Purchasing new hardware? Read our latest product comparisons

Modern-day aviation pioneer achieves world's first untethered, manned electric helicopter flight


September 5, 2011

Pascal Chretien's prototype electric helicopter takes flight

Pascal Chretien's prototype electric helicopter takes flight

Image Gallery (18 images)

It's easy to look back at the history of exploration and aviation and feel like there's no mountains left to climb, that the age of the great pioneers is behind us and we're doomed to a future of LCD tanning and monitor hypnosis. But don't try telling that to Pascal Chretien. On August 12, this electrical/aerospace engineer and helicopter pilot took to the air in the world's first untethered, fully electric manned helicopter flight in a prototype machine that he designed and built almost entirely by himself within a 12 month development period. In his 2 minute, 10 second test flight, Chretien beat aviation giant Sikorsky into the record books - but it was not without significant risk. As the man himself puts it: "in case of crash I stand good chances to end up in kebab form."

With battery technology advancing steadily and electric vehicles popping up across all sorts of transport modes, electric helicopters have been one of the last dominoes to fall. That's because the dynamics of helicopter flight tend to consume a lot of energy - and in a way that doesn't fit in well with the way batteries perform.

Electric airplanes, for example, require a lot of power in the takeoff phase, but can cruise and land on fairly meager amounts of energy. But helicopters require strong power delivery throughout the takeoff, hovering and landing phases - so you have to make sure there's plenty of power in the tank to take you down softly.

So when French company Solution F contacted Pascal Chretien and asked him to build the world's first manned electric helicopter, he knew he had to come up with a pretty unique design - an ultra-light, super simple helicopter that could get a decent flight time out of its available battery power.

Designing a prototype electric helicopter

For the basics of conventional helicopter flight and definitions of a couple of the terms below, check out our " How to Fly a Helicopter" video - it really is fascinating how these contraptions work in a conventional sense.

A conventional system wouldn't work here though - a tail rotor, for example, drains somewhere between 8% and 10% of total hover power. So Chretien modeled and built a coaxial design with two counter-rotating rotors on top - a torque-balanced design that can fly without the need for a tail rotor to stop the aircraft rotating out of control - instead, it just needs a simple, lightweight tail fin.

In place of the typical cyclic control, which uses an ingenious variable blade tilting system to control which way the helicopter tilts and advances, Chretien chose an extremely simple weight-shifting system - a big set of handlebars (incorporating the collective control) that literally tilt the main weight of the aircraft underneath the rotors - as his steering assembly. But this increased Chretien's risk factor by a significant margin - because it meant the controls would be reversed compared to a normal helicopter.

As Chretien puts it: "Weight savings were substantial - 4 to 5kg compared to a conventional arrangement... But habits being second nature, after 15 years of flying conventional machines the risks of crash were quite high." So during the development phase of the aircraft, Chretien built himself a pendular weight shift training machine to get himself used to the system and make sure he didn't react the wrong way when he first took to the air.

Yaw control was achieved with a combination of electric controllers (presumably varying the speeds of the two rotors) and a mechanical linkage that tilts the tail fin against the downwash from the main rotors - and the yaw controls are operated through pedals as in a conventional helicopter design.

The frame of the helicopter was built from welded 7020 aluminum tubing - composite materials would have been lighter, but time was of the essence, and crash-worthy aluminum frames can be built in very short timeframes - plus, this decision helped keep the cost of the vehicle down.

The Powerplant

Chretien had been given a target of 10 to 12 minutes' flight time by Solution F, so the most critical part of the aircraft design was working out how to store enough power for this kind of flight, as well as how to use that power most efficiently. Early on, he sought the help of Lithium Balance , who supplied the battery management system and consulted on power storage issues.

Chretien chose brushed DC motors for the rotor shafts, even though the required power output was "just on the edge of what can be achieved with brushed motors" - because brushed motors are exceptionally efficient, and their simple controller units are significantly lighter than those of more powerful, less efficient brushless motors.

With these in place, Chretien was able to achieve an 87.5% energy efficiency between the battery terminals and the rotor shafts.

