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Subpart B--Flight 25.21 Proof of compliance. 25.101 General. Controllability and Maneuverability 25.143 General. 25.161 Trim. 25.171 General. 25.201 Stall demonstration. Ground and Water Handling Characteristics 25.231 Longitudinal stability and control. Miscellaneous Flight Requirements 25.251 Vibration and buffeting. |
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(a) Each requirement of this subpart must be met at each appropriate combination of weight and center of gravity within the range of loading conditions for which certification is requested. This must be shown- (1) By tests upon an airplane of the type for which certification is requested, or by calculations based on, and equal in accuracy to, the results of testing; and (2) By systematic investigation of each probable combination of weight and center of gravity, if compliance cannot be reasonably inferred from combinations investigated. (b) [Reserved] (c) The controllability, stability, trim, and stalling characteristics of the airplane must be shown for each altitude up to the maximum expected in operation. (d) Parameters critical for the test being conducted, such as weight, loading (center of gravity and inertia), airspeed, power, and wind, must be maintained within acceptable tolerances of the critical values during flight testing. (e) If compliance with the flight characteristics requirements is dependent upon a stability augmentation system or upon any other automatic or power operated system, compliance must be shown with Secs. 25.671 and 25.672. (f) In meeting the requirements of Secs. 25.105(d), 25.125, 25.233, and 25.237, the wind velocity must be measured at a height of 10 meters above the surface, or corrected for the difference between the height at which the wind velocity is measured and the 10-meter height. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-23, 35 FR 5671, Apr. 8, 1970; Amdt. 25-42, 43 FR 2320, Jan. 16, 1978; Amdt. 25-72, 55 FR 29774, July 20, 1990] Sec. 25.23 Load distribution limits. (a) Ranges of weights and centers of gravity within which the airplane may be safely operated must be established. If a weight and center of gravity combination is allowable only within certain load distribution limits (such as spanwise) that could be inadvertently exceeded, these limits and the corresponding weight and center of gravity combinations must be established. (b) The load distribution limits may not exceed-- (1) The selected limits; (2) The limits at which the structure is proven; or (3) The limits at which compliance with each applicable flight requirement of this subpart is shown. Sec. 25.25 Weight limits. (a) Maximum weights. Maximum weights corresponding to the airplane operating conditions (such as ramp, ground or water taxi, takeoff, en route, and landing), environmental conditions (such as altitude and temperature), and loading conditions (such as zero fuel weight, center of gravity position and weight distribution) must be established so that they are not more than- (1) The highest weight selected by the applicant for the particular conditions; or (2) The highest weight at which compliance with each applicable structural loading and flight requirement is shown, except that for airplanes equipped with standby power rocket engines the maximum weight must not be more than the highest weight established in accordance with Appendix E of this part; or (3) The highest weight at which compliance is shown with the certification requirements of Part 36 of this chapter. (b) Minimum weight. The minimum weight (the lowest weight at which compliance with each applicable requirement of this part is shown) must be established so that it is not less than-- (1) The lowest weight selected by the applicant; (2) The design minimum weight (the lowest weight at which compliance with each structural loading condition of this part is shown); or (3) The lowest weight at which compliance with each applicable flight requirement is shown. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-23, 35 FR 5671, Apr. 8, 1970; Amdt. 25-63, 53 FR 16365, May 6, 1988] Sec. 25.27 Center of gravity limits. The extreme forward and the extreme aft center of gravity limitations must be established for each practicably separable operating condition. No such limit may lie beyond-- (a) The extremes selected by the applicant; (b) The extremes within which the structure is proven; or (c) The extremes within which compliance with each applicable flight requirement is shown. Sec. 25.29 Empty weight and corresponding center of gravity. (a) The empty weight and corresponding center of gravity must be determined by weighing the airplane with-- (1) Fixed ballast; (2) Unusable fuel determined under Sec. 25.959; and (3) Full operating fluids, including-- (i) Oil; (ii) Hydraulic fluid; and (iii) Other fluids required for normal operation of airplane systems, except potable water, lavatory precharge water, and fluids intended for injection in the engine. (b) The condition of the airplane at the time of determining empty weight must be one that is well defined and can be easily repeated. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-42, 43 FR 2320, Jan. 16, 1978; Amdt. 25-72, 55 FR 29774, July 20, 1990] Sec. 25.31 Removable ballast. Removable ballast may be used on showing compliance with the flight requirements of this subpart. Sec. 25.33 Propeller speed and pitch limits. (a) The propeller speed and pitch must be limited to values that will ensure- (1) Safe operation under normal operating conditions; and (2) Compliance with the performance requirements of Secs. 25.101 through 25.125. (b) There must be a propeller speed limiting means at the governor. It must limit the maximum possible governed engine speed to a value not exceeding the maximum allowable r.p.m. (c) The means used to limit the low pitch position of the propeller blades must be set so that the engine does not exceed 103 percent of the maximum allowable engine rpm or 99 percent of an approved maximum overspeed, whichever is greater, with-- (1) The propeller blades at the low pitch limit and governor inoperative; (2) The airplane stationary under standard atmospheric conditions with no wind; and (3) The engines operating at the takeoff manifold pressure limit for reciprocating engine powered airplanes or the maximum takeoff torque limit for turbopropeller engine-powered airplanes. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-57, 49 FR 6848, Feb. 23, 1984; Amdt.
25-72, 55 FR 29774, July 20, 1990] |
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(a) Unless otherwise prescribed, airplanes must meet the applicable performance requirements of this subpart for ambient atmospheric conditions and still air. (b) The performance, as affected by engine power or thrust, must be based on the following relative humidities; (1) For turbine engine powered airplanes, a relative humidity of-- (i) 80 percent, at and below standard temperatures; and (ii) 34 percent, at and above standard temperatures plus 50 deg. F. Between these two temperatures, the relative humidity must vary linearly. (2) For reciprocating engine powered airplanes, a relative humidity of 80 percent in a standard atmosphere. Engine power corrections for vapor pressure must be made in accordance with the following table:
(c) The performance must correspond to the propulsive thrust available under the particular ambient atmospheric conditions, the particular flight condition, and the relative humidity specified in paragraph (b) of this section. The available propulsive thrust must correspond to engine power or thrust, not exceeding the approved power or thrust less-- (1) Installation losses; and (2) The power or equivalent thrust absorbed by the accessories and services appropriate to the particular ambient atmospheric conditions and the particular flight condition. (d) Unless otherwise prescribed, the applicant must select the takeoff, en route, approach, and landing configurations for the airplane. (e) The airplane configurations may vary with weight, altitude, and temperature, to the extent they are compatible with the operating procedures required by paragraph (f) of this section. (f) Unless otherwise prescribed, in determining the accelerate-stop distances, takeoff flight paths, takeoff distances, and landing distances, changes in the airplane's configuration, speed, power, and thrust, must be made in accordance with procedures established by the applicant for operation in service. (g) Procedures for the execution of balked landings and missed approaches associated with the conditions prescribed in Secs. 25.119 and 25.121(d) must be established. (h) The procedures established under paragraphs (f) and (g) of this section must-- (1) Be able to be consistently executed in service by crews of average skill; (2) Use methods or devices that are safe and reliable; and (3) Include allowance for any time delays, in the execution of the procedures, that may reasonably be expected in service. