# AD 59-18-02: Fuel Line Modification

- Type: Airworthiness directive
- Status: Current
- Products: Textron C-45G, C-45H, D18S, TC-45G and TC-45H
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Small airplane
- Registered aircraft: 116 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/99CB8169125F87CE86256A080072319B.0001
- DRS record last changed: January 21, 2026
- Page: https://openairdocs.org/ad/59-18-02

## The airworthiness directive

59-18-02 BEECH: Applies to All Model C45G, TC45G, C45H, TC45H and D18S Airplanes.

Compliance required as indicated.

Corrosion of fuel supply lines in the wing root area can result from the flexible cockpit hot air duct touching the aluminum fuel line. Fuel line leaks due to this corrosion may cause fuel system malfunctioning or hazardous accumulations of fuel and fumes in the wings or cabin. To prevent these conditions, accomplish the following:

  (a) Compliance required not later than October 15, 1959.

  (1) Inspect the 5/8-inch O.D. fuel line (Beech P/N's 407-189686 LH and 407-189731 RH) beneath each battery installation on both sides of the airplane for indications of corrosion. Replace the lines if damaged.

  (2) Install 5/8-inch I.D. x 1/16-inch tubing (Tygon tubing manufactured by U.S. Stoneware, Akron 9, Ohio) split lengthwise over the fuel lines (407-189686 LH and 407- 189731 RH) in the area of the cockpit hot air duct. Secure the split tubing by taping.

  (3) Obtain adequate clearance between the fuel line and the cabin hot air duct by installing a suitable double clamp on the line and duct.

  (b) Compliance required at each periodic airplane inspection after accomplishment of (a).

  (1) Remove split Tygon tubing from fuel supply lines (407-189686 LH and 407-189731 RH) and inspect lines for corrosion. Replace fuel lines if necessary.

  (2) Reinstall split Tygon tubing and double clamp between cabin hot air duct and fuel line as outlined in (a)(2) and (a)(3).

(Beech Service Bulletin No. 68, Model D18S issued February 1959, 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 5 of 17 models: TC-45G, C-45H, C-45G, TC-45H, D18S

## 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: 116 (116 by airframe model, 0 by engine model)
- Makers: Beech 116

Models with the most aircraft:

- [Beech D18S](https://openairdocs.org/model/beech-d18s): 55 aircraft (airframe model)
- [Beech C-45H](https://openairdocs.org/model/beech-c-45h): 50 aircraft (airframe model)
- [Beech C-45G](https://openairdocs.org/model/beech-c-45g): 9 aircraft (airframe model)
- [Beech TC-45G](https://openairdocs.org/model/beech-tc-45g): 2 aircraft (airframe model)

All 5 models: https://openairdocs.org/ad/59-18-02/models.md
Every aircraft: https://openairdocs.org/ad/59-18-02/aircraft.md

Its text cites no advisory circulars or STCs.

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.