Lesson 13: Aircraft Structures And Flight Controls

Aircraft StructuresTruss-type Structures

Had struts and wire-braced wingsOccupants sat in open cockpitsCockpits fabric-covered

Stressed-skin Structures

All of the structural loads are carried by the skin.Thin wood skinOr aluminum-alloy sheets

Aircraft StructuresMonocoque

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:ElevatorHorizontalStabilizerRudderVerticalStabilizerAileronFlapCowling

Structural Loads/StressFive Types Of Stress

TensionCompressionBending forceTorsionShear force

Structural Loads/Stress

Structural Loads/StressDeformation

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 gs)

Materials For Aircraft ConstructionWood

Aluminum Alloys

Honeycomb

Magnesium

Stainless Steel

Materials For Aircraft Construction

Structures

StructuresWing Construction Truss-type

StructuresStressed-skin Wing Construction

Cantilever Wing

Control Surface Construction

Control Surface ConstructionControl Surface Flutter

Control Surface must be mass balanced so that their center of gravity does not fall behind their hinge line.

Fuselage ConstructionTruss Fuselage construction

Pratt trussWarren trussStressed-skin StructureMonocoqueSemi - Monocoque

Pressurized Structure

Flight Controls

Flight Controls

Pitch ControlElevators

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

Pitch Control

Pitch ControlStabilator

All-movable tailAnti-servo tab

Ruddervators

Provides both longitudinal and directional stabilization and control.

Lateral Or Roll ControlAilerons

Rolling action produced is the primary method of lateral control on most aircraft.

Lateral Or Roll Control

Directional ControlAdverse 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 ControlRudder

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 ControlsTrim Tabs

Balance Tab

Anti-Servo Tab

Servo Tab

Spring Tab

Adjustable Stabilizer

Trim Tabs

Balance Tab

Anti-Servo Tab

Servo TabUsed 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

FlapsChange 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 DevicesDelays 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