AD Amdt-39-9834
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Textron | Canada Ltd | Airworthiness Directives; Allison Engine Company Model 250-C47B Turboshaft Engines |
| aircraft | Bell | Helicopter Textron | Airworthiness Directives; Allison Engine Company Model 250-C47B Turboshaft Engines |
| engine | Allison | Engine Company Model 250-C47B | Airworthiness Directives; Allison Engine Company Model 250-C47B Turboshaft Engines |
Unsafe Condition
Uncommanded inflight engine shutdowns due to electrical noise characteristics in the engine control unit (ECU) PW10 voltage and potential failure of the engine main electrical harness assembly and overspeed solenoid.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Replace the engine main electrical harness assembly with an improved assembly, disable the overspeed solenoid, inspect the ECU internal PW10 voltage for electrical noise characteristics and replace non-serviceable units. Add a placard to the helicopter instrument panel indicating the overspeed protection system is disabled, remove the prior placard from AD 96-21-12, revise the Rotorcraft Flight Manual, and perform maintenance actions to clear ECU faults before each flight.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Before further flight
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Affected Aircraft
Allison Engine Company Model 250-C47B turboshaft engines installed on Bell Helicopter Textron Model 407 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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