The Fallacy of Scaling, or Why You Need Highly Knowledgeable Experts

Picture this scenario – an internal or external customer contacts a team, possibly through a Request for Proposal (RFP) or as an exercise. The customer knows that your team makes a certain product, and the customer desires to have a similar product. However, the original product is either too big or too small for the desired application. What generally happens?

A small team of engineers, along with a support team of management, financial, and business experts, convenes to define a solution that meets the customer’s desires. Since a similar product already exists, that product becomes a starting point for engineering, cost, and schedule studies. Usually, the preferred outcome is a product like the existing one but with more – more range, more seats, or more payload capacity. Occasionally the preference is for less – less range, less payload, or more likely, smaller external dimensions. The first course of action the team comes to is to take the current product and scale it to fit the new product’s specifications.

The problem then becomes how to do the scaling in a credible manner. I first realized this phenomenon when I was 6 years old, sitting in the rear seat of a four-passenger Piper Comanche. We had stopped overnight in Little Rock, Arkansas, and were sitting on the ramp with the engine idling when a North American P51D Mustang went by on a taxiway. I stared at the Mustang, my mind boggled by its sheer size. Up until that time, I had seen pictures of the legendary World War II fighter, and even had a model of one. But in my six-year old mind, I had made a basic scaling error – I took what I knew, the size of a four place single engine aircraft, and had scaled down that size for my internal picture of how big a Mustang ought to be, for it only had one seat, not four. And so, looking out the window from my vantage of a four place aircraft, and watching this behemoth roll by, caused a definite case of cognitive dissonance.

I had let one parameter guide my understanding of how big a Mustang is. A more thorough investigation would have uncovered some more pertinent parameters, such as engine horsepower (Mustang: 1490, Comanche: 250, or about 6 times the power), cruise speed (435 mph vs 180), and max gross weight (12,100 pounds vs 2900). Then I might have realized my mistake and understood that the Mustang was 50% longer and twice as tall as the Comanche, even with a similar wingspan.

Therein lies the fallacy of scaling – the scaling parameters must be categorized and prioritized, and for that you need knowledgeable experts. These are people who understand the interactions of different parameters, which ones to deprecate, and the ones that should dominate. And most importantly, what parameters really matter. If you are taking a four place aircraft and turning it into a six-place aircraft, there are lots of changes besides adding two seats. Most likely the fuselage length grows, and this upsets the balance of where the center of lift is for multiple reasons. Not only are you adding aluminum (or additional composites), but cable lengths (both electrical and mechanical) change. The outer mold line of the fuselage necessarily changes, the question becomes whether a “plug” is installed or the whole fuselage changes. These decisions have aerodynamic consequences. Think of the difference between the Beechcraft Debonair straight-tail Bonanza (four seats) and Bonanza 36 series (six seats) vs the Grumman American AA1 (two seats) and AA5 series aircraft (four seats). Both initial aircraft added two seats. The Bonanza took the route of blending the fuselage across the new length whereas the AA1 vs AA5 has a constant-width plug. Consequently, the AA5 has control problems in certain flight regimes, where the slab sides result in aerodynamic blanking of one or more tail surfaces. The Beechcraft solution was undoubtedly more expensive, but the 36 series of Bonanzas has endured in the marketplace whereas the AA series is a footnote.

So, what can you as a mass properties engineer do when faced with this very familiar scenario? We are in an irreplaceable position on any program because mass properties engineers have visibility across the breadth of a program. Use that to your advantage. Put on your systems engineering hat and look at how the various parts of your total system come together and how they interact. This is where mass properties engineers shine. We are among the few who have insight into every aspect of the product from where components are placed to how these components operate. And, because mass properties engineers have this insight, we are able to influence design and design changes, including functional and aesthetic aspects of a proposed design. Unlike most other engineering disciplines, we are not “pigeon-holed” into affecting one of a design’s parameters. We can interplay multiple factors and guide the program’s management towards arriving at a better solution than one by multiple engineers, each looking only at a subset of the available options. This is the true Unique Selling Point of Mass Properties Engineering, one that has immense value to a company employing mass properties engineers and it is one of the major reasons engineers choose to stay in mass properties.

Finally, what is the SAWE’s role in enabling an individual mass properties engineer to perform this powerful position? Look no further than the SAWE’s Mission Statement: The Society of Allied Weight Engineers is an international, professional, nonprofit organization dedicated to the promotion, practice, and innovation of the field of mass properties engineering. The SAWE executes its mission via a variety of initiatives encompassing peer reviewed papers, conferences, industry leading training, mentoring by experienced mass properties engineers, and establishing industry specific Standards and Practices. The SAWE has enabled countless mass properties engineers to better serve their companies through all the above methods of knowledge transfer, in the process creating the next generation of mass properties experts. Tying this all together, the engineers who become tomorrow’s experts will lead the innovations that power tomorrow’s products.