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-38, 41 FR 55466, Dec. 20, 1976] Sec. 25.103 Stalling speed. (a) VS is the calibrated stalling speed, or the minimum steady flight speed, in knots, at which the airplane is controllable, with-- (1) Zero thrust at the stalling speed, or, if the resultant thrust has no appreciable effect on the stalling speed, with engines idling and throttles closed; (2) Propeller pitch controls (if applicable) in the position necessary for compliance with paragraph (a)(1) of this section and the airplane in other respects (such as flaps and landing gear) in the condition existing in the test in which VS is being used; (3) The weight used when VS is being used as a factor to determine compliance with a required performance standard; and (4) The most unfavorable center of gravity allowable. (b) The stalling speed VS is the minimum speed obtained as follows: (1) Trim the airplane for straight flight at any speed not less than 1.2 VS or more than 1.4 VS At a speed sufficiently above the stall speed to ensure steady conditions, apply the elevator control at a rate so that the airplane speed reduction does not exceed one knot per second. (2) Meet the flight characteristics provisions of Sec. 25.203. Sec. 25.105 Takeoff. (a) The takeoff speeds described in Sec. 25.107, the accelerate-stop distance described in Sec. 25.109, the takeoff path described in Sec. 25.111, and the takeoff distance and takeoff run described in Sec. 25.113, must be determined-- (1) At each weight, altitude, and ambient temperature within the operational limits selected by the applicant; and (2) In the selected configuration for takeoff. (b) No takeoff made to determine the data required by this section mayrequire exceptional piloting skill or alertness. (c) The takeoff data must be based on-- (1) A smooth, dry, hard-surfaced runway, in the case of land planes and amphibians; (2) Smooth water, in the case of seaplanes and amphibians; and (3) Smooth, dry snow, in the case of skiplanes. (d) The takeoff data must include, within the established operational limits of the airplane, the following operational correction factors: (1) Not more than 50 percent of nominal wind components along the takeoff path opposite to the direction of takeoff, and not less than 150 percent of nominal wind components along the takeoff path in the direction of takeoff. (2) Effective runway gradients. Sec. 25.107 Takeoff speeds. (a) V1 must be established in relation to VEF as follows: (1) VEF is the calibrated airspeed at which the critical engine is assumed to fail. VEF must be selected by the applicant, but may not be less than VmcG determined under Sec. 25.149(e). (2) V1, in terms of calibrated airspeed, is the takeoff decision speed selected by the applicant; however, V1 may not be less than VEF plus the speed gained with the critical engine inoperative during the time interval between the instant at which the critical engine is failed, and the instant at which the pilot recognizes and reacts to the engine failure, as indicated by the pilot's application of the first retarding means during accelerate stop tests. (b) V2MIN, in terms of calibrated airspeed, may not be less than-- (1) 1.2 VS for-- (i) Two-engine and three-engine turbopropeller and reciprocating engine powered airplanes; and (ii) Turbojet powered airplanes without provisions for obtaining a significant reduction in the one-engine-inoperative power-on stalling speed; (2) 1.15 VS for-- (i) Turbopropeller and reciprocating engine powered airplanes with more than three engines; and (ii) Turbojet powered airplanes with provisions for obtaining a significant reduction in the one-engine-inoperative power-on stalling speed; and (3) 1.10 times VMC established under Sec. 25.149. (c) V2, in terms of calibrated airspeed, must be selected by the applicant to provide at least the gradient of climb required by Sec. 25.121(b) but may not be less than-- (1) V2MIN, and (2) VR plus the speed increment attained (in accordance with Sec. 25.111 (c)(2)) before reaching a height of 35 feet above the takeoff surface. (d) VMU is the calibrated airspeed at and above which the airplane can safely lift off the ground, and continue the takeoff. VMU speeds must be selected by the applicant throughout the range of thrust-to-weight ratios to be certificated. These speeds may be established from free air data if these data are verified by ground takeoff tests. (e) VR, in terms of calibrated airspeed, must be selected in accordance with the conditions of paragraphs (e) (1) through (4) of this section: (1) VR may not be less than-- (i) V1; (ii) 105 percent of VMC; (iii) The speed (determined in accordance with Sec. 25.111(c)(2)) that allows reaching V2 before reaching a height of 35 feet above the takeoff surface; or (iv) A speed that, if the airplane is rotated at its maximum practicable rate, will result in a VLOF of not less than 110 percent of VMU in the all engines-operating condition and not less than 105 percent of VMU determined at the thrust-to-weight ratio corresponding to the one-engine-inoperative condition. (2) For any given set of conditions (such as weight, configuration, and temperature), a single value of VR, obtained in accordance with this paragraph, must be used to show compliance with both the one-engine inoperative and the all-engines-operating takeoff provisions. (3) It must be shown that the one-engine-inoperative takeoff distance, using a rotation speed of 5 knots less than VR established in accordance with paragraphs (e)(1) and (2) of this section, does not exceed the corresponding one-engine-inoperative takeoff distance using the established VR. The takeoff distances must be determined in accordance with Sec. 25.113(a)(1). (4) Reasonably expected variations in service from the established takeoff procedures for the operation of the airplane (such as over-rotation of the airplane and out-of-trim conditions) may not result in unsafe flight characteristics or in marked increases in the scheduled takeoff distances established in accordance with Sec. 25.113(a). (f) VLOF is the calibrated airspeed at which the airplane first becomes airborne. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-38, 41 FR 55466, Dec. 20, 1976; Amdt. 25-42, 43 FR 2320, Jan. 16, 1978] Sec. 25.109 Accelerate-stop distance. (a) The accelerate-stop distance is the greater of the following distances: (1) The sum of the distances necessary to-- (i) Accelerate the airplane from a standing start to VEF with all engines operating; (ii) Accelerate the airplane from VEF to V1 and continue the acceleration for 2.0 seconds after V1 is reached, assuming the critical engine fails at VEF; and (iii) Come to a full stop from the point reached at the end of the acceleration period prescribed in paragraph (a)(1)(ii) of this section, assuming that the pilot does not apply any means of retarding the airplane until that point is reached and that the critical engine is still inoperative. (2) The sum of the distances necessary to-- (i) Accelerate the airplane from a standing start to V1 and continue the acceleration for 2.0 seconds after V1 is reached with all engines operating; and (ii) Come to a full stop from the point reached at the end of the acceleration period prescribed in paragraph (a)(2)(i) of this section, assuming that the pilot does not apply any means of retarding the airplane until that point is reached and that all engines are still operating. (b) Means other than wheel brakes may be used to determine the accelerate- stop distance if that means-- (1) Is safe and reliable; (2) Is used so that consistent results can be expected under normal operating conditions; and (3) Is such that exceptional skill is not required to control the airplane. (c) The landing gear must remain extended throughout the accelerate-stop distance. (d) If the accelerate-stop distance includes a stopway with surface characteristics substantially different from those of a smooth hard-surfaced runway, the takeoff data must include operational correction factors for the accelerate-stop distance. The correction factors must account for the particular surface characteristics of the stopway and the variations in these characteristics with seasonal weather conditions (such as temperature, rain, snow, and ice) within the established operational limits. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-42, 43 FR 2321, Jan. 16, 1978] Sec. 25.111 Takeoff path. (a) The takeoff path extends from a standing start to a point in the takeoff at which the airplane is 1,500 feet above the takeoff surface, or at which the transition from the takeoff to the en route configuration is completed and a speed is reached at which compliance with Sec. 25.121(c) is shown, whichever point is higher. In addition-- (1) The takeoff path must be based on the procedures prescribed in Sec. 25.101(f); (2) The airplane must be accelerated on the ground to VEF, at which point the critical engine must be made inoperative and remain inoperative for the rest of the takeoff; and (3) After reaching VEF, the airplane must be accelerated to V2. (b) During the acceleration to speed V2, the nose gear may be raised off the ground at a speed not less than VR. However, landing gear retraction may not be begun until the airplane is airborne. (c) During the takeoff path determination in accordance with paragraphs (a) and (b) of this section-- (1) The slope of the airborne part of the takeoff path must be positive at each point; (2) The airplane must reach V2 before it is 35 feet above the takeoff surface and must continue at a speed as close as practical to, but not less than V2, until it is 400 feet above the takeoff surface; (3) At each point along the takeoff path, starting at the point at which the airplane reaches 400 feet above the takeoff surface, the available gradient of climb may not be less than-- (i) 1.2 percent for two-engine airplanes; (ii) 1.5 percent for three-engine airplanes; and (iii) 1.7 percent for four-engine airplanes; and (4) Except for gear retraction and propeller feathering, the airplane configuration may not be changed, and no change in power or thrust that requires action by the pilot may be made, until the airplane is 400 feet above the takeoff surface. (d) The takeoff path must be determined by a continuous demonstrated takeoff or by synthesis from segments. If the takeoff path is determined by the segmental method-- (1) The segments must be clearly defined and must be related to the distinct changes in the configuration, power or thrust, and speed; (2) The weight of the airplane, the configuration, and the power or thrust must be constant throughout each segment and must correspond to the most critical condition prevailing in the segment; (3) The flight path must be based on the airplane's performance without ground effect; and (4) The takeoff path data must be checked by continuous demonstrated takeoffs up to the point at which the airplane is out of ground effect and its speed is stabilized, to ensure that the path is conservative relative to the continous path. The airplane is considered to be out of the ground effect when it reaches a height equal to its wing span. (e) For airplanes equipped with standby power rocket engines, the takeoff path may be determined in accordance with section II of Appendix E. