AD 2011-22-08
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | MD | Various | Airworthiness Directives; MD Helicopters, Inc. Model MD900 Helicopters |
Unsafe Condition
Failure of the Vertical Stabilizer Control System (VSCS) tube adapter, part number 500N7218-1, could lead to loss of yaw control and subsequent loss of control of the helicopter.
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Required Actions
Turn ON both VSCS switches. De-energize the autopilot (AP/SAS) by centering the trim actuators, turning off the AP/SAS MSTR switch, and pulling specific circuit breakers. Install placards for AP/SAS deactivation and airspeed limitation. Revise the Rotorcraft Flight Manual (RFM) for limitations and emergency procedures. Alternatively, replace both VSCS tube adapters with newly-designed airworthy adapters, P/N 900C2010303-101, to terminate the AD requirements.
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Compliance Time
Before further flight
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Affected Aircraft
MD Helicopters, Inc. Model MD900 helicopters with a Vertical Stabilizer Control System (VSCS) tube adapter, part number 500N7218-1, installed, certificated in any category.
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Source: Official FAA Source ↗
Retrieved: Apr 6, 2026
Rights: U.S. Government Public Domain
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