Aerodynamics Of Flight Flashcards
Wake turbulence
Atmosphere disturbance that forms behind an aircraft due to its vortices. They can impose rolling moments exceeding roll-control authority, and possibly causing occupant or aircraft damage
What is induced drag?
Lift generation causes higher pressure below the wing, lower pressure above. This pressure difference causes wingtip vortices and a downwash behind the wing. The downwash tilts the lift vector rearwards, creating a rearward component. This rearward component of lift acts in the direction of drag, and is induced drag
If thrust is increased and angle of attack is constant what will happen?
The speed and lift will increase and the aircraft will climb until lift equals weight
Air will flow using the path of _______
least resistance, hence moving to the tips.
The wingtip vortex consists of _______
circulating air off the wingtip in a counterclockwise direction from the right tip and clockwise from the left tip
Wingtip vortices are usually invisible, but during a humid day, _______
water condenses and becomes visible, so the white vortices can be seen.
Don’t confuse wingtip vortices with _______
condensation trails (contrails), which are water vapors from the engine exhaust that you see streaked across the sky
Wingtip vortices are directly proportional to _______
weight and AOA. As weight increases, more airflow is needed and so the stronger the vortices. As AOA increases, airflow over the top is relatively faster and so stronger vortices.
Vortices can be very dangerous to _______
smaller aircraft, so the pilot must be aware of any heavy aircraft in the area and avoid its vortices, which cause wake turbulence.
Heavy aircraft need more lift. The more lift required the _______ the vortices. Heavy aircraft typically fly at _______ speeds, which means _______
stronger
low
increased AOA and stronger vortices. This is why heavy, slow aircraft create some of the most violent vortices
The vortices themselves create _______
induced drag. The greater the AOA, the greater the pressure difference (which means more lift), and so more violent vortices which in turn creates more induced drag and turbulence.
Vortices are smaller as the aircraft gets closer to the _______
ground. This is because vortices dissipate in strength as they hit the ground.
What is turbulence flow?
as the angle of attack increases, the boundary layer starts to separate and the air flows in all kinds of directions
What is laminar flow?
At low angles of attack, the boundary layer stays attached and air flows smoothly over the wing
What is turbulence?
a sudden change in airflow by eddies (whirling motion of air) and currents.
Light aircraft must especially avoid the _______ of large aircraft or else they _______
wake turbulence
roll, and especially during takeoff and landing when close to the ground. Pilots must keep their distance, make adjustments while flying and taking off, and pay attention to heavy aircraft to avoid its wake turbulence.
What is ground effect?
The aerodynamic phenomenon that happens right before touchdown when the aircraft feels like it cannot go any lower. This happens because of the trapped air between the ground and the wings, which act like a cushion. The airflow is restricted by the surface below, like water or land.
Ground effect doesn’t take place unless the airplane is _______
within half-wingspan of the ground.
If there is not enough thrust for take off, ground effect might create _______
the illusion that there is, but once out of it the airplane can lose lift and crash
During takeoff, you begin flight with what effect?
Ground effect
When pilots know about ground effect, they can use it to _______
their advantage in certain situations
Ground effect has advantages, such as when _______
taking off a short or soft runaway. In short runaways the pilot can get enough speed and tilt the nose up high to get the airplane out of of the ground as quickly as possible, and when up in the air the pilot can lower pitch to stay in ground effect and build enough speed to get out of it. The same procedure can be done with soft runaways, because they create drag on the wheels, so getting out of the surface quickly provides an advantage.
Upwash is?
Oncoming airstream deflected upwards and over the wing by the leading edge.
Downwash is?
Downward airstream deflection as it passes over the wing and past the trailing edge
A stall is caused by _______
the separation of airflow from the wing’s upper surface. Separation usually starts at the trailing edge and moves forwards, and a reverse airflow starts creeping in, pushing the wing downwards
Rudder effectiveness usually increases with _______
speed, so large deflections at low speeds, and small at high speeds are usually what’s required
In propeller-driven aircraft, any slipstream (_______) _______
rearward-flowing air pushed back by the propeller
flowing over the rudder Increases its effectiveness