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-6, 30 FR 8468, July 2, 1965; Amdt. 25-42, 43 FR 2321, Jan. 16, 1978; Amdt. 25-54, 45 FR 60172, Sept. 11, 1980; Amdt. 25-72, 55 FR 29774, July 20, 1990] Sec. 25.113 Takeoff distance and takeoff run. (a) Takeoff distance is the greater of-- (1) The horizontal distance along the takeoff path from the start of the takeoff to the point at which the airplane is 35 feet above the takeoff surface, determined under Sec. 25.111; or (2) 115 percent of the horizontal distance along the takeoff path, with all engines operating, from the start of the takeoff to the point at which the airplane is 35 feet above the takeoff surface, as determined by a procedure consistent with Sec. 25.111. (b) If the takeoff distance includes a clearway, the takeoff run is the greater of-- (1) The horizontal distance along the takeoff path from the start of the takeoff to a point equidistant between the point at which VLOF is reached and the point at which the airplane is 35 feet above the takeoff surface, as determined under Sec. 25.111; or (2) 115 percent of the horizontal distance along the takeoff path, with all engines operating, from the start of the takeoff to a point equidistant between the point at which VLOF is reached and the point at which the airplane is 35 feet above the takeoff surface, determined by a procedure consistent with Sec. 25.111. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-23, 35 FR 5671, Apr. 8, 1970] Sec. 25.115 Takeoff flight path. (a) The takeoff flight path begins 35 feet above the takeoff surface at the end of the takeoff distance determined in accordance with Sec. 25.113(a). (b) The net takeoff flight path data must be determined so that they represent the actual takeoff flight paths (determined in accordance with Sec. 25.111 and with paragraph (a) of this section) reduced at each point by a gradient of climb equal to-- (1) 0.8 percent for two-engine airplanes; (2) 0.9 percent for three-engine airplanes; and (3) 1.0 percent for four-engine airplanes. (c) The prescribed reduction in climb gradient may be applied as an equivalent reduction in acceleration along that part of the takeoff flight path at which the airplane is accelerated in level flight. Sec. 25.117 Climb: general. Compliance with the requirements of Secs. 25.119 and 25.121 must be shown at each weight, altitude, and ambient temperature within the operational limits established for the airplane and with the most unfavorable center of gravity for each configuration. Sec. 25.119 Landing climb: All-engine-operating. In the landing configuration, the steady gradient of climb may not be less than 3.2 percent, with-- (a) The engines at the power or thrust that is available eight seconds after initiation of movement of the power or thrust controls from the minimum flight idle to the go-around power or thrust setting; and (b) A climb speed of not more than 1.3 VS. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-84, 60 FR 30749, June 9, 1995] Sec. 25.121 Climb: One-engine-inoperative. (a) Takeoff; landing gear extended. In the critical takeoff configuration existing along the flight path (between the points at which the airplane reaches VLOF and at which the landing gear is fully retracted) and in the configuration used in Sec. 25.111 but without ground effect, the steady gradient of climb must be positive for two-engine airplanes, and not less than 0.3 percent for three-engine airplanes or 0.5 percent for four-engine airplanes, at VLOF and with-- (1) The critical engine inoperative and the remaining engines at the power or thrust available when retraction of the landing gear is begun in accordance with Sec. 25.111 unless there is a more critical power operating condition existing later along the flight path but before the point at which the landing gear is fully retracted; and (2) The weight equal to the weight existing when retraction of the landing gear is begun, determined under Sec. 25.111. (b) Takeoff; landing gear retracted. In the takeoff configuration existing at the point of the flight path at which the landing gear is fully retracted, and in the configuration used in Sec. 25.111 but without ground effect, the steady gradient of climb may not be less than 2.4 percent for two-engine airplanes, 2.7 percent for three-engine airplanes, and 3.0 percent for four engine airplanes, at V2 and with-- (1) The critical engine inoperative, the remaining engines at the takeoff power or thrust available at the time the landing gear is fully retracted, determined under Sec. 25.111, unless there is a more critical power operating condition existing later along the flight path but before the point where the airplane reaches a height of 400 feet above the takeoff surface; and (2) The weight equal to the weight existing when the airplane's landing gear is fully retracted, determined under Sec. 25.111. (c) Final takeoff. In the en route configuration at the end of the takeoff path determined in accordance with Sec. 25.111, the steady gradient of climb may not be less than 1.2 percent for two-engine airplanes, 1.5 percent for three-engine airplanes, and 1.7 percent for four-engine airplanes, at not less than 1.25 VS and with-- (1) The critical engine inoperative and the remaining engines at the available maximum continuous power or thrust; and (2) The weight equal to the weight existing at the end of the takeoff path, determined under Sec. 25.111. (d) Approach. In the approach configuration corresponding to the normal all-engines-operating procedure in which VS for this configuration does not exceed 110 percent of the VS for the related landing configuration, the steady gradient of climb may not be less than 2.1 percent for two-engine airplanes, 2.4 percent for three-engine airplanes, and 2.7 percent for four engine airplanes, with-- (1) The critical engine inoperative, the remaining engines at the go-around power or thrust setting; (2) The maximum landing weight; and (3) A climb speed established in connection with normal landing procedures, but not exceeding 1.5 VS. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-84, 60 FR 30749, June 9, 1995$ Sec. 25.123 En route flight paths. (a) For the en route configuration, the flight paths prescribed in paragraphs (b) and (c) of this section must be determined at each weight, altitude, and ambient temperature, within the operating limits established for the airplane. The variation of weight along the flight path, accounting for the progressive consumption of fuel and oil by the operating engines, may be included in the computation. The flight paths must be determined at any selected speed, with-- (1) The most unfavorable center of gravity; (2) The critical engines inoperative; (3) The remaining engines at the available maximum continuous power or thrust; and (4) The means for controlling the engine-cooling air supply in the position that provides adequate cooling in the hot-day condition. (b) The one-engine-inoperative net flight path data must represent the actual climb performance diminished by a gradient of climb of 1.1 percent for two-engine airplanes, 1.4 percent for three-engine airplanes, and 1.6 percent for four-engine airplanes. (c) For three- or four-engine airplanes, the two-engine-inoperative net flight path data must represent the actual climb performance diminished by a gradient of climb of 0.3 percent for three-engine airplanes and 0.5 percent for four-engine airplanes. Sec. 25.125 Landing. (a) The horizontal distance necessary to land and to come to a complete stop (or to a speed of approximately 3 knots for water landings) from a point 50 feet above the landing surface must be determined (for standard temperatures, at each weight, altitude, and wind within the operational limits established by the applicant for the airplane) as follows: (1) The airplane must be in the landing configuration. (2) A stabilized approach, with a calibrated airspeed of not less than 1.3 VS or VMCL, whichever is greater, must be maintained down to the 50 foot height. (3) Changes in configuration, power or thrust, and speed, must be made in accordance with the established procedures for service operation. (4) The landing must be made without excessive vertical acceleration, tendency to bounce, nose over, ground loop, porpoise, or water loop. (5) The landings may not require exceptional piloting skill or alertness. (b) For landplanes and amphibians, the landing distance on land must be determined on a level, smooth, dry, hard-surfaced runway. In addition- (1) The pressures on the wheel braking systems may not exceed those specified by the brake manufacturer; (2) The brakes may not be used so as to cause excessive wear of brakes or tires; and (3) Means other than wheel brakes may be used if that means-- (i) Is safe and reliable; (ii) Is used so that consistent results can be expected in service; and (iii) Is such that exceptional skill is not required to control the airplane. (c) For seaplanes and amphibians, the landing distance on water must be determined on smooth water. (d) For skiplanes, the landing distance on snow must be determined on smooth, dry, snow. (e) The landing distance data must include correction factors for not more than 50 percent of the nominal wind components along the landing path opposite to the direction of landing, and not less than 150 percent of the nominal wind components along the landing path in the direction of landing. (f) If any device is used that depends on the operation of any engine, and if the landing distance would be noticeably increased when a landing is made with that engine inoperative, the landing distance must be determined with that engine inoperative unless the use of compensating means will result in a landing distance not more than that with each engine operating. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-72, 55 FR 29774, July 20, 1990; Amdt.
