# AD 93-25-17: Gas Generator Turbine (GGT) Disks and Cooling Plates

- Type: Airworthiness directive
- Status: Current
- Products: General Electric CT7-2A, CT7-5A2, CT7-6, CT7-7A and CT7-9C
- Effective: February 2, 1994
- Published: January 3, 1994, 59 FR 3–4
- Issued as: Final rule
- Superseded by: Nothing supersedes this AD
- Product type: Engine
- Amendment: 39-8781
- Docket: 92-ANE-08
- Registered aircraft: 79 may be affected, by airframe or engine model (OpenAirDocs)
- Federal Register: https://www.federalregister.gov/documents/1994/01/03/93-31908/airworthiness-directives-general-electric-ct7-series-turboprop-and-turboshaft-engines
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/3D7AEAE4BF320C9086256846005757B8.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/93-25-17

## The airworthiness directive

93-25-17 GENERAL ELECTRIC: Amendment 39-8781. Docket No. 92-ANE-08. Applicability: General Electric (GE) Models CT7-5A2, -7A, and -9C Turboprop Engines; and Models CT7-2A, and -6 Turboshaft Engines, incorporating gas generator turbine (GGT) disks and cooling plates, as listed by Part Number (P/N) and Serial Number (S/N) in GE CT7 Turboprop Service Bulletin (SB) A72-252, dated August 31, 1990; GE CT7 Turboshaft SB A72-17, and GE CT7 Turboshaft SB A72-18, both dated September 10, 1990, installed on, but not limited to, Saab 340A, Casa CN235-10, Bell 214ST, and European Helicopter Industries EH101. Compliance: Required as indicated, unless accomplished previously. To prevent fatigue cracks that can result in uncontained engine failure, accomplish the following: (a) Remove from service the affected GE Model(s) CT7-5A2, -7A, and -9C engines GGT rotor stage 1 and 2 disks, and stage 2 forward and aft cooling plates, prior to exceeding the "Max total allowable cycles"; as listed in GE CT7 Turboprop SB A72-252, dated August 31, 1990, and replace with serviceable parts. (b) Remove from service the affected GE Model(s) CT7-6 engine GGT rotor stage 1 disk and stage 2 forward cooling plate prior to exceeding the "Max total allowable cycles"; as listed in GE CT7 Turboprop SB A72-17, dated September 10, 1990, and replace with serviceable parts. (c) Remove from service the affected GE Model(s) CT7-2A engine GGT rotor stage 2 disk and stage 2 forward cooling plate prior to exceeding the "Max total allowable cycles"; as listed in GE CT7 Turboshaft SB A72-18, dated September 10, 1990, and replace with serviceable parts. (d) 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, Engine Certification Office. The request should be forwarded through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, EngineCertification Office. NOTE: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Engine Certification Office. (e) 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. (f) The removals and replacements of the affected rotor stage disks and cooling plates shall be done in accordance with the following service bulletins:

DOCUMENT NO. PAGE NO. ISSUE DATE GE CT7 Turboprop SB A72-252 1-13 Original Aug 31, 1990 TOTAL PGS: 13

GE CT7 Turboshaft SB A72-17 1-4 Original Sep 10, 1990 TOTAL PGS: 4

GE CT7 Turboshaft SB A72-18 1-4 Original Sep 10, 1990 TOTAL PGS: 4

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 General Electric Aircraft Engines, 1000 Western Avenue, Lynn, Massachusetts 01910. Copies may be inspected at the FAA, New England Region, Office of the Assistant Chief Counsel, Attn: Rules Docket No. 92-ANE-08, 12 New England Executive Park, Burlington, Massachusetts; or at the Office of the Federal Register, 800 North Capitol Street NW., suite 700, Washington, DC. (g) This amendment becomes effective on February 2, 1994.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS E8NE](https://openairdocs.org/tcds/E8NE): General Electric Company GE Aviation; names 5 of 30 models: CT7-9C, CT7-7A, CT7-2A, CT7-6, CT7-5A2

## 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: 79 (0 by airframe model, 79 by engine model)
- Makers: Saab-Scania 38, Bell 17, Construcciones Aeronauticas 5, Bell Helicopter Textron 4, Saab-Fairchild 4, Sikorsky 4, Saab 3, Agustawestland 2, Leonardo S P A 2

Models with the most aircraft:

- [GE CT7-SER series](https://openairdocs.org/engine/ge-ct7-ser-series): 43 aircraft (engine model)
- [GE CT7 series](https://openairdocs.org/engine/ge-ct7-series): 26 aircraft (engine model)
- [GE CT7-5A2](https://openairdocs.org/engine/ge-ct7-5a2): 7 aircraft (engine model)
- [GE CT7-2A](https://openairdocs.org/engine/ge-ct7-2a): 3 aircraft (engine model)

All 4 models: https://openairdocs.org/ad/93-25-17/models.md
Every aircraft: https://openairdocs.org/ad/93-25-17/aircraft.md

No proposed rule in this release led to it. Its text cites no advisory circulars or STCs.

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