Principles of flight Flashcards
Aircraft can only remain airborne whilst…
Moving
How is lift generated?
By the aircraft’s wing
How is the top surface of the wing shaped?
Such that air which flows over the wing increases speed and reduces pressure
How is the bottom surface of the wing shaped?
Such that air which flows under the wing reduces speed and increases pressure
At what angle does lift act to the direction of air flow on the wing?
90 degrees
What is the point at which lift acts called?
The centre of pressure
Factors affecting lift:
- An increase in airspeed results in an increase in lift
- An increase in angle of attack results in an increase in lift
Airspeed is direction proportional to…
Lift squared
What is the critical angle for stalling?
15 degrees
Decreased air density leads to…
Decreased lift (this can be due to an increase in altitude, temperature or humidity)
What happens if lift is greater than weight?
The aircraft ascends
What happens if lift is less than weight?
The aircraft descends
What happens if lift is equal to weight?
The aircraft remains at level flight
What happens if thrust is greater than drag?
The aircraft accelerates
What happens if thrust is less than drag?
The aircraft decelerates
What happens if thrust is equal to drag?
The aircraft’s speed remains constant
Aircraft speed is directly proportional to…
Drag squared
What are the 3 axis through the centre of gravity?
- Lateral axis through wings
- Longitudinal axis along the aircraft
- Normal axis, up and down
What is pitching?
Nose of the plane up and down (elevators)
What is rolling?
Whole plane to one side (ailerons)
What is yawing?
Nose of the plane side to side (fin/rudder)
What is stability?
The ability of an aircraft to return to level flight of its own accord without the pilot having to intervene, a result of good design
Turbulence
Bumpy air can cause a wing to drop or nose to rise or fall
What are dihedral wings?
Those with their lowest points at attachment to the body
What are anhedral wings?
Those with their highest points at attachment to the body
What are trimming tabs?
Extensions on the elevator, aileron and rudder to help to cancel out unwanted forces on the pilots joystick
Airbrakes
- Reduces lift and increases drag
- Used when approaching landing
Gliding angle
How far a glider can glide from a given height e.g. Viking is roughly 15km for 1km (weather dependent)
What does spinning rotor blades in one direction cause?
Torque in the other direction
What does the tail rotor do?
Counteracts force, preventing the helicopter from spinning out of control
What is the rotor disk?
The area covered by the blades
How can lift be increased in a helicopter?
By increasing the angle of attack
How is lift generated?
By the Bernoulli principle
How is lift distributed around the wing?
Uneven
What accompanies an object when it moves through the air?
A “wake” of eddies and vortices which wastes energy
How can we minimise drag?
- Reduce protruding parts
- Streamlining
- Streamlining shapes to have a “finesse ratio” of between 3 and 4:1
What are elevators controlled by?
Moving the joystick back and forth
What are ailerons controlled by?
Moving the joystick left and right
What is the rudder controlled by?
Rudder pedals
What happens when the angle of attack is too great?
The airflow over the wing cannot meet the airflow under the wing
What do flaps do?
Allow you to generate lift at lower speeds
Lower stalling speed is…
Better
Factors increasing stalling speed
- More weight
- Less power
- Manoeuvres and steeper turns
- Wind
The gliding angle
How steep your descent is
What does increasing or decreasing rotor speed affect?
Lift production
What does the collective pitch lever do?
Changes the angle of the rotor blades
What do the yaw pedals do?
Control the angle of the tail rotor blades
