Cooperation in Aircraft Design

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Res Eng Des (1992) 4:115-130 Research in Engineering DesignTheory, Applications, andConcurrent Engineering 1992 Springer-VerlagNew York Inc.

Cooperation in Aircraft DesignA l a n H . B o n d 1'* a n d R i c h a r d J . R i c c i~Manufacturing Engineering Program, University of California, Los Angeles, California, USA; and 2AutomationSystems, Lockheed Aeronautical Systems Company, Burbank, California, USA

Abstract. We des cribe how aircraft are designed in a largeorganizat ion. We discuss the different phases o f designand interact ion with the customer. We then describe themodels used by each specialis t department and the in terac-t ions among departments during the design process . Weobserve that the main design choices are refinement opera-t ions on the design. W e then briefly describe how thenegotiat ion process is control led by an organizat ional lyagreed sequence of comm itment s teps . We then describenegotiation at higher levels in the organization. W hat deci-s ions are made, the compromises worked out , and theeffect of these higher-level commitments on the designprocess .We c onclude that : (I) aircraft design proceeds by thecooperation o f specialists (specialist teams or depart-ments); (2) each specialist has its own model of the design,and m ay use several d ifferent models or part ial models fordifferent purposes; (3) specialists have limited ability tounderstand eac h other 's models . They commu nicate usinga shared vocabulary, but not necessari ly .shared technicalknowledge; (4) design proceed s by successive refinementof the models , which are c oordinated and updated to-gether; (5) the design decis ions, which are acts of commit-ment and m odel refinement , are negotiated by the special-ists among themselves; (6) one way this negotiationprocess is organized and control led is by the use o f com-mitment steps; (7) negotiations occur at higher levels inthe organizat ion, resul t ing in commitments which great lyinfluence and constrain the design process and its organi-zat ion, and which have the greatest effect on the cost ofthe product .

1 Introduct i ont . i The Problem o f Col laborat ive DesignW h e r e a s t h e r e i s s o m e e x i s t i n g p u b l i s h e d r e s e a r c ho n c o n c u r r e n t d e si g n r e q u i r e m e n t s a n d o n c o m p u t e rs y s t e m s f o r t h e s u p p o r t o f c o n c u r r e n t d e s i gn ( s e e ,

Offprint requests: 4173C Engineering 1, Department of Com-puter Science, University of California, Los Angeles, CA 90024-1596, USA

e . g . , [ I ] a n d [2 ]) , we k n o w o f v e ry l i t tl e p r e v i o u sw o r k t h a t h a s r e p o r t e d o n e x i s t in g c o l l a b o r a t i v e d e -s i g n i n m a n u fa c t u r i n g o rg a n i z a t i o n s .

W e p e r c e i v e t h e p ro b lem as to f i r s t describe co l -l a b o ra t i v e d e s i g n , t h e n t o m a n a g e i t (i . e . , t o c o n t ro la c t i o n a n d a l l o c a t e r e s o u rc e s s o a s t o o p t i m i z e r e -s o u r c e u s e , s u b j e c t t o r e a l - ti m e r e q u i r e m e n t s ) . A sp a r t o f t h is , w e c a n t h e n d e t e r m i n e h o w t o s u p p o r tt h i s a c t i v i t y , b y c h a n g e s i n procedure , cu l ture , a n dco mp u te r s u p p o r t .

1.2 Separa te ModelsAn i l l u s t r a ti v e e x a m p l e a r i s e s i n o u r wo rk o n c o l l a b -o ra t i o n i n w i n g s e c t i o n d e s i g n . He re a s t r e s s e n g i -n e e r a n d a p ro d u c i b i l i t y d e s i g n e r i n t e r a c t u s i n g ad i a g r a m o n a C A D s y s t e m . T h e s t r e s s e n g i n e e rn e e d s a s o l u t i o n wh i c h t r a n s m i t s l o a d s we l l t h ro u g ht h e s t r u c t u r e , a n d t h e d e s i g n e r n e e d s a s t r u c t u r e t h a ti s e a s y t o f a b r i c a t e , u s i n g , f o r e x a m p l e , a n a u t o m a t i cr i v e ti n g m a c h i n e . T h e c r i t e r i a u s e d b y e a c h s p e c ia l -i s t a r e p r i v a t e t o t h e m i n t h a t t h e y a r e c o m p l e x a n dc o n c e r n e d w i t h t h e i r p a r ti c u l a r t e c h n o l o g i e s .

In t h e c a s e o f t h e c o l l a b o ra t i o n o f a p ro d u c i b i l i t yd e s i g n e r a n d a s t r e s s e n g i n e e r , t h e p ro d u c i b i l i t y d e -s i g n e r i s c o n c e r n e d w i t h a r r a n g i n g fo rm s a n d f a s t e n -e r s s o t h a t t h e d e s i g n r e a l i z e s ( o r " s i z e s " ) a g i v e nl a y o u t a n d fu n c t i o n , a n d i s p ro d u c i b l e ( i . e . , m a n u -f a c t u r a b l e o n t h e m a c h i n e s c u r r e n t l y a v a i l a b le u s i ngt e c h n i q u e s a n d t o o l i n g c u r r e n t l y i n u s e i n t h e o rg a n i -z a t io n ) . H i s d e s c r i p t i o n c o n c e r n s t h e u s e o f t h e p a r t ,a n d i t s p ro d u c t i o n . T h e p ro d u c i b i l i t y e n g i n e e r t r i e st o m a k e j o i n t s wh i c h a r e s t r a i g h t, a n d a c c e s s i b l ew i t h k n o w n r i v e t i n g g u n t y p e s . H e a l s o n e e d s t ok e e p r i v e t s p a c i n g c o n s t a n t , o r a t l e a s t t o a s m a l ln u m b e r o r d i f f e r e n t r i v e t s p a c i n g s , i n o rd e r t o l i m i tt o o l i n g s e t -u p c o s t .

T h e s t r e s s e n g i n e e r i s c o n c e r n e d w i t h a r r a n g e -m e n t s s u c h t h a t t h e l o a d s c a r r i e d i n t h e e l e m e n t sa r e we l l f o rm e d , i n t h a t i n t e rn a l l o a d i s t r a n s m i t t e dt h ro u g h o u t t h e s t ru c t u re , wh i c h s a t i s f i e s a g i v e n e x -t e rn a l l o a d s p e c i f i c a t i o n . H i s d e s c r i p t i o n c o n c e rn s


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116 Bond & Ricci: Coopera tion in Aircraft Design

loads, s t resses , t ransmission , and techniques fo rf inding them. The stress engineer works privatelywith a f inite element model which calculates loadpatterns satisfying differential equations derivedf rom physica l p rinc ip les . T hese must match the loadtransmission proper t ies o f the s ized geometry .

The comm on language of the i r co llabora t ion issimply a drawing, that is, geometric elements andtheir relations; in addition, indications of what isr ight or wrong with a given geometry, and possiblysuggested changes in the geometry .

In aircraft design, there are many other special-ists, each with their own technology and language.For example , there a re aerodynamicis ts who usesurface models and f low-field equations; there aremain ta inab i l i ty eng ineers concerned wi th access ,d isassembly , and rep lacement ; there a re hydrau l icengineers ; and thermodynamic exper ts . They do no tunders tand each o ther ' s spec ia l iza t ions , bu t theyhave to collaborate to produce a single design ac-ceptable to all .The aim of collabo ration is to produ ce a designwhich is agreed to by each agent. This means thateach agent has a justif ication o f the design that he issatisf ied with. In organizational practice, i t is veryimportant to validate designs. Manufacturing is verymuch concerned with validation, specif ication, andstandardization, as organizational mechanism s. Thedesign must satisfy ' contractual requirements andmust also meet safety and other legal and govern-ment-d ic ta ted requ irements .

