# AD 48-49-03: Electrical Circuit Inspection

- Type: Airworthiness directive
- Status: Current
- Products: Boeing DC-6, DC-6A and DC-6B
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Large airplane
- Registered aircraft: 17 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/7DA5CC2F3CEE1AE7862569BC005AD5FD.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/48-49-03

## The airworthiness directive

48-49-03 DOUGLAS: Applies to All DC-6 Airplanes.

Compliance required not later than March 1, 1949.

To reduce the probability of a loss of power for electrical circuits considered to be essential in flight, these essential circuits were designed to be connected directly to the master bus. Other less essential circuits are connected to the master bus through a 500-ampere Burndy limiter (fuse).

In an undetermined number of aircraft some of the essential circuits were inadvertently connected to the distribution bus rather than to the master bus.

It is necessary, therefore, that all DC-6 aircraft be inspected and such rewiring as necessary be done to assure that the following circuit protectors are connected to the master bus:

Radio Master (B1-102), Fuel Booster Pumps (B1-63, 97), Invertor Power (B1-111, 116), Propeller Booster (Curtiss Propellers only, F1-28, 29), Propeller Control (Curtiss: B1-141, 142, 143, 144. Hamilton Standard: B1-188, 189, 190, 191), Propeller Synchronizer (B1-145), Governor Control (Hamilton Standard only, B1-192), Generator Control Panel (Eclipse Generator System only, B1-246, 247, 248, 249. Reference Douglas Service Bulletin DC-6 No. 329.

(Douglas Service Letter A214-T.3338/TFW dated October 22, 1948 covers this same subject.)

## Affected data sheets (3) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS 6A3](https://openairdocs.org/tcds/6A3): The Boeing Company; names 1 of 3 models: DC-6A
- [TCDS 6A4](https://openairdocs.org/tcds/6A4): The Boeing Company; names 1 of 2 models: DC-6B
- [TCDS A-781](https://openairdocs.org/tcds/A-781): The Boeing Company; names 1 of 1 models: DC-6

## 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: 17 (17 by airframe model, 0 by engine model)
- Makers: Douglas 17

Models with the most aircraft:

- [Douglas DC-6B](https://openairdocs.org/model/douglas-dc-6b): 9 aircraft (airframe model)
- [Douglas DC-6A](https://openairdocs.org/model/douglas-dc-6a): 7 aircraft (airframe model)
- [Douglas DC-6](https://openairdocs.org/model/douglas-dc-6): 1 aircraft (airframe model)

All 3 models: https://openairdocs.org/ad/48-49-03/models.md
Every aircraft: https://openairdocs.org/ad/48-49-03/aircraft.md

Its text cites no advisory circulars or STCs.

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