Aircraft Wings
Introduction to Aerospace Engineering
EG-194
College of Engineering
Swansea University
The facts
Naming convention for planform of a wing
Characteristics of a wing
Dihedral angle, swept wings
Trapezoidal Wing Planform (1)
• A planform is the shape
and layout of a fuselage
and wing
wing apex
wing root
wing tip
fillet
(Note this is not a fillet in
the mechanical sense)
•
Boeing
Trapezoidal Wing Planform (2)
+
= gross wing area
S or SG
= net wing area SN
• It is the gross wing area
that affects aerodynamic
performance.
span b
•
Boeing 720
• The span is the distance
from one wing tip to the
other
Trapezoidal Wing Planform (3)
• most wing parameters are
defined in terms of gross wing
root* chord cr
or c0
•
The chord is length of the wing in
the nose to tail direction
(*despite name, usually
defined on the centreline!)
fuselage
centre-line
semi-span s
tip chord ct
Trapezoidal Wing Planform (4)
sweep angle Λ0.25
fuselage
centre-line
¼ chord line
25 % chord line
• The angle of sweep is
conventionally measured along the
quarter chord line.
• If the quarter chord line varies in
sweep angle, the leading edge is
used;
• If that varies, the sweep is
expressed in sections (e.g., 25
degrees from 0 to 50% span, 15
degrees from 50% to wingtip).
Swept wings
• The aerodynamic properties of a local section of a wing are
governed mainly by the component of flow normal to the leading
edge.
Speed V
θ
Normal Speed
V cos θ
• Sweeping a wing can be used to delay the onset of forms of
drag associated with transonic flight.
– Increasing the Mach number at which these effects occur.
– Allowing a plane to fly quicker for a given thrust
Trapezoidal Wing Planform (5)
+
ct
λ=
cr
• wing taper ratio
=S
cr
• standard mean chord, SMC,
(or geometric mean chord)
S
c=
b
• mean aerodynamic chord,
+b / 2
MAC
1
2
span b
ct
c =
S
 c dy
−b / 2
• aerodynamic shape of wing,
defined by its Aspect Ratio
b
b2
=
AR =
c
S
Mean Chords
• The SMC and MAC are both measures of the chord of an
equivalent rectangular wing sharing attributes with the real wing
• For the SMC these attributes are
– the same area and span
– It is a geometric value and is rarely used in aerodynamics.
• For the MAC the attributes are
– the same area, aerodynamic force and position of the
centre of pressure at a given angle of attack
Trapezoidal Wing Planform (6)

high wing
anhedral (negative)

mid wing

low wing
dihedral (positive)
Γ
Dihedral / Anhedral Angle
• Dihedral angle is the upward angle, relative to the horizontal, of
a wing
• A negative dihedral angle is termed an anhedral angle.
• The dihedral effect is a rolling moment resulting from slideslip
– Slideslip is motion sideways
• For a dihedral angle the rolling moment works to restore the
plane to level flight
– Aids stability
– Lowering the centre of gravity and wing sweep do the same
• Anhedral angle aids manoeuvrability
Aspect ratio
• You will learn later in this module that induced drag is inversely
proportional to aspect ratio.
• Hence high aspect ratio equals lower thrust requirements
• Problems with high AR
– Bending moments -> more deflection or stronger structure
– Manoeuvrability
– Where do you put the fuel in long thin wings?
– Other forms of drag dominate at or around supersonic
speeds
Important Information
Examples of wing types
Very high AR – Round-the-World Flight
•
Voyager
High AR + Sweep – Airliner
•
CV-990
Medium AR – Subsonic

Spitfire

Sea
Fury
Low AR + Sweep + Taper
Supersonic + Stealth
•
F-22
Very Low AR – Mach 2+
•
F-104 Starfighter
Very Very Low AR – SST demonstrator
•
HP-115
Many other planforms: non-trapezoidal wings
• crescent (Victor)
– Victor takes the concept of
swept wings one step
further by adjusting the
sweep angle in three steps
along the wing.
– This allows each section to
independently raise the
critical Mach number and so
achieve a high cruise speed
• Handley Page Victor
Many other planforms: non-trapezoidal wings
• Lambda (B-2 Stealth bomber )
– Intended to deflect or
absorb radar signals
– Composites and radar
absorbing paint employed

Northrop Grumman B-2 Spirit
Non-Trapezoidal Wings
– ogee (Concord)
– leading-edge extensions & strakes (F/A-18)

Concorde

F-18
Non-Planar Wings
• The SNECMA Coléoptère (below left)
– was a vertical take off aircraft developed by the French in
the 1950s. Tested but very unstable in flight
• The North American Aviation XB-70 Valkyrie was the prototype
version of the proposed B-70 nuclear-armed deep-penetration
strategic bomber.

ring
wing
•

winglets
XB-70
Wingtip devices
• Winglets (used on most modern airliners)
– Increase the effective aspect ratio
– Lower lift-induced drag (reduce wingtip vortices)
– But also increase other types of drag
– Adds weight to end of wings
Beechcraft Starship
Multiple Wings
•
Biplane

Sopwith Triplane


Tandem Wing (Proteus)
Box-Wing
Box Wing
14-bis / Oiseau de proie
(Santos Dumont, 1906)
Variable Geometry
• To take off you need a wing configuration that works well when
induced drag is dominant.
• At high speeds the wing design must primarily address wave
drag.
• The solutions to these two problems are mutually exclusive.
• Hence the concept of variable geometry so the wing shape can
change to one that works well in the current regime.
Variable Geometry
•
Tornado

B-1B


oblique wing SST
F-14