1.3 ConflictWe shall ignore any pro blem s of conflict and decep -tion in collaboration, and assume benign, nonantag-onistic collaboration. This is, in any case, what hap-pens in organizations. At a given organizationallevel , one depar tment can assume tha t the in forma-t ion g iven by o ther depar tments i s "cor re c t . " I t isno t he ld responsib le fo r inaccurac ies o r e r ro rs o fjudgm ent o f o ther depar tments . Prob lems of compe-tence and conf lic t o f in teres t among depar tm ents a reusually assumed to be dealt with at higher organiza-tional levels.1.4 Outline o f This Pa perIn Sect ion 2 , we d iscuss how the co l labora t ive p rod-uct design process is init iated by specif ication withthe customer . Sec t ions 3 and 4 descr ibe the d i fferentspecialists involved in aircraft design, the modelsthey use, and their interactions. Section 4.3 drawsconclusions on the overa l l s t ruc ture o f the co l labora-t ive design process . Sec t ion 4 .4 d iscusses model re -

PHASE

~ O N C E P T D E S IG N

PRELIMINARY DESIGN

PRODUCTION DESIGN

MAIN DECISIONSI~equh'eluent sSpex:itic~t&~ns

Fuel/Stores/Engine()ug~l,o, d Sy~telnxhdm~rd Profile

Fuel/Stllres/EnginesFlight Station/EnvirmunentCtm~rots/HydraulicsPrimary Stnu:turM JointsElectricM/B[ack BoxesDetailed Inboard Profile

Sam e as gbow~ exceptDe~ailed parts releasedfor pr(ld u(C.ionDimenslmts with all parts

MAIN TECHNOLOGIES

DesignStr~c~,,r~'~ (Stre~/L~ad ,s ~VCeightsAeronlechanic~Mission AnMysis

DesignAl~rodyl~ulicsStructures (Stress/Loads]Weighg~Al~romechal~icsTllermodyn~mii:sRMar ImagiugI PropulsionR, M aud S

Fig. 1. Design phases, main decisions, and main technologiesinvolved.

f inement. Section 5 lays out a typical completescheme of design goals and s teps in the design ofaircraft to prototype stage. Section 6 brief ly raisesthe issue of higher level negotiation. By higher level,we mea n (1) at a higher level of abstractio n, such aspolicies for choice of materials, and also (2) con-cerned wi th o rgan iza t ion and s uppor t o f the designprocess . Sec t ion 7 summar izes and concludes .

2 Specifying the Produ ct2.I Phases o f DesignThe design of an aircraft usually has three maind is t ingu ishab le phases , Concept Design , Pre l imi-nary Design, and Prod uct ion Design . The m ain dec i-s ions made in each phase and the m ain depar tme ntsinvolved in each phase are l isted in Fig. 1 . Thegeneral idea of these phas es is in relation to thecustomer , the de terminat ion of feasib i li ty , and t im-ing and cost estimates. Originally, a concept designwas suf fic ien t to a l low a commitm ent o f resourcesby the customer . A proo f o f concep t i s tha t a v iab leproduct can be p roduced to per form the miss ion ."Based on th is spec i f ica t ion , we are convinced tha twe can ach ieve th is design a t this cos t ." As a i rp lanesbecame more expensive and the i r in t roduct ion a lsoinvolved major technolog ica l and product ion pro-cess investment , the negot ia t ion wi th the customerbecame more p ro t rac ted . Pre l iminary design in -vo lves a major de ta i led design , perhaps tak ing 50people and s ix months to comple te , and cost ing sev-eral mill ion dollars. Another approach is to designto the po in t o f p roducing a p ro to type p lane . Th is i s


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Bond & Ricci: Coop eration in Aircraft Design 117

so m e t im es ca l led a " d em o n s t r a to r " o r " v a lu a t io n "p r o jec t b y th e Dep a r tm en t o f De f en se ( DOD) .The spec i f ica t ion of the miss ion ma y be genera tedby a mi l i ta ry customer and g iven in a reques t forproposal . For comm ercia l customers , an unso l ic i tedproposa l m ay be made, based on a survey of indust ryneeds made by the a i rp lane company . A commit-men t (e.g. , to b uy 50 planes if they m eet this specif i-ca t ion) can somet imes be ob ta ined .

From the spec i f ica t ion , a concep t design is doneand subm it ted to the customer , f rom which an awardmay be made for the nex t s tep . The nex t s tep i susually not a full preliminary design, but a design tothe leve l o f a paper p ro to type . This i s aga in submit -ted to the customer , who makes a fu r ther award ,usual ly to more than one con trac tor in compet i t ion ,to p roduce an ac tua l p ro to typ e . This i s a p re liminarydesign of the prod uctio n version . I t results in a physi-ca l "demonst ra to r" ( i .e . , an ac tua l p lane tha t per -fo rms to the spec i f ica t ion , bu t which is "handma de") , as wel l as many o th er aspects o f the design ,including:1 . Demonst ra t ion tha t the company has suf f ic ien t

" k n o w h o w" to p r o d u ce th e p l an es .2 . Dem onst ra t ion tha t key types o f people a reavailable.

3 . Dem onst ra t ion tha t the p lane can be made wi thinschedule .4. Demonstration that the plane is maintainable.I f a p roduct ion con trac t i s then awarded , s ince

this is often 2--3 years later , a redesign is done totake in to account new technolog ica l advances , tog ive a p roduct ion design , and to manufac ture a g ivenn u m b er o f p l an es .

2.3 High-Lev el Analysis and SynthesisA smal l team of concep t designers does the f i r s t -cu tanalysis o f the possib i li t ies . Ea r ly ke y dec is ions are :I . Major manufac turab il i ty cho ices .

Material policyFas t enin g p o l i c y - - ty p es o f f as t en e r, wh e th e r t ouse au tomat ic fas ten ing machines , w hether to usesea lan tSizes o f par tsFly by wire o r no t

2. Struc tural design policy.3 . Major i tems of suppor tab i l i ty .

Built- in test equipmentMa jo r sp a re s v e r su s r ep a i r ab le - - r u d d e r s , e l ev a-tors, landing gear , doors, etc.

These dec is ions are more impor tan t than exact ad-herence to schedules . An a t tempt i s made to makea " le vel p lay ing f ie ld" fo r the design by es t imat ingthe three main as pec ts of the design all into dollarfigures:

D E S I G N - - w e i g h t , s t r e n g t h ;M A N U F A C T U R I N G - - m a n - h o u r s , f ix ed a ss et s;S U P P O R T - - m a n - h o u r s , s p a r e s .

The team determines:1. Overall size, weight, and power.2. Basic spatial style and shape or approach.3 . Basic mater ia ls and processes .4. Basic structural philosoph y.5. Fro m the set of missions, a set of scena rios is

developed . These de termine the numb er o f t imesa stress is applied and allow fatigue measures tobe developed .

2.2 Custo mer SpecificationThe customer spec i f ica t ion con ta ins the fo l lowingtypes o f in format ion :1. Store s ( i .e . , cargo) weight, size. There m ay be 20or 30 different type s of stores to be carr ied at anyone t ime.2. At this stage, a descriptio n of a set of missions,which inc ludes speed reg ime, d is tance , t ime in

air , and payloads.3 . Ex treme per formance condi t ions , speeds, acce l -erations, etc.4 . Volume.5 . Per form ance charac ter is t ics , maneuvrab i l i ty ,fuel eff iciency.6. Ta rget cost , profit, cost/e ffect ive design.

2.4 The Initial Cartoo nThe designer takes the ou tpu t f rom the team, andthe customer spec i f ica t ion , and produces an in i t ia lcartoon. The car toon con ta ins the fo l lowing typesof information:1. Lo ca t io n o f m a jo r sy s t em s /co m p o n en t s .2 . Locat io n of major s t ructura l mem bers ( s t ruc tura larrangement drawing).3. Planform.4 . Cross-sec t ion o f var ious cr i t ica l sec t ions;more specif ically:1. Basic geometry .2. Size information.3 . Basic loca t ion of main system s su ch as fue l ,

stores, landing gear , f l ight station, and engine(s) .


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118 Bond & Ricci: Cooperation in Aircraft Design

ACES 11EJECTION SEAT

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FWDWEAPONS ADVANCED

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FWDAVIONICSB AY

FUSELAGEFUEL TANKS

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WINGFUELTANK

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ENGINEFEEDTANKSAFTAVIONICSFWO

AVIONICSBAY F ~ F BAY ~ r " D

APU

L. ARADAR AMAD VECTOREDANTENNA FWD AI R THRUST

WEAPONS BAY REFUELING NOZZLERECEPTACLE

Fig. 2. Surface definitionof initial cartoon given as three-view drawing.

