Federal Aviation Administration, DOT § 23.909
(4) It must be demonstrated in flight condition must be suitably protected that when restarting engines following to prevent ice formation, or it must be a false start, all fuel or vapor is dis- shown that any ice shed into the pro- charged in such a way that it does not peller disc will not create a hazardous constitute a fire hazard. condition. (f) Restart envelope. An altitude and (f) Each pusher propeller must be airspeed envelope must be established marked so that the disc is conspicuous for the airplane for in-flight engine re- under normal daylight ground condi- starting and each installed engine tions. must have a restart capability within (g) If the engine exhaust gases are that envelope. discharged into the pusher propeller (g) Restart capability. For turbine en- disc, it must be shown by tests, or gine powered airplanes, if the min- analysis supported by tests, that the imum windmilling speed of the en- propeller is capable of continuous safe gines, following the in-flight shutdown operation. of all engines, is insufficient to provide (h) All engine cowling, access doors, the necessary electrical power for en- and other removable items must be de- gine ignition, a power source inde- signed to ensure that they will not sep- pendent of the engine-driven electrical arate from the airplane and contact power generating system must be pro- the pusher propeller. vided to permit in-flight engine igni- [Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as tion for restarting. amended by Amdt. 23–26, 45 FR 60171, Sept. 11, 1980; Amdt. 23–29, 49 FR 6847, Feb. 23, 1984; [Amdt. 23–14, 38 FR 31822, Nov. 19, 1973, as Amdt. 23–43, 58 FR 18970, Apr. 9, 1993] amended by Amdt. 23–17, 41 FR 55464, Dec. 20, 1976; Amdt. 23–26, 45 FR 60171, Sept. 11, 1980; § 23.907 Propeller vibration. Amdt. 23–29, 49 FR 6847, Feb. 23, 1984; Amdt. 23–34, 52 FR 1832, Jan. 15, 1987; Amdt. 23–40, 55 (a) Each propeller other than a con- FR 32861, Aug. 10, 1990; Amdt. 23–43, 58 FR ventional fixed-pitch wooden propeller 18970, Apr. 9, 1993; Amdt. 23–51, 61 FR 5136, must be shown to have vibration Feb. 9, 1996; Amdt. 23–53, 63 FR 14798, Mar. 26, stresses, in normal operating condi- 1998; Amdt. 23–54, 65 FR 55854, Sept. 14, 2000] tions, that do not exceed values that have been shown by the propeller man- § 23.904 Automatic power reserve sys- tem. ufacturer to be safe for continuous op- eration. This must be shown by— If installed, an automatic power re- (1) Measurement of stresses through serve (APR) system that automatically direct testing of the propeller; advances the power or thrust on the op- (2) Comparison with similar installa- erating engine(s), when any engine tions for which these measurements fails during takeoff, must comply with have been made; or appendix H of this part. (3) Any other acceptable test method [Doc. No. 26344, 58 FR 18970, Apr. 9, 1993] or service experience that proves the safety of the installation. § 23.905 Propellers. (b) Proof of safe vibration character- (a) Each propeller must have a type istics for any type of propeller, except certificate. for conventional, fixed-pitch, wood pro- (b) Engine power and propeller shaft pellers must be shown where necessary. rotational speed may not exceed the [Doc. No. 4080, 29 FR 17955, Dec. 18, 1964; 30 limits for which the propeller is certifi- FR 258, Jan. 9, 1965, as amended by Amdt. 23– cated. 51, 61 FR 5136, Feb. 9, 1996] (c) Each featherable propeller must have a means to unfeather it in flight. § 23.909 Turbocharger systems. (d) Each component of the propeller (a) Each turbocharger must be ap- blade pitch control system must meet proved under the engine type certifi- the requirements of § 35.42 of this chap- cate or it must be shown that the tur- ter. bocharger system, while in its normal (e) All areas of the airplane forward engine installation and operating in of the pusher propeller that are likely the engine environment— to accumulate and shed ice into the (1) Can withstand, without defect, an propeller disc during any operating endurance test of 150 hours that meets
259
VerDate 11
the applicable requirements of § 33.49 of the level, normal takeoff, or taxing at- this subchapter; and titude, whichever is most critical. In (2) Will have no adverse effect upon addition, for each airplane with con- the engine. ventional landing gear struts using (b) Control system malfunctions, vi- fluid or mechanical means for absorb- brations, and abnormal speeds and ing landing shocks, there must be posi- temperatures expected in service may tive clearance between the propeller not damage the turbocharger com- and the ground in the level takeoff at- pressor or turbine. titude with the critical tire completely (c) Each turbocharger case must be deflated and the corresponding landing able to contain fragments of a com- pressor or turbine that fails at the gear strut bottomed. Positive clear- highest speed that is obtainable with ance for airplanes using leaf spring normal speed control devices inoper- struts is shown with a deflection cor- ative. responding to 1.5g. (d) Each intercooler installation, (b) Aft-mounted propellers. In addition where provided, must comply with the to the clearances specified in para- following— graph (a) of this section, an airplane (1) The mounting provisions of the with an aft mounted propeller must be intercooler must be designed to with- designed such that the propeller will stand the loads imposed on the system; not contact the runway surface when (2) It must be shown that, under the the airplane is in the maximum pitch installed vibration environment, the attitude attainable during normal intercooler will not fail in a manner al- takeoffs and landings. lowing portions of the intercooler to be (c) Water clearance. There must be a ingested by the engine; and clearance of at least 18 inches between (3) Airflow through the intercooler each propeller and the water, unless must not discharge directly on any air- compliance with § 23.239 can be shown plane component (e.g., windshield) un- with a lesser clearance. less such discharge is shown to cause no hazard to the airplane under all op- (d) Structural clearance. There must erating conditions. be— (e) Engine power, cooling character- (1) At least one inch radial clearance istics, operating limits, and procedures between the blade tips and the airplane affected by the turbocharger system in- structure, plus any additional radial stallations must be evaluated. Turbo- clearance necessary to prevent harmful charger operating procedures and limi- vibration; tations must be included in the Air- (2) At least one-half inch longitudinal plane Flight Manual in accordance clearance between the propeller blades with § 23.1581. or cuffs and stationary parts of the air- [Amdt. 23–7, 34 FR 13092, Aug. 13, 1969, as plane; and amended by Amdt. 23–43, 58 FR 18970, Apr. 9, (3) Positive clearance between other 1993] rotating parts of the propeller or spin- ner and stationary parts of the air- § 23.925 Propeller clearance. plane. Unless smaller clearances are sub- stantiated, propeller clearances, with [Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as the airplane at the most adverse com- amended by Amdt. 23–43, 58 FR 18971, Apr. 9, 1993; Amdt. 23–51, 61 FR 5136, Feb. 9, 1996; bination of weight and center of grav- Amdt. 23–48, 61 FR 5148, Feb. 9, 1996] ity, and with the propeller in the most adverse pitch position, may not be less § 23.929 Engine installation ice protec- than the following: tion. (a) Ground clearance. There must be a clearance of at least seven inches (for Propellers (except wooden propellers) each airplane with nose wheel landing and other components of complete en- gear) or nine inches (for each airplane gine installations must be protected with tail wheel landing gear) between against the accumulation of ice as nec- each propeller and the ground with the essary to enable satisfactory func- landing gear statically deflected and in tioning without appreciable loss of
260
VerDate 11