Electric Motors and Controllers for Use in ... - CAFE Foundation

This is my presentation for the Third Annual Electrical Aircraft Symposium at the Hiller 

Aviation Museum in San Carlos, CA. I have added several links that were not in my 

original notes, but that I hope will help guide readers to form their own conclusions, and 

possibly add to the core of knowledge we hope to collectively build. 

San Carlos, April 24, 2009 

1

This presentation is an expansion of a talk I gave at the 2008 Tehachapi gathering of the 

Experimental Soaring Association. Dr. Brien Seeley heard that presentation and asked me 

to do a similar show for the 2009 San Carlos CAFÉ symposium. 


2

“The many experiments made during this last quarter of the nineteenth century have given considerable 

i impetus to the h question i of f guidable id bl bballoons. ll Th The cars furnished f i h d with i h propellers ll attached h d in i 1852 to the h 

aerostats of the elongated form introduced by Henry Giffard, the machines of Dupuy de Lome in 1872, of the 

Tissandier brothers in 1883, and of Captain Krebs and Renard in 1884, yielded many important results. But if 

these machines, moving in a medium heavier than themselves, maneuvering under the propulsion of a screw, 

working at an angle to the direction of the wind, and even against the wind, to return to their point of 

departure, had been really ‘guidable,’ they had only succeeded under very favorable conditions. In large, 

covered halls their success was perfect. In a calm atmosphere they did very well. In a light wind of five or six 

yards a second they still moved. But nothing practical had been obtained. Against a miller's wind-- nine yards 

a second--the machines had remained almost stationary. Against a fresh breeze--eleven yards a second--they 

would have advanced backwards. In a storm--twenty-seven to thirty-three yards a second--they would have 

been blown about like a feather. In a hurricane--sixty yards a second--they would have run the risk of being 

dashed to pieces. And in one of those cyclones which exceed a hundred yards a second not a fragment of them 

would have been left. It remained, then, even after the striking experiments of Captains Krebs and Renard, 

that though guidable aerostats had gained a little speed, they could not be kept going in a moderate breeze. 

Hence the impossibility of making practical use of this mode of aerial locomotion. 

“With With regards to the means employed to give the aerostat its motion a great deal of progress had been made made. 

For the steam engines of Henry Giffard, and the muscular force of Dupuy de Lome, electric motors had 

gradually been substituted. The batteries of bichromate of potassium of the Tissandier brothers had given a 

speed of four yards a second. The dynamo-electric machines of Captain Krebs and Renard had developed a 

force of twelve horsepower and yielded a speed of six and a half yards per second. 

With regard to this motor, engineers and electricians had been approaching more and more to that 

desideratum which is known as a steam horse in a watch case. Gradually the results of the pile of which 

Captains Krebs and Renard had kept the secret had been surpassed, and aeronauts had become able to avail 

themselves h l of f motors whose h lih lightness iincreased d at the h same time i as their hi power.” ” 

Robur the Conqueror, Jules Verne 


3

Harpers Magazine, in 1901, published this cartoon, with this telling caption. Often, 

because no immediate commercial reward can be gained from a new invention, there is no 

reward or recognition for the inventor. Often, since existing technologies are adequate to 

dissuade hopeful visionaries from wasting their time in the new field, promising 

alternatives to the current reality are neglected. 


4

This book, a compilation of articles from Popular Science and Popular Mechanics magazines 

of the 1920’s and 1930’s, reflects on the folly of trying to predict the future. Almost none of 

the predicted marvels in the book came to pass – many are still awaiting an entry in the 

hoped-for world of the future. 


5

As with all generalities, my outline is subject to occasional excursions into areas of related 

interest, if not strict adherence to the categories shown. 


6

Following a heart attack in April, 2004, I had time to recuperate and engage in leisure 

reading. On a trip not authorized by my doctor, I had my daughter Beth drive me to a 

favorite magazine shop in Portland, Oregon, where I purchased the current edition of 

Quiet Flyer, which featured Rob Honeycutt’s amazing Extra 330L. 

I was able to deduce that a 28-pound airplane that could hover had to be putting out at 

least 28-pounds of thrust. It turned out to be better than that, and I was able to conceive 

that these little model electric motors could power a sustainer power pack for sailplanes. 

