# AD 77-21-03: Rudder Spar Cracks

- Type: Airworthiness directive
- Status: Current
- Products: Piper PA-36-285
- Effective: October 18, 1977
- Published: October 13, 1977
- Issued: October 4, 1977
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Small airplane
- Amendment: 39-3056
- Registered aircraft: 40 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/6105CB79CF91AB678625699D004F6359.0001
- DRS record last changed: November 21, 2025
- Page: https://openairdocs.org/ad/77-21-03

## The airworthiness directive

77-21-03 PIPER: Amendment 39-3056. Applies to Model PA-36-285, Serial Nos. 36-7360001 through 36-7760003 certificated in all categories.

To prevent hazards in flight associated with rudder spar cracks, accomplish the following:

  (a) Within the next 50 hours in service from the effective date of this AD unless previously accomplished within the past 50 hours in service and at intervals not to exceed 100 hours in service from the last inspection, inspect the rudder spar at hinge attachment points for cracks using a magnifying glass of at least ten power.

  (b) If cracks exist replace the rudder assembly with a new rudder assembly Piper Part No. 98125-04 or equivalent.

  (c) Upon the incorporation of rudder assembly, Piper Part No. 98125-04 or equivalent, compliance with the requirements of this AD may be dispensed with.

  (d) Equivalent inspection and repairs must be approved by the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region.

  (e) Upon submission of substantiating data by an owner or operator through an FAA Maintenance Inspector, the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region may adjust the inspection intervals specified in this AD.

(Piper Service Bulletin No. 518 refers to this subject.)

This amendment is effective October 18, 1977.

## 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: 40 (40 by airframe model, 0 by engine model)
- Makers: Piper 40

Models with the most aircraft:

- [Piper PA-36-285](https://openairdocs.org/model/piper-pa-36-285): 40 aircraft (airframe model)

All 1 models: https://openairdocs.org/ad/77-21-03/models.md
Every aircraft: https://openairdocs.org/ad/77-21-03/aircraft.md

Its text cites no advisory circulars or STCs.

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