Wing Design Flashcards
High Aspect Ratio on lift/drag
High Cl
Less wing tip vortices less induced drag from lower span wise pressure gradient
Wing Loading
How much lift needed to produce weight
Measured in kg/m2
Small span heavy ac - High wing loaded
Large span light ac - Low wing loaded
Span Wise Distribution
Change in lift across the span
Methods for reducing Cl peak at tip
Camber changes (less towards tip)
Washout - reduce AOI to reduce local AOA at tip
Surface area reduction at tip
Ellipetical Wing
Constant CL
Lift drops towards span
Expensive not used on CAT
Rectangular Wing
Greatest lift at root
Cl reduces towards tip
IAOA increases/EAOA reduces/Induced drag increases
More downwash towards tip
Tapered Wing
CL peak at mid span
Ideal taper ratio of 0.5
Sweep back wing
Greatest downwash at root
EAOA greatest towards tip
Wing tip vortex thanks to downwash
Modern A/C design
Swept + Tapered
Not great stall characters tip stalling
Economical
Closest to elipetical design
Sweep Angle
Angle at which wing is inclined to the lateral axis
Usually measure at 25% of the chord
Taper Ratio Formula
Tip Chord/Root
Aspect Ratio Formula
Wingspan2/wing area
Span2/ area
Span/chord
Thickness/Chord Ratio
The ratio of max thickness of an aerofoil on the chord length expressed as a percentage
Usually between 10% to 12%
Mean Aerodynamic Chord is
The chord of an equivalent untwisted rectangular wing with the same pitching moment and lift characteristics as the actual wing
Spanwise flow is higher in
Slow speed/high aspect ratio ac
(Slow flight less KE so more inclined to flow Spanwise)
(Faster planes/shorter cord less)
Effective AOA is the angle between
The angle between the effective airflow and the chord line
Induced AOA is the angle between
Between the relative airflow and the effect air flow
Smaller wing tip vortices means
Greater effective AOA and smaller Induced AOA as Effective airflow is less inclined
Strong vortices does what to downwash and EAF
Increases the downwash inclining the EAF upwards
Smaller vortices means
Shallow effective airflow angle
Bigger effective AOA
Smaller induced AOA
Less induced drag
Wing tip vs wing root on a rectangular ac
Wing tip = strong vortices/greater effective airflow/smaller eAOA/larger induced AOA
Wing root = weaker vortices/greater effective AOA
Directional flow of trailing tip vortex
Span wise flow is always outward from under wing to upper surface
Anti clockwise around right wing
Clockwise around left wing
When viewed from behind
What wing produces the lowest induced drag
Ellipetical wings produce the most lift for the smallest wing tip vortices
At there tips the pressure differential is almost 0
Wing Loading
Measured in kg/m2
Weight per unit of the wing area
Greatest on heavy ac with smaller wings = higher wing loading
More intense vortices
Which wing planform has the lowest induced drag
Ellipetical wing
Which wing has the highest induced drag
Rectangular (longer tip chord)
Swept back wing advantages and disadvantages
+ Increases the critical Mach number
+ Positive contribution to static directional stability
+ Positive significant contribution to static lateral stability
- tip stall and pitch up at stall
- lower cl for given AOA which increases stall speed
- clmax less and occurs at higher AOA
- change in CL per change in alpha is less
- must have complex high lift devices to to/ld
- must be flown at high AOA than straight wings for cl
Wing AOA
Chord to the relative airflow
Aeroplane AOA
Longitudinal axis to relative air flow (speed vector)
Angle of incidence
Wing root chord to longitudinal axis
