AD 2011-15-51
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Textron | Various | Airworthiness Directives; Bell Helicopter Textron Canada (Bell) Model 407 and 427 Helicopters |
| aircraft | Bell | 407 and 427 | Airworthiness Directives; Bell Helicopter Textron Canada (Bell) Model 407 and 427 Helicopters |
Unsafe Condition
Certain hydraulic servo actuators may have a loose nut, shaft, and clevis assembly due to improper lock-washer installation, which could result in a malfunction of the servo in the flight control system and subsequent loss of control of the helicopter.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Inspect certain hydraulic servo actuators to determine whether the shaft turns independently of the nut or the clevis assembly. If the shaft turns independently, replace the servo with an airworthy servo. If the shaft does not turn independently, inspect the lock washers. If any lock washer tab is not bent flush against a flat surface of the nut or clevis assembly, bend it flush. Reidentify the servo by metal-impression stamping or vibro-etching '67.01' onto the modification plate. Before installing a servo with a part number or serial number identified in this AD, inspect it following the AD requirements.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Before further flight for certain affected servos and within 25 hours time-in-service for certain other affected servos identified by a serial number.
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Bell Helicopter Textron Canada Model 407 and 427 helicopters.
AI-generated summary from the source AD text. Verify against the official source before acting.
Source: Official FAA Source ↗
Retrieved: Apr 6, 2026
Rights: U.S. Government Public Domain
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