# AD 93-25-05: Driveshaft Flex Coupling Bolts, Bushings, and Nuts

- Type: Airworthiness directive
- Status: Current
- Products: Rolls-Royce 250-C20S with STC SE2352NM
- Effective: February 22, 1994
- Superseded by: Nothing supersedes this AD
- Product type: Engine
- Amendment: 39-8771
- Docket: 91-ANE-50
- Registered aircraft: 611 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/68D1937FF139E17486256846004DD116.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/93-25-05

## The airworthiness directive

93-25-05 ALLISON: Amendment 39-8771. Docket 91-ANE-50. Applicability: Allison Model 250-C20S turbine engines, as modified by Soloy Conversion, Ltd., Supplemental Type Certificate (STC) SE2352NM, installed on but not limited to Cessna 206 and 207 airplanes. Compliance: Required as indicated, unless accomplished previously. To prevent bolt fretting and fatigue failure, main engine driveshaft detachment, and engine failure, accomplish the following: (a) Within 90 days after the effective date of this AD, inspect the main engine driveshaft and replace the driveshaft flex coupling bolts, bushings, and nuts in accordance with Soloy Corporation Service Bulletin No. 04- 780, dated December 11, 1991. Replace with a serviceable part those main engine driveshafts with elongated bolt holes. (b) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle Aircraft Certification Office. The request should be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Seattle Aircraft Certification Office. NOTE: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Seattle Aircraft Certification Office. (c) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate the airplane to a location where the requirements of this AD can be accomplished. (d) The inspection, and replacement, if necessary, shall be done in accordance with the following service bulletin:

Document No. Pages Revision Date Soloy Corporation Service Bulletin No. 04-780 1-3 Original December 11, 1991

Total Pages: 3.

This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Soloy Corporation, 450 Pat Kennedy Way, S.W., Olympia, WA 98501- 7298; telephone (206) 754-7000. Copies may be inspected at the FAA, New England Region, Office of the Assistant Chief Counsel, 12 New England Executive Park, Burlington, MA; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. (e) This amendment becomes effective on February 22, 1994.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS E4CE](https://openairdocs.org/tcds/E4CE): Rolls-Royce Corporation; names 1 of 23 models: 250-C20S

## 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: 611 (0 by airframe model, 611 by engine model)
- Makers: Bell 365, Hughes Helicopters 58, Mcdonnell Douglas Helicopter 56, Hiller 19, Agusta 18, Hughes 14, Aerospatiale 10, Enstrom Helicopter 10, MD Helicopters 10, Cessna 9

Models with the most aircraft:

- [Allison 250-C20 series](https://openairdocs.org/engine/allison-250-c20-series): 530 aircraft (engine model)
- [Allison 250 series](https://openairdocs.org/engine/allison-250-series): 79 aircraft (engine model)
- [Rolls-Royce 250-C20S](https://openairdocs.org/engine/rolls-royce-250-c20s): 2 aircraft (engine model)

All 4 models: https://openairdocs.org/ad/93-25-05/models.md
Every aircraft: https://openairdocs.org/ad/93-25-05/aircraft.md

## Related documents

- [STC SE2352NM](https://openairdocs.org/stc/SE2352NM): Modification of turbine engine.. Fifty-Ten-Yankee LLC, Named in the applicability

---
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.