# AD 48-13-01: Generator Control Box Insulation

- Type: Airworthiness directive
- Status: Current
- Products: Textron D18C and D18S
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Small airplane
- Registered aircraft: 55 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/11A810852541206A86256A1C0072EC8E.0001
- DRS record last changed: January 21, 2026
- Page: https://openairdocs.org/ad/48-13-01

## The airworthiness directive

48-13-01 BEECH: Applies to All D18S, D18C Airplanes Equipped With Pilot's Reclining Seats and Having the Generator Control Box Mounted on Bulkhead No. 5.

To be accomplished not later than July 1, 1948.

To prevent a short circuit between the hot terminal of the generator control box and bulkhead No. 5, rivet a 0.016 phenolic sheet 13/4 x 3 inches between the bulkhead web and the first horizontal angle immediately above the generator control box. The sheet should extend downward from the angle to the web cutout and provide positive insulation between the web and the hot post of the generator control box. If a phenolic strip has previously been installed at this point, an additional strip will not be necessary.

(Beech Service Letter No. D18-23 covers this same subject.)

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS A-765](https://openairdocs.org/tcds/A-765): Textron Aviation Inc.; names 2 of 17 models: D18S, D18C

## 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: 55 (55 by airframe model, 0 by engine model)
- Makers: Beech 55

Models with the most aircraft:

- [Beech D18S](https://openairdocs.org/model/beech-d18s): 55 aircraft (airframe model)

All 1 models: https://openairdocs.org/ad/48-13-01/models.md
Every aircraft: https://openairdocs.org/ad/48-13-01/aircraft.md

Its text cites no advisory circulars or STCs.

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