 350 operating hours after the effective date. Do not operate a twin-engine helicopter with one engine upgraded to TU 109 if the other engine is not upgraded.
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Compliance Time
Within 350 operating hours after the effective date
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Affected Aircraft
Turbomeca Arriel 2S1 turboshaft engines that have not incorporated Modification TU 109, installed on, but not limited to, Sikorsky S-76C twin-engine helicopters.
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Source: Official FAA Source ↗
Retrieved: Apr 4, 2026
Rights: U.S. Government Public Domain
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