Aircraft

Swiss eVTOL demonstrator aircraft takes to the skies

Swiss eVTOL demonstrator aircr...
The tech demonstrator lifts off
The tech demonstrator lifts off
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The aircraft has a 4.5-meter (14.8-ft) wingspan
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The aircraft has a 4.5-meter (14.8-ft) wingspan
The aircraft is completely electrically powered
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The aircraft is completely electrically powered
The tech demonstrator transitions to forward flight
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The tech demonstrator transitions to forward flight
The just-completed first phase of testing included 550 individual test flights
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The just-completed first phase of testing included 550 individual test flights
The tech demonstrator lifts off
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The tech demonstrator lifts off
View gallery - 5 images

Although numerous companies are now developing so-called "air taxis," many of those groups currently have nothing but renderings of their planned aircraft. Switzerland's Dufour Aerospace, however, recently completed the first phase of testing of a large-scale demonstrator.

Like pretty much all other proposed air taxis, Dufour's demonstrator is an eVTOL. That stands for electric vertical take-off and landing, describing a battery-powered aircraft that can take off and land like a helicopter, but then switch into faster and more efficient fixed-wing flight while cruising.

It's also what's known as a tilt-wing aircraft, in which the entire wing – along with its motors and propellers – tilts from a horizontal to a vertical orientation. There are also tilt-rotor airplanes, in which the propellers/rotors tilt independently of the wing. However, Dufour figures that its approach (which was inspired by the experimental Canadair CL-84 aircraft) is a better way to go.

"A tilt-wing does not lose efficiency due to down-load from the prop wash onto the wing," Dufour CTO Jasmine Kent tells us. "Indeed, the props keep airflow attached to the wing, enabling much faster and more efficient transitions between hover and cruise modes of flight than a tilt-rotor. It also saves weight and complexity by having only one tilt mechanism."

The tech demonstrator transitions to forward flight
The tech demonstrator transitions to forward flight

The just-completed first phase of testing included 550 individual test flights, in which the demonstrator "demonstrated a high degree of stability and control in all conditions, including transitions from hover to cruise and back again."

Kent says that the fully-electric aircraft, which was developed in partnership with the ETH Zurich research institute, has a 4.5-meter (14.8-ft) wingspan – this reportedly puts its aerodynamic behaviour in the range of the company's planned passenger-carrying aircraft, known for now as the aEro 3.

No other specs on the demonstrator or the aEro 3 are being released at this time, but you can see the former in flight, in the video below.

Source: Dufour Aerospace

Dufour VTOL tech demonstrator

View gallery - 5 images
11 comments
guzmanchinky
Very cool efficient looking design. I wonder if it makes sense to build a quadrotor like this with one wing in the front and one in the rear, seems like it might be more stable in hover? But then you have two tilting wings which is more complex and heavy I guess...
Johannes
Nice, simple electric craft that's also quite attractive, in flight mode at least.
McDesign
Maybe a conventional quad rotor layout where the whole dual-wing structure rotates into a bi-plane configuration?
Karmudjun
Great look - I'm guessing this is a mock-up demonstrator - with a 15 foot wingspan, the fuselage would limit a human pilot to that of a jockey-sized person if they entered with the canopy out of the way. But knowing how balance affects flight, I presume the tilt wing mechanism right behind the cockpit might balances out the batteries and such between the tail and the wing mechanism. What size is the anticipated human capable eVTOL? Great review on the developments!
Towerman
Still just a plane with vertical props. Nothing exciting and still too big for anything other than an airport.
dan
physics: size matters!
scaling up in aviation is not possible: volume and therefore mass increases in cube, surface (wing areas!) only in square! yes, size matters. an aircraft twice as “big” is therefore 8 times heavier. this makes scaling up impossible. a quadcopter-design or any similar as a toy drone scaled up for manned operations is therefore not possible, at least for many years to come.

main problem for all eVTOLs and alike are insufficient batteries that only last for some minutes to fly… eVTOL need an additional improvement of battery performance of a factor of 50 (fifty – that means 5’000 percentage!) currently, there are no (not even theoretical) concepts how this increase of power density could be achieved.

But congrats to the Swiss, nice programming of their model plane! Next step would be any fail-safe idea how to eliminate the death zone for eVTOL in case of power loss somewhere near the ground, e.g. in circuit or when take-off or landing where most accidents happens… a helicopter could auto-rotate, a plan can glide, and an eVTOL?
Towerman
@dan... """""quadcopter-design or any similar as a toy drone scaled up for manned operations is therefore not possible, at least for many years to come.""""" That is a false statement, it has been done many times and real life flying already happening.

Furthermore the reliability of multirotors and redundancy makes them safer than winged aircraft and rotorcraft as they have basically no mechanical components and can land almost anywhere. And have redundancy built in convention old style aircraft can't compete with. And Battery tech is catching up much quicker than you guessed and other forms of powering electric Evtol's is practically becoming reality. The revolution to come is unstoppable, best to put up a smile and fully embrace it, as absolutely nothing will be able to stop it ;)
dan
@Towerman

Thanks for your reply. I would love to fly a VTOL with flux capacitor! ;-) Facts: In aviation simplicity means safety. Redundancy can increase MTBF, sure, but it always is a massive cost driver. New technology will evolve, but in particular in aviation it takes time!

OLD = SAFE As a pilot and working in this industry, we are sometimes disappointed how slowly (legal) changes/new technologies can proof safety standards and conquer the markets… Example: most small aircraft engines still don’t use fuel injection technology!!! Nobody knows the future, but I consider it foolish to believe battery technology suddenly jumps within an investor’s/owner’s time frame, e.g. 3 to 7 years.