Fatigue Life vs Weight Virtual Forum Coming November 20th

Designing for the lightest weight conflicts with the reality that our products have to be usable over their lifetime.  Flexure, friction, rolling resistance, and impact resistance all need to be considered before a product is released for production.  Combating these forces and movements often requires additional or larger structure to ensure a product’s survival out in “the world”.  How do we, as mass properties engineers, accurately predict structural and dynamic systems weight based on system life requirements?

Answering this question is the subject of the second SAWE Virtual Forum.  The Society of Allied Weight Engineers is holding a one-hour Virtual Forum on Fatigue Life vs Weight on Friday, November 20th at 8 AM PST (11 AM EST, 4PM CEST) to discuss this looming problem. Join us and let the SAWE know your experiences and opinions on how best to account for component life requirements in the weight of structural and dynamic components.

Join Forum Leader Josh Elmore of the Army’s Combat Capabilities Development Command, Aviation and Missile Center, and the SAWE Leadership in this 2020-2021 SAWE Virtual Forum via Zoom (link below) and let your voice be heard.  Be involved in solving a problematic aspect of mass properties engineering that impacts not only our ability to control weight, but our relationships with our management and customers.

Zoom Instructions

To join the meeting, first you must register using the link below.

https://us02web.zoom.us/meeting/register/tZMvf-6pqzwsGdBR46NzUL9fLJQZ5kgcXhA1

After registering, you will receive an email from Bill Boze (SAWE Executive Director) with the subject “Tech Forum – Fatigue Life vs Weight Confirmation”. Save this email, as it has the information required to actually join the meeting. Please note that to join the meeting, you MUST use the Zoom desktop client or mobile app. You will not be able to join using the web client.

Your organization needs competent mass properties engineers

According to a survey conducted by the Society of Allied Weight Engineers in 2018, organizations that design, build and/or operate aeronautical, marine, offshore or land vehicles need to promote the value of mass properties engineers within their organization to ensure vehicles can operate to their intended performance and safety parameters.  Simultaneously, organizations must focus on replacing and transferring the knowledge and experience of mass properties engineers who will be leaving in large numbers in the next 5 to 10 years.

The aforementioned is the leading paragraph to a letter being distributed to the leaders in government and industry to promote the value of mass properties engineering, while also inviting them to learn more about SAWE and how SAWE can address the collective needs of those organizations who need competent mass properties engineers.  The attached letter and accompanying enclosure have been distributed to the leadership of over 200 addressees  worldwide.  We want to increase the reach of this letter by asking you to share it with your fellow mass properties engineers and elevate this letter up your management chain to garner support for increased organizational awareness and involvement.  We also encourage you to utilize this letter to secure financial support for attending the next SAWE International Conference in May in Norfolk, Virginia.

Regards,

Bill Boze

President, Society of Allied Weight Engineers

What does participation at a SAWE conference do for you?

For me, the recent SAWE conferences have given me renewed drive to go back to work and continue to earn my paycheck, but with increased personal investment in my career, my company, and my SAWE Family. Getting to listen to very interesting technical presentations, network with a like-minded group, engage our Exhibitors, and see growth of our profession first hand is an opportunity worth the personal investment of time and finances. You might be surprised by the response of your management when you build a solid business case for why they should invest in their future by promoting your participation in the SAWE. Resources for this exist on our website. Use The Welcome to the SAWE pitch as a baseline, https://www.sawe.org/system/files/Welcome_to_SAWE_Company_0.pdf. Use the 2018 SAWE Industry Survey results at https://www.sawe.org/blog/2018/08/12/sawe-survey-results/. Review tips for justification of attending a conference at https://www.sawe.org/conferences/conferencetips. INSPIRE the future by digesting Rod Van Dyk’s article in the 2018 Fall Journal, https://www.sawe.org/members/journal/fall_2018.

I encourage everyone who reads this to post at least a one liner answering the subject question.

Thanks,

Clint.

Orion Spacecraft Testing Coverage

The Orion spacecraft recently underwent mass properties verification in Houston in preparation for the second Launch Abort System test.  NASA Langley Research Center was intimately involved and LaRC engineers Amanda Cutright and Anjie Emmett were on hand for the operations.

