# Airworthiness Directives; Raytheon (Beech) Model 400, 400A, 400T, MU-300, and MU-300-10 Airplanes
> **Rule** · Final rule. · Published 1998-03-20 · Effective 1998-04-24 · 63 FR 13495
## Document
- **Document number:** 98-6952
- **Category:** airworthiness
- **Type:** Rule
- **Action:** Final rule.
- **Citation:** 63 FR 13495
- **Publication date:** 1998-03-20
- **Effective date:** 1998-04-24
- **FAA docket:** Docket No. 97-NM-68-AD
## Abstract

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Raytheon (Beech) Model 400, 400A, 400T, MU- 300, MU-300-10 airplanes, that currently requires replacement of outflow/safety valves with serviceable valves. This amendment revises the applicability of the existing AD to add an airplane model and to remove other airplanes, as well as to identify the serial numbers of affected airplanes. The actions specified by this AD are intended to prevent cracking and consequent failure of the outflow/safety valves, which could result in rapid decompression of the airplane.

## Source
- [Federal Register document](https://www.federalregister.gov/documents/1998/03/20/98-6952/airworthiness-directives-raytheon-beech-model-400-400a-400t-mu-300-and-mu-300-10-airplanes)
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