4. Basic location of electronics .5. Wing cross-sections.6. Number and location of engines.7. Basic rada r configuration.The designer gives the cart oon its first main geomet-ric representation as a three-view drawing, wherethe cross-sections at critical sections are developed,as given in Fig. 2.

3 Differe nt Mod els for Different SpecialistsThe set of specialists departments involved in eachdesign phase was shown in Fig. 1. In this section,we discuss the models used by each department ineach phase.Each specialist department constructs, from thecartoon, its own specialized model. A model willusually have a geometric representation, but in gen-

eral will be abstraction, and will contain a lot ofnongeometric information.3.1 DesignerThe main taks of the design department is the devel-opment of three-view drawings, with preliminaryinboard profile. This contains: Loca tion of major systems/components. Locati on of major structural members (structuralarrangement drawing). Planform. Cross-sections at various critical sections.The main task is to develop, update, and maintainspatial arrangements and geometry.3.2 AerodynamicsThe main question being answered by aerod ynamicsis "Will it fly? " More specifically, estimates o f theflight characteristics of the design so far.


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Bond & Ricci: Cooperation in Aircraft Design 119

In the concept design phase, this model is a 2D plan (planform) with minor allowances for airfoil (e.g., angle of

attack of wings) and rough approximations of cross-section areaprogression.The main outputs are lift/drag profiles and effi-

ciency assessments . This gives more exact fuel esti-mates, wing area, and wing sweep angle.In the preliminary design phase, more detailed

models are used. Aerody namic models consist of aconsiderable amount of vehicle description, up toand including some inlet detail and wind-tunnelmodels: 3D surface models. Some 3D flow models (simplified). Sophisticated cross-sectional area progression (for

wave drag).A quadpan model uses a mesh of 3D surface ele-ments , and a full 3D finite eleme nt model is eventu-ally used.

3.3 StructuresThe structures department is concerned with thestrength and structural integrity of the aircraft underall required conditions of use. The structures model is a 3D finite element model is a lumped model (e.g., 2-3 lumped stringers rep-resent 20 actual stringers, 200 degrees of freedom

represent 5000 degrees of actual freedom, parame-ters are lumped) has abstract structural members and abstract plates.In the concept design phase, it is a fairly sparsemodel, u sed pr imarily for rough sizing of main load-carryin g members. Main critical joint s are defined,and main load paths are found. The main outputsgenerated are required cross-sectional areas ofstructural members, and their moments of inertia.The values of loads in each member are found. Fromthese, stresses in each member can be easily deter-mined. The loads transmitted through each joint arealso found.

In preliminary design phase, a model is eventu-ally developed (called a full "bones" drawing),which represents each actual structural member bya modeled structural member: Much more sophisticated external loading models,including a significant set o f flight conditions. Much more detailed structural "bones" model,

including all primary load-carrying memb ers andmany of the secondary load carying members. Significant study done on both critical and second-ary joint areas (not to rivet level). Significant amount of detailed structural analysisdone on critical members, includes crippling,buckling, bending analysis (very local analysis).

In the production phase, detailed individual stressanalyses are performed for all important substruc-tures throughout the aircraft.

3.4 WeightsThe weights departmen t is concerned with the staticweight distribution. Their model contains the follow-ing types of information: A lumped model with point masses and moments

of inertia. A representation o f the 1 g loading configuration(i.e., just to lift off the ground). The cen ter of gravity (cg).

The center of lift (provided by aero dynamics).In the concept design phase, the lumped masses

and moments of inertia represent the main compo-nents of the vehicle. The mod el is used to generaterough 1 g loading for structural applied loads. Man yof these numbers are based upon ph enomenologicalformulae obtained empirically. The main out puts arethe balance (cg), and the total weight.

In the preliminary design phase: Significant detailed weight calculations for 1 gloading. Major vendor part information is used.

Exact x,y,z cg locations are used wh ere possible. Total weight calculations become more realisticand critical, as to meet perform ance requirements.

3.5 AeromechanicsAeromechanics are concerned with the dyn amic re-sponse of the sy stem under given excitation regimes.The model: is an inertia model is generally simpler than a structures model is a stick diagram with lumped masses and stiff-nesses.

It is used to gen erate nodal vibration relationshipsand vehicle stability characteristics. The outputscontain vibration amplitudes throug hout the vehiclefor given flight conditions which are used as multipli-ers for inertial effects on applied structural loads.

In the concept design phase, a simplified mass-stiffness stick model represen ting the vehicle is used


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to generate nodal vibration relationships and vehiclestability characteristics.

In the preliminary design phase: A significantly enha nced mass-stiffness stickmodel is used to de termine stability. More detailed analysis of vibration/stability prob-lems relating to major components (i.e., engine

and wings) is carried out.

3.6 Mission AnalysisMission analysis is used mainly in the concept designphase. It uses parametric characteristics of vehiclelayout to perform sizing iterations to determine opti-mal geometric shape.

3.7 Radar lmagingThis technology determines detectability by radar.The model consists of panelized data used to repre-sent the vehicle shape. The model must be extremelyaccurate and dense (number of elements) in order toaccurately find true reflectance values.

3.8 Thermodynamic AnalysisThis model is concerned with heat absorption, con-ductance, and emittance throughout the vehicle, andhow these affect the structural, environmental, andreliability characteristics of the aircraft. In the con-cept design phase, it consists of a space model con-sisting of major components represented as lumpedmasses as conductors and resistors. In the prelimi-nary design phase, a much more detailed model isused: it contains many components the vehicle is broken into regions and localized systems, such as fuel systems and electri-cal systems, are studied individually.

3.9 Mecha nism AnalysisThe mechanisms o f the aircraft consist of the opera-tion of all moving mechani cal systems in the vehicle.In the concept design phase, the model: defines moving surfaces models landing gear includes control systems and specifies the motion of the large main members.In the preliminary design phase, the model is thesame as above except: motion ranges are defined in much greater detail

minor components, such as hydraulic pumps, areincluded

large attention is paid to fitting working mecha-nisms within volume constraints and structural aspects are studied and determined (siz-ing, life cycle, etc.).

3.10 ManufacturabilityManufacturing specialists are involved already atthe concep t level, as described in Section 2.3. Manu-facturing specialists do not have a separate model,but criticize the main design model. In the prelimi-nary design phase, the main criticisms concernwhether the design could be built in the given fabri-cation shops. Considerations include materialchoices and whether special fabrication processesor techniques would be involved.

During the last phase of prototype design, theyare involved in all the detailed specifications of partsand assemblies.1. Correct specifications for manufacturing have tobe generated.2. Assignments of manufacturing processes have tobe determined. These have to satisfy manufactur-

ability criteria.3. Detailed assembly processes have to be deter-mined to ensure that assemblies can actually be

assembled.4. Detailed cost factors are determined at the partlevel.Thus, in this last phase, there is a manufacturing

model which is the set of process plans for fabricat-ing parts, and the set o f assembly plans for assem-bling them. These plans do not cont ain detailed tool-ing designs, but contain an outline tooling design ortooling concept.3.1t Quality Assu ranc eChecking is done by QA specialists to criticize de-signs.3.12 Reliability, Main tainability ,and SupportabilityChecking is done by RM&S specialists. They use"lessons learned" feedback from the field in theform of case reports, to criticize designs.3.13 Cost Estimatio n and ControlCost specialists are involved in all phases. Theyuse analytical models to derive estimate d costs fro mdesigns so far.


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Bond & Ricci: Coop eration in Aircraft Design 121

4 Interactions Am ong SpecialistsIn this section, we describe the interactions and in-te r faces among the d i f feren t spec ia l i s ts and the i rmodels .

