Author: Richard

ITPS

I was privileged to spend a day at ITPS in London Ontario. Giorgio Clementi and his family are old friends and ITPS is a true family business with his wife Bev and all his sons involved. 

If you get a chance to tour the facility you should.

As well as the wildly diverse fleet of aircraft they have extensively adapted for teaching, ITPS have developed and built an Advanced Aircraft Simulation Centre.

This is a suite of eight simulator stations linked together in an integrated simulation environment allowing groups of pilots to train as a unit in a simulated battlespace or other environment.

This facility is one of few in the world with this capability and all of this has been created and integrated in-house at ITPS. The facility includes a cinema style viewing gallery so the exercise can be viewed, assessed and used as a teaching aid.

Every time I make the drive to London to see ITPS they have added to their impressive repertoire of equipment, capabilities and services.

The Clementi family have created something extraordinary on a little regional airport in the middle of Ontario. It is an international aerospace success story and a center of excellence and innovation.

Boundary Conditions and the Affliction of Intelligent Management

All analysts know that a solution to a problem is only as good and the boundary conditions used to define the problem.

The same principle can be applied to other aspects of product development.

It can also be applied (in a similar sense) to life. If there are no boundaries, rules or limitations the social and societal results at small and large scales are chaotic unless the people involved develop arbitrary rules and boundaries to operate within.

So, any problem that you tackle with no or insufficient boundary conditions will produce results that are either nonsensical or misleading.

So where is all this leading us to?

One of our clients has had a huge boost. They have engaged a dynamic new executive team and have significant funding on the horizon. We are all planning and working towards the production development program launch and part of that activity is to better define the production aircraft.

Definition of the production aircraft relies on a series of ‘trade studies’. These trade studies look at varying one or maybe two aircraft parameters and assess the impact on procurement and operational cost, technical and certification risk and cost and other factors.

This is all good and quite normal.

The devil is always hiding in the details.

Before we got all excited about the trade studies we had a baseline production aircraft defined. This meets the basic market requirement. It may need some tweaking – do we have to increase MTOW to carry more fuel to allow a longer range to hedge against a weight growth problem in development? What effect does this have on the size and OML of the aircraft and how does that impact cruise performance?

Instead of examining specific parameter incremental shifts and the impact on the aircraft product, we have leapt into the brave new world of unfreezing all high level aircraft parameters and looking at literally everything.

You can see where this is going… how can you execute a trade study (a simple analysis) if there is no baseline aircraft (set of boundary conditions) to deviate the parameters of interest against?

This is a problem of EMI (External Management Imposition or Implosion). Every new manager brings in a set of experiences that creates a set of biases and motivations (I refer to this using the shorthand ‘comfort zone’). The overlap of the manager’s existing comfort zone with the requirements and reality of the program at hand depends on the relevance of the manager’s prior experience.

If the manager does not have a large amount of directly relevant experience they will be operating outside of their comfort zone.’ This will usually (but not always) result in two things:

  • A desire to challenge the decisions already made and a reluctance to make a decision based on a reduced ability to properly evaluate the parameters that drive the decision.
  • A desire to move the solution into their comfort zone – where they can make a good evaluation of the solution and make a rational decision but the solution could be the wrong solution, or an inappropriate solution for the program.

I know this to be generally true because I have found myself in the same position and I have behaved like this, and I have witnessed it with many other people in positions of responsibility.

So our client has fallen into several traps at once.

  • They have initiated a set of aircraft level trade studies so invasive that they have left insufficient boundary conditions for most of the trade studies to be completed. They have also ignored the obvious high level reasoning for why decisions have been made to date.
  • They have very competent leadership with experience from different types of aircraft programs so the speed of decision making is tempered with excessive caution. Decision making is slow. To date we have no decisions made.
  • I expect that when decisions are made some of the solutions will be inappropriate for the program as they fall into the gravity well of our new managers comfort zones.

Our client has made decisions that look great on paper. You get the best people – and these are the best people. The managers they have brought in are very impressive individuals with fantastic careers at very high levels in major OEMs. However the things they do very, very well are imperfectly aligned with the needs of the client.

Engineering development is relatively easy compared to development of the team and the team leadership.

