Federal Aviation Administration, DOT § 35.19

the propeller installation and oper- (2) The following are regarded as ation instructions required under § 35.3. major propeller effects for variable (e) If the safety analysis depends on pitch propellers: one or more of the following items, (i) An inability to feather the pro- those items must be identified in the peller for feathering propellers. analysis and appropriately substan- (ii) An inability to change propeller tiated. pitch when commanded. (1) Maintenance actions being carried (iii) A significant uncommanded out at stated intervals. This includes change in pitch. verifying that items that could fail in (iv) A significant uncontrollable a latent manner are functioning prop- torque or speed fluctuation. erly. When necessary to prevent haz- [Amdt. 35–8, 73 FR 63346, Oct. 24, 2008, as ardous propeller effects, these mainte- amended by Amdt. 35–9, 78 FR 4041, Jan. 18, nance actions and intervals must be 2013; Amdt. 35–9A, 78 FR 45052, July 26, 2013] published in the instructions for con- tinued airworthiness required under § 35.16 Propeller critical parts. § 35.4. Additionally, if errors in mainte- The integrity of each propeller crit- nance of the propeller system could ical part identified by the safety anal- lead to hazardous propeller effects, the ysis required by § 35.15 must be estab- appropriate maintenance procedures lished by: must be included in the relevant pro- (a) A defined engineering process for peller manuals. ensuring the integrity of the propeller (2) Verification of the satisfactory critical part throughout its service life, functioning of safety or other devices (b) A defined manufacturing process at pre-flight or other stated periods. that identifies the requirements to The details of this satisfactory func- consistently produce the propeller crit- tioning must be published in the appro- ical part as required by the engineering priate manual. process, and (3) The provision of specific instru- (c) A defined service management mentation not otherwise required. process that identifies the continued Such instrumentation must be pub- airworthiness requirements of the pro- lished in the appropriate documenta- peller critical part as required by the tion. engineering process. (4) A fatigue assessment. (f) If applicable, the safety analysis [Amdt. 35–9, 78 FR 4042, Jan. 18, 2013] must include, but not be limited to, as- § 35.17 Materials and manufacturing sessment of indicating equipment, methods. manual and automatic controls, gov- ernors and propeller control systems, (a) The suitability and durability of synchrophasers, synchronizers, and materials used in the propeller must: propeller thrust reversal systems. (1) Be established on the basis of ex- (g) Unless otherwise approved by the perience, tests, or both. Administrator and stated in the safety (2) Account for environmental condi- analysis, the following failure defini- tions expected in service. tions apply to compliance with this (b) All materials and manufacturing part. methods must conform to specifica- (1) The following are regarded as haz- tions acceptable to the Administrator. ardous propeller effects: (c) The design values of properties of materials must be suitably related to (i) The development of excessive the most adverse properties stated in drag. the material specification for applica- (ii) A significant thrust in the oppo- ble conditions expected in service. site direction to that commanded by the pilot. [Amdt. 35–8, 73 FR 63347, Oct. 24, 2008] (iii) The release of the propeller or any major portion of the propeller. § 35.19 Durability. (iv) A failure that results in excessive Each part of the propeller must be unbalance. designed and constructed to minimize

901

VerDate Mar<15>2010 10:12 Mar 18, 2014 Jkt 232046 PO 00000 Frm 00911 Fmt 8010 Sfmt 8010 Y:\SGML\232046.XXX 232046 pmangrum on DSK3VPTVN1PROD with CFR § 35.21 14 CFR Ch. I (1–1–14 Edition)

the development of any unsafe condi- (a) The propeller control system tion of the propeller between overhaul must be designed, constructed and vali- periods. dated to show that: (1) The propeller control system, op- § 35.21 Variable and reversible pitch erating in normal and alternative oper- propellers. ating modes and in transition between (a) No single failure or malfunction operating modes, performs the func- in the propeller system will result in tions defined by the applicant through- unintended travel of the propeller out the declared operating conditions blades to a position below the in-flight and flight envelope. low-pitch position. The extent of any (2) The propeller control system intended travel below the in-flight low- functionality is not adversely affected pitch position must be documented by by the declared environmental condi- the applicant in the appropriate manu- tions, including temperature, electro- als. Failure of structural elements need magnetic interference (EMI), high in- tensity radiated fields (HIRF) and not be considered if the occurrence of lightning. The environmental limits to such a failure is shown to be extremely which the system has been satisfac- remote under § 35.15. torily validated must be documented in (b) For propellers incorporating a the appropriate propeller manuals. method to select blade pitch below the (3) A method is provided to indicate in-flight low pitch position, provisions that an operating mode change has oc- must be made to sense and indicate to curred if flight crew action is required. the flight crew that the propeller In such an event, operating instruc- blades are below that position by an tions must be provided in the appro- amount defined in the installation priate manuals. manual. The method for sensing and (b) The propeller control system indicating the propeller blade pitch po- must be designed and constructed so sition must be such that its failure that, in addition to compliance with does not affect the control of the pro- § 35.15: peller. (1) No single failure or malfunction of [Amdt. 35–8, 73 FR 63347, Oct. 24, 2008] electrical or electronic components in the control system results in a haz- § 35.22 Feathering propellers. ardous propeller effect. (2) Failures or malfunctions directly (a) Feathering propellers are in- affecting the propeller control system tended to feather from all flight condi- in a typical airplane, such as struc- tions, taking into account expected tural failures of attachments to the wear and leakage. Any feathering and control, fire, or overheat, do not lead unfeathering limitations must be docu- to a hazardous propeller effect. mented in the appropriate manuals. (3) The loss of normal propeller pitch (b) Propeller pitch control systems control does not cause a hazardous pro- that use engine oil to feather must in- peller effect under the intended oper- corporate a method to allow the pro- ating conditions. peller to feather if the engine oil sys- (4) The failure or corruption of data tem fails. or signals shared across propellers does (c) Feathering propellers must be de- not cause a hazardous propeller effect. signed to be capable of unfeathering (c) Electronic propeller control sys- after the propeller system has sta- tem imbedded software must be de- bilized to the minimum declared out- signed and implemented by a method side air temperature. approved by the Administrator that is consistent with the criticality of the [Amdt. 35–8, 73 FR 63347, Oct. 24, 2008] performed functions and that mini- mizes the existence of software errors. § 35.23 Propeller control system. (d) The propeller control system The requirements of this section must be designed and constructed so apply to any system or component that that the failure or corruption of air- controls, limits or monitors propeller plane-supplied data does not result in functions. hazardous propeller effects.

902

VerDate Mar<15>2010 10:12 Mar 18, 2014 Jkt 232046 PO 00000 Frm 00912 Fmt 8010 Sfmt 8010 Y:\SGML\232046.XXX 232046 pmangrum on DSK3VPTVN1PROD with CFR