8.3 theory of flight Flashcards
wat are the 4 fundamental forces?
lift
weight
thrust
drag
what is glide ratio?
ratio of distance forward to the distance downwards
what does glide scope vary with?
decreasing airspeed and fundamental forces
will glide scope change if fundamental forces remain the same?
the glide ratio will remain constant
the max value of the glide ratio is relative to what?
lift and drag ratio
what is the glide ratio the sum off?
forward speed divided by the sink speed
what must a heavier aircraft do to ensure it has the same glide scope as a lighter aircraft?
higher airspeed is required
what does the sum of all upward components of forces equal what?
equals the sum of all downwards components of forces
what does the sum of all forward components of forces equal?
the sum of all backwards components of forces
lift is equal to what?
weight
sum of vertical force is 0
no climb or decent
power plant is set so thrust is equal to what?
to drag
sum of horizontal forces is 0
no change in acceleration
what is the clockwise moments acting on an aircraft are equal to what?
the anticlockwise moment acting on an aircraft
sum of moment of 0
no rotation
what are moments caused by?
forces on a lever not acting through the point of rotation
what does lift on the wing carry?
weight of aircraft and downwards acting stabilizer
anti clockwise rotation equals what?
clockwise rotation
what does lift produce?
L1 to produce a anticlockwise rotation and forward force
what must L1 be balanced by?
a clockwise rotation giving upwards force to ensure equilibrium is maintained
what is the wing pitching moment a product of?
lift and distance between center of gravity and center of pressure of the wing
how can a pitching moment of a wing be measured?
direct measurement on a balance or by pressure plotting
if pitching moments are measured at various points along the cord for 7 values what will we find?
at one particular point the centrifugal moment will be constant
what are the ways of considering the effects of changing angle of attack on the pitching moment on an airfoil?
change in lift through CP
changes in aerodynamic center
what happens when an aircraft enters climb?
weight acting parallel to the drag line which slows it further
what are the primary factors affecting performance?
take off and landing distance
rate of climb
ceiling
payload
range
speed
maneuverability
stability
fuel economy
what does aircraft performance result from?
combination of aircraft powerplant and characteristics
aircraft characteristics define what?
power and thrust requirements for various conditions of flight
what does the red, blue, green curve represent in total drag diagram?
red = induced drag
blue = parasite drag
green = total drag
what does a aircraft require to fly?
mechanical energy
what are the two forms of mechanical energy?
kinetic - energy of speed
potential - stored energy
what formula summarizes energy relationships?
KE = 1/2 * m * a
PE = m * g * h
what is thrust measured in?
pounds or newtons
when does positive climb performance occur?
when an aircraft gains PE by increasing altitude
the combination of what factors contributes t positive climb performance?
aircraft climb using excess power
aircraft climb by converting airspeed to altitude
what does an increase in altitude also does what?
increase the power required to decrease the power available climb performance diminished with altitude
what is range performance?
ability of an aircraft to convert fuel energy into flying distance
rang performance appears in what forms?
take max flying distance from given fuel load
to fly at specified distance with minimum fuel used
if max specific range is desired what must flight conditions provide?
flight conditions must provide max speed pre fuel flow
the values of specific range versus speed are affected by what variables?
aircraft gross weight
altitude
external aerodynamic configuration of the aircraft
when an aircraft flies at a constant altitude with its wings level what happens?
lift is equal to the weight of the aircraft
what happens when an aircraft banks?
lift acts inwards toward center of turn and upwards
an aircraft requires what to make a turn?
sidewards force
the force of lift is divided into what?
vertical ad horizontal components at right angles to each other
what is the vertical component of a turn?
weight
what is the horizonal component of a turn?
force that pulls the aircraft from straight path into a turn
what is centrifugal force?
equal and opposite reaction of aircraft to change the direction and act as equal and opposite to the horizontal component of lift
for an aircraft to turn it must be what?
banked
what must happen to ensure the aircraft maintains its altitude during turn?
lift must be equal to the resultant of centrifugal force and weight
what is the risk of increasing AOA to maintain the vertical component of lift?
could reach critical AOA so risk of accelerated stall
what must compensate for added lift if airspeed was increased during a turn what must happen?
AOA must decrease or increase bank angle to maintain constant altitude
what happens in a slipping turn?
aircraft is not turning at the rate appropriate to the bank being used since yaw is outside the turn path
when the aircraft is banked to much the horizonal component is grater than what?
grater than centrifugal force
equilibrium is what during a turn?
horizontal lift and centrifugal force is re established by decreasing the bank or increasing the turn or both
what does a skidding turn result from?
excess centrifugal force over the horizontal over horizontal lift component
maximum load factor at given bank angle what is the ratio?
ratio of lift to weight
load factor is given in what ratio?
in grams
load factor is a representation of what?
the load of the aircraft structure compared to the relative acceleration of gravity in straight and level flight
what is the max load factor given as?
limit load factors
what load id an aircraft designed to handle for safety?
limit load factor
the load factor is the resultant of what?
resultant force or lift in a turn divided by the weight
load factor can also be described as what?
g load
the load factor is related to the max bank angle why?
for structural strength of the aircraft and passenger comfort
the higher the speed what is the rate of turn?
the slower the rate of turn
what is a stall?
aerodynamic loss of lift that occurs when an airfoil exeats critical angle of attack and smooth flow over the wing breaks
where can stall occur?
at any sir speed or any altitude
once stall has occurred what must happen?
reduce AOA below original stalling angle to restore lift
what are the characteristics of a stall?
loss of lift
pitch down
roll or yaw to one side
how easy is it to recover a stall with a nose pitch down moment in a stable aircraft?
easy by lowering pitch altitude
how easy is it to recover a stall with a nose pitching down moment on a unstable aircraft?
hard as it can go in to a spin which can be impossible to recover from
where are stalls common?
at low speeds
where is the more room to recover from a stall in flight?
during landing and takeoff
the graph of load factor can be plotted against what?
against indicated airspeed
what is the flight envelope diagram known as?
