32 AEROSPACE AMERICA/NOVEMBER 2015 Copyright 2015 by the American Institute of Aeronautics and Astronautics

by Dianne J. DeTurrisddeturri@calpoly.eduandSteven J. D’Ursosjdurso@illinois.edu

As impressive as it is to beam back images of Pluto

or to whisk passengers around the globe in comfort

and safety, the systems engineering practices

underlying these products won’t be adequate

for a future of ever-evolving complexity. Aerospace

engineering professors

Dianne J. DeTurris and

Steven J. D’Urso, members

of AIAA’s Complex

Aerospace Systems

Exchange forum, explain how lessons from the

software industry can help aerospace engineers

manage complexity.

Back in 2001, a small team ofsoftware developers gatheredat a Utah ski resort and craftedan entirely new philosophy

and approach to computer programming.Instead of complaining about changes

to requirements, developers would em-brace change as an opportunity for com-petitive advantage. Face-to-face conversa-tions would be the preferred way to shareinformation. Programmers would meet reg-

ularly with the business side of the house.An over emphasis on planning and docu-mentation would end, replaced by an ea-gerness to adapt.

Those were among the key points of theteam’s “Manifesto for Agile Software Develop-ment,” a document that has now been signedby many leading developers and sparked im-proved efficiency and productivity.

The aerospace engineering professionhas reached a crossroads similar to that

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AEROSPACE AMERICA/NOVEMBER 2015 33

faced by those programmers in Utah.Achieving the breakthroughs that our cus-tomers will demand in the coming yearswill require engineers to manage unprece-dented design complexity and wrap in de-velopments across a multitude of disci-plines. We have to update some parts ofsystems engineering and completely over-haul others.

Since systems engineering is aboutmanagement, process and control, as well

as engineering and technology, we have torethink the systems-based organizationalpractices we currently use. Part of the solu-tion will be for thought leaders working inthe aerospace industry to gather regularly,just as software leaders who embrace theAgile mindset do, and discuss techniquesand ideas for addressing the challenges thatarise from system complexity.

AIAA began doing this in 2012 whenmembers of the aerospace community met

Steve Mann

Cutaway view of a jet engine.Aerospace systems engineers maybe ripe for an overhaul in order tospark productivity and creativity.

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34 AEROSPACE AMERICA/NOVEMBER 2015

for the first time for a series of discussionscollectively known as CASE, for the Com-plex Aerospace Systems Exchange. TheCASE meetings are held during AIAA’s reg-ularly scheduled forums and have been at-tended by chief engineers, program manag-ers, academics and systems engineeringprofessionals who have run into this phe-nomenon and want to find out more.

CASE promotes the application of sys-tems engineering as a strategy for dealingwith the growing complexity of modernaerospace systems, including satellites,space probes, airliners or military planes.New systems are fundamentally differentthan older systems with respect to func-tionality and interconnections. Complexitycan add delay and cost to the developmentcycle, and if current trends continue, someprojects won’t be completed at all.

Consider such military planes as theF-4, F-104, F-15, F-16 and F/A-18. It tookfive to seven years to bring each of theseaircraft to initial operational capability af-ter the award of the first prototype con-

tract. Then, in the 1980s, the Air Force be-gan funding work on an even morecomplex aircraft, the Advanced TacticalFighter, now called the F-22. It took 19years to develop the F-22, and at vastlyhigher cost than previous aircraft.

The appearance of unpredictable be-havior — for instance, an unexpected air-flow or electrical effect — is an indicator ofcomplexity in a system. To cope, the de-sign of a complex system must be inher-ently non-deterministic, meaning one hasto appreciate and address unpredicted be-havior as it appears.

History offers clear lessons about this.The F-15 air superiority fighter was built toa historic load and fatigue spectrum, be-cause that is what engineers knew at thetime. Engineers did not adequately considerthat the F-15 would fly at a much higherangle of attack than its predecessors. Anunpredicted vortex shed by the forebodyand inlets impinged on the vertical tails athigh angles of attack. This created a signifi-cant structural load and fatigue issue for the

Flight engineer station of the supersonic Concorde jetliner, which had a three-person cockpit crew.

Concorde Legacy

AEROSPACE AMERICA/NOVEMBER 2015 35

vertical tails. Ultimately, stronger materialswere found to handle the intense loadsfrom this unpredicted behavior. Today, sys-tems engineers know to apply multi-disci-plined analyses to predict these effects.However, the high complexity and non-lin-ear fluid and structural mechanics makedefinitive predictions elusive.

