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Lesson 13: Aircraft Structures And Flight Controls. Aircraft Structures. Truss-type Structures Had struts and wire-braced wings Occupants sat in open cockpits Cockpits fabric-covered Stressed-skin Structures All of the structural loads are carried by the skin. Thin wood skin
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Aircraft Structures • Truss-type Structures • Had struts and wire-braced wings • Occupants sat in open cockpits • Cockpits fabric-covered • Stressed-skin Structures • All of the structural loads are carried by the skin. • Thin wood skin • Or aluminum-alloy sheets
Aircraft Structures • Monocoque • Virtually no internal framework • Semi-monocoque • Internal arrangement of formers and stringers is used to provide additional rigidity and strength to the skin.
Airframe Units: • Fuselage • Wings • Stabilizers • Flight control surfaces • Landing gear
Airframe Units: Vertical Stabilizer Horizontal Stabilizer Rudder Elevator Cowling Flap Aileron
Structural Loads/Stress • Five Types Of Stress • Tension • Compression • Bending force • Torsion • Shear force
Structural Loads/Stress • Deformation • Nonpermanent Deformation • Deformation disappears when the load is removed. • Permanent Deformation • Wrinkles observed on top of wing and bottom of horizontal stabilizer. • Stretch marks on the bottom of the wing or top o the stabilizer. (positive g’s)
Materials For Aircraft Construction • Wood • Aluminum Alloys • Honeycomb • Magnesium • Stainless Steel
Structures • Wing Construction Truss-type
Structures • Stressed-skin Wing Construction
Control Surface Construction • Control Surface Flutter • Control Surface must be mass balanced so that their center of gravity does not fall behind their hinge line.
Fuselage Construction • Truss Fuselage construction • Pratt truss • Warren truss • Stressed-skin Structure • Monocoque • Semi - Monocoque • Pressurized Structure
Pitch Control • Elevators • Sole function is to change the angle of attack of the airplane, which alters its speed, lift and drag.
Pitch Control • Stabilator • All-movable tail • Anti-servo tab • Ruddervators • Provides both longitudinal and directional stabilization and control.
Lateral Or Roll Control • Ailerons • Rolling action produced is the primary method of lateral control on most aircraft.
Directional Control • Adverse aileron yaw • The aileron that moves downward creates lift and induced drag. • Induced drag pulls the nose of the airplane around in the direction opposite the way the airplane should turn.
Directional Control • Rudder • Rotates the airplane about its vertical axis (Yawing) • Also provides a form of roll control because the application of rudder causes yaw which will induce a roll.
Trim Controls • Trim Tabs • Balance Tab • Anti-Servo Tab • Servo Tab • Spring Tab • Adjustable Stabilizer
Servo Tab • Used on large aircraft when the control forces are too great for the pilot to manually move. • Flight control column moves the tab on the control surface and this aerodynamically moves the main control surface.
Aerodynamically Balanced Control Surface • Overhang deflects to the opposite side of the fuselage from the main rudder surface to produce an aerodynamic force that aids the pilot.
Flaps • Change the camber of the wing and increase both its lift and drag for and given angle of attack • Moved by cables form an electric motor driven jackscrew.
Leading Edge Devices • Delays the the airflow separation caused by a stall to a higher angle of attack. • Increases the energy of the air flowing over the surface.