{"id":"F2020L00555","name":"AD/AL 250/91 Amdt 2 Engine Compressor Module - Removal from Service","slug":"ad-al-250-91-amdt-2-engine-compressor-module-removal-from-service","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":100120,"registerId":"commonwealth-F2020L00555-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Rolls-Royce (Allison) Turbine Engines - ","sectionType":"part","heading":"Rolls-Royce (Allison) Turbine Engines - 250 Series","content":"# Rolls-Royce (Allison) Turbine Engines - 250 Series\n\n| AD/AL 250/91 Amdt 2 | Engine Compressor Module - Removalfrom Service | 10/2020 |\n| ------------------- | ---------------------------------------------- | ------- |\n\n```html\n

Applicability:

All Rolls-Royce Allison 250 series engines.

Requirement:

1. Review engine logbooks and determine if a compressor module with a serial number listed in Table 1 and 2 is installed in the engine.

2. Remove affected Rolls-Royce Allison C20B series and C20R series compressor modules with a serial number listed in Table 1 from service.

3. Remove affected Rolls-Royce Allison C18 series, C28 series, C30 series and C47 series compressor modules with a serial number listed in Table 2 from service.

4. All affected Rolls-Royce Allison C20B series and C20R series compressor modules must be sent to an approved maintenance organisation to be assessed in accordance with Original Equipment Manufacturer (OEM) specifications.

Compressor rotor wheels in the position numbers listed in Table 1 for a module with a serial number listed in Table 1 must be replaced before returning the compressor module to service, the subject removed rotor wheels must be quarantined or scrapped so they cannot be installed as a serviceable part.

5. All affected Rolls-Royce Allison C18 series, C28 series, C30 series and C47 series compressor modules must be sent to an approved maintenance organisation to be assessed in accordance with OEM specifications.

Compressor impellers must be replaced, or may only be returned to service through an approved OEM repair scheme before returning the compressor module to service. Impellers deemed as not recoverable must be quarantined or scrapped so they cannot be installed as a serviceable part.

Table 1: Affected C20B and C20R compressor modules.

Affected Compressor Module Serial Numbers (S/N):

C20B series

C20R series

Module S/N:

Compressor Rotor Wheel Position Number:

Module S/N:

Compressor Rotor Wheel Position Number:

CAC23900

1, 2, 3 & 4

CAC15280

1

Table 1 (Continued)

Module S/N:

Compressor Rotor Wheel Position Number:

Module S/N:

Compressor Rotor Wheel Position Number:

CAC30243

CAC30972

CAC31261F

CAC31394

CAC32128

CAC33247

CAC33931

CAC34205

CAC35463

CAC36132

CAC37795

CAC37814

CAC37978

CAC38521

CAC39053

CAC40090

CAC40093

CAC40446

CAC40483

CAC40560

CAC41262

CAC41846

CAC41917

CAC42465

CAC43498

1

1

1

To be advised (TBA).

2, 3 & 4

1 & 6

1 & 2

TBA.

4

2, 3, 4, & 6

1

1, 2, 3, 4 & 5

1

TBA.

TBA.

1

1

TBA.

TBA.

1 & 5

1

TBA.

1

1 & 4

1 & 5

CAC15850

CAC15973

CAC28209

1 & 4

1 & 4

3 & 4

Table 2: Affected C18, C28, C30 and C47 compressor modules.

Affected Compressor Module Serial Numbers (S/N):

C18 series

C28 series

C30 series

C47 series

CAC21705B

CAC28017

CAC28022

CAC28048

CAC28119

CAC70026

CAC70243

CAC70779

CAC28046

CAC90011

CAC90052

CAC90069

CAC90507

CAC90719

CAC91119

CAC91305

CAC91311

CAC91507

CAC44094

CAC44293

CAC44294

CAC45072

CAC45750

Table 2 (Continued)

C18 series

C28 series

C30 series

C47 series

CAC91607

CAC91623

CAC91635

CAC91820

CAC98516

CAC98537

Compliance:

1. Before further flight.

2. For C20B and C20R series compressor modules: Before further flight.

3. For C18, C28, C30 and C47 series compressor modules: the earlier of the following:

(i) within 50 hours’ time in service;

(ii) 12 April 2020;

(iii) next engine shop visit.

(iv) for C47 compressor module Serial Number CAC44094, within 50 hours’ time in service or 4 June 2020.

4. Before returning to service.

5. Before returning to service.

For aircraft located away from a maintenance facility, a special flight permit may be issued for one non-revenue ferry flight to return the aircraft to the nearest maintenance facility to carry out the requirements of this AD.

CASA is to be notified of any engines found to have an affected module fitted via the Defect Reporting Service.

Note 1: Civil Aviation Authority of New Zealand (CAA NZ) Airworthiness Directive DCA/AL250/60A has been referenced as a source document for Tables 1 and 2.

Note 2: The primary safety concern with C18, C28, C30 and C47 series compressor modules relates to unauthorised drilling of compressor impellers for balancing.

