Newsletter – December 2022

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December 2022 - Best Wishes for 2023

Generally speaking, we can assert that 2022 was the most challenging year for our company since its foundation. We have faced many issues, but after all we have been able to carry out our project. We have welcomed lots of new members in our team and we said goodbye to others, but we still feel the same sense of belonging to our company, that's all that matters. 

Concerning the work carried out in 2022, we are proud to say that we have accomplished a lot of achievements in manufacturing the first Swiss fully electric aircraft, UR-1:

  • The completion of the V-Tail with the control surface integrated,
  • The assembly of the canopy,
  • The completion of the fuselage molds.

In this regard, November was a key month for the company under many points of view. The big piece of news is that we have finally received the electric batteries that will be equipped on the first Swiss all-electric race plane, UR-1. Our team is currently working on arranging them in boxes made for this precise purpose. Then, we will be ready to install them inside the wing. In addition, the team is still committed to testing the fuselage molds and the wing flaps.

We are also pleased to announce that we have a new technical supporter: the renowned company Brütsch/Rüegger Tools, which offered us many important tools for our workshop. We are truly grateful for having the opportunity to count on this support.

In any case, 2022 was a key year also because it gave us the opportunity to plan our future more precisely. Indeed, we made some choices that will influence our history as a company: we have designed our next prototype, a civil aviation aircraft, the UG-2, with high performance and low operational costs. And this is just one of the projects we have in the pipeline for the next years.

So, after such a challenging year, we need to take a break (we will be back in January).
Before saying goodbye, we would like to thank you for the support you never forgot to show and for following us in our journey. To show our gratitude, at the end of this newsletter's number, you will find a funny gift... 
We hope that our and your 2023 will be healthy, full of success and bright. Let's see what Santa is planning to give us way for the new year. 


  • Completion of the molds of the fuselage
  • Electric batteries close to be installed in their own boxes

Communication and Marketing

Short Outlook

During the next weeks, Pie Aeronefs team plans to be involved in the installation of the electric batteries in their own boxes.
Another crucial step will be represented by the end of the tests on the fuselage and on the flaps.

Seen on the press

Nov 28th | MSM - Le mensuel de l’industrie: Link

"Les entreprises aéronautiques romandes se regroupent" | MSM - Le mensuel de l’industrie

New articles

Dec. 7th - International Civil Aviation Day: electric aviation state of play Link

New vacancy on "Jobs at Pie" webpage: 

Stress Engineer (Full time) Link

Team News

Welcome to Ronald Jonker, our composite technician

Welcome to Daniel Salama, our administrative manager

Welcome to Alejandro Rivera, our junior composite technician

Welcome to Frédéric Stebler, our composite technician

Welcome to Ambroise Meyer de Shadelhofen, our junior composite technician

Welcome to Majid Ammam, our account manager

We need you !

Moving to the future requires a strong team work. We, at Pie Aeronefs SA, are looking for partners and sponsors who want to join forces towards the fastest Swiss all-electric aircraft.

Have a look to our registration page and we will be glad to hear from you.

Special Christmas GIFT (or as we call it: "a gem for nerd")

We are pleased to share with you the presentation our CEO and CTO, Marc Umbricht, created for MY CAD 2022 conference. If you are wondering why we have decided to offer you this "pearl", it is just because he has involved Santa Claus in a special mission and, of course, because it is funny.
So, enjoy it! 


At Pie Aeronefs, we try to use a first-principles, mission based approach to aircraft design. This is in contrast to the traditional method of aircraft development, which is largely iterative and empirical, i.e. to take an existing airframe and make small improvements to extend its capability.

We are a small team in La Sarraz, relatively vertically integrated for aircraft R&D. We have a composites workshop and are set up to bring a prototype from conception to first flight. Our goal is to create the first truly market viable electric aircraft, which does not compromise on performance.

Traditional aircraft conceptional design relies heavily on statistical models to estimate system sizes and weights. To say that it is not mission focused would be incorrect, but there are serious limitations to the conclusions which can be drawn. It is difficult to explore new design spaces based on extrapolations from existing data, limiting the innovations that can be made.

This presents us with a dilemma. Statistical models have the advantage of being relatively accurate, but do not telegraph their limitations. For example, it was extremely difficult for post-war fighter designers to breach the sound barrier, as the supersonic regime is fundamentally different from the subsonic environment of WW2 fighters. It was therefore difficult to extrapolate into this new regime. On the other hand, analytical models are very easy to understand and extrapolate to the limits of their applicability, as many of the model assumptions are obvious, and thus are obviously true or false depending on the application. They do have a bad habit of being over-optimistic, however. When estimating the weight of a structural element, a model of the necessary cross-section is unlikely to capture glue joints, bolts, interfaces, and other critical details which are not visible at the conceptual design stage.

Fundamentally, statistical models lead to similar designs, because without a reliable way to estimate the limit of applicability, the designer is forced to be overly conservative, or else run the risk of generating unrealistic designs.


When taking the time to be truly innovative, however, real breakthroughs can be made. This is the Rutan boomerang, which had the simple design goal of resolving the issue of engine-out yaw balancing. Piston engines turn one way, and this creates an asymmetry in the thrust produced. For a "right-handed" engine, the propeller will generate thrust slightly to the right of the shaft axis. This creates a problem in multi-engine propellers, where an engine failure on one side will be worse than the other. Some aircraft use so-called counter-rotating propellers, although it is expensive to create a small number of "left-handed" engines. Burt Rutan's solution was to position the engines asymmetrically, such that there was more drag on the right, and more thrust on the left, evening out to a relatively balanced aircraft, no matter which engine was operating. As a result, the Rutan Boomerang is one of the safest multi-engine aircraft ever made, even if it had no commercial success.