Assuming a 524 pound AUW sailplane with even a modest 25:1 lift to drag ratio, it would 

require only 20.96 pounds of thrust to maintain altitude at its best l/d speed. 


7

One has the option to select a single large motor or two or more smaller motor to get the 

desired thrust. Rob Honeycutt used twin Hacker motors in his successful Extra 330L, using 

a speed reduction drive to the prop. 

Hacker followed up with multiple motors in geared drive arrangements – a twin-motor 

item and a four-motor design that produced 87 pounds of thrust through a 30-inch 

propeller, and cost $2,995. Because the four motors required four electronic speed 

controllers and four battery packs, it and the twin-motor system shown above were soon 

replaced by y larger, g single g motor designs. g 

http://www.hackerbrushless.com/ 


8

Most model motors in the size ranges of interest in this presentation are brushless, and are 

either inrunners or outrunners. 

Inrunners are built like traditional brushed motors, but take their speed control from an 

electronic speed controller. 

Outrunners reverse the major parts of the inrunner motor, with the stator mounted in a 

fixed, central position, and the rotor spinning around in the outer casing of the motor. The 

propeller is fastened to the spinning casing, a great deal like the configuration of WWI 

rotary engines. 

Taking signals from the speed controller, the motors outer magnets are turned on an off at 

120-degree phased intervals. Each time a pole is activated, it draws the rotor toward it. 

The speed controller acts as the interface between the battery and the motor. Since the 

battery is always at the same voltage, the controller has to modulate that power to allow 

the motor to turn at different speeds. 

A series of MOSFET transistors act as switches in the speed p controller and vary y the width 

of the pulses sent to motor. 


9

Electronic speed controllers (ESCs) must be carefully matched to the intended motor. 

Brushless motors do not receive electricity directly from the batteries that power them, but 

have that current modulated by an electronic speed controller. There are several features 

of electronic speed controllers typically used in model aircraft that we should consider. 

If the full voltage from the batteries was passed uninterrupted to the motor, the motor 

would run at whatever speed the available voltage allowed. 

For determining how to match a motor and propeller, a motor performance parameter, kV, 

or revolutions per minute per volt volt, will be helpful helpful. Motors vary in their kV rating, rating 

depending on size, number of windings, poles, etc. 

How do we vary the amount of electricity which passes into the motor? The best control 

would allow everything from the motor not turning over at all to a full-throttle, full power 

run. An electronic speed controller (ESC) enables this, with some limitations, usually at 

lower RPMs. 

An ESC works as a switch, using g high-speed g p MOSFETs ( (metal oxide semiconducting g field 

effect transistors) to switch the current on and off. The motor receives only pulses of 

electricity that are allowed through by the controller as the MOSFETS turn on and off. The 

power received by the motor is based on how “wide” the pulse is, 


10

“The servo signal is a simple digital pulse. It spends most of its time at a logic low (0 V). 

Ab About t every 20mS 20 S it goes logic l i high hi h (3 t to 6 VDC) and d then th quickly i kl goes low l again. i It i is thi this 

tiny window of logic high time, called the pulse width, that gets the attention of the servo. 

Please refer to the drawing. The period labeled "A" is called the frame rate. In the example 

it is repeated every 20mS (50 times per second), which is quite typical for most radio 

systems. 

Modern servos define center as a 1.5mS pulse width, as shown by detail "B" in the drawing. 

Full servo rotation to one side would require that this pulse width be reduced to 1.0mS. 

Full rotation to the other side would require the pulse width to increase to 22.0mS. 0mS Any 

pulse width value between 1.0mS and 2.0mS creates a proportional servo wheel position 

within the two extremes. The frame rate does not need to change and is usually kept 

constant. 

The servo will not move to its final destination with just one pulse. The servo amp 

designers had brilliantly considered that multiple pulses should be used to complete the 

journey. This little trick reduces servo motor current draw and it helps minimize erratic 

behavior when an occasional corrupt signal is received. To move the servo, you must 

repeat the h pulse l every few f milliseconds, illi d at the h chosen h f frame rate. Md Modern R/C systems use 

a 40Hz - 60Hz frame rate, but the exact timing is not critical. If your frame rate is too slow, 

your servo's movement will become rough. If the rate is too fast the servo may become 

very confused.” 

http://www.rc-cam.com/servotst.htm 


11

Components vary in quality and price. For purposes of this paper and presentation, I’ve 

decided to stay with equipment that has demonstrated reliability, is made in America or 

Europe (there are myriad inexpensive Chinese components, but anecdotal evidence 

suggests lack of reliability and product support for many such motors and controllers – 

although that situation is improving). 