V n diagrams
each flight envelope is an illustration of what?
aircrafts gross weight
configuration of flaps and landing gear
applicable altitude
in the V n diagram what are the different stages?
normal operating range
caution range
structural damage
structural failure
what are structural limits?
positive and negative G allowed limits of the aircraft
what are structural limits also refereed to?
acceleration limits or limit loads factors
what will numerous over stresses cause?
shorten the service life of the aircraft
what do aeroelastic limits define?
the max operating speeds
above this structural damage or failure can occur
what is the aeroelastic limit frequently referred to as?
redline airspeeds
what does ultimate structural limits define?
operating strength limits of the aircraft
ultimate structural loads are outside what?
outside normal operating envelope
what is the usual aircraft designee rule for ultimate structural limits?
150% of the structural limit
what do plain flaps do?
change wing curvature when extended increasing flow serrating at the trailing edge creating larger drag
what is the maximum angle of attack of plain flaps?
12 degrease
what increase in lift does plain flaps give?
50% - 55% of increase in lift
what increase in lift for single slotted flap?
65% - 70% at 16 degrease AOA
what is the increase in lift for multi slotted flap?
70% at 18 degrease
what does splatted flap produce?
higher level of lift
what do split flaps produce?
a nose pitching down moment with 60% - 65% increase in lift at 14 degrease
what s the most common type of flaps on aircraft?
fowler flaps
what do fowler flaps allow pilots to do?
to change settings for take off and landing
what do fowler flaps increase?
wing area when extended witch can help generate lift
what do fowler flaps produce?
nose down pitching moment with a 95% increase in lift at 15 degrease of angle of attack
flaps create a change in what?
in pressure
what flaps create the most pressure change?
slotted flaps
what flaps create the smallest pressure change?
plain wing
what happens when flaps are lowered?
lift is increased and is to proportional increase in drag
what do leading edge flaps lower?
staling speeds
what happens when the leading edge and not the trailing edge is dropped?
increase in stalling angle and level flight stalling altitude
leading edge flaps can be licked with what?
airspeed measuring systems so they droop when the speeds fall below the minimum
what do Kruger flaps increases?
increase wings camber to generate more lift
wat type of wings are Kruger flaps installed on?
on swept wings
slotted Kruger flaps have similar aerodynamic performance to slotted flaps but what is different?
they have a different deployment method
what do leading edge flaps increase?
the Cl
what do leading edge cuffs increase?
CL-max and the camber of the wing
wat devices are cuffs?
aerodynamic devices
where do leading edge cuffs extend?
down and forward
fixed nature of leading edge cuffs extract a penalty in what?
maximum cruise airspeed
recent advances have reduced this penalty
what do slats prevent?
flow separation by suppling more energy to the boundary layer
what happens when the slat is deployed?
an increase in the camber of the wing
what is a slot?
fixed aerodynamic feature of the wing
reduces stall speeds and performance at low handling speeds
define a slot?
a spanwise gap in each wing allowing air to flow bellow the upper surface
what happens with slots at low AOA?
airflow through the slot is insufficient and contributes to drag
a leading edge slot can do what?
increase maximum coefficient of lift o an airfoil by 40%
what is a vortex gyrator?
metal projection on the wings surface
what are the shapes of vortex generators?
rectangular
arofoil shape
what do vortex generators do when placed correctly?
improve performance and controllability on the aircraft at low speeds and in climb at high AOA
what is the adverse pressure gradient?
air moves from low pressure to high pressure
high pressure losses energy until what?
until the airflow separates from the wing
wat air is not affected by skin friction?
air above the boundary layer
wat do vortex generators act like and what do they create?
act like mini wing tip vortices so spiral the free stream airflow
wat do vortex generators enable the wing to do?
enable wing tip to operate at higher AOA
wat are winglets?
small structs at the aircrafts wing
what do winglets do?
creates vortices at wing tip witch creates a lot of drag and turbulence
what is the simplest way to reduce induced drag?
increase the wing span
wat does increasing the wing span do?
generates more lift and thrust
what is the down side of a longer wing span?
weight penalty
fuel efficiency losses
wat is the solution t the problem on increasing the wingspan?
adding winglets which ensures the vortex of induced drag which is torn apart and distributed vertically
winglets generate lift in what direction?
perpendicular to relative wind
when a lift vector is drawn from the winglet the lift vector points where?
forward a little
what are the benefits of installing winglets on aircraft?
reduced fuel consumption
increased range
improved performance
lower emissions
