First public test flight of Airbus electric 2-seat E-Fan aircraft at E-Aircraft Day; precursor to 4-seat extended range version
27 April 2014
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| The successful first public flight of the electric E-Fan experimental aircraft took place during the E-Aircraft Day in Bordeaux. Click to enlarge. |
The Airbus Group’s electric E-Fan experimental aircraft made its first public test flight at E-Aircraft Day in Bordeaux, France. The electric E-Fan training aircraft is an innovative technology experimental demonstrator based on an all-composite construction.
Airbus Group plans to further develop the E-Fan technology demonstrator and to produce and market two versions of the aircraft by a subsidiary named VoltAir. The two-seater version E-Fan 2.0 will be a fully electric training aircraft powered only by batteries. The four-seater version E-Fan 4.0 will be a training and general aviation aircraft which will also have a combustion engine within the fuselage to provide an extended range or endurance.
First presented in the static parc at the Paris Air Show in 2013 (earlier post), the two-seat E-Fan features two electric motors with combined power of 60 kW, each driving a ducted, variable pitch fan. Total static engine thrust is about 1.5 kN, with the energy being provided by two battery packs located in the wings. The length of the aircraft is 6.7 meters with a wingspan of 9.5 meters.
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| The all-electric E-Fan training aircraft. Click to enlarge. |
The duct increases the static thrust, it reduces the perceived noise and improves safety on the ground. The E-Fan is the first electric aircraft featuring ducted fans to reduce noise and increase safety. With the engines located close to the center-line of the aircraft, the E-Fan also has very good controllability in single-engine flight.
Another innovation of the E-Fan is its landing gear, which consists of two electrically-actuated retractable wheels positioned fore and aft under the fuselage, plus two small wheels under the wings. The aft main wheel is driven by a 6 kW electric motor, providing power for taxiing and acceleration up to 60 km/h during take-off, reducing overall electrical power consumption in day-to-day operation. The maneuvering of the aircraft on the ground and the initial acceleration on take-off without the main engines can so be done completely silently.
To guarantee a simple handling of the electrically powered engines and systems, the E-Fan is equipped with an E-FADEC energy management system.
As a first for an electrically powered aircraft, the E-Fan also features a pyrotechnically deployed airframe parachute rescue system.
| A five-minute view of design, assembly and first flight on 11 March 2014. |
The E-Fan’s motors are powered by a series of 250V Lithium-ion polymer battery packs, comprising 120 40Ah, 4V cells made by KOKAM. The batteries are housed within the inboard part of the wings outside the cockpit, and provided with venting and passive cooling. Because of timing and availability constraints, off-the-shelf Lithium polymer batteries are used in the technology demonstrator, giving an endurance of between 45 minutes and 1 hour. New batteries with a higher energy density will be installed later on, which will increase the endurance to up to 1 hour + 15 minutes reserve.
The batteries can be recharged in one hour, or they can be rapidly replaced by means of a quick-change system (not yet available on the demonstrator aircraft). An on-board 24 Volt electrical network supplies the avionics and the radios via a converter. A backup battery is provided for emergency landing purposes.
Take-off speed is 100 km/h (54 knots); cruising speed is 160 km/h (86 knots); maximum speed is 220 km/h (119 knots).
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| Plan view and cross-sections of the wing show the E-Fan’s battery installation. Click to enlarge. |
Airbus sees the two-seat E-Fan as particularly suited for short missions such as basic pilot training, glider towing and aerobatics, with a flight endurance of one hour for pilot training and 30 minutes for aerobatics. E-Fan can bring significant benefits in terms of cost per flight hour in the general aviation domain, Airbus suggests.
Accordingly, Airbus Group and its partners are aiming to perform research and development to construct a series version of the E-Fan and propose an industrial plan for a production facility close to Bordeaux Airport. Airbus Group’s research efforts support the environmental protection goals of the European Commission, as outlined in its “Flightpath 2050” program.
An interesting development.
These could be he first practical full BEP (Battery Electric Planes) and the first practical PHEP (Plug-in Hybrid Electric Planes).
As rechargeable batteries improve by 2X to 5+X, BEPs could become a good solution to reduce air and noise pollution, specially for training and private planes. Larger PHEPs could eventually be used for short range commercial flights
Posted by: HarveyD | 27 April 2014 at 07:37 AM
Agree, Harvey. The twin ducted fans are done perhaps for jet-style effect as a low-cost jet trainer, but is not the most efficient nor cost-effective method of propulsion. Considering the small size of e-motor and the low top speed of 120 kts, a single fixed-pitch propeller in the nose of the aircraft would provide increase efficiency of above 30% plus being much cheaper and lighter. For higher top speeds, a variable pitch propeller would be necessary, and such a sleek airframe with retractable landing gears would yield much higher topspeeds once the ducted fans are removed and more powerful motor is installed. A 100-kW motor with a variable-pitch 2-blade propeller up front can easily yield 160 kts or higher, for aerobatic or racing purposes.