Here is a video clip of Anjie and Amanda explaining the testing:

http://www.dailypress.com/visuals/video/95951602-132.html

Knowing the mass and the CG of the Orion spacecraft is a safety of flight issue.  The AA-2 (Ascent Abort – [test] Two) test flight will test the Launch Abort System during the critical boost phase of the Space Launch System.  The LAS must safely remove the Orion capsule with its crew away from a failing booster if there is a launch mishap. The earlier PA-1 (Pad Abort – [test] One) test performed a similar function, but from a stationary simulated launch pad.  The AA-2 capsule is an actual Orion Command Module, instrumented and mass simulated for this test. The fixture seen in the videos was built to enable multiple weight and CG measurements to be made in multiple orientations and is reusable on subsequent Orion vehicles.

The Houston Chronicle also posted an article on the verification test at:

https://www.houstonchronicle.com/news/nation-world/article/NASA-s-Orion-spacecraft-test-module-passes-13152137.php#photo-16006303

Amanda and Anjie traveled to Johnson Space Center in Houston for the testing.   They are seen in the background of the video above.

The Norfolk, VA area newspaper The Daily Press also ran a story about the testing:

http://www.dailypress.com/news/science/dp-nws-nasa-langley-orion-test-20180215-story.html

Both Amanda Cutright and Anjie Emmet are members of the Hampton Roads Chapter of the SAWE.  Amanda is co-chair of the upcoming 78th International Conference on Mass Properties Engineering in Norfolk, VA  from May 18 – 23, 2019.

 

Robert Zimmerman

SAWE Vice President – Technical Director

SAWE Survey results

Dear Mass Properties Engineering Industry participants,

The SAWE recently conducted an industry survey with the ultimate objective of stimulating increased collaboration between Academia, SAWE Company Members and Corporate Partners, society members, and the SAWE Executive Board toward a common objective of addressing the current risks and opportunities.

Summarized results are available here.

Please use this forum to discuss the results and the direction of our society.

Paper 3699 “The Health of Mass Properties Engineering in Aerospace, Marine, Offshore, Land Vehicles, and Allied Industries – Results of a 2018 Industry Survey” with the detailed results can be downloaded from the SAWE document ordering and downloading database at https://www.sawe.org/papers/3699.

Please take the initiative to proactively participate in our Society of Allied Weight Engineers resulting in the betterment of our World through open collaboration.

Sincerely,

Clint Stephenson
SAWE Executive Vice President
executivevp@sawe.org
8326475599

Success in Weight Control

In 1986 I was seemingly drifting from project to project on a short-term basis when I was asked to report to a program known only as Program B.  I arrived at the locked door on the fifth floor of a building we jokingly referred to as “The Six Story Building”.  After knocking on the door, I was greeted by a secretary who looked at my badge, checked my name against a list, and let me in.  I was shown a desk, where I dropped my briefcase, and then followed the secretary to what proved to be the program manager’s office.

Inside, there were a small group of people standing around.  The secretary left and came back a few minutes later with another person.  This continued for about 15 minutes, then a slight, balding man arrived and shut the door.  He introduced himself as the program manager, whom I will call Doctor E.  Doctor E went around the room asking each of us to state our names and areas of expertise.  Then he explained what we were doing.

The government was looking to launch a satellite that would use an infrared device, cooled by a Dewar jar filled with liquid methane.  We were to design this satellite, incorporating the various instruments and this quite large and heavy Dewar.  And then we were hit with the kicker – the launch vehicle was already designated, and it did not have a large payload capacity.  And the deployment stage would spin for stabilization.

I went back to my desk and began listing what this satellite would need – structure, electronics, tubing, cabling, power, etc., and going over the specs we had been given for the instrumentation and the Dewar.  Then I conceptually created a satellite and came up with a weight estimate that I took to the structures lead.  He called in the thermodynamics engineer to look at what I had come up with just as the power engineer arrived with his concept of how to power the satellite.  The power engineer envisioned a satellite surrounded by solar panels, and I still recall the thermal engineer’s initial reaction, namely “Don’t put me in a box!”  The four of us sat there in structure lead’s office and hashed out a top-level packaging scheme and I ran a quick calculation to see what that would weigh.  Just then Doctor E came in and looked at my figures with dismay.  He shooed us out and closed the door to the structures lead’s office.

The next morning the structures lead came to me and said he ran his own calculations overnight and agreed with what I’d come up with.  We marched into Doctor E’s office and presented a united front.  His reaction was “OK, but we have to keep the weight down to allow for specification creep.”  The three of us looked at each other and the structures lead had this look on his face that said “Duh!”