Drawing from Hyperion Motors 


12

Inrunners tend to be more efficient than outrunners, but turn at incredibly high RPMs, 

requiring the use of a gearbox to reduce propeller speed to required levels. Even with the 

6.7 gearbox on this NeuMotor, further reduction would be required. At 70,000 rpm, the 

output shaft would still turn over at 10,447 rpm! 

Luckily, the planetary gearbox, made by Maxon, allows stacking a second (or third) 

gearbox, further increasing torque, allowing a larger propeller, and reducing propeller 

speed. A second gearbox on this unit would reduce propeller speed to 1,560 RPM, in a 

desirable range g for ultralight g use. For some of the larger g NeuMotors, which turn over at 

only (!) 30,000 rpm, the speed of the propeller could be proportionally slower. 

http://www.neumotors.com/Site/Welcome.html 

http://www.castlecreations.com/products/neumotors/nm.html 


13

Another inrunner manufacturer, Bob Boucher at Astro-Flight has been involved with solarpowered 

aircraft such as the Solar Challenger, and pioneered the use of cobalt and other 

special metals in his motors. 

He has been involved in the development of the motor Greg Cole is using on the 

Sparrowhawk, and the 50kW unit currently being tested on the Monnet Sonerai electric 

project. 

http://www.astroflight.com/ 


14

Plettenberg has an interesting spinner that completely surrounds the motor, and provides a 

central hole that cools the motor, a bit like Kurt Tank’s original design for the FW-190. A 

recent addition is the use of a thrust vectoring servo, similar to what is installed on the A-I- 

R Atos using Dr. Eck’s motor. 

Although the Extra is probably too small for the use intended in this presentation, there is 

the possibility of using two in wing-mounted pusher configuration on something like a 

Mitchell Wing or Swift. A similar spinner is available for the Terminator and Predator, 

allowing g similar configurations g with up to 15 hp. 

http://www.plettenberg-motoren.com/UK/index.htm 


15

This chart of representative available motors gives some idea of those which fit into the 

lower range of our survey. Note that peak power is never to be held for more than two 

minutes with most of these motors (30 seconds for NeuMotors), and that most limit 

continuous power to half their peak output. 


16

The DMSV (Deutscher Motorschirm Verbuch e. V. – the German Paramotor Association) 

gave the first type test certificate for a motor, MP number DMSV-MS-5019-09, to the 

company LFG [boron man]. The drive unit developed by LFG [boron man] as well as 

Wolfgang Zankl and the company PAP brought to the production stage one of German Dr. 

Ing. Werner [Eck’s] developed brushless external runner engine HPDirect 10, which is 

integrated into the cage of the PAP 1400. The unit is very light, but produces 55 kg (121 

pounds) of thrust with a three-bladed propeller on the PAP paramotor. 

(The above is a rough g translation of the very y rough g translation afforded by y Babelfish.) 


17

Schulze controllers are recognized as high-quality, high-end units for serious modelers. 

The unit shown cost over 400 Euros, or about $520. Its light weight is essential in models, 

and builders of “real” aircraft may want to consider a more robust controller with even 

more power handling capabilities. Despite that consideration, the Werner Eck motor uses 

a similar Czech or German controller in its many applications on human-carrying 

ultralight aircraft. 

http://www.schulze-elektronik-gmbh.com/index_uk.htm 


18

Installed on the PAP1400 powered parachute frame, the HPDirect 10 swings a large Helix 

propeller for greater thrust. 

In the Swift rigid-wing hang glider, the unit and associated batteries and controller are 

neatly streamlined, allowing Manfred Ruhmer to note that flight characteristics are not 

noticeably different from those of the pure glider version. 

“When I heard of this motor, my interest was aroused immediately. With a weight of 3.75 

kg and a number of revolutions of 2,000 [RPM] he is to be propelled in the position large 

propellers directly. He puts a continuous duty of 8 kW and a short time achievement of 

over 10 kW problem-free away. As automatic controller… a Czech Jeti Spin 200 is used. 

