An Electric Helicopter Lifts Off – Briefly

Dean Sigler Electric Powerplants, Sustainable Aviation 4 Comments

Gizmag apparently beat everybody to this story, with even Popular Science quoting from the online gadget hunter’s web site.

They report that in mid-August 2011, Pascal Chretien piloted his creation, a coaxial rotor, twin Lynch-motored helicopter that he built for Solution F, a Swiss racing engine development firm.  He performed the flight “in the presence of a court appointed witness,” according to a press release from Lithium Balance, the firm that supplied the battery management system (BMS) for and acted as consultants to the project.  The “first” Chretien claims is a carefully parsed one, an “untethered, fully electric manned helicopter flight in a prototype machine.”  The fact that he designed and built a unique machine and flew it in a 12 month span makes the two minute, 10 second flight all the more remarkable.  Solution F asked for a 10 to 12 minute flight, so more news will be coming, undoubtedly.

Battery management system - the most complex part of the helicopter

As Lithium Balance notes, “With degrees in Electronics and Aeronautical Engineering along with a commercial pilot’s license, Pascal had all the ingredients except one – battery systems expertise,” which the firm was happy to supply.  They used Kokam pouch-type lithium-polymer batteries with their BMS monitoring and controlling charging and discharging.

The mechanical parts were more to Chretien’s liking, with his use of welded 7020 aluminum tubing for the frame (a choice over the longer development time for composites), coaxial blades to simplify controls and eliminate the need for a tail rotor (which would have drained power from the main rotors), and a combination of varying the speed of the two rotors to give yaw control, and using weight shift by the pilot for pitch and roll controls.  The designer even built a “pendular” simulator on which he could practice control movement and body control before actually attempting flight on his machine.

Dual Lynch motors, pulley system and simplified control system

“Ultra-lightweight inverters” from Kruspan control the Lynch brushed motors and a simple pulley system supplies power to the rotors.  The light weight and simplicity of the design undoubtedly helped Chretien achieve his initial goal.

As Lithium Balance explains, “As much as possible was simulated and tested using CAE (computer aided engineering) before being built and Kokam had to supply video evidence of the pack running at 5C continuously without overheating, after all as Pascal said ‘I don’t want to be a barbecued frog!’”

Pascal Chretien in flight - a noteable first

Gizmag expanded on the exothermic exigencies of the power source.  “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.’”

Luckily, Chretien has not ended up as a barbequed frog kebab, and we can only wish him continued good fortune in his endeavors.


Comments 4

  1. Dear Dean Sigler,

    The news of the flight of Chretien Pascal is a world premiere of our site INFOAVION through its partner in France Christophe Hernoult, published on September 1, 2011. (Gizmag published it on September 5). I personally also post it on the Facebook wall of the CAFE Foundation on September 1. Congratulations Dean! CAFE’s blog is excellent.

    (Adolfo, thank you for informing me of your excellent site. Now CAFE has another source to call on.)

  2. “Kokam had to supply video evidence of the pack running at 5C continuously without overheating”
    Very amazing when you know how those batteries cells are working, and how KOKAM is managing its communication…

    A world premiere ? Without witnesses, except a very bad photographer ? No news except Gizmag, Infoavion and Cafe Blog ? Amazing…

    (Editor’s Note: Dozens of blogs ran this story, but with pretty much the same materials from Gizmag. Your CAFE editor found corroborating evidence from other sources, as noted in the entry. How are Kokam battery cells working and how does Kokam manage its communication. They are used throughout the world and there seems to be no evidence of their being defective or unsafe.)

  3. Dear Dean Sigler,

    I confirm you what says Adolfo. Infoavion was the first web site spread this information.

    Christophe hernoult

  4. During our recent visit to Europe, I had the opportunity to stop in Venelles and could visit Solution F. I have seen the helicopter there, hung at the ceiling. I met a gentleman whose name is Al, who saw the helicopter in flight, back to August 2011. I asked him to comment on the program and the flight tests. His recollection was that the main purpose of this small helicopter was to validate technological bricks, including energy storage and new battery cooling solutions.
    Al mentioned that at some stage Chretien and Solution F had difficulties in obtaining a permit to fly from the authorities, as there was apparently no suitable category where to fit this rather unorthodox machine. Consequently, all flights were conducted on private property and the flight envelope had to be drastically reduced to not enter into what is legally defined as airspace. Al witnessed several hovers, with some of them extending up to 10 minutes, but the machine was never allowed to do a circuit.
    Apparently Chretien has developed a breakthrough in distributed electromagnetic transmissions for helicopters with an application to UAV. After spending some months trying to interest the local industry, Chretien finally left and is now developing this technology elsewhere. Al mentioned that Chretien was frustrated by the total lack of support from the local authorities and the industry.
    This small helicopter is really unique; conducting the whole program in less than a year is quite an achievement, too. Solution F are heavily involved in the development of hybrid vehicles and racing. We saw some amazing testing facilities, there. Pedro.A.

Leave a Reply

Your email address will not be published. Required fields are marked *