25-84, 60 FR 30749, June 9, 1995] |
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(a) The airplane must be safely controllable and maneuverable during-- (1) Takeoff; (2) Climb; (3) Level flight; (4) Descent; and (5) Landing. (b) It must be possible to make a smooth transition from one flight condition to any other flight condition without exceptional piloting skill, alertness, or strength, and without danger of exceeding the airplane limit load factor under any probable operating conditions, including-- (1) The sudden failure of the critical engine; (2) For airplanes with three or more engines, the sudden failure of the second critical engine when the airplane is in the en route, approach, or landing configuration and is trimmed with the critical engine inoperative; and (3) Configuration changes, including deployment or retraction of deceleration devices. (c) The following table prescribes, for conventional wheel type controls, the maximum control forces permitted during the testing required by paragraphs (a) and (b) of this section:
(d) Approved operating procedures or conventional operating practices must be followed when demonstrating compliance with the control force limitations for short term application that are prescribed in paragraph (c) of this section. The airplane must be in trim, or as near to being in trim as practical, in the immediately preceding steady flight condition. For the takeoff condition, the airplane must be trimmed according to the approved operating procedures. (e) When demonstrating compliance with the control force limitations for long term application that are prescribed in paragraph (c) of this section, the airplane must be in trim, or as near to being in trim as practical. (f) When maneuvering at a constant airspeed or Mach number (up to VFC/MFC), the stick forces and the gradient of the stick force versus maneuvering load factor must lie within satisfactory limits. The stick forces must not be so great as to make excessive demands on the pilot's strength when maneuvering the airplane, and must not be so low that the airplane can easily be overstressed inadvertently. Changes of gradient that occur with changes of load factor must not cause undue difficulty in maintaining control of the airplane, and local gradients must not be so low as to result in a danger of overcontrolling. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-42, 43 FR 2321, Jan. 16, 1978; Amdt. 25-84, 60 FR 30749, June 9, 1995] Sec. 25.145 Longitudinal control. (a) It must be possible at any speed between the trim speed prescribed in Sec. 25.103(b)(1) and Vs, to pitch the nose downward so that the acceleration to this selected trim speed is prompt with-- (1) The airplane trimmed at the trim speed prescribed in Sec. 25.103(b)(1). (2) The landing gear extended; (3) The wing flaps (i) retracted and (ii) extended; and (4) Power (i) off and (ii) at maximum continuous power on the engines. (b) With the landing gear extended, no change in trim control, or exertion of more than 50 pounds control force (representative of the maximum short term force that can be applied readily by one hand) may be required for the following maneuvers: (1) With power off, flaps retracted, and the airplane trimmed at 1.4 VS1, extend the flaps as rapidly as possible while maintaining the airspeed at approximately 40 percent above the stalling speed existing at each instant throughout the maneuver. (2) Repeat paragraph (b)(1) except initially extend the flaps and then retract them as rapidly as possible. (3) Repeat paragraph (b)(2), except at the go-around power or thrust setting. (4) With power off, flaps retracted, and the airplane trimmed at 1.4 VSI, rapidly set go-around power or thrust while maintaining the same airspeed. (5) Repeat paragraph (b)(4) except with flaps extended. (6) With power off, flaps extended, and the airplane trimmed at 1.4 VS1, obtain and maintain airspeeds between 1.1 VS1, and either 1.7 VS1, or VFE, whichever is lower. (c) Is must be possible, without exceptional piloting skill, to prevent loss of altitude when complete retraction of the high lift devices from any position is begun during steady, straight, level flight at 1.1 VS1 for propeller powered airplanes, or 1.2 VS1 for turbojet powered airplanes, with-- (1) Simultaneous movement of the power or thrust controls to the go-around power or thrust setting; (2) The landing gear extended; and (3) The critical combinations of landing weights and altitudes. If gated high-lift device control positions are provided, retraction must be shown from any position from the maximum landing position to the first gated position, between gated positions, and from the last gated position to the full retraction position. In addition, the first gated control position from the landing position must correspond with the high-lift devices configuration used to establish the go-around procedure from the landing configuration. Each gated control position must require a separate and distinct motion of the control to pass through the gated position and must have features to prevent inadvertent movement of the control through the gated position. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-23, 35 FR 5671, Apr. 8, 1970; Amdt. 25-72, 55 FR 29774, July 20, 1990; Amdt. 25-84, 60 FR 30749, June 9, 1995] Sec. 25.147 Directional and lateral control. (a) Directional control; general. It must be possible, with the wings level, to yaw into the operative engine and to safely make a reasonably sudden change in heading of up to 15 degrees in the direction of the critical inoperative engine. This must be shown at 1.4Vs1 for heading changes up to 15 degrees (except that the heading change at which the rudder pedal force is 150 pounds need not be exceeded), and with-- (1) The critical engine inoperative and its propeller in the minimum drag position; (2) The power required for level flight at 1.4 VS1, but not more than maximum continuous power; (3) The most unfavorable center of gravity; (4) Landing gear retracted; (5) Flaps in the approach position; and (6) Maximum landing weight. (b) Directional control; airplanes with four or more engines. Airplanes with four or more engines must meet the requirements of paragraph (a) of this section except that-- (1) The two critical engines must be inoperative with their propellers (if applicable) in the minimum drag position; (2) [Reserved] (3) The flaps must be in the most favorable climb position. (c) Lateral control; general. It must be possible to make 20 deg. banked turns, with and against the inoperative engine, from steady flight at a speed equal to 1.4 VS1, with-- (1) The critical engine inoperative and its propeller (if applicable) in the minimum drag position; (2) The remaining engines at maximum continuous power; (3) The most unfavorable center of gravity; (4) Landing gear (i) retracted and (ii) extended; (5) Flaps in the most favorable climb position; and (6) Maximum takeoff weight. (d) Lateral control; airplanes with four or more engines. Airplanes with four or more engines must be able to make 20 deg. banked turns, with and against the inoperative engines, from steady flight at a speed equal to 1.4 VS1, with maximum continuous power, and with the airplane in the configuration prescribed by paragraph (b) of this section. (e) Lateral control; all engines operating. With the engines operating, roll response must allow normal maneuvers (such as recovery from upsets produced by gusts and the initiation of evasive maneuvers). There must be enough excess lateral control in sideslips (up to sideslip angles that might be required in normal operation), to allow a limited amount of maneuvering and to correct for gusts. Lateral control must be enough at any speed up to VFC/MFC to provide a peak roll rate necessary for safety, without excessive control forces or travel. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-42, 43 FR 2321, Jan. 16, 1978; Amdt. 25-72, 55 FR 29774, July 20, 1990] Sec. 25.149 Minimum control speed. (a) In establishing the minimum control speeds required by this section, the method used to simulate critical engine failure must represent the most critical mode of powerplant failure with respect to controllability expected in service. (b) VMC is the calibrated airspeed at which, when the critical engine is suddenly made inoperative, it is possible to maintain control of the airplane with that engine still inoperative and maintain straight flight with an angle of bank of not more than 5 degrees. (c) VMC may not exceed 1.2 VS with-- (1) Maximum available takeoff power or thrust on the engines; (2) The most unfavorable center of gravity; (3) The airplane trimmed for takeoff; (4) The maximum sea level takeoff weight (or any lesser weight necessary to show VMC); (5) The airplane in the most critical takeoff configuration existing along the flight path after the airplane becomes airborne, except with the landing gear retracted; (6) The airplane airborne and the ground effect negligible; and (7) If applicable, the propeller of the inoperative engine-- (i) Windmilling; (ii) In the most probable position for the specific design of the propeller control; or (iii) Feathered, if the airplane has an automatic feathering device acceptable for showing compliance with the climb requirements of Sec. 25.121. (d) The rudder forces required to maintain control at VMC may not exceed 150 pounds nor may it be necessary to reduce power or thrust of the operative engines. During recovery, the airplane may not assume any dangerous attitude or require exceptional piloting skill, alertness, or strength to prevent a heading change of more than 20 degrees. (e) VMCG, the minimum control speed on the ground, is the calibrated airspeed during the takeoff run at which, when the critical engine is suddenly made inoperative, it is possible to maintain control of the airplane using the rudder control alone (without the use of nosewheel steering), as limited by 150 pounds of force, and the lateral control to the extent of keeping the wings level to enable the takeoff to be safely continued using normal piloting skill. In the determination of VMCG, assuming that the path of the airplane accelerating with all engines operating is along the centerline of the runway, its path from the point at which the critical engine is made inoperative to the point at which recovery to a direction parallel to the centerline is completed may not deviate more than 30 feet laterally from the centerline at any point. VMCG must be established with- (1) The airplane in each takeoff configuration or, at the option of the applicant, in the most critical takeoff configuration; (2) Maximum available takeoff power or thrust on the operating engines; (3) The most unfavorable center of gravity; (4) The airplane trimmed for takeoff; and (5) The most unfavorable weight in the range of takeoff weights. (f) VMCL, the minimum control speed during approach and landing with all engines operating, is the calibrated airspeed at which, when the critical engine is suddenly made inoperative, it is possible to maintain control of the airplane with that engine still inoperative, and maintain straight flight with an angle of bank of not more than 5 degrees. VMCL must be established with-- (1) The airplane in the most critical configuration (or, at the option of the applicant, each configuration) for approach and landing with all engines operating; (2) The most unfavorable center of gravity; (3) The airplane trimmed for approach with all engines operating; (4) The most favorable weight, or, at the option of the applicant, as a function of weight; (5) For propeller airplanes, the propeller of the inoperative engine in the position it achieves without pilot action, assuming the engine fails while at the power or thrust necessary to maintain a three degree approach path angle; and (6) Go-around power or thrust setting on the operating engine(s). (g) For airplanes with three or more engines, VMCL-2, the minimum control speed during approach and landing with one critical engine inoperative, is the calibrated airspeed at which, when a second critical engine is suddenly made inoperative, it is possible to maintain control of the airplane with both engines still inoperative, and maintain straight flight with an angle of bank of not more than 5 degrees. VMCL-2 must be established with-- (1) The airplane in the most critical configuration (or, at the option of the applicant, each configuration) for approach and landing with one critical engine inoperative; (2) The most unfavorable center of gravity; (3) The airplane trimmed for approach with one critical engine inoperative; (4) The most unfavorable weight, or, at the option of the applicant, as a function of weight; (5) For propeller airplanes, the propeller of the more critical inoperative engine in the position it achieves without pilot action, assuming the engine fails while at the power or thrust necessary to maintain a three degree approach path angle, and the propeller of the other inoperative engine feathered; (6) The power or thrust on the operating engine(s) necessary to maintain an approach path angle of three degrees when one critical engine is inoperative; and (7) The power or thrust on the operating engine(s) rapidly changed, immediately after the second critical engine is made inoperative, from the power or thrust prescribed in paragraph (g)(6) of this section to-- (i) Minimum power or thrust; and (ii) Go-around power or thrust setting. (h) In demonstrations of VMCL and VMCL-2- (1) The rudder force may not exceed 150 pounds; (2) The airplane may not exhibit hazardous flight characteristics or require exceptional piloting skill, alertness, or strength; (3) Lateral control must be sufficient to roll the airplane, from an initial condition of steady flight, through an angle of 20 degrees in the direction necessary to initiate a turn away from the inoperative engine(s), in not more than 5 seconds; and (4) For propeller airplanes, hazardous flight characteristics must not be exhibited due to any propeller position achieved when the engine fails or during any likely subsequent movements of the engine or propeller controls. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-42, 43 FR 2321, Jan. 16, 1978; Amdt.
25-72, 55 FR 29774, July 20, 1990; 55 FR 37607, Sept. 12,
1990; Amdt. 25-84, 60 FR 30749, June 9, 1995] |
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(a) General. Each airplane must meet the trim requirements of this section after being trimmed, and without further pressure upon, or movement of, either the primary controls or their corresponding trim controls by the pilot or the automatic pilot. (b) Lateral and directional trim. The airplane must maintain lateral and directional trim with the most adverse lateral displacement of the center of gravity within the relevant operating limitations, during normally expected conditions of operation (including operation at any speed from 1.4 VS1 to VMO/MMO). (c) Longitudinal trim. The airplane must maintain longitudinal trim during-- (1) A climb with maximum continuous power at a speed not more than 1.4 VS1, with the landing gear retracted, and the flaps (i) retracted and (ii) in the takeoff position; (2) A glide with power off at a speed not more than 1.4 VS1, with the landing gear extended, the wing flaps (i) retracted and (ii) extended, the most unfavorable center of gravity position approved for landing with the maximum landing weight, and with the most unfavorable center of gravity position approved for landing regardless of weight; and (3) Level flight at any speed from 1.4 VS1, to VMO/MMO, with the landing gear and flaps retracted, and from 1.4 VS1 to VLE with the landing gear extended. (d) Longitudinal, directional, and lateral trim. The airplane must maintain longitudinal, directional, and lateral trim (and for the lateral trim, the angle of bank may not exceed five degrees) at 1.4 VS1 during climbing flight with-- (1) The critical engine inoperative; (2) The remaining engines at maximum continuous power; and (3) The landing gear and flaps retracted. (e) Airplanes with four or more engines. Each airplane with four or more engines must maintain trim in rectilinear flight- (1) At the climb speed, configuration, and power required by Sec. 25.123(a) for the purpose of establishing the rate of climb; (2) With the most unfavorable center of gravity position; and (3) At the weight at which the two-engine-inoperative climb is equal to at least 0.013 VS02 at an altitude of 5,000 feet. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-23, 35 FR 5671, Apr. 8, 1970; Amdt.
