# AD 57-03-03: Micronic Filter Cover

- Type: Airworthiness directive
- Status: Current
- Products: Boeing DC-7, DC-7B, DC-7C, 1049-54, 1049B-55 (Navy R7V-1), 1049C-55, 1049D-55, 1049E-55, 1049F-55 (USAF C-121C), 1049G-82, 1049H-82, 149-46 and 7 more
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Large airplane
- Registered aircraft: 9 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/D2F4880A40C870688625696F0047E86C.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/57-03-03

## The airworthiness directive

57-03-03 DOUGLAS AND LOCKHEED: Applies to Lockheed Constellation Series and Douglas DC-7 Series Airplanes.

Compliance required by April 1, 1957, for Constellation aircraft and by May 1, 1957, for DC-7 aircraft.

Under certain cold weather operating conditions the perforated paper covering around the Purolator micronic filter elements are subject to accumulation of ice as a result of entrained water crystals in the fuel freezing on this covering. This interferes with proper fuel filtering by causing the fuel to pass through the bypass valve in the filter unit. To make the micronic filter less susceptible to clogging by ice, the perforated paper covering around the filter element is to be removed. Removal of the perforated cover does not affect the filtering characteristics of the filter element. Filter elements without the paper covering are identified as Purolator P/N 30868-3.

## Affected data sheets (4) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS 6A5](https://openairdocs.org/tcds/6A5): Lockheed Martin Aeronautics Company; names 8 of 8 models: 1049G-82, 1049C-55, 1049E-55, 1049F-55 (USAF C-121C), 1049D-55, 1049B-55 (Navy R7V-1), 1049H-82, 1049-54
- [TCDS A-763](https://openairdocs.org/tcds/A-763): Lockheed Martin Aeronautics Company; names 6 of 6 models: 149-46, 649-79, 749A-79, 749-79, 649A-79, 49-46
- [TCDS 4A10](https://openairdocs.org/tcds/4A10): The Boeing Company; names 3 of 3 models: DC-7, DC-7C, DC-7B
- [TCDS 4A17](https://openairdocs.org/tcds/4A17): Lockheed Martin Aeronautics Company; names 1 of 1 models: 1649A-98

## 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: 9 (9 by airframe model, 0 by engine model)
- Makers: Douglas 5, Lockheed 4

Models with the most aircraft:

- [Douglas DC-7](https://openairdocs.org/model/douglas-dc-7): 2 aircraft (airframe model)
- [Douglas DC-7B](https://openairdocs.org/model/douglas-dc-7b): 2 aircraft (airframe model)
- [Douglas DC-7C](https://openairdocs.org/model/douglas-dc-7c): 1 aircraft (airframe model)
- [Lockheed 49-46](https://openairdocs.org/model/lockheed-49-46): 1 aircraft (airframe model)
- [Lockheed 749-79](https://openairdocs.org/model/lockheed-749-79): 1 aircraft (airframe model)
- [Lockheed 1049H-82](https://openairdocs.org/model/lockheed-1049h-82): 1 aircraft (airframe model)
- [Lockheed 1649A-98](https://openairdocs.org/model/lockheed-1649a-98): 1 aircraft (airframe model)

All 7 models: https://openairdocs.org/ad/57-03-03/models.md
Every aircraft: https://openairdocs.org/ad/57-03-03/aircraft.md

Its text cites no advisory circulars or STCs.

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