Manual of Standards Flashcards
What is aerofoil span?
Distance from Wingtip to Wingtip
What is Chord?
Straight line joining leading edge to trailing edge
What is Chamber?
- Camber is the curvature of the wing
- Increasing Camber on upper surface causes the airflow to accelerate and generate more lift
- Distance between mean camber line and chord line
- Position of greatest camber is usually 30% back from leading edge
What is Thickness/Chord ratio?
- Describes the relative thickness
- A thick wing that is well cambered is ideal for high lift at low speeds
What is Relative airflow?
-Relative motion between body and remote airflow
What is Angle of Attack?
-The angle between the chord line and relative airflow
What is Laminar?
- Smooth airflow
- Persists while the aerofoil is thickening
What is Turbulent Boundary Layer?
- At max thickness there is an abrupt change in boundary layer
- Chaotic tumbling airflow
- Produces more drag then laminar
How does Chamber effect Lift?
Increased camber creates a faster airflow over upper surface; increasing lift production
How does Thickness/Chord Ratio effect Lift?
-A thick wing that is well cambered is ideal for lift production at low speeds
How does Relative airflow effect Lift?
Tilting the wing upward (or increasing the angle of attack) increases lift—to a point—but decreases airspeed. If you tilt it too much, the airflow pulls away from the upper surface, and the smooth flow turns turbulent. The wing suddenly loses lift, a condition known as a stall. You can reestablish a smooth airflow by tilting the wing back to a more level position. Tilting the wing downward (or decreasing the angle of attack) decreases lift, but increases airspeed.
How does Angle Of Attack effect Lift?
-Increased AOA= Increased lift
Up to 16 degree AOA or stall angle
How does Laminar effect Lift?
-Loss of laminar= reduction in lift snd increased drag
How does Turbulent Boundary Layer effect Lift?
The effects of the boundary layer on lift are contained in the lift coefficient
How does Chamber effect Drag?
An efficient camber reduces the effect of drag, a force that acts against thrust. … Thus, lift is easier to generate and maintain with an efficient camber. In contrast, an inefficient camber results in a wing with a great deal of drag; more thrust is needed to compensate for the increased drag.
How does Thickness/Chord Ratio effect Drag?
In order to reduce wave drag, wings should have the minimum curvature possible while still generating the required amount of lift. … For this reason, it is common for wings to taper their chord towards the tips, keeping the thickness-to-chord ratio close to constant, this also reduces induced drag at lower speeds.
How does Angle Of Attack effect Drag?
-As angle of attack increases drag continues to increase
How does Laminar effect Drag?
Drag force is proportional to the velocity for a laminar flow and the squared velocity for a turbulent flow. Even though the ultimate cause of a drag is viscous friction, the turbulent drag is independent of viscosity. Drag forces always decrease fluid velocity relative to the solid object in the fluid’s path.
How does Turbulent Boundary Layer effect Drag?
turbulent boundary layer is said to have a much steeper speed gradient at the aircraft skin, causing much more friction drag
What are the different types of drag?
Total Drag: Is the total of various drag forces acting on aircraft
Most of total drag is induced drag
Induced Drag: Associated with the production of lift
Parasite Drag: Including skin friction and Form drag
What is the effect on total drag from changes in IAS?
As speed increase Parasite drag increases
-Doubling speed gives four times the amount of parasite drag
As speed Increases Induced drag decreases
What is the effect on total drag from changes in Weight?
Less weight= Less Drag
More weight= More drag
What is the effect on total drag from changes in Height?
For a given IAS the associated TAS will be higher if altitude increases. Therefore the same drag at high altitude will be accompanied by a higher TAS
Use Bernoulli’s theory to describe how an aerofoil produces lift
Areas of increase velocity= a reduction in pressure
The area above the aerofoil is an area of low pressure whilst the pressure under the wing has a higher pressure which creates lift
Bernoulli’s Theory:
- Kinetic energy (Dynamic Pressure)
- Potential Energy (Static Pressure)
Pressure energy (Static)+ Kinetic Energy (Dynamic)= Constant Total energy
If static decreases then the velocity of air (dynamic) must increase
What is the Coanda theory?