So what can a consultant do to tackle all of these boundary condition problems? If it is hard fixing stupid, try fixing the very, very intelligent.

Unfiltered Progressivism

In aerospace engineering there is a natural conservatism forced on us by the laws of physics, the regulatory framework and the market. Interestingly, as much as they may believe differently, the market is almost as conservative as the laws of physics…..

Gender may have progressed from a binary to existing on a spectrum but Force will always equal Mass multiplied by Acceleration (In Newtonian physics anyway) and changes of state (solid to liquid, linear to buckled) will still be fundamentally binary no matter how progressive our politics become. Passing or failing a criteria will never exist on a spectrum.

Improvement can only occur through change.The current progressive mindset appears to be based, in part on a logical fallacy. This can be described something like this.

Everything can be improved, Improvement can only be created by change. Change is inherently good as it brings about improvement.

This approach does work until you get to ‘Change is inherently good’. Change in itself does not care about the outcome. This is why we have analysis,so we can predict the outcome of a change. We have replaced analysis with feelings and wishful thinking.

This is also the fallacy of ‘disruptive thinking’ (https://studyonline.abdn.ac.uk/resources/disruptive-thinking) this is a phrase that has fallen out of vogue of late but a few years ago disruptive thinking was essential to…….something? Getting headlines? Appearing to be dynamic and progressive?

Disruptive is a much better word as it means to break or interrupt something. Because breaking something ‘always’ yields good results – especially when applied to aircraft or society in general.

So we arrive at eVTOL. eVTOL is the progressive mindset applied to aerospace engineering.

  • What if we imagine that batteries were many times more energy dense than they actually are or are likely to be?
  • What if we imagine that the government will let us certify something new and high risk?
  • What if we imagine that insurance costs will be very low?
  • What if we imagine that the cost per ride is a fraction of what it is almost certainly going to be?
  • What if we imagine that everyone has no internal risk monitoring system and will want to ride on these aircraft?
  • What if we imagine that these new types of aircraft will never crash and we can fly them over densely populated urban centers?

You can see the same (ironically) type of blue sky thinking applied to society

  • What if we pretend gender and sex are not binary but are infinitely variable and exist on a spectrum?
  • What if it made children happier to use transsexual drag performers to teach them this ideology in school?
  • What if we abolish national borders and allow uncontrolled immigration?
  • What if we treat personal offense as if it is a violent crime and prosecute the offenders?
  • What if we pretend that people will be happy if we take away the need to strive for anything and provide them with universal basic income?

In a previous, less progressive age, eVTOL programs would be a small number of fringe experimental projects. In that sense they would be interesting and may provide great value but at high risk of failure.

Like the memetic (and political) spread of progressive gender ideology until it now dominates the public information space, the spread of eVTOL projects and the propaganda surrounding them is endemic.

eVTOL, like progressive political ideology, is not without some merit. Electric aircraft should be safer and quieter (whether they are greener depends on how the electricity is generated, transmitted and stored).

However, unquestioning acceptance of any claim, no matter how unlikely or impossible, in both progressive politics and progressive aircraft development, leads to the idea that the value of the project is in the perceived virtue of the claim, not the end result of the policy or project.

In the realm of progressive aircraft projects this virtue value, or indeed virtual value is reflected by the level of investment that each project attracts.

Not all eVOTL projects are the same. The litmus test is to look at the range (should be low, <50miles) and projected production units (should be low, less than 500 per year – and that is pretty darn ‘sporty’).

If anyone is projecting more than these numbers, like most progressive policies, the consequence of reality is likely to significantly misalign with the predictions.

Is the aircraft industry embracing change for the sake of change regardless of the likely outcome? What is the outcome likely to be?

Even with traditional, boring, conservative aircraft development, if hundreds of aircraft OEMs are competing for the same market the outcome is reliably and predictably negative. The introduction of unfiltered progressivism into this scenario only makes the predicted outcome more reliable.

Morals of Convenience

I always think of ethics as ‘morals of convenience’. This is a little unfair. Wikipedia defines ethics as “…involves systematizing, defending, and recommending concepts of right and wrong behavior” which is a better definition. If morals define what is right or wrong ethics are the ways in which we apply morals to the real world.

How far do you have to go to put yourself in the clear with regard to ethics in engineering? This is an issue that I always have trouble managing for myself.

