Federal Aviation Administration, DOT § 23.933

affected by the turbocharger system in- clearance necessary to prevent harmful stallations must be evaluated. Turbo- vibration; charger operating procedures and limi- (2) At least one-half inch longitudinal tations must be included in the Air- clearance between the propeller blades plane Flight Manual in accordance or cuffs and stationary parts of the air- with § 23.1581. plane; and (3) Positive clearance between other [Amdt. 23–7, 34 FR 13092, Aug. 13, 1969, as amended by Amdt. 23–43, 58 FR 18970, Apr. 9, rotating parts of the propeller or spin- 1993] ner and stationary parts of the air- plane. § 23.925 Propeller clearance. [Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as Unless smaller clearances are sub- amended by Amdt. 23–43, 58 FR 18971, Apr. 9, stantiated, propeller clearances, with 1993; Amdt. 23–51, 61 FR 5136, Feb. 9, 1996; the airplane at the most adverse com- Amdt. 23–48, 61 FR 5148, Feb. 9, 1996] bination of weight and center of grav- § 23.929 Engine installation ice protec- ity, and with the propeller in the most tion. adverse pitch position, may not be less than the following: Propellers (except wooden propellers) (a) Ground clearance. There must be a and other components of complete en- clearance of at least seven inches (for gine installations must be protected each airplane with nose wheel landing against the accumulation of ice as nec- gear) or nine inches (for each airplane essary to enable satisfactory func- with tail wheel landing gear) between tioning without appreciable loss of each propeller and the ground with the thrust when operated in the icing con- landing gear statically deflected and in ditions for which certification is re- the level, normal takeoff, or taxing at- quested. titude, whichever is most critical. In [Amdt. 23–14, 33 FR 31822, Nov. 19, 1973, as addition, for each airplane with con- amended by Amdt. 23–51, 61 FR 5136, Feb. 9, ventional landing gear struts using 1996] fluid or mechanical means for absorb- ing landing shocks, there must be posi- § 23.933 Reversing systems. tive clearance between the propeller (a) For turbojet and turbofan reversing and the ground in the level takeoff at- systems. (1) Each system intended for titude with the critical tire completely ground operation only must be de- deflated and the corresponding landing signed so that, during any reversal in gear strut bottomed. Positive clear- flight, the engine will produce no more ance for airplanes using leaf spring than flight idle thrust. In addition, it struts is shown with a deflection cor- must be shown by analysis or test, or responding to 1.5g. both, that— (b) Aft-mounted propellers. In addition (i) Each operable reverser can be re- to the clearances specified in para- stored to the forward thrust position; graph (a) of this section, an airplane or with an aft mounted propeller must be (ii) The airplane is capable of contin- designed such that the propeller will ued safe flight and landing under any not contact the runway surface when possible position of the thrust reverser. the airplane is in the maximum pitch (2) Each system intended for in-flight attitude attainable during normal use must be designed so that no unsafe takeoffs and landings. condition will result during normal op- (c) Water clearance. There must be a eration of the system, or from any fail- clearance of at least 18 inches between ure, or likely combination of failures, each propeller and the water, unless of the reversing system under any op- compliance with § 23.239 can be shown erating condition including ground op- with a lesser clearance. eration. Failure of structural elements (d) Structural clearance. There must need not be considered if the prob- be— ability of this type of failure is ex- (1) At least one inch radial clearance tremely remote. between the blade tips and the airplane (3) Each system must have a means structure, plus any additional radial to prevent the engine from producing

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