Airflow seeks to remain attached to surface (entrainment)
Air flows over the surface and is then deflected downwards
=Total reaction
How does Coanda theory effect lift production?
The equal and opposite reaction of the wing creates a pressure difference between the top and bottom surfaces this is called total reaction and gives way to lift drag forces
In relation to Power available/ Power required curves Label speeds for: -Range -Endurance -Best Rate of Climb -Best Angle of Climb
- First-line: Endurance +Min Power
- Second-line: Range + Max Rate + Max Surplus power
- Third line: Max possible speed
Best angle depends on thrust
What is the lift formula?
Lift=CL 1/2 PV^2S
What is CL in the Lift Formula?
- Measure of lifting ability of the wing
- Depends on shape, section and Angle of Attack
What is 1/2 PV^2 in the Lift Formula?
Represents kinetic energy possesed by unit volume of air
- Density
- The velocity of relative airflow
In cockpit: IAS
What is S in the Lift Formula?
-A bigger wing= More lift
Area of Wing represented by S
Steady level Flight:
- Lift
- Weight
- Thrust
- Drag
Lift:
- Changes with flap, airspeed and AoA
- Lifting force caused by difference in static pressure above and below surface of wing that is at a right angle to the relative airflow and acts through centre of pressure.
- AOA changes postion of CoP
Weight:
-Gravitational forces that act down through Centre of Gravity
Thrust:
-Acts through prop shaft
Drag:
- Changes with AOA, configuration and airspeed
- Resists motion of aircraft
- Parallel to airflow
- The opposite direction of flight path
Lift and weight must be equal
Thrust and Drag must be equal
- Lift and weight will only decrease with fuel burn
- Thrust and drag will depend on airspeed and AOA
Steady Climb:
- Lift
- Weight
- Thrust
- Drag
- Achieved by increasing thrust beyond what is necessary for level flight opposing drag
- Lift acts perpendicular to the flight path (Lift = Less than Weight)
- Weight acts vertically (Some in direction of drag)
- Need to supply enough thrust to overcome the drag and the effect of weight in drag direction
- Lift only needs to equal component of weight perpendicular to flight path; less than level flight
Steady Descent:
- Lift
- Weight
- Thrust
- Drag
-No thrust if gliding
Balanced Level turn:
- Lift
- Weight
- Thrust
- Drag
- Horizontal force of lift provides the centripetal force that pushes aircraft into turn
- Lift force balances weight of aircraft
- Need backpressure
- Steeper the turn the greater the lift force required
Why would you fly max range?
When you need to get the most distance out of the fuel you have onboard
Why would you fly max endurance?
When you need to spend the most time in the air possible
-Think: searching for someone in the same location, don’t need to get far just need to remain in the air a long time
Effect of change in H/W on Range?
- Any Headwind will reduces range
- To achieve best range in headwind fly faster then min drag
Effect of change in T/W on Range?
- Any tailwind will increase range
- In tailwind fly slower then min drag speed
Effect of change in H/W on Endurance?
-Wind has no effect on Endurance
Effect of change in T/W on Endurance?
-Wind has no effect on Endurance
Aerodynamic and Engine considerations to acheive:
-Max still Air Range
-Max Endurance
When operating Normally aspirated engine?
Max range
- Min drag
- Full throttle height
- Best lift/drag ratio
Max Endurance
- Lowest altitude
- Min power
Aerodynamic and Engine considerations to acheive:
-Max still Air Range
-Max Endurance
When operating Turbocharged/ Supercharged engine?
