# Airworthiness Directives; De Havilland Aircraft of Canada Limited (Type Certificate Previously Held by Bombardier, Inc.) Airplanes
> **Rule** · Final rule; request for comments. · Published 2021-12-21 · Effective 2022-01-05 · 86 FR 72174
## Document
- **Document number:** 2021-27709
- **Category:** airworthiness
- **Manufacturer:** De Havilland
- **Type:** Rule
- **Action:** Final rule; request for comments.
- **Citation:** 86 FR 72174
- **Publication date:** 2021-12-21
- **Effective date:** 2022-01-05
- **FAA docket:** Docket No. FAA-2021-1064
## Abstract

The FAA is superseding Airworthiness Directive (AD) 2017-19- 09, which applied to certain De Havilland Aircraft of Canada Limited (Type Certificate Previously Held by Bombardier, Inc.) Model DHC-8-400 series airplanes. AD 2017-19-09 required modifying the nose landing gear (NLG) shock strut assembly. This new AD requires repetitive lubrications of the trailing arm of the NLG. This new AD also requires revising the existing maintenance or inspection program to include new and revised airworthiness limitations (life limits for certain bolts). This AD was prompted by reports of a certain bolt being found missing or having stress corrosion cracking. The FAA is issuing this AD to address the unsafe condition on these products.

## Source
- [Federal Register document](https://www.federalregister.gov/documents/2021/12/21/2021-27709/airworthiness-directives-de-havilland-aircraft-of-canada-limited-type-certificate-previously-held-by)
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