4.1 Inform al Overview of InteractionsAmong SpecialistsWe c an give an overall i l lustration by brief ly describ-ing a typical scenario in a preliminary design envi-ronme nt. At this point in the design, the designerhas developed a shape concept with signif icant detailas fa r as the loca t ion of the veh ic le p r imary systemsand veh ic le sur face components /con tro l su r facesare concerned .A "bones" d iagram determin ing r ib s ta t ions , fu -se lage r ing s ta t ions , major p ressure bu lkheads, ma-jo r jo in ts , and major load carry ing members has beend ev e lo p ed .A typ ica l cours e o f ac tion might be as fo l lows.The aero-engineer , who has a l ready made prev iouspre l iminary runs , now c rea tes a more de ta i led modeland runs the more expensive f low codes to ge t abe t te r fee l o f the veh ic le per formance . He comesback wi th da ta which ind ica te the improvements canbe ma de by m odify ing cer ta in areas o f the veh ic leshape .The designer examines these suggested changesre la t ive to the i r e f fec t on the packaging of the veh ic lesystem s and the suppor t s t ruc ture used to ho ld thesesystems in p lace .

The s t ress eng ineer examines the designer ' schanges to the structure needed to fulf i l l aerody-namic recommendat ions and runs an upgradedstress f inite element model ref lecting these changes.The feedback f rom the FEM analysis i s repor ted tothe designer , denot ing any t rouble a reas which mayarise.The th ree o rgan iza t ions wi l l now si t down to -ge ther , usual ly in a meet ing to d iscuss var ia t ions o fthe p ropos ed changes which cou ld a l lev ia te p rob lemareas . Com promis es wi ll be suggested . Al l these o r-ganizations will then return to their respective disci-p l ines to make fur ther s tud ies on the recommendedcompromises . These new stud ies wi l l necessi ta tefur ther meet ings to reconci le con t inu ing prob lemareas. This i teration process will continue until al lparties are satisf ied that they can l ive with the de-scr ibed changes .

Throughout th is p rocess , t ime and co st o f ana lysisp lay an impor tan t ro le as to the dep th o f analysisac tua l ly under taken and the num ber o f i te rat ionsa l lowed . In the end , these two fac tors a re whatc loses o f f fu r ther developm ent and the developm ent

communi ty se t t les in to a "make th is work" s i tu -ation.

4.2 Descriptions of Input and Output toEach Specialist4.2.1 Designer. The designer bases h is designprimarily on the information obtained from theproposa l spec i f ica t ions . From th is in format ion andprev ious exper ience , concep ts , e tc . , the designergenera tes a th ree-v iew car toon con cep t which fo rmsthe basis o f the f i r st ana lysis . T hereaf te r , he /sheupdates and ref ines the spatial layouts in interactionwith the technology specia l i s ts . Inpu t i s rece ivedf rom a l l o ther depar tments and the designer ' s taskis to constan t ly resyn thesize a good design . Themodel used is a se t o f d rawings, on a CA D system ,which represen t the ac tua l geom etry o f the a i rcraf t ,as i t is estimated so far .4.2.2 Aerodynamics.

Input: The aerod ynamics spec ia l i st wi ll query ge-ometry (2D and/or 3D) fo r spec i f ic geometrypoints (x,y,z), which wi l l be used to represen tthe sur face shape of the veh ic le , and can beused to demonst ra te a i r f low over the sur face .Model elements: From input data, a 3D quadrilat-e ra l g r id o f po in ts wi l l be developed to repre-sen t the a i r f low system about the veh ic le .Output: Life , d rag , and pressure d is t r ibu t ion ofthe veh icle for a given se t of f light conditio ns.From the ou tpu t , the v iab i l ity o f the veh ic le tofulfill the flying requirements will be deter-mined and requ ired changes recommended .

4.2.3 Structures. The ph i losophy beh ind thest ruc tures model i s tha t i t i s c rea ted fo r two basicreasons:1. To prove, through a nalysis, the viabil i ty of the

design (i.e., will the structure fail to fulfill itsstrength requirements) .2 . To help in the optimiza tion of the design ( i .e . ,reduce weigh t , reduce cost , reduce complex i ty ,etc.) .The leve l o f deta i l var ies as the design proc eedstoward grea ter def in i t ion and comple t ion . The rea-sons for the variation in detail include:1. L ack of comple teness o f design .2. Cos t of running analysis.3 . Time requ ired to c rea te and run model .

Input: The s t ruc tures spec ia li s t wil l query geom e-try (2D and/ or 3D) for specif ic geom etric points


8/16


(x,y,z), which can be used to represen t thest rength com ponen ts o f the s t ruc ture . Theseinc lude load pa ths , physica l loca t ions , type ofloads transferred, and strength of load path.St ruc tures wi l l a lso rece ive ex terna l p ressured is t r ibu t ion da ta f rom the aerodynamics andloads depar tments .Model elements: From input da ta , a "bu lk da tadeck" represen t ing the model i s c rea ted . Th isincludes:1. Grid points representing p hysical locations.2 . Connect iv i ty e lements represen t ing the

physica l s t ruc ture th rough which the loadspass.3. Material proper ties representing thestrength and stiffness characterist ic s o f themater ial o f each com ponent .

4. Structura l propert ies representing the physi-ca l shape and s ize o f each com ponent .5 . Appl ied ex terna l loads f rom aerodynamic/loads p ressure curves .

Output: Internal loads and configuration deflec-tions. F rom this output, the viabil i ty of the con-figuration is determined, and required changesa r e r eco m m en d ed .

4.2.4 Weights and loads. The inputs, model andoutputs for weights analysis are as follows:

Input: The weigh ts model i s genera ted f rom sev-eral source s including the central design layout,empirical data based on existing aircraft andvendor da ta on inc luded par ts /segme nts o f theairplane, such as engines, radar systems, etc.Model elements: The model assigns weights in alumped model .Output: A gravitational loading distr ibutionwhich is lumped and /or p rov ides an envelope .In addition, there is a loads group which elabo-ra tes the dynamic load ing cases .Input: The loads data is a direct result of combin-ing aerodynamical ly der ived pressu re d is t r ibu-tion data with different spee d regimes and f l ightcondi t ions which impose cer ta in g fo rces andair forces on the vehicle.Model elements: A lumped model .Output: A set of load cases.

4.2.5 Aeromechanics. The inputs, model, andoutpu ts fo r aeromechanics analysis a re as fo l lows:1 . The aeromechanics model i s der ived f rom thecompo nents o f the th ree-v iew crea ted by the de-signer (determines st iffnesses) and the I g weights

developed by the weigh ts g roup .

2 . The model i s a s impler lumped model represen t-ing the basic structure only. I t typically ignoresmajor systems and has fewer s t ruc tura l membersthan o ther s t ruc tura l models . I t uses lumpedweights and inertia.3. Mathematical st imuli are applied to the result ingmodel to de termine sy stem v ibra t ion and s tab i l i tycharacterist ics for each f l ight condition. This isused to make recommendat ions on a l te r ing theparameters o f s t ruc tures in the wing and fuse lage .

4.2.6 Manufacturability. During design, manu-fac turing spec ia l i s ts re la te to the c oopera t ive designprocess more as checkers wi th ve to ing ab i l i ty thandesign drivers. They act to stabil ize cost and t ime.

Checking is done by m anufac tur ing spec ia l i s ts tocrit icize designs.Input: The main design model .Output: Cri t icisms of the fo rm of ve to ing or sug-

gested modif ica t ions o f g iven aspe cts o f thedesign.

Dur ing the las t phase o f p ro to typ e design , theyare involved more interactively in all the detailedspeci fica t ions o f par ts and assembl ies .

A lot of manu facturabili ty cr i t icism and cons traintis actually ach ieved from the training of central de-signers in the principles o f man ufactura bili ty; in ad-d i t ion , there a re design handbooks, used fo r theguidance of designers , which con ta in manufac tura-bil i ty cr i ter ia. Thus, the interaction is via the transferof knowledge th rough educat ion .4.2.7 Quality assurance. Checking is done byQA specialists to cr i t icize designs.

Input: The main design model .Output: Cri t ic isms of the fo rm of ve to ing or sug-gested m odif ica t ions o f g iven aspe cts o f thedesign.

