# AD 66-20-04: Oil Filter Adapter Gasket - Type: Airworthiness directive - Status: Current - Products: Lycoming Engines IO-320-A1A, IO-320-A2A, IO-320-B1A, IO-320-B1B, IO-320-B1C, IO-320-B1D, IO-320-B2A, IO-320-C1A, IO-320-E2A, IO-360-A1A, IO-360-A1B, IO-360-A2A and 112 more - Effective: August 27, 1966 - Superseded by: Nothing supersedes this AD - Product type: Engine - Amendment: 39-277 - Registered aircraft: 62,405 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/1B9F32C6553252058625682A004F57DD.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/66-20-04 ## The airworthiness directive 66-20-04 LYCOMING: Amdt. 39-277, Part 39, Federal Register August 18, 1966. Applies to Model O-320, IO-320, O-340, O-360, IO-360, O-540, and IO-540 Series Engines Equipped With AC Oil Filters Except O-320- A, -E Series, Engine Serial Number 16128-27 and Higher; O-320-B, -C, and -D Series, Engine Serial Number 6217-39 and Higher; IO-320 Series, Engine Serial Numbers 2110-55A, 2113-55A and Higher; O-360 Series, Engine Serial Number 9346-36A and Higher; O-540 Series, Engine Serial Numbers 9770-40, 9800-40, 9803-40 and Higher; and IO-540 Series, Engine Serial Numbers 2831-48, 2835-48, 2840-48 and Higher. Compliance required within the next 50 hours' time in service after the effective date of this AD, unless already accomplished. To prevent further failures of oil filter adapter gasket, P/N 74904, accomplish the following: (a) Replace gasket, P/N 74904, with gasket, P/N 76691. (b) Inspect the stud, cap screws, and tapped holes in the accessory housing mounting padfor proper length or depth, as applicable, in accordance with Lycoming Service Bulletin No. 307 or later FAA-approved revision. Replace studs and cap screws of improper length and retap holes of insufficient depth as necessary in accordance with Bulletin No. 307 or later FAA-approved revision. This directive effective August 27, 1966. ## Affected data sheets (7) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS E-274](https://openairdocs.org/tcds/E-274): Lycoming Engines; names 34 of 60 models: O-320-C2B, O-320-E2B, O-320-E2C, O-320-B3B, O-320-C3A, O-320-C2A, O-320-D2A, O-320-A1B… - [TCDS E-295](https://openairdocs.org/tcds/E-295): Lycoming Engines; names 26 of 47 models: O-540-B2B5, O-540-A1D, O-540-A4B5, O-540-F1B5, O-540-A3D5, O-540-A4C5, O-540-F1A5, O-540-A1D5… - [TCDS E-286](https://openairdocs.org/tcds/E-286): Lycoming Engines; names 22 of 72 models: O-360-C1C, O-360-C1A, O-360-B1A, O-360-A1A, O-360-A3D, O-360-A4A, O-360-B2A, O-360-A1D… - [TCDS 1E4](https://openairdocs.org/tcds/1E4): Lycoming Engines; names 18 of 81 models: IO-540-A1A5, IO-540-B1C5, IO-540-G1A5, IO-540-C1B5, IO-540-G1B5, IO-540-B1B5, IO-540-C4B5, IO-540-K1B5… - [TCDS 1E10](https://openairdocs.org/tcds/1E10): Lycoming Engines; names 12 of 89 models: IO-360-B1C, IO-360-A2A, IO-360-B1D, IO-360-A2B, IO-360-C1B, IO-360-B1B, IO-360-A1A, IO-360-A1B… - [TCDS 1E12](https://openairdocs.org/tcds/1E12): Lycoming Engines; names 9 of 32 models: IO-320-B1C, IO-320-B1D, IO-320-B2A, IO-320-C1A, IO-320-B1B, IO-320-B1A, IO-320-A1A, IO-320-E2A… - [TCDS E-277](https://openairdocs.org/tcds/E-277): Lycoming Engines; names 3 of 3 models: O-340-A2A, O-340-B1A, O-340-A1A ## 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: 62,405 (0 by airframe model, 62,405 by engine model) - Makers: Piper 26,233, Cessna 14,521, Mooney 3,522, Beech 1,631, Robinson Helicopter 1,298, Grumman American Avn. 1,185, Bellanca 1,114, Maule 685, Champion 448, Aviat 423 Models with the most aircraft: - [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series): 27,057 aircraft (engine model) - [Lycoming O&VO-360 series](https://openairdocs.org/engine/lycoming-o-vo-360-series): 11,931 aircraft (engine model) - [Lycoming I0360 series](https://openairdocs.org/engine/lycoming-i0360-series): 6,174 aircraft (engine model) - [Lycoming 0-540 series](https://openairdocs.org/engine/lycoming-0-540-series): 5,228 aircraft (engine model) - [Lycoming IO-540 series](https://openairdocs.org/engine/lycoming-io-540-series): 4,219 aircraft (engine model) - [Lycoming IO-320 series](https://openairdocs.org/engine/lycoming-io-320-series): 1,707 aircraft (engine model) - [Lycoming O-360 series](https://openairdocs.org/engine/lycoming-o-360-series): 1,023 aircraft (engine model) - [Lycoming 0-360-A1D](https://openairdocs.org/engine/lycoming-0-360-a1d): 968 aircraft (engine model) - [Lycoming O-360-A1A](https://openairdocs.org/engine/lycoming-o-360-a1a): 601 aircraft (engine model) - [Lycoming O-540-F1B5](https://openairdocs.org/engine/lycoming-o-540-f1b5): 299 aircraft (engine model) - [Lycoming O-320 series](https://openairdocs.org/engine/lycoming-o-320-series): 256 aircraft (engine model) - [Lycoming IO-540-D4A5](https://openairdocs.org/engine/lycoming-io-540-d4a5): 237 aircraft (engine model) - [Lycoming IO-360 series](https://openairdocs.org/engine/lycoming-io-360-series): 217 aircraft (engine model) - [Lycoming IO-360-A1A](https://openairdocs.org/engine/lycoming-io-360-a1a): 196 aircraft (engine model) - [Lycoming O-320-A2B](https://openairdocs.org/engine/lycoming-o-320-a2b): 180 aircraft (engine model) - [Lycoming IO-540-C4B5](https://openairdocs.org/engine/lycoming-io-540-c4b5): 179 aircraft (engine model) - [Lycoming I0-360-B1E](https://openairdocs.org/engine/lycoming-i0-360-b1e): 141 aircraft (engine model) - [Lycoming O-320-D1A](https://openairdocs.org/engine/lycoming-o-320-d1a): 116 aircraft (engine model) - [Lycoming O-320-E2A](https://openairdocs.org/engine/lycoming-o-320-e2a): 98 aircraft (engine model) - [Lycoming O-320-B2B](https://openairdocs.org/engine/lycoming-o-320-b2b): 92 aircraft (engine model) All 126 models: https://openairdocs.org/ad/66-20-04/models.md Every aircraft: https://openairdocs.org/ad/66-20-04/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.