25-38, 41 FR 55466, Dec. 20, 1976] |
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The airplane must be longitudinally, directionally, and laterally stable in accordance with the provisions of Secs. 25.173 through 25.177. In addition, suitable stability and control feel (static stability) is required in any condition normally encountered in service, if flight tests show it is necessary for safe operation. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-7, 30 FR 13117, Oct. 15, 1965] Sec. 25.173 Static longitudinal stability. Under the conditions specified in Sec. 25.175, the characteristics of the elevator control forces (including friction) must be as follows: (a) A pull must be required to obtain and maintain speeds below the specified trim speed, and a push must be required to obtain and maintain speeds above the specified trim speed. This must be shown at any speed that can be obtained except speeds higher than the landing gear or wing flap operating limit speeds or VFC/MFC, whichever is appropriate, or lower than the minimum speed for steady unstalled flight. (b) The airspeed must return to within 10 percent of the original trim speed for the climb, approach, and landing conditions specified in Sec. 25.175 (a), (c), and (d), and must return to within 7.5 percent of the original trim speed for the cruising condition specified in Sec. 25.175(b), when the control force is slowly released from any speed within the range specified in paragraph (a) of this section. (c) The average gradient of the stable slope of the stick force versus speed curve may not be less than 1 pound for each 6 knots. (d) Within the free return speed range specified in paragraph (b) of this section, it is permissible for the airplane, without control forces, to stabilize on speeds above or below the desired trim speeds if exceptional attention on the part of the pilot is not required to return to and maintain the desired trim speed and altitude. [Amdt. 25-7, 30 FR 13117, Oct. 15, 1965] Sec. 25.175 Demonstration of static longitudinal stability. Static longitudinal stability must be shown as follows: (a) Climb. The stick force curve must have a stable slope at speeds between 85 and 115 percent of the speed at which the airplane-- (1) Is trimmed, with-- (i) Wing flaps retracted; (ii) Landing gear retracted; (iii) Maximum takeoff weight; and (iv) 75 percent of maximum continuous power for reciprocating engines or the maximum power or thrust selected by the applicant as an operating limitation for use during climb for turbine engines; and (2) Is trimmed at the speed for best rate-of-climb except that the speed need not be less than 1.4 VS1. (b) Cruise. Static longitudinal stability must be shown in the cruise condition as follows: (1) With the landing gear retracted at high speed, the stick force curve must have a stable slope at all speeds within a range which is the greater of 15 percent of the trim speed plus the resulting free return speed range, or 50 knots plus the resulting free return speed range, above and below the trim speed (except that the speed range need not include speeds less than 1.4 VS1, nor speeds greater than VFC/MFC, nor speeds that require a stick force of more than 50 pounds), with-- (i) The wing flaps retracted; (ii) The center of gravity in the most adverse position (see Sec. 25.27); (iii) The most critical weight between the maximum takeoff and maximum landing weights; (iv) 75 percent of maximum continuous power for reciprocating engines or for turbine engines, the maximum cruising power selected by the applicant as an operating limitation (see Sec. 25.1521), except that the power need not exceed that required at VMO/MMO; and (v) The airplane trimmed for level flight with the power required in paragraph (b)(1)(iv) of this section. (2) With the landing gear retracted at low speed, the stick force curve must have a stable slope at all speeds within a range which is the greater of 15 percent of the trim speed plus the resulting free return speed range, or 50 knots plus the resulting free return speed range, above and below the trim speed (except that the speed range need not include speeds less than 1.4 VS1, nor speeds greater than the minimum speed of the applicable speed range prescribed in paragraph (b)(1), nor speeds that require a stick force of more than 50 pounds), with-- (i) Wing flaps, center of gravity position, and weight as specified in paragraph (b)(1) of this section; (ii) Power required for level flight at a speed equal to VMO + 1.4 VS1/2; and (iii) The airplane trimmed for level flight with the power required in paragraph (b)(2)(ii) of this section. (3) With the landing gear extended, the stick force curve must have a stable slope at all speeds within a range which is the greater of 15 percent of the trim speed plus the resulting free return speed range, or 50 knots plus the resulting free return speed range, above and below the trim speed (except that the speed range need not include speeds less than 1.4 VS1, nor speeds greater than VLE, nor speeds that require a stick force of more than 50 pounds), with-- (i) Wing flap, center of gravity position, and weight as specified in paragraph (b)(1) of this section; (ii) 75 percent of maximum continuous power for reciprocating engines or, for turbine engines, the maximum cruising power selected by the applicant as an operating limitation, except that the power need not exceed that required for level flight at VLE; and (iii) The aircraft trimmed for level flight with the power required in paragraph (b)(3)(ii) of this section. (c) Approach. The stick force curve must have a stable slope at speeds between 1.1 VS1 and 1.8 VS1, with-- (1) Wing flaps in the approach position; (2) Landing gear retracted; (3) Maximum landing weight; and (4) The airplane trimmed at 1.4 VS1 with enough power to maintain level flight at this speed. (d) Landing. The stick force curve must have a stable slope, and the stick force may not exceed 80 pounds, at speeds between 1.1 VS0 and 1.3 VS0 with- (1) Wing flaps in the landing position; (2) Landing gear extended; (3) Maximum landing weight; (4) Power or thrust off on the engines; and (5) The airplane trimmed at 1.4 VS0 with power or thrust off. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-7, 30 FR 13117, Oct. 15, 1965] Sec. 25.177 Static lateral-directional stability. (a) [Reserved] (b) [Reserved] (c) In straight, steady sideslips, the aileron and rudder control movements and forces must be substantially proportional to the angle of sideslip in a stable sense; and the factor of proportionality must lie between limits found necessary for safe operation throughout the range of sideslip angles appropriate to the operation of the airplane. At greater angles, up to the angle at which full rudder is used or a rudder force of 180 pounds is obtained, the rudder pedal forces may not reverse; and increased rudder deflection must be needed for increased angles of sideslip. Compliance with this paragraph must be demonstrated for all landing gear and flap positions and symmetrical power conditions at speeds from 1.2 VS1 to VFE, VLE, or VFC/ MFC, as appropriate. (d) The rudder gradients must meet the requirements of paragraph (c) at speeds between VMO/MMO and VFC/MFC except that the dihedral effect (aileron deflection opposite the corresponding rudder input) may be negative provided the divergence is gradual, easily recognized, and easily controlled by the pilot. [Doc. No. 24344, Amdt. 25-72, 55 FR 29774, July 20, 1990; 55 FR 37607, Sept. 12, 1990] Sec. 25.181 Dynamic stability. (a) Any short period oscillation, not including combined lateral directional oscillations, occurring between 1.2 VS and maximum allowable speed appropriate to the configuration of the airplane must be heavily damped with the primary controls-- (1) Free; and (2) In a fixed position. (b) Any combined lateral-directional oscillations ("Dutch roll") occurring between 1.2 VS and maximum allowable speed appropriate to the configuration of the airplane must be positively damped with controls free, and must be controllable with normal use of the primary controls without requiring exceptional pilot skill. [Amdt. 25-42, 43 FR 2322, Jan. 16, 1978, as amended
by Amdt. 25-72, 55 FR 29775, July 20, 1990; 55 FR 37607,
Sept. 12, 1990] |
