{"id":"F2012L00544","name":"AD/AL 250/86 Amdt 3 - Compressor Adaptor Coupling","slug":"ad-al-250-86-amdt-3-compressor-adaptor-coupling","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":88743,"registerId":"commonwealth-F2012L00544-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Allison Turbine Engines - 250 Series","sectionType":"division","heading":"Allison Turbine Engines - 250 Series","content":"### Allison Turbine Engines - 250 Series\n\n| AD/AL 250/86 Amdt 3 | Compressor Adaptor Coupling | 5/2012 |\n| ------------------- | --------------------------- | ------ |\n\n```html\n

Applicability:

Rolls-Royce Corporation (formerly Allison Engine Company, Allison Gas Turbine Division, and Detroit Diesel Allison) 250-B17, -B17B, -B17C, -B17D, -B17E,
250-C20, -C20B, -C20F, -C20J, -C20S, and -C20W series turboprop and turboshaft engines with the compressor adaptor couplings installed listed in Table 1 of this Directive.

Table 1. - Affected Compressor Adaptor Couplings

Manufacturer

Affected part numbers

Alcor Engine Company (Alcor)

P/Ns 23039791AL.
23039791AL-1/-2/-3.

EXTEX Ltd. (EXTEX)

A23039791.
E23039791.
E23039791-1/-2/-3.
EH23039791.
EH23039791-1/-2/-3.

Rolls-Royce Corporation (RRC)

23039791-1/-2/-3.

Superior Air Parts (SAP)

A23039791.

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These engines are installed on, but not limited to, the aircraft in Table 2 of this Directive:

Table 2. - Applicable Aircraft

Helicopters

Agusta Models.
A109, A109A, A109A II.

Bell Models.
206A, 206B, 206L.

Enstrom Models.
TH-28, 480, 480B.

Eurocopter France Models.
AS355E, AS355F, AS355F1, AS355F2.

Eurocopter Deutschland Models.
BO-105C, BO-105S.

MDHI Models.
369D, 369E, 369H, 369HM, 369HS, 369HE.

Schweizer Model 269D.

Aeroplanes

B-N Group Ltd. Model.
BN-2T.

Requirement:

1. Alcor Compressor Adaptor Couplings

Remove Alcor compressor adaptor couplings, P/Ns 23039791AL, 23039791AL-1, -2, and -3 from service.

2. EXTEX and SAP Compressor Adaptor Couplings

Remove EXTEX and SAP compressor adaptor couplings, P/Ns A23039791, E23039791, E23039791-1, -2, and -3, EH23039791, and EH23039791-1, -2, and -3, from service.

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3. RRC Compressor Adaptor Couplings

Remove RRC compressor adaptor couplings, P/Ns 23039791-1, -2, and -3 from service.

4. Installation Requirements for Compressor Adaptor Couplings

Machine the compressor impeller as follows:

(a) Select and measure the pilot outside diameter (OD) of a new larger dash size coupling.

(b) For example, if a -1 coupling was removed, a -2 coupling must be installed.

(c) If a -3 coupling is removed, a new impeller is required.

(d) Machine the inside diameter (ID) of the compressor impeller to achieve a fit of 0.0000 to -0.0013 inch. No fretting is allowed on the impeller after machining.

(e) Due to previous fretting, an impeller with a -1 coupling removed might have to be machined for a -3 coupling. Plating of the impeller ID is not allowed.

(f) Fluorescent penetrant inspect the impeller.

(g) Install a new compressor adaptor coupling, P/N 23076559-2 or -3; or

(h) If a new impeller is installed, then install compressor adaptor coupling, P/N 23076559-1.

(i) Heating of the impeller per the engine overhaul manual is required to install the coupling to achieve the target fit specified in Table 3 of this Directive:

New adaptor

Adaptor OD

Fit (interference)

(i) 23076559-1

0.9000 to 0.9008 inch

0.0000 to -0.0013 inch.

