{"id":"F2006B11012","name":"AD/JT9D/19 Amdt 2 - Surge Margin Improvements","slug":"ad-jt9d-19-amdt-2-surge-margin-improvements","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56612,"registerId":"commonwealth-F2006B11012-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/JT9D/19 Amdt 2 - Surge Margin Improvements","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nPratt and Whitney Turbine Engines \\- JT9D Series\n\nAD/JT9D/19\n\nAmdt 2\n\n  \nSurge Margin Improvements 3/93\n\nApplicability: JT9D-7R4D, E series engines installed in Boeing B767 aircraft.\n\nRequirement: Action in accordance with FAA Airworthiness Directive 90-14-08, paragraphs (a), (b), (c), (d), (e), (f), (g), (h) and (i).\n\nFor the purpose of this Directive, compliance with the requirements of PWA SB JT9D-7R4-75-101 is deemed to be an alternative method of compliance with the requirements of FAA AD 90-14-08, paragraph (d), (2).\n\nCompliance: As detailed in the requirement document, with an effective date of 4 March 1993.\n\nBackground: This Directive has been amended to reflect the release of an additional procedure which, if incorporated, will improve the JT9D-7R4 surge margin.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a narrow, technical airworthiness directive focused on a specific engine modification. The amendment history mentioned ('amended to reflect the release of an additional procedure') suggests incremental refinement rather than scope expansion. The document remains tightly focused on its original purpose: improving surge margins on specific JT9D engine variants."},"complexity_factors":["Very short document (under 300 words)","Only 1 defined term implicitly referenced (the alternative compliance method)","No nested conditional logic — simple directive to follow external document","Single cross-reference to FAA directive and one service bulletin","Clear applicability statement limiting scope to specific engine models and aircraft type","No exceptions or exceptions-to-exceptions"],"plain_english_summary":"This is a **safety order for aircraft engines**. It applies to specific Pratt & Whitney JT9D engines (the -7R4D and -7R4E models) installed in Boeing 767 aircraft.\n\n**What it does:**\n- Requires airlines and aircraft operators to follow a specific set of maintenance procedures laid out in an American aviation safety directive (FAA AD 90-14-08)\n- These procedures are designed to **improve \"surge margin\"** — essentially making the engines less likely to stall or surge (a dangerous condition where airflow through the engine becomes unstable)\n- Offers an alternative way to comply: operators can follow a Pratt & Whitney service bulletin (SB JT9D-7R4-75-101) instead of one specific part of the American directive\n\n**Who it affects:**\n- Airlines and operators flying Boeing 767s with these specific engine models\n- Maintenance organisations servicing these engines\n\n**Why it matters:**\nEngine surges can cause power loss, engine damage, or even in-flight shutdowns. This directive mandates upgrades to prevent these dangerous situations, improving flight safety."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"The AD has been amended to reflect the release of an additional procedure that, if incorporated, will improve the JT9D-7R4 surge margin (Background). Practically, the amendment expands the set of acceptable technical actions by recognising an additional procedure (and explicitly accepting a Pratt & Whitney service bulletin as an alternative method for FAA AD paragraph (d)(2)). This changes the options available to operators for achieving compliance compared with the original wording that relied solely on the FAA AD requirements. (Requirement; Background)"},"complexity_factors":["Narrow applicability to specific engine models (JT9D-7R4D and -7R4E) on a specific airframe (Boeing B767). (Applicability)","Direct cross-reference to an external regulatory instrument (FAA AD 90-14-08) with multiple quoted paragraphs (a)–(i), which requires users to consult another document to know the exact steps. (Requirement)","Acceptance of a manufacturer service bulletin (PWA SB JT9D-7R4-75-101) as an alternative method for one subparagraph (d)(2), introducing an additional external technical source. (Requirement)","Technical subject matter (surge margin improvement) that