Lesson 4 Flashcards
What is bad about drag?
Climb performance
Longer to take off
Increased fuel consumption
Range + endurance reduced
What is good about drag?
Helps to decelerate
Jet can operate at high power setting to make it more responsive
The lift / drag ratio is a good measure of aircraft ????
Efficiency
L/D max occurs at VMD which is approximately how many degrees?
4°
Lift = weight + ?????
Downforce
Downforce can be considered as extra???
weight
Doing what to the CG has the same effect as getting heavier
Moving it forward
Moving the centre of gravity forwards does what to the stall speed?
Increases the stall speed
Lowering the landing gear will create extra drag beneath the centre of gravity, what moment will this produce?
A pitch down a moment.
This has to be balanced with greater downforce from the stabiliser, effectively increasing weight and increasing stall speed.
A jet will cruise with it’s nose slightly up. What does this mean for the lift in relation to thrust?
What does this do to VS
the stall speed?
A component of thrust acts as lift as it cruises with 2° - 3° nose up.
VS is reduced as the wing isn’t working as hard.
An aircraft with puller props - will be able to generate more lift at higher thrust settings due to?
What does this do to VS
the stall speed?
Propwash over the aerofoil
VS is reduced as the wing isn’t working as hard.
An aircraft flying close to the stall VS attempts to roll right. It can cause low speed aileron reversal. Explain
Deflecting an aileron up reduced α locally on that wing.
If α is already close to αCRIT then α could push the high wing into a stall and the aircraft rolls in the opposite commanded direction.
Load factor is what expressed as a equation?
Load factor (n) = Lift⁄Weight
Describe an accelerated stall
Pulling accelerated G will lead to the stall speed increasing. This means stalling at an accelerated speed aka accelerated speed.
If Load factor (n) is greater than 1 then the wing is working harder? True/false
True
Another load factor equation, this one relates it to the stall??
n ∝ VS2
If both the wing and stabiliser are stalled it is known as a?
Deep stall
What’s bad about a deep stall?
Elevator can no longer be used to help with recovery.
What types of aircraft are prone to deep stalls?
T-tails
Swept wing
What preventative tool is used in aircraft prone to deep stalls?
Stick pusher
Contamination can increase VS, reduce αCRIT / CL MAX
What are examples of contamination?
Clear ice
Rime ice
Heavy rain
What is a premature stabiliser stall and what would it cause?
Stabilise stalls before the wing. This would cause a loss in downforce and a pitch down.
The stall speed and altitude:
Above Mach 0.4 VS starts climbing.
Why?
At lower altitude the ‘bow wave’ of the wing allows for a gentle deviation of the incoming air allowing it to bend up and over the aerofoil.
At the higher altitude, compressibility means that the wing sneaks up on the air and forces an abrupt deviation over the top of the aerofoil making it more of a challenge for the flow to be laminar.
What relationship describes stall speed and mass?
VS ∝ √ mass
Load factor does what in a turn?
Increases
What relationship describes load factor in a turn?
n =
1⁄cosθ
An aircraft reaches αCRIT and aileron’s are deflected (pilot attempting to roll wing level) describe the actions that follow resulting in a spin
One wing stalls more
Uneven drag create a yaw towards the low wing
Yaw has the high wing moving through the air faster so it will lift and create roll
Roll > yaw
Yaw > roll
etc.
etc.
Crash
What are the 3 parts of a spin?
Incipient spin
Fully developed spin
Recovery
“the first few rotations before the forces are fully balanced” describes?
Incipient spin
“In a spin, all forces are balanced” describes what?
Fully developed spin.
How would you recover from a spin?
Unload controls, throttle idle.
Establish direction of spin
Opposite rudder until spin stops
Pitch to recover from stall
Roll level
Recover to level flight and restore power
Turn indicator in a spin: NEEDLE points (not ball) in the direction of the spin. What does one do with this information?
Opposite rudder to the needle
VSW means?
And what is it greater than?
Stall warning speed
Greater than VS
What are the two types of stall warning?
Natural
Artificial
What are examples of natural stall warnings?
Control buffet
Sluggish unresponsive controls
difficult to maintain altitude
difficult to keep nose up
un-commanded roll
slow speed
Three examples of artificial stall warnings
Unique audio warning
Visual Indication (stall light)
Shaker to simulate a control buffet
How will a light aircraft tell the pilot about an approaching stall?
A flapper switch, sits beneath the stagnation point on the leading edge of the wing, as the stagnation point moves down below the flapper switch this triggers the switch and makes a sound in the cockpit
How will larger aircraft sense an oncoming stall?
Angle of attack probe
Angle of attack of vane
VSW will be how much faster than VS and VSR
5kt or 5% greater than VS
3kt or 3% greater than VSR
Extending flaps INITIALLY does what
Increases the downwash angle
this changes the AoA and RAF on the horizontal stabiliser.
Which increases the downforce.
Which causes the aircraft to pitch up
Which results in a balloon above the intended flight path.
Overall, what is the effect of extending the flaps?
CP moves aft causing pitch down moment.
Flaps are not for creating more ____
Lift
Flaps and slats mostly involve changing the wing ______
camber
Flaps allow us to create the ____ amount of ____ at a slower airspeed.
Flaps allow is to create the same amount of lift at a slower airspeed.
Describe a plain flap?
Hinged trailing edge
Increases camber
Does not increase surface area
Describe a split flap?
Hinged lower surface
No change in surface area
Large drag increase
Lots of turbulence
Describe a slotted flap?
Slot allows airflow from underside to pass through to the top. This re-energises the boundary layer, delaying separation.
Describe a fowler flap
Extends downwards and rearwards.
Can be slotted or un-slotted
Describe slats?
Leading edge protrudes forwards leaving a slot
No camber change
The slot re-energises the boundary layer, delaying separation.
Variable camber flap
Leading edge is dropped downwards
Increases camber
Increases leading edge radius
Describe kruger flap
Same purpose as variable camber but a bit worse (stalls earlier)
Useful for root when variable would be nearer the tip
Jammed asymmetric flaps would have what problems?
yaw towards the lower flap
roll away from lower flap
Likely to overcome the ability of the ailerons to compensate.
What is designed to stop asymmetric flaps
Brakes will physically clamp flap mechanisms if asymmetry is detected.
Ground effect _____ happen within 1 wingspan from the ground
could
Ground effect ____ happen within half a wingspan of the ground.
will
The closer the wing is to the ground, the greater the ground _______
effect
Which part of the lift formula can be swapped out for IAS?
IAS2 = 1⁄2 ρ V2
What is the drag formula?
Drag = Half density x velocity2 x Surface area x Coefficient of drag
D = 1⁄2 ρ V2 S CD
or
D = IAS2 S CD
What happens to ID (induced drag) when the speed of the aircraft doubles?
ID ∝ 1⁄V2
When the airstream velocity increases, the parasite drag increases by the square of the velocity increase.
So, if the airstream velocity increases by a factor of 4, the parasite drag will increase by a factor of (4^2), which is 16