Max Endurance
- Fly at lowest height
- Engine at Best economy
Max range
- Range increased at full throttle height from turbocharger
- Full throttle height will be at much higher altitude
On Power required/ Power available curve label:
- Best still air range speed
- Best endurance speed
- Max level flight speed
X
Effect of changes in Angle of Attack up to stalling angle on:
-Pressure changes above and below aerofoil
- As AOA increases minimum pressure on top of wing becomes less and creates more lift until stalling angle
- As AOA increases; centre of pressure moves forward
Effect of changes in Angle of Attack up to stalling angle on:
-Changes in airflow characteristics streamlined to turbulent
-As AOA increases air finds it increasingly difficult to stick to curvature and eventually separates into turbulent chaotic flow preventing any further increase in lift
Effect of changes in Angle of Attack up to stalling angle on:
-Lift and Drag
- Increase AOA= Increased lift until stalling angle
- Increases AOA= Continual Drag increase
Effect of changes in Angle of Attack up to stalling angle on:
-The Boundary layer
-As AOA increases to stall angle the boundary layer separates
Identify angle of attack on Coeffiecnt of Lift/Drag graph associated with:
-Minimum drag: max level flight speed
X
Identify angle of attack on Coeffiecnt of Lift/Drag graph associated with:
-Max Lift: Stalling Angle
X
Identify angle of attack on Coeffiecnt of Lift/Drag graph associated with:
-Best CL/CD: Best glide and still air range
X
Purpose of Anhedral?
- Negative dihedral
- Downward angle of wing
- Decreases lateral stability
- Often used in large aircraft with sweepback to counter excessive stability
Purpose of Dihedral?
- Upward angle of wing
- Used to increase lateral stability
Purpose of Aspect Ratio?
- Ratio of length of wing to average chord
- High aspect ratio wings (Long and thin) are used for gliders as they produce the best lift drag ratio at low IAS
Purpose of Sweepback?
- Angle at which wing is angled rearwards
- Delays onset of shock waves and allows cruise at higher Mach numbers
Purpose of Washout?
- Wing is twisted so that the angle of incidence of wingtip is less than wing root
- Most lift is generated at root and less near the wingtips
- Allows aileron control in stall
- Reduces induced drag
Purpose of Wing Spoilers?
- plate like surfaces that are hinged to protrude from mid to upper surface of wing
- Raised into airflow; decreasing the lift and increasing drag
- Assists rolling moment
- Offsets yawing moment
- Used to steapen approach
- Increase weight on mainwheels during landing to improve braking
- Used to prevent unwanted lift close to the ground
- Also used as speed brakes
Purpose of Flaps?
- Modify camber and area of wing and lift Coefficient
- Generate more lift at slower speed
- Reduces stall speed
- Steepens approach
Purpose of Voretx generators?
- Perturde vertical on upper wing surface
- Designed to introduce turbulance to boundary layer to maintian attached airflow over aerofoil
Purpose of Trim Tabs?
- Attached to trailing edge of control surface
- Apply specific loading on control surface
- remove the need for pilot input
During a balanced level turn:
- Speed
- Bank Angle
- Radius
- Rate of Turn
- Rate of turn is proportional to bank angle and inversely proportional to TAS
- Max rate is achieved by max bank and min speed
- Radius of turn is proportional to the square of TAS and inversely proportional to bank
- Min radius is achieved by lowest TAS and max bank
For given IAS determine approx. Angle of Bank to acheive Rate 1 Turn (360 in 2min)
Airspeed/10 +7
Example:
120 kts
120/10 +7 = 19 Degrees
Why must power be applied to maintain speed in level turn?
- Vertical component of lift must support weight
- Additional lift is required meaning an increase in speed or AOA
Why does an aeroplane tend to overbank in level and climbing turns but not in descending turns?
- Outer wing travels faster then inside wing and therefore produces more lift causing it to overbank
- In descending turns the inner wing has a higher AOA which produces more lift and neutralises over banking tendency
What is the effect of aileron drag on turn perfromance at low speed?
