Aircraft configuration

Aircraft ConfigurationSelection Process

Second stageSource:Roskam

Made by: Amr EmadCUFE RESEARCH TEAM

1-selection of overall configuration:conventionalflying wingtandem wingcanardthree surfacejoined wing

Preliminary configuration design and integration of the propulsion systems

2-selection of fuselage layout3-selection of propulsion system layout:piston/propeller with or without superchargingturbo/propeller of prop-fanturbojet or rocketramjet of rocketrotary/dieselelectric(solar-microwave-lithium fuel cell)


4-selection of number of engines and/or propellers5-integration of the propulsion system:propellers: pusher or tractorengine buried in the fuselage or in the wingengines in nacelles on the fuselage or on the wingdisposition of engines and nacelles


6-selection of planform design parameters for the wing and for the empennage (tails and/or canard):sizeaspect ratiosweep anglethickness ratiotaper ratiocontrol surface size and dispositionincidence angledihedral angle


7-selection of type, size and disposition of high lift devices:mechanical or powered flabstrailing edge and/or leading edge devices


8-selection of landing gear type and disposition:fixed of retractabletail dragger ,tricycle of tandemnumber of struts and tireswheel location up and downfeasibility of gear retraction


9-selection of major systems to be employed by the airplane:flight control system, primary and secondarynavigation and guidance system


10-selection structural arrangement,type of structure and manufacturing breakdown:metallic,composite or mixturearrangement of primary structure of major airplane componentsattachment structure for landing gearmanufacturing and assembly sequence


important notes:configuration design is non-unique and iterative process


two phases of preliminary design:the first consists of 16 step-the feasibility of a given configuration with a minimum engineering worklimited accuracy but require only small amount of engineering man-hoursthe second consists of 30 step-these method have fairly good accuracy but require significant expenditure of engineering man-hours


Step by step guide to configuration design:the results of preliminary sizing:take-off weightoperating weight emptypayload weightmission fuel weightwing areawing aspect rationtake-off powerrequired lift coefficients:clean clmaxtake-off clmax-tolanding clmax-lThese data are the input data for the airplane


preliminary design sequence I :


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 requirementshot and high field requirementswater based or amphibious requirementsfor carrying large vehiclesrequirement for extreme range or endurancerequirements for large search radars

Step one

step 2:perform a comparative study of airplanes with similar mission performancethe objective is :familiarize yourself with the competition and with work done by others

Step two

step 3:select the type of configuration to be designednote 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

Step three

step 4:prepare a preliminary(scaled)drawing of the fuselage

Step four

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

Step five

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 ratiowing sweep anglewing thickness ratiowing airfoil(s)wing incidence anglewing dihedral angle

Step six

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

Step seven

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

Step eight

step 9:decide which type of landing gear is to be used and its disposition

Step nine

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

Step ten

step 11:perform a class I stability and control analysis of proposed configuration.

Step eleven

step 12:perform a class I drag polar analysis

Step twelve

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 142-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.

Step thirteen

-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.

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.

Notes

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

Step fourteen

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.

Step fifteen

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

Step sixteen

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.

Step seventeen

step 18:size the landing gear tires and struts using class II methods.

Step eighteen

step 19:prepare an initial structural arrangement drawing

Step nineteen

step 20:redraw the threeview obtained at the end of p.d sequence I

Step twenty

step 21:perform a class II stability and control analysis using the threeview of step 20

Step twenty-one

step 22:compute the installed power and/or thrust characteristics of the propulsion system.

Step twenty-two

step 23:list all performance requirements which the airplane must meet.

Step twenty-three

step 24:iterate through 17 to 23 as needed and adjust the configuration.

Step twenty-four

step 25:finalize the threeview and tabulate the essential airplane geometry

Step twenty-five

step 26:finalize the structural arrangement.

Step twenty-six

step 27:prepare a preliminary manufacturing breakdown.outline of configuration possibilities:3.3.1 overall configurationconventionalflying wingcanard or tandem wingthree surfacesjoined wing

Step twenty-seven

3.3.2 fuselage configurationconventionaltwin fuselagetwin boom with center fuselageburnelli(give examples)

3.3.3 engine type number of engines and engine disposition3.3.3.3 engine disposition:tractorpushercombination tractor and pusherwithin these three basic arrangements, engine can be installed in the following manner:1-in pods or nacelles2-buriedwhether podded or buried, engines can be disposition on or in:1-the wing: below above or in-line2-the fuselage3-the empennage

3.3.4 wing configuration3.3.5 empennage configuration3.3.6 landing gear type and disposition

Step twenty-eight

step 5.1: check the mission specification for and definition of the type of power plant requiredstep 5.2: draw preliminary speed(or Mach) versus altitude envelope for the airplanestep 5.3:compare the airplane speed-altitude envelope with those and decide which type of power plant provides the best overall matchstep 5.4:determine the maximum power requirement for airplanestep 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.

5.1 selection of propulsion system type:

Having decided on the type and the number of engines to be employed, the next decision is: where should these engines be located?!

Integration of the propulsion system:

step 5.7:decide on pusher ,a tractor or mixed installationstep 5.8:decide on mounting the engines on:1-wing2-the fuselage3-the empennage4-any combination of 1 through 3

step 5.9: obtain the necessary information on:1.engine geometry and clearance envelope2.engine attachment points4.engine c.g. locationstep 5.10:make dimensioned drawings of all engine installation required by your airplanestep 5.11:draw the engine installation in the threeview. The amount of detail here depends on the type of the threeview being drawn

step 5.12:documentwing configurationempennage and landing gear configuration and its disposition.

Questions ?!?!

Engineering

Aircraft configuration