An ethical question came up with regard to climate science. I am not a climate alarmist but there is strong evidence that the earth has warmed. However the climate issue is often represented as a catastrophic issue and this context is used to justify the presentation of data that is not strictly accurate so the mildly skeptical can be persuaded to ‘do the right thing’. You know – the end justifies the means.

Regarding this issue someone asked me the question “Oh crap, so thousands of scientists have been lying to us?”, my spur of the moment response was “It is like eVTOL. If you base thousands of engineers’ income on favorably manipulated battery energy density figures then it will be widely supported as credible. Are all engineers working at eVTOL companies lying to us?”

The comparison is not a bad one. eVTOL is predicated on the idea that if we can reduce or totally eliminate the emissions from aircraft, and use batteries, the systems become cheaper, simpler and more reliable. This will make travel cheaper and help the environment. This is a societal good.

However, there is a fundamental problem with this approach. Current battery energy density is such that aircraft are not commercially viable when you consider IFR reserve requirements and, as I wrote a couple of newsletters ago, the energy necessary to provide an acceptable environment for the passengers and crew.

For now we will ignore the safety aspects of the battery and power management systems which are significant and may further reduce the weight efficiency of these systems.

All conscious engineers on these programs know this is a problem. There are two main ways that the non viability of current batteries are philosophically managed in these programs:

  1. The performance is based on current battery weight efficiency and gives a very low range/speed/endurance but a market for a very low range/speed/endurance aircraft is justified in the business model.
  2. The performance of the vehicle is based on a non certified, non industrialized, or in the worst case non-existent, super weight-efficient battery.
  3. The performance is justified with an absurd weight fraction that reduces the weight of everything else other than the batteries and the payload in order to carry enough batteries at current or close to current energy densities

I won’t name companies or projects that fall into these three categories but you probably know who they are already – and some companies use a combination of these methods to create a surface level viable product and viable business model.

In case (1) the engineer can go ahead and work without ethical compromise. Most engineers do not care about flawed business models as they do not impact the technical aspects of the product which is their primary concern. Flawed business models used to attract large investments are the responsibility of the executive alone (generally)

For cases (2) and (3) some of the engineers know that critical aspects of the aircraft product are based on parameters and inputs that they know to be false or ‘forward looking projections’ at best. Does that make them ethically compromised?

As engineers we have all had moments in our career where you have generated a result out of an analysis that was much better than you thought it would be. As you acquire more experience you know to assume that these results are almost always wrong and you go back and double check your work.

This also occurs as you receive data from other engineers or departments. If it does not pass the sniff test or looks to be in error you take it back to the originator and run through the source material to make sure it is correct.

You have to be the reality filter for the rest of the project. Whether that information is technical or commercial. Whether management likes it or not, it is what they pay you to do. If you do your job properly you will find that management does not like it.

Your job is to be right, not to be popular. If your employer demands that you compromise your ethics to be part of the team then you are on the wrong team.

My Scratch Drawing Checklist

Metal part drawing checklist – this list is not comprehensive. Any and all errors will not be tolerated whether they are on this list or not.

Title Block

  • Is the drawing title correctly formulated? (Typically major to minor i.e., AILERON SYSTEM, BELLCRANK, OUTBOARD, LH)
  • Is the drawing number correctly formulated?
  • Is the material correctly specified?
  • Is the stock size correct? (Did you check with procurement?)
  • Is a heat treat required?
  • Is the corrosion protection correctly specified?
  • Have you checked all the interfacing components and hardware to make sure that the corrosion protection is correct?
  • Are there any other coating/priming/painting processes that should be applied at the part level?
  • Has the grain direction been defined?

Views

  • Have you included enough projected views, sections and details to fully and correctly define the part?
  • Have I included views that are not needed or do not add clarity?
  • Is every key feature dimensioned correctly”
  • Have I used the correct number of decimal places so the appropriate level of tolerance is defined?
  • Have I specified custom tolerances where required?
  • Have I used custom tolerances where they are not required?
  • If I have included a reference dimension (in brackets) why is it needed? – the CAD can always be used for reference
  • Is the location of the part number rational? You may have to check the upper assemblies to ensure it remains visible at installation.