This automatic controller is able to carry out with good cooling, 200 [Amps]. The tension 

(voltage) can amount to up to 60 V. 

The unit uses battery packs arranged in a sixteen batteries in series, 9 in parallel 

configuration for 144 cells (A123, LiFePO4). Weighing 12.5 kg. This gives 58 Volts and 20.7 

Amp hours. Total added weight on the Swift is 20-22 kg, causing a slight increase in 

gliding speed and sink rate rate. 

http://www.geigerengineering.de/avionik/produkte/ 

http://www.swift-light.at/ 


19

The A-I-R Mosquito, fitted with the HPDirect 10 with a direct drive to a folding propeller, 

and Saft lithium polymer polymer batteries gives approximately 10 minutes of running 

time, enough for an 800 meter climb. Toni Roth notes that the system is not any heaver 

than a backpack unit with a conventional two-stroke engine. 

There is some indication that the unit has the possibility of vectored thrust, as indicated in 

the following: 

“For … Atos we developed and [built] an electronically steered introduction tail unit, 

integrated cockpit control members and intelligent servo mechanisms also here automation 

and avionics for more efficiency and the correct flight feeling.” 

http://www.a-i-r-usa.com/index.asp?ID=4243 


http://www.a-i-r.de/index.php 

20

This simple operational drawing of a brushed motor’s operation shows the mechanical 

commutation required to control the motor’s rotation and speed. Mechanical brushed 

commutation leads to the brushed motor’s biggest drawbacks, inefficiencies caused by the 

mechanical nature of the system, and wear that requires frequent maintenance. 

Despite those drawbacks, the most common motors on practical ultralights and light 

aircraft at this time are brushed motors, mostly Lynch models, but also Perms and those 

specially built by their creators. 


21

This diagram, based on the control drawing in the APAME literature, shows the simplicity 

of the basic motor/controller configuration, in this case for a brushed motor. 

Note the monitoring of current between the battery and controller and the controller and 

motor, and the voltage for the battery and motor. Fusing is provided at several crucial 

points to prevent damage to components, although failures here would probably bring 

down an aircraft. 

http://www.apame.eu/AA%20welcome.html 


22

This cutaway of a Lynch Motor shows the compact nature of the design, which has an axial 

gap arrangement between the coil on the stator and the magnets on the rotor. Lynch 

motors have excellent power-to-weight ratios, and can be controlled by brushed or 

brushless controllers. 

http://www.lemcoltd.com/ 


23

Electravia, following the successful testing of a Lynch motor and 47kg battery pack on their 

Souricette ultralight, installed the motor on an Alatus AM-12 motorglider. The superior 

aerodynamics of the motorglider (27:1 lift to drag ratio) allowed over an hour’s flight on a 

battery pack half the weight of that on the ultralight. 

Electravia has also flown a trike on this power system, and an ultralight Souricette. The 

Souricette, although it uses the same motor as the Alatus, is a far “draggier”, heavier 

machine, and requires a battery pack double the size of that in the Alatus for less duration. 

The Alatus managed g 1 hour, seven minutes on its 20 kg g battery, y the Souricette 48 minutes 

on its larger pack. 

http://www.electravia.fr/ANGLAIS/Aindex.html 


24

Randall Fishman won best new design at the 2007 EAA Air Adventure for his adaptation of 

the Monnet Moni motorglider with an electric motor and controller of his own design. 

The motor puts out 18hp at full power, but Fishman flies it at about 33-percent power, 

enabling level flight at 60 mph at .7C battery drain, and with very little elevation of battery 

or motor temperatures. 

http://www.electraflyer.com/ 


25

One customer of Fishman’s, Jerry Booker, a farmer and airplane designer in southern 

Illinois, has mounted his motor on a retractable arm on his Red Tail Hawk motorglider, 

and is nearing flight testing. He uses the same motor, controller and battery pack as that 

on Fishman’s Moni, but should have slightly greater endurance because of the lower span 

loading of his aircraft. 