POWER REQUIREMENTS: A decent small aircraft needs an engine of ca. 100 kW, a decent helicopter maybe 200 kW. eVTOL due to smaller propeller areas (= less efficient) in comparison to a helicopter, even more. A new TESLA (model S) battery stores 85 kWh and weights 1200 lb. And TESLA is good!

COMPLETIVE? So, for a simple airplane for a 2 hours flight plus 30 min flight to alternate plus 30 reserve time results in a 3’600 lb battery pack (flying at 85 kW). In the last decades, progress in battery technology was measured in a low one-digit percentag. But we need a jump of approximately 5’000 percentage! Ordinary fuel in comparison would have a mass of maybe 150 lb plus the same for the engine. 3600 lb vs 300 lb.

CHARGING TIME is the next issue, in particular for any (air taxi) operator. Risk of (electrical) failures could be solved by redundancy, sure, but this results in a loss of (cost) efficiency… Hybrid aircraft design may have a future, but hybrid systems are even more complex/expensive.

SAFETY: All aircrafts must be built in such a way, that they can guarantee safety in any conditions, also in the (unlikely) event of loss of power, bird strike etc. As said, an airplane can glide, a helicopter can auto-rotate etc. Neither is possible for eVTOLs in their death zone (e.g. between 10 ft and 500 ft) when taking-off or landing vertically, as a parachute could not be deployed in time.

KISS: Keep It Simply Stupid = Safety. That’s also good for business. Of course, it is possible to run a few minutes an eVTOL, but on a commercial base in compliance with aviation standards it will take mooore time or we may need a flux capacitor!

FUTURE: We safe fossil fuel by using bicycles, installing solar panels, be modest in what we do, eat, possess etc. Cost-efficiency and minimizing our footprint and ground infrastructure are increasingly important, also in aviation! In the future, we may use gyrocopters, that are simple, powerful and fuel-saving. And likely, many of us will fly highly efficient (bio-)fuel driven aircrafts. And the very, very rich will have some new toys, flying by eVTOL from JFK to Manhattan.
Towerman
""but I consider it foolish to believe battery technology suddenly jumps within an investor’s/owner’s time frame, e.g. 3 to 7 years.""

Not foolish, clever yes as it is already happening:

5 years ago, people mocked and ridiculed Elon Musks Tesla ability
to create a vehicle with good range.

Today Tesla has dumbstruck all of them by having a commercial vehicle that can go 325 miles miles on a charge.

Of course battery technology is not there yet for aircraft to give the range of ICE powered craft, however it will come, whether it be batteries or fuel cells that will be used or something entirely else.
it will happen sooner rather than later. Cost will come down and the technology will be simplified.


As for your SAFETY remark:

No that is not entirely correct.
Helicopters also have a death zone of the same distances, many helicopters have gone down because of the inertia of the rotorblades decreasing too soon in those margins causing it to fly under the power curve.
The pilot is just a sitting duck at that point.

Thats why EVTOLS and electric craft are safer than ICE craft. It has multiple redundancies, in a split second a redundant motor takes over, causing an eventless save of the aircraft.

Doesn't matter if airplanes can glide, if there is no airport, the outcome is usually fatal.

KISS: Keep It Simply Stupid = Safety. That’s also good for business. Of course: Indeed thats why EVTOL's is clearly the ultimate winner, no complex mechanical moving parts, pipes, complex fuel systems, maintenance prone mechanics.
Simply a solid state like motor with 2 bearings. The brilliance in this concept can never be underestimated ! And will completely take over in every conceivable for in the medium to long term future.
dan
Hi Towerman, thanks for your reply! I like your enthusiasm for technological progress!

I stick to the numbers: Batteries are not competitive in aviation for eVTOL-applications, this decade at least. Please read my example - and in particular for an eVTOL, the same battery would be at least twice as heavy, e.g. 7200 lb.

E.M. has done a great job. I love his visionary mind and action (TESLA, SpaceX etc.), but aviation is different to cars (power demand, safety issues etc.). And “no”, TESLA batteries are not the jump needed. They may have improved a 50 % - what is great, but eVTOLs need an improvement of 5’000 % and that is just physics/math. Sorry, that will not happen not even in laboratories near soon!

The transition from normal flight to auto-rotation is for a helicopter pilot a delicate task and yes, depending on type and skills, there is a small death zone also for helicopters. That’s why gyrocopters are really cool, as they always already fly in auto-rotation. Very safe, very simple and affordable. And gyrocopters can land within a few feet, nearly anywhere, unlike an airplane that would be in trouble without an airport, you’re right.

Most eVTOLs are mechanically less complex, sure. To “compensate” a bird strike or power loss within a fraction of time, redundancy/a lot of reserve thrust, and powerful IT/software are needed. This is costly and certifying software is a true nightmare, ask Boeing with its 737 MAX. So, looking at an eVTOL, they are not simple, they are extremely complex!

That’s why e.g. eVTOL-Lilium-team have spent $ 100 m and they are looking for another half a billion $ (!) to make it fly! So, it may look simple but actually it is very capital demanding and complex. It is quickly said “a redundant motor takes over”, but in real aviation, it is a very high goal. In consequence, a return of investment within the next couple of years (as promised by some eVOTL companies) are equally safe as investments in the flux capacitor. I like your enthusiasm but pairing it with some numbers may safe (your) money.