Datums

  • Do they make sense for manufacture?
  • Do they make sense for the quality inspection?
  • Have you used datums that are accessible and can be used for measurement?

Drawing Notes

  • Is the general note for using the E-Model included
  • Are notes included that define all the critical aspects of the part
  • Are there any special inspections or quality checks required? Do not assume that manufacturing or quality know anything about the part.
  • Are there any special storage requirements between part manufacture and installation in the aircraft?
  • Is there anything else we should be communicating?

Revision table

  • Is the description of the change sufficient?
  • Is the date correct
  • Is the effectivity included and correct?

Other

  • Have I included a second sheet to the drawing when there was room for everything on the first sheet?
  • Have I added a second sheet because it is required to maintain clarity?
  • Do arrow, pointers, dimension lines pass through each other?
  • Do arrow, pointers, dimension lines pass through any text?
  • Does an element of the drawing come very close to or pass over the drawing border frame?
  • Have I done my job?
  • Will Manufacturing be laughing at me behind my back because my name is on this drawing?

Uniqopter – An Honest eVTOL Program

Towards the end of 2021 I connected with Eugene Pik on Linkedin. Eugene is an interesting guy – raised in Soviet Belarus, moved to Israel and has been running his business in Canada for many years.

He wanted to produce a eVTOL aircraft that would serve the medical evacuation (medevac) market better than the helicopters that are currently being used.

We had some long discussions and we made a few decisions. We would seek to make the project and the corporation fully open source. This decision is where the articles on open source have come from and this has proved to be very interesting.

In the name of open source we would be honest about all aspects of the program. We would make no optimistic projections, we would seek to exploit no markets that do not currently exist, we would not plan to set up our own operations company to place orders for the product.

We would set up the commercial aspect of the program like any other traditional aircraft program and see if it could work.

So we started as all aircraft programs should. We talked to the customers and users. Eugene lined up conversations with many medevac operators in Canada and the US and we listened to everything they had to say.

We learned that the Canadian and US business and operating models are quite different. The US market is served by operator subcontractors where the operating cost is a very significant part of their operation. The Canadian operations are vertically integrated where the flight operations are just part of a larger organization and the vehicle operating costs are not driving the choice of vehicles.

We learned that noise is a big issue as operators flying into city hospitals get multiple noise complaints for every flight they make and they need to carry the pilot (sometimes 2 pilots), two medics and two patients (in some states).

In the US the flight durations are low and operators in both countries have problems getting into some landing areas because of the space needed for the main and tail rotors and the hazards they represent to potential bystanders.

We also learned that helicopter floors are not designed to be fluid proof and there are significant problems with cleaning and sterilizing the helicopter and the underfloor areas.

The vehicle would need to be capable of IFR operations and would need large double doors at the rear to allow easy loading and unloading of patients, and especially larger patients.

In a relatively short time we had a good picture of the market requirements and set about configuring the vehicle.

The Vehicle

Batteries
If you have read this newsletter before you know the physics based approach I use for battery based feasibility studies so we discounted batteries after the first high level assessment. There is no battery powered hovering vehicle that can meet IFR reserve requirements and have any useful load or range left over – if you consider the currently available energy densities.

Hybrid
If you want to use electric motors to avoid direct (or indirect) drive from a piston or turbine motor then you have to use either hydrogen fuel cell or on board electrical generation based on hydrocarbon fuel.

As I have noted before Hydrogen has great energy density and lousy density – unless you keep it close to zero Kelvin. As well as the impracticality of onboard hydrogen storage there is also no production and delivery infrastructure for hydrogen and there is no type certification path for hydrogen fuel cell systems.

With all of this in mind, and keeping ourselves based in reality you end up with a turbine generation system. There are certified turbo generation systems (these are called APUs) but these systems are not very high efficiency but they do exist. We would have to plan to develop our own or partner with a supplier to develop a system. However it would be physically possible to create a generator and there is a preliminary path through the certification process for a turbo generator.

This is a view of a preliminary loft of the aircraft with turbine engine, generation and buffer/emergency power battery packs

How is it going to fly?
Well – wings and conventional landing are out of the question so it would have to be a rotorcraft of some type. It would have to have a smaller overall footprint than a traditional helicopter. Smaller rotors mean lower disk area and reduced hovering efficiency. Hybrids already have an efficiency loss compared to direct drive systems so we need to have the rotor disk area as large as possible.