(ii) 23076559-2

0.9020 to 0.9028 inch

0.0000 to -0.0013 inch.

(iii) 23076559-3

0.9040 to 0.9048 inch

0.0000 to -0.0013 inch.

(j) The mating surfaces of the impeller and coupling must not have any fretting. Do not install a -1 coupling into a used impeller.

Note: FAA AD 2004-26-09 Amdt 39-13921 refers.

\n```\n\n| Compliance: | 1. Alcor Compressor Adaptor Couplings(a) For couplings with 600 or more operating hours-since-new as of the effective date of this Directive, or the operating hours are unknown and cannot be determined, remove couplings from service within 50 additional operating hours after the effective date of this Directive or by 15 June 2005, whichever occurs later.(b) For couplings with fewer than 600 operating hours-since-new on the effective date of this Directive, remove couplings from service before exceeding 650 operating hours-since-new or by 15 June 2005, whichever occurs later.2. EXTEX and SAP Compressor Adaptor Couplings(a) For couplings with 600 or more operating hours-since-new as of the effective date of this Directive, or the operating hours are unknown and cannot be determined, remove couplings from service within 100 additional operating hours after the effective date of this Directive or by 15 June 2005, whichever occurs later.(b) For couplings with fewer than 600 operating hours-since-new on the effective date of this Directive, remove couplings from service within 150 additional operating hours after the effective date of this Directive or by 15 June 2005, whichever occurs later.3. RRC Compressor Adaptor CouplingsAt the next time the compressor rotor is disassembled for any reason, but not later than 1 March 2017, subject to the following conditions:(a) The engine has been operating with acceptable power assurance checks.(b) The engine, gearbox, or turbine has not experienced any recent chip lights or metal in oil events.(c) All mandatory bulletins issued by RRC have been accomplished within the designated compliance requirements.(d) That the maintenance records indicate proper engine maintenance has been performed per the applicable Operations and Maintenance Manual.(e) Compliance with Commercial Engine Bulletin (CEB)-A-1392 latest revision is still applicable next time the compressor is due for repair or overhaul. Compliance Code 4. |\n| ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n| | (f) The parts related to the CEB or AD must have been manufactured by Rolls-Royce. If they are not Rolls-Royce manufactured parts, RRC Compressor Adaptor Couplings must be replaced by the compliance date of revision 2 of this AD (1 March 2012).4. Installation Requirements for Compressor Adaptor CouplingsFrom the effective date of this Directive.DefinitionFor the purposes of this Directive, next access is defined as when the compressor module is separated from the engine and disassembled for any reason. |\n| ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| | This Amendment becomes effective on 8 March 2012. |\n| Background: | This AD results from nine reports of engine shutdown caused by compressor adaptor coupling failure.Amendment 3 compliance date extended for RRC compressor adapter couplings, subject to the stated conditions.Amendment 2 corrected a typographical error in Table 2 of the Applicability and removes the discrepancy in the compliance times for EXTEX and SAP couplings.Amendment 1 amended the compliance period.Amendment 1 of this Directive became effective on 22 March 2005.The original issue of this Directive became effective on 17 March 2005. |\n\n![](image.001.png)\n\nMike Higgins \nDelegate of the Civil Aviation Safety Authority\n\n8 March 2012","sortOrder":0},{"sectionNumber":"AD/AL 250/86 Amdt 3","sectionType":"part","heading":"AD/AL 250/86 Amdt 3","content":"## AD/AL 250/86 Amdt 3","sortOrder":1},{"sectionNumber":"Compressor Adaptor Coupling","sectionType":"part","heading":"Compressor Adaptor Coupling","content":"## Compressor Adaptor Coupling","sortOrder":2},{"sectionNumber":"5/2012","sectionType":"part","heading":"5/2012","content":"## 5/2012","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":7,"scope_assessment":{"changed":true,"description":"Amendments adjusted compliance timing and conditions rather than expanding the listed parts or aircraft. Amendment 3 extended the RRC compliance date (to 1 March 2017) subject to several operational and maintenance conditions; earlier amendments corrected a typographical error in the applicability table and harmonised compliance times for EXTEX and SAP couplings and modified compliance periods."