Note 3: The primary safety concern with C20B and C20R series compressor modules relates to blending repairs on compressor rotor wheels with the lack of shot peening.

This AD commences on 8 May 2020.

Background:

A recent audit of a New Zealand maintenance organisation by CAA NZ has determined that compressor module inspections and repairs of these modules may not have been carried out in accordance with approved Rolls-Royce procedures.

\n```\n\n| | Amendment 1 adds the C18 series compressor module, introduces additional serial numbers to each module series and makes minor editorial changes throughout the text.Amendment 2 adds C47 series compressor module serial number CAC44094, with compliance action time of 50 hours’ time in Service or 4 June 2020. |\n| --- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n\n![A drawing of a face\nDescription automatically generated](image.001.jpeg)\n\nPieter van Dijk \nDelegate of the Civil Aviation Safety Authority\n\n4 May 2020","sortOrder":0},{"sectionNumber":"AD/AL 250/91 Amdt 2","sectionType":"part","heading":"AD/AL 250/91 Amdt 2","content":"## AD/AL 250/91 Amdt 2","sortOrder":1},{"sectionNumber":"Engine Compressor Module - Removalfrom S","sectionType":"part","heading":"Engine Compressor Module - Removalfrom Service","content":"## Engine Compressor Module - Removal \nfrom Service","sortOrder":2},{"sectionNumber":"10/2020","sectionType":"part","heading":"10/2020","content":"## 10/2020","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":6,"scope_assessment":{"changed":true,"description":"Scope was expanded by amendments: Amendment 1 added the C18 series and additional module serial numbers; Amendment 2 added C47 serial number CAC44094 and a specific compliance time (50 hours TIS or 4 June 2020). The instrument therefore broadened the set of affected modules and introduced additional compliance timing."},"complexity_factors":["Large list of specific affected serial numbers across four module series (C18, C20B, C20R, C28, C30, C47)","Different remedial actions by series (rotor wheel replacement/quarantine vs impeller replacement/OEM repair)","Multiple and varying compliance deadlines (before further flight; within 50 hours; fixed calendar dates; next shop visit)","Requirement to use approved maintenance organisations and OEM specifications, creating procedural and supply dependencies","Recordkeeping and logbook review obligation to identify affected modules","Reporting obligation to CASA via Defect Reporting Service and potential need for special flight permits for ferry flights"],"plain_english_summary":"Requires operators of all Rolls‑Royce (Allison) 250‑series engines to check logbooks for listed compressor‑module serial numbers and remove affected modules from service. C20B/C20R modules must go to an approved maintenance organisation and have specified rotor wheels replaced and quarantined; C18/C28/C30/C47 modules must be assessed by an approved maintenance organisation and have impellers replaced or returned only under an OEM repair scheme. Compliance times vary (some before next flight; others within 50 hours, set dates, or next shop visit)."},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":true,"description":"The original AD has expanded significantly through amendments. Amendment 1 added the C18 series and additional serial numbers across all affected series. Amendment 2 added the C47 series with a specific serial number (CAC44094) and its own compliance deadline. What began as a targeted directive has grown to cover six distinct engine series (C18, C20B, C20R, C28, C30, C47) with different technical issues and compliance timelines."},"complexity_factors":["Multiple overlapping compliance deadlines depending on engine series (immediate vs. 50 hours vs. calendar dates)","Two distinct technical defects requiring different remedial actions (rotor wheel replacement vs. impeller replacement/repair)","Extensive serial number tables (Table 1 and Table 2) with specific position numbers for affected components","Cross-reference to New Zealand aviation authority (CAA NZ) source documentation","Nested requirements: removal → assessment → replacement → quarantine/scrap → return to service","Exception for ferry flights (special flight permit) with specific non-revenue restriction","Amendment history tracking (Amendment 1 and 2) showing evolution of scope"],"plain_english_summary":"This CASA Airworthiness Directive orders owners/operators of Rolls‑Royce (Allison) 250 series engines to check logbooks, ground and remove specified compressor modules suspected of improper repairs/inspections, and have affected parts assessed, repaired or replaced by approved facilities. It also requires quarantine or scrapping of non‑conforming rotor wheels/impellers.\n\nIt affects operators of helicopters and light aircraft using these engines and is mandatory because the defects (unauthorised drilling and improper blending repairs) can cause catastrophic engine failure."},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-al-250-91-amdt-2-engine-compressor-module-removal-from-service","history":"/api/acts/ad-al-250-91-amdt-2-engine-compressor-module-removal-from-service/history","analysis":"/api/acts/ad-al-250-91-amdt-2-engine-compressor-module-removal-from-service/analysis","conflicts":"/api/acts/ad-al-250-91-amdt-2-engine-compressor-module-removal-from-service/conflicts","importantCases":"/api/acts/ad-al-250-91-amdt-2-engine-compressor-module-removal-from-service/important-cases","documents":"/api/acts/ad-al-250-91-amdt-2-engine-compressor-module-removal-from-service/documents"}}