In the end we settled on two pairs of stacked counter rotating rotors. These would have to be relatively closely coupled. This would allow us to create an effective larger rotor area for the same footprint and help drive up efficiency.

In addition, if we house these twin rotors inside a ring we may get some duct efficiency, it would help protect people from the hazard of the rotors and help mitigate noise problems.

If we selected a twin turbo generator system we could split the power from the two turbo generators so one generator drives one rotor in each of the pairs. This way if we suffered an engine loss we could still retain control as a single fan in each of the two sets would remain operable for safe flight and landing.

Flight Controls
Pitch control (or for/aft control) will be achieved through a direct mechanical connection to the rotors themselves:

Other axis controls will be achieved through the use for reaction control valves similar to the RN Sea Harrier or Harrier AV8B:

A nice side effect of using turbine engines is that you have bleed air that you can tap into to drive the reaction control thrusters and also to heat the cabin. Cabin heating is a problem that battery control and fuel cell powered aircraft have yet to address.

Software control will be avoided in favor of direct mechanical connection to the reaction control valves. This has yet to be detailed and we may find that some software management of the flight control system is unavoidable

The Fuselage
In this layout of the interiors much credit must be given to Ferno. They went above and beyond being a mere potential supplier and helped us lay out the interior for multiple configurations. They made sure we gave enough space to carry the medics, the patients and the equipment and allow the medics to work around the patients in flight.

We also have to acknowledge the help of Norman Wijker in lofting the fuselage and the fairings above the cabin. Norman went above and beyond in producing a body and fairing shape that met our needs and then some.

The Final Preliminary Configuration
Having identified a market segment, we talked to the customers, defined a specification, reviewed the available technology and the competition and sketched out a preliminary configuration:

90 minute flight mission with 30 minute reserve for 1 or 2 pilots, two medics, and 1 or 2 patients

  • Flight time: 90 minutes + 30 min reserve
  • Speed: 125 knots (232 Km/h, 144 Mph)
  • Useful weight (payload): 1530 lb
  • Weight of the medical equipment: 500 lb
  • Total weight: 7000 lb
  • Number of medics: 2
  • Number of pilots: 1 or 2
  • Number of patients: 1 or 2, up to 400 lb total

The resulting vehicle would be a part 27 twin engined turbine powered rotorcraft specifically designed to meet the mission based requirement in a medevac role.

There are some technical risks that we need to address:
Certified turbo generation system, close twinned counter rotating rotors, flight control system avoiding software, power plant failure modes.

However, there are not many risks that thoroughly violate established physical laws – that puts us in pretty good shape for an eVTOL program.

The Business
The essence of the business case is that you have to be able to generate enough revenue and profit to justify the investment and the timeline to revenue and profit.

Aircraft programs required a lot of money and a lot of time to get to profit.

Profit is a function of the economy of scale you are working at. The fewer vehicles you produce the greater the cost per unit you produce and lower the profit. If you can’t produce and sell enough units you cannot get the cost down low enough to make a profit and you operate at a loss (or ‘negative profit’ for the diplomatically minded).

If you start a company and you only have one product you need to sell enough of the profit to support all of your company facilities and systems.

If you examine the helicopter industry no successful company just produces one model of helicopter. I.e. they create leverage from their company facilities and systems to generate acceptable economies of scale because the sales from a single class of helicopter is not sufficient to create acceptable economies of scale.

In short: You need to sell a bunch of vehicles or you’re gonna get in trouble.

How many vehicles can you really expect to sell? Eugene investigated the business case and the first port of call is the GAMA production numbers. This is a sobering read.

In a good year the global sales in this segment reaches 500 units:

The number sold is more realistically in the 300-400 unit range. – so let’s use 350 units per year as the global market for new vehicles.

If we achieve 10% global market penetration (35 units a year) would we be profitable? From my experience and preliminary numbers the answer is ‘barely’. So realistically the answer is that we would have to achieve at least 10% market penetration just to break even.

We will be competing with Bell, Airbus and Leonardo (Agustawestland). Would they be able to aggressively price their products and rely on their MRO revenue to sustain them in order to get the orders we would need to survive. Answer: Yes.

