takeoff or to slow the aircraft in flight or landings;ailerons that control the roll or bank of the aircraft; andtrim tabs used to aerodynamically unload the controlsurfaces to relieve some of the pilot’s work. On theleading (front) edge of the wing may be found auxiliarylifting devices, resembling flaps, which are used toincrease camber (curvature) of the wing for added lift ontakeoff. Most Navy jet aircraft carry their bomb loads onpylons (called stations) under the wings and, in somecases, under the fuselage. Some jets have missilestations on the sides of the fuselage. Fuel cells arelocated in the wings; additional external tanks can befitted for extra range. Larger jets may have their enginesslung beneath the wings in pods. Some low-wingaircraft have their main landing gear retract into thewings, while the nose wheel retracts into the fuselage.On most high-wing aircraft all gear retracts into thefuselage.EMPENNAGE.—The empennage consists of thestabilizing fins mounted on the tail section of thefuselage. These include the vertical stabilizer on whichis generally mounted the rudder that is used to controlyaw, or direction of the nose about the vertical axis; andthe horizontal stabilizer, on the trailing edge of whichare the elevators that determine the pitch (climb or dive).Some supersonic aircraft may have a full delta wing. Inthat case, there is no horizontal stabilizer and theelevators and ailerons are combined into controlsurfaces called elevons.In aircraft with internally mounted jet engines,exhausts normally are in the tail. High-performance jetshave afterburners that give additional thrust at the costof greatly increased fuel consumption.Rudder, ailerons, and elevators are collectivelygrouped as control surfaces. The “stick” or a similardevice in the cockpit controls these surfaces, while footpedals control the rudder. On high-performanceaircraft, aerodynamic pressures on these surfacesbecome too great for a pilot to overcome manually;hence, all high-speed models today have power-assistedcontrols.Rotary-Wing Aircraft NomenclatureThe aerodynamics of rotary-wing aircraft (fig.8-40) are considerably more complex than those offixed-wing aircraft. A helicopter essentially consists ofa fuselage, main rotor or rotors, and often a tail rotor.FUSELAGE.—As in fixed-wing aircraft, thefuselage contains the cockpit and cabin.M A I N ROTO R . — T h e m a i n r o t o r i s t h eapproximate equivalent of the wing of a fixed-wingaircraft. Each rotor blade is an airfoil, like a wing, andthe lift is generated by the rotation of the assembly,which creates a flow of air over the blades.A helicopter is lifted into the air by the aerodynamicforces on the rotor and not pushed up by the downwash.Some helicopters have twin rotors in tandem at eitherend of the fuselage; but most have a single, main rotorwith a tail rotor mounted at right angles. A few havetandem intermeshing rotors.TAIL ROTOR.—The tail rotor is used fordirectional control and stability. It is mounted at rightangles to the main rotor to counteract the torque of thatsystem. By varying the pitch of the tail rotor blades, thepilot controls yaw.Helicopter engines are connected to the rotorshaft(s) by a transmission, which may be disengaged.That permits the engine(s) to be operated on the groundwithout engaging the rotor system and also permits amode of flight known as autorotation. If the enginesshould stop while in flight, they can be disengaged; thefreewheeling action of the rotor will allow a slowerdescent.8-33Figure 8-39. Fixed-wing aircraft.Student Notes:
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