The rechargeable battery cells are Lithium ion polymer pouch cells, with an energy density of 160 Watt-hours per kg. Although reasonably lightweight, these cells presented probably the biggest danger to Chretien in the test flight phase. As he puts it: "The infamous thermal instability of lithium/cobalt chemistry does not leave room for error... It is important to take it slowly, if I don't want to wreck tens of thousands of Euros worth of hardware; but also, in case of crash I stand good chances to end up in kebab form, as LiPo batteries are notoriously infamous for bursting to flames once distorted. The chemical reaction is violently exothermic. This machine looks like a toy, and flies like a toy, but there is a raging tiger under the seat, waiting to bite at the first mistake."

Test flights

Chretien initiated a few tethered test flights earlier this year, and was able to test the action and torque balance of the rotor controllers, the weight-shift directional tilt system and the ground effect behavior of the aircraft.

And then, on August 12, it was time for the main event - the world's first untethered, manned flight of an electric helicopter, an event which lasted 2 minutes, 10 seconds up to a maximum height of 1 meter.

In this moment, Chretien and Solution F beat aviation goliath Sikorsky to the punch - Sikorsky has been working on its own project to get the first manned electric helicopter in the air, and unveiled its pre-flight Firefly prototype at the Experimental Aircraft Association AirVenture exhibition in July 2010.

But the Firefly is a much more conventional helicopter than Chretien's creation - it uses a conventional enclosed body shape, a single top rotor with a conventional swashplate and cyclic control, and a tail rotor - all of which add considerable weight, requiring additional heavy battery packs. This may have contributed to the fact that Sikorsky hasn't been able to run its first manned flight yet.

It's perhaps a little ironic that Chretien beat Sikorsky to the punch using a coaxial twin-rotor design, as Sikorsky is one of the leading proponents of coaxial helicopters - notably pushing a demonstrator version of its X2 to an unofficial helicopter speed record of 250 knots just last year.

Where to from here?

While he works on expanding the device's flight envelope, Chretien has a few things to think about after his pioneering test flight. The electric drive train needs more work, for example, and Chretien believes that "looking at the excellent power reserve we have today, it appears that we could have used a conventional cyclic [control] stick."

Before he takes the helicopter out of the ground effect zone - or above about 4 meters - he wants to refine the current yaw control setup.

Eventually, Chretien sees a hybrid drive train being the ultimate outcome of this project. To understand why this is important, you need to understand that at present, helicopter flight is nearly 40 times as dangerous as airplane flight, at about 23 deaths per million flight hours versus just 0.6 for aeroplanes.

Current figures, Chretien says, put engine failure and internal/mechanical failures down as responsible for over 40% of helicopter crashes. But if a helicopter was to use a hybrid power system, you could store backup power in the battery. Chretien says a simple system could offer 3-4 minutes of battery powered flight if the petrol engine failed, enough to land the craft safely and help to reduce that 40% of crashes.

So as he works on patents in that area and further developing his prototype electric helicopter, Chretien is certainly a busy man - he's had just six days off since last August and it's hard to see how things will slow down from here!

We wish him all the best and congratulate him on his new place in the history books.

About the Author
Loz Blain Loz has been one of Gizmag's most versatile contributors since 2007. Joining the team as a motorcycle specialist, he has since covered everything from medical and military technology to aeronautics, music gear and historical artefacts. Since 2010 he's branched out into photography, video and audio production, and he remains the only Gizmag contributor willing to put his name to a sex toy review. A singer by night, he's often on the road with his a cappella band Suade. All articles by Loz Blain

So What\'s Patentable here??

Weight shift helicopter, same as many ultralight helis made over the last 70 years.

Application of Electric Motors for spinning a Propeller, have to look at RC planes over the last 20 years.

Maybe he could patent a new way to cook Kebabs.

Shish, in the rotors, cooked via expliding Li-Po\'s.

Nice to see electrics getting air time.


I would have preffered to sit on a Lithium iron phosphate battery for its safety characteristics, the trade off on size and weight would be a small one in this application...