Would we survive? – a barely profitable company with minimal to no MRO revenue having to discount our products just to get into the market. Answer – Almost certainly No.

So Eugene (along with Taras Lyssenko – long time associate and trusted voice of reason) decided to post the project as an on line ‘white paper’ on commercial viability

The Hype
So how do you make the business case for a startup company developing a single vertical take off air vehicle?

  • You need to create a business case with compelling revenue and profit.
  • This means you have to produce more aircraft in your class that are currently sold globally
  • In turn you need to present a market that does not currently exist that supports the sale of thousands of new aircraft every year.
  • That market is based on a price point that can only be justified by the low cost of the vehicle based on the size of the market which is based on a price point that can only be justified by the low cost of the vehicle based on the……..

You end up in the circular logic of the chicken and egg where neither the chicken or the egg have yet to be shown to exist.

eVTOL – Making or Repeating History?

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OK – upfront, the data for the Wright Flier I am using is taken from the Wright Flier Model B wikipedia page (https://en.wikipedia.org/wiki/Wright_Model_B).This was the last iteration of the original Wright Flier configuration and was sold in 1910. Their famous first flight was in 1903 so this places seven years between the initial flight of the prototype (the first powered flight in human history) and the Model B.

To put this in context Joby aviation was started in 2009 (thirteen years ago)and started flying full scale unmanned prototypes in 2017 (five years ago).

The timelines are a little different but more than fair as Joby has the accumulated knowledge of the previous century of the global aeronautic global history of technical development and computing power trillions of times greater than a slide rule.

So this comparison is horribly unfair in favor of Joby, and other eVTOL developers. It is also worth pointing out that the Wright brothers were incredibly inventive and the way that they developed their original aircraft and proceeded towards their first flight was nothing short of astonishing.

So we will use three standard performance comparisons, these are maximum range, useful load and cruise speed. 

Maximum Range Comparison
To be fair it is clear that the Wright brothers were not subject to VFR/IFR reserves. Considering the numbers published by the eVTOL manufacturers and knowing battery energy density I am confident many eVTOL manufacturers are also ignoring regulatory reserve requirements…..so they are representing each manufacturer at their word.

Useful Load
Useful load is not the ‘payload’, but for eVTOL as the mass of the ‘fuel’ cannot be varied so the useful load is effectively the same as the payload – unless you can vary the amount of batteries carried to modify the amount of payload you can carry. This is one of the fundamental limitations of eVTOL – the payload is fixed at a single value and the range can only be varied according to the mass of the payload and not the additional fuel you can carry as the payload reduces.

Speed
This is one area where modern vehicles can excel compared to the first powered aircraft configuration ever flown. Both in terms of induced drag and parasitic drag.

Conclusion
In terms of range and useful load the Wright Flier does pretty well; surprisingly well considering the over 100 years between the products being compared. The level of technology employed in current products and the analytical methods and design tool available to us today.

To make a better comparison I have included the Diamond DA40 (https://en.wikipedia.org/wiki/Diamond_DA40_Diamond_Star) and the Robinson R44 (https://en.wikipedia.org/wiki/Robinson_R44) in the graphs.

Not surprisingly the energy density of liquid hydrocarbon and modern aerodynamics make a huge difference

What this does throw into sharp relief is how the adoption of batteries are driving aircraft performance backwards for range and useful load despite the advances in aircraft and propeller aerodynamics over the last 100 years.

The question remains – is there is a market for these aircraft with positively regressive performance Is the perception of virtue of relocating your pollution to a power generating plant some distance away worth the loss in performance?
If you could cut your iPhone data plan to ¼ for current data transfer speed if it appeared to help save the planet would you do that?

I didn’t think so.

Electric Aviation and the Problem of the Cold Cabin

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All the numbers used in this article are Rough Order of Magnitude (ROM) numbers. Nothing nuanced here – just back of the napkin numbers. If you disagree with my assessment let me know, send me your numbers and I will publish you in the next newsletter.

On one of our programs this week we have got into the subject of cabin heating. This is a relatively high altitude cabin and the heating requirement is going to be more than your run of the mill eVTOL aircraft.

