# AD 80-21-12 R1: Engine Oil System

- Type: Airworthiness directive
- Status: Current
- Products: Great Lakes 2T-1A-1 and 2T-1A-2
- Effective: April 14, 1983
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Small airplane
- Amendment: 39-4625
- Registered aircraft: 142 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/25131B2B4E10ECA286256A4E00590C2C.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/80-21-12-R1

## The airworthiness directive

80-21-12 R1 GREAT LAKES AIRCRAFT CORPORATION: Amendment 39-3940 as amended by Amendment 39-4625. Applies to Models 2T-1A-1 and 2T-1A-2 (Serial Numbers 501 through 828) airplanes with Lycoming I0-360 or AEIO-360 engines installed, certificated in any category.

Compliance: Required as indicated, unless already accomplished.

To prevent engine oil inlet temperatures from exceeding acceptable limits within the next 50 hours time- in-service after the effective date of this AD, accomplish either paragraph (a) or (b) below:

  (a) Remove Cowl Face P/N 50106-2 and Belly Cowl P/N 50105-2 and modify in accordance with Great Lakes Service Bulletin No. 11, dated September 1, 1980, and incorporate Great Lakes Parts Kit SPK 101. Perform engine run-up and inspect oil system for leaks; or

  (b) Fabricate and install a louver plate (P/N 50105-33) and louver backing plate (P/N 50105-32) on the side of the belly cowling in accordance with Great Lakes Drawing Number 50105, Sheet 3 of4, Revision C.

  (c) The airplane may be flown in accordance with FAR 21.197 to a location where this AD may be accomplished.

  (d) An equivalent method of compliance may be approved by the Manager, Atlanta Aircraft Certification Office, FAA Central Region, 1075 Inner Loop Road, College Park, Georgia 30337.

Drawing 50105, Sheet 3 of 4, Revision C, and Great Lakes Service Bulletin No. 11, dated September 1, 1980, pertinent to this AD, may be obtained from Great Lakes Aircraft Company, Drawer A, Eastman, Georgia 31023; telephone (912) 374-5535.

This Amendment 39-4625 revises Amendment 39-3940 (45 FR 67646), AD 80-21-12 in its entirety.

Amendment 39-3940 became effective October 17, 1980.

This Amendment 39-4625 becomes effective April 14, 1983.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS A18EA](https://openairdocs.org/tcds/A18EA): WACO Classic Aircraft Corporation; names 2 of 3 models: 2T-1A-1, 2T-1A-2

## 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: 142 (142 by airframe model, 0 by engine model)
- Makers: Great Lakes 121, Waco Classic 20, Great Lakes/Fritz Joe 1

Models with the most aircraft:

- [Great Lakes 2T-1A-2](https://openairdocs.org/model/great-lakes-2t-1a-2): 115 aircraft (airframe model)
- [Waco Classic 2T-1A-2](https://openairdocs.org/model/waco-classic-2t-1a-2): 20 aircraft (airframe model)
- [Great Lakes 2T-1A-1](https://openairdocs.org/model/great-lakes-2t-1a-1): 6 aircraft (airframe model)
- [Great Lakes/Fritz Joe 2T-1A-2](https://openairdocs.org/model/great-lakes-fritz-joe-2t-1a-2): 1 aircraft (airframe model)

All 4 models: https://openairdocs.org/ad/80-21-12-R1/models.md
Every aircraft: https://openairdocs.org/ad/80-21-12-R1/aircraft.md

Its text cites no advisory circulars or STCs.

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.