Commonwealth legislation

AD/AL 250/41 Amdt 5 - Third Stage Turbine Wheel - Inspection and RPM Operational Restrictions

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Commonwealth

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legislative instrument

Plain English Summary

6/10 complexity

This Airworthiness Directive requires operators of specified Allison 250‑series engines without solid blade shroud third‑stage turbine wheels to install cockpit/indicator placards and to limit engine RPM in certain ranges until the affected wheels are replaced. It applies to listed 250‑C20 and 250‑B17 variants and matters because it changes ground and operating speed limits and obliges operators to carry out replacements and labelling in line with the manufacturer’s revision.

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Direct links to the current provisions in AD/AL 250/41 Amdt 5 - Third Stage Turbine Wheel - Inspection and RPM Operational Restrictions.

AD/AL 250/41 Amdt 5 - Third Stage Turbine Wheel - Inspection and RPM Operational Restrictions

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY

SCHEDULE OF AIRWORTHINESS DIRECTIVES

View image in the official source
Allison Turbine Engines - 250 Series

AD/AL 250/41

Amdt 5

Third Stage Turbine Wheel - Inspection and RPM Operational Restrictions

5/84

Applicability: All models 250-C20, C20B, C20F, B17, B17B, B17C and B17D not fitted with solid blade shroud third stage turbine wheels.

Document: 1. Allison 250-C20, C20B, C20F, CEB-A-1174 Rev. 3; or

Allison 250-B17, B17B, B17C B17D, CEB-A-1146 Rev. 3.

Note: FAA AD 83-03-02 R1 also refers.

In addition, until all affected turbine wheels have been replaced with solid blade shroud wheels, it will be necessary to install a placard on or adjacent to the aircraft installed N2 tacho indicator, prohibiting sustained operation between 90 and 98% N2.

And

For C20, C20B, C20F powered aircraft only install a placard in clear view of the pilot stating that:

“DURING ALL GROUND OPERATION, THE ENGINE N1 SPEED MUST BE MAINTAINED AT GROUND IDLE EXCEPT DURING TRANSIENT OPERATION, WHEN PERFORMING REQUIRED OPERATIONAL CHECKS, IN HIGH OR GUSTY WIND CONDITIONS OR WHERE SAFETY WOULD BE ADVERSELY AFFECTED.”

And

For B17, B17B, B17C B17D powered aircraft only install a placard in clear view of the pilot stating that:

“DURING ALL GROUND OPERATION, THE ENGINE N2 SPEED MUST BE MAINTAINED BELOW 90%N2 RPM EXCEPT DURING TRANSIENT OPERATION, WHEN PERFORMANCE REQUIRED OPERATIONAL CHECKS IN HIGH OR GUSTY WIND CONDITIONS OR WHERE SAFETY WOULD BE ADVERSELY AFFECTED.”

Compliance: In accordance with the reference document.

Background: This Directive is raised in issue to ensure compliance with Revision 3 of the manufacturers document which is a complete reissue. It now requires replacement of non-sold blade shroud wheels on a tighter phased schedule and it is no longer allowable to re-install any superseded wheel.

Installation of third stage turbine wheel with solid blade shroud deletes the engine operating speed restrictions imposed by this Directive.

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY

SCHEDULE OF AIRWORTHINESS DIRECTIVES

Source text

Sourced from the Federal Register of Legislation (legislation.gov.au), CC BY 4.0.

1 AD/AL 250/41 Amdt 5 - Third Stage Turbine Wheel - Inspection and RPM Operational Restrictions

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY

SCHEDULE OF AIRWORTHINESS DIRECTIVES

Allison Turbine Engines - 250 Series

AD/AL 250/41

Amdt 5

Third Stage Turbine Wheel - Inspection and RPM Operational Restrictions

5/84

Applicability: All models 250-C20, C20B, C20F, B17, B17B, B17C and B17D not fitted with solid blade shroud third stage turbine wheels.

Document: 1. Allison 250-C20, C20B, C20F, CEB-A-1174 Rev. 3; or

Allison 250-B17, B17B, B17C B17D, CEB-A-1146 Rev. 3.

Note: FAA AD 83-03-02 R1 also refers.

And

For C20, C20B, C20F powered aircraft only install a placard in clear view of the pilot stating that:

And

For B17, B17B, B17C B17D powered aircraft only install a placard in clear view of the pilot stating that:

Compliance: In accordance with the reference document.

Installation of third stage turbine wheel with solid blade shroud deletes the engine operating speed restrictions imposed by this Directive.

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY

SCHEDULE OF AIRWORTHINESS DIRECTIVES