Electric propulsion may be the salvation for the ever stagnant general aviation industry, still relying on WWII tech monstrous-sized aircooled piston engine that are very expensive, big and heavy, and burning leaded fuel that is very expensive and polluting. Those engines often failed catastrophically on takeoff, killing the occupants, thus dampen public enthusiasm for general aviation.
Electric motors are much cheaper, lighter, and infinitely more reliable than WWII-age piston engine, maintenance-free, and will last forever. Electricity as fuel costs perhaps 1/12th the cost of Av gas. With the upcoming 5-5-5 batteries, BEP (Battery Electric Planes) will be competitive with petrol planes in term of speed and range, while being infinitely safer and cheaper to operate. With computerized navigation and piloting and electric propulsion and satellite-base weather prediction, General Aviation will be 10x safer and perhaps will be grow much faster than ever before.
All the reasons that has killed people in GA planes before can now be eliminated, such as bad weather (satellite weather display and prediction), poor navigation (now with GPS), engine failure (now with fail-proof e-propulsion), airframe failure (airframe parachute), and pilot errors (computerized piloting and navigation).
Posted by: Roger Pham | 27 April 2014 at 08:27 AM
The idea of an electric towplane for sailplane launch is interesting, but I believe there's already been an electric self-launching sailplane.
An electric trainer for pattern work is certainly going to slash the noise and cost of flying.
Posted by: Engineer-Poet | 27 April 2014 at 08:50 AM
The Lange Antares is an electric powered sail plane.
http://www.lange-aviation.com/htm/english/news/news.html
I was researching axial electric motors and came across a guy who just put an electric motor and prop on a pole behind the cockpit as a pusher like the Antares. He was able to take off from most small airports without a tow.
Posted by: SJC | 27 April 2014 at 10:42 AM
This is the one, the Emrax motor on the Apis sailplane in Solvenia.
http://www.enstroj.si/Glider-products/electric-apis.html
They have videos of it taking off and flying.
Posted by: SJC | 27 April 2014 at 10:52 AM
The major difference with these units are that Airbus has all the technical and financial resources required to mass produce and commercialize BEPs and PHEPs worldwide.
Posted by: HarveyD | 27 April 2014 at 01:09 PM
Sometimes it needs to be shown that it can be done. RC hobbyists have been flying motorized gliders for quite a while, the Antares and Apis showed it could be done at full scale with a pilot.
In January 2007 the Volt was announced, many people knew a series hybrid would work and those beliefs were reinforced after the announcement. There was a greater response to that announcement on here than I had seen to any other story.
It is easy to criticized and tear down, but those that know it can be done persevere.
Posted by: SJC | 28 April 2014 at 07:07 AM
roger> fail-proof e-propulsion
That's probably optimistic. I'm enthusiastic about electric propulsion for small GA aircraft, and confident that they can be more reliable than a typical Rotax 912 but I have no illusions that they will be fail-proof. No mechanical or electronic assembly is fail-proof.
Cost and maintenance of aircraft motors will undoubtedly be a fraction of current aero engines.
Posted by: electric-car-insider.com | 28 April 2014 at 08:48 AM
@EC-insider,
No, fail-proof e-propulsion is feasible. I meant exactly what I stated. Just look at this twin e-fan plane. Electronics can typically have MTBF of about 1:100,000 hrs. Those two fans can have separate motor controllers and batteries to increase redundancy. In the case of the failure of one fan, the other can still fly the airplane to a landing site, usually in less than an hour's time. It would take a failure of BOTH fans within an hour to cause a forced landing.
So, 100,000 hrs square would equal to 10 billion flight hours. Now, yearly General Aviation in the USA logged ~20 million flight hours. So, it would take the whole fleet of General Aviation in the USA using twin-motor aircraft, 500 YEARS to have a single aircraft with failure of BOTH motors within an hour to cause a forced landing. That, my friend, is practically fail-proof! In 500 years, we probably will be using WARP drive to get to Mars and back within the same day!
A single propeller airplane can be driven by 2-3 motors geared to a single main spur gear, each motor has seperate motor controller and switches and relays for redundancy. This would reduce the cost of having multiple propellers, but cannot guard against propeller failure which is very rare.
Or, twin propeller aircraft can be used, one in the front and one on the rear of the aircraft to avoid thrust asymmetry, similar to the Cessna 337 Skymaster.
