2.303 2.304 2.31 2.311 2.3111 2. 3112 2. 3113 2. 3114 2. 312 2. 3121 2.3122 strength under reasonable service conditions. When a fabrication process requires close control to attain this objective, the process shall be performed in accordance with a process specification. Protection. All members of the primary structure shall be suitably protected against deterioration or loss of strength in service due to weathering corrosion, abrasion, or other causes. In seaplanes special precautions shall be taken against corrosion from salt water, particularly where parts made from different metals are in close proximity. Adequate provisions for ventilation and drainage shall be made. Inspection Provisions. Adequate means shall be provided to permit the examination of such parts of the airplane as require periodic inspection. Major Components Wings Proof of Strength. The strength of stressed-skin wings shall be substantiated by load tests or by combined structural analysis and tests. External Bracing. When wires are used for external lift bracing, the structure shall be designed to develop at least one half the required load factor, with any one wire cut. Rigging loads shall be taken into account in a rational or conservative manner. When brace struts of large fineness ratio are used, the aerodynamic forces on such struts shall be taken into account. Ribs. The strength of ribs shall be proved by test to at least 125 percent of the ultimate loads for the most severe loading conditions, unless a rational analysis and test procedure is employed. The load shall be suitably distributed between upper and lower wing surfaces unless a more severe distribution is used. The effects of ailerons and high-lift devices shall be properly accounted for. Rib tests shall simulate conditions in the airplane with respect to torsional rigidity of spars, fixity conditions, lateral support and attachment to spars. Covering. Proof of strength of fabric covering is not required when standard grades of cloth and methods of attaching and doping are employed, provided however, that special tests may be required when it appears necessary to account for the effects of unusually high design airspeeds or slipstream velocities or similar factors. Control Surfaces (Fixed and Movable) Proof of Strength. Limit load tests are required to prove compliance with limit load requirements. Control surface tests shall include the horn or fitting to which the control system is attached. Analysis or individual load tests shall be conducted to demonstrate compliance with the multiplying factor of safety requirements for control surface hinges. Rigging loads due to wire bracing shall be taken into account in a rational or conservative manner. Installation. Movable tail surfaces shall be so installed that there is no interference between the surfaces or their 627038-45- -14 2. 3123 2. 313 2. 3130 2. 3131 2. 3132 2.3133 bracing when any one is held in its extreme position and any other is operated through its full angular movement. Hinges. Hinges of the strap type bearing directly on torque tubes are permissible only in the case of steel torque tubes which have a multiplying factor of safety at the hinge point of not less than 1.5. Control surface hinges, excepting ball and roller bearings, shall incorporate a multiplying factor of safety of not less than 6.67 with respect to the ultimate bearing strength of the softest material used as a bearing. Hinges incorporating ball or roller bearings shall be designed to not exceed the manufacturer's non-Brinell rating at limit load. Control Systems General. All controls shall operate with sufficient ease, smoothness and positiveness to permit the proper performance of their function and shall be so located and identified as to provide the greatest possible convenience in operation and the least possibility of confusion and consequent inadvertent operation. Wherever possible, the sense of motion involved in the operation of the control shall correspond with the sense of the effect of the operation upon the airplane or the part operated, or failing this, shall suggest it. Primary Flight Controls. The primary flight controls shall consist of a control stick directly in front of each pilot or a column providing a grip or wheel in that position, and, when the rudder is independently controlled, a pair of foot pedals or a rudder bar for each pilot. The primary controls shall operate as follows: (a) A rearward displacement of the top of the stick, grip, or wheel shall cause the airplane to pitch nose up. (b) A displacement of the stick or grip toward the right or a right hand rotational displacement of the wheel shall be required to bank the airplane right wing down. (c) A forward displacement of the right hand rudder pedal shall be required to turn the airplane to the right. Trimming Controls. The trimming controls shall be conveniently grouped and each shall operate in the plane and with the sense of the motion of the airplane which their operation is intended to produce. Proper precautions shall be taken against the possibility of inadvertent or abrupt tab operation. Means shall be provided to indicate to the pilot the range of adjustment and the direction of motion. Tab controls shall be irreversible, nonflexible and extremely rugged, unless the tab is properly balanced about its hinge line. Trimming devices shall be capable of continued normal operation in spite of the failure of any one connecting or transmitting element in the primary flight control system. Wing Flap Controls. Wing flap controls shall be so oriented and shall operate in such manner as to require an upward motion of the control to retract the flaps. The controls shall maintain, without assistance from the crew, 2. 3133 -T 2. 3135 2. 3136 2. 3137 2. 3138 any desired flap position. Means shall be provided to indicate the flap position to the pilot. The flap-operating mechanism shall be such as to prevent sudden inadvertent or automatic opening of the flap at speeds above the design speeds of the extended flap conditions. The time required to extend fully or to retract flaps shall not be less than 15 seconds unless it can be demonstrated that the operation of the flaps in a lesser time does not result in unsatisfactory flight characteristics. For transport category airplanes, the flap control shall provide means for bringing the flaps from any position within the operating range to any one of three positions, designated hereinafter as landing, approach, and take-off positions, or to the fully retracted position, by placing the primary flap control in a single setting marked as corresponding to each such flap position, the flaps thereupon moving directly to the desired position without requiring further attention. If any extension of the flaps beyond the landing position is possible, the flap control shall be clearly marked to identify such range of extension. The landing position, approach position, and take-off position, or any of them, may be made variable with altitude or weight by means of a secondary flap control provided for that purpose. Such a secondary control, if provided, shall operate