# AD 81-01-01: Propeller Deice Relay

- Type: Airworthiness directive
- Status: Current
- Products: Piper PA-31T and PA-31T1
- Effective: February 27, 1981
- Published: February 26, 1981
- Issued: February 13, 1981
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Small airplane
- Amendment: 39-4051
- Registered aircraft: 151 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/E3A722266036D70E862569A6005CDA41.0001
- DRS record last changed: November 21, 2025
- Page: https://openairdocs.org/ad/81-01-01

## The airworthiness directive

81-01-01 PIPER: Amendment 39-4051. Applies to Piper PA-31T S/N 8120008, 8120009, 8120010, and 8120013, and Piper PA-31T1 airplanes S/N 8104007, 8104008, 8104009, 8104010, 8104011, 8104012, and 8104013. Compliance required as indicated, unless already accomplished.

To prevent loss of the propeller and intake lip deicing functions, comply as follows:

Prior to further flight in known icing conditions, inspect for proper propeller and intake lip deice power relay in accordance with Piper telegraphic form letter #31-28, dated December 22, 1980, or equivalent, approved by Chief, Engineering and Manufacturing Branch. If (P/N 484247) relay is installed, check to insure that correct D.C. relay PRD7DYD (24 VDC) is installed. If the latter relay is not installed, remove and install proper relay prior to further flight in known icing conditions.

This amendment is effective February 27, 1981, and was effective upon receipt by all recipients of the letter dated December 24, 1980.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS A8EA](https://openairdocs.org/tcds/A8EA): Piper Aircraft Inc.; names 2 of 6 models: PA-31T, PA-31T1

## Registered aircraft it may apply to (OpenAirDocs)

Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment.

- Aircraft: 151 (151 by airframe model, 0 by engine model)
- Makers: Piper 151

Models with the most aircraft:

- [Piper PA-31T](https://openairdocs.org/model/piper-pa-31t): 87 aircraft (airframe model)
- [Piper PA-31T1](https://openairdocs.org/model/piper-pa-31t1): 64 aircraft (airframe model)

All 2 models: https://openairdocs.org/ad/81-01-01/models.md
Every aircraft: https://openairdocs.org/ad/81-01-01/aircraft.md

Its text cites no advisory circulars or STCs.

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