# AD 61-21-05: Compass Circuit Breakers

- Type: Airworthiness directive
- Status: Current
- Products: Lockheed Martin 188A and 188C
- Effective: November 2, 1961
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Large airplane
- Registered aircraft: 4 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/6177D8AAC5FFACEA862569B300725430.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/61-21-05

## The airworthiness directive

61-21-05 LOCKHEED: Amdt. 342 Part 507 Federal Register October 3, 1961. Applies to All Model 188 Aircraft.

Compliance required as indicated.

Several instances of inadvertent tripping of compass circuit breakers have occurred due to bumping the ganging bar by the occupant of the observers seat. Due to the effect of the loss of heading information upon operational safety, accomplishment of the following is required:

Within the next 100 hours' time in service after the effective date of this AD, inspect the pilot's and copilot's compass circuit breakers, and if the circuit breakers are ganged together, either remove the ganging bars, or install a protective guard which precludes inadvertent operation of the ganging bar. (These circuit breakers are located in the lowest circuit breaker panel beside the observers seat on the left side of the flight deck.)

This directive effective November 2, 1961.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS 4A22](https://openairdocs.org/tcds/4A22): Lockheed Martin Corporation; names 2 of 2 models: 188A, 188C

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

Models with the most aircraft:

- [Lockheed 188C](https://openairdocs.org/model/lockheed-188c): 3 aircraft (airframe model)
- [Lockheed 188A](https://openairdocs.org/model/lockheed-188a): 1 aircraft (airframe model)

All 2 models: https://openairdocs.org/ad/61-21-05/models.md
Every aircraft: https://openairdocs.org/ad/61-21-05/aircraft.md

Its text cites no advisory circulars or STCs.

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