# Airworthiness Directives; Pilatus Aircraft Ltd. Models PC-12 and PC-12/45 Airplanes
> **Rule** · Final rule; request for comments. · Published 1997-11-06 · Effective 1997-12-01 · 62 FR 59993
## Document
- **Document number:** 97-29236
- **Category:** airworthiness
- **Manufacturer:** Pilatus
- **Type:** Rule
- **Action:** Final rule; request for comments.
- **Citation:** 62 FR 59993
- **Publication date:** 1997-11-06
- **Effective date:** 1997-12-01
- **FAA docket:** Docket No. 97-CE-95-AD
## Abstract

This amendment adopts a new airworthiness directive (AD) that applies to Pilatus Aircraft Ltd. (Pilatus) Models PC-12 and PC-12/45 airplanes. This AD requires replacing the fuel tank vent valves with modified fuel tank vent valves. This AD is the result of mandatory continued airworthiness information (MCAI) issued by the airworthiness authority for Switzerland. The actions specified by this AD are intended to prevent the fuel tank inward vent valve from freezing, which, if followed by a cold soak at altitude, could result in wing airfoil distortion and structural damage with consequent degradation of the airplane's handling qualities.

## Source
- [Federal Register document](https://www.federalregister.gov/documents/1997/11/06/97-29236/airworthiness-directives-pilatus-aircraft-ltd-models-pc-12-and-pc-1245-airplanes)
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