4.2.8 Reliability, maintainability, and supportabil-ity. Checking is done by RM &S specia l is ts to c r i ti -cize designs.

Input: The main design model .Output: Cri t ic isms of the fo rm of ve to ing or sug-gested modif ica t ions o f g iven aspects o f thedesign.

4.2.9 Cost estimation and control. Cost spec ia l -ists are involved in all phases.Input: The main design model .Model elements: Cost estimates for assemblies.


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Structuresbiggerwingbox "~more ibsI, momentA ..... s:ctio o~

baiancetotalweight

Weights

i speed egimevolume, weightdistance performanceI a~oon j

Aerodynamicsmoreexact

g f~ el estimatewingarea/ sweep ngle/ geometl]-o4net

FinalConceptualDesign

mission

inertiadistribution

[ Aeromechanics

F i g . 3 . C o n c e p t u a l d e s i g n .

Output: Cost estimates for given aspects of thedesign.

4.3 Overal l S tructure of the Des ign Process4.3.1 Interac ting specialists . During conceptualdesign, the initial cartoon is refined up to the pointof a fairly detailed layout. During this process, thespecialized models are constructed in their initialforms, and then also refined so as to reflect andto incorporate the changes and progression of thecentral design. This is diagrammed in Fig. 3.Further, the sets of experts involved graduallychange as the design proceeds. Some leave and somejoin the dance.4.3 .2 Coordinated ref inement o f models . Theprocess of refinement, where each specialist refineshis model, and works to keep his model up to datewith the central model, is depicted in Fig. 4. Thisalso shows the input of specification changes, andtheir distribution to the relevant specialists.

4 .4 Mode l R e f inemen tA model may be changed to correct it, but most ofthe changes are in the ref inement of the model. Wegive some examples of refinement:

specialistmodel

i specificationchangesspecialistmodel

model changesevaluationssuggestions1\ 1\ /\

refinement refinement refinementF i g . 4 . T h e p r o c e s s o f c o o r d i n a t e d r e f i n e m e n t o f m o d e l s .

4.4 .1 Envelope to more detai led geometry. Theinitial model specifies an approximate volume,which can be an envelope or a bounding cuboid forthe refined model.4.4 .2 More exact numerical es t imates . As an ex-ample, fuel capac ity 15,000 gal is a repr esen tati on ofan interval such as 14,000-16,000. A more exactestimate migh t be 15,500 gal, which might at thislevel of refinement corresponds to the interval15,250-15,750.4.4.3 Single to multiple eleme nts. The mappingfrom the initial model, which lumps elements intoabstract elements, may not be a direct expansio n ofeach element into several more detailed elements.We have depicted a lumped model with four ele-ments being expanded into a more detailed modelwith 14 elements. We also show that single elementexpansions have to be merged to produce a refine-ment, and that additional elements may be addedduring this process.4.4.4 Puttin g in explicit fuel , pow er, and hydrauliclines. These may have a nonnegligible diameterand other requirements and ma y need to be consid-ered at a nondetailed level.4.4.5 SuJface geom etry specification. Surfacesare at first approximated by a series of definingcurves comprising planar cross-sections and pri-mary longitudinal lines. Finally, these are convert edinto surface patches in which the areas betw een thedefining curves are mathematically defined. Theanalysis models represent these surfaces using pla-nar facets connected to x , y , z coordinate data.4.4 .6 Ar t iculat ion and fas tening. A 3D form willat first exist in a simplified shape, and will then berefined, and optimized for man ufacture , by articulat-ing it into an assembl y of compone nt parts. This may


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124 Bond & Ric ci: Cooperation in Aircraft Design

CustomerProject management

D ~ i g n ~n d sys%ems

LoftI Aerodynamics

Propuls ionWeights

Generate requi rements .Prom customer requirementsand advanced technology assessment ,coordinate configuration concept,Generate ba~e|ine rawings ,genera l ar rangement ,inboard profile(suppor t tool - CADAM}Wing propor t ions + (~ ) Wig chord lengtb/sut face area .(b) thickness/chord tength~ (c) Aspec~ Ratio.Empennage s ize ,Thrust to weight r~ t io T/W.Engine selection~ ta,nge of cycle parameters.Engine installation criteria.Approx gross weight . Approx em pty weight .Strtlct ure~

Ae~omechanics

Mater ia ls and producibi l i tyModel specificationsLaborator iesEngineer ing shopPl ight tes tOther d isc iphnes

Evaluate configuratiou for{I) oad paths for low costl ight weight s t ructures , and(2) reasonable and consistent design parameters,Provide criteria guidelines.Par t ic ipate in des ign:11) evaluation for loads(2) aeroelastic and flutter effects(suppor t tool - loads programs) ,

Fig. 5. Step 1: Initial design parameters.

require specification of fasteners for stress calcula-tions at a nondetai led level .4.4.7 Sizing ofparts for structural models. Sizingreplaces a center l ine specification by a volume ge-ometry. This m ay at f irst exist as a width and heightspecification only, and then an exact cross-sectionalgeometry. After this , modifications such as l ight-ening holes may be added.4.4.8 Addition of elements. Some e lements mayhave a simplified representation at the initial level,and thus the model is refined by enhancing them. Anexam ple, in the design area, is of adding the cockpite lements such as seats and conso le . There may beintermediate refinements, such as specifying theangle of incl ination of the back of the seat, and thepi lo t ' s v iewing window.

5 Organization of Design Using Comm itted StepsThe w ay the grouping of design departments is usu-ally organized is related to the schedule steps indesign. A step is defined as a set of design choicesthat must be committed to by a given time.5.1 Steps in Advanced Aircraft DesignWe show, in Figs. 5-13, an organization into s ixsteps som etime s used in aircraft design. Th ese stepsare:1. Initial design parameters.2. Generate data/prel iminary point design.3. Parametric and trad e-off analysis.

CustomerProject managemettt

Design al~d systems

Give approval at design review.Change configuration collcept,revise design par~lueters,do design review.Update genera l ar rangement ,update inhoard prof i le ,find wetted areas andarea dis t r ibut ion,functional systenl8 considerations(1} flight controls (2) fuel(3} hydraulic (4) electrical(5) avionics (6) environmenta l cont rol(6) weapons.(Use0 CADAM support tool).(May use Asset suppor t tool ) .Produce updated basel ine drawings ,genera/ arrangements, inboard profile,Loft

~ - d y x ~ a a n i c s D e t e r m i n e(1) eppennage scal ing data (2) drag data(3) low speed lift data(4} control surface sizes.{U~es aerodynamic programstPropuls ion

Weights

- S ~ t . : t u r ~

Aeromechanics

~aTer ia ls and producibi l i tyModel specificationsLaborator ies-E'~l~gin ar ug shop

Fl ight tes tOther disciplines

Determine(1) parametr ic ins ta l led engine ,performance data versus(a) overall pressure ratio(b) bypass ratio(e l turbine ent ry temperature(2) Loom flow field col~ditions(3) in le t and exhaust nozzle performance data(4) Scal ing data(5) Ins ta l led engine weigh data(6) Performance and weight scaling7} Ini t ia l s t ructura l temperatures .(Uses propuls ion programs} .Determine(11 component weight relationship~(21 payload and operating equipnmnt weights(3) effects of configuration peculiar items(4) C.G. location and limits(5) F~el volume relationships.(use mass dis t r ihut io~ tool}Define structural design criteria.Perform trade-off studies to define(1) basic structural concepts(21 material usage,Provide effects on asset weight equation~due to (~ s t ructurM technology(b) s t ructura l ar rangements(c) s t ructura l des ign requirements ,Provide parametric basic loads.Par t ic ipate in des ign evaluat ionPreliminary aeroielastic assessment.(use loads programs, deta i led load~ programsand aeroelas t ic program)

Fig. 6. Step 2: Generate data/preliminary point design.

4. Detai l point design studies .5. Refine selected configuration.6. Design and build prototype.Within each step, and for each goal , we indicatewhich of the many avai lable com puter support toolsare used.

