Private GL07- Aerodynamic Principles

which factors cause more induced drag or less induced drag: 1. low speed, high aoa, large wingtip vortices 2. high speed, low aoa, small wingtip vortices

1 = more induced drag 2= less induced drag

primary wing design factors (4)

1. airfoil camber 2. aspect ratio 3. wing area 4. wing planform camber: upper camber and lower camber wingspan/average chord = aspect ratio wing area= wingspan x average chord

which prop characteristics affect thrust

1. airfoil shape of the prop blade causes high pressure on its rear face and low pressure on its front face. the pressure difference generates thrust 2. airfoil section of the prop blade changes smoothly from a thick, low speed airfoil at the root of the blade to a thin, high speed airfoil at the tip 3. AOA changes smoothly bw the root and the tip, with each section having the optimum AOA for the speed at that point, providing max thrust throughout length of blade

how does ground effect change airplane performance near the ground

1. airplane seems to "float" when landing 2. at lower than normal climb speed, plane might climb initially, and then settle back to the runway 3. plane will lift off at lower than normal airspeed.

how does an airfoil create lift?

1. as the wing forces air downward, the wing lifts upward in response (newtons 3rd law) 2. airfoil causes air flowing along its lower surface to slow down, which increases air pressure below the wing 3. pressure difference bw the higher air pressure below the wing and the lower air pressure above wing creates lift

pilot control of lift:

1. can increase or decrease aoa 2. can change airspeed. this proportionally changes amount of lift. Double the airspeed, will quadruple the lift >>> half the airspeed, 1/4 amt of lift 3. change wing shape by lowering flaps. lowering flaps, increases lift. and decreases stall speed increasing lift also increases drag, which is a byproduct of lift.

how can pilots ^ lift during flight?

1. increase airspeed 2. change the wing shape by lowering the flaps 3. increase the angle of attack

what happens when you fly a plane within one wingspan height of the ground

1. induced drag is reduced 2. more of the wing's lift acts vertically 3. lift is increased 4. wing can create enough lift at a lower airspeed to support weight of the plane.

4 forces of flight

1. lift- supports plane in flight. created by airflow above and below wing. 2. weight- opposes lift and is result of gravity 3. thrust- propels plane forward and varies with applied engine power 4. drag opposes thrust and is a backward or retarding force that limits speed of plane

what is the relationship bw parasite drag and airspeed

1. parasite drag decreases as speed decreases. 2. doubling your airspeed quadruples parasite drag 3. parasite drag increases as speed increases

types of flaps (4)

1. plain flaps- extend and pivot downward from tailing edge of wing; ^ overall camber of wing, change chord line, and ^ wing's lifting capacity 2. split flaps, hinged only to lower surface of wing; flaps ^ lift but produce greater drag 3. slotted flaps- change camber and chord line; allow high pressure air from beneath wing to flow over flap surface; increase lift and delay airflow separation at higher AOA 4. fowler flaps- attach to wing by track and roller system; extend both rearward and down to ^ wing area and change the camber and chord line many planes use flaps for takeoff as well as landing

if an airplane has a wingspan of 120 ft and an average chord of 12 ft, what is its aspect ratio

10 ft

if a plane has a wingspan of 144 ft and an average chord of 12 ft, what is the aspect ratio?

144/ 12 = 12

if an airfoil moves twice as fast through the air, it generates

4x more lift

extending flaps

> changes camber to increase the coefficient of lift. > changes chord line and increases angle of attack

how does the angle of attack affect the coefficient of lift?

> if the angle of attack exceeds CLmax, lift decreases > as angle of attack increases, lift increases until the coefficient of lift reaches CLmax

vectors

> vector arrow length represents the magnitude of the force > vector arrow orientation represents direction of force > 2 or more vectors acting on an object at the same time can be added or subtracted to create a resultant vector

relationship between air velocity and lift?