independently of the primary control and in such manner that when it has been adjusted (for the effect of weight or altitude), the necessary flap position can thereafter be obtained by placing the primary flap control in the desired position. The secondary control shall be so designed and marked as to be readily operable by the crew. The rate of flap retraction shall be such as to permit compliance with 2.131 (b). Operation Test. An operation test shall be conducted by operating the controls from the pilot's compartment with the entire system so loaded as to correspond to the minimum limit control force specified for the control system in question. In this test there shall be no jamming, excessive friction, or excessive deflection. Installation. All control systems and operating devices. shall be so designed and installed as to prevent jamming, chafing, interference by cargo, passengers or loose objects, and the slapping of cables or tubes against parts of the airplane. All pulleys shall be provided with satisfactory guards. Stops. All control systems shall be provided with stops which positively limit the range of motion of the control surfaces. Stops shall be capable of withstanding the loads corresponding to the design conditions for the control system and shall minimize deflection of the surfaces or the controls beyond their design limits. Power Operated Flight Controls. When a power device is used for operating the primary flight controls provisions shall be made for retaining sufficient control for steady flight and landing after failure of any single part of the system, 2. 3139 2. 314 2. 3141 2. 3142 2. 31420 2. 31421 2. 31422 excluding failures in mechanical parts of the system comparable to equivalent parts of manually operated systems. (NOTE: One way of meeting this requirement would be to insure that the pilot has sufficient manual control after failure of the power system. Another way would be to provide at least two entirely independent power systems.) Provision shall be made for all foreseeable kinds of failure so as to insure that any control circuits rendered inoperative and/or inoperable by the failed power system can quickly be put into a position for safe flight at moderate speeds. These requirements shall be met under the conditions of failure of all engines in single and twin-engined airplanes, and of any two engines in other multiengined airplanes. Control System Locks. When a device is provided for locking a control surface while the aircraft is on the ground or water, compliance with the following requirements shall be shown: (a) The locking device shall be so installed as to prevent taxiing the aircraft from taking off while the lock is engaged. (b) Means shall be provided to preclude the possibility of any lock becoming engaged during flights. Landing Gear Shock Absorption. Main, nose, and tail wheel units shall incorporate shock absorbing elements whose adequacy is demonstrated by the tests specified in Section 2.2411. In addition, the shock absorbing ability of the landing gear in taxiing must be demonstrated in the operational test of 2.143. Retracting Mechanism and Supports. The structure supporting the landing gear in its retracted position shall be designed for the maximum load factors in the flight conditions. The retracting mechanism and supporting structure shall be designed for the combination of friction, inertia, brake torque, and air-drag loads occurring during retraction at any airspeed and load factor up to those specified for the flaps extended condition, 2.212. Means shall be provided for the purpose of maintaining the wheels in the extended position. Emergency Operation. When other than manual operation of the landing gear is employed, an auxiliary means of extending the landing gear shall be provided. Operation Test. Proper functioning of the landing gear retracting mechanism under the specified limit retracting loads shall be demonstrated by operation tests. Position Indicator and Warning Device. When retractable landing wheels are used, visual means shall be provided for indicating to the pilot, at all times, the position of each of the wheels. In addition, landplanes shall be provided with an aural warning device which shall function continuously, when the engine is throttled preparatory to landing, until extension is completed and the gear is locked. For other than transport category airplanes, any other equally 2. 31423 effective warning device may be substituted in lieu of an aural device. Retraction Control. The control provided for retractable -T gears shall be so oriented and shall operate in such a manner as to require an upward motion of the control to retract the gear. 2.3143 2. 3144 2. 3145 -T 2.315 2. 3151 Wheels. Main landing gear wheels (i. e. those nearest the airplane center of gravity) shall be of an approved type in accordance with Part 5.1. The rated static load of each main wheel shall not be less than the design weight for ground loads (2.240 and 2.240-T) divided by the number of main wheels. Nose wheels shall be approved in accordance with Part 5 for an ultimate radial load not less than the maximum nose wheel ultimate loads obtained in the ground loads requirement, 2.24, and for the corresponding side and burst loads specified in Part 5.1. Tires. A landing gear wheel may be equipped with any type of tire constructed by a reputable maker provided that the rating of the maker is not exceeded. When specially constructed tires are used to support an airplane, the wheels shall be plainly and conspicuously marked to that effect. Such markings shall include the make, size, number of plies and identification marking of the proper tire. Brakes. Transport category airplanes shall be equipped with brakes certificated in accordance with the provisions of Part 5 for the maximum certificated landing weight at sea level and the power-off stalling speed. The brake system for such airplanes shall be so designed and constructed that in the event of a single failure in any connecting or transmitting element in the brake system, (exclusive of the brake operating handle or pedal and the primary braking elements such as the drum and shoe or their equivalent) or the loss of any single source of hydraulic or other brake operating energy supply, it shall be possible, as shown by suitable test or other data, to bring the airplane to rest under the conditions specified in 2.124-T with a mean negative acceleration during the landing roll of at least 50 percent of that obtained in determining the landing distance under that section. Hulls and Floats Buoyancy (Main Seaplane Floats). Main seaplane floats shall have a buoyancy in excess of that required to support the gross weight of the airplane in fresh water as follows: (a) 80 percent in the case of single floats. Main seaplane floats for use on aircraft of 2,500 pounds (1,134 kg.) or more maximum authorized weight shall contain at least five water-tight compartments of approximately equal volume. Main seaplane floats for use on aircraft of less than 2,500 pounds (1,134 kg.) maximum authorized weight shall contain at least four such compartments. |