# AD 79-20-08: Induction System

- Type: Airworthiness directive
- Status: Historical
- Products: Great Lakes 2T-1A-1 and 2T-1A-2
- Effective: October 8, 1979
- Superseded by: [AD 2004-25-22](https://openairdocs.org/ad/2004-25-22)
- Product type: Aircraft, Small airplane
- Amendment: 39-3580
- Registered aircraft: 142 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/281C743CEF7ACF4786256A38005B042D.0001
- DRS record last changed: August 7, 2025
- Page: https://openairdocs.org/ad/79-20-08

## The airworthiness directive

79-20-08 GREAT LAKES: Amendment 39-3580. Applies to Models 2T-1A-1 and 2T- 1A-2 airplanes having a Lycoming IO-360-B1F6 or AIO-360-B1G6 engine installed.

COMPLIANCE: Required as indicated unless already accomplished.

To preclude engine induction system blockage by pieces of failed alternate air doors and resulting power loss, accomplish the following:

A) Within the next 25 hours time-in-service after the effective date of this AD:

1. Visually inspect the aircraft induction system drain fitting located in the induction elbow below the fuel injector for blockage or restriction. If the hole is restricted in the weld area or not drilled through the elbow, before further flight open up the restricted hole or drill a hole in the elbow at the fitting location using a No. 10 (.193) drill.

B) Within 25 hours time-in-service after the effective date of this AD and each 100 hours time-in-service thereafter:

1. Visually inspect the alternate air door for distortion, heat damage and cracks. If any of these conditions are noted, before further flight repair the existing door or fabricate and install a new door in accordance with Figure I of this AD.

2. Visually inspect the induction system including the filter for cleanliness, security and damage from backfire or induction system fires. Before further flight, repair or replace any damaged components necessary to restore the system to an airworthy condition.

C) Any equivalent method of compliance with this AD must be approved by the Chief, Engineering and Manufacturing Branch, FAA, Central Region.

This amendment becomes effective on October 8, 1979.

FIGURE 1

## 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/79-20-08/models.md
Every aircraft: https://openairdocs.org/ad/79-20-08/aircraft.md

## Related documents

- [AD 2004-25-22](https://openairdocs.org/ad/2004-25-22): Engine induction system · Great Lakes 2T-1A-1 and 2T-1A-2. Effective Jan 28, 2005. Supersedes this AD

Its text cites no advisory circulars or STCs.

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