Private Pilot Ground School モドキ
- 4 Aerodynamic Forces
- 4 forces in straight and level flight
- Lift is usally 5 to 8 time more than Thrust (depends on design and engine)
- Parasite Drag (increases as speed increases, as frictions)
- Induced Drag (increases as speed decreases, or pitch increases)
- Total Drag = Parasite Drag + Induced Drag
- Angle of attack (AOA)
- The angle between chord line and relative wind
- Lift and Drag is created propotional to this AOA, not attitud
- Stall and Spin
- As angle of attack increases, the lift increase until Critical Angle of Attack
- The air flow separates over the air foil beyond this angle
- STALL (loss of lift will happens)
- Airfoil stalls at critical angle of attack regardless of CG, Weight, Density, etc.
- Spin is a kind of continuous stall with when one wing stalls more than the others.
- break a stall, follow manifactures (POH) instruction.
- if none is avaialbe
- power off
- aileron neutral
- full oppiste rudder to stop the rotation
- reduce backpressure move briskkly to break the stall
- as rotation stops, neutralize, and smooth recovery from dive
- then recover as other stall, watch out for secondary stall
- each airplane spins differently
- Airplane does not sipn if it is not stalled
- Flight control
Turning and Load Factor
- 3 Major Control surface
- Three axes of airplane
(1) Longitudinal axes
Moving around longitudinal axes is ROLL which is controlled by AILERON.
(2) Lateral axes
Moving around lateral axis is PITCH which is controlled by ELEVATOR.
(3) Vertical axes
Moving around vertical axes is YAW which is controlled by RUDDER.
- Center of Gravity (CG)
- CG is the point at which three axis cross.
- aircraft or objects moves around CG
- increase lift and drag by changing airfoil
- slower airspeed for takeoff and landing.
- slower stalling speed.
- increase performance on landing and takeoff period
- increases angle of descent without increase airspeed.
- decreases weight on landing gear at the moment of touch down.
- helps to reduce landing and takeoff speed
- Higher Drag in Cruise, so it will be retracted normal cruise
- reliefs pressure to help a pilot.
- help to fly better
- little tab on the edge of flight control surface.
- moves opposite but localized lift moves flight control to desired position
- some trim control only changes tension on control cable.
Load Factor and Stall.
- To turn the airplane (or anything) it must have sideward force.
- You can create this sideward force by banking the airplane.
- The direction of lift is Inclined.
- One component of lift still acts vertically to oppose weight.
- The other component acts Horizontally to pull the airplane inside of the turn,
- 'Horizontal component of lift causes airplane to turn.
- During the turn vertical component of lift is decreased.
- To make level turn
- increase power, or
- increase angle of attack
- Load Factor
- Load supported by wing
- Load Factor = (G) = Load / Actual Weight
- Load factor chart
- Bank angle increase, Load Factor increase.
- Load Factor increase, stall speed increase.
- banked = Less Vertical Component of Lift
- Wings need to create more Lift at same airspeed => increase Angle of Attack
- Reaches Critical Angle of Attack at faster airspedd than Vs
Pitch Stability and CG range
- It is a characteristic of an airplane in flight that causes it to return to original condition after it is disturbed
- "Stable airplane requires less effort to control"
- If the CG is located forward of forward limit of CG
- The airplane is too stable
- It is hard to pitch up at takeoff and landing.
- may not have enough control on landing.
- If the CG is located rearward of afｔ limit of CG
- The airplane became unstable.
- It's hard to recover from stall, or may be impossible to recover from a spin.
- (An airplane may fly faster)
Pitch and power
- It must stay certain range to fly safely.
Left Turning Tendency
- Prop wash causes stronger tail down force.
- If you reduce Power
- Less Prop wash
- Less tail down force
- Nose comes down.
- Constant angle of attack
- usually results Constant airspeed (if no pitch contol is touched
Torque: Action (turning propeller to right) has reaction (banking airplane left).
P-factor: Asymmetrical thrust (yaw to the left)
Slip stream (Vertical Stabilizer to the right)
Gyro precession (Tailwheel) The reaction to the force applied to gyro acts 90 degrees ahead of rotation.
- High power & High angle of attack (Low airspeed )= Left turning tendency is the GREATEST
- this is not for nosewheel airplane (tri-cycle, e.g. C-172)
- Incresed Lift and Reduced Induced Drag near ground.
- Airflow is deflected down by wingtip vortex.
- near ground, vortex is blocked by ground and became weaker as plane get closer to the ground.
- less wind vortex, less induced drag created.
- a change in airflow by the ground.
- Local air flow became less bended down = less tiled lift
- Less tiled Lift = More lift and Less Induced Drag
- happens in less than half of the length of wing span above ground.
- increase as plane gets lower. More effect in a low wing airplane
- It causes the airplane to
- has more lift in ground effect and get stronger as it gets closer to the ground
- Float during landing.
- Become airborne before reaching recommended take off speed during takeoff.
- This is NOT a recommended way of explaining, but
- It is like cushioning effect of the air near ground