So, how does one go about first-principle design? The first task is to rigorously define and understand the mission. This is the canvas on which you can develop your aircraft. Next, the top-line directive is to be creative. It's important, however, to exercise restraint, as any good idea you have will have to actually be realized by your design team. As a rule, the difficulty of including innovations scales exponentially with the number of visits from the good idea fairy.

I have prepared a topical example.
Santa has to deliver all the gifts to the good little christian boys and girls. While this may seem exclusionary, it is an important limitation to the scope of the mission, as we can largely exclude non-christian parts of the globe, along with much of the population.
In essence, we have to deliver a large number of packages, over 24 hours, and we only have a single qualified operator, as Santa does not like to delegate.

We define these mission parameters and assumptions. Critically, we assume that we can do multiple trips, and we decide to do a single continent at a time. Additionally, because of a little bit of Christmas magic, we will neglect heat dissipation in this exercise. And finally, all children have been good this year.

Let us assume that South America is the limiting mission case. It is in the southern hemisphere, and has a large christian population. We then construct this model, based on a normal distribution of targets (boys and girls), and an average gift mass of 250 grams. This results in a total range requirement of 40'700 km, 20 million kg of payload, and a minimum cruising speed of mach 4.1.

We thus see that the venerable SR71 blackbird is too slow for Santa. We can do 3 turnarounds in 24 hours, for North America, South America, and Europe.

From these requirements, we can sketch out some general mission architectures. Here we can propose three architectures: a VTOL arrangement with high-speed cruise capability, an intercontinental Christmas missile, and a high-velocity, constant speed gift bomber.

We then evaluate them on a number of evaluation criteria. The VTOL and ICCM have major advantages, but each have disqualifying drawbacks. For example, it is physically quite difficult to create a vehicle that is capable of both supersonic and hovering flight.


So we are left with a fixed wing configuration. We then proceed to fuel estimation. This is the Breguet range equation (or rather the solution to it) which calculates the fuel requirements for aircraft. Using specific fuel consumption figures from the Concorde and Rolls Royce Olympus 593 engine, we see that we can only achieve a range of 17'400 km if we were to have half of the aircraft made of fuel. Clearly, we need to get creative.

If we can manage to reduce the range requirement, we may be able to have a realistic fuel fraction. One way would be to observe that the gifts leave the aircraft with significant energy. If they were to have guidance packages, we would be able to deliver gifts across a wide area, within a "cross-track range". This range can be estimated with an energy equation, and an assumed lift to drag ratio of the gifts.


Given an L/D_gift of 15, we can see that at mach 4, the cross track-range exceeds half the width of the South American continent. We can thus see that we can optimise speed to cover the entire continent within two passes, a southbound leg and a northbound leg.
Unfortunately, we still don't have quite enough range to cover our mission requirements, and we may have to ask the American Airforce for mid-flight refueling.

On the other hand, we can start to get creative with efficiency. If we were to increase the L/D ratio from 7 (the Concorde) to 14, we would double the effective range of the aircraft, and meet our mission requirements. Without going into too much detail, we must respect the mission speed, and it is best to respect the existing wing-loading at this stage of analysis. That leaves us with atmospheric density. If we were to fly at a higher altitude, we would have a higher absolute speed, while increasing the lift coefficient and keeping the drag coefficient constant. We then see that our target altitude is only 15'000 m, a relatively common altitude for business jets. Thus the aircraft has reasonable design parameters for the main vehicle.

Now we turn to the glide pod. Recalling the energy equation we used to convert to range, we must cause the pod to adjust from Mach 3.5 to its best glide speed. Unfortunately, for a "standard" glide speed of 60 knots, the equivalent energy altitude is 87 km, which would be reached if we were to convert all the excess speed (kinetic energy) to altitude (potential energy). At this altitude, the air is extremely thin, as we are at the edge of space. If we were to use our previous approach of adjusting for low density, the required airspeed to meet our lift requirements would be 7.8 km/s. It would thus be prudent to embrace ballistic flight. Fortunately for us, Burt Rutan again has beat us to the punch. This is the spaceship one, which is designed to "belly flop" from vacuum into the atmosphere, and use a levered tail boom to recapture the airflow and force the aircraft back into controlled flight. In this way, we can control re-entry without losing energy unnecessarily.


Finally, we turn to final aircraft mass. With half of the aircraft dedicated to fuel, we would be prudent to dedicate at least 30% to structure and systems, leaving 20% for payload. As payload is the only known value (recall we need 20'000 tons of gifts), the aircraft must thus be 100'000 tons. For reference, the late AN-225, the largest aircraft to ever fly, is only 650'000.
Given these fractions, however, it is not unreasonable to believe that we can create a structure that meets these requirements. It is likely to be challenging.

Assuming we can meet them, that results in a wing surface that must cover 194'000 m2. Using a relatively limited AR of 5, that would give us a wingspan of close to a kilometer. Quite the sleigh. In the lower picture, you can see Santa for scale.

So, in conclusion, I can provide Santa with a credible upgrade to his current delivery solution. I think it's safe to say he has the infrastructure to support this vehicle, or if not, has the labor force to upgrade his existing airbase.

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Pie Aeronefs SA
Rue de la Tannerie 6
1315 - La Sarraz

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