{"id":"F2009L03849","name":"AD/JT8D/43 - Front Compressor Hub","slug":"ad-jt8d-43-front-compressor-hub","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":81094,"registerId":"commonwealth-F2009L03849-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Pratt and Whitney Turbine Engines - JT8D","sectionType":"division","heading":"Pratt and Whitney Turbine Engines - JT8D Series","content":"### Pratt and Whitney Turbine Engines - JT8D Series\n\n| AD/JT8D/43 | Front Compressor Hub | 12/2009 |\n| ---------- | -------------------- | ------- |\n\n| Applicability: | Pratt & Whitney Aircraft JT8D-1, -1A, -7, and -7A turbofan engines using Front Compressor Front Hub Part Nos. 504101 and 515201.Note 1: Pratt & Whitney Aircraft Alert Service Bulletin (ASB) No. 2944 RevisionNo. 13 dated 22 October 2008 lists the engine and hub serial numbers affected by this AD.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |\n| -------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. To preclude failure of the front compressor front hub as a result of (a) possible surface defects in the blade slots or (b) possible loss of effectiveness of shotpeening in the blade slots accomplish the following on hubs listed in tables I and II of the above ASB.a. Visually inspect the rear face and overhung shelf of the hub rim for cracks emanating out of the base of the acute corner of the dovetail slots, orb. Inspect with an eddy current probe the rear overhung shelf of the hub rim for cracks emanating out of the base of the acute corner of the dovetail slots, orc. Remove all first stage compressor blades and inspect the blade slots of the hub with an eddy current probe for cracks emanating out of the base of the acute corner of the dovetail slots.d. If any crack is found during any of the foregoing inspections replace hub.It is permissible to use any of the three inspection procedures at the end of the preceding inspection period.2. To preclude failure of the front compressor front hub from lack of shotpeening, accomplish the following on hubs listed in table III of the above ASB.a. Visually inspect to determine whether the rim area of the hub has been shotpeened.b. If the inspection confirms that the hub has not been shotpeened then the hub is to be inspected in accordance with Requirements 1.a. through d. of this AD. |\n\n|             | Later revisions of the above SB, approved by the United States Federal Aviation Administration (FAA) as an Alternate Method of Compliance (AMOC) to FAA AD 71-07-01 are considered acceptable for compliance with the equivalent Requirements of this AD.Note 2: FAA AD 71-07-01 Amdt. 39-1279 dated 7 September 1971 refers.                                                                                                                                                                                                                                                                                                                                                                                                                                         |\n| ----------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Compliance: | Compliance required as indicated on all front compressor front hubs that have accumulated 6000 cycles or more in service.For Requirement 1.a. - Within the next 150 cycles in service and every 150 cycles in service thereafter until the hub is removed.For Requirement 1.b. - Within the next 150 cycles in service, unless already accomplished and every 400 cycles in service thereafter until the hub is removed.For Requirement 1.c. - Within the next 150 cycles in service, unless already accomplished and every 1500 cycles in service thereafter.For Requirement 1.d. - Before further flight.For Requirement 2.a. - Within the next 150 cycles in service.For Requirement 2.b. - At the intervals defined in Requirements 1.a. through 1.d. of this AD. |\n|             | This Airworthiness Directive becomes effective on 19 November 2009.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |\n| Background: | Surface defects found on certain front compressor hubs may lead to failure of the hub and subsequent damage or loss of control of the aeroplane.This AD is issued following a review of airworthiness directives preceding changes to CASR 39. This AD was not previously issued however a review of the data indicates that the FAA AD referenced is still current. In addition the manufacturer recently issued an updated ASB referencing the FAA AD.                                                                                                                                                                                                                                                                                                              |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n28 September 2009","sortOrder":0},{"sectionNumber":"AD/JT8D/43","sectionType":"part","heading":"AD/JT8D/43","content":"## AD/JT8D/43","sortOrder":1},{"sectionNumber":"Front Compressor Hub","sectionType":"part","heading":"Front Compressor Hub","content":"## Front Compressor Hub","sortOrder":2},{"sectionNumber":"12/2009","sectionType":"part","heading":"12/2009","content":"## 12/2009","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":6,"scope_assessment":{"changed":false,"description":"This AD continues the original safety-focused scope — preventing front compressor hub failure due to cracks or inadequate shotpeening — and closely follows the referenced FAA AD and the manufacturer’s ASB lists. It does not broaden the subject matter beyond those hubs and serial numbers identified by the ASB, and it expressly accepts later ASB revisions only if approved by the FAA as an AMOC. Therefore the scope has not been materially expanded beyond the original airworthiness intent: it remains a targeted inspection-and-replace mandate for affected JT8D hubs."},"complexity_factors":["Multiple inspection options (three distinct methods under Requirement 1) allowing operator choice","Different repeat intervals tied to inspection method (150, 400 and 1500 cycles) creating conditional scheduling rules","Applicability limited by part numbers and specific serial numbers listed in external ASB tables I, II and III (cross-reference dependency)","Cross-reference to FAA AD 71-07-01 and acceptance of later ASB revisions approved as FAA AMOCs (external regulatory cross-references)","Conditional two-stage requirement for hubs potentially lacking shotpeening (Requirement 2 triggers Requirement 1 if unshotpeened)","Technical inspection methods requiring specific tools and skills (eddy-current testing, blade removal) which affect implementation complexity","Compliance threshold condition (applies only to hubs with 6000 cycles or more) adds an eligibility gate","Immediate mandatory action if cracks are found (replace before further flight), creating urgent operational constraints"],"plain_english_summary":"**What this instrument does (mechanically):**\n\n- This is an Airworthiness Directive (AD) that requires inspections and, where necessary, replacement of certain Pratt & Whitney JT8D front compressor hubs (Part Nos. 504101 and 515201). It targets hubs and engine serial numbers listed in the manufacturer’s Alert Service Bulletin (ASB) tables I, II and III.\n\n- It sets out three alternative inspection methods to detect cracks in the dovetail (blade) slots of the hub: a visual inspection of the rear face and overhung shelf (Requirement 1.a), an eddy-current inspection of the overhung shelf (Requirement 1.b), or removing first-stage compressor blades and performing an eddy-current inspection of the blade slots (Requirement 1.c). If any crack is found by any method, the hub must be replaced before the next flight (Requirement 1.d).\n\n- For hubs that may not have been shotpeened (a surface-hardening process that helps prevent cracking), the AD requires a visual check to confirm whether shotpeening was done (Requirement 2.a). If shotpeening is absent, the hub must be inspected using the crack-detection procedures listed above (Requirement 2.b).\n\n- The AD specifies when the inspections must start and how often they must be repeated, depending on the inspection method used: generally starting within the next 150 cycles in service for most checks, with repeat intervals of 150, 400 or 1500 cycles depending on the chosen method (see the Compliance section).\n\n**Who it affects:**\n\n- Operators and maintainers of aircraft powered by Pratt & Whitney JT8D-1, -1A, -7 and -7A engines that use the specified front compressor hub part numbers and serial numbers listed in the ASB. Airline maintenance organisations, independent overhaul shops and aircraft owners who operate affected engines must comply.\n\n**Why it matters (safety and operational mechanics):**\n\n- The stated safety risk is that surface defects or ineffective shotpeening in the hub dovetail slots can lead to hub crack initiation and propagation. Hub fracture could cause engine damage or loss of control of the aircraft. The AD’s mechanical effect is to detect such cracks early and remove cracked hubs from service.\n\n**Key operational effects and duties (who pays, who decides, what behaviour changes):**\n\n- Operators pay for the inspections, any blade removals, eddy-current testing, and hub replacements. Maintenance organisations will schedule inspections, choose which permitted inspection method to use, and carry out repairs or replacements when cracks are found.