> when there is no air flowing over an airfoil there is no lift > to generate lift, an airfoil needs motion relative to the air > the faster an airfoil moves relative to the air, the more lift it generates > if all other factors remain the same, doubling the airspeed, quadruples the amount of lift.

which type of flap is attached to the wing by a track and roller system

fowler flap

what angle of attack yields the greatest coefficient of lift

CLmax

what factors cause an airfoil to stall

CLmax is exceeded and the airflow separates from the upper surface of the wing

how does the angle of attack affect induced drag

a lower angle of attack creates smaller wingtip vortices, reducing induced drag

newton's 2nd law of motion states that when a force is applied to a mass, the mass will

accelerate

how does changing the thickness of a prop from root to tip affect thrust

airfoil shape at the root provides max thrust at the low rotational speeds that occur near the hub and a thin, flat airfoil provides max thrust at tip

what is purpose of flaps

allow for slower touchdown, ^ camber to provide lift, help maintain lift at low airspeeds, such as during landing, ^ lifting efficiency and decrease stall speed

a wing interacting with a moving stream of air is an example of

an airfoil

what causes an airfoil to stall

an airfoil will stall when it exceeds its critical aoa, regardless of weight, airspeed, or flight attitude at any angle of attack above CLmax, lift decreases as smooth airflow over the upper surface of the wing becomes turbulent and separates

newton's 3rd law of motion states that every application of force results in

an equal and opposite rxn force

what is angle of attack

angle between the chord line of an airfoil and the relative wind > AOA can change based on pilot input or external factors like updrafts or wind gusts

what is the angle of attack

angle bw relative wind and the chord line of an airfoil

super important thing that affects amount of lift generated?

angle of attack

what is the angle bw the wind chord line and a line parallel to the longitudinal axis of the airplane

angle of incidence

what is an ailfoil

any surface that provides lift when it interacts with a moving stream of air

newton's laws of motion 1st

apply to all objects in motion or at rest 1st law: > object at rest will remain at rest unless acted upon by an outside force > object in motion cont in motion with same speed and direction unless acted upon by outside force

how does the bernoulli principle apply to lift

as air flows faster over the top of the airfoil, pressure decreases, and as air slows down under the bottom of the airfoil, pressure increases

drag

backward or retarding, force that limits the forward speed of aircraft. opposes thrust. by reducing drag, you can go faster w the same amt of thrust

equilibrium

change in any single force creates changes of varying magnitude in other forces. equilibrium exists when: > lift = weight > drag equals thrust equilibrium can exist at straight and level, climb or descent. > when plane returns to equilibirum, there are no acceleration forces, and plane is in unaccelerated flight.

ground effects relationship to drag

changes the airflow pattern due to ground effect: > modifies average relative wind > causes more of the wing's lift to act vertically > this decreases induced drag allows wings to create enough lift at a lower speed to support the weight of plane.

angle of attack and coefficient of lift

coefficient of lift (CL) is a way to measure lift as it relates to angle of attack. CL is determined by airfoil design and angle of attack.

lift to drag ratio (L/D)

comparing lift generated by wings to total drag provides lift/drag ratio (L/D) Lift/Drag = L/D ratio L/D ratio varies with the aoa of the airfoil L/D max is the aoa where the lift-drag ratio reaches its maximum value. corresponds to the power off glides speed that provides best glide ratio of the airplane. L/D max also provides most efficient fuel economy > airspeed for achieving L/D max varies with the weight of plane; however aoa for L/D max doesn't vary significantly

objects at rest tend to remain at rest, and objects in motion tend to

cont in motion at the same speed and in the same direction unless acted upon by an outside force

which of the following causes the total weight of an aircraft to change during flight

crop dusting

bernoulli's principle states that as the velocity of a fluid increases, its pressure

decreases

what is interference drag

drag created when the air flowing around one part of the plane interacts with air moving at a different speed or direction around an adjacent part of the plane

stall strips

enhance flight safety. are metal strips attached to leading edge of each wing, near wing roots. > disrupt airflow at high angles of attack >>>causes wing root area behind them to stall before the wingtips >>> helps to preserve aileron effectiveness, providing an opportunity for recovery before the stall progresses to wingtips

generating thrust

forward force that propels plane through air. thrust begins when the expansion of burning gases in the engine creates a force that turns the propeller > prop is a rotating airfoil and its motion accelerates a mass of air backward. Newton's 3rd law states that an equal and opposite force acts in a forward direction as a reaction.

