# Proposed AD 99-NM-226-AD: Short Brothers Model SD3-60 SHERPA, SD3-SHERPA, SD3-30, and SD3-60 Series Airplanes

- Type: Proposed airworthiness directive (not in force)
- Status: Became AD 2001-02-08
- Action: Notice of proposed rulemaking (NPRM).
- Published: October 6, 1999, 64 FR 54239
- Comments due: November 5, 1999
- Became: [AD 2001-02-08](https://openairdocs.org/ad/2001-02-08)
- Docket: 99-NM-226-AD
- FR document: 99-26086
- Official PDF: https://openairdocs.org/files/sha256/b2/e9/b2e96909c9c87de45920fba8e70a961c8f6d0780b7ce6628e5a78ed6948d7d53 (from https://www.govinfo.gov/content/pkg/FR-1999-10-06/pdf/99-26086.pdf)
- Federal Register: https://www.federalregister.gov/documents/1999/10/06/99-26086/airworthiness-directives-short-brothers-model-sd3-60-sherpa-sd3-sherpa-sd3-30-and-sd3-60-series
- Page: https://openairdocs.org/proposed/99-NM-226-AD

## Summary

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Short Brothers Model SD3-60 SHERPA, SD3-SHERPA, SD3-30, and SD3-60 series airplanes. This proposal would require replacement of the existing pneumatic de-icing boot pressure indicator switch with a newly designed switch. This proposal is prompted by an occurrence on a similar airplane model in which the pneumatic de-icing boot indication light may have provided the flightcrew with misleading information as to the proper functioning of the de-icing boots. The actions specified by the proposed AD are intended to prevent ice accumulation on the airplane leading edges, which could reduce controllability of the airplane.

## Notices in this docket

- Oct 6, 1999: Notice of proposed rulemaking (NPRM). (first notice), FR document 99-26086, comments due Nov 5, 1999 (https://www.federalregister.gov/documents/1999/10/06/99-26086/airworthiness-directives-short-brothers-model-sd3-60-sherpa-sd3-sherpa-sd3-30-and-sd3-60-series)

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