Aerodynamics Of Flight

Question 1

Wake turbulence

Answer 1

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

Question 2

What is induced drag?

Answer 2

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

Question 3

If thrust is increased and angle of attack is constant what will happen?

Answer 3

The speed and lift will increase and the aircraft will climb until lift equals weight

Question 4

Air will flow using the path of _______

Answer 4

least resistance, hence moving to the tips.

Question 5

The wingtip vortex consists of _______

Answer 5

circulating air off the wingtip in a counterclockwise direction from the right tip and clockwise from the left tip

Question 6

Wingtip vortices are usually invisible, but during a humid day, _______

Answer 6

water condenses and becomes visible, so the white vortices can be seen.

Question 7

Don’t confuse wingtip vortices with _______

Answer 7

condensation trails (contrails), which are water vapors from the engine exhaust that you see streaked across the sky

Question 8

Wingtip vortices are directly proportional to _______

Answer 8

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.

Question 9

Vortices can be very dangerous to _______

Answer 9

smaller aircraft, so the pilot must be aware of any heavy aircraft in the area and avoid its vortices, which cause wake turbulence.

Question 10

Heavy aircraft need more lift. The more lift required the _______ the vortices. Heavy aircraft typically fly at _______ speeds, which means _______

Answer 10

stronger

low

increased AOA and stronger vortices. This is why heavy, slow aircraft create some of the most violent vortices

Question 11

The vortices themselves create _______

Answer 11

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.

Question 12

Vortices are smaller as the aircraft gets closer to the _______

Answer 12

ground. This is because vortices dissipate in strength as they hit the ground.

Question 13

What is turbulence flow?

Answer 13

as the angle of attack increases, the boundary layer starts to separate and the air flows in all kinds of directions

Question 14

What is laminar flow?

Answer 14

At low angles of attack, the boundary layer stays attached and air flows smoothly over the wing

Question 15

What is turbulence?

Answer 15

a sudden change in airflow by eddies (whirling motion of air) and currents.

Question 16

Light aircraft must especially avoid the _______ of large aircraft or else they _______

Answer 16

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.

Question 17

What is ground effect?

Answer 17

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.

Question 18

Ground effect doesn’t take place unless the airplane is _______

Answer 18

within half-wingspan of the ground.

Question 19

If there is not enough thrust for take off, ground effect might create _______

Answer 19

the illusion that there is, but once out of it the airplane can lose lift and crash

Question 20

During takeoff, you begin flight with what effect?

Answer 20

Ground effect

Question 21

When pilots know about ground effect, they can use it to _______

Answer 21

their advantage in certain situations

Question 22

Ground effect has advantages, such as when _______

Answer 22

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.

Question 23

Upwash is?

Answer 23

Oncoming airstream deflected upwards and over the wing by the leading edge.

Question 24

Downwash is?

Answer 24

Downward airstream deflection as it passes over the wing and past the trailing edge

Question 25

A stall is caused by _______

Answer 25

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

Question 26

Rudder effectiveness usually increases with _______

Answer 26

speed, so large deflections at low speeds, and small at high speeds are usually what’s required

Question 27

In propeller-driven aircraft, any slipstream (_______) _______

Answer 27

rearward-flowing air pushed back by the propeller

flowing over the rudder Increases its effectiveness