Basic Aerodynamics& Theory of Flight

ByAhmad Ahsan

Course Grading

Marks Distribution

Aircraft Structure• Aircraft structure is required to support two types of

load• Ground Load: movement on the ground ( taxiing,

landing, and towing)• Air Loads: loads during flight by maneuvers and

gusts • Function of Aircraft Structure:• To transmit and resist loads.• To provide and maintain shape.• To protect passengers, payload, and systems from the

environmental conditions.

A. Fuselage

B. Wings

C. Empenage or

Tail

D. Power Plant

E. Landing Gear or

Undercarriage

Aircraft Components

Propeller

Landing Gear

Wing

Left Aileron

Fuselage

Empennage

Nacelle

Right Aileron

WingHorizont

al Stabilize

r

Vertical Stabilize

r

Rudder

Elevator

Main body of airplane Pilot & cargo compartments Generally constructed in two or more sections Carries accessories and other equipments Includes numerous access doors, inspection plates,

landing wheel wells, and other openings

Fuselage

• Airfoils attached to each side of the fuselage

• Main lifting surfaces

• Various design size and shape

• May be attached at the top, middle, or lower

portion of the

fuselage

- High-wing, mid-wing, and low-wing

• The number of wings can also vary

- Monoplanes, biplanes

Wing

Know n as tail section

Consist of

◦ Vertical Stabilizer

◦ Rudder

◦ Horizontal Stabilizer

◦ Elevators

Empennage - Tailplane

Power PlantA unit or machine that converts chemical energy

contains in the fuel to thrust force. Thrust force is

essential for moving the airplane forward and

producing lift force. With the piston engine, the

propeller is used to convert torque at engine shaft to

be thrust.

With the jet engine,

the jet engine

output is the

thrust force.

Located underneath of the

fuselage with shock strut

Fixed / Retractable

Provides means of landing taxiing

Tri- cycle –Conventional type

Floating gear for seaplane /ski-

equipped for ice surface landing

etc..

Landing Gear

Material use in Airframe Construction

Airframe Materials Properties

- High Strength to Weight ratio

- Light weight

- Corrosion Resistant

- Should be non flammable

- High quality

• WOOD

• STEEL & ITS ALLOYS (Strong)

• ALUMINIUM & ITS ALLOY (Commonly used)

• TITANIUM ALLOYS (Heat Barriers)

• MAGNESIUM ALLOYS (light and strong)

• PLASTICS & COMPOSITE MATERIAL (modern

and latest)

Material use in Airframe Construction

Fuselage Structure DetailTYPES OF STRUCTURETYPES OF STRUCTURE

TRUSS TYPE

- PRATT TRUSS

- WARREN TRUSS

MONOCOQUE

SEMI-MONOCOQUE

TRUSS TYPE

• Most early aircraft used this technique with

wood and wire trusses.

• The truss type fuselage frame is assembled with

members forming a rigid frame e.g. beams, bars, etc

• There are two types of truss structure.

- PRATT TRUSS

- WARREN TRUSS

PRATT TRUSSPRATT TRUSS• Early aircraft

• Wooden or metal

structure

• Heavy weight

• Box like structure

Diagonal members of tubing or solid rods

• Conical Type structure• Force transfer to other supporting beams• Capable to carry tension + compression• More space , strength , rigidity• Better streamline

WARREN TRUSSWARREN TRUSS

MONOCOQUE MONOCOQUE • In this method, the exterior surface of the fuselage is

the primary structure.

•A later form of

this structure uses

fiberglass cloth

impregnated with

polyester or epoxy

resin, instead of

plywood, as the skin.

MONOCOQUE MONOCOQUE

SEMI-MONOCOQUESEMI-MONOCOQUE•This is the preferred method of constructing an all-

aluminum fuselage.

•Includes a series of frames in the shape of the

fuselage cross sections are held in position on a

rigid fixture, or jig.

•These frames are then joined with lightweight

longitudinal elements called stringers.

•These are in turn covered with a skin of sheet

aluminum, attached by riveting or by bonding with

special adhesives.

SEMI-MONOCOQUESEMI-MONOCOQUE

Fuselage Sections are joined by usingfasteners.Fuselage Sections are joined by usingfasteners.

Basic TermsVertical Members :

• Formers: a structural member of an aircraft

fuselage, of which a typical fuselage has a

series from the nose to the empennage.

• Typically perpendicular to the longitudinal axis

of the aircraft.

• The primary purpose of formers is to establish

the shape of the fuselage, reduce the length

of stringers, and prevent instability.

Basic TermsVertical Members :

• Frame : The mechanical structure of the

aircraft including its fuselage, wings, and

empennage.