A reader of his RTH Yahoo Group, Paul F. Ralph, has designed a 33:1 motorglider, the 

Mew Gull, and has done a series of estimates for power required with a similar electric 

motor. He has also created a battery/fuel y chart that is helpful in analyzing y g weight g and 

expected duration for different power-pack configurations. 

http://groups.yahoo.com/group/RedTailHawkUltralightSailplane/ 


26

Mark Brierle pulled into Tehachapi, California’s Mountain Valley Airport last Labor Day 

towing his UltraGull 2000 with a Perm 132 motor and Kelly controller mounted where the 

two-stroke Rotax or HKS would normally be. 

He has flown this craft within the last few months, and reports breaking ground in 55 feet, 

climbing at 270 feet per minute, and being able to stay aloft for 11 minutes on a small 

lithium battery pack. He reports running at 4.5kW at 55 mph. 

http://www.thundergull.com/ 

. 


27

Ken Krueger, engineer for Van’s Aircraft, asked the Lynch Motor Company for assistance 

in selecting a motor or motors that could power a new, possibly kit-built design for the 

company. His specifications called for a motor that could produce full power for five to six 

minutes and up to 50-percent power for at least an hour. 

http://www.vansaircraft.com/ 


28

APAME and ACV are now working on the two craft shown. The single seat Electro on the 

right will use a 26 hp Lynch motor while the Duo flying wing will use a 43 hp Lynch unit 

with belt reduction. 

http://www.electravia.fr/ANGLAIS/Aproducts.html 


29

At a greatly oversimplified level, brushless electric motors are controlled through two 

different means, use of a trapezoidal wave form, or the digitized equivalent of a sinusoidal 

wave form. 

The trapezoidal form causes greater motor noise in operation, and less smoothness of 

running than the sinusoidal form. It is simpler, however, and is resistant to harmonics 

problems that the sinusoidal motor control can experience. Only one motor in this survey 

uses this wave pattern – the Yuneec motor from China, used on paramotors and an 

anticipated twin-motor ultralight g aircraft. 

All other motors use a sinusoidal wave form, with different design approaches to read the 

back emf or sense Hall effect sensors to determine the rotor position and synchronize the 

triggering of, usually, MOSFETs to energize the coils in the motor. 


30

Patrick McLaughlin of Mountain High Oxygen in Redmond, Oregon, is developing a range 

of controllers independently from other motor projects. He wants to provide a range from 

20kW to at least 90kW, and further. These units can be used as servo or stepper controllers 

if desired. 

http://www.mountainhighoxygen.com/ 


31

Yuneec, a Chinese company making products imported by Englishman Clive Coote, bases 

its powered parachute motor on a large outrunner type design. The firm claims 10kW for 

this motor and is introducing a larger, 12.5 kW unit. 

With its 66.6 Volt, 30 Ah battery pack, Yuneec claims 25-30 minutes flight time, a good 

accomplishment considering the high drag inherent in paragliders. It will be interesting to 

see the run times achieved with two motors on the projected ultralight airplane Yuneec is 

developing. 

The motor is part of a package that includes a battery management system, controller (the 

only one in this presentation running a trapezoidal input to the motor), charger, and a 

hand-held control interface with an LCD screen and a stick shaker to indicate a low battery 

charge. 

http://yuneeccouk.site.securepod.com/paramotor_Tech%20Spec.html 


32

KLD Energy Technologies, located in Austin, Texas is developing a wheel-hub motor that 

provides over 55 mph top speed and 0-50 times of 10 seconds for an electric scooter that 

will be mass produced in Vietnam. 

Company literate promotes the high frequency nature of the motor, running at 2,500 Hertz, 

as a result of nano-crystalline materials that replace traditional iron cores. Such 

“amorphous” materials are being used to promote cooler running and lower saturation 

losses. 

http://www.kldenergy.com/ 

http://www.kldenergy.com/Articles/090419CNNCoverage.pdf 


33

Light Engineering Motors have amorphous metal and permanent magnets as part of their 

design, and produce significant torque. Their controllers feature redundant hall sensors 

and high resolution encoders. 

http://www.lightengineering.com/ 


34

Apex Drive Laboratories uses a dual stator-single rotor design, with U-shaped core. The 

dual permanent magnets on the rotor and the patented U-shaped core help produce high 

torque at low RPM. A dedicated controller can use Hall-effect commutation for high 

torque at low speed, or sensorless control for high-speed systems. 

