Drag

Question 1

what direction does drag act

Answer 1

in the direction of the relative airflow

Question 2

main difference between Laminar and Turbulent?

Answer 2

this would be the greater speed change in turbulent

Question 3

describe laminar flow?

Answer 3

• all flow parallel
• lower average speed
• less kinetic energy

Question 4

describe turbulent flow?

Answer 4

• thicker
• higher speed
• more kinetic energy
• more drag

Question 5

what is interference drag?

Answer 5

this Is drag that occurs when two wing surfaces are joined together ie fuselage and the wings

Question 6

how do we reduce interference drag?

Answer 6

we reduce it by what’s.known as filleting. it smoothes out velocity.

Question 7

what is induced drag?

Answer 7

this is drag created when an aerofoil creates lift

Question 8

what does increase is downwash do to aoa?

Answer 8

the AoA is effectively reduced. ands is lift.

Question 9

how do you reduce induced drag?

Answer 9

• this is done with tapered elliptical wings
• washout
• reducing thickness at tip
• elliptical distribution

Question 10

what do elliptical wings ensure?

Answer 10

elliptical wings ensure that lift is even distributed across the wings and that the whole wing will stall at the same time.

Question 11

what does flap deployment do to wing tip vortices?

Answer 11

it reduced wing tip vortices due to the disruption of span wise flow.

Question 12

how can you reduce wing tip vortices?

Answer 12

• increase the washout

- increase the size of the flaps

Question 13

how can wing tip vortices be increased?

Answer 13

• heavier aricraft

- clean configuration

Question 14

how are wingtip votices created?

Answer 14

air moves from the underside of the wing to the upper side of the wing which is lower pressure. then falls of the back of the wing and spirals down and outwards

Question 15

how long can wing tip vortices last?

Answer 15

up to 3 mins

Question 16

what does the maximum gradient on a polar curve represent?

Answer 16

this would be the point of maximum lift to drag ratio.

Question 17

what is the coefficient of drag equation?

Answer 17

cdi = CL2/AR

Question 18

what does increase in aspect ratio do to induced drag?

Answer 18

it decreases the induced drag.

Question 19

where does speed stability occur?

Answer 19

this occurs above the speed where level flight can be maintained with minimum thrust. VMD

Question 20

what height does ground effect take effect?

Answer 20

increases as height reduces, but below half the wingspan

Question 21

what does ground affect do to downwash?

Answer 21

ground affect decreases downwash, increases effective AoA

Question 22

why does ground affect occur?

Answer 22

airflow is slowed even more below the wing due to surface friction.