Airworthiness Directive · Amendment 39-21546 · Landing gear
De Havilland Aircraft of Canada Limited (Type Certificate Previously Held by Bombardier, Inc.) Airplanes
This AD applies to 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.
The FAA is superseding Airworthiness Directive (AD) 2015-17- 08, which applied to certain Bombardier, Inc. Model DHC-8-400 series airplanes. AD 2015-17-08 required installing new cable assemblies with a pull-down resistor. This AD requires modifications to the nose wheel steering (NWS) system. This AD was prompted by a report indicating that several failure modes of the NWS system may cause the loss of feedback from both rotary variable differential transformers to the steering control unit. The FAA is issuing this AD to address the unsafe condition on these products.
Within 4,000 flight hours or 18 months, whichever occurs first after the effective date of this AD: 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.