Their DD31w motor weighs 84 pounds and puts out a peak of 46 kW, or 61.7 hp and a 

continuous output of 31.3 kW, or 46 hp. Its peak torque is of interest, though. With 576 

Nm (425 ft-lbs) peak and 157 Nm (117 ft-lbs) continuous, the motor produces this at 

relatively y low RPMs. 

Recently, the company recently received a $250,000 commercialization grant from the 

Oregon Nanoscience and Microtechnology Institute (ONAMI) for its patented microchannel 

liquid cooling approach. 

http://www.apexdrivelabs.com/ 


35

Roman Susnik was instrumental in the design of the motor used on the Pipistrel Taurus, a 

two-seat self-launching sailplane. He has developed a line of 20-, 30-, and 40-kW motors 

which are large outrunners in concept. He has also developed controllers specifically for 

these motors. 

http://www.sineton.com/www/ 

http://www.glider-one.si/index.php?option=com_content&task=view&id=58&Itemid=87 


36

“The controller can commutate the motor in two different ways: using Hall effect sensors to 

determine the magnet core’s position in relation to the coils, or using the motor’s back-EMF 

to sense rotor position, eliminating the need for Hall sensors. The AeroConversions 

controller will initially employ a Hall effect sensor-equipped motor, but back-EMF 

controlling will also be explored to potentially further simplify the AeroConversions motor 

design. The AeroConversions controller will also provide in-cockpit monitoring of battery 

power levels to the pilot.” 

http://www.aeroconversions.com/e-flight/ g 


37

Part of ENFICA-FC (Environmentally Friendly Inter-City Aircraft – Fuel Cell) project at the 

University of Turin, and headed by Professor Ing. Gulio Romeo, the Skyspark project uses 

a Sicme Motori Valentino motor of 65 kW maximum output in a light wood airframe, the 

Pioneer 300. The goal is to set a speed record for electric aircraft, first with battery power, 

and second with fuel cells as the storage medium. 

The project has an aggressive schedule, with the first proposal in late 2005, and a complete 

airframe, motor, controller, batteries, fuel cells and hydrogen storage tanks being displayed 

in February y 2009. The plan is to stage g a flight g test in the late spring g or early y summer with 

batteries, establish a speed record (180 km/hr) and then, in the fall, attempt to achieve a 

speed record on fuel cells only. 

http://pdf.aiaa.org/preview/CDReadyMATIO07_1768/PV2007_7754.pdf 


http://www.enfica-fc.polito.it/en 

38

“Sicme Motori, technological partner of SkySpark, is producing the Valentino engine, 

which will be propelling the aircraft. This prototype, which stems out of the cooperation 

with the Electrical Engineering Department of the Polytechnic of Torino, is very light and 

has a high performance: it only weights 25 kg and features a maximum power of 65 kW at 

a speed of only 2500 rpm. 

“Valentino is the crowning jewel of 45 years of industrial experience focused on research 

and innovation. “Sicme Motori is one of the first companies on the international scene to 

apply y Direct-Drive technology gy to electrical engines” g states Alberto Sola, Chairman of 

Sicme. “This has allowed us to do without the gearbox, guaranteeing a maximum energetic 

efficiency”. Gearless motors reduce maintenance needs enormously, have remarkable 

environmental advantages, guarantee outstanding performance and absence of noise, even 

at low power regimes. 

“Valentino is a Direct-Drive motor (synchronous, with permanent magnets) of a brushless 

kind. This means that, in contrast with a brush motor, it does not need electronic switches 

embedded on the main rotor in order to work. It uses particularly p y sophisticated p materials, , 

has an external rotor, and is cooled by liquid. 

“Always active in the field of innovation, Sicme Motori has been one of the first companies 

to invest in renewable energies. ‘We have been busy with wind power since 2002, well 

before it became a media hype’ says Alberto Sola, ‘and we are now working on a new 

generation of electrical engines that will find concrete applications in many important 

sectors, such as the automobile, to realize highly performing ecological engines’. “ 


From a SkySpark press release 

October 20, 2008 

39

The E-Silence aerobatic has nothing of note I can find at this point that is not on the slide. 


40

Combining a Rotax 914 with a motor that can be used with the engine at takeoff, or by itself 

in case of an engine failure, this hybrid is a first of its kind in the light airplane realm. 