Johan Smit

I would suggest using inflatable pontoons for the landing gear. This would save weight, and give a soft touchdown. I feel this project is going to struggle to get any endurance.

As far as helicopters being dangerous, we are always told that they can auto-rotate to touchdown if the engine fails. Does this ever happen? I am a fan of autogyros. Surely they are more efficient than helicopters? Slower admittedly.


Next goal for Helicopters - CLOCKWORK!


James Dugan

\"Yaw control was achieved with a combination of electric controllers (presumably varying the speeds of the two rotors) and a mechanical linkage that tilts the tail fin against the downwash from the main rotors - and the yaw controls are operated through pedals as in a conventional helicopter design.\"

I doubt that the blade velocity can be varied between the two blades. More likely the blade pitch can be varied between the two blades. The blade with the higher pitch will exert more torque, causing the chopper to rotate about its vertical axis.


Terrific article, the best I\'ve read in gizmag for years.

I\'m a pilot, and the reason helicopter accident statistics are higher is actually the way they are used - not because of the helicopter.

Almost all heli accidents are from operational incidents like wire strikes, logging, Medevac and other extremely dangerous low-altitude ops. When you get down really low like helis have to, the wires, towers, antennas and trees seem to come out of nowhere.

Todd Dunning

That\'s fantastic. I just wish gizmag would let us know of the costs to develop such technology. I see he was commisioned. I have hopes of inventing things too, but have little money to invest in prototypes. I\'d like to know how much play money I would need to seriously think about inventing. So how much did this contraption cost? 100$, 1000$, 100000$, what power of ten are we talking here?


@IggyDalrymple-R/C co-ax helicopters do use differential speed between the blade sets to control yaw. I do not know if that is what is employed here; only that it is used in models quite successfully. It would seem that digital speed controls would be a much more economical and lighter approach.

Chuck Arlt

\"Chretien chose brushed DC motors for the rotor shafts, even though the required power output was \"just on the edge of what can be achieved with brushed motors\" - because brushed motors are exceptionally efficient, and their simple controller units are significantly lighter than those of more powerful, less efficient brushless motors.\"

The article seems to have this backward. Brushless DC motors are much more efficient than brushed DC motors. The carbon brushes in the brushed motors add significant friction to the system which reduces efficiency and increases heat output. This is why all modern electric vehicles and RC cars and planes use brushless DC motors. Brushless DC motors do require much more complicated electronics, and they also tend to be more expensive.

Bill Carlson

@Bill. I was thinking the same exact thing when reading the article. I always replace brushed motors, with brushless in my RC planes & heli\'s, or outright purchase a brushless with a new machine.

Joe Sobotka

I just wondered what the tail fin does. The contra-rotating blades stop any torque rotation. I suppose it works with forward motion, but is ineffective when stationary.


Right on Bill (except for the friction part of it, that is not significant).

And Chuck - I think that this probably wouldn\'t employ varying rotor speeds for yaw control as it would be slow-acting. It works for my R/C helis simply because they are small, but it would take alot of energy to change the speed of these big rotors with all their inertia. That is probably why they use the tilting tail fin.


Batteries are a lousy power source for aircraft because they do not get lighter as the energy is used. In light aviation it is not near the problem as in commercial aviation, but the carrying capacity of an airplane is decided by its maximum gross landing weight. Replacing ten tons of JP8 with ten tons of batteries, removes ten tons of cargo capacity.

When a helicopter\'s engine quits in flight they do auto-rotate often to a safe landing, this is rare because of the high reliability of aviation engines.

Auto-gyros can not take off vertically, or hover but their no power landing mode is more attractive than a fix wing plane\'s.


Re; It works for my R/C helis simply because they are small, but it would take alot of energy to change the speed of these big rotors with all their inertia. That is probably why they use the tilting tail fin. comment Blixdevil - September 6, 2011 @ 10:00 am PDT

It is not the speeding up, and slowing down the rotors that is important, it is the torque imbalance that does the work. the tail fin is just redundant.


Typo/correction on the chemistry front: It isn\'t LiPo, It\'d be LiCo, if they\'re talking about Cobalt. Po is Pollonium, and is radioactive. I\'m not aware of it being used in batteries.