5.2 Commitment StepsWe summarize the above s ix steps in Fig. 14.5.2.1 The concept of commitment step. As dia-grammed in Fig. 15, the notion of commitment stepis that a set of joint com mitm ents is made by al l thedesign agents at the end of each step. These arepublic commitments to best estimates for decis ionchoices. These estimates are then used by al l agentsduring the next step.


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Bond & Ricci: Coope ration in Aircraft Desig n 125

C u s t o m e rPro~ect management Determine trAde-off m~trlx,D o d ~ i g n evMnation,Design and sys tems Study powei p lant s i/ee , wing ~nd eppel tage s ize ,fllselAgc size, basic alrfrKtlle geometry.controls ~ ld avionics ,(m~y u s e C A D A M ) .M~y do Asset s tndy (Asset tool}.LoftArod--~y namics Study ms, euvr abi l i ty ,acceleration, ~ate of climb.ceiling, off-design mission c~pahility,range/ fuel consumpt ion,o p t i m u m t h r u s t to weight (T/W} raticx(use aerodynamic programs) .Proptf ls iou Study engine cycle and s ize .lift engine size.( se propnls ion programs ),Weights

St ructuresAeromechanies

Matet iMs en d producibi l i ty

Model specifications

Study gross weight ,empty weight , s t ructura l w eight ,sys tem~ and subsystems weight .propulsiotl weight, fuel volume avail~ble,filel reqairt.~d, eff~mts of advanced technology.effects of configuration chan ges,maximum take-off weight ,(use mass dis t r ibut ion program).Determine strlt(:tura], conlponent/nlatt~ri~l nlatrix.Pxovide parametric basic loads.P~rtieipeAe in desig*~ eval uatio n,Parametr ic ~erolast ic assessment .(use detailed loads programs and aer(mlasticity l)rograul)Study eltghteering cost~Study acquis i t ion of(I) product ion m~ter ia l ~ut labor .(2) tool ing, (3) sparesStudy opera t ioual e~ ts :(i ) maintenance, (2) replenish spares.(3) fl~el and oil. and (41 pay and allowances,Produce estilll~.h~ of total system cost.

L~bor atoriesEngineer ing shopFl ight tes tOther disciplines Acoustics - side lim~ noise.flyover noise, ~lt(t footprint noise.

Fig. 7. Ste p 3: Parametric and trade-off analysis.

5.2.2 E stimates and decisions must form an ade-quate sequence. Each s tep produces es t imated re-sults within intervals that are sufficient to al low ev-ery agent in the fol lowing step to achieve its goals ,viz. , estimate d results within the accuracy or inter-val required for the end of the next step. Thu s, foragents a , b, c, and d, i f after step i they have pro-duc ed results in intervals I a, lib, IF, and I~, and if the yhave private results U/, P~, PT, and P/~, then P~, and{ ~, 17, and I f} as input for agent a should be sufficientto allo w the com put atio n of PT+~ and P~d~, and P~I bnd { i, I~, and I d} as inp ut for agent b shou ld besufficient to al lo w the compu tation of P~+~ andI)+ ~, and so on.5.2.3 The publ ic estimated results are the contextfor design action. The public estimated results , atthe end of step i , are the context for design action instep i + 1.

I a}I/} and P?} ---> P~+ i an d I~+ 1IF}1/}

Custo mer Give approval at end of st(~p.Project managemen t Select deta i l point des igns .desigtl review, andrevise design parametel's,Design and sys tems From conf igura tion des ign,genera,re preliminary coueepts.i.e.. general arrang ements and inh oard prldiles,Update genera/ arrangements and inboard profiles.consider configuration pe~:uliar items(e.g., r~dar, weapons, p~yload).dl~t~Illlilte wetted areas, and area,R di.~tributi(m.Make layouts for(1) flight co ntrols sy~tent(2) powerldant instMlation(3) ~tructural arr~,ngenlent(4) t~l~ding Rear(5) crew s ta t ion(6) fuel system(71 hydraulic system(8) electrical system(91 avionics system(t0) r111viroltlnent~l (xmtrd sys tem( 11 weapons sys tem(12) miscel laneous equipment(13) nlec](uses CADAM).Produce i lpdated concept drawings .inehldi I tg genera l ar ra l tgenmnts .inlmard profiles, ~nd layouts,

Loft Develop loft surface.(uses CADAM).Aerodyll~mic~

Propnl~km

Weights

Determine(1) drag lnfiht up(2) matmuvcr envelope V-N die,gram(3l control surfa,:c size(4) pr imary miss ion performance ~nalys is{5) airport performance(6) flight envelope{7)(8) C,G. range, loadahility19) preliminary failure amdysis.(us~s aerody umnic progrexms Kiid transmdc ~nalysi~},II~,fine(1) engine selection(2) insttdled perfi~rnt~nce dat a(3) inh~t and nozzle size andiustMl~tioll configur~th)I~.Determim~:(l ) Fm~l sys tem s iz ing requirements(2) Initial auxiliary system requlrenltmtsalld defiaition.l~(dhle structural telnl)eraturcs.Duternlhle transient telllper~turtr ~udhistories (ff structurM COlll])ont!lltS.(Uses propulsion progi}uns anddetailed propulsion progr~uns}.Determine(1) group weight statel,t~nt(2) prclim lnary ma~ss distribu tion~tltd lllolllellt of iaert ia dataI3) C.G, travel analysis.Do tr~tde-off studie s, effects ~f advan ced techtvdr~gy on(1) materials(2) type of constructioll( 3 ) active cont rols(4} propulsion,tUse~ ma-4s distribu tion progr~nl).

]Fig. 8. Step 4: Detail point design studies, p art 1.

Example:approx layout}control surface size}engine weight and size}payload and c.g. limits}basic structural concepts} --~

structural component/material matrixparametric basic loads}

5.2.4 There is a main overall pattern o f depen-dency. As shown in Fig. 16, there is an overall


12/16

126 Bond & Ric ci: Cooperation in Aircraft Design

Structures

Aerollmcll&llics

MMeri;ds ~,nd pmdtlcibility

Model spel;ificat ilnls

Lal)oratoriesI Engim!eri~g shopFlight testOthm" discilllilms

Expand and refine trade-off studiesto define( 1 ) detai l str uct ur~l design concepts(2) materiM usage(3) design/m~uuf~cturi~g p~rameters.Generate basic struetllral arraugements.Perform analysis to size basic st rm;tural eleme~lts:(1) internal loads distribntkm altalysi,~(2) Stress analysis for strellgth altd stiffness(31 fatigue and fracture anMy~is for durabilityand damage tolerance(4) thermal stress ~malysis(5) sonic fatigue analysis.Provide imdhuinary hea~ic loadsDetermine stiffness data for a~troeleastic anMyses.Colldllct structural concept tests,(Uses NASTRAN and FAMAS},Provide(1) aerodastic stability derivatives(2} flutter analysis(31 aeroela.stic evMuatiml o{ perfotnt~uce requiremeuts(4} acoustic ellvirOlllllent(51 loeala ~u~d crit eri~ repor t(6) eugim~ k~4ds analy sis(7) l andin g g~ar toaxls {it design {it} fatigue.I~xpaml and refine trade-off studies(1l effects o{ C,G travel(2) det ail stru cturM design load.~ trite!fla.(Uses detailed loads p~ogralllS, aero,,Iastic p~ogl~llland detail ed aerolttechanics prograuts),Select(1) materiMs and processes(2) parts alld equipnmnt.Refine lIlallllf~ctllrillg breakd,,wn,Provide producibility design support,Perforlll cost trade-off studies.Deterlnim~ lift: cycle costs.hlelztify test requirem euts,M~ke smoothness drawings.Deterlnim~(1) configuratiou parame ters(2) Lockheed design requirements(3) Perfor malice p~rameters.

Techifical discipline evMluttiml(I) military systems - inission pt?rfl)rlttance(2) human f~ctors(3) reliability(4) vnlnerMfility.

Fig. 9. Step 4: Detail point design studies, part 2.

dependency pattern, which is more or tess repeatedin each step.

6 Higher-Level NegotiationThe elaboration of the design by n egotiation of spe-cial ists is preceded by and constrained by negotia-tions that occur at a higher level of abstraction, andof organizational management. These decis ions de-termine choices which control the overal l decis ionson the aircraft and also the means by which the restof the design is carried out.

