### DRAFT **DRAFT DRAFT**  **Requesting public**  **comments**

This document does not represent final agency action on this matter and should not be viewed as a guarantee that any

final action will foll ow in this or any other form. **Subject:** P ropeller C ritical P arts **Date:** DRAFT **Initiated By:** ANE
- 110 **AC No:** 3 5
. 16
- DRAFT **Change: 1.**  **P URPOSE** 
. This advisory circular (AC) provides guidance and acceptable methods, but not the only methods, that may

be used to demonstrate compliance with the p ropeller c ritical p arts requirements of Title 14 of the Code of Federal Regulations (14 CFR 35.16 ). This AC provides information about what a propeller critical part is, the identification of propeller critical parts by applicant s , and engineering, manufacture, and maintenance processes for those parts. **2. APPLICABILITY** 
. a. The guidance provided in this document is directed to propeller applicants, manufacturers, modifiers, foreign regulatory au thorities, and Federal Aviation Administration (FAA) designated engineering representatives. b. This material is neither mandatory nor regulatory

in nature and does not constitute a regulation. I t describes acceptable means, but not the only means, for demonstrating compliance with the applicable regulations. We (“the FAA”) will consider other methods an applicant may present to demonstrate compliance. Terms such as “should,” “shall,” “may ,” and “must” are used only in the sense of ensuring applic ability of this particular method of compliance when the method in this document is used. While these guidelines are not mandatory , they are derived from extensive FAA and industry experience in determining compliance with the relevant regulations. I f we find that following this AC would not result in compliance with the applicable regulations, we will not be bound by this AC, and we may

require additional substantiation as the basis for finding compliance. c. This material does not change, create any additional, authorize changes in, or permit deviations from existing regulatory requirements.

### DRAFT **DRAFT DRAFT**  **Requesting public**  **comments**

This document does not represent final agency action on this matter and should not be viewed as a guarantee that any

final action will follow in this or any ot her form. 2 **3. RELATED REGULATIONS** 
. Please check the FAA’s website at **http://ecfr.gpoaccess.gov** for part 35of Title 14 of the Code of Federal Regulations (14 CFR).
a . 14 CFR 35.15, Safety

analy sis. **5. DEFINITIONS**  . For the purpose of this AC, the following definitions apply :
a. Approved L ife . The mandatory replacement life of a part that is approved by the FAA and is listed in the a irworthiness l imitat ion s ection (ALS) of the i nstructions for c ontinued a irworthiness (ICA)
. b
. Engineering Process
. The process that d efines the integrity of p ropeller c ritical p arts throughout their service life.
c . Fixed Process . Processes that should not be changed without proper validation and approval as defined in the engineering plan. d
. Manufacturing Process
. The process that identifies the requirements to produce p ropeller c ritical p art s consistent with the e ngineering p rocess.
e . Prim ary

Failure . Failure of a part that is not the result of prior failure of another part or sy stem. f
. Propeller Critical Part
. A part on the p ropeller whose primary failure can result in a h azardous p ropeller e ffect , as determined by the s afety a na ly sis required by § 35.15. g . Service Management Process
. The process that identifies the c ontinued a irworthiness r equirements of p ropeller c ritical p arts as required by the e ngineering process. **6. INTRODUCTION** 
. a. The failure of a p ropell er c ritical p art could result in a h azardous p ropeller e ffect as defined by § 35.15 . Accordingly , applicant s must meet the requirements of § 35.16 for propeller critical part management
. Section 35.16 require s th at applicants establish the integrity of p ropeller critical parts through defined e ngineering , ma nufacturing, and s ervice m anagement p rocess es . These three processes form a closed
- loop sy stem link ing design intent , as defined by the engineering process, to part manufacture and service ma nagement
. Engineering, manufacturing, and service management work together as an integrated sy stem that recognizes actions in one area may affect all
. b. The e ngineering p rocess defines the requirements , technical data, and actions necessary to establish a nd maintain the integrity of p ropeller c ritical p arts throughout their service life. The e ngineering p rocess and the part life are established before the part is introduc ed into service
. T he engineering process is updated as new information becomes avail able.