41

Flight Design and Rotax collaborated to produce this motor for this year’s Aero 2009 E- 

Fli Flight ht Expo. E It i is iinstalled t ll d on a CTS light li ht sport t aircraft. i ft 

“Flight Design GmbH, the German creators of the popular CT line of light sport aircraft, 

used AERO Friedrichshafen to announce details of their work on a new hybrid engine 

concept. The propulsion package consists of a standard Rotax 914 turbocharged engine to 

which is mated a 40-hp (30 kW) electric motor. The electric motor is coupled to the 

propeller hub using a poly-V-belt drive that has no overloading impact on the crankshaft 

and, thus, allows the motor to transmit its power directly to the point where it's needed. 

Since the basic Rotax is left mostly y untouched, its 130-hp poutput, p combined with the electric 

motor's 40 hp, provide for a combined 170-hp output for the hybrid. The electric motor will 

be used for takeoffs and climbs, and makes use of its full capacity over a maximum fiveminute 

span. In cruise, power comes entirely from running the gas engine at full power. 

Twenty minutes is required for a full recharge on the 25 kilos of lithium ion batteries that 

power the electric motor. 

“One of the features being touted by Flight Design is the added safety inherent with a 

hybrid. Should there be a failure of the combustion engine, power from the electric motor 

can supplant a stopped engine and provide sufficient thrust to stretch the aircraft aircraft's s glide to 

an emergency landing. Flight Design expects to begin flight testing of its hybrid in one of 

its existing aircraft by the middle of 2009.” 


http://www.avweb.com/avwebflash/news/FlightDesignHybridAero_200078-1.html 

42

This motor is promising because of its Oxford roots, being designed by graduate students 

with the intended purpose of selling rights to private manufacturers. Its high power to 

weight ratio is interesting enough, but further modeling, based on the same factors that led 

to the demonstrated output shown, suggests that at higher revs, the motor could put out 

up to 150 kW. 

http://www.scienceoxfordnetworks.com/news-publications-news-articles/oxfordelectric-motor-set-for-track-tests 


http://www.isis-innovation.com/licensing/3056.html 

http://www.isis innovation.com/licensing/3056.html 

43

Alan Cocconi has built up AC Motors with his highly original solutions to myriad 

quandaries in electric motors and drives. No longer at the helm of that organization, he is 

devoting his time to a project called Skybase, a surveillance system using seven separate 

solar-powered aircraft that will hook up in flight to form a 280-foot wingspan, sevenmotored 

stratosphere cruiser. 

Each of the seven individual aircraft will use the motor he originally designed for the Solar 

Impulse project, putting out a maximum 15 kW at takeoff, but slowing to produce 1.5 kW 

each at cruise. This 10:1 output ratio allows endless cruising, g with solar panels producing g 

power during the day, and charging a battery array in each plane for power through the 

night. He is not in favor of using fuel cells for this mission as they require heating to 

prevent freezing in the low temperatures at high altitudes, and relies instead on batteries in 

a central cluster in each airplane. Alan says that batteries provide 90-percent cycle 

efficiency. 

His ironless construction reduces inductance losses and allows generation of smooth 

currents at low speeds. p The motors will turn over at only y 800 RPM maximum. 

http://solar-flight.com/solong/index.html 

http://www.engineering.columbia.edu/news/archive/engnews_s98/cocconi.html 


http://www.designnews.com/article/3158-The_Quest_for_Perpetual_Flight.php 

44

One must consider the total cost of batteries, including anticipated cycle life, to fully 

calculate the cost of powering electric aircraft. 

NiMH and NiCad batteries may be less expensive than lithium ion or lithium polymer, for 

instance, but three times as many are needed for an equivalent voltage. 

LiFePO4 batteries may have slightly lower voltages than straight lithium units, but 

promise more useful cycles. Any of this may be moot, because there may be a straight 

lifetime of three years for lithium batteries, regardless of their use. 

A new battery from Toshiba, Toshiba the Supercharged Ion Battery Battery, or SCIB, SCIB claims a life of 6,000 6 000 

cycles. Its cost is unknown because Toshiba is releasing it only to OEMs, and its only 

current use is on the Schwinn Tailwind bicycle. 