Now if they were trying to say \"Lithium Ion Power Pouch\", then it\'d be LIPP, but either way, it\'s not LiPo.

Patrick Salsbury

LiPo refers to Lithium Polymer batteries.


How is this MODERN?


Sloburn - you can\'t have torque imbalance without changing the speed of the rotors or the pitch. These are fixed pitch so they cannot cause imbalance that way, they would have to change their speed. And since they are fixed pitch, they also cannot land by autorotation in the event of an engine/motor failure.


Blixdevil - September 8, 2011 @ 06:40 am PDT

The blades inertia resisted velocity change so the torque imbalance begins turning the fuselage at the same time as the rotors begin their velocity change so it is not the different velocity, but the torque imbalance.

I can not think of any production helicopter that can not autorotate.


From what I understand you have to be able to change pitch to use autorotation for emergency landing. So yeah, I guess the rotor of a fixed pitch would still turn as it falls out of the sky unpowered, but you wouldn\'t be able to reduce pitch to increase rotor speed then increase pitch at the last moment to provide lift with whatever rotor momentum you have left.


Brushless systems are far more efficient than brushed systems: Look at the development of electric flight, where today you are hard pressed to find any brushed motor for sale, while there are hundreds (probably thousands) of brushless motor variants for sale, as the are far more efficient, and that goes for the complete systems as well: Longer endurance, or higher power, or both, for the same power plant weight (batteries, speed controller, motor, motor mount, and propeller). For instance, a 3 kW brushless motors cost very little today, while twenty years ago (when I began flying electric) there just wasn\'t any available! My smaller brushless power systems came from Aveox (CA, USA), and cost about ten times as much as similar power plants cost today (actually more than that, but for the case of argument, let\'s say ten times), as they then were manufactured at high standards in California, while most of todays brushless come from China, where salaries are lower.

So Aveox, which still is around, just makes systems today for the \'US military complex\', and similar well-heeled customers (like Hollywood).

Tord Eriksson

An Agni brushed motor has 91% efficiency, whereas a Plettenberg Predator 37 brushless has 86 to 89% efficiency. Brushless motors are not necessarily more efficient than brushed motor. Efficiency has a lot to do with mechanical design, such as the air gap between rotor and magnets. When designing an electric drive train it is important to consider the system as a whole, and not only one component. The controller is very important, and the solution used in this project is very efficient thanks to their controller, and a not so bad motor.

Stephane Arsonneau

Looking at the pictures, and as a retired aeronautical engineer, I can say that this machine is loaded with very clever concepts, except for one thing: There does not seem to be any significant firewall between the battery pack and the pilot\'s seat. The logic behind the madness seems to be the cooling of the battery pack. Those guys are very smart, but traded performance for safety. The pilot has more balls than brain. They really wanted to get there, obviously; and deserved their price.