• Bulkhead : A dividing wall within an aircraft or

ship.

Longitudinal Members

• Longerons : longitudinal structural component

of an aircraft's fuselage usually along the

length of fuselage.

• Stringers : longitudinal structural components

between sections of

fuselage.

Wing Structure•In most modern airplanes, the fuel tanks are an

integral part of the wing structure, or consist of

flexible containers mounted inside of the wing.

• Attached to the rear, or trailing, edges of the wings

are two types of control surfaces referred to as

ailerons and flaps.

Empennage•The empennage includes the entire tail group,

consisting of fixed surfaces such as the vertical

stabilizer and the horizontal stabilizer.

•The movable surfaces include the rudder, the elevator,

and one or more trim tabs.

• A second type of empennage design includes a one-

piece horizontal stabilizer that pivots from a central

hinge point. ( called stabilator )

•The rudder is attached to the back of the vertical

stabilizer.

•Trim tabs are small, movable portions of the trailing

edge of the control surface. These movable trim

tabs, which are controlled from the cockpit, reduce

control pressures. Trim tabs may be installed on

the ailerons, the rudder, and/or the elevator.

Empennage Structure

Spar

RibsStringers

Skin

Spar

Stringers

Stabilator

•The landing gear is the principle support of the

airplane when parked, taxiing, taking off, or when

landing.

•The most common type of landing gear consists of

wheels. T

•The landing gear consists of three wheels — two

main wheels and a third wheel positioned either at the

front or rear of the airplane.

Landing Gear Structure

Landing Gear Types

Landing Gear Types: Tricycle, Tailwheel, Bogey

Landing Gear Types

Landing Gear Types

Other Landing Gear Types : Float & Ski

•The power plant usually includes both the engine and

the propeller. •The primary function of the engine is to provide the

power to turn the propeller. •It also generates electrical power, provides a vacuum

source for some flight instruments, and in most single-

engine airplanes, provides a source of heat for the

pilot and passengers. •The engine is covered by a cowling, or in the case of

some airplanes, surrounded by a nacelle. •The purpose of the cowling or nacelle is to streamline the

flow of air around the engine and to help cool

engine.

Power Plant

• Wing Pod Mount – Commonly use on commercial airplane since fuel is

carried in wing– Less noise– Bad yawing moment effect– Ground clearance limitation higher gear strut

• Clean wing , shorter take off.• No ground clearance limitation• Less yawing effect• Weight penalty Aft Cg. and load distribution • Cabin Noise and Vibration• Fuel pump

Fuselage Mount

• “Any surface, such as a wing, propeller, rudder, or even a trim tab, which provides aerodynamic force when it interacts with a moving stream of air.” FAA

•The mean camber line is a line drawn midway between the upper and lower surfaces

• The chord line is a straight line connecting the leading and trailing edges of the airfoil.

The Airfoil

The angle of attack is the angle between the

chord line and the average relative wind.

Greater angle of attack creates more lift (up to a

point).

Angle of Attack

Bernoulli’s Principle & Airfoil• The upper surface of an

airplane’s wing is designed to have a greater curvature or camber as compared to lower surface. This greater curvature causes air to flow faster over the upper surface.

• Due to higher speed, the pressure decreases.

• On the lower pressure, the lesser curvature causes decrease in speed and increase in pressure.

• This creates “Lift”

Four Forces of Flight

DRAG

WEIGHT

THRUST

LIFT

Lift• Lift is the force created by the interaction between the wings

and the airflow. • It opposes the downward force of weight. • Lift is an aerodynamic force and is directly proportional to the

square of velocity. • It is produced by the dynamic effect of the air acting on the

airfoil. • It acts perpendicular to the flight path.• Aircraft lift acts through a single point

called the center of pressure. • Lift Equation: L=½ ρ V2A CL

LIFT

Weight• Weight is the combined load of the aircraft, crew, fuel,

passengers, and the cargo. • Weight pulls the aircraft downward because of the force of

gravity. • It opposes lift, and acts through the aircraft’s center of gravity

(CG)• Weight is not constant

WEIGHT

Thrust• Thrust is the forward force produced by the

powerplant,propeller or rotor. • It opposes or overcomes the force of drag.• Direction of thrust depends on design

THRUST

Drag• Drag is a rearward acting force that resists the motion of

aircraft through the air.• It is an aerodynamic force and like lift varies to square of

velocity.• Two broad drag classifications.• Parasite drag: caused by disruption of airflow by the wing,

rotor, fuselage, and other parts of structure. • Induced drag: produced as reaction of lift• Drag Equation: D= ½ ρ V2A CD

DRAG

The Ailerons control movement on the lateral axis called

“rolling”.

Control around the Longitudinal AxisAssignment

The End