Author: Richard

Making the change – Process Definition in an Imperfect World

A version of this article first appeared in the May 2018 edition of our free newsletter, to subscribe click here

So you have engineered, built and flown your prototype aircraft. It has provided the metrics that you see looking for and the investors are happy. You now have to take all of the lessons learned from the prototype and develop your archetype – the production design. You also have to define the design to production design standards and develop your own in house processes. These processes have to be simple enough to enable you to build and sell at a profit but rigorous enough to ensure adequate quality and you qualify for the all important production certificate.

Most of my work is with the design engineers but as I work with more programs I have ended up getting drawn into the interface between design and manufacturing and then defining manufacturing processes.

This has all been very interesting, but during this expansion of my experience I have noticed a few important things.

  1. I did not realize how few of the engineers in the design groups I work with had ever picked up and read a process specification.
  2. Engineering teams that are good at producing prototype designs need a cultural shift in order to move into developing production designs
  3. Not all company management have no awareness of these issues, or see the impact of not tackling the issues.

There is a prevailing attitude in the prototype engineering group that manufacturing know what they are doing and it does not need to be defined on the face of the drawing. And that to define all of these obvious things on the face of the drawing is in some way insulting to manufacturing. In a practical sense this is true. An experienced machinist or layup technician knows what to do and how to do it to get a generally airworthy result. But they should not be responsible for deciding what is to be done. That is the job of the engineer.

The engineer should also know exactly how much definition is required to guarantee airworthiness and put no more than is required on the face of the drawing. This is maybe the hardest part for the engineer to get right. How much definition is too much definition?

So the drawing should define what is required for airworthiness. The process specification contains the approved manufacturing operations and consumable products that results in a finished part or assembly that is actually airworthy.

The process specifications need to be created by engineering and manufacturing working together – and this has to be done before the production design definition takes place.

At one of our clients this process is being handled ‘organically’ as we create drawings we define the required process on an as needed basis. This is not perfect and there are hiccups along the way. However, the engineers are getting involved in creating the process specifications and get a first hand view of how much thought and work is required – this is all good. How do the different classes and grades of anodizing affect hole diameter and the subsequent fit of a bushing?

In a perfect world we would just stop the entire program and create a complete set of process specifications and an entire quality system and the rest of the company would wait for us to finish. But I don’t think that is going to happen……

Rotorcraft and the cost of innovation

This article first appeared in the May 2018 edition of our free newsletter, to subscribe click here

As part of the white paper I wrote on the aerial urban mobility market I had the chance to review over 60 concepts. Most of which rely on lift rotors, or vectored thrust, for some of their flight envelope. In the white paper I touch on some of the problems with this approach but there are specifics that are useful to examine.

I am not a flight dynamics expert (as the following may confirm) but a few things do appear to be readily apparent.

This is one train of thought:

  1. there is a reliance on multiple lift rotors or vectored thrust for take off and landing
  2. The highest number of lift rotors on any aircraft previously certified for civil use is two
  3. My assessment is more than two lift rotors require some form of software control or stability augmentation
  4. Software in critical aircraft systems is very, very expensive to certify

This is another:

  1. helicopters mitigate an engine failure through auto rotation
  2. If you do not have large rotors that allow this you need an alternative mitigation
  3. The most likely mitigation is a BRS system (ballistic parachute system)
  4. For a BRS system to work you need speed and time
  5. In a hover close to the ground this will not work
  6. A BRS system is heavy anyway, with projected battery capacity this must be a severe detriment to aircraft performance

For electric multi rotor systems the following train of thought then occurs:

  1. what if each rotor is fed by a totally independent shielded bank of batteries, can you argue that total power loss is practically impossible?
  2. Does that mean if you have 8 rotors you need 8 independent charging points?
  3. Does each power system has to be isolated inside an independant faraday cage type protection to mitigate lightning strike?
  4. This is giving me a headache, why don’t I just go buy a Robinson R44 helicopter?
  5. For the amount of money I would have to invest in developing a new vehicle of this type I could buy the Robinson helicopter company…….

So, do I have this all wrong? Will multirotor vehicle concepts prove to be simple to certify and will they dominate the market? As I briefly touch on in the white paper, any aerial urban mobility vehicle that makes it to market has to compete with the only existing aerial urban mobility vehicle – the helicopter. Any successful concept would have to be safer/quieter/cheaper/faster/longer range than a helicopter. How many are?

