Principles of flight Flashcards
what is washout in a stall
reduction in angle of incidence from wing root to wing tip to ensure wing tip stalls first
1 reason ice accumulation can effect stall
1- ice on wings
cause a breakdown of streamline flow at angles of attack well below stall angle so stall at higher speeds
2nd reason ice accumulation can effect stall
- weight
increase in weight stall speed will be increased
How do flaps effect stall speed
flaps lower stall speed and are used in take off and landing.
with flaps wings will drop and their will be little to no indication of stall
What is blanking
turbulence over tail plane causes poor control from the elevator. Use a T-Tail to try and countreract
T-Tail stall
very high AofA with slow speeds. will enter a deep stall. When planes stall it will sink with a high angle of attack making stall impossible to recover form
What is a spin
when an aeroplane stalls it is followed by a spiral decent
how is a spin initiated
pilot will yaw plane prior to stall.
outer wing will speed up and more lift so will rise
inner wing will slow down less lift and so will drop
What is autorotation after the stall
when dropping wing is further stalled, aeroplane will roll a sideslip will develop and nose will drop, no correction and a controlled spin will occur
why shouldn’t you use aileron after a stall
it will roll you into a spin
weight of an aeroplane acts through
Centre of Gravity
wing loading equation
wing loading= weight of aeroplane/wing area
Bernoulli’s principle
anything in motion will have energy.
a fluid in motion have-
-static pressure energy
-dynamic pressure
Bernoulli said
for an ideal fluid total energy in a streamline flow remains constant
camber of a wing
is curvature
a well cambered aerofoil
slow speed high lift
angle of incidence
the angle the wing is fixed to the airframe
a thin cambered aerofoil
high speed
what happens to centre of pressure as angle of attack increased
moves forward
lift depends on
wing shape
angle of attack
air density
freestream velocity
wing surface area
angle of attack
chord line and the relative airflow
total reaction act through
centre of pressure
as angle of attack increases
lift from wing increases
In a 30 degrees bank turn you experience what load factor
1.15g
In a 60 degrees bank turn you experience what load factor
2g
in a 70 degree bank turn what load factor will be experienced
3g
in a 80 degree bank turn what load factor will be experienced
6g
if L/D ratio is greatest the glide distance is greatest. If l/d is 5/1 you will glide
5 times more
how does flap effect the lift to drag ratio
increases drag more than lift so lift to drag ratio is lowered. Steeper glide angle
what is a Vx climb
lowest speed. Steepest incline. used to clear obstacles- Max gradient speed
What is a Vy climb
reach altitude as quick as possible. Gains height in quickest amount of time
what is a cruise climb
high speed and height gain. Allows better forward visibility
Performance equation
power+attitude=performance
TAS
IAS
TAS= true airspeed and is relative to distance travelled through air
IAS=Indicated airspeed and is relative to aerodynamic effects such as lift and drag
lift operates through……
weight operates through……
….. centre of pressure
……centre of gravity
what is a slat
are part of leading edge of wind and can form slots for air to flow through to delay stalling to higher a of a
fowler flaps
move back and down, increasing wing area as well as camber
as air flows through a venturi tube
static pressure reduces as the tube narrows
critical angle
angle at which the laminar flow over wing breaks into eddies and separates
3 types of parasite drag
skin friction
form drag and
interference drag
skin friction drag
friction forces between an object and air it is travelling through causes skin friction drag
form drag
airflow separates from surface eddies formed and streamline flow is effected. increase drag
interference drag
the sum of all drag is greater than drag on one surface. this is due to interreference with with other surfaces such as wings and fuselage, creating additional drag
Parasite drag and airspeed
as airspeed increases so does parasite drag
Induced drag
by product of production of lift.
how is positive lift produces
static pressure on upper surface will be less than lower. As air flows rearward some airflow will spill or leak around wing tip from high to low static pressure above the wing
ways to reduce induced drag
- high aspect ratio wings(long narrow wings)
- tampered wings as they have weaker wingtip vortices so induced drag less
3.washout- wing built with an inbuilt twist
What is a washout to reduce induced drag
higher AofA the greater the pressure difference between upper and lower wing surfaces. If wing is built with inbuilt twist angle of attack at wing tip is less than at wing root. Therefore the pressure difference reduces leakage and therefore induced drag reduced
How to increase induced drag
- low airspeed high angle of attack
- more lift produced, more drag produced
DRag from aerofoil at low and high speeds
low speeds-high due to induced drag
high speeds-high due yo parasite drag
Total drag
sum of various forces of drag acting in opposite direction of flight
What is the blade angle
angle the chord line of the prop makes with the plane of rotation
Larger near root and smaller near tip
Slipstream effect in takeoff
prop will rotate clockwise.
this causes an asymmetric flow over the fin an rudder . high power the slipstream will impinge on left of fin, pushing tail right and yawing plane left.
