AD 2021-20-06
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Airbus | Helicopters Model AS355E | Airworthiness Directives; Airbus Helicopters |
Unsafe Condition
multiple fatigue cracks in power turbine (PT) 3rd stage wheels, which could result in fatigue failure of a PT 3rd stage wheel, and subsequent loss of engine power, release of debris and damage to the helicopter, and loss of control of the helicopter.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
revising the existing Rotorcraft Flight Manual (RFM) for your helicopter to replace a note with a caution to not allow rotor speed to stagnate between 279 and 374 revolutions per minute (RPM), and installing a placard to avoid 71-95% N2 steady-state speed (avoid operation at 279-374 RPM).
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Compliance Time
within 50 hours time-in-service after the effective date of this AD
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Affected Aircraft
Airbus Helicopters Model AS355E, AS355F, AS355F1, and AS355F2 helicopters, certificated in any category, with a Rolls-Royce Corporation (formerly Allison) engine Model 250-C20F installed.
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Source: Official FAA Source ↗
Retrieved: Apr 6, 2026
Rights: U.S. Government Public Domain
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