The next few weeks were hectic, 7 days/week for 10-11 hours a day as we breezed through refining the design, looking to minimize cabling, tubing, and electronics while I also spent a lot of time with component placement to keep the spin axis aligned with the deployment stage’s spin axis.  As time went on, my constantly updated mass properties database converged with my “back of the envelope” calculation to within a few pounds.  This was done by constantly questioning every part and any change the various groups decided belonged on the spacecraft.  With a cohesive group of dedicated engineers who shared a common purpose in winning this proposal, keeping the weight under control was relatively easy.  Finally, as the deadline for delivering the proposal neared, the company held a “Black Hat Review” of our proposal, meant to uncover weaknesses in our design and proposed methodologies.  This was held over a Saturday and Sunday, meaning most of the team finally got some time off while the upper management met with the “Black Hats” and walked through the proposal’s many pages.

Monday morning, as we came in, we heard that there would be an all hands meeting in the conference room.  A few minutes before the appointed time we filed in and were surprised to see the company President sitting up front next to the program manager.  Also present were other senior level executives.  Doctor E started speaking, telling us that the Black Hats, who were sitting in front of us, had never seen a stronger proposal.  There were a couple of nits, but these were truly insignificant items that were easily fixable.  We all started to smile, then the company President rose from his chair and walked to the podium.  He told us that the value of this particular project was small, and in a few months’ time the same government customer would be evaluating another proposal the company was working on.  The Program A proposal was worth more than ten times as much as Program B.  It was the consensus of the Black Hats that we would win the Program B proposal, at which point the government could (he said “possibly would”) award the other proposal to a different company, as we would already have won one.  Therefore, the Black Hats had decided to tell this customer that our company was a “No Bid” on Program B and this winning proposal team was hereby transferred to the Program A proposal.  You could see the disbelief on everyone’s face as we filed out of the room to pack up our belongings and head to the facility where Program A was already underway.

Arriving at the other facility, I went in and found my new supervisor.  I knew that there was already a mass properties engineer assigned to this proposal, which had been in conceptual design and pre-proposal activities for over a year.  I was told that the other engineer would temporarily report to me while the company found a place for him – in other words there was only budget for one mass properties engineer and I was to be it.  I didn’t like the feeling that I was taking someone else’s job away, but I went and found the outgoing engineer who had already heard what was happening.  He turned over his files to me, went through a quick overview of Program A, and left.

I went to my new desk, started going through the reams of paper and the mass properties database, and was shocked at what I found.  The program was seriously overweight.  There was a hard requirement for launch capability and the mass properties database showed our design was over by hundreds of pounds, fully 50% over the launch capability.  Obviously, we weren’t meeting requirements, with the trade-off being a severe shortage in range.  My first stop was with the flight design group to verify range versus payload and compare that to what the database said we were carrying.  Next, I went to my new supervisor and told him what I had found and questioned why he hadn’t told me about this when I had first met him.  Amazingly, he was unaware how severe the situation was, although he knew we were overweight.  I went to Doctor E, who was now the deputy program manager on Program A and explained what I’d found.  He said two words, “Fix it!”

Going back to my supervisor, I asked for a copy of the technical proposal.  He said it wasn’t finished, and I said then get me what we have.  I started going through the proposal subsystem by subsystem, checking what was in the proposal against the mass properties database, and verified that the database was generally accurate.  Moreover, it looked like the known unknowns were accounted for.  That, at least was good news – we weren’t worse off than I thought we were.  Next, I went to each lead, subsystem by subsystem, and introduced myself, explained that we had a severe technical challenge, and that I wanted to verify that what I had in my proposal document was the current design.  There were a few differences, but overall everything checked out.  Then I went to the vehicle architect and spent several hours with him and the systems lead going over what I knew, and with Doctor E’s admonishment behind me, explained that we had to “Fix it!”  Shaving a few pounds here and there was not going to give us a viable technical proposal – this needed a rethinking of what we were trying to achieve.

With the words, “If we remove an item, we achieve a 100% weight reduction of that item,” I shocked the system architect into action.  Together we called a mandatory meeting of all subsystem leads, where I repeated what I’d said and then went on to say that unless we could prove we needed an item, it was off the vehicle.  There was, of course, consternation.  We went single-string on many subsystems.  Structural pieces were pulled, the size of the whole vehicle shrank as space was no longer required for this or that box.  Cabling mass came way down.  We shaved material from component boxes, structural members, skins, insulation, combined functions of multiple electronic boxes into one component – anything to get the weight down.