During the operation of the ailerons the wing of the down going aileron increases it’s lift coefficient and also the drag coefficient. Since the lift coefficient on the wing of the up going aileron decreases so does the drag, resulting in greater drag on wing which rises which pulls it backwards resulting in yaw opposite to the direction of roll. To counteract the yaw rudder must be added, however these deflected control surfaces create extra drag and result in a loss of airspeed. Aileron drag can be offset with frise ailerons or differential ailerons.
How do Frise Ailerons offset drag?
- Leading-edge of upward aileron protrudes beneath the lower surface and increase the drag on that side
- When aileron is deflected down the wedge nose hinges up out of the airflow
- When aileron is deflected up it hinges down and produces additional parasite drag
- Reduces need for extra rudder deflection by evening up drag
- Total drag is reduced
How do Differntial Ailerons offset drag?
- Counter adverse yaw
- The issue with drag is when it isn’t even
- Full extent of downward travel is much less then upward travel
- Drag caused by downgoing aileron is induced drag
- By extending upgoing aileron more parasite drag is produced
On Power required/ Power available graph label;
-Stall speed (Power on)
X
On Power required/ Power available graph label;
-Region of reverse command
X
What situation would result in aircraft exceeding load factor?
-Pull up from dive
-90 degree bank turn
-Spiral dive
Specifically in rough turbulent air
What situation would result in aircraft exceeding wing loading limits?
- Small wing area
- High weight
- Excessive load factor
What is load factor?
Total acceleration expressed as a ratio to straight n level
Lift/Weight
What is Wing loading?
-Loading that wing can support
Max weight of aircraft/Total area of the mainplane
What is G?
The force of gravity on the planet
Effect of changing weight and altitude on:
-Angle of Attack
-Increase weight= Increase AOA
Effect of changing weight and altitude on:
-IAS
-Increase weight= Increased IAS
Effect of changing weight and altitude on:
-Level Flight Range
-Increased weight= Decreased Range
(Due to: Heavy aircraft requires more lift, speed required is higher, drag is greater, thrust required increases, more power is required= increase in fuel flow)
-Height has very little effect on range
-Operate at full throttle height so engine can perform at best efficiency
Effect of changing weight and altitude on:
-Level Flight Endurance
-Increased weight= Decreased weight
(Due to: More weight= More lift and drag= More power= Higher fuel Flow)
-Best endurance is as low as posisble
-Height increase= Endurance decrease
Effect of changing weight and altitude on:
-Rate of Turn
- Weight has no effect on rate of Turn
- Height has no effect
Effect of changing weight and altitude on:
-Radius of Turn
- Weight has no effect on radius of turn
- Height has no effect
Effect of changing weight and altitude on:
-Glide Range
- Weight does not effect glide range as long as we select the correct speed
- Height has no effect
Range is Distance
Effect of changing weight and altitude on:
-Glide Endurance
- Increases in weight will reduce glide endurance
- Height will effect gliding endurance
Endurance is TIME
Effect of changing Power on:
-Turn Rate
For constant bank; rate of turn decreases with speed increase
For constant speed; rate of turn increases as bank increases
Effect of changing Power on:
-Turn Radius
For constant bank; radius of turn increases as speed increases
For constant speed; radius of turn decreases as bank increases
How does energy state of aircraft change with changes in altitude and airspeed?
Use the throttle to control total energy and the elevator to control the distribution of energy between altitude and airspeed. … When the throttle increases thrust above drag, the airplane gains total energy, and when the throttle reduces thrust below drag, the airplane loses total energy
Increased altitude= decreased perfromance
How does Position of CG effect longitudindal stability?
- Further forward the CG is the stronger the longitudinal stability
- Aft CG= reduced longitudinal stability
How does movement of centre of pressure effect longitudindal stability?
Aft COP= Increase longitudinal stability
How does changes in thrust effect longitudindal stability?
Increased thrust= Decreased airspeed stability= Decreased longitudinal stability as it produces a nose-up force
How does tailplane movement effect longitudindal stability?