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(a) Stalls must be shown in straight flight and in 30 degree banked turns with-- (1) Power off; and (2) The power necessary to maintain level flight at 1.6 VS1 (where VS1 corresponds to the stalling speed with flaps in the approach position, the landing gear retracted, and maximum landing weight). (b) In each condition required by paragraph (a) of this section, it must be possible to meet the applicable requirements of Sec. 25.203 with-- (1) Flaps, landing gear, and deceleration devices in any likely combination of positions approved for operation; (2) Representative weights within the range for which certification is requested; (3) The most adverse center of gravity for recovery; and (4) The airplane trimmed for straight flight at the speed prescribed in Sec. 25.103(b)(1). (c) The following procedures must be used to show compliance with Sec. 25.203; (1) Starting at a speed sufficiently above the stalling speed to ensure that a steady rate of speed reduction can be established, apply the longitudinal control so that the speed reduction does not exceed one knot per second until the airplane is stalled. (2) In addition, for turning flight stalls, apply the longitudinal control to achieve airspeed deceleration rates up to 3 knots per second. (3) As soon as the airplane is stalled, recover by normal recovery techniques. (d) The airplane is considered stalled when the behavior of the airplane gives the pilot a clear and distinctive indication of an acceptable nature that the airplane is stalled. Acceptable indications of a stall, occurring either individually or in combination, are-- (1) A nose-down pitch that cannot be readily arrested; (2) Buffeting, of a magnitude and severity that is a strong and effective deterrent to further speed reduction; or (3) The pitch control reaches the aft stop and no further increase in pitch attitude occurs when the control is held full aft for a short time before recovery is initiated. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-38, 41 FR 55466, Dec. 20, 1976; Amdt. 25-42, 43 FR 2322, Jan. 16, 1978; Amdt. 25-84, 60 FR 30750, June 9, 1995] Sec. 25.203 Stall characteristics. (a) It must be possible to produce and to correct roll and yaw by unreversed use of the aileron and rudder controls, up to the time the airplane is stalled. No abnormal nose-up pitching may occur. The longitudinal control force must be positive up to and throughout the stall. In addition, it must be possible to promptly prevent stalling and to recover from a stall by normal use of the controls. (b) Maximum speed for stability characteristics, VFC/MFC. VFC/MFC is the maximum speed at which the requirements of Secs. 25.143(f), 25.147(e), 25.175(b)(1), 25.177, and 25.181 must be met with flaps and landing gear retracted. It may not be less than a speed midway between VMO/MMO and VDF/ MDF, except that for altitudes where Mach number is the limiting factor, MFC need not exceed the Mach number at which effective speed warning occurs. (c) For turning flight stalls, the action of the airplane after the stall may not be so violent or extreme as to make it difficult, with normal piloting skill, to effect a prompt recovery and to regain control of the airplane. The maximum bank angle that occurs during the recovery may not exceed-- (1) Approximately 60 degrees in the original direction of the turn, or 30 degrees in the opposite direction, for deceleration rates up to 1 knot per second; and (2) Approximately 90 degrees in the original direction of the turn, or 60 degrees in the opposite direction, for deceleration rates in excess of 1 knot per second. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-84, 60 FR 30750, June 9, 1995] Sec. 25.205 [Removed. Amdt. 25-72, 55 FR 29775, July 20, 1990] EDITORIAL NOTE: For the convenience of the user, the removed text is set out below. Sec. 25.205 Stalls: Critical engine inoperative. (a) It must be possible to safely recover from a stall with the critical engine inoperative-- (1) Without applying power to the inoperative engine; (2) With flaps and landing gear retracted; and (3) With the remaining engines at up to 75 percent of maximum continuous power, or up to the power at which the wings can be held level with the use of maximum control travel, whichever is less. (b) The operating engines may be throttled back during stall recovery from stalls with the critical engine inoperative. Sec. 25.207 Stall warning. (a) Stall warning with sufficient margin to prevent inadvertent stalling with the flaps and landing gear in any normal position must be clear and distinctive to the pilot in straight and turning flight. (b) The warning may be furnished either through the inherent aerodynamic qualities of the airplane or by a device that will give clearly distinguishable indications under expected conditions of flight. However, a visual stall warning device that requires the attention of the crew within the cockpit is not acceptable by itself. If a warning device is used, it must provide a warning in each of the airplane configuations prescribed in paragraph (a) of this section at the speed prescribed in paragraph (c) of this section. (c) The stall warning must begin at a speed exceeding the stalling speed (i.e., the speed at which the airplane stalls or the minimum speed demonstrated, whichever is applicable under the provisions of Sec. 25.201(d)) by seven percent or at any lesser margin if the stall warning has enough clarity, duration, distinctiveness, or similar properties. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-7, 30 FR 13118, Oct. 15, 1965; Amdt.
25-42, 43 FR 2322, Jan. 16, 1978] |
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(a) Landplanes may have no uncontrollable tendency to nose over in any reasonably expected operating condition or when rebound occurs during landing or takeoff. In addition-- (1) Wheel brakes must operate smoothly and may not cause any undue tendency to nose over; and (2) If a tail-wheel landing gear is used, it must be possible, during the takeoff ground run on concrete, to maintain any altitude up to thrust line level, at 80 percent of VS1. (b) For seaplanes and amphibians, the most adverse water conditions safe for takeoff, taxiing, and landing, must be established. Sec. 25.233 Directional stability and control. (a) There may be no uncontrollable ground-looping tendency in 90 deg. cross winds, up to a wind velocity of 20 knots or 0.2 VS0, whichever is greater, except that the wind velocity need not exceed 25 knots. At any speed at which the airplane may be expected to be operated on the ground. This may be shown while establishing the 90 deg. cross component of wind velocity required by Sec. 25.237. (b) Landplanes must be satisfactorily controllable, without exceptional piloting skill or alertness, in power-off landings at normal landing speed, without using brakes or engine power to maintain a straight path. This may be shown during power-off landings made in conjunction with other tests. (c) The airplane must have adequate directional control during taxiing. This may be shown during taxiing prior to takeoffs made in conjunction with other tests. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-23, 35 FR 5671, Apr. 8, 1970; Amdt. 25-42, 43 FR 2322, Jan. 16, 1978] Sec. 25.235 Taxiing condition. The shock absorbing mechanism may not damage the structure of the airplane when the airplane is taxied on the roughest ground that may reasonably be expected in normal operation. Sec. 25.237 Wind velocities. (a) For landplanes and amphibians, a 90-degree cross component of wind velocity, demonstrated to be safe for takeoff and landing, must be established for dry runways and must be at least 20 knots or 0.2 VS0, whichever is greater, except that it need not exceed 25 knots. (b) For seaplanes and amphibians, the following applies: (1) A 90-degree cross component of wind velocity, up to which takeoff and landing is safe under all water conditions that may reasonably be expected in normal operation, must be established and must be at least 20 knots or 0.2 Vs0, whichever is greater, except that it need not exceed 25 knots. (2) A wind velocity, for which taxiing is safe in any direction under all water conditions that may reasonably be expected in normal operation, must be established and must be at least 20 knots or 0.2 VS0, whichever is greater, except that it need not exceed 25 knots. [Amdt. 25-42, 43 FR 2322, Jan. 16, 1978] Sec. 25.239 Spray characteristics, control, and stability on water. (a) For seaplanes and amphibians, during takeoff, taxiing, and landing, and in the conditions set forth in paragraph (b) of this section, there may be no-- (1) Spray characteristics that would impair the pilot's view, cause damage, or result in the taking in of an undue quantity of water; (2) Dangerously uncontrollable porpoising, bounding, or swinging tendency; or (3) Immersion of auxiliary floats or sponsons, wing tips, propeller blades, or other parts not designed to withstand the resulting water loads. (b) Compliance with the requirements of paragraph (a) of this section must be shown-- (1) In water conditions, from smooth to the most adverse condition established in accordance with Sec. 25.231; (2) In wind and cross-wind velocities, water currents, and associated waves and swells that may reasonably be expected in operation on water; (3) At speeds that may reasonably be expected in operation on water; (4) With sudden failure of the critical engine at any time while on water; and (5) At each weight and center of gravity position, relevant to each operating condition, within the range of loading conditions for which certification is requested. (c) In the water conditions of paragraph (b) of this
