# AD 59-06-02: Landing Gear Orifice Check Valve

- Type: Airworthiness directive
- Status: Current
- Products: Boeing DC-7, DC-7B and DC-7C
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Large airplane
- Registered aircraft: 5 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/A86FBF9E721A4743862569BC00727A71.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/59-06-02

## The airworthiness directive

59-06-02 DOUGLAS: Applies to All Model DC-7 Series Aircraft.

Compliance required by first block overhaul after receipt of parts but not later than December 1, 1959.

Several instances have occurred wherein the green indicator light for one of the main landing gear failed to go on when the landing gears were extended. In one case, after landing, it was noted that the left gear downlatch was not fully engaged and the ground lock safety pin could not be installed. Subsequent investigation and laboratory tests revealed that the orifice check valve could malfunction due to contaminants in the hydraulic fluid of sufficient quantity and size (approximately 0.003-inch diameter) and thereby prevent full extension of the gear.

To overcome this difficulty, remove existing orifice check valve assembly, P/N 4498423-503 (Mineral Oil Aircraft), or P/N 4498423-5503 (Skydrol Aircraft), from each main landing gear actuating cylinder and replace with new orifice check valve assembly, P/N 2230565-5-093 (Mineral Oil Aircraft), or P/N 4481262-5-093 (Skydrol Aircraft). (Douglas Service Bulletin DC-7 No. 353 dated January 30, 1959, covers this same subject.)

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS 4A10](https://openairdocs.org/tcds/4A10): The Boeing Company; names 3 of 3 models: DC-7, DC-7C, DC-7B

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

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)

All 3 models: https://openairdocs.org/ad/59-06-02/models.md
Every aircraft: https://openairdocs.org/ad/59-06-02/aircraft.md

Its text cites no advisory circulars or STCs.

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