- Tailplane assists longitudinal stability
- Tailplanes provide the restoring force
- Depends on distance from Cog and area of the tailplane
- Tailplane further from cog= strong stabilising moment
How does High vs. Low wings effect Lateral Stability?
- High wing has a greater lateral stability
- The horizontal component of lift will act to produce sideslip
How does Dihedral Vs. Anhedral effect Lateral Stability?
- Dihedral enhances lateral stability; in the event of a wing drop the aircraft will instead yaw stopping wing drop and returning to level flight
- Anhedral is negative dihedral; acts to take away lateral stability
How does Sweepback effect Lateral Stability?
- Improves lateral stability
- May require anhedral to reduce some stability
- If a wing drops; side slip occurs however relative airflow approaches from the direction of sideslip, effective span of lower wing is increased while higher wing is reduced=
How does large fore/aft displacement of CG effect Directional stability?
A forward CG provides stronger directional stability and gives a longer moment arm for the fin.
How does large vs small fin and rudder moment effect Directional stability?
The larger the area and further away from the centre of gravity the stronger the stabilising moment
What is the relationship between directional and lateral stability?
Lateral stability is weaker then directional stability
Could produce aircraft opposite but it would be extremely difficult to fly even though it wouldn’t have spiral instability
What is the effect of spiral instability on the control of the aeroplane?
- Lateral stability will attempt to roll the aircraft back to level and DIrectional stability will attempt to yaw the nose in the direction of airflow BUT
- Lateral stability is much weaker and directional stability will dominate and without corrective action in a wing drop directional stability will produce yaw in the direction of sideslip.
in the yaw the outside wing will accelerate; increasing lift and worsening the wing drop
What is static stability? (With diagrams)
- Forces to prevent any further displacement
- The object moves back to original position
What is dynamic stability? (With diagrams)
- Oscillations
- Pendulum
What are the controllability problems associated with flight in the region of reverse command?
-Power required to prevent a continuous drop in speed
Purpose of Trim Tabs?
-Removes stick force for a set angle of attack and power setting
Purpose of Balance Tabs?
- Used to lighten up control feel
- If the elevator moves up, the tab moves down
Purpose of Anti-Balance tabs?
-Resists the surface movement, increasing the pressure required
Purpose of Aerodynamic Balance?
- Helps to assist pilot when force to deflect surface becomes too great.
- The horn balance works by protruding into the opposite airflow to assist the movement
Purpose of Mass Balance?
- Assists in minimising control surface oscillations and flutter
- Weight is attached to the control surface to bring the centre of gravity closer to the hinge
Functions of items in relation to moevement of main control surface?
- Trim Tabs
- Balance Tabs
- AntiBalance Tabs
- Aerodynamic Balance
- Mass Balance
Trim Tab: Elevator, Rudder, Aileron
-If you want the right-wing down you push the right trim down
-Tab down wing down (Aileron)
-Tab left Tail left (Rudder)
Trim in the direction you want the slip and skid ball to move
Balance Tabs/ Servo Tabs: Elevator
- Reduces heavy feeling
- Elevator up: Tab moves down
Antibalance Tabs: Elevator
- Resists control surface movement to make controls heavier to move
- Moves in same direction as elevator
Aerodynamic Balance: Elevator or rudder
- Horn balance on tailplane
- Assists pilot by moving opposite direction of control surface to apply pressure from airflow
Mass Balance: Elevator, Rudder, Aileron
-Weight attached to control surface
Stability and control characteristics of nose wheel aeroplanes during ground operation?
- Better visibility
- Directional control is not hard as the main wheel is controlled by rudders
- Less weathercocking then tailwheel aircraft
- Wheelbarrowing in nose wheel aircraft
Effect of Propeller torque on Controllability?
- There is a force trying to rotate the aircraft in the opposite direction of the prop rotation
- If the prop is rotated clockwise the tendency will be to move the aircraft anticlockwise and roll to the left
Effect of Slipstream effect on Controllability?
