Airplane Design
Conceptual Design
Preliminary Design
Detail Design
Conceptual Design
Ø Requirements
Ø Weight of the airplane – first estimate
Ø 
Critical
Performance analysis
·
Maximum Lift Coefficient CL
·
Lift – to – Drag Ratio L/D
·
Wing loading W/S
·
Thrust – to – Weight Ratio
T/W
No
Ø Configuration layout – shape and size of the airplane on a drawing
(or) computer screen
Ø Better weight estimate
Ø 
Performance
analysis – does the design meet (or) exceeds requirements
Yes
Ø Optimization - is
it the best design
Ø Latitude
Ø The overall shape
Ø Size
Ø Weight
Ø Performance
Ø The shape and
size of the wing
ü Swept Back
ü Swept Forward
ü Straight
Ø The location of
the relative to the fuselage
Ø The shape and
size of the horizontal and vertical stabilizer
Ø The use of canard
or not
Ø Engine size and
placement
Ø Aerodynamics
Ø Propulsion
Ø Flight
performance
Ø Landing gear is
to retract into the wing rather than the fuselage or engine nacelle
Requirements
Ø Range
Ø Take of distance
Ø Stalling velocity
Ø Passenger
capacity
Ø Maximum velocity
Ø Rate of climb
Ø Rate of dive
Ø Landing distance
Ø Maximum load
factor
Ø Maximum turn rate
and sometime minimum turn radius
Ø Service ceiling
Ø Cost
Ø Reliability and
maintainability
Ø Maximum size
(hangers)
Ø Interior and
exterior mechanical aspects of the airplane
Weight of the airplane
Ø The gross takeoff
weight
Ø Weight estimate
Ø Albeit crude
Ø More weight –
more drag
Ø Engine with more
power – more weight
Critical performance parameter
Ø Maximum Lift
co-efficient CL
Ø Lift – to – Drag
ratio usually at cruise L/D
Ø Wing loading W/S
Ø Thrust - to -
Weight ratio T/W
Ø Achieve the
performance to estimate W/S, T/w
Configuration layout
Ø Drawing the shape
and size of the airplane
Ø Critical
performance parameter with initial weight estimate given the information to
approximately size of the airplane and to draw configuration
Better weight estimate
Ø Overall size and
shape of the airplane
Ø Improved estimate
weight
Ø More detail
estimate of the fuel weight
Performance Analysis
Ø High speed is
critical
Ø The high wing
loading that allow this high speed
Ø Increase the
takeoff and landing distance
Optimization
Ø Parameters T/W,
W/S
Constraint Diagram
Ø Solution space
for the airplane design
Ø Thrust – to -
Wing ratio
Ø Wing loading
Ø Plot of the sea –
level thrust – to – takeoff wing ratio T0/W0 versus the
wing loading at takeoff W0/S
Ø Take off
constraint
Ø Landing
constraint
Ø Sustained level
turn
Interim Summary
Ø Make a selection
of the airfoil section
Ø Determine the
wing geometry
ü Aspect ratio
ü Sweep angle
ü Taper ratio
ü Twist
ü Incidence angel
relative to fuselage
ü Dihedral,
vertical location on the fuselage
ü Wing tip shape
Ø Choose the
geometry and arrangement of the tail
Ø The size, number
and placement of the engine
Ø High Lift device
Preliminary Design
Ø Major, minor changes
Ø Structural and
control system analysis and design takes place
Ø Substantial wind
tunnel testing
Ø Computational
fluid dynamics (CFD) calculation of the complete flow field over the airplane
configuration
Ø The drawing
process
Ø Outside skiing of
the airplane
Detail Design
Ø The nuts and
bolts of airplane design
Ø Aerodynamic,
propulsion, structure, performance, and flight control analysis
Ø Rip, spar, and
section of skin now takes place
Ø The size, number
location of fasteners [rivets, welded joints]
Ø Tools and jigs
Ø Flight simulator
