Chapter 3 Aerodynamic Principles

Within _________ above the the surface, ground effect is most common.

1 wingspan

Newton's first law of motion states ____________.

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 unless it is acted on by other forces.

Changes in the center of pressure of a wing affect the aircraft's ______________.

Aerodynamic balance and controllability

Explain Bernoulli's principle.

As the velocity of a fluid increases, it;s internal pressure decreases

____________ is the relationship between the length an width of a wing.

Aspect ratio

Which problem is most likely to result from ground effect?

Becoming airborne before reaching the appropriate takeoff speed

_________ states that as the velocity of a fluid increases, its pressure decreases.

Bernoulli's principle

The distance forward and aft of the optimal position for the center of gravity is the ___________.

CG range

____________ is the capability of an airplane to respond to your control inputs, especially with regard to attitude and flight path.

Controllability

__________ is the upward angle of the airplane's wings with respect to the horizontal.

Dihedral

_________ is a backward, or retarding, force which limits the speed of the airplane.

Drag

Newton's third law states ___________.

Every force applied to an object is opposed by an equal force in the opposite direction.

_______ increase the lifting efficiency of the wing and decrease stall speed.

Flaps

__________ allow you to steepen the angle of descent on an approach without increasing airspeed.

Flaps

_________ results from the turbulent wake caused by the separation of airflow from the surface of a structure.

Form drag

__________ is the result of the earth's surface altering the airflow patterns about the airplane.

Ground effect

____________ is the result of interference of the surface of the earth with the airflow patterns about an airplane.

Ground effect

__________ is generated by the airflow circulation around the wing as it creates lift.

Induced drag

What must a pilot be aware of as a result of ground effect?

Induced drag decreases, therefore any excess speed at the point of flare may cause considerable floating

__________ occurs when the airflow around one part of the airplane interacts with the airflow around an adjacent part.

Interference drag

How will an airplane loaded to its aft CG limit behave?

It will be less stable at all speeds

________ is the steadying influence exerted by the side area of the fuselage and vertical stabilizer.

Keel effect

_________ is the force created by the effect of airflow as it passes over and under the wing.

Lift

_____________ is the characteristic of an airplane that permits you to maneuver it easily and allows it to withstand the stress resulting from the maneuvers.

Maneuverability

________ is caused by any aircraft surface which deflects or interferes with the smooth airflow around the airplane.

Parasite drag

__________ is normally divided into form drag, interference drag, and skin friction drag.

Parasite drag

_________ refers to the shape of the airplane's wing when viewed from above or below.

Planform

____________ is caused by the roughness of the airplane's surfaces.

Skin friction drag

__________ is the characteristic of an airplane in flight that causes it to return to a condition of equilibrium, or steady flight, after it is disturbed.

Stability

__________ disrupt the airflow at high angles of attack, causing the wing area directly behind them to stall before the wingtips stall.

Stall strips

_________ is the forward force which propels the airplane through the air.

Thrust

__________ is the sum of parasite and induced drag.

Total drag

One way to visualize Bernoulli's principle is to imagine air flowing through a ________.

Venturi

_________ is caused by downward pull of gravity.

Weight

_________ is the total surface area of the wings.

Wing area

_________ is a major contributor to lateral stability.

Wing dihedral

________ movement around the vertical axis is produced by the rudder.

Yaw

An airplane becomes progressively more difficult to control as the CG moves _____.

aft

If the CG is beyond the _______ it will be difficult to lower the nose to recover from a stall or spin.

aft limit

The _______ turn the plane around its longitudinal axis.

ailerons

An ________ is any surface, such as a wing, that provides an aerodynamic force when it interacts with a moving stream of air.

airfoil

An airplane always stalls when the critical angle of attack is exceeded regardless of _________, _________, or _________.

airspeed, flight attitude, weight

The angle formed by the wing chord line and the relative wind is called the ___________.

angel of attack (AOA)

The __________ refers to the angle between the wing chord line and a line parallel to the longitudinal access of the airplane.

angle of incidence

What does Bernoulli's principle state?

as the velocity of a fluid increases, its pressure decreases

The angle between the chord line of an airfoil and the relative wind is known as the angle of _________.

attack

The _________ is the characteristic curve of the airfoil's upper and lower surfaces.

camber

The common reference point for the three axes is the airplane's ______________.

center of gravity (CG)

The longitudinal stability of an airplane is determined primarily by the location of the ____________ in relation to the ____________.

center of gravity, center of pressure (lift)

The center of pressure is sometimes referred to as the ________________.

center of lift.