- Prop rotation causes a clockwise rotating slipstream over aircraft; this causes an asymmetric flow to the fin and rudder hitting the left side pushing the tail to the right and yawing the nose to the left
- Some aircraft have an offset fin to overcome the effect
- Pilot will need to manage this with rudder
Effect of Gyroscopic effect on Controllability?
-When in a tailwheel aircraft; when you lift the tail wheel off the ground the nose-down pitching moment will be altered to a yaw to the Right in a clockwise rotating prop
Effect of Asymmetric blade effect on Controllability?
- A yawing moment caused at high angles of attack when the downgoing blade prop blade is at a higher angle of attack and generates more thrust.
- Aircraft will yaw in to the left if the prop spings clockwise
- The higher the power and lower the airspeed the more correcting rudder required
What is ground effect?
A reduction in induced drag and a change in pressure
How does ground effect; effect aeroplane performance?
- Noticeable at height One wingspan above ground
- Changes pressure distribution
- Reduces induced drag
- After leaving ground effect induced drag increases, nose pitchs up and there is a loss in longitudinal stability
Symptoms of approaching stall?
- Reducing airspeed
- Nose down pitch
- Oscillations
- Possible wing drop and Yaw
- Buffet
Characteristics of a stall?
- Sinking
- Rearwards movement of centre of pressure
- Nose drop
What is the effect of using aileron when approaching and during a stall?
- Ailerons can cause the wing to stall early; the lower wing will increase its AOA and stall causing a wing drop
- AIleron will cause the wing to stall more on oneside and stops the wing from stalling root to tip; which is the safest optionn
Why does an aeroplane stall at different speeds?
Because the stall happens at a particular Angle of Attack not airspeed and many factors can change the stall spees
Effect of Power on Level Flight Stall IAS
- Increase
- Decrease
- Nil
- Increase power= Stall IAS decreases; Thrust acts to assist lift, amount of lift required from wings decreases
- Decrease Power= Stall IAS Increases
Effect of Flap on Level Flight Stall IAS
- Increase
- Decrease
- Nil
- Flaps extended= Lowest stall IAS; Flaps increase lift coefficient
- Flaps retracted= Higher stall IAS
Effect of Windshear/ Vertical Gusts on Level Flight Stall IAS
- Increase
- Decrease
- Nil
- Increases gusts etc= accelerated stall due to load factor
- When an H/W chanegs to X/W or T/W the moemntary loss of airspeed can cause stall
Effect of Manoeuvres on Level Flight Stall IAS
- Increase
- Decrease
- Nil
-Increasing Load factor= Increase in IAS of stall
Effect of Weight on Level Flight Stall IAS
- Increase
- Decrease
- Nil
- Increase weight= Necessary lift increases, Higher IAS required for given AOA and stall occurs at higher IAS
- Decrease Weight= Lower IAS
Effect of Frost/Ice on Level Flight Stall IAS
- Increase
- Decrease
- Nil
-Ice present= Higher stall IAS
Effect of Altitude on Level Flight Stall IAS
- Increase
- Decrease
- Nil
Stalling IAS remains the same at all altitudes
Aerodynamic principles of stall recovery?
- Lower the nose: Reduce stall AOA
- Full Power: Increase airspeed
Ideally the stall should start near the wing root; and progress out to tip
*
Which manoeuvres may a plane stall at an angle which appears to be different to true stalling angle?
- If the load factor is more then 1G the stall speed is increased
- Bank turns increase stalling speed significantly
Difference between spin and spiral?
- In spin wings are stalled; in spiral they arent
- In spin airspeed is low and constant
- In spiral airspeed is high and rapidly increasing
- In a spin loads on airframe are modest
- In spiral loads on airframe are dangerously high
Recovery technique for Spin?
Power off
Opposite rudder
Forward stick to unstall wings
Recovery technique for Spiral?
Power off
Locate horizon
Level Wings
Return nose to level
Sudden H/W gust on final what happens to ROD?
Decreases
What is total reaction?
Airflow pushing back on wing and lift pushing wing up
