Avia122 ch13

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• 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.

Semi-monocoque

Airframe Units:

• Fuselage

• Wings

• Stabilizers

• Flight control surfaces

• Landing gear

Airframe Units:

Elevator

HorizontalStabilizer

Rudder

VerticalStabilizer

Aileron

Flap

Cowling

Structural Loads/Stress

• Five Types Of Stress

• Tension• Compression

• Bending force

• Torsion• Shear force

Structural Loads/Stress

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

Materials For Aircraft Construction

Structures

Structures

• Wing Construction Truss-type

Structures

• Stressed-skin Wing Construction

Cantilever Wing

Control Surface 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

Flight Controls

Flight Controls

Pitch Control

• Elevators

• Sole function is to change the angle of attack of the airplane, which alters its speed, lift and drag.

Pitch Control

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.

Lateral Or Roll Control

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.

Directional Control

Trim Controls

Trim Controls

• Trim Tabs

• Balance Tab

• Anti-Servo Tab

• Servo Tab

• Spring Tab

• Adjustable Stabilizer

Trim Tabs

Balance Tab

Anti-Servo Tab

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.

Adjustable Stabilizer

Fixed Trim Tab

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.

Stall Strip and Vortex Generators

Auxiliary Lift Devices

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.

Flaps

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.

Fixed Slot

Movable Slat