I was on that proposal for six weeks without taking a day off, although I admit I did work half days on Sundays (five hours versus 10 or 11).  We passed our Black Hat Review.  We turned the proposal in but did not win the contract.  The customer said we were in technical compliance but that other companies had better cost and management proposals.  BUT – we did not lose on technical grounds, which we surely would have if we had been 50% overweight.  I can count that as a “win”.  Losing a proposal is not unusual, it happens a lot, just as a company’s decision to “No Bid” a proposal is not unusual.  These are part of corporate life, and corporate life lives on despite these setbacks.

The lesson learned is that a mass properties engineer is much more than a clerk.  Yes, we have to keep track of the mass properties, but that is only part of the job.  Know what your requirements are.  Keep your management informed.  Interact with your subsystem compatriots.  Don’t let a small problem become a big problem.  Look at the overall picture and determine if what you are doing supports that vision.  And most importantly – you may be the “Weights Person”, however, keeping mass properties under control is everyone’s responsibility, so enlist others in the quest to maintaining a technically sustainable design.

Robert Zimmerman

Call to the SAWE Membership – Academic Committee Needs your Help!

The Academic Committee is gathering all available materials regarding Classes, Presentations and Papers for Students (college-level) and Ideas for Student Projects and Events. The intent is to build a SAWE library of resources pertaining to introductory mass properties and introduction to the SAWE.  It is also the SAWE President’s desire to leverage existing work towards developing a Mass Properties training certification program for academic and newly assigned mass properties engineers.

Initially, these currently available materials will be able to be used by any SAWE member for a SAWE Chapter or local university outreach meeting, or for inspiring ideas for Chapter or local school events. Some of the very interesting and diverse materials we have so far include:

  • Introduction to the SAWE – Whidy Kiskunas
  • SAWE University Outreach Presentation – Casey Regan
  • Why Mass Properties Engineers Matter – Robert Zimmerman
  • The Value of Mass Properties Engineering  Roger Belt
  • Weight & Mass Properties Engineering for Aircraft Design – Whidy Kiskunas & Rod Van Dyk; Based on material originated by Casey Regan
  • The Secret Life of the Center of Gravity  Robert Zimmerman & Kristen Terry
  • Mass Properties Engineering as a Systems Engineering Discipline – Robert Zimmerman
  • Naval Architecture & Marine Engineering; Course NAME 581: Introduction to Ship Design – Andy Schuster

These resources will be available in the SAWE Group Office folder.  If you or your SAWE Chapter have any material you would like to contribute to our library, please contact me (V.P. of Academic Affairs) at Donna.Gerren@Colorado.EDU.  Let’s hope we can provide a wealth of information useful to our membership for SAWE meetings and outreach activities. Thank you very much for your contributions!

Donna Gerren

Technical Input on In Service Weight Control

I thought I would start a thread on a topic of conversation, In Service Weight Control, from recent SAWE events. After a platform is put into operation, configuration changes take place throughout operation.  This must be kept track of for safe and successful operation.

What related experiences can you share?

I’ll start.  I perform Integrated Mass Properties analysis on the International Space Station (ISS).   I gather inputs from the International partners on Visiting Vehicles coming and going.  I gather inputs from our International partners on modules.  I gather inputs from our Configuration team as changes are made, for example moving Orbital Replacement Units (ORUs) from their storage location on ISS to their new location to support continued operation.  I verify the inputs make sense and question everything that doesn’t.

When you put it all together, you have analysis of the ISS at any given point in time needed to operate the ISS as it orbits our Earth every 90 minutes.

Consider sharing your experiences here, at a local chapter meeting, in a presentation / paper, and/or at a conference.

I am hoping this will be a catalyst to increased technical discussion.

Thanks.

Clint.

SAWE survey

Please go to https://www.sawe.org/survey/ and take the time to complete this survey.  SAWE leadership devoted a lot of time and thought to develop it.  We will use the results to improve the professions served by the SAWE as well as improving the benefits of participation in the SAWE.  Please invite your colleagues to take the survey.  We want to hear from as many people as possible interested in helping to develop the industries served by the Society of Allied Weight Engineers.  The results will be used to write a paper that will be presented at the Sheraton DFW in Irving, TX in early May 2018.  Make your plans to attend now.  Get company support and begin your travel plans after a well deserved holiday season.  Happy Holidays and best wishes to your family and friends.

Sincerely.

Clint Stephenson, SAWE Individual Membership Chair.