Negotiations are carried out not only within oneorganization, but also among teaming partners. De-cis ions have to be made concerning:1. Who wil l do what.2. What is required.3 . Sys tems .4. Communication.5. What kinds o f data and its format.6. Security in data move men t.7. Set up procedures.

Pl'ojec t 111ll~g(:ll1811~ systems

Loft

Aerodytt~tmit s

Pmpul~ion

Giwt Approval at eud of step,Maintain solected configuration,do design Ieviews, revist~ desigll p~ttallmters.(1) general arrangements(2) in I~ard profile(3) cmtfig~ratiomd peculi~sr itenl~.Make detailed layou ts for(1) wimt tunnel modeL~(2) mock-ups ~nd colllpollellt testing.Detailed layouts:(I) flight control system(2) power plant installation(3) stru ctural arr~ngenlex~t(4) Ianding gear(5) crew station16) fuel system(7) hydraulic system(8) electrical system(9) avionics systems{10} ellvironmelltal colltrol systell~(II I weapons system(I21 miscella~mous equipmtmt(131 umehal~isms.( ~)se~ CAD AM) .Produce updated drawings.Provide loft contours for mock-ups,wimbtuunel lnodds andCOlllpOllell~ testing .(nses CAD AM and CALAC()}.Define and direct willd-tllnuld test program.Flight COlttrol systellt - priamtry a nd ~XlltOltl&tlc.Upd~tte dr~g build-up per Willd-ttlUlie[ results.Prepare stab ilit y aml COlttrol reports,Control surface sizillg, upd ate pet wimt-tunnel results.Prepa re perfornlau,:e rel,o~.t,~.Airp ort perfurnlance. UlldMe per wlnd-tunnel results.Rx~fin,' flight envet~pe t~llff~!t bonndark~s.Fdm,ct of .qtorl~s, IIpd~t~, p0r wiltd-t llllllel rt~llltS .Fligh t simulations, ~xm~p~tter ~nd piloted.D,~v,,l,p gn~r~nte,,s.l~efi~e fitih~re analysis.{U~es aerodynamic programs.trensonk: a~mIysis program and ADAIS}.D~tine ~nd l:o~ld~tctwilld-ttlltm:I, te~t,Prepare, ~llgil/c perftlrmcmce reports.FiltMize iulet, llO~Z1callt[ lteu:elle ocatiou.Upd ate ixtst~dlatiou Iossos per wind-tnnuel resMts.Engine coutrol-systeln lllodld8~Thrust lllallagelnelit ,qystl~iii.FinMize auxiliar y systems rt~qllitelltelltsaml definitiolt:(1) envi~mlnlentM (2) antidcing(3) auxiliary power 14) engilm st4~rtlug(5) w~uts and draius (6) tlm lst reverse.D,,tail stru ctnr al tellllmr&ttlteS ~.lld tem per atu re gradients.(Uses propulsion progr~mls l, 2 and 3}.

Fig. 10. Step 5: Refine selected configuration, part 1.

In the context of a long-standing cooperative rela-tionship, the aim of negotiation is to f ind a win-wincompromise with which al l partners are comfort-able. This is particularly true within the sa me organi-zation, or among suborganizations within one orga-nization.

6.1 High-Level Engineering DecisionsAn example of this is the choice of materials to beused in each part of the aircraft. In the case of themajor redesign of the P3 to produce the P7, eachpart of the aircraft was examined to determine thematerial to be used. There were a large number ofparts analyzed and decis ions were usual ly amongcomposites , aluminum and high strength aluminum.These choices were made by examining s tate-of -the-art manufacturing costs and also the avai lablepossibi l i t ies for composites . High strength alumi-num al lows one to reduc e the skin gauge, giving less


13/16


Weights

St r tt(;tures

Aerolnechatdcs


Lahoratories

Engineering shopFlight testOther disciplines

Detail estima ted weight aad balance report.Define specification weight with cus tome r/ma rket ing.Evalua te c~st/weigh t trade-off studies.Mass distribution per final I:oufigut~tionincluding variations ill:(1) fncl (2) 1,ayh~ad(3) distribution for criti cal loading.Fuel ~e~SllS~ttitude.(Uses mass distrihu tion program slit] fuel iner tia i)rogram).Colltillll(} trade~offs to define:(1) detail structural design concepts(2) triateriMs usage (3} producibility methods.Oellerate. detail structu ral arrangeluen{s.Expand and refine stHictural element sizhlg anMysis( 1} nternal loads{2) streagtI~ and stiffne~(3) durability and d~mage tolerance(4) thermM stress (5) sonic fatigue.Refine stiffness d at a {(>r aeroe lasti c analysis.Colltilltle structurM tests.Plan fo* pro toty pe devetopme~t analysis t~lld test s.(Uses FAMAS and N A S T R A N ) .Refine( t ) aer(~dastic stM)ility derivatives(2) basic loads (3) flutter analysis(4) a emelas tic pe.r~ormante analysis(5) aconstic el~vironlllent{6) loads and criteria report(7) aertmlastic optimization(8) engine loads analysis(9) wind-tuunel tes t program for loads.EstaMis h structurM design lo~uls criteria.Define alld Collduct low-speedwind-tullnel f lutte r model progranl.(Uses detailed loads programs,detail ed aerolllechanics programs ~ndairframe/ground interaction i)rogr~lu).Refine(i materials and process selection{2) parts and eqlliplllellt selection.Continue (l) produeibility design suppor t{2) cost trade:off studies.Prepare(i customer desigu requiremen ts(2) Lockheed design requirementsf3) ellstolller pecul iar COllfigllr&tioll requirel/tel/ts(4) performance guarantee s (5) weight guarantees.Build COl.ponellt test rigsper eltgineering requirenmnts.Conduct Ct)ltlpOltent tests.Design and huiM flutter models.Do flutter model tests,Design a.lld build wind-tunnel nlodels.Do willd-tullne] test s,Build mock-upsper engineeriag requirelnents.Tech nicM"discip in e s analysis(i) military systems- mission per[ornlance(2) human factors (3) ~eliahility(4) wflnerability (5) survivability

Fig. 11. Step 5: Refine selected configuration, part 2.

aluminum in the wing; I0% stronger material maysave 8% weight.

These higher-level engineering decis ions are tosome extent negotiable later; however, renegotia-tion is costly and difficult, and is thus discouraged.The m aterial decis ion thus can b e regarded as a goalto be attained. In the elaboration of the design, som egoals wil l be attained, and s ome wil l fai l to be exactlyachieved. The p roject is then managed so that partsof the des ign which overachieve com pensate forthose that underachieve. The attainabil i ty of thesedesign constraints produces vertical confl icts andrenegotiation among levels of the organization, andit can prod uce con tractual confl icts among differentorganizations.

Cnst olner Give approval and acceptance,Proj ect lll~lti~elltent Prep&re proposal,do (:llStOnl(~r review ~iid Lontl' ~ct @WP*I(IFinalize design requircnmnts.Determine lllodifi{:atiolls required.EvahllitiOll of r~qllirelnoltts.Dcsigu ~utd syst(~lns PinMize:t l ) gellt:/~ glrsugellletlt~(2) inboard profile(3) coufiguration imcnliar items.Colttplete and rdea se prototy pe drawings:

(I) flight control system(2) power plant iltstMlation(3 } strui:turM arra41gements(41 I~nding gear (5) crew station(6) tirol system (7) hyd~mlic system(8) electrical sy stem (9) avionics syst em(10) euvirollnmllta| col~trol syst em(II) weapons system{12) iniscellaneous equipmentf 13) ~mmfianisms.Produce prototype drawings.(Uses CADAM),Loft Provide loft COllt0Rrs o desigll and nlanllfacturing,(Uses CADAM and CALACO ),Aerodynamics

Propulsi


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128 Bond & Ricci: Cooperation in Aircraft Des ign

