# Airworthiness Directives; Bombardier, Inc. Model BD-100-1A10 (Challenger 300) Airplanes
> **Rule** · Final rule. · Published 2012-04-05 · Effective 2012-05-10 · 77 FR 20520
## Document
- **Document number:** 2012-8041
- **Category:** airworthiness
- **Type:** Rule
- **Action:** Final rule.
- **Citation:** 77 FR 20520
- **Publication date:** 2012-04-05
- **Effective date:** 2012-05-10
- **FAA docket:** Docket No. FAA-2011-1064
## Abstract

We are adopting a new airworthiness directive (AD) for all Bombardier, Inc. Model BD-100-1A10 (Challenger 300) airplanes. This AD was prompted by reports that the horizontal stabilizer trim actuator (HSTA) no-back and the number 1 motor brake assembly (MBA) can both fail dormant. This AD requires revising the airplane maintenance schedule to include new functional tests of the HSTA no-back and HSTA brake system. We are issuing this AD to prevent dormant failure of the HSTA no-back and the number 1 MBA, which along with additional component failure could result in an uncontrollable horizontal stabilizer surface runaway without the ability to retrim, and consequent loss of the airplane.

## Source
- [Federal Register document](https://www.federalregister.gov/documents/2012/04/05/2012-8041/airworthiness-directives-bombardier-inc-model-bd-100-1a10-challenger-300-airplanes)
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