Or, twin wing-mounted motors /propellers can be used, however, these are computer-monitored for adverse yaw such that if one motor or propeller shouuld fail on one side, the computer will shut off power to the other motor while trim the aircraft for asymmetric thrust and then gradually advancing the remaining functional motor.
Please note that electric motors are much smaller, cheaper, and lighter and can be scaled much smaller than aircraft piston engines. This means that smaller but multiple motors and propellers are feasible whereas not practical with piston engines for small planes. A three-propeller configuration can be used, with one in the nose and one on each wings of the aircraft to minimize thrust asymmetry issue in the case of a single engine failure. The failure of a single motor in a tri-motor plane means that the airplane can still climb and arrive to destination with the 2 remaining motors/propellers.
Posted by: Roger Pham | 30 April 2014 at 03:50 PM
The failure of any two motor/propeller units in a tri-motor plane means that the aircraft can still maintain altitude to the nearest landing site, usually less than an hour's away, and not be forced to land in inhospital terrains where damages can occur. So, if one take 100,000 hrs and cube it, the probability of all 3 motor/propeller unit failure within the same hour would be: 100,000^3 = 1,000,000,000,000,000 hrs !!! At the 20 million flight hours/yr of General Aviation in the USA, it would take 50 million years.
Posted by: Roger Pham | 30 April 2014 at 04:12 PM
Using 3 smaller e-motors for added redundancy should not be a major problem.
However, some sort of (to be developed) ultra light power generator will be required for extended range, mid-size e-planes, at least until such times as 10X+ batteries are available.
Posted by: HarveyD | 01 May 2014 at 09:05 AM
@Harvey,
A generator and a motor to use the power from the generator would add a lot of unnecessary weight (and cost) to the plane. It's kinda of duplication of effort!
Instead of a ICE power generator and a motor to absorb that power, simply connect a fixed pitch propeller to the engine at the nose of the aircraft for cruise thrust. Thus, a simple light-weight shaft to transfer the torque from the engine to the propeller will take over the function of the generator and motor.
So, imagine a hybrid plane (HEP) having three power plants connected to 3 propellers. Two e-motors will be on the wings for takeoff and climb power and one small-size ICE will be mounted on the nose just for horizontal cruise. In flight, the propellers on the wings will be stopped and feathered to reduce drags since their thrusts are no longer needed for cruise. The airplane must be efficient to be able to cruise at a thrust to weight ratio of 1:20 or lower, since the ICE having 1/3 of the total takeoff power can only operate at 50-75% of peak power for peak efficiency. E-motors and small ICE can make the plane more efficient aerodynamically.
Thin and flat flexible solar PV's can be embedded into the wings to recharge the batteries during flight in order to help reduce the size of the batteries and extend the cruising range. At current battery technology, the batteries should be sized only enough to take the plane to the nearest landing site should there be a failure of the engine.
However, when 5-5-5 batteries will arrive, there will be no need for the ICE any more for range of up to 400 miles. For longer range and/or rapid refill, the hybrid plane architecture (HEP) still be needed as I outlined above. Bette ICE technology will also be needed, like turbo-charged direct injection and electric turbo-compounding automotive engine to make GA more appealing and more useful to the public.
Posted by: Roger Pham | 01 May 2014 at 12:14 PM
@Harvey,
One can consider FC + compressed H2 to be a 10X battery. Due to the cost and weight of the FC unit, perhaps some high-power battery can be used for augmenting takeoff power so that the size of the FC stack can be reduced. This would be simpler and greener and much cheaper than using gasoline in a HEP (Hybrid Electric Plane).
Posted by: Roger Pham | 01 May 2014 at 04:16 PM
An ultra light FC could generate enough power for the central electric prop to safely 'power glide' to the nearest airport or landing pad when batteries run out. The on-board GPS could indicate and guide the pilot to the nearest landing place.
Yes, future lower cost higher efficiency solar cells could eventually supply enough power for extended low speed day time operation.
Yes, in the post-2020 era, improved 5-5-5 batteries will make small e-planes a low cost reality?
Posted by: HarveyD | 02 May 2014 at 08:19 AM
China may soon start manufacturing up to 1,000 Bombardier Q400E for the local market.
A similar deal with Russia may be falling out due to Canada's stand on the Ukraine and Crimea situation.
Posted by: HarveyD | 02 May 2014 at 08:27 AM
The E-Fan blades are variable pitch. This adds to the range of performance from this airplane in various situations.
And as I understand it, the ducted fans are much more efficient than open props of the same diameter.
The tips of the blades are moving the fastest, and there is a rotating ring capturing the ends of the blades so almost no air slips around the tip. The air flow is directed into more parallel direction by the duct.
Wikipedia says that ducted fan are up 94% more efficient than the same diameter open prop.
Posted by: NeilBlanchard | 20 July 2014 at 05:17 AM