Aircraft Certification Service (AIR) Draft Advisory Circulars (ACs) Open for Comment
| Document Title: | AC 33-13 Sample Size Considerations for Comparative Test and Analysis for Turbine Aircraft Engine and Auxiliary Power Unit (APU), Parts Manufacturer Approval (PMA), and Third-Party Repair Parts |
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| Summary: | This advisory circular (AC) describes two approaches to define minimum sample sizes of products and articles for turbine aircraft engines and auxiliary power units (APUs) that applicants for a parts manufacturer approval (PMA) may use to show compliance with the test reports and computations requirements of Title 14, Code of Federal Regulations (14 CFR) § 21.303(a)(4), using the comparative test and analysis approach to support showing the engine or APU comply with the applicable airworthiness requirements of 14 CFR Part 33 and Technical Standard Order (TSO) C77. |
| Reference: | 14 CFR 21.303(a)(4) 14 CFR 43.13 |
| Documents for Download: | Draft Document Comment Matrix |
| Comments Due: | September 12, 2025 |
| How to Comment: | Email comments to 9-AVS-TechWriters@faa.gov |
| Document Title: | AC 33.70-5 Damage Tolerance of Axial Blade Slot Features in High-Energy Turbine Engine Rotors |
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| Summary: | This advisory circular (AC) provides definitions, guidance, and acceptable methods, but not the only methods, that may be used to demonstrate compliance with requirements in title 14 of the Code of Federal Regulations (14 CFR) 33.70 related to the integrity of engine life-limited parts. Section 33.70 contains requirements applicable to the design and life management of propulsion system life-limited parts, including high-energy rotating parts |
| Reference: | 14 CFR 33.70 |
| Documents for Download: | Draft Document Comment Matrix |
| Comments Due: | September 12, 2025 |
| How to Comment: | Email comments to 9-AVS-TechWriters@faa.gov |
Related Information
- Final Aircraft Certification advisory circulars, other policy documents, and technical standard orders (TSOs) are available on FAA's Dynamic Regulatory System (DRS)
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- FAA Regulations
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- To comment on rulemaking documents, please visit the DOT Docket Management System.
Last updated: Wednesday, August 13, 2025