Dave 67

I just stumbled upon this article, recently as well as the other electric helicopter flight reference on You Tube of the German team who built a multi rotor heli using BL motors. Having designed some of the smallest RC electric helis before the revolution of the Micro, Sub-Micro and Palm Size (MIA TM), I have been working also on my own personal single man carrying helicopter design for the past 12 some years. No not every day not even every month, but whenever the building bug set in, as I have not been too keen on making a mark with this as I did with my first "Slow Flight Super Ultralight" 4 ounce 20" rotor RC Electric Micro helicopter, the pre 2000 MIA Sport LE and subsequently the Ultralight 8 ounce 20" rotor MIA Robin 280, and due to many other commitments, I've been taking the design and build process slowly, My energy level is not as it use to be 20 years back and I have learned that there are more important things in life than to be on a race to make a mark, I've already done that when I established MIA Micro-FLIGHT. But I too built a real man operable simulator a number of years back as I did nearly 25 some years when I also built a scale sim for RC helis, when I was learning to fly. Generally speaking, once you have a good idea of how a Radio Controlled helicopter is put together, building a single man carrying helicoper with todays technolgy is rather a piece of cake, especially coaxials. While one with the right experience in this area and knowledge of helicopters, electronincs, can scale up a Coaxial RC heli, fairly easily, with off the shelf components, there are many areas that have to be carefully considered for safety. The Inventor and article touches up on the dangers of Li-Pol batteries, and Mechanics failure. All this can be easily resolved with the proper design something I have pondered since the invention of BL motors and Li-Pol technology and I think I have it figured out. In retrospect, it is amazing that Hiller achieved a single man carrying portable heli back at the time he did the Hornet. My heli is tottaly ifferent than what I've seen inluing some of the most recent electics real man carrying helis, but I will not disclose it until it is fully finctionable hoping to do it slowly and within my time frame on this planet. Like I said I am in no hurry to compete or break world records but I am been careful not to duplicate anything that has been done before. I have specific ways I design RC models, and many Upgrade products and have locked on a few methods that work at both RC and Real scale and I want to remain true to this aproach so that my helicopter will be easily recognizeable as a MIA Design. Obviously to anyone who is familiar with Brushless Motors v. Carbon Brush Motors , the article is indeed backwards. The photos do show BL motors on the helicopter. A SIMPLER AND PERHAPS MORE OBVIOUS SOLUTION TO THE HELI IN THIS ARTICLE WOULD BE TO TAKE THE LESS COMPLEX GAS OPERATED COAXIAL THE OTHER GENT ON YOU TUBE SHOWS AND RETROFIT BL MOTORS ON IT, YOU CAN STILL WEIGHT SHIFT IT WITHOUT MUCH COMPLEXITY SIMPLY BY PUSHING AGAINST THE TRI LG LEGS. MY OPTION IS MUCH SIMPLER...

Mario Arguello

Mario Made some valid comments on batteries. It looks like Pascal Chretien’s coaxial helicopter is a simple solution to demonstrate that all the technological bricks are now available for a new breed of power plant.

I did a couple of searches, and found that those folks have indeed lodged a couple of patents applied to highly redundant direct drives applied to rotary wing aircrafts.

Dave 67

I admire his work and would love to see how far he takes it,but a multirotor setup, verse's those two slice and dice coaxial blades,seems to be the better choice.First it eliminates all those complex mechanical systems,it uses small electric motors with small fix pitched propeller's,it is capable of flying with less than all it's motors, and,because its fly by wire,it can be fitted with a redundant system,as a backup, in the advent complete loss of all systems .Even if both systems failed you still have one last way to save yourself,a ballistic chute,which can be fitted to a multicopter, pretty easily,compared to a conventional helicopter, because of the layout and use of small motors and propellers. .Personally I think,multicopters could be the answer to affordable and safe flight for everyone,I guess time will tell.

Thomas Lewis

How come there's no video?


See the GWR: http://www.guinnessworldrecords.com/world-records/9000/First-electric-helicopter

Designing a tailor made helicopter around the powerplant was the most sensible approach and is a far better way than fitting an existing machine with an electric drive which always leads to a heavier solution. Because of their lower disk loading, helicopters offer better propulsive efficiency than multicopters hence are the best host for such propulsion where energy is scarce.

Michael Rogers

Strange how dogmatic comments can be when it comes to brushless motors versus brushed motors. As someone rightfully noted, there is no significant efficiency gap between the two technologies. The difference is more on the long term reliability: a brushless motor is far superior; however brushed motors have been in the industry for decades and perform well, when properly maintained. Reading the article, it comes clear that the DC motor-MOSFET controller solution was retained to optimize the weight budget (at the expense of long service life). For a machine designed to break a record, this choice makes a lot of sense as it offers good end-to-end efficiency combined with the lightest solution resulting from the use of light & highly efficient controllers. A production machine might not utilize the same motors, but it did the job in the context of a demonstrator. There is no doubt that this machine will be followed by other electric helicopters, but that one has the merit to be innovative and create a milestone. For the first time in the history, aircraft propulsion is undergoing a change of paradigm and this is really exciting! MR

Michael Rogers
Post a Comment

Login with your Gizmag account:

Related Articles
Looking for something? Search our articles