Aircraft Configuration selection process

1. Aircraft Configuration
Selection Process
Second stage
Source:Roskam
Made by: Amr Emad
CUFE RESEARCH TEAM

2. Preliminary configuration design and
integration of the propulsion systems
 1-selection of overall configuration:
conventional
flying wing
tandem wing
canard
three surface
joined wing

3. Preliminary configuration design and
integration of the propulsion systems
 2-selection of fuselage layout
3-selection of propulsion system layout:
piston/propeller with or without supercharging
turbo/propeller of prop-fan
turbojet or rocket
ramjet of rocket
rotary/diesel
electric(solar-microwave-lithium fuel cell)

4. Preliminary configuration design and
integration of the propulsion systems
 4-selection of number of engines and/or propellers
5-integration of the propulsion system:
propellers: pusher or tractor
engine buried in the fuselage or in the wing
engines in nacelles on the fuselage or on the wing
disposition of engines and nacelles

5. Preliminary configuration design and
integration of the propulsion systems
 6-selection of planform design parameters for the
wing and for the empennage (tails and/or canard):
size
aspect ratio
sweep angle
thickness ratio
taper ratio
control surface size and disposition
incidence angle
dihedral angle

6. Preliminary configuration design and
integration of the propulsion systems
 7-selection of type, size and disposition of high lift
devices:
mechanical or powered flabs
trailing edge and/or leading edge devices

7. Preliminary configuration design and
integration of the propulsion systems
 8-selection of landing gear type and disposition:
fixed of retractable
tail dragger ,tricycle of tandem
number of struts and tires
wheel location up and down
feasibility of gear retraction

8. Preliminary configuration design and
integration of the propulsion systems
 9-selection of major systems to be employed by the
airplane:
flight control system, primary and secondary
navigation and guidance system

9. Preliminary configuration design and
integration of the propulsion systems
 10-selection structural arrangement,type of structure
and manufacturing breakdown:
metallic,composite or mixture
arrangement of primary structure of major airplane
components
attachment structure for landing gear
manufacturing and assembly sequence

10. Preliminary configuration design and
integration of the propulsion systems
 important notes:
configuration design is non-unique and iterative
process

11. Preliminary configuration design and
integration of the propulsion systems
 two phases of preliminary design:
the first consists of 16 step
-the feasibility of a given configuration with a
minimum engineering work
limited accuracy but require only small amount of
engineering man-hours
the second consists of 30 step
-these method have fairly good accuracy but require
significant expenditure of engineering man-hours

12. Preliminary configuration design and
integration of the propulsion systems
 Step by step guide to configuration design:
the results of preliminary sizing:
take-off weight
operating weight empty
payload weight
mission fuel weight
wing area
wing aspect ration
take-off power
required lift coefficients:
clean clmax
take-off clmax-to
landing clmax-l
These data are the input data for the airplane

13. Preliminary configuration design and
integration of the propulsion systems
 preliminary design sequence I :

14. Step one
 step 1: carefully review the mission specification and
prepare a list of those items which have the major
impact on the design.
for example:
very short and soft field requirements
hot and high field requirements
water based or amphibious requirements
for carrying large vehicles
requirement for extreme range or endurance
requirements for large search radars

15. Step two
 step 2:perform a comparative study of airplanes with
similar mission performance
the objective is :familiarize yourself with the
competition and with work done by others

16. Step three
 step 3:select the type of configuration to be designed
note that: for a student who is just getting started in
study of airplane design it's important to:
make a decision to go with a certain type of
configuration and move on

17. Step four
 step 4:prepare a preliminary(scaled)drawing of the
fuselage

18. Step five
 step 5:decide which type of propulsion system is to
be used and how propulsion system will arranged.
this step will affect on fuselage ,wing and other
components of aircraft

19. Step six
 step 6:decide which wing planform design parameters are
to be used.
also decide on the size and location of wing mounted
lateral controls.
surface planform(s) and aspect ratio(A) are already known,
these were determined during the preliminary sizing work
the additional parameters must now be selected:
wing taper ratio
wing sweep angle
wing thickness ratio
wing airfoil(s)
wing incidence angle
wing dihedral angle

20. Step seven
 step 7:decide on the type, the size and disposition of
high lift devices.

21. Step eight
 step 8:decide on the layout of empennage:size
planform geometry and disposition.
also select the size and location of longitudinal and
directional controls.
note that:the word "Empennage" is used here to
indicate tails,canards and other additional stabilizing
or control surfaces to be used in the configuration

22. Step nine
 step 9:decide which type of landing gear is to be used
and its disposition

23. Step ten
 step 10:decide a scaled preliminary arrangement
drawing of proposed configuration and perform a
class I weight and balance analysis.

