# AD 91-21-09: Air Induction System

- Type: Airworthiness directive
- Status: Current
- Products: Piper PA-24-260
- Effective: November 29, 1991
- Published: October 28, 1991
- Issued: September 25, 1991
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Small airplane
- Amendment: 39-8056
- Docket: 91-CE-41-AD
- Registered aircraft: 590 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/A0194E08F84C594F862569A700559C7D.0001
- DRS record last changed: November 21, 2025
- Page: https://openairdocs.org/ad/91-21-09

## The airworthiness directive

91-21-09 PIPER AIRCRAFT CORPORATION: Amendment 39-8056. Docket No. 91- CE-41-AD. Supersedes AD 91-02-06.

Applicability: Model PA-24-260 airplanes (serial number (S/N) 24-3642, S/N 24-4000 through 24-4255, S/N 24-4257 through 24-4782, and S/N 24-4784 through 24-4803) that are equipped with nonturbocharged fuel-injected engines, certificated in any category.

Compliance: Required within the next 100 hours time-in-service after the effective date of this AD, unless already accomplished.

To prevent inadvertent engine stoppage while flying in weather conditions conducive to induction system icing, accomplish the following:

  (a) Modify the airplane by installing a manually controlled heated alternate air induction system in accordance with the instructions in either Piper Service Bulletin No. 861, dated May 4, 1987, or Supplemental Type Certificate SA2694CE.

  (b) The installation of a manually controlled heated alternate air induction system does not constituteapproval for flight in icing conditions.

  (c) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate the airplane to a location where the requirements of this AD can be accomplished.

  (d) An alternative method of compliance that provides an equivalent level of safety may be approved by the Manager, Atlanta Aircraft Certification Office, 1669 Phoenix Parkway, Suite 210C, Atlanta, Georgia 30349. The request should be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Atlanta Aircraft Certification Office.

  (e) The modification required by this AD shall be done in accordance with Piper Service Bulletin No. 861, dated May 4, 1987. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR Part 51. Copies of Piper Service Bulletin No. 861, dated May 4, 1987, may be obtained from the Piper Aircraft Corporation, 2926 Piper Drive, Vero Beach, Florida 32960. Copies of the service bulletin may be inspected at the FAA, Central Region, Office of the Assistant Chief Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri, or at the Office of the Federal Register, 1100 L Street, NW, Room 8401, Washington, DC.

Airworthiness Directive 91-21-09 supersedes Amendment 39-6849, AD 91-02-06.

This amendment (39-8056, AD 91-21-09) becomes effective on November 29, 1991.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS 1A15](https://openairdocs.org/tcds/1A15): Piper Aircraft Inc.; names 1 of 4 models: PA-24-260

## 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: 590 (590 by airframe model, 0 by engine model)
- Makers: Piper 590

Models with the most aircraft:

- [Piper PA-24-260](https://openairdocs.org/model/piper-pa-24-260): 590 aircraft (airframe model)

All 1 models: https://openairdocs.org/ad/91-21-09/models.md
Every aircraft: https://openairdocs.org/ad/91-21-09/aircraft.md

## Related documents

- [STC SA2694CE](https://openairdocs.org/stc/SA2694CE): Installation of manually controlled engine induction alternate air heat system.. Webco Aircraft Co, Cited in the text

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