implicates maintenance procedures and engineering judgement but is not explained in the directive itself. (Background)","Effective date and amendment history are stated but the AD delegates technical detail to the referenced documents, concentrating substantive complexity in those external texts. (Compliance; Background)"],"plain_english_summary":"### What this instrument does\n\nThis is an Airworthiness Directive (AD) issued by the Civil Aviation Safety Authority that requires operators of certain Pratt & Whitney JT9D turbine engines to carry out specified actions to reduce the risk of engine surge by improving the engine's surge margin. The directive tells operators to act in accordance with an existing FAA Airworthiness Directive (FAA AD 90-14-08), specifically paragraphs (a) through (i). (See: \"Requirement\".)\n\n### Who it affects\n\n- Airlines or aircraft operators that have Pratt & Whitney JT9D-7R4D and JT9D-7R4E series engines installed in Boeing B767 aircraft. (See: \"Applicability\".)\n\n### How it works, mechanically\n\n- The directive says: do what FAA AD 90-14-08 paragraphs (a)–(i) require. (See: \"Requirement\".)\n- For one particular subrequirement (FAA AD 90-14-08 paragraph (d)(2)), the directive accepts compliance by using a Pratt & Whitney service bulletin (PWA SB JT9D-7R4-75-101) as an alternative method. (See: \"Requirement\".)\n- The directive took effect on 4 March 1993 and must be complied with as detailed in the referenced requirement document. (See: \"Compliance\".)\n\n### Why it matters (official purpose and practical consequences)\n\n- The stated purpose in the instrument is to reflect the release of an additional procedure that, if incorporated, will improve the JT9D-7R4 surge margin. That is the explicit reason given for the amendment. (See: \"Background\".)\n\n- Who pays: the operators of the affected engines/aircraft must perform whatever actions the referenced FAA AD or the accepted Pratt & Whitney service bulletin require. The directive itself does not state costs; it simply mandates compliance. (See: \"Requirement\", \"Compliance\".)\n\n- Who decides: the Civil Aviation Safety Authority issued the directive and prescribes compliance by reference to the FAA AD; Pratt & Whitney’s service bulletin is accepted as an alternative method for one sub-item. Where the directive refers to the FAA AD or the service bulletin, those external documents determine the technical steps required. (See: \"Requirement\".)\n\n- Behaviour changes: operators must incorporate the procedures from the FAA AD (or the accepted service bulletin for the specified sub-item) into their maintenance/repair activity for the listed engine models. The amendment adds an additional procedure option to improve surge margin. (See: \"Requirement\", \"Background\".)\n\n- Compliance burden and discretion: the directive is prescriptive and requires operators to follow an external regulatory document (FAA AD) or a manufacturer service bulletin for one subpoint. The acceptance of a manufacturer service bulletin as an alternative method reduces choice for that particular sub-item to either meet the FAA AD steps or adopt the specified service bulletin steps. The AD does not state exemptions or cost relief. (See: \"Requirement\".)\n\n### Implementation risks and trade-offs to watch for\n\n- The directive relies on external technical documents (FAA AD 90-14-08 and PWA SB JT9D-7R4-75-101). Operators must obtain and interpret those documents accurately to demonstrate compliance. (See: \"Requirement\".)\n- The amendment adds an additional procedure (stated to improve surge margin). Whether operators adopt that procedure or another permitted method will depend on the technical fit and cost to the operator; those practical considerations are not specified in the directive itself. (See: \"Background\".)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-jt9d-19-amdt-2-surge-margin-improvements","history":"/api/acts/ad-jt9d-19-amdt-2-surge-margin-improvements/history","analysis":"/api/acts/ad-jt9d-19-amdt-2-surge-margin-improvements/analysis","conflicts":"/api/acts/ad-jt9d-19-amdt-2-surge-margin-improvements/conflicts","importantCases":"/api/acts/ad-jt9d-19-amdt-2-surge-margin-improvements/important-cases","documents":"/api/acts/ad-jt9d-19-amdt-2-surge-margin-improvements/documents"}}