# AD 56-25-04: Flap Symmetry

- Type: Airworthiness directive
- Status: Current
- Products: Lockheed 1049-54, 1049C-55, 149-46, 49-46, 649-79, 649A-79, 749-79 and 749A-79
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Large airplane
- Registered aircraft: 2 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/3C9524D96BFE5C868625696D0071ACAF.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/56-25-04

## The airworthiness directive

56-25-04 LOCKHEED: Applies to All Models 49, 149, 649, 649A, 749, 749A Aircraft; Model 1049 Serial Numbers 4001 Through 4024; Model 1049C Serial Numbers 4501 Through 4520 and 4523 Through 4538.

Compliance required at first block overhaul following receipt of parts or by March 1, 1958, whichever occurs first.

In view of the continuing series of incidents wherein flaps extend on one side of the aircraft out of symmetry with the other side, a means shall be installed which will automatically shut off the hydraulic power to the flap actuating motors whenever an asymmetrical condition exists. One method of accomplishing this means is described in Lockheed Service Bulletin No. 49/SB-794 for the 49/749 Series and No. 1049/SB-2270 for the 1049 Series.

## Affected data sheets (2) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [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 6A5](https://openairdocs.org/tcds/6A5): Lockheed Martin Aeronautics Company; names 2 of 8 models: 1049C-55, 1049-54

## 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: 2 (2 by airframe model, 0 by engine model)
- Makers: Lockheed 2

Models with the most aircraft:

- [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)

All 2 models: https://openairdocs.org/ad/56-25-04/models.md
Every aircraft: https://openairdocs.org/ad/56-25-04/aircraft.md

Its text cites no advisory circulars or STCs.

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