But I am sure that eVTOL UAM operators will want to run their service in Toronto or Stavanger in the middle of winter so this will still be a problem at some level.

For electrical conversion of regular fixed wing aircraft this is a more significant problem.

Turbo propeller and turbo fan engines generate the two things that are lacking for humans at altitude. Pressure and heat. Turbine engines allow you to tap into the hot air under pressure from the turbine to provide both heat and air pressure for the cabin.

The addition of turbochargers allows you to ‘harvest’ heat and pressure from piston engines. This heat and pressure is not only useful for providing a comfortable cabin environment but can also be used for intake lip and flying surface anti-ice systems.

It is important to note that these systems, called bleed air systems, do not convert the waste energy from the engine. They tap into the energy of the motive system and further reduce engine efficiency. 

Waste heat from engines is very hard to recover, as is any inefficiency as it is entropic by nature. Reconcentrating that entropic waste is difficult, heavy, expensive or impossible.

Electrical motive systems have inefficiencies and those inefficiencies are represented as waste heat. When batteries release energy they generate heat. The motor controllers and motors are not 100% efficient and that inefficiency is represented as heat. All in all between the battery and the rotating shaft of the motor you can expect to lose 10-15% of the overall energy.

If you are cruising at 350HP or around 200kw that can mean you are also generating up to 0.15 x 200 = 30kw of heat throughout the system. This is also true of UAVs. In recent talk with university students at Tuskegee University we touched on the subject that if each motor is, say, 93% efficient and pulling 1kw you have a 70W heater at each motor. These issues need to be managed and this heat, like all waste heat, has to be dissipated through vanes, circulating air systems, radiators etc.

In order to pressurize and heat the cabin at 41,000ft (high altitude cruise for a pressurized aircraft) for 8 occupants you generally need 10-12kw.

Well, if you have 30kw of waste energy that is more than enough, right? 

Well, no. That energy is in the form of entropic waste heat. If you could gather most of it and cool it using a heat exchanger you may be able to recover some of the heat for use in the cabin but it would necessitate the use of a large, over complex heat exchanging system, would not recover enough energy and would still fail to pressurize the cabin.

So you have to pull that 12kw out of the batteries. If you need 12kw of heat and pressure and your heater and your compressor are, lets say 70% efficient then you need 12 / 0.7 = 17.14kw  – let’s say 17kw from the battery.

For one hour of flight at 41,000ft the battery energy requirement to maintain the cabin environment is therefore 17 kwh.

Using the packaged battery energy density of 150wh/kg this means you need to carry around 250lb of batteries to provide the necessary cabin environment for one hour.

For eight passengers this would be 30lb of batteries per passenger per hour to cruise at 41,000ft.

On the Explorer AIrcraft program we had a series of conversations with some of the world’s leading researchers in the field of fuel cells at one of the US National Laboratories. I raised the issue of the lack of harvestable excess energy in the form of heat and pressure being a barrier to the adoption of fuel cell and battery technology in aviation and it was not something that had been examined or considered.

So not only will electric aircraft have to rely on extracting additional power from the already weight inefficient batteries, they will also have to carry the excess weight of an electric compressor and heating system for the cabin air.

While lower performance and lower altitude aircraft do not have to provide pressure to the cabin they do have to provide heat. For those operators who want to offer electric UAM in the middle of winter the heating requirement overall is roughly half of the overall bleed air energy mix. So around 5-6kw.

So the battery mass requirement for unpressurized flight will be roughly half of the number calculated above – that is 15lb of batteries per passenger per flight hour.

The Joby S4 with one pilot and 4 passengers will require 75lb of batteries per flight hour for cabin heating in cold conditions.

This amount of additional battery weight would not be a problem if you were not already fighting the unfavorable physics of battery energy density in all other aspects of design and operation.

Is this article just dumping on electric aviation from a negative point of view? Well, yes it is. Batteries have their useful applications in aviation. Powering commuter style passenger aircraft is definitely not one of them.

Sometimes lousy energy density and immature technology is just lousy energy density and immature technology.

Eulogy for an Astronaut

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This month I attended the celebration of life for astronaut and test pilot Bjarni Tryggvason. He was the test pilot for the Otto Aviation flight test program and was instrumental in getting the 500L prototype aircraft into the air and providing feedback and guidance for improving the aircraft for production. He will be missed personally and professionally by many people.

