{"id":"F2006L02254","name":"AD/AL501/7 - Third Stage Turbine Blade Failures","slug":"ad-al501-7-third-stage-turbine-blade-failures","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":117580,"registerId":"commonwealth-F2006L02254-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Rolls Royce (Allison) Turbine Engines - ","sectionType":"division","heading":"Rolls Royce (Allison) Turbine Engines - AL501 Series","content":"### Rolls Royce (Allison) Turbine Engines - AL501 Series\n\n| AD/AL501/7 | Third Stage Turbine Blade Failures | 8/2006 |\n| ---------- | ---------------------------------- | ------ |\n\n| Applicability: | Allison Models 501-D13, 501-D13A, 501-D13D and 501-D13E Engines not modified in accordance with Allison Commercial Engine Bulletin No. 72-77.Note 1: Allison Commercial Engine Bulletin requires the installation of third stage turbine blades P/N 6794773 identified by a stripe of heat and corrosion resistant aluminium polytherm paint 1/2-inch wide and 4 inches long around contour of the inlet casing clockwise.                                   |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| Requirement:   | Action in accordance with FAA AD 59-18-01 for 501-D13 and 501-D13A engines.Action in accordance with FAA AD 60-07-01 for 501-D13D and 501-D13E engines.Note 2: FAA AD 59-18-01 and 60-07-01 Amdt 124 refer.                                                                                                                                                                                                                                                  |\n| Compliance:    | As detailed in FAA AD 59-18-01 or AD 60-07-01, as applicable, with a revised effective date of 3 August 2006.                                                                                                                                                                                                                                                                                                                                                |\n|                | This Airworthiness Directive becomes effective on 3 August 2006.                                                                                                                                                                                                                                                                                                                                                                                             |\n| Background:    | Third stage turbine blade failures have occurred due to a resonance condition at low speed ground idle. All of these failures to date have resulted in visible damage to fourth stage blades as well as fourth stage vanes. In one case continued operation of an engine with a failed blade resulted in failure of the turbine inlet case-vane case split line bolts. This AD requires limits be placed on engine ground operations for unmodified engines. |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n21 June 2006","sortOrder":0},{"sectionNumber":"AD/AL501/7","sectionType":"part","heading":"AD/AL501/7","content":"## AD/AL501/7","sortOrder":1},{"sectionNumber":"Third Stage Turbine Blade Failures","sectionType":"part","heading":"Third Stage Turbine Blade Failures","content":"## Third Stage Turbine Blade Failures","sortOrder":2},{"sectionNumber":"8/2006","sectionType":"part","heading":"8/2006","content":"## 8/2006","sortOrder":3}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a standard Airworthiness Directive with narrow, targeted scope addressing a specific mechanical failure mode in specific engine models. It has not expanded beyond its original safety purpose."},"complexity_factors":["Short, single-purpose directive (approximately 250 words of substantive content)","Only 4 specific engine models affected, clearly identified","Relies on incorporation by reference to two external FAA documents rather than restating requirements","Simple conditional logic: applies only to engines 'not modified' per specific bulletin","Single compliance date with no phased implementation","No nested definitions or interpretation section","Background explanation is straightforward and technical but accessible"],"plain_english_summary":"This mandatory CASA Airworthiness Directive requires operators of Allison 501‑D13 series engines that have not been modified per the factory bulletin to follow existing FAA safety orders limiting ground operating procedures. It addresses a known low‑speed vibration that can cause third‑stage turbine blade failure and collateral damage.\n\nEffective 3 August 2006, it adopts the FAA ADs to prevent catastrophic engine failure, protecting aircraft, crew, and passengers."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD does not expand scope beyond the originally targeted engines and conditions: it remains confined to specified Allison 501‑D13 series engines that are not modified per the stated commercial engine bulletin and requires compliance with the referenced FAA ADs. The instrument revises the effective date but does not broaden the population or types of measures required."},"complexity_factors":["Cross-reference to external FAA ADs (FAA AD 59‑18‑01 and 60‑07‑01) creates dependence on other instruments and their amendments","Conditional applicability limited to engines not modified per Allison Commercial Engine Bulletin No. 72‑77","Technical requirement to install/identify a specific part (third‑stage blade P/N 6794773) and its marking","Operational constraint rather than a single maintenance action (limits on ground operations introduce procedural changes)","Effective date revision and need to track applicable amendment history (administrative compliance burden)","Safety consequence linkage (failures can damage later stages and hardware), increasing urgency of compliance"],"plain_english_summary":"This Airworthiness Directive requires operators of Allison 501‑D13, 501‑D13A, 501‑D13D and 501‑D13E engines that have not been modified per Allison Commercial Engine Bulletin No. 72‑77 to comply with the relevant FAA directives (FAA AD 59‑18‑01 or 60‑07‑01) and takes effect 3 August 2006. It imposes limits on engine ground operations for affected unmodified engines and requires the installation/identification of replacement third‑stage turbine blades (P/N 6794773) where the bulletin applies. Operators bear compliance costs; CASA (through its delegate) enforces the requirement."},"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-al501-7-third-stage-turbine-blade-failures","history":"/api/acts/ad-al501-7-third-stage-turbine-blade-failures/history","analysis":"/api/acts/ad-al501-7-third-stage-turbine-blade-failures/analysis","conflicts":"/api/acts/ad-al501-7-third-stage-turbine-blade-failures/conflicts","importantCases":"/api/acts/ad-al501-7-third-stage-turbine-blade-failures/important-cases","documents":"/api/acts/ad-al501-7-third-stage-turbine-blade-failures/documents"}}