which from this list cause a change to aircraft weight? fuel consumption, change in air density, firefighting, ambient temp changes, adding passengers, crop dusting, loading fuel

fuel consumption, firefighting, adding passengers, crop dusting, and loading fuel

camber

fundamental characteristic of wing design. refers to curvature of airfoil from front to back There are upper and lower changes in camber affects lift. > if upper camber increases and lower camber remains the same, the velocity differential bw the upper and lower surfaces increases, increasing lift

ground effect truths

ground effect occurs within 1 wingspan's distance from the ground or water, is more noticeable in low-wing planes because wings are closer to ground, and occurs when ground alters airflow around the wing.

ground effect and performance

if you try to fly out of ground effect- more thrust is req. to sustain lift. however they may not be any more thrust available because you normally take off with max thrust, induced drag suddenly increases, and increased drag slows the plane and reduces lift. ground effect may allow an overloaded or improperly configured plane to lift off but it won't be able to climb. ground effect is responsible for "floating" during the landing flare. > may need to reduce pitch angle slightly to maintain a descent. you must reduce thrust to cont. slowing plane for landing.

how can pilots ^ amt of lift during flight

increase airspeed

high lift devices.

increase efficiency of the airfoil at low speeds. flaps are the most common high-lift device flap- is a surface at the trailing edge of a wing that has hinges or tracks so its trailing edge can move downward leading edge devices provide better stall characteristics, reduce landing speed, and can increase airfoil camber slots allow airflow to remain attached over the outer portion of the wings after roots have stalled. slots dont causes much change in effectiveness of airfoil when wing is at low AOA SLATS tho are portions of leading edge that can move forward & down to create a path for air similar to a slot. will increase effective wing area. leading edge flaps- usually ^ both wing camber and ara, allowing wing to develop more lift at reduced airspeeds. normally just found on jets

if upper camber of an airfoil is increased while the lower camber remains unchanged, lift:

increases

when wing area increases, the amount of lift produced by the wing

increases

which type of drag decreases as airspeed increases

induced

two types of drag

induced drag- result of wings producing lift. it decreases as plane goes faster parasite drag- all other drag. any drag unrelated to production of lift. it increases with speed

force of weight

is force of gravity, which acts vertically towards c.o.g > isn't constant. varies over duration of flight. Weight of plane increases as you add: > fuel >baggage > pilot and passengers total weight of plane decreases as fuel is consumed.

factors affecting induced drag

it is typically greater at low airspeed and decreases at higher airspeed.

what force causes induced drag

lift

what happens to lift when the upper camber of an airfoil is increased while the lower camber remains unchanged

lift increases

how do you calculate the lift needed to support the aircraft? related to wing area

lift needed to support aircraft: plane weight/ wing area= lift (pounds per sq. ft) lb/ft^2 amount of lift a wing produces is directly proportional to the wing area

test: what are the 4 forces that act on a plane during flight

lift, weight, thrust, and drag

parasite drag (3 types)

like force you feel when you put hand out window of car any drag unrelated to production of lift 3 types: 1. form- from turbulent wake that occurs when airflow separates from surface of the object (streamlining decreases form drag by reducing airflow separation) Never eliminated entirely! interference drag- when air flowing around one part of the airplane interacts with air moving at a different speed or in a different direction around an adjacent part. (ex. at wing root two different flow patterns come together) 3. skin friction drag- caused by roughness of airplane surfaces. thin layer of air clings to rough surfaces, causing eddies that contribute to drag. minimized with glossy surface or rivets sticking out

what do the length and orientation of a vector arrow represent?

magnitude and direction

wing twist

or washout. is a design feature that creates a lower angle of incidence at the wingtip than at the wing root. >>> results in the wingtip having a lower angle of attack than the root when approaching a stall

relationship between airspeed and parasite drag

parasite drag is proportional to the square of the airspeed: doubling your airspeed quadruples parasite drag > plane top speed is limited by rapid ^ in parasite drag

what happens to the amt of parasite drag when you double your airspeed

parasite drag quadruples

relative wind and flight path

plane's flight path is its line of travel through the air. when applied to the entire plane, relative wind is always directly opposite to the flight path.

prop characteristics affecting thrust cont.

prop blade twists slightly from root to tip and is thicker at root. This helps compensate for fact that blade tips travel at a higher speed than roots.

what generates thrust for prop driven planes

prop forces air backward, creating a rxn force forward

prop characteristics that affect thrust

prop provides the thrust that moves plane through air. each prop blade works like airplane wing > airflow creates high pressure on the rear face of prop and a low air pressure on front face. difference in pressure creates force moving toward the front of the prop called thrust. when prop is turning but plane isnt moving, the blade angle, or pitch, is equivalent to the AOA for an airplane wing. Plane of rotation is equivalent to the flight path of a wing.