Aetomechalti(;s

Material~ ~utd Im~ducibility


LMmratories

El~ghtecring shopFlight test

Other disdptilms

Finalize:(1) aerolastic stabil ity derivatives(2) aerolastic pm'formance(3) Imsic loaxls{41 Flutter analysis(5) Acoustic tzeatment(6) Eltgine loads analysis(7) Landing gear analysisDefine:(1) Flight test pt'ogram forloads validation(2) Ground and flight test programsfor flutter substantiationIn-depth lomls aild criteria reportAerolo.stic optin~izationDefine and condtlct high speedWilld-tllllltd flllttet ntodel programFlight test lialsol~(Uses detailed loads programsdeta iled aeromechauics programsand alrframe/ground interatction prograln)Fiualiae materialsand pro(:e~s selectionFinalize parts amteqtliplnellt selectionSpecitications amtstandardsColllll/on a]it y studies:(1) forgings and extrusions{21 parts, equipln(mt. (:olltpone~ttsIdentify long lead i temsDesigl~ to costl)rogtam inl plemellt ationFinalize:(I } cllstomer design requirements{2) Lockheed design requirenlents(3) custonmr ptmuliar requirements{41 perf)r~l~ll(x? gu~r~ilte es{5} weight g~ta~'~tteesContiltue wind-tllnnel teatsof prototype configurationCOlltilltl(! conlpollent testsof prototype ~:oufiguratimiphul ~lld exe(tlttestatic: tests of prototypeVchlclc systems simulatorPlight simM~to:sC(Jll~lllu(~ q,utter inodel testsR evi~e mock-upsto protntype configuratioltPlan flight test programNxt]cit~t~ iight te~t programper ellginec~riltga.n(t(:llg~Olll(ir reqll Jrt~lllt~ntNTechuicM dis:iplinesfinalize reconllnelId~tions all~t reports(1) l l l i l i tary systell ls - inissioll I)er[orln&Itce(2) human factors{3) reliabil ity14) vuhmrabilit yt5) survivabi(ity(6) nlaint ainabilityMallufacturiug buihts prototype(Usi~ig CADA M}

Fig. 13. Step 6: De sign and build prototype, part 2.

tremely complex. Whereas for sheet metal , a wingsection would require about 10-15 detai ls in adrawing, for composites i t requires perhaps asmany as a hundred details per drawing. There isthe basic plan view of the wing, but then manysections showing the ply structure to be used. Thisinformation has to be used by manufacturing inmaking the wing but also by engineering in doingstress analyses. The plys in each section fal l intoplysets, which are in a certain spatial order. Thedrawing specification was first negotiated betweenthe designers and manufacturing and a set of plytables was added to the drawing. These gave theply/ID, the material code and the angle of the plyto a reference axis . These ply tables were used bymanufacturing to layout and cut ptys. However,this data form did not allow engineering to createa model for stress analysis without a lot of extrawork. What was negotiated was a drawing specifi -cation change in which the plysets were added toal l cross-sections of drawings and detai ls , togetherwith the plyset order. From this data form, themanufacturing ply tables could be then created.Since creating both types of data was extremelytime consuming, a software tool was specified tobuild the manufacturing ply tables automatically.This tool was budgeted and scheduled to take 3months to implement and test. During the transitionperiod, the designers would generate both types oftables . The payoffs were that engineering saveda lot of work and minimized the possibi l i ty fortranscription and transformation error, manufactur-ing sti l l got what they needed, and designers even-tual ly saved some time in generating section plytables which were more natural for them to de-termine.

Computer links. For transferring data, tapes orTP l ines, and, i f so, how big? Who wil l control themovement of data, which computer managers?Security. Accountabil i ty in moving data, docu-mentation to be generated, who wil l s ign, whererecords will be kept, the security organization re-sponsibility.

The design is optimized to the limits of the toolsthat are chosen.6.2.1 Example. A recent e xample of informationhandling negotiation, which occurred betweenLockheed Burbank (where the product was beingdesigned and engineered) and Lockheed Georgia(where the product was being manufactured), con-cerned what specification was to be used for draw-ings of composite wings. These drawings are ex-

7 Summary and Conclusion7.1 SummaryWe described how aircraft are designed in a largeorganization. We discussed the different phases ofdesign and interaction with the customer. We thendescribed the models u sed by each special ist depart-ment and the interactions amo ng departments duringthe design process . We observed that the main de-sign choices are refinement operations on the design,and we discussed refinement.

We then described how the negotiation processis control led by an organizational ly agreed seque nceof commitment s teps .

We then described negotiation at higher levelsin the organization. What decis ions are made, the


15/16


DESIGNA N DSY STEM SL O F TAERODYNAMICS

PR O PU LSI O N

WEI G H TS

STR U C TU R ES

AEROMECHANICS

MATERIALS AN DPR O D U C I B I LI TY

MODELSLABORATORIES

S T E P 1INITIAL DESIGNPA R A M ETER Sbaseline drawingsinboard profile

wing p~.r~mett;rsthrus t /weightratiormage ofcycle paranlctersinsta/lationcriteriaapproxi lnat eweight, e.g.

load l)adtsdesigu parmm:tcrs

providecr i t er iaguidelines

STEP 2PR ELI M I N A R Y PO I N TANALYSISgeneral ar raugenlentsupdate i l tb~rd prof i l eftlnctiOllal systemconsiderations

I drag datacontrol surfacesizesperforlnallce dataweighttenlper~tures

payload andolmratil lg equipnmute.g, l imitsfuel~volmner(~ati(mshipsdefine structuraldesign exiteriabasic stru(:t l lrale(nH~}tsprovideparamet r ic1)a~sic oadsprelitninaryaerolastic itSSt?SfiItI(11

S T E P 3PARAMETER ESTIMATI()NTRADE-OFFSupdated layouts

maaoeuveral~ili tyrange/fueloptimum thn~st/weight ratiostudy engine cyclealtd size

structural weightsubsystems weightpropulsion weightfiml-volmuedefine structuralCOml)Oneatnlateri~l l l latrix

pa4rglnet ic basicloadsl)aranletrh:aerol~stic assesmltentstudy ax:quisition ofl)r~duction l aboran d tools(~Stillla t(! t/)t~4[sygtelll cost

S T E P 4D ETA I L PO I N TSTU D I ESupdated layoutsflmctionalsystems layoutsdeveloploft surfacecontrol surface sizesdrag bui ld-upc,g, remge, loadabilityrefine engine selectioninlet m~d nozzle sizefuel system sizings t ructural t emperaturespreliminary in~ss distributionmoment of iner t i a datac,g. travel analysis

refine trade -off aa, mIysish~sic s t ructu ral gr~,llgelllel~tssize llasie strt l


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130 Bond & Ricci: Cooperation in Aircraft Desig n

DesignCriteria(proposal)+Propulsion+Aerodynamicscharacteristics J

DESIGNi!

AERO " ~ DESIGN f 'a ~ DESIGN ~--| -- i---W E I G H T S ~ LOADS q~STRESS . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . .. . . . ~ " " STRESS

Fig. 16, The main overal l pat tern of dependency.

7. Neg otiat ion oc curs at higher levels in the organi-zation, resulting in commitments which greatlyinfluence and constrain the design process and itsorganization, and which have the greatest effecton the cost of the product.

Acknowledgments. We would l i ke to thank Dave Cannon, Bi l lThompson, and Dave Richardson of Lockheed Ai rcraf t Com-pany, Bm'bank, Cal i fornia , f or d i s cuss ions on wingsection de-s ign, and on col l abora t ion in manufactur ing organiza t ions in gen-

era l . The UCLA Manufactur ing Engineer ing Program i ssuppor t ed by gi f ts and grant s f rom man y corpora t ions , and by theIns t i t u t e for Manufactur ing and Automat ion Research.

Referencesl , Duvvuru Sr i r am, Rober t D. Logcher , an d Shuichi Fukuda.

Proceedings of t he MIT-JSME Workshop on Coopera t iveProduct Development , 1989. Held a t MIT, Novem ber 20- -21,1989.

2 . Alan H. Bond. The coopera t ion of exper t s i n engineer ing de-sign. In Distributed Artificial Intelligence, Volume H, pages463-484, 1989.

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Cooperation in Aircraft Design

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