\n\n- Decision-making is constrained: the AD allows choice among the three inspection procedures (see Requirement 1), but imposes the specified start times and repeat intervals. Later ASB revisions approved by the FAA as an Alternate Method of Compliance (AMOC) are acceptable (the AD cross-references the ASB and FAA AD). \n\n**Costs, incentives and trade-offs:**\n\n- Direct costs: regular inspection labour, potential blade removal and reinstallation time, eddy-current equipment use, and replacement hubs where cracks are detected.\n\n- Incentives: because finding a crack requires replacement before next flight, operators are incentivised to perform inspections on schedule and possibly adopt the inspection method that minimises downtime or cost while meeting the AD’s interval requirements.\n\n- Trade-offs: a less invasive but more-frequent inspection (visual or overhung-shelf eddy-current) may increase recurring maintenance time but avoid the larger downtime associated with blade removal; conversely, the more intrusive inspections (blade removal + eddy-current) have longer repeat intervals but higher immediate labour costs.\n\n**Implementation risks and compliance burdens:**\n\n- Availability of qualified personnel and eddy-current inspection capability affects compliance. Removing first-stage blades for inspection increases shop time and aircraft downtime compared with on-wing inspections.\n\n- The AD relies on operators checking ASB tables for affected serial numbers; misidentification of parts or missed updates to ASB/AMOC approvals could cause non-compliance.\n\n**Legal and procedural cross-references:**\n\n- The AD accepts later revisions of the manufacturer’s Service Bulletin if they are approved by the FAA as an AMOC to the referenced FAA AD (FAA AD 71-07-01). The ASB lists the precise hub and engine serial numbers to which the AD applies.\n\n**Where to look in the document for specific actions:**\n\n- Which hubs are affected: ASB tables I, II and III (Applicability section).\n- Crack-detection options and replacement requirement: Requirement 1 (subparagraphs a–d).\n- Shotpeening check and follow-up: Requirement 2 (subparagraphs a–b).\n- Compliance timing and cycle intervals: Compliance section (starts-with 6000 cycles threshold and the 150/400/1500-cycle frequencies).\n\nOverall, the AD operates by defining a set of permitted inspection techniques, mandating their timing, and requiring replacement of cracked hubs; it places the cost and operational burden of these inspections and replacements on the engine operators and maintenance providers while allowing some flexibility in the inspection method chosen so long as the required intervals and corrective actions are followed."},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing specific safety defects in particular Pratt & Whitney engine models. The document explicitly states it was issued following a regulatory review (CASR 39 changes) but confirms the underlying safety issue and FAA directive remain current. No scope creep is evident; it remains targeted at the specific compressor hub defect."},"complexity_factors":["Multiple inspection pathways (1.a, 1.b, 1.c) with different compliance intervals (150, 400, and 1,500 cycles)","Cross-reference to external manufacturer document (Pratt & Whitney Alert Service Bulletin No. 2944 Rev 13) for serial number lists","Nested conditional logic: Requirement 2.b triggers Requirements 1.a through 1.d if shotpeening is absent","Reference to foreign regulatory equivalence (FAA AD 71-07-01) and AMOC (Alternate Method of Compliance) provisions","Technical aviation terminology requiring specialized knowledge (eddy current, shotpeening, dovetail slots, cycles in service)","Multiple tables referenced but not reproduced in the directive itself (Tables I, II, and III)"],"plain_english_summary":"This AD mandates recurring inspections of the Pratt & Whitney JT8D-1/1A/‑7/‑7A front compressor hub—visual, eddy‑current checks, and verification of required shotpeening—and immediate replacement if cracks are found. It affects operators of older Boeing 727/737 and McDonnell Douglas DC‑9/MD‑80 aircraft using these engines. It’s safety‑critical to prevent catastrophic hub failure and subsequent engine or airframe damage."}},"importantCases":[],"_links":{"self":"/api/acts/ad-jt8d-43-front-compressor-hub","history":"/api/acts/ad-jt8d-43-front-compressor-hub/history","analysis":"/api/acts/ad-jt8d-43-front-compressor-hub/analysis","conflicts":"/api/acts/ad-jt8d-43-front-compressor-hub/conflicts","importantCases":"/api/acts/ad-jt8d-43-front-compressor-hub/important-cases","documents":"/api/acts/ad-jt8d-43-front-compressor-hub/documents"}}