24. Step eleven
 step 11:perform a class I stability and control analysis
of proposed configuration.

25. Step twelve
 step 12:perform a class I drag polar analysis

26. Step thirteen
 step 13:analyze the results of steps 10 and 11 by asking
these questions:
1-If the weight and balance results of step 10 as well as
the stability and control results of step 11 are satisfactory
-proceed to step 14
2-if the results of step 10 show that the airplane has a "tip-over"
problem. This means that the c.g is incorrectly
located relative to landing gear.

27.  -try making minor adjustment to wing and landing
gear locations and see if the problem can be solved
that way.
-if you can, make the changes(s) and go on to step 14.
-if the problem cannot be solved with minor
adjustments, consider a change in the configuration.
That may imply going back to step 2.
3-if the airplane has too much travel between forward
and aft c.g
-the suggestion made under 2. apply here also.

28. Notes
 Note that: this problem tends to disappear if the
payload c.g ,the fuel c.g. and the OWE c.g. are close
together.(Try to achieve this)
sometimes the problem can be solved by relocation
of a particularly"heavy"component.

29. Step fourteen
 step 14:from the drag polar of step 12,compute those
L/D values which correspond to the mission phases
and to the sizing requirements considered in the
preliminary sizing process of one.
-tabulate the new and old L/D values
-Determine the impact of any changes in L/D on
Wto,We and Wf. this can be done using the results of
the sensitivity analyses carried out during the
preliminary sizing process

30. Step fifteen
 step 15:prepare a dimensioned three view which
reflects all changed which were were made as a result
of the iterations involved in steps 10 through 14.

31. Step sixteen
 step 16: prepare a report which documents the results
obtained during p.d sequence I include
recommendations for change, for further study or for
research and development work which work which
needs to be carried out.
Preliminary design sequence II:
this p.d sequence strats with the threeview of step 15
and with the report of step 16

32. Step seventeen
 step 17:list the major systems needed in the airplane.
1-airplane systems have a significant impact on empty
weight.
2-to determine any obvious conflicts which would
arise by having two or more systems occupy the same
space in the airplane.

33. Step eighteen
 step 18:size the landing gear tires and struts using
class II methods.

34. Step nineteen
 step 19:prepare an initial structural arrangement
drawing

35. Step twenty
 step 20:redraw the threeview obtained at the end of
p.d sequence I

36. Step twenty-one
 step 21:perform a class II stability and control analysis
using the threeview of step 20

37. Step twenty-two
 step 22:compute the installed power and/or thrust
characteristics of the propulsion system.

38. Step twenty-three
 step 23:list all performance requirements which the
airplane must meet.

39. Step twenty-four
 step 24:iterate through 17 to 23 as needed and adjust
the configuration.

40. Step twenty-five
 step 25:finalize the threeview and tabulate the
essential airplane geometry

41. Step twenty-six
 step 26:finalize the structural arrangement.

42. Step twenty-seven
 step 27:prepare a preliminary manufacturing
breakdown.
outline of configuration possibilities:
3.3.1 overall configuration
conventional
flying wing
canard or tandem wing
three surfaces
joined wing

43.  3.3.2 fuselage configuration
conventional
twin fuselage
twin boom with center fuselage
burnelli(give examples)

44.  3.3.3 engine type number of engines and engine
disposition
3.3.3.3 engine disposition:
tractor
pusher
combination tractor and pusher
within these three basic arrangements, engine can be
installed in the following manner:
1-in pods or nacelles
2-buried
whether podded or buried, engines can be disposition on
or in:
1-the wing: below above or in-line
2-the fuselage
3-the empennage

45. Step twenty-eight
 3.3.4 wing configuration
3.3.5 empennage configuration
3.3.6 landing gear type and disposition

46. 5.1 selection of propulsion system
type:
 step 5.1: check the mission specification for and definition
of the type of power plant required
step 5.2: draw preliminary speed(or Mach) versus altitude
envelope for the airplane
step 5.3:compare the airplane speed-altitude envelope
with those and decide which type of power plant provides
the best overall match
step 5.4:determine the maximum power requirement for
airplane
step 5.5:decide on the number of engines and on the
specific engine model to be used.
step 5.6:if the airplane being designed is a propeller driven
airplane, determine the required propeller blades with the
following class I method.

47. Integration of the propulsion system:
 Having decided on the type and the number of
engines to be employed, the next decision is: where
should these engines be located?!

48.  step 5.7:decide on pusher ,a tractor or mixed
installation
step 5.8:decide on mounting the engines on:
1-wing
2-the fuselage
3-the empennage
4-any combination of 1 through 3

49.  step 5.9: obtain the necessary information on:
1.engine geometry and clearance envelope
2.engine attachment points
4.engine c.g. location
step 5.10:make dimensioned drawings of all engine
installation required by your airplane
step 5.11:draw the engine installation in the
threeview. The amount of detail here depends on the
type of the threeview being drawn

50.  step 5.12:document
wing configuration
empennage and landing gear configuration and its
disposition.

51. Questions ?!?!