},"complexity_factors":["Multiple affected part numbers across four manufacturers (Alcor, EXTEX, RRC, SAP) increasing tracking and inventory complexity.","Staged and differing compliance deadlines tied to operating hours-since-new and fixed calendar dates.","Technical installation and machining requirements with precise tolerances (0.0000 to -0.0013 inch) and prohibitions (no plating; no fretting).","Conditional deferral for RRC couplings subject to multiple maintenance and operational attestations (chip lights, metal-in-oil history, mandatory bulletins, maintenance records, CEB compliance).","Cross-references to manufacturer Commercial Engine Bulletin (CEB)-A-1392 and FAA AD 2004-26-09, creating dependency on external documents.","Inspection mandate (fluorescent penetrant) and prohibition on installing certain couplings into used impellers, adding shop-level procedural steps and possible replacement of impellers.","Amendment history altering deadlines and correcting applicability tables, requiring attention to which revision applies."],"plain_english_summary":"This Directive orders removal from service of specific compressor adaptor couplings fitted to Rolls‑Royce (Allison) 250‑series turboprop/turboshaft engines on listed helicopters and aeroplanes, and sets required machining, inspection and replacement procedures (including exact fits, heating and inspection methods). It affects aircraft owners/operators and maintenance providers, who must pay for parts, machining, inspections and downtime to meet staged removal deadlines or follow conditional deferral rules for certain Rolls‑Royce parts."},"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"},"kimi_summary":{"content_quality":"ok","complexity_score":6,"scope_assessment":{"changed":true,"description":"The original directive (March 2005) was a straightforward safety order to remove faulty couplings. Amendment 3 (March 2012) significantly expanded the scope by introducing a complex conditional compliance scheme for Rolls-Royce manufactured couplings, allowing extended deadlines until 2017 if five specific operational and maintenance conditions are met. This transformed a simple 'remove by date X' directive into a nuanced, risk-based maintenance program with alternative compliance paths."},"complexity_factors":["Multiple manufacturer-specific compliance tracks (Alcor, EXTEX/SAP, RRC) with different deadlines and hour thresholds","Nested conditional logic for RRC couplings requiring five separate pre-conditions to qualify for extended compliance","Technical installation requirements including precise machining tolerances (0.0000 to -0.0013 inch interference fit) and prohibited practices (no plating, no fretting allowed)","Cross-reference to FAA AD 2004-26-09 and Commercial Engine Bulletin CEB-A-1392","Definition of 'next access' required for interpretation of compliance timing","Amendment history (Amendments 1, 2, 3) with varying effective dates and retroactive compliance deadlines (some dating back to 2005)"],"plain_english_summary":"This CASA Airworthiness Directive mandates removal and replacement of certain faulty compressor adaptor couplings on Rolls‑Royce 250‑series engines used in several helicopters and one fixed‑wing type. It targets couplings from multiple suppliers that have caused in‑service engine shutdowns. Compliance prevents further inflight engine failures by ensuring defective parts are replaced with approved replacements."}},"importantCases":[],"_links":{"self":"/api/acts/ad-al-250-86-amdt-3-compressor-adaptor-coupling","history":"/api/acts/ad-al-250-86-amdt-3-compressor-adaptor-coupling/history","analysis":"/api/acts/ad-al-250-86-amdt-3-compressor-adaptor-coupling/analysis","conflicts":"/api/acts/ad-al-250-86-amdt-3-compressor-adaptor-coupling/conflicts","importantCases":"/api/acts/ad-al-250-86-amdt-3-compressor-adaptor-coupling/important-cases","documents":"/api/acts/ad-al-250-86-amdt-3-compressor-adaptor-coupling/documents"}}