AD 68-22-02
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Rolls-Royce Corporation | 250-C10B (T63-A-5A) | ALLISON Model 250-C18, 250-C18A, and 250-C10B Engines |
| engine | Rolls-Royce Corporation | 250-C18 | ALLISON Model 250-C18, 250-C18A, and 250-C10B Engines |
| engine | Rolls-Royce Corporation | 250-C18A | ALLISON Model 250-C18, 250-C18A, and 250-C10B Engines |
Unsafe Condition
Compressor assemblies with serial numbers prior to specified limits may experience failure due to insufficient strength, leading to engine failure.
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Required Actions
Modify engines in accordance with Allison Commercial Engine Bulletins 250 CEB-51 and 250 CEB-52. Until modified, restrict N1 rpm to ≤96.5% except during takeoff (limited to 2 minutes), and limit generator load to ≤60 amps above 70% N1 rpm.
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Compliance Time
on or before May 1, 1969
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Affected Aircraft
Rolls-Royce Corporation Model 250-C18 (compressor assemblies serial numbers prior to CAC 21073), Model 250-C18A (compressor assemblies serial numbers prior to CAC 20202), and all Model 250-C10B engines.
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Federal Register Abstract
Compressor Assemblies
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_68-22-02.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 68-22-02 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: ALLISON Model 250-C18, 250-C18A, and 250-C10B Engines Subject: Compressor Assemblies Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 11/01/1968 Make: Rolls-Royce Corporation Model: 250-C10B (T63-A-5A) | 250-C18 | 250-C18A Product Type: Engine Product Subtype: Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 68-22-02 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 68-22-02 SUBJECT HEADING: ALLISON Model 250-C18, 250-C18A, and 250-C10B Engines ACTION: SUMMARY: DATES: Effective November 1, 1968. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 68-22-02 ALLISON: Applies to Model 250-C18, 250-C18A, and 250-C10B engines, to wit Allison Model 250-C18 engines having compressor assemblies installed with serial numbers prior to Serial Number CAC 21073; Model 250-C18A engines having compressor assemblies installed with serial numbers prior to Serial Numbers CAC 20202; and all Model 250-C10B engines. The Allison model engines to which this AD is applicable must be modified in accordance with Allison Commercial Engine Bulletin 250 CEB-51 and 250 CEB-52 dated October 16, 1968, on or before May 1, 1969. Until modified, the engines to which this AD is applicable may be operated provided: (1) They are not operated with N1 (gas producer) rpm greater than 96.5 percent, except for "takeoff"; (2) Time operated at "takeoff" does not exceed two (2) minutes; (3) The generator load does not exceed 60 amps when the engine is operating above 70 percent N1 rpm.* NOTE: This amendment becomes effective November 1, 1968. *As a result of these operating restrictions, the rotorcraft flight manual and certain power plant instrument markings for the Bell 206A, the Fairchild Hiller FH-1100, and the Hughes 369A and 369H helicopters in which these engines are installed may require modifications or the installation of suitable placards. The necessary information for such changes is available from the manufacturers of these helicopters. FOOTER:
Document Text
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AD Final Rules - DRS_68-22-02.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 68-22-02 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: ALLISON Model 250-C18, 250-C18A, and 250-C10B Engines Subject: Compressor Assemblies Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 11/01/1968 Make: Rolls-Royce Corporation Model: 250-C10B (T63-A-5A) | 250-C18 | 250-C18A Product Type: Engine Product Subtype: Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 68-22-02 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 68-22-02 SUBJECT HEADING: ALLISON Model 250-C18, 250-C18A, and 250-C10B Engines ACTION: SUMMARY: DATES: Effective November 1, 1968. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 68-22-02 ALLISON: Applies to Model 250-C18, 250-C18A, and 250-C10B engines, to wit Allison Model 250-C18 engines having compressor assemblies installed with serial numbers prior to Serial Number CAC 21073; Model 250-C18A engines having compressor assemblies installed with serial numbers prior to Serial Numbers CAC 20202; and all Model 250-C10B engines. The Allison model engines to which this AD is applicable must be modified in accordance with Allison Commercial Engine Bulletin 250 CEB-51 and 250 CEB-52 dated October 16, 1968, on or before May 1, 1969. Until modified, the engines to which this AD is applicable may be operated provided: (1) They are not operated with N1 (gas producer) rpm greater than 96.5 percent, except for "takeoff"; (2) Time operated at "takeoff" does not exceed two (2) minutes; (3) The generator load does not exceed 60 amps when the engine is operating above 70 percent N1 rpm.* NOTE: This amendment becomes effective November 1, 1968. *As a result of these operating restrictions, the rotorcraft flight manual and certain power plant instrument markings for the Bell 206A, the Fairchild Hiller FH-1100, and the Hughes 369A and 369H helicopters in which these engines are installed may require modifications or the installation of suitable placards. The necessary information for such changes is available from the manufacturers of these helicopters. FOOTER:
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Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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