Propeller torque reaction- take off effect
prop rotates clockwise, torque reaction will cause aircraft to rotate anti-clockwise and roll left
constant speed/fixed pitch prop
efficient over a range of rpm and speeds
variable pitch prop
can change blade angle
Thrust to drag produces a
pitch up
lift to weight produces a
pitch down motion
General Cp and CG positions
Cp is behind Cg normally
high stability=
harder to control
high controllability=
more unstable
3 reference axes
lateral
longitudinal
normal
longitudinal axis
rolling
lateral stability
Lateral axis
pitching
longitudinal stability
normal axis
yawing
directional stability
how Cg effects longitudinal stability
further forward the CG the more stable the plane is
directional stability
ability for plane to recover from a disturbance in the yawing of the plane. ability for the plane to weathercock its nose into any cross wind
lateral stability
natural ability for plane to recover from a disturbance in roll
what is wing dihedral
wings of plane are inclined upwards from fuselage to wing tips to improve stability in low wing aircrafts
what is wing sweepback
wings point backwards /\
CP in front of CG a …… couple is produced so tail plane produce a ….. force
nose up
upwards
effectiveness of controls is achieved
at high speeds
Primary focus of flaps
increase lifting ability
effects of drag-
- increased lift
- pitch attitude change- CofP move back
3.decrease lift/drag ratio(plane will not glide as far with flap)
4.increased drag
5.lower stall angle of attack
6.lower stalling speed
7.
flaps in take off
lower stall speed.
produce more lift at slower speeds
increased drag so lower angle of attack
wing load equation
weight of aeroplane/wing area
streamline flow
molecules follow the same steady path
turbulant flow
molecules do not follow the perfect streamline flow, as boundary layer seperates from surface
kinetic energy=
1/2 x mass x velocity squared
dynamic pressure=
1/2 x rho x velocity squared
what happens to CofP when aeroplane stalls
CofP far forward
faster aircraft wing is less or more curved
Less curved
disadvantages of laminar flow
stall at higher speed and lower stalling angle
what is a vortex
twisting flow of air
relationship between AofA and weigh
angle of attack decrease is same as weight decreasing
how to reduce lift at same Aof A
reduce airspeed
how height effects TAS and IAS
higher you go true airspeed increases
but
IAS remains the same
Prop sections
near hub blade must be hick and strong
at tip of prop they will be tip vortices which air spills around from high to low pressure.
Only small part of prop is effective 60-90% tip radius
if lift behind weight nose….
if weight behind lift nose…
……down
…….up
drag above thrust nose….
thrust above drag…..
…….down
……..up
static stability
energy unable to move it will remain stationary
how many ft in 1 nm
6080
what provide roll stability
- washout
2.stall strips
3.vortex generators
what are leading edge lift devices
- slats
2.slots
What is a slip in relation to a prop
The difference between Geometric Pitch and Effective Pitch
what is aileron drag
aircraft will yaw towards up going wing and wing with aileron will deflect downwards
what is aerodynamic drag
a force of drag which operates in the opposite direction of motion
what does mass balance do
help reduce flutter at high speeds and control at low speeds
how to work out stall speed from a speed and degree
original speed X root (1/cos(degree)
how a stall warner works
the stagnation point moves down the leading edge o indicate low pressure
roll of a spoliler
to reduce lift
effect of drag in a decent
increase in drag increases rate of decent
as altitude increases what happens to static and dynamic pressure
dynamic-remains constant
static- decreases
as critical angle of attack reached,
lift reduces and drag increases
what do frise ailerons do
counteract adverse aileron yaw by introducing the lower leading edge of the aileron into the airflow beneath the aerofoil
What could be a cause of “buffet”
When a wing approaches the stalling angle of attack, the separated airflow above the wing is encountered by the tail surfaces of the aircraft
For a conventional sub-sonic airflow through a venturi tube:
static pressure reduces in converging section to create kinetic energy
3 factors nor included in the Coefficient of lift is
air density
freestream air velocity
wing SA
chord line
straight line joining the ends of the mean camber line
mean camber line
line drawn half way between upper and lower surface
an airplane leaving ground effect will experience
an increase in induced drag and increase in thrust
in a turn altitude must be kept due to
loss of vertical component of lift
lift is defined as
force acting perpendicular to the relative wind
force of lift acts ….
force of drag acts…
…perpendicular to airflow
……..parallel to flight path
to experience same force of ground effect airplane need a ….. angle of attack
….lower
when does p-factor cause plane to yaw left
when at high angles of attack
how is flutter avoided
moving center of gravity of control column towards hinge line
effect of tail wind on climb
degrade climb
effect of headwind on glide
reduce glide distance over ground
30 degree angle
7%
45 degree angle
19%
60 degree angle
41%