generating thrust cont

prop. rotates in circular path called plane of rotation angle of prop blade relative to plane of rotation is the blade angle/ pitch

an airfoil is any surface that:

provides lift when it interacts with a moving stream of air

planform

refers to shape of airplane wing when viewed from above or below 1. sweptback- efficient at high speeds but degraded low speed performance 2. combination: rectangular and tapered- good compromise for low speed planes. rectangular inboard exhibits good stall characteristics and is cost effective. tapered outboard portion allows for reduction in weight and increases aspect ratio 3. highly tapered- provied decrease in drag and more lift for effective high speed flight. tapered wings have a tendency to stall first slightly inboard of wingtip 4. rectangular- tends to stall first at wing room, which gives adequate stall warning and aileron effectiveness

aspect ratio

relationship between the length and width of a wing. is a primary factor determining lift and drag characteristics Higher the aspect ratio, higher the lifting efficiency of the wing aspect ratio= wing span (wingtip to wingtip) / wing's average chord

what is always directly opposite the flight path of a plane

relative wind

what is clean configuration

shape of a plane when the gear and flaps are up in a retractable gear airplane

what wing design element ensures the wing root stalls before the wing tip to help preserve aileron effectiveness

stall strips

what is equilibrium

state in which all opposing forces are balanced

bernoulli's principle

states that as the velocity of a fluid increases, its pressure decreases. explains how propellers produce thrust

what is a stall

sudden decrease in lift that occurs when the airfoil exceeds the angle of attack for CLmax. > at any AOA above CLmax, lift decreases rapidly as the smooth airflow over the upper surface of the wing becomes turbulent and separates

what is total drag

sum of parasite and induced drag

what is total drag

sum of parasite drag and induced drag. total drag varies over the speed range. because induced drag decreases with speed and parasite drag increases with speed. drag is at its minimum where parasite drag and induced drag are equal.

how does a prop driven airplane create thrust

the prop accelerates a mass of air backward, and the rxn force drives the airplane forward

what happens to an airplane in unaccelerated flight if one or mor of the four forces changes

there will be an acceleration in the direction of the stronger force until the opposing forces are again in equilibrium

which force acts in opposition to drag

thrust

what is the purpose of a wing twist

to ensure that the wing roots stall before wingtips

what is the purpose of flaps when landing

to maintain lift at low airspeeds for a safer landing

what is L/D Ratio

total lift divided by total drag

wing area

total surface area of wings. must be sufficient enough to: > support the weight of the plane > maintain lift the greater the wing area, the more lift it produces.

T/F when applied to the entire plane, relative wind is always directly opposite to the flight path

true- an aircraft's flight path is its line of travel through the air

angle of incidence.

upward angle formed bw the chord line and a line parallel to the longitudinal axis

what force acts vertically toward the center of the earth

weight

newton's 2nd law

when a force is applied to a mass, mass will accelerate. F=ma as plane moves, additional thrust may cause it to speed up, friction works to slow it down, and turning the nosewheel may cause a change in direction

true statements about 2nd law

when a force is applied to a mass, the mass will accelerate, and a large force applied to a small mass causes a larger acceleration than the same force applied to a larger mass

ground effect

when a plane flies within one wingspan's distance from the ground or water, the earth's surface alters the 3d airflow around the plane and reduces induced drag. will notice during takeoff and landing. >>> there is a reduction in upwash, downwash, and wingtip vortices- ground effect >>> induced drag is about 1/2 its usual value when the wing is 1/10 of a wingspan above the ground >>> more noticeable in low wing plane because wings closer to ground.

3rd law of motion

whenever one body exerts a force on another, the second always exerts an equal force in the opposite direction. for every action there is an equal and opposite rxn > air and propeller

which of the following wing design features ensures that the wing root stall before the wingtips so the ailerons remain effective during recovery?

wing twist

what is the primary cause of induced drag

wingtip vortices. so at low airspeed with high aoa you have high induced drag at high airspeed a lower aoa generates the necessary amt of lift so the wingtip vortices are less powerful and create less induced drag smaller the angle of attack, the less the induced drag the wings produce

does coefficient of Lift increase with aoa?

yes.