section, and in the corresponding wind conditions, the
seaplane or amphibian must be able to drift for five minutes
with engines inoperative, aided, if necessary, by a sea
anchor. |
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(a) The airplane must be demonstrated in flight to be free from any vibration and buffeting that would prevent continued safe flight in any likely operating condition. (b) Each part of the airplane must be demonstrated in flight to be free from excessive vibration under any appropriate speed and power conditions up to VDF/MDF. The maximum speeds shown must be used in establishing the operating limitations of the airplane in accordance with Sec. 25.1505. (c) Except as provided in paragraph (d) of this section, there may be no buffeting condition, in normal flight, including configuration changes during cruise, severe enough to interfere with the control of the airplane, to cause excessive fatigue to the crew, or to cause structural damage. Stall warning buffeting within these limits is allowable. (d) There may be no perceptible buffeting condition in the cruise configuration in straight flight at any speed up to VMO/MMO, except that stall warning buffeting is allowable. (e) For an airplane with MD greater than .6 or with a maximum operating altitude greater than 25,000 feet, the positive maneuvering load factors at which the onset of perceptible buffeting occurs must be determined with the airplane in the cruise configuration for the ranges of airspeed or Mach number, weight, and altitude for which the airplane is to be certificated. The envelopes of load factor, speed, altitude, and weight must provide a sufficient range of speeds and load factors for normal operations. Probable inadvertent excursions beyond the boundaries of the buffet onset envelopes may not result in unsafe conditions. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-23, 35 FR 5671, Apr. 8, 1970; Amdt. 25-72, 55 FR 29775, July 20, 1990; Amdt. 25-77, 57 FR 28949, June 29, 1992] Sec. 25.253 High-speed characteristics. (a) Speed increase and recovery characteristics. The following speed increase and recovery characteristics must be met: (1) Operating conditions and characteristics likely to cause inadvertent speed increases (including upsets in pitch and roll) must be simulated with the airplane trimmed at any likely cruise speed up to VMO/MMO. These conditions and characteristics include gust upsets, inadvertent control movements, low stick force gradient in relation to control friction, passenger movement, leveling off from climb, and descent from Mach to airspeed limit altitudes. (2) Allowing for pilot reaction time after effective inherent or artificial speed warning occurs, it must be shown that the airplane can be recovered to anormal attitude and its speed reduced to VMO/MMO, without- (i) Exceptional piloting strength or skill; (ii) Exceeding VD/MD, VDF/MDF, or the structural limitations; and (iii) Buffeting that would impair the pilot's ability to read the instruments or control the airplane for recovery. (3) With the airplane trimmed at any speed up to VMO /MMO, there must be no reversal of the response to control input about any axis at any speed up to VDF/MDF. Any tendency to pitch, roll, or yaw must be mild and readily controllable, using normal piloting techniques. When the airplane is trimmed at VMO/MMO, the slope of the elevator control force versus speed curve need not be stable at speeds greater than VFC/MFC, but there must be a push force at all speeds up to VDF/MDF and there must be no sudden or excessive reduction of elevator control force as VDF/MDF is reached. (b) Maximum speed for stability characteristics, VFC/MFC. VFC/MFC is the maximum speed at which the requirements of Secs. 25.143(f), 25.147(e), 25.175(b)(1), 25.177, and 25.181 must be met with flaps and landing gear retracted. It may not be less than a speed midway between VMO/MMO and VDF/ MDF, except that for altitudes where Mach number is the limiting factor, MFC need not exceed the Mach number at which effective speed warning occurs. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-23, 35 FR 5671, Apr. 8, 1970; Amdt. 25-54, 45 FR 60172, Sept. 11, 1980; Amdt. 25-72, 55 FR 29775, July 20, 1990; Amdt. 25-84, 60 FR 30750, June 9, 1995] Sec. 25.255 Out-of-trim characteristics. (a) From an initial condition with the airplane trimmed at cruise speeds up to VMO/MMO, the airplane must have satisfactory maneuvering stability and controllability with the degree of out-of-trim in both the airplane nose-up and nose-down directions, which results from the greater of-- (1) A three-second movement of the longitudinal trim system at its normal rate for the particular flight condition with no aerodynamic load (or an equivalent degree of trim for airplanes that do not have a power-operated trim system), except as limited by stops in the trim system, including those required by Sec. 25.655(b) for adjustable stabilizers; or (2) The maximum mistrim that can be sustained by the autopilot while maintaining level flight in the high speed cruising condition. (b) In the out-of-trim condition specified in paragraph (a) of this section, when the normal acceleration is varied from +1 g to the positive and negative values specified in paragraph (c) of this section-- (1) The stick force vs. g curve must have a positive slope at any speed up to and including VFC/MFC; and (2) At speeds between VFC/MFC and VDF/MDF the direction of the primary longitudinal control force may not reverse. (c) Except as provided in paragraphs (d) and (e) of this section, compliance with the provisions of paragraph (a) of this section must be demonstrated in flight over the acceleration range-- (1) -1 g to +2.5 g; or (2) 0 g to 2.0 g, and extrapolating by an acceptable method to -1 g and +2.5 g. (d) If the procedure set forth in paragraph (c)(2) of this section is used to demonstrate compliance and marginal conditions exist during flight test with regard to reversal of primary longitudinal control force, flight tests must be accomplished from the normal acceleration at which a marginal condition is found to exist to the applicable limit specified in paragraph (b)(1) of this section. (e) During flight tests required by paragraph (a) of this section, the limit maneuvering load factors prescribed in Secs. 25.333(b) and 25.337, and the maneuvering load factors associated with probable inadvertent excursions beyond the boundaries of the buffet onset envelopes determined under Sec. 25.251(e), need not be exceeded. In addition, the entry speeds for flight test demonstrations at normal acceleration values less than 1 g must be limited to the extent necessary to accomplish a recovery without exceeding VDF/MDF. (f) In the out-of-trim condition specified in paragraph (a) of this section, it must be possible from an overspeed condition at VDF/MDF to produce at least 1.5 g for recovery by applying not more than 125 pounds of longitudinal control force using either the primary longitudinal control alone or the primary longitudinal control and the longitudinal trim system. If the longitudinal trim is used to assist in producing the required load factor, it must be shown at VDF/MDF that the longitudinal trim can be actuated in the airplane nose-up direction with the primary surface loaded to correspond to the least of the following airplane nose-up control forces: (1) The maximum control forces expected in service as specified in Secs. 25.301 and 25.397. (2) The control force required to produce 1.5 g. (3) The control force corresponding to buffeting or other phenomena of such intensity that it is a strong deterrent to further application of primary longitudinal control force. [Amdt. No. 25-42, 43 FR 2322, Jan. 16, 1978] |
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