New Address for our Cayman Technical Office

Friends, partners and clients, We have moved our physical location in the Cayman Islands. Please make sure all physical correspondence is sent to the address below.

Please update your records with the following:

Abbott Aerospace SEZC Ltd, Cayman Enterprise City

The Strathvale House, 90 North Church Street,

George Town, Grand Cayman, Cayman Islands

 

Our regular snail-mail PO box is unchanged:

Abbott Aerospace SEZC Ltd, Cayman Enterprise City

P.O. Box 10315, Grand Cayman, KY1-1003

Cayman Islands

 

We look forward to seeing you soon!

New Analysis Spreadsheets – Combined Tension and Flexure of Beams

We have been working out way through the beam analysis methods of in the NASA-TM-73305. analysis manual. This latest set of spreadsheets is for combined tension and flexure of simple beams and have been authored by my talented daughter who is an engineering student at Ryerson University in Toronto. I have checked than so any remaining mistakes are mine alone.

Enjoy!

 

 

 

 

AA-SM-026-101

AA-SM-026-102

AA-SM-026-103

AA-SM-026-104

AA-SM-026-105

AA-SM-026-106

Correction to Textbook – Threaded Fasteners

Many thanks to Surya Batchu for the following correction to our free textbook.

At the top of Page 91 of the textbook the phrase “The interaction equation for fasteners loaded in the unthreaded shank is:” should read “The interaction equation for fasteners loaded in the thread is:”.

This will be corrected in the much anticipated soon to be released third edition.

Happy stressing!

A Risk Review of Aerial Urban Mobility Vehicle Concepts

We have developed a tool for risk analysis for Aerial Urban Mobility Concepts and have ranked the Top 5 design concepts using this unique risk analysis method.

The spreadsheet tool and white paper are made freely available from our website here.

This is an extract from the white paper:

At the start of any technological or market revolution, there is an evolutionary explosion of ideas and concepts. This can be conceptualized similarly to the Cambrian Explosion of 541 million years ago. Over time the many genetic variations are naturally selected until only the variations that naturally suit their environment or are able to adapt to their environment survive.

This effect can be observed to a lesser or greater extent when any technological breakthrough is developed in a relatively free market.

Phase 1: Many organizations will evolve many different designs which will be tested in the market and regulatory environments. Over time different archetypes made by several manufacturers will survive the natural selection process.

Phase 2: In the long term, these organizations will grow their market share, reduce in number through consolidation and will stabilize as two or more large organizations.

These two phases can be characterized as ‘Conceptual Cull’ and ‘Corporate Consolidation’. This white paper is concerned with the ‘Conceptual Cull’ phase. This paper is not entirely scientific in nature. Where possible empirical assessments are made. These assessments are combined with the informed experience of the author and the reviewers in order to draw rational conclusions.

Technical Feasibility:

This white paper is not intended to be a criticism of any single concept or any single company. This paper is not concerned with technical feasibility and for the purpose of this study, it is assumed that all of the designs reviewed are technically feasible. 

Stratos Wing Test

This article first appeared in the December 2017 edition of our free newsletter, to subscribe click here

 

In December I flew to Redmond Oregon to spend some quality time with the Stratos Aircraft project. Nirav Shukla and I have worked on the production version of the wing for the Stratos 714 jet and the wing test article has been constructed over the last few months.

I can’t give specific figures but we reduced the weight of the wing by several hundred pounds compared to the prototype aircraft wing. This was, in part, relatively easy because there is never enough time in a prototype program to get the structure to the target weight – so there was some low hanging fruit. However, we were happy with the result and the test went very well and we are comfortable with the strength of the structure and Stratos is happy with the weight. All good!

Between the prototype and the production design, we upgraded the FE model of the wing – and the whole aircraft.

In the finite element model of the prototype, we modeled all of the cored composites with single laminate element cards. This creates large offsets relative to the element size:

Laminate elements can become unreliable as the offset approaches the element size, especially so for asymmetric layups.

We changed the finite element mesh to the following configuration:

The core is modeled with solid elements and the laminate elements have a much smaller offset relative to their element size. This means that we could increase the mesh density without compromising the veracity of the solution.

We could also model features such as core chamfers more accurately.

Wing Upper skin showing laminate Element Thicknesses

 

View on the underside of the upper skin showing modeled Core Features

 

Because of the increase in mesh density we have a greater trust in the buckling solution from the finite element model so we could move away from hand buckling checks that we knew to be very conservative to using the finite element solution for buckling.