The _________ is a point along the wing chord line where lift is considered to be concentrated.

center of pressure

The _______ is an imaginary straight line drawn through the airfoil from the leading edge to the trailing edge.

chord line

The AOA is formed by the _________ and the _________.

chord line, relative wind

The term "angle of attack" is defined as the angle between the _______ and the __________.

chord line, relative wind

The _________ is a way to measure lift as it relates to the angle of attack.

coefficient of lift (CL)

In training airplanes, __________ normally refers to the position of the landing gear and flaps.

configuration

An airplane always stalls when the ___________ is exceeded regardless of airspeed, flight attitude, or weight.

critical angle of attack

For a given airplane, a stall always occurs at the same angle, regardless of airspeed, flight attitude, or weight. This angle is the stalling or __________.

critical angle of attack

If airspeed is ________, parasite drag increases __________.

doubled, fourfold

The _______ pitches the plane over its lateral axis.

elevator

Newton's second law states __________.

f = ma

Parasite drag is normally divided into _______, _________, and ________.

form drag, interference drag, skin friction drag

If airspeed is doubled, parasite drag increases _________.

fourfold

The angle of attack at which an airplane wing stalls will remain the same regardless of _____________.

gross weight

In ________, induced drag decreases and excess speed in the flare may cause floating when the aircraft is within one wingspan above the surface.

ground effect

In _________ an airplane may become airborne before it reaches its recommended takeoff speed.

ground effect

The phenomenon of ________ is associated with the reduction of induced drag.

ground effect

As power reduction in airplanes, other than T-tails will decrease the downwash on the ___________ from the wings and propeller slipstream, This is what causes the nose to pitch down after a power reduction.

horizontal stabilizer

One of the main functions of flaps during approach and landing is to ___________ the angle of descent without ___________ airspeed.

increase, increasing

The component of lift acting in a rearward direction is _________.

induced drag

An airplane said to be __________ will require less effort to control.

inherently stable

Induced drag is _______ proportional to the square of the speed.

inversely

If one wing is lower than the opposite wing, __________ helps return the wings to a level attitude.

lateral stability

Stability about an airplane's longitudinal axis, which extends nose to tail, is called __________ .

lateral stability

A higher aspect ratio produces __________ for the same amount of lift.

less drag

In straight and level flight, ________ equals weight and ________ equals drag.

lift, thrust

The four forces acting on an airplane in flight are ________, ________, ________, and _________.

lift, weight, thrust, drag

The four forces acting on an airplane in flight are ________, _________, _________, and _________.

lift, weight, thrust, drag

The ________ of an airplane involves the pitching motion or tendency of the aircraft to move about its lateral axis.

longitudinal stability

The three axes of flight are the __________, ___________, and ____________ of flight.

longitudinal, lateral, vertical axes

One purpose of wing flaps is to allow the pilot to _____________________.

make steeper approaches to a landing without increasing airspeed

The first indications of a stall include ____________, ___________, or ___________.

mushy feeling in the flight controls, a stall warning device, ,a slight buffeting of the airplane

If you load your airplane so the CG is forward of the forward CG limit, it will be too _________.

nose heavy

If you reduce power during flight, a ________ pitching tendency occurs due to the reduction of downwash from the wings and the propeller which reduces elevator effectiveness.

nose-down

Floating caused by ground effect is most noticeable at a distance of less than ___________ above the surface.

one wingspan

Drag is classified as either _______ or ________.

parasite, induced

An aircraft that doesn't return to the original position, but instead does so over a period of time through a series of successively smaller oscillations, the aircraft displays ______________.

positive dynamic stability

The initial tendency to return to the position from which it it was displaced is termed __________________.

positive static stability

The __________ is the airflow which is parallel to and opposite the flight path of the airplane.

relative wind

Aspect ratio = (________)/(________)

span, average cord

A ______ is caused by the separation of airflow from the wing's upper surface.

stall

Another method sometimes used to ensure positive control during the stall is installation of __________ which consist of two metal strips attached to the leading edge of each wing near the fuselage.

stall strips

If the CG is beyond the aft limit, it will be difficult to lower the nose to recover from a ________ or ________.

stall, spin

Flaps allow you to _______ the angle of descent on an approach without ________ airspeed.

steepen, increasing

In __________, __________ flight, lift equals weight and thrust equals drag.

straight and level, unaccelerated

When are the four forces that act on an airplane in equilibrium?

straight and level, unaccelerated flight

Additional forces are exerted on the horizontal ________ of most aircraft by downwash from the propeller and the wings.

tail surfaces

The negative lift on the tail which counteracts nose heaviness is called ___________.

tail-down force

The four forces acting on an airplane in flight are in equilibrium during _____________.

unaccelerated flight

The _________ have the effect of deflecting the airstream downward in the vicinity of the wingtip, creating an increase in downwash.

wingtip vortices