{"id":"F2007L04028","name":"AD/ATR 42/21 - Thermal Acoustic Insulation Blankets on Frame 24","slug":"ad-atr-42-21-thermal-acoustic-insulation-blankets-on-frame-24","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":160817,"registerId":"commonwealth-F2007L04028-current","compilationNumber":null,"startDate":"2026-04-04","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Avions de Transport Regional ATR 42 Seri","sectionType":"division","heading":"Avions de Transport Regional ATR 42 Series Aeroplanes","content":"### Avions de Transport Regional ATR 42 Series Aeroplanes\n\n| AD/ATR 42/21 | Thermal Acoustic Insulation Blanketson Frame 24 | 12/2007 DM |\n| ------------ | ----------------------------------------------- | ---------- |\n\n| Applicability: | ATR 42-400 and 42-500 models, all serial numbers, except aircraft modified with ATR modification No. 05117 or 05322 or 05791 or Service Bulletin (SB) ATR42-25-0134.                                                                                                                                                                                                                                                     |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| Requirement:   | Unless previously accomplished, remove the metallised PET insulation blankets installed on the left and the right sides of the aircraft over frame 24 between stringers 5 and 14, as detailed in the accomplishment instructions of SB ATR 42-25-0155.Note: EASA AD 2007-0106-E, effective 20 April 2007 refers.                                                                                                         |\n| Compliance:    | Accomplish within 25 flight hours after the effective date.                                                                                                                                                                                                                                                                                                                                                              |\n|                | This Airworthiness Directive becomes effective on 25 October 2007.                                                                                                                                                                                                                                                                                                                                                       |\n| Background:    | On two ATR 42-500 aircraft, some burnt spots were found on insulation blankets installed over frame 24. Investigations concluded that due to the proximity of the hot bleed air duct, installation of thermal-acoustical insulation blankets having a metallised PolyEthylene Terephtalate (PET) covering (Mylar), may represent a fire risk. This AD requires the removal of metallised PET blankets covering frame 24. |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n5 October 2007","sortOrder":0},{"sectionNumber":"AD/ATR 42/21","sectionType":"part","heading":"AD/ATR 42/21","content":"## AD/ATR 42/21","sortOrder":1},{"sectionNumber":"Thermal Acoustic Insulation Blanketson F","sectionType":"part","heading":"Thermal Acoustic Insulation Blanketson Frame 24","content":"## Thermal Acoustic Insulation Blankets  \non Frame 24","sortOrder":2},{"sectionNumber":"12/2007 DM","sectionType":"part","heading":"12/2007 DM","content":"## 12/2007 DM","sortOrder":3}],"analysis":{"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"},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The AD's scope is consistent with its stated intent: to remove metallised PET blankets over frame 24 after burnt spots were found. It targets specified ATR 42 submodels and explicitly excludes aircraft already modified by listed modifications or the listed service bulletin, without expanding or narrowing beyond those technical boundaries (Applicability; Requirement; Background)."},"complexity_factors":["Narrow applicability: limited to ATR 42-400 and 42-500 models, with explicit exemptions for aircraft modified by ATR mod No. 05117, 05322, 05791 or SB ATR42-25-0134 (Applicability).","Single, clearly specified corrective action: removal of metallised PET insulation blankets on left and right sides over frame 24 between stringers 5 and 14, per SB ATR 42-25-0155 (Requirement).","Short, explicit compliance window: action to be completed within 25 flight hours after the effective date (Compliance).","Dependence on external technical material: accomplishment instructions and validation reference a specific service bulletin and an EASA AD (Requirement / Note).","Safety basis drawn from two observed incidents (burnt spots) and identified proximity to the hot bleed air duct, which frames the risk justification (Background).","Low regulatory discretion: effective date and immediate compliance obligation set by CASA (Effective date / Delegate signature)."],"plain_english_summary":"This Airworthiness Directive requires operators of ATR 42-400 and 42-500 aeroplanes to remove metallised PET (Mylar) thermal-acoustic insulation blankets from both sides over frame 24 (between stringers 5 and 14), unless the aircraft already has certain ATR modifications or a specific service bulletin. CASA set a compliance deadline of 25 flight hours from the effective date (25 October 2007); the AD follows discovery of burnt spots and identifies a potential fire risk from proximity to the hot bleed air duct."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a targeted safety directive addressing a specific fire risk identified on particular aircraft models. The scope remains precisely limited to the insulation blanket issue on frame 24 of ATR 42-400/500 aircraft, with no expansion beyond the original safety concern."},"complexity_factors":["Single, specific technical requirement (remove specific insulation blankets)","Limited applicability (only two ATR 42 sub-models)","Clear exemption list (four specific modifications exempt aircraft)","Simple compliance timeline (25 flight hours)","No nested conditions or cross-references to other legislation","Short document (approximately 200 words of substantive content)","Only one defined technical term (metallised PET/Mylar explained in background)"],"plain_english_summary":"This AD orders operators of ATR 42-400 and -500 aircraft to remove metallised PET (Mylar) insulation blankets from frame 24 because they sit too close to hot bleed-air ducts and have caused burn damage, posing a fire/smoulder risk. Maintenance must comply within 25 flight hours (effective 25 Oct 2007) following Service Bulletin ATR 42-25-0155; aircraft already modified per specified ATR service bulletins are exempt."}},"importantCases":[],"_links":{"self":"/api/acts/ad-atr-42-21-thermal-acoustic-insulation-blankets-on-frame-24","history":"/api/acts/ad-atr-42-21-thermal-acoustic-insulation-blankets-on-frame-24/history","analysis":"/api/acts/ad-atr-42-21-thermal-acoustic-insulation-blankets-on-frame-24/analysis","conflicts":"/api/acts/ad-atr-42-21-thermal-acoustic-insulation-blankets-on-frame-24/conflicts","importantCases":"/api/acts/ad-atr-42-21-thermal-acoustic-insulation-blankets-on-frame-24/important-cases","documents":"/api/acts/ad-atr-42-21-thermal-acoustic-insulation-blankets-on-frame-24/documents"}}