AD 2001-25-06
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sikorsky | Aircraft Corporation Model S-76B and S-76C | Airworthiness Directives; Sikorsky Aircraft Corporation Model S-76B and S-76C Helicopters |
Unsafe Condition
Failure of the essential bus could cause both attitude and heading reference (AHRS) WARN circuits to generate an AHRS fail signal, resulting in both autopilots going off-line and loss of control of the helicopter.
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Required Actions
Modify Nos. 1 and 2 AHRS WARN circuits in accordance with Sikorsky Aircraft Corporation Alert Service Bulletin No. 76-34-7A (320A), Revision A, dated September 17, 2001. An alternative method of compliance or adjustment of the compliance time may be used if approved by the Manager, Boston Aircraft Certification Office, FAA.
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Compliance Time
Within 30 days after the effective date of this AD, unless accomplished previously.
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Affected Aircraft
Sikorsky Aircraft Corporation Model S-76B helicopters, serial numbers 760430, 760441 through 760445, 760448 through 760452, 760454, 760455, 760458, 760462, and 760465, and Model S-76C helicopters, serial numbers 760420, 760436, 760438, 760440, 760453, 760456, 760457, 760459, 760460, 760461, 760463, 760464, 760466 through 760487, 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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