### DRAFT **DRAFT DRAFT**  **Requesting public**  **comments**

This document does not represent final agency action on this matter and should not be viewed as a guarantee that any

final action will follow in this or any ot her form. 3 c. The m anufacturing p rocess is a compilation of the controls and procedures, such as the drawings, procedures, specifications, and instructions required to produce and inspect a p ropeller c ritical p art , as defined by the e ngineering p rocess. d. The s ervice m anagement p rocess identifies the procedures for in
- service maintenance, overhaul, and repair to ensure that a p ropeller c ritical p art achieves the requirements defined by the e ngineering p rocess. The s ervice m anagement p rocess forms the basis for in
- service maintenance, overhaul, and repair that are convey ed through the IC A , and the ALS of the IC A constant with the engineering process
. **7. GENERAL** 
. a. The engineering, manufacturing, and service management processes should p rovide clear information for propeller critical part management. “Process” in the context of the proposed requirement does not mean that all the required technical information is within a single document. When relevant information exists elsewhere, the p rocess documents may reference for example, drawings, material specifications, process specifications, as appropriate. These references should be clear enough to sufficiently identify the referenced document so as to allow the design history

of an individ

ual part to be traced. b. When a critical part is inseparable from an assembly , the assembly is identified as a critical part . B oth the inseparable part (s) and the assembl y should be included in the engineering, manufacturing and service management processes. This does not limit applicants from defin ing separable assemblies containing p ropeller c ritical p arts as a p ropeller c ritical p art in support of the engineering process. **8. DEFINING AN ENGINEERING PROCESS** 
. a. In troduction
. The e ngin eering p rocess includes procedures and requirements for how p ropeller c ritical p arts are identified, associated life analy sis is determined , and mandatory in spection intervals
. Each of these is discussed in more detail below. b. Id entify ing Propel ler Critical Parts
. Section 35.15 Safety analy sis requires the identification of all propeller critical parts
. The e ngineering p rocess should require that the drawing (s) distinguish p ropeller c ritical p arts
. c. Li fe Analy sis . The engineering pr ocess should establish the methodology for determining what propeller critical parts are life limited, if any . For those that require a life limit , the approved life is published in the I CA Airworthiness L imitations Section (ALS). ( 1 ) Establi sh ing the Propeller Critical Part L ife . The applicant s engineering process should provide a sy stematic and uniform methodology to predict part life. The a pplicants life prediction methodology

should consider : a irplane operating conditions, engine compati bility , stress

### DRAFT **DRAFT DRAFT**  **Requesting public**  **comments**

This document does not represent final agency action on this matter and should not be viewed as a guarantee that any

final action will follow in this or any ot her form. 4 analy sis, materials data, safe life analy sis and/or damage tolerance analy sis, wear analy sis and service experience. Any

in
- service inspections identified as required to maintain the part life should be incorporated into the IC A of the ALS
. ( 2 ) Maintaining the Propeller Critical Part L ife
. The e ngineering p rocess should include a provision for incorporating design, manufacturing and service data , relative to the condition of p ropeller c ritical p arts , into the part life methodolog y. This is to assure that design changes and changes introduced during manufacture or service will be evaluated, and if necessary , corrective action taken to restore or maintain part life
. d. Mandatory

