AD 2021-10-13
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Bombardier | Various | Airworthiness Directives; De Havilland Aircraft of Canada Limited (Type Certificate Previously Held by Bombardier, Inc.) Airplanes |
| aircraft | Bombardier | Various | Airworthiness Directives; De Havilland Aircraft of Canada Limited (Type Certificate Previously Held by Bombardier, Inc.) Airplanes |
| aircraft | de Havilland | Various | Airworthiness Directives; De Havilland Aircraft of Canada Limited (Type Certificate Previously Held by Bombardier, Inc.) Airplanes |
Unsafe Condition
Several failure modes of the nose wheel steering (NWS) system may cause the loss of feedback from both rotary variable differential transformers to the steering control unit, leading to NWS runaway, loss of directional control of the airplane, and possible consequent runway excursion.
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Required Actions
Perform modifications to the NWS system, in accordance with paragraph 3.B of the Accomplishment Instructions of De Havilland Aircraft of Canada Limited Service Bulletin 84-32-162, Revision B, dated November 13, 2019, including UTC Aerospace Systems Service Bulletin 406300-32-142, dated June 24, 2019; and UTC Aerospace Systems Service Bulletin 406330-32-143, dated June 24, 2019, within 4,000 flight hours or 18 months after the effective date of this AD.
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Compliance Time
Within 4,000 flight hours or 18 months after the effective date of this AD
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Affected Aircraft
De Havilland Aircraft of Canada Limited Model DHC-8-401 and -402 airplanes, certificated in any category, serial numbers 4001, and 4003 through 4608 inclusive.
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Source: Official FAA Source ↗
Retrieved: Apr 6, 2026
Rights: U.S. Government Public Domain
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