In using the large assembly and global FE model for buckling we saw buckling results that we knew were likely to be ‘non-real’. These were compression buckling modes that were centered on the node at the bottom of the core chamfer and were very local to that region of the panel.

 

Typical compression buckle at core ramp down

We still made sure that these modes occurred above 150% of limit load. We were happy with a zero margin of safety for these buckling loads as we did not expect to see them on test and we did not see any sign of them on test.

If you have any experience of this behavior from this type of modeling we would love to hear from you to compare notes.

The wing attachment bracket regions were sized using typical hand methods available in our technical library.

Yours truly in front of the wing mounted in the test rig just before the test was done

The test went very well. Dieter Kohler was on hand to conduct the test. It is much better to have an independent expert conduct the test. As it is ‘our wing’ if I were conducting the test we would have stopped at every noise coming out of the wing box. Dieter ran the test up to limit and then from zero to limit and finally ultimate briskly, largely ignoring the few noises that came out of the wing box.

On post-test inspection the integrity of the wing box was not compromised. There were some minor hairline adhesive cracks at a couple of locations. These cracks may have been present before the test – the scrutiny that an assembly is subjected to post-test is much higher than the inspection before the test and the cracks were so small that they may be been missed by the pre-test inspection.

In the end, it should have come as no surprise that the wing passed the test – we are using strain limits that give very high residual strength for the undamaged structure.

After a series of other tests (static loading of the MLG in the wing, testing of the flap on the wing, internal pressure testing) we will be able to play with the wing – induce some damage and find out what the true residual strength of the wing is by testing to destruction. The fun stuff!

Note: the test documented in this article and the planned series of tests are internal company development tests and will not be used for certification of the aircraft.

Thanks to Stratos Aircraft for first of all including us in the development team for their fantastic aircraft and for allowing us to publish this article.

Prototypes and Archetypes

This article first appeared in the November 2017 edition of our free newsletter, to subscribe click here

We have had the good fortune to work on many programs when they are in the early stages of development. This involves working on the prototype design and build. I have touched on this subject in previous articles but it deserves an article all of its own.

Put simply, the sole function of a prototype is risk reduction, or conversely, confidence building.

Both investors and engineers fail to understand the function of a prototype and how that plays out in the implementation and testing of the prototype and how that integrates into the larger development program.

The prototype exists to reduce risk in a number of ways

  • Evaluate a new material
  • Evaluate a new process (manufacturing, inspection, maintenance, etc)
  • Evaluate a new feature or design characteristic

Many types of evaluations are possible and as many as are useful should be done: performance, strength, aesthetic, customer satisfaction, maintainability, inspectability, etc

The results of these evaluations can drive improvements, to the archetype or production design.

The first prototyping mistake:

Fly, Fly Fly!

Many programs feel compelled, often by the investors, to have a visible measure of the value of their investment. This comes in the form of the desire to fly the prototype for an extended period during which it represents little real development value. Hell. You are an aircraft company and you have an aircraft. Whaddaya gonna do?

A prototype only has to function as far as the risk reduction exercise requires and should only be operated until the development risks are understood. Prototypes are rarely designed for extensive flying and every flight of the prototype represents a risk to the program – the prototype has, by definition, unique or new features that are not fully understood. Once the prototype has served its primary purpose it best serves the project as an impressive lawn ornament. i.e. used in a positive way that represents no risk to the program.

The second mistake:

Making production design decisions before the prototype has been fully evaluated.

This is most common amongst startups and is for a very understandable reason

When a project finishes the engineering for the prototype, they have a team of engineers with nothing to do. Most companies start on the production design. This is also driven by the need to keep manufacturing busy.

A lot of startup companies understandably want to build in-house capability during the prototype stage. This includes manufacturing capability.

Once the prototype has been built and is in an evaluation phase the manufacturing workload drops to a fraction of what it was during the prototype build phase.

For a startup company this represents a real problem – do you furlough the manufacturing staff and risk losing the in house capability, tribal knowledge and team synergy that was created during the prototype build? Or do you find a way to keep manufacturing busy in a meaningful way while the prototype aircraft is stepped through the cautious and sometimes painfully slow path to safe flight and eventually the performance evaluations it was built for?

Can the company afford to keep their team together doing ‘busy work’ until they have something meaningful to do?

What often happens is that production design is started early, driven largely by the perceived need to keep the manufacturing team busy.

This approach is not necessarily problematic as long as you make all the right guesses about the prototype performance evaluations and the prototype later goes on to prove you right.

