# AD 66-18-03: Induction System Icing

- Type: Airworthiness directive
- Status: Current
- Products: Piper PA-23-250 (Navy UO-1) and PA-E23-250
- Effective: August 2, 1966
- Published: July 23, 1966
- Issued: July 18, 1966
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Small airplane
- Amendment: 39-262
- Registered aircraft: 899 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/5D540747193B21448625699700580983.0001
- DRS record last changed: November 21, 2025
- Page: https://openairdocs.org/ad/66-18-03

## The airworthiness directive

66-18-03 PIPER: Amdt. 39-262 Part 39 Federal Register July 23, 1966. Applies to Model PA-23-250 and PA-E23-250 Airplanes, Serial Numbers 27-2505 through 27-3139 and 27- 3141 through 27-3275, Not Equipped With Turbochargers.

Compliance required as indicated, unless already accomplished.

To prevent engine power failures due to induction system icing, accomplish the following:

  (a) Within the next 10 hours' time in service after the effective date of this AD, until modified in accordance with (b), attach the following operating limitation placard to the instrument panel in full view of the pilot:

"Do not operate into known or forecast icing conditions.

Do not apply manual alternate air."

  (b) Within the next 100 hours' time in service after the effective date of this AD, modify alternate air systems to provide heated alternate air in accordance with Piper Service Bulletin No. 230A, dated May 6, 1966, incorporating Kit No. 757021.

(Piper Service Bulletin No. 230, dated March 4, 1966, also pertains to this subject.)

This directive effective August 2, 1966.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS 1A10](https://openairdocs.org/tcds/1A10): Piper Aircraft Inc.; names 2 of 6 models: PA-E23-250, PA-23-250 (Navy UO-1)

## 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: 899 (899 by airframe model, 0 by engine model)
- Makers: Piper 899

Models with the most aircraft:

- [Piper PA-23-250](https://openairdocs.org/model/piper-pa-23-250): 894 aircraft (airframe model)
- [Piper PA-23-250 (6PCLM)](https://openairdocs.org/model/piper-pa-23-250-6pclm): 5 aircraft (airframe model)

All 2 models: https://openairdocs.org/ad/66-18-03/models.md
Every aircraft: https://openairdocs.org/ad/66-18-03/aircraft.md

Its text cites no advisory circulars or STCs.

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