CASE helps engineers prepare for theunpredictable and respond effectively whenit does occur. Specifically, CASE helps themtarget resources at the right questionsduring the entire development process fromconcept definition through manufacturing.Consider the actual story of a pilot whoonce was asked what was important for anew aircraft being designed, and respondedthat it absolutely had to go faster than Mach2. In further questioning, he acknowledgedthat he seldom flies at that condition. Hisgoal was to be sure he would have suffi-cient excess thrust for dogfighting. Asking apilot about how fast the airplane needed togo was the wrong question. The right ques-tion would have been, “What attributesdoes the aircraft need for effective dog-fighting?” Fostering effective communica-tion between stakeholders and designers,where each has his or her own perspective,is part of managing complexity.

And there are other places wherecomplexity influences the quest for a totalsystem design, including technical, func-tional, physical, operational, human or or-ganizational issues, which requires a holis-tic approach. A company must managelarge, diverse, and geographically dis-persed teams and introduce organizationalpractices that embrace complexity. Theidea is to be adaptable both technicallyand organizationally.

The reality of complexityAs systems become increasingly complex,an approach that emphasizes configurationstatus accounting or configuration manage-ment is no longer as effective. These con-ventional processes might be described asthe functional equivalent of a systems engi-neering police force in which the processesguide people rather than people guidingthe processes. When performed this way,systems engineering feels like somethingthat is done to you rather than by you. Farbetter for complex systems is to embed sys-tems engineers at all stages of development

and have them be an organic part of theteam. In this strategy, everyone on the proj-ect is engineering the total system and ispart of the “total systems” engineering team.

For new complex systems, there is ahigh probability that a configuration man-agement process will prove to be inade-quate, resulting in schedule delays andlarge cost overruns. Unpredicted eventsemerge as minor concerns mentioned atthe water cooler and loom larger the lon-ger they remain unaddressed. The exis-tence of an unpredicted condition indicatesthat we, as engineers, do not completelyunderstand the system. We need to en-hance our awareness of seemingly minorconcerns and embrace them rather thanpush them away. To ignore these weak sig-nals is to climb the technical ladder of sys-tem development only to find that whenwe get to the top, the ladder has beenleaning on the wrong building.

The inability of an agency or companyto effectively manage complexity is some-times a result of overconfident or disen-gaged engineers. For instance, a naturaltendency in systems engineering is to takethe stance, “That can’t be a problem, be-cause we don’t have any budget for it.”

This posture emanates from the humancondition that leans toward overconfidence,as described by Nobel Prize-winning psy-chologist Daniel Kahneman in his book,“Thinking, Fast and Slow.” In contrast, thereis a predisposition to disengage because offear or frustration. This dynamic sets up anunending analytics black hole, in which youcan never gather enough data to solve thecomplex problem. Seemingly minor, third-

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The U.S. Air Force’s F-22 Raptortook 19 years to develop inpart due to its complexity.

36 AEROSPACE AMERICA/NOVEMBER 2015

and fourth-order phenomena in a systemcan be combined to create a first-orderproblem because there are so many poten-tial system states that they cannot be quan-tified. And no amount of experimentationcan guarantee a solution to those problems.

To deal effectively with complex sys-tems, it needs to be OK for people to say,“Hey wait a minute! What if we did this in-stead?” As an engineering community, weneed to be able to observe the problemwithin the complexity context, pause theprocess to fix it, and further question thecurrent functional architecture in the com-plex system. The systems process must in-clude acknowledgment that something isnot understood and solve it using complex-ity theory and practice.

Simply put, systems engineering mustencompass complexity forethought and vi-sion. When a disruption in the processappears, an effective total systems engi-neer will say, “Let’s not ignore that obser-vation.” Experts in multiple domains canthen be engaged. This kind of integrated

approach is essential for successful com-plexity management.

For now, CASE will continue to addressend-to-end systems engineering contentwithin the aerospace community at AIAAforum workshops, paper sessions andthrough publications to build the capacityof the organization to deal with complexity.Ultimately, CASE helps us know when weare asking the right questions and address-ing the right problems.

QQQDianne J. DeTurristeaches aerospaceengineering at CalPoly State Universityin San Luis Obispo,California. She is on

the AIAA Steering Committee for CASE. Ste-ven J. D’Urso teaches aerospace systems en-gineering at the University of Illinois/Urba-na-Champaign. He was session chair for theConcept Development of Complex Systemsat CASE 2015.

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