# AD 80-25-05: Voltage Regulator Modification

- Type: Airworthiness directive
- Status: Current
- Products: Piper PA-31T and PA-31T1
- Effective: February 12, 1981
- Published: February 12, 1981
- Issued: January 29, 1981
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Small airplane
- Amendment: 39-4041
- Registered aircraft: 151 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/3574D4E5EDBED1D3862569A6005CD7CB.0001
- DRS record last changed: November 21, 2025
- Page: https://openairdocs.org/ad/80-25-05

## The airworthiness directive

80-25-05 PIPER: Amendment 39-4041. Applies to Piper PA-31T S/N 8120001 thru 8120010 and Piper PA-31T1 airplanes S/N 8104001 thru 8104012.

Compliance required as indicated:

To prevent failure of the voltage regulator which can result in complete electrical failure, prior to further flight either at night or into instrument weather conditions, alter the voltage regulator, Piper P/N 584152 in accordance with Piper telegraphic letter #31-26, dated November 26, 1980, or an approved equivalent.

Equivalent alterations must be approved by the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region, Jamaica, New York.

This amendment is effective February 12, 1981, and was effective upon receipt for all recipients of the letter of November 26, 1980, covering this same subject.

## 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/80-25-05/models.md
Every aircraft: https://openairdocs.org/ad/80-25-05/aircraft.md

Its text cites no advisory circulars or STCs.

## NTSB investigations that cite this AD (1)

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

- [NTSB ANC97IA035](https://openairdocs.org/ntsb/ANC97IA035), Mar 15, 1997: Piper PA-31-350 (N3542H), Kotzebue, AK, incident, minor damage. Probable cause: the jammed main landing gear which was caused by a binding main landing gear door with a broken hinge. The fractured, inadequate main landing gear door hinge was also causal.

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