Flight theory Flashcards
What is a vector?
Magnitude + Direction
How do we add vectors?
F1 points to start of F2
Resultant force starts and tail of F1 and goes to head of F2
What are Newtons Laws
- Object will stay stationary, unless force is applied
- Object will move in direction of and proportional to force
- Every action has an equal and opposite reaction
Formula for Force and units?
F=MA
F = kg m/s2 = Newton
What is a moment?
Weight * Distance from a fixed point.
Units: Kg m
How do we calculate CG?
Calculate all moments using fixed Datum
Add all moments up ( kg m )
Divide by total weight ( kg )
CG is the distance from the Datum +/- the distance
What is density and the formula?
How much matter in a volume.
Measure as weight per cubic meter
m/v = kg/m3
ISO Standard measures?
-Pressure
-Temp
-Height measured at
15 c
1013.2 HPa
What is pressure and the measures?
Force exterted on each m2.
1 pascal = 1 Newton / m2
1 HPa = 100 Pascals
What is the formula for the general gas law?
Relationship between Pressure, Volume and Temp
P*V / T = constant
Pressure * Volume / Temp = constant
What is torque?
The angular version of linear force
Formula for CPF?
Centripedal Force
Centripetal Force =
m*v2 / r
Formula for Radial Acceleration?
v2/r
What is the total energy of Air?
Total Energy = Pressure Energy + Kinectic Energy
Ps + 1/2 sigma V2
What is the Chord Line and Mean Camber line in an Aerofoil
Chord
Line from front to back
Camber
Line equidistance from top and bottom.
These are equal if the aerofoil is symmetrical.
Forces for Lift on an Aerofoil?
Lift - at the Centre of Pressure. This is the sum of all of the pressure forces.
Operates at 90 degrees to Relative Wind
Drag - operates opposite to Relative wind
Center of Pressure moves forward as the angle of attack increases
What is the Total Reaction Force?
With regards to lift
Resultant Force = Lift - Drag
(Expressed as a VECTOR)
What happens to lift as AoA increases?
Increases Linierly, then reducing, then stall.
What is the aspect ratio AR?
The wing span to the mean chord
What is the formula for Lift?
Lift co-effiecent * 1/2p * v2 * S
1/2p = air density
v = velocity
s = surface area of the wing
What factors increase the Lift co-efficient?
The lift co-effeicient is not constant, but varies.
Shape of the wing
Angle of attack
How is the sweep angle of a wing calculated?
Angle between fuslage center of the wing compared to the 1/4 chord to the wing tip
What is the stagnation point?
Point at which the wind splits on the leading edge.
Describe the laminar air, boundary air, turbulent air and transition point
Boundary Air - air layer closest to the wing.
Laminar air - smooth air flowing over the wing
Turbulent air - not smooth air flowing over the wing
Transistion point - point on the between laminar and turbulent air
What the standard aerofoil shapes
What is the taper ratio for a wing?
Length of the tip / length of the root
Ct/Cr
What are the factors of Drag
What is the drag formula?
CD * 1/2p * v2 * S
CD - Co-efficent of drag
1/2p - air density
v2 - velocity squared
S - cross sectional surface area
What are the 4 factors for Profile Drag?
- Form Factor
- Cross Sectional
- Area
- Airflow speed
Interactions between parasite drag and induced drag
Parasite Drag - increases with Speed.
Induced Drag - decreases with Speed.
Therefore there is an optimal speed/AoA ( 4 - 5 degrees ) to maximise range.
What can be done to reduce Induced Drag?
Goal: Create elpictal lift. Done by
- Reduce wingtip vortexs
- Increase AR ( span to surface area ) - wider span = less induced drag
What does downwash do to the lift co-efficent?
( and how does downwash occur? )
Downwash is caused as the pressure equalises at the wingtips ( creating Vortexs )
It reduces the lift co-efficient, meaning a high AoA for the same life, meaning more drag.
For a light aircraft - what is ‘normal’ stall AoA and best cruise AoA
16 degrees
4 - 5 degrees
How do we estimate AoA in a light aircraft?
There is not an AoA indicator. Therefore the POH has recommended speeds.
Note: These are proxy, esp. Stall speed.
However they are good guidance for cruise, climb and glide speeds.
What is the formula for wing loading?
Weight / Area
What increases stall speed?
- Weight
- Load factor ( apparent weight )
This means that in straight and level the heavier the plane the higher the stall speed
What are the 2 stall speeds on the Airspeed Indicator?
Vs0 - bottom of white arc. Full landing config
Vs1 - bottom of the green arc. Cruise config
What is the most important factor with regards to stall speed?
Aerofoil shape. Dictates the stall angle of attack, and how gentle or abrupt the stall is.
What is the formula for load factor and stall speed increase
What is the most important part of the plane to keep free of ice/dirt?
