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