However, even if you make the right guesses about your product the prototype can still reveal critical issues that you did not anticipate that will change your production design.

Should you wait until the very end of the prototype evaluation before starting production design and manufacture?

These questions are faced by every aircraft startup and there is no right answer. However, it may be worth bearing in mind that most aerospace startups fail because they run out of money.

If there is a choice you can make early on in the program that preserves cash, that is a choice you will not regret later.

The Third Prototyping Mistake:

Change for the sake of Change

Once you have a prototype you have a set of prototype tools and a set of engineering that puts you some way along the route towards selling a certified product in the market.

The least change between the prototype and the archetype represents the greatest value possible out of the prototype program.

There is a strong temptation, during the process of changing to the development of the production design, to start over. To take all the lessons learned and start the development of a brand new aircraft is very tempting.

It is better to make the archetype as close as possible to the prototype. Certify the archetype and then further changes can be introduced as supplemental type certificates once you have your type certificate and are making revenue.

If the production design has many significant differences to the prototype it becomes a new design and whether you like it or not, your first production airframe ends up being another prototype.

In the words of somebody wise: “Sales solve everything”. Perfect products never make it to market.

To summarize:

  • Do not fly the prototype for longer than you absolutely need to
  • Wait until you have learned your lessons from the prototype before making decisions on production design
  • Keep the archetype as close as possible to prototype. If you start over, the first production aircraft will be another prototype

It is best to plot the quickest time to market with a ‘compromise’ product that still gives a significant advantage over the competition. Worry about introducing perfection in your STC’s. High value options and upgrades are great ways to generate additional revenue once you have a few hundred aircraft sales under your belt.

Airports and Idiots

This article first appeared in the December 2017 edition of our free newsletter, to subscribe click here

So we flew back from Canada to Cayman after Christmas. I travel a lot; to and from the US, Canada, Europe and the Caribbean. Airports suffer from greater and lesser degrees of design and operational competence in their layout and user experience.

Flying WestJet from Terminal 3 at Toronto airport is an astonishing five-act opera of total idiocy.

There is a complete misuse of space and human effort that creates the most delay and inconvenience for the traveler and results in the worst experience for all involved, including the staff.

There are 4 separate roadblocks that caused queues and delays:

  1.  The check-in machines. It was relatively quiet when we arrived at the airport (about 7:15am) and there were queues to use the automatic check-in machines
  2. The baggage drop. You then have to queue again in order to partake of the privilege of putting your bag on a conveyor and scanning your boarding pass because this is ‘better’
  3.  The queue outside the queuing area outside security – In order to get into the queuing area for security. Clever – I was surprised that they managed to create another queue where I least expected it.
  4.  You then wait inside the queuing area to wait to play your part in the kabuki theater of airport security

As I mentioned already this was a relatively quiet time of day and there were queues at all of the roadblocks. On a busy day, it must be literally insane (or more insane)

I counted the number of staff and I believe that there were at least 10-15 airline staff required to maintain this system (herding the sheep who are doing all the work) and 3 security staff before you get into the security area proper.

It also requires a number of automatic check-in machines and a number of baggage processing machines. A significant capital investment and ongoing maintenance cost (a number of both were out of order).

I drew out the floor plan. It is impressive that they create so many queues for so many people with as many switchbacks and direction changes as possible. If you were to consciously create a system to induce as much spatial disorientation and nausea as possible it would be difficult to do better.

At some point it will be obvious to everyone that the customer experience at commercial airports is specifically designed to be the worst possible, minimizing the effectiveness of the resources available. They are doing a great job.

However, they could take the opposite approach – make the experience as pleasant as possible for the customer. Using the same number of airline staff and have traditional check-in desks that would achieve two significant benefits to the customer.

  1. It would be significantly quicker
  2. It would not be a soul destroying, nausea-inducing, degrading experience

But that would be crazy….

So, hats-off to the team at Toronto Terminal 3. From Zurich to the Caribbean, Heathrow to Los Angeles and Dubai to Denver they have pulled out all the stops to create a singularly terrible, terrible experience that beats the competition hands down. Maximising customer effort and discomfort while minimising the humanity of the overall experience. The worst airport experience I have had in 2017 by a shockingly vast margin.

 

It’s all about the Money – Part 2

This article first appeared in the November 2017 edition of our free newsletter, to subscribe click here

 

In the last few years there has been a proliferation of unique electric vehicles and flying cars. Blue sky thinking and disruptive technology are the order of the day and I can see that there will be a number of disappointed investors ahead.

