11.1 Theory of flight Flashcards
what are the 3 primary axis
lateral, longitudinal, vertical
what are the 3 movements along the axis’s
pitch, roll, yaw
at what angle do all the axis intersect
90 degrees
where is the lateral axis on the aircraft
wing tip to wing tip
where is the longitudinal axis on the aircraft
nose to tail
where is the vertical axis on the aircraft
runs through aircrafts centre of gravity
what are the 3 primary flight controls
ailerons, elevators, rudder
on larger aircraft what flight controls are added
roll spoilers
what control an aircrafts roll?
ailerons and spoilers
if an aircraft is rolled to the right what do the ailerons do
right aileron up, left aileron down
what ailerons are used during high speed flight
inboard
if an aileron goes down does it increase or decrease lift?
increase
what’s the equation to calculate dynamic energy
1/2 x density x airspeed(2)
at low speed flight what ailerons are used
both inboard and outboard
what controls an aircrafts pitch
elevators, stabilators, variable incidence stabiliser, canards
what are the elevators furthest away from the centre of gravity
greatest leverage
do the ailerons operate in the same direction
no
do the elevators operate in the same direction
yes
what is a variable incidence stabiliser used for
pitch trimming
when the variable incidence stabilisers are used what can the compensate for
passenger weight, freight, fuel loads, engine settings
where are the wings located on an aircraft when canards are used
front of aircraft
what controls yaw on an aircraft
rudder
what is used to prevent the pilot over stressing the rudder during flight
rudder limiter
when is the rudder only used independently
correct direction of aircraft in crosswind or when a single engine fails
what is used to move the elevators
screwjack
what are the names of the two, duel purpose flight controls
elevons, ruddervators
what makes up elevons
elevators, ailerons
what makes up ruddervators
elevators, rudder
where are elevons usually used
high performance, military aircraft
what’s a common example of an aircraft with ruddervators
v - tail
what are the 3 common high lift devices
slots, slats, flaps
what do slots allow the aircraft to do in terms of speed
fly at slower speed and high angle of attack
whats a disadvantage of slots
produce a lot of drag
are flaps secondary or primary flight controls
secondary
what does the flap do to the wings shape
increase its camber
what are all the types of flap (7)
plain flap, split flap, slotted flap, fowler flap, slotted fowler flap, krueger flaps, flaperons
how much lift does a plain flap produce
50-55%
how much does a split flap increase lift by?
60-65%
how much does a slotted flap increase lift by
65-70%
how much does a fowler flap increase lift by
95%
whats the difference between a slotted fowler flap and fowler flaps
slotted fowler flaps have a gap between the trailing edge and leading edge of the flap to re-energise the boundary layer
what flaps do some heavy aircraft have
leading edge flap
what can krueger flaps increase in the aircrafts handling
low speed handling
what is a flaperon
an aileron that can also function as a flap
what are the 2 main induced drag devices on modern aircraft
spoilers, speed brakes
where are spoilers located on the wing
upper surface
what can be the 3 distinct spoiler functions
flight spoilers, ground spoilers, roll spoilers
what are roll spoilers used in conjunction with
ailerons
where are speed breaks positioned on aircraft
on structural areas strong enough to withstand high air loads
what do wing fences do
reduce the effect of spanwise flow and reduce wing tip stall
what is the direction of the flow in spanwise flow
along the leading edge
whats the ideal direction of the wind over wing
right angle to leading edge
what is a saw tooth leading edge and what does it prevent
slight extension on the leading edge and reduces wing tip stall
what is the purpose of a vortex generator
re-energises the boundary layer
what is the purpose of stall wedges
to ensure the wing root will stall before the wing tip
whats the shape of the cross section of stall wedges
triangular
what duct do all high lift devices have and why
convergent duct to accelerate airflow from lower to upper surface
are trim tabs a primary or secondary flight control
secondary
what is the purpose of trim tabs
compensate for aircrafts imbalances
what are the 2 types of trim tab
fixed and moveable
whats the difference between fixed and moveable trim tabs
fixed can only be adjusted on the ground, moveable can be adjusted in the air
what direction does the trim tab go
opposite to the flight control
what is the purpose of a balance tab
to assist the pilot in moving a flight control
what direction does a balance tab go in comparison to the flight control
opposite
what direction does the anti balance tab go in comparison to the flight control
same direction
what aircraft are servo tabs used on
large aircraft
what is the purpose of a servo tab
make it easier to move the flight control for the pilot
what is linked with mass balancing
aircrafts centre of gravity and centre of pressure
what is a balance panel
plate connected to the leading edge of the control surface
what do balance panels divide the front of the control surface into
upper chamber, lower chamber
what is the speed of sound
mach 1
what are the 3 speed regions
subsonic, transonic, supersonic
whats the compressible flow speed at subsonic
0.8 mach or less
whats the compressible flow speed at transonic
0.8 - 1.2 mach
whats the compressible flow at supersonic
1.2 - 5 mach
what speed do most modern aircraft operate at
subsonic
if an aircraft is traveling at transonic speed what speed is the airflow on the aircraft
subsonic and supersonic
when traveling at supersonic what is the speed of all the airflow around the aircraft
all supersonic
if an aircraft is flying at the same speed as sound whats its mach number
1
if an aircraft is at 0.6 mach what percentage of sound is it flying at
60%
what is the critical mach number
lowest mach number at which airflow over some points of the aircraft reaches the speed of sound but not exceed it
what mach number is air considered compressible at
0.4 mach
what creates a shock wave
air being disturbed due to the aircraft going through it
if an aircraft is going faster than the speed of sound where is the shockwave
behind the aircraft
are expansion waves shock waves
no
when are expansion waves formed
supersonic airflow changes direction over a curve or corner
what are the 2 typical supersonic wing profiles
double wedge, circular arc
what is wave drag
portion of total drag which is caused from shock waves
what 2 ways can help reduce wave drag
vortex generators, applying the area rule
whats the slight disadvantage of vortex generators when reducing weave drag
introduces slight parasite drag
describe the area rule briefly
changing certain areas on the aircraft where shockwaves are most common
what can aerodynamic heating also be known as
friction heating
what happens to temperature during supersonic flight
increases alot
for a supersonic aircraft what must the airflow be slowed to when entering the compressor
subsonic
gas turbines cannot take in airflow speeds above what
0.4 mach
how does a normal shock diffuser inlet slow air velocity
using a normal shock wave
in a converging duct does velocity increase or decrease
increases
in a converging duct does static pressure increase or decrease
decrease
what happens to static pressure and velocity in a convergent duct
velocity decrease, static pressure increase
how does a single/multiple oblique shock inlet slow air velocity
external oblique shock wave
if multiple oblique shock waves are used to slow air velocity what are its advantages
less wasted energy and highest pressure recovery
what does a variable supersonic inlet provide
optimum efficiency at all airspeeds and angles
at flight speeds below mach 1 is the supersonic inlet open or closed
fully open
at flight speeds slightly above mach 1 how do supersonic inlets slow the air
slight panel angle change creating a normal shockwave
at flight speed of high mach numbers how does a supersonic inlet slow the airspeed
inlet adjusts to create 3 oblique shock waves and then a normal shockwave
how do we reduce the profile thickness of the wing and delay the critical mach number
swept back wings
whats the most common swept wing angle on modern jet aircrfat
30 degrees
if the centre of pressure is forward of the centre on gravity what risk is increased
stall risk