The leading edge.
Ice buildup / dirt - will have the biggest impact on stall speed.
What is the impact of Slipstream on Stall Speed?
The stall speed will be lower, due to the airflow over the wing. Could be as much as 5 knts.
This is why a ‘bump of power’ on landing can prevent a hard landing… even if the plane does not actually go faster.
What is the power condition for the stall speed in the POH?
Idle. (as power will decrease stall speed )
Where do we want to the wing to stall first?
Why?
What shape should the wing be?
At the wing root, keeping the aerilons in undistured air. AND reducing wing drop
More rectangular wings will do this
AND
Twisting the tips
What is the load factor?
Relationship between weight and lift.
What is a spin ( and the cause ) ?
A yaw aggirvated stall.
Caused because the lower wing is slower than the upper - therefore stalls first
AND
The lower wing has more drag and is slower - therefore tendancy to increase
Why does the stall risk go up in a turn?
Two factors:
- Load factor increases, increasing stall speed
- The lower wing is going slower and has more drag.
Un-conordiated turns agreviate stall risk
What are the risk times for turns to cause stall/spin?
Turn on to final
Already low speed
May increase bank if overshoot
Valley turns
May increase bank angle
Way to avoid
- Use power when doing a turn
- Know how much space you have
What is the impact of stall speed with a 60 degree bank angle?
41%
Symptom of a stall?
- decreasing airspeed
- Possible nose high ( angle of attack )
- MAYBE stall warning
- Ariframe buffet or vibration
Spin recovery procedure?
P power close throttle
Identify you are in spin
A - Ailerons neutral
R - Rudder oposite spin.
E - Elevators slowly forward
S - Spin stops. Slowly pull out of dive and power back in
What are the phases of a spin?
Stall
Incipient Spin
Full developed Spin
Recovery
What is a graveyard spiral and recovery?
Not a spin.
Causes is because plane is not level and pulling back on yoke to recover just tighens the turn
Recovery
Power out
Aileron to level plane
WHEN LEVEL - Gently pull to recover from dive
Power back in.
Formula and rule of thumb to calculate turn radius
V2 / 11.26 * Tangent of Bank Angle
OR
1% of the airspeed will give the diameter with standard rate turn.
How do we find max endurance speed?
It is the lowest point on the power required.
High air density = better , so fly as a low as possible
How do we find max Range speed?
A tangent line is drawn from zero to the bottom point of the power required.
The point at which is crosses is the best TAS
Other considerations:
Lean to minimise fuel burn
Higher Altitude = less drag.
Winds
Therefore is it a winds / altitude trade-off
What is the formula for performance at all phases of flight
Power + Attitude = Performance
Means if the IAS fails OR the power fails we can still fly - use the other indicator
The altitude at which full power is only capable of sustaining level flight at one airspeed is called the
This is two words.. not performance ceiling
Absolute Ceiling
What is the thrust to drag formula for a climb?
T = D + RCW ( Rearward component of weight )
Lift is < Weight ( the plane is ‘driving’ upwards )
Where on the Power / TAS Graph is the Max ROC ( Rate of Climb)
This graph has the power needed and power available.
At the largest difference between power required and power available
How do the following affect Climb Performance?
Flaps
Weight
Wind
Flaps
reduces the rate and angle of climb
Weigh
Increases Rearward Component of Weight - therefore decreases rate and angle
Wind Headwind
Rate of Climb not affected vs tail wind
Angle increases
Ground Speed Reduced
How does do following affect Descents?
Flaps
Wind
Power
Flaps - increases Drag, therefore reduces range.
Wind - Headwind reduces range
Power - More power increases range
How does the Weight affect Descents?
More weight = same range.
BECAUSE
More weigh increases the forward componet of weight, meaning the glide path is flown faster.
How does L/D affect range in a descent?
Best L/D is achieved by fliying best glide speed.
Resulting in lowest angle of attack vs drag
What are CPF ( Centripedial Force) and CFF ( Centrifegual Force )
CPF is inwards force
CFF is outwards force
How do the forces work in a turn ( Weight and Lift )
VCL must be equal to Weight.
Due to the turn, we need to back stick
What is the load factor?
The lift needs to increase in a turn, due to the HCL
This results in an Weight force on an angle, called ‘G’
At what angle of bank will power be required to maintain altitude?
As drag increases, more power is required at 45 degrees to overcome the incresed drag.
Full power is required about 60 degrees… therefore max bank angle
Under / Over banking tendancies in a climbing/ descending turn
Outer wing is always travelling faster, therefore more lift.
In Climbing turn - results in overbanking tendancy.
In descending turn - inner wing has a higher angle of attack, so often cancel out. Depending on aircraft design, can result in underbanking tendancies.
What is a rate 1 turn?
How to calculate it?
3 degrees per second
Angle of bank = TAS /10 + 7