I talk to some of these projects and one I spoke to a few months ago told me something revealing. One of the principals on the project told me “It is too early in the program to start to talk to ‘aircraft’ people”.

Hmmmm – that might be a good attitude if you were not engaged in an aircraft development program. I have devised a series of assessments to judge what the likely chance of success of one of these ‘blue sky’ projects is.

  1. On the ‘About us’ part of a project’s website does the featured key team members include a CTO, a VP Engineering or a chief engineer? If a project dedicated to air vehicle engineering development does not include an engineer in the top echelons of their project they are likely not to succeed. With the best will in the world visionary leaders, CFOs and marketing experts are likely to go off the rails if left unchecked in an ivory tower at the head of a project.
  2. How many engines/rotors does the aircraft have? No civil aircraft has been certified with more than four engines (to my knowledge). No hovering civil rotorcraft has been certified with more than one lift rotor. In the wild, west of the new part 23 regulatory environment, the FAA will likely exercise more caution – as everybody generally does when faced with greater uncertainty. Trying to certify an exotic aircraft is likely to be made more difficult than it would have been in the old regulatory environment.
  3. Is the aircraft electric or liquid fuel powered? It is worth noting that no electric vehicle has been certified under part 23. I don’t think this is because electric aircraft are inherently less certifiable – there are advantages regarding reliability and maintenance. The drawback is that the energy density of batteries is just not comparable to oil derivatives.

If we do some simple math. We can rate the endurance of a powerplant and fuel system by the energy density of the fuel x the efficiency of the engine.

A gasoline powered piston engine:
The energy density of Kerosene = 42.8MJ/Kg, a good piston engine efficiency = 30% or 0.30.

The Abbott Aerospace power plant success index for a piston engine = 0.30 x 42.8 = 12.84

A gasoline powered turbine engine:
The energy density of Kerosene (as before) = 42.8MJ/Kg, a good turbine engine efficiency = 45% or 0.45.

The Abbott Aerospace power plant success index for a turbine engine = 0.45 x 42.8 = 19.26

A battery powered electric motor:
The energy density of rechargeable lithium metal batteries (in development, about twice the current Tesla battery energy density) = 1.8MJ/Kg, a good electric motor efficiency = 90% or 0.9.

The Abbott Aerospace power plant success index for an electric power system = 0.9 x 1.8 = 1.62

To summarize:

System AAPPSI
(Abbott Aerospace Power Plant Success Index)
Piston engine 12.84
Turbine engine 19.26
Electric motor 1.62

It is worth noting that as you burn liquid fuel the aircraft gets lighter and more efficient, a battery weighs the same whether it is charged or empty. This effect has not been quantified in this mini-study.

When an electric aircraft is certified will there be a market for it considering the endurance of the aircraft is likely to be an order of magnitude less than a traditional alternative?

I love electric power systems – they are safe, very cheap to maintain, quiet and efficient. Even the performance projection for the next generation of batteries still put them an order of magnitude out.

References and Sources
https://en.wikipedia.org/wiki/Energy_density
https://en.wikipedia.org/wiki/Engine_efficiency
https://www.energy.gov/sites/prod/files/2014/04/f15/10097517.pdf

To get back to the original point. One of these 3 points is enough to constitute a high program risk factor. If a single program has all of these characteristics my assessment is that the likelihood of failure is so close to certain that it can be regarded as certain.

…..and by failure, I mean failure to repay the financial investment in the project. It is not a success to get through certification and realize that you are selling every aircraft at a loss and the market is a fraction of what was projected at the start of the program.

Investors are free to make whatever assessments they make and invest in whatever they choose. My concern is that the extent of private equity investments in very high-risk programs is causing a lack of investment in credible programs which have a greater chance of commercial success. The failure of the programs that do receive investment is likely to hurt the credible aerospace startups as the entire sector will get a bad reputation.

Marketing mockups and GCI animations of people getting into exotic looking vehicles in their driveways and being whisked off to futuristic commercial complexes to make important decisions are just figments of someone’s imagination.

You still have to deal with the laws of physics and governmental statute, regulation and policy and they do not care what you or anyone else think the future should look like.

I hope that investors start to rub the pixie dust from their eyes and observe proper due diligence and risk assessment exercises.

I know of many part 23 programs that are credible and low risk but cannot get funded, in part because of the rush to take part in the next ‘revolution’. I only hope the investment community start to take a more rational view of the risks and benefits of the projects they have to choose from.