Aerofoil Design

Question 1

What is a chord line

Answer 1

A straight line connecting LE to TE

Question 2

What is Chord

Answer 2

The length of the chord line

Question 3

What is Mean Aerodynamic Chord (MAC)

Answer 3

The chord average from root to wingtip

Question 4

What is thickness/ Chord ratio

Answer 4

The thickest section of wing expressed as a percentage of chord length
Typically ~ 12%

Question 5

What is the mean camber line

Answer 5

Line formed by at halfway between upper and lower surface of a wing. From LE to TE

Question 6

What is aerofoil camber

Answer 6

Dist between mean chord and mean camber line

Question 7

Where is the max camber of an aerofoil

Answer 7

At the point where mean chord and mean camber lines are furthest apart

Question 8

Can the points of max camber and max thickness be co-located

Answer 8

Yes

Question 9

What is upwash WRT low pressure above a wing

Answer 9

Air approaching the LE starts to flow upwards due to low pressure above the wing

Question 10

What causes wing tip vortices

Answer 10

Spanwise flow

Question 11

WRT RAF which direction does lift act

Answer 11

Perpendicular

Question 12

What is the total reaction of an aerofoil

Answer 12

The resultant of lift and drag forces

Question 13

What 2 parameters are used to measure AoA

Answer 13

Chord line and RAF

Question 14

What is the critical angle of an aerofoil

Answer 14

AoA which if exceedes airflow will seperate from top of wing, causing large sudden decrease in lift

Question 15

The angle of attack of an aerofoil is the angle measured between the _____ & the RAF

Answer 15

Chordline

Question 16

What would be required for an aerofoil to generate no lift

Answer 16

Negative AOA or be at an angle below horizontal

Question 17

What is leading edge stagnation point

Answer 17

Air molecules impacting the leading edge, causing them to bunch up resulting in an envelope of high pressure air

Question 18

Does the LE stagnation point only consist of dynamic pressure

Answer 18

No

Question 19

What is total head pressure and how does it differ from RAF

Answer 19

Is combination of static and dynamic pressure from LE stagnation point

Question 20

Is total head pressure greater or lower that RAF static pressure

Answer 20

Greater

Question 21

Does a higher AoA increase or decrease LE stagnation pressure

Answer 21

Increase

Question 22

What is total head pressure

Answer 22

Total head pressure is the pressure of the completely stopped air within the LE stagnation point

Question 23

Does total head pressure aid or hinder aircraft movement

Answer 23

Hinder

Question 24

Does the low pressure area above the wing act through a single point

Answer 24

No, load is spread over chord of the wing

Question 25

What is it called when the low pressure is represented by by a single point on the chord line

Answer 25

CP

Question 26

What happens to CP when AoA is increased

Answer 26

CP moves forward

Question 27

What happens to the Low Pressure on the upper wing at the Critical Angle

Answer 27

CP moves towards LE and collapses, resulting in large sudden loss of lift

Question 28

Will a high lift wing have a high or low thickness/ chord ratio

Answer 28

High

Question 29

Will a short take off landing aircraft have a high degree of camber and thickness or low degree of camber and thickness

Answer 29

High and high

Question 30

When and why would a symmetrica aerofoil be used?

Answer 30

Why: to supply equal amounts of lift in both positive and negative directions When: vertical stabliser

Question 31

When will symmetrical aerofoils produce lift?

Answer 31

As soon as AoA is created relative to RAF

Question 32

What are typical characteristics of a high speed aerofoil

Answer 32

Low drag section, little camber

Question 33

What are the advantages of high speed aerofoil

Answer 33

High subsonic speeds for long range | Fuel efficient

Question 34

WRT shockwaves, how does a gentle camber high speed aerofoil affect change the formation of shockwaves

Answer 34

The gentle upper surface delays build up of shockwaves at high subsonic speeds, reducing shock drag rise/ shock stall