KDRs Flashcards
Explain the forces of lift, weight, thrust and drag during steady level flight
Lift = weight Thrust = Drag
What is the affect of lift and drag with an increase in weight?
More weight requires more lift with a higher angle of attack which means more drag and more thrust required to maintain altitude
How are the lift-weight and thrust-drag couples balanced?
Lift-weight has nose down pitching moment, thurst-drag has a smaller nose up pitching moment. The difference is balanced by horizontal stabiliser which is shaped like an upside down wing.
Where does lift act on the wing?
Center of pressure around a third of the way back during level flight and moves forward with increase in AoA.
Which direction does lift act?
Perpendicular to relative airflow
How do the forces act during a steady climb?
Lift is less than weight. Thrust is more than drag. Thrust equals drag + rear component of weight.
How do the forces act during a steady descent?
During glide descent, lift is less than weight. Weight = lift + drag
How do the forces act during a steady balanced turn?
Lift is greater than weight to maintain level flight. Horizontal component of lift is the centripedal forace that turns the aircraft.
What does an anhedral wing do?
Decreases lateral stability. Used by heavier aircraft that struggle to roll.
What does a dihedral wing do?
Increases lateral stability particularly in low wing aircraft. When in side slip, lower wing has higher AoA and exposed to more relative airflow creating lift and righting roll.
What does a change in aspect ratio do?
Longer thinner wings create less induced drag. Smaller vortices created.
What does a swept wing do?
Increases lateral stability. When in roll, lower wing exposed to more relative airflow creating lift and righting roll.
What do washout wings do?
Reduces induced drag. Lower AoA at wing tip reduces pressure difference and the resulting wing tip vortices.
What do wing spoilers do?
Rise on top of aerofoil increasing drag and decreasing lift. Used to slow down aircraft usually on landing and can be used on one side to assist roll.
What do vortex generators do?
Creates turbulence over wing, mixing with free stream velocity and delaying separation point reducing parasitic drag. More useful at higher AoA (short field) reducing stall speed.
What do flaps do?
Increases lift and drag allowing more steep AoC/AoD on take-off and landing. Also increases visibility during slow flight as it allows a lower nose attitude.
What do trim tabs do?
Relieves control load reducing pilot workload.
Apply bernoulli’s theorem to describe how an aerofoil produces lift.
As air speeds up over the top of the wing, like a venturi, an increased dynamic means decreased static pressure to maintain total constant pressure. Difference in static pressure above and below wing gives the lifting force below the wing.
Describe Ground Effect and its effect on aircraft performance.
- Ground effect most pronounced half a wingspan above the ground but acts up to a full wingspan above the ground.
- When close to the ground, downwash restricted by ground reducing formation of wingtip vortices induced drag.
- Lift also increased.
State the effect of climb rate and angle through changes in flap
Increase in flap decreases AOC and ROC
What is the relationship between Lat and Long and positions on the Earth?
- Prime Meridian 0° E/W
- Long position is the amount of degrees E/W of line until you hit the international date line
- Equator 0°
- Poles 90° N/S
- Each degree made up of 60’ which is made up of 60”
What is the effect of lat and long on time differences?
- Earth moves 15° every hour, 1° every 4 minutes
- 15’ = 1 minute
- BOD: Further North, earlier BOD in winter, later in summer.
- EOD: Further North later EOD in winter, earlier in Summer
What is the effect of Lat and Long on distance and direction?
- 1’ = 1nm for Latitude ONLY
- As long curved, not a reliable way to measure distances
What is the purpose of a wastegate?
To control the amount of exhaust gasses flowing to the turbine by opening and closing.