Oxidation, Hot Corrosion, Thermal Fatigue, and Erosion Characteristics Testing to Support 14 CFR, Part 33, § 33.15, Compliancefor Turbine Engines

AC 33-11 · FAA

Public domain · FAAAdvisory Circulars

Overview

The Oxidation, Hot Corrosion, Thermal Fatigue, and Erosion Characteristics Testing to Support 14 CFR, Part 33, § 33.15, Compliancefor Turbine Engines (AC 33-11) is a public-domain FAA advisory circular, republished here as a free chaptered HTML edition with a linked table of contents and the official PDF.

Publisher: FAA
Document: AC 33-11
Pages: 8
Chapters: 2

Key points

This advisory circular (AC) describes acceptable methods for demonstrating compliance with 14 CFR, Part 33, § 33.15 for turbine engine parts.
The guidance is applicable to applicants seeking FAA approval for PMA, TC design changes, STC, or repairs of turbine engine and APU parts.
Comparative assessments of materials must show that replacement parts have equivalent durability characteristics for oxidation, hot corrosion, thermal fatigue, and erosion.
Burner rig testing is recommended to simulate engine conditions for evaluating part performance under extreme conditions.
The document emphasizes that while the methods described are acceptable, they are not mandatory and other compliance methods may be considered.

Frequently asked questions

What is the purpose of AC 33-11?

The purpose of AC 33-11 is to describe acceptable methods for supporting compliance findings related to materials for turbine engine projects under 14 CFR, Part 33, § 33.15.

Who is the intended audience for this advisory circular?

The guidance is intended for applicants requesting FAA approval for PMA, TC design changes, STC, or repairs of turbine engine and APU parts.

What types of tests are recommended for compliance?

Burner rig testing is recommended to evaluate oxidation, hot corrosion, thermal fatigue, and erosion resistance of replacement parts in conditions simulating an aircraft engine.

Are the methods described in this AC mandatory?

No, the methods described in this AC are not mandatory; they are acceptable means of demonstrating compliance, and other methods may also be considered.

What characteristics must be compared for replacement parts?

Replacement parts must be compared for durability characteristics related to oxidation, hot corrosion, thermal fatigue, and erosion to ensure they are at least equivalent to the type design part.

part shape (e.g., airfoils); or effects that otherwise negatively affect part function or durability.

9/23/14 AC 33-11 part shape (e.g., airfoils); or effects that otherwise negatively affect part function or durability.

The consumed material could be the base metal, the protective coating, or protective oxide scale.

(5) Other Criteria.

(a) Weight changes (positive/retention or negative/spalling); (b) Visual inspection for surface damage; (c) Phases of coating before and after oxidation; (d) Examining for microstructure changes in coatings and base metal; (e) Coating phase transformation and volume increase; and (f) Associated cracking and/or spalling.

(6) The replacement part must show to be, at least, equal to the type design part for the above characteristics in terms of part or feature performance and durability.

6. Summary . The methods of compliance identified in this AC may be used to show compliance to § 33.15 for certain material characteristics using comparative assessment. If material specimen testing is used, sample size, specimen design, and test conditions must adequately represent the actual part in its operating environment.

If you have any suggestions for improvements or changes, you may use the template provided at the end of this AC.

Colleen M. D’Alessandro Assistant Manager, Engine and Propeller Directorate Aircraft Certification Service

Next: Appendix A. Advisory Circular (AC) Feedback Information →

Appendix A. Advisory Circular (AC) Feedback Information

9/23/14 AC 33-11 Appendix A. Advisory Circular (AC) Feedback Information If you have comments or recommendations for improving this AC, or suggestions for new items or subjects to be added, or if you find an error, you may let us know about it by using this page as a template and 1) emailing it to 9-AWA-AVS-AIR500-Coord@faa.gov, or 2) faxing it to the attention of the AIR Directives Management Officer at 202-267-3983.

Subject: (insert AC number and title) Date: (insert date) Comment/Recommendation/Error: (Please fill out all that apply) An error has been noted: Paragraph ____________________ Page ______ Type of error (check all that apply): Editorial____ Procedural____ Conceptual____ Description/Comments:______________________________________________ _________________________________________________________________ _________________________________________________________________ Recommend paragraph ______ on page ______ be changed as follows: (attach separate sheets if necessary) _________________________________________________________________ In a future change to this AC, please include coverage on the following subject: (briefly describe what you want added attaching separate sheets if necessary) ________________________________________________________________ Name: __________________________ A-1