I nspection I nterval
. The e ngineering p rocess should include a methodology for determin ing any mandatory inspection interval s , and for incorporat ing them into the ALS of the IC A
. **9. DEFINING A MANUFACTURING PROCESS** 
. a. In troduction
. The manufacturing process identifies the requirements to co nsistently produce propeller critical parts as required by the engineering process. T he requirements established by

the m anufacturing p rocess should include engineering requirements , and appl y controls to ensure that manufacturing and inspection methods a nd processes are maintained. The manufacturing process can be broadly grouped as process and source approvals, and part marking. Each is discussed below : b
. Manufacturing Process Approval
. ( 1 ) The essential m anufacturing p rocess es shou ld be reviewed and approved by the appropriate engineering, quality and manufacturing personnel established by the applicant
. C hanges to the manufacturing processes should be subject to the same or similar review and approval process
. The review and appr oval of changes should include an assessment of the impact on the life of the critical part
. The applicant may integrate the manufacturing process with the quality

sy stem to assure conformance for all p ropeller c ritical p arts
. ( 2 ) The applican t should identity the appropriate inspection personnel who will ensur e the manufactured product is consistent with the requirements of the e ngineering p rocess. This group of personnel should also evaluat e and approv e non - conformance disposition s, and all p ropeller c ritical p art manufacturing sources. ( 3 ) The level of detail in the inspection process may vary depending on the process step being considered, the sensitivity of the step, and the level of control necessary to achieve the p ropeller c r itical p art requirements.
c . Source Approval
. The applicant should impose source approval requirements on suppliers of parts, materials or processes that are incorporated into c ritical p art s . Approval means the source has successfully

demonstrated to the applicant that the y have the capability to produce

### DRAFT **DRAFT DRAFT**  **Requesting public**  **comments**

This document does not represent final agency action on this matter and should not be viewed as a guarantee that any

final action will follow in this or any ot her form. 5 parts or materials that satisfy the requirements of the critical part established in the engineering and manufacturing processes. d. Part Marking
. P ropeller c ritical p arts marking should be consistent with 14 CFR part 45
. Propeller c ritical p arts not addressed in p art 45 do not require part number and serial number markings. The procedures for marking p ropeller c ritical p arts should be defined in the m anufacturing or e ngineering p rocess , a s applicable. **10. DEFINING A SERVICE MANAGEMENT PROCESS** 
. a. I ntroduction
. The s ervice m anagement p rocess is part of the process to maintain p ropeller c ritical p arts throughout their service life. The s ervice m anagement p rocess identifie s and co nvey s the requirements for in
- service repair, maintenance, and overhaul to remain consistent with the requirements contained in the e ngineering p rocess. ( 1 ) The IC As and ALS of the I CA, o peration and maintenance manuals, bulletins and other ser vice documents are part of the s ervice m anagement p rocess. The service management process has been developed with the expect ation that general procedures such as pre
- flight or other periodic inspections and overhauls will be accomplished in accordance wit h the published service documents and do not need to be in the ALS of the I CA
. ( 2 ) Critical parts should be identified in the service documents. b. Elements of a Service Management Process
. The s ervice m anagement p rocess should include t he following: (1) Service requirements and procedures to maintain c ontinued a irworthiness
. (2) Propeller installation, maintenance and overhaul procedures
. (3) Airworthiness l imitations
. (4) Repair procedures
. c. Determining the Acceptability of Repair, Maintenance and Overhaul Processes
. (1) Repair, maintenance, and overhaul should be reviewed and approved by the appropriate engineering, quality

and manufacturing personnel established by the appl icant. The review should include an assessment of the impact on the life of the critical part
. C hanges to Repair, maintenance, and overhaul should be subject to the same or similar review and approval process
. d. IC A Statement
. (1) To ensure a closed
- loop between the in
- service parts and the e ngineering p rocess , the applicant should highlight the importance of limits to the repair and maintenance of p ropeller c ritical p arts in the propeller maintenance manuals. Applicants may use the following wording in

### DRAFT **DRAFT DRAFT**  **Requesting public**  **comments**

This document does not represent final agency action on this matter and should not be viewed as a guarantee that any

final action will follow in this or any ot her form. 6 the propeller maintenance manual, or something similar, to highlight the criticality of repairs on p ropeller c ritical p arts , or parts that affect p ropeller c ritical p arts:

“ The following maintenance and repair instructions have been substantiated based on engineering analy sis that expects this product will be operated and maintained using the procedures and inspections provided in the I CA supplied with this product
. ”

**END**