ToF - Four Forces of Flight

Prelims Quiz 2

Law of Inertia

First law of Motion

Law of Inertia

A body at rest tends to remain at rest, and a body in motion tends to remain moving at the same speed and in the same direction.

Law of Acceleration

Second law of Motion

Law of Acceleration

When a body is acted upon by a constant force, its resulting acceleration is inversely proportional to the mass of the body and is directly proportional to the applied force

Law of Action-Reaction

Third Law of Motion

Law of Action-Reaction

Whenever one body exerts a force on another, the second body always exerts on the first, a force that is equal in magnitude but opposite in direction.

THRUST

DRAG

WEIGHT

LIFT

Forces Acting on an Airplane

downward

Sum of all upward forces equals the sum of all ___ forces

backward

Sum of all forward forces equals the sum of all ___forces

Velocity of air

Angle of attack

Surface area of wing (Aspect Ratio)

Density of air

Four(4) factors that affects Lift

Lift

Perpendicular to the flight path through the wing’s center of lift. Proportional to the square of the airplane’s velocity.

four

Airplane traveling at 200 knots has ___ times the lift as the same airplane traveling at 100 knots, if the angle of attack and other factors remain constant

twice

A wing with a planform area of 200 square feet lifts ___ as much at the same angle of attack as a wing with an area of 100 square feet

Daniel Bernoulli

Bernoulli’s Principle was developed by a Swiss Mathematician and Physicist named

Bernoulli’s Principle

____ dictates that the faster a fluid moves, the lower the pressure it exerts on the area.

PRESSURE DIFFERENTIAL

The fast flowing air above the wings decreases the surrounding air pressure. Because the air pressure is greater below the airfoil than above, a resulting lift force is created. This _________ is the main cause for lift.

angle of attack

During flights at normal operating speeds, if you increase the ____, you increase lift.

Early Airfoil

Late Airfoil
Clark ‘Y’ Airfoil
Laminar Flow Airfoil

Subsonic Airfoil Design

Circular Arc Airfoil
Double Wedge Airfoil

Supersonic Airfoil Design

Planform

Shape of the airplane’s wings when viewed from above.

Straight
Elliptical
Tapered
Sweptback
Delta

Airfoil Types

Aspect Ratio

Span divided by Average Chord = ___

lifting efficiency

In general, the higher the Aspect Ratio, the higher the ___ of the wings

Angle Of Incidence

Wings are typically mounted at a small positive angle of incidence, to allow the fuselage to be "flat" to the airflow in normal cruising flight. The angle between the longitudinal axis and the wing chord.

forward

In general, at high angles of attack the center of pressure moves ____, while at low angles of attack the center of pressure moves aft.

aft

In general, at high angles of attack the center of pressure moves forward, while at low angles of attack the center of pressure moves ___.

CL

As angle of attack increases, __ also increases until CLmax

stalled

A wing can be ___at any airspeed and any altitude

Plain Flaps
Split Flaps
Slotted Flaps
Fowler Flaps

Four Basic Type of Flaps

Lifting Device
Drag Device
Allows a steep angle of descent, without increasing airspeed.

Flaps have 3 main purposes:

increase

once the FLAP extension reaches approximately the midpoint, a significant __ in DRAG will occur for a relatively small increase in lift.

half

Most manufacturers limit the takeoff setting to __ flaps or less (FLAPS 10° for Cessna 172)

WEIGHT

Combined load of airplane, crew, pax & cargo. It opposes lift, and acts vertically downward through the airplane’s center of gravity

THRUST

Forward force produced by the engine and propeller. Forward force needed to produce speed.

DRAG

Rearward, retarding force, and is caused by disruption of airflow by the wing, fuselage, and other protruding objects.

Parasite Drag
Induced Drag

2 Types of Drag

Form Drag

Skin Friction Drag

Interference Drag

3 types of Parasite Drag

four

Doubling the airspeed increases the drag __ times, and tripling the airspeed increases the drag nine times

nine

Doubling the airspeed increases the drag four times, and tripling the airspeed increases the drag __ times

Form drag

is the portion of parasite drag generated by the aircraft due to its shape and airflow around it.

Skin Friction Drag

is the aerodynamic resistance due to the contact of moving air with the surface of an aircraft. Aircraft designers utilize flush mount rivets and remove any irregularities which may protrude above the wing surface.

Interference drag

comes from the intersection of airstreams that creates eddy currents, turbulence, or restricts smooth airflow.

perpendicular

he most interference drag is observed when two surfaces meet at ___ angles.

Induced Drag

Inherent whenever a wing is producing lift. Inseparable from the production of lift. Rearward component of lift.

increases

As angle of attack increases, induced drag ___ proportionally.