The occasion was very well attended by hundreds of people and included several flypasts. The master of ceremonies closed with this reading. This is written by Aaron Freeman and was first published by NPR in 2005 (https://www.npr.org/templates/story/story.php?storyId=4675953)

I had not heard this before and I thought it was very fitting:

You want a physicist to speak at your funeral. You want the physicist to talk to your grieving family about the conservation of energy, so they will understand that your energy has not died. You want the physicist to remind your sobbing mother about the first law of thermodynamics; that no energy gets created in the universe, and none is destroyed. You want your mother to know that all your energy, every vibration, every Btu of heat, every wave of every particle that was her beloved child remains with her in this world. You want the physicist to tell your weeping father that amid energies of the cosmos, you gave as good as you got.

And at one point you’d hope that the physicist would step down from the pulpit and walk to your brokenhearted spouse there in the pew and tell him that all the photons that ever bounced off your face, all the particles whose paths were interrupted by your smile, by the touch of your hair, hundreds of trillions of particles, have raced off like children, their ways forever changed by you. And as your widow rocks in the arms of a loving family, may the physicist let her know that all the photons that bounced from you were gathered in the particle detectors that are her eyes, that those photons created within her constellations of electromagnetically charged neurons whose energy will go on forever.

And the physicist will remind the congregation of how much of all our energy is given off as heat. There may be a few fanning themselves with their programs as he says it. And he will tell them that the warmth that flowed through you in life is still here, still part of all that we are, even as we who mourn continue the heat of our own lives.

And you’ll want the physicist to explain to those who loved you that they need not have faith; indeed, they should not have faith. Let them know that they can measure, that scientists have measured precisely the conservation of energy and found it accurate, verifiable and consistent across space and time. You can hope your family will examine the evidence and satisfy themselves that the science is sound and that they’ll be comforted to know your energy’s still around. According to the law of the conservation of energy, not a bit of you is gone; you’re just less orderly. Amen.

-Aaron Freeman.

The Responsibility of an Engineer

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My daughter is shortly to graduate from Ryerson University and recently took part in the ritual of ‘The calling of the Engineer’

She told us about it and my first reaction was that it was all rather silly. However, being an engineer I had to look into it, carry out a root cause analysis if you will.

It was all rather fascinating.

The worlds of the ritual were written by Rudyard Kipling at the request of the Canadian professor H. E. T. Haultain. The ritual was deemed necessary because of the Quebec bridge disaster in which seventy four people died because of incorrect engineering analysis.

The complete wording of the ritual is not publicly available but a part of the ritual is reciting a Poem by Rudyard Kipling called the “Hymn of Breaking Strain”, this is the first verse (to give you a flavor):

THE careful text-books measure
(Let all who build beware!)
The load, the shock, the pressure
Material can bear.
So, when the buckled girder
Lets down the grinding span,
‘The blame of loss, or murder,
Is laid upon the man.
Not on the Stuff—the Man!

While the language may be archaic, we now have many women engineers including my mother and my daughter, the sentiment remains sound. An engineer carries responsibility for the work. You cannot blame the thing that broke, you have to blame the engineer. It does not matter why it broke, the engineer is responsible for and mitigating all possible risks. These include materials (where do your materials and allowable values come from?), geometry (Too thin? Too slender? Too few fasteners?), manufacturing (read and understand those process specifications and understand the quality system), installation (process specs again, corrosion protection, clamp up forces, etc) , service (load and environmental conditions), repair (approved repairs, field repair materials and processes, etc.). If any of these are incorrect or inappropriate the engineer is to blame.

Many engineers see their discipline as an abstract theoretical exercise and spend all their time working on, for example, finite element analysis. This is common if you work in a large technical office and it is how I spent the first few years of my career. However, the level of responsibility of each engineer is not changed by their working environment.

Rituals are an important way of imprinting ideas and memorizing them.

So having spent some time looking into it from the position of an old(ish) and cynical engineer I have concluded that the ceremony has value. Those values do have to be reinforced on a regular basis though.

Modernity seems to take a dim view of rituals, but I think we do need them and we institute them in our lives when they are not imposed externally.

Good for the Canadian engineers and their seven wardens.