45

Tokyo Institute of Technology students, with a grant from Panasonic, used 160 AA 

Oxyhydride cells to power a small motor on their adapted HPA, driving the plane to about 

5 meters height and 400 meters distance. 

Calculating a sale price of $5.00 per 4-pack, 160 cells would cost $200. 

400 meters = 1,328 feet, or a quarter mile. 

Flying 1 mile on this aircraft would cost $800. 

http://panasonic.co.jp/corp/news/official.data/data.dir/en060718-3/en060718-3.html 


46

From the University of London Press Release:. 

“Master Master of Engineering (4th year) ear) project students ha have e modified an aircraft to fly fl on 

electric power, in association with Anglia Sailplanes and AeroElvira Ltd. 

“The first flights took place on 20/21 September. Test pilot, Derek Piggott, described the 

modified aircraft as a "delight to handle". 

“The aircraft was modified by the addition of 8 underwing pylons attached by removable 

straps. The pylons were fitted with 16 propellers (280 mm in diameter) driven by electric 

motors and powered by lithium-ion batteries supplied by Ripmax PLC. The motors were 

activated by a wireless link by the pilot in the cockpit. A permit-to-fly was issued by the 

British Gliding Association 

Association. 

“The project involved over 3 MEng Project groups over a period of 5 years, including for 

example the following students (now all graduates): Ross Shepherd, Stefan Wurwal, Mark 

Saunders, Hamza Baker, Mikel Alonso, Morten Christiansen, Sami Ghamloush, Mehrtash 

Lotfian, Mohammad Ali Sarkandi, Junaed Wahid.” 

News date: 24 September 2008 

Graupner p 900’s cost $ $60 each, , so the motor cost was $ $960. 

. 


http://www.pprune.org/aviation-history-nostalgia/343843-edgley-ea-9-optimist.html 

http://www.qmul.ac.uk/news/newsrelease.php?news_id=1122 

47

I’ve chosen to show the classic Pietenpol because it has been the test bed for so many different 

engines. Originally designed for use with the Model “A” Ford engine, which weighed 244 

pounds with magneto, the “Piet” also carried the Ford’s radiator (21 pounds), a propeller 

weighing 15 pounds, water and oil. The total weight of the powerplant, ready to fly, was thus 

over 300 pounds. Consider a 43 hp Lynch Motor in place of the Ford, a five-pound controller, and 

up to 245 pounds of batteries, and one can see the potential. 

This may be an elusive dream with current technology, though. A takeoff run of 766 feet can get 

the Piet airborne, and establish a 350 feet-per-minute climb, assuming g an 85-percent efficient 

propeller and the Lynch motor. Weight allowance for batteries would allow about 16kWh, or 

only about one take-off and a half-hour of cruising before the $24,000 battery pack would be 

drained (not good for life cycles, either). A full-hour of cruising would require a lighter, more 

efficient battery and $40,000. This would make 1,000 cycles at $40.00 per flight (plus charging 

costs), not much better, in terms of cost, than a regular vintage light aircraft. 

Consider that Pennec and Lucas in France built their Dieselis as a modern homage to the 

Pietenpol, p , using ga modern Opel p diesel engine g in p place of the Model “A”, , and making, g, like the 

Pietenpol, a light wooden airframe, although far more aerodynamically clean. As a consequence, 

the Dieselis and its even cleaner outgrowth, the Gazaille, cruise at 90 mph on a little over one 

gallon of diesel fuel per hour. Both can cruise at 120 on two gallons per hour. Both could be 

capable, with refinement, of winning the CAFÉ 100 mph/100 mpg prize. 

Consider also that the weight capacity for power can be used for an efficient electric motor and 

controller, lightweight batteries, and the dream of a practical, two-seat light sport aircraft can be 

achieved. Consider also, that the electrification of classic aircraft could be realized, because of 

their heavy original powerplants. 


48

In a discussion with Alan Fishman, he claimed that his batteries will last for 1,000 

cycles if used carefully, as they have been in test flying. In cruise at 70 mph, the 

Moni’s batteries are being drained at 0.7C. His battery pack lists at $8,500, meaning 

that 1,000 flights (around an hour to an hour-and-a-half) would average about 

$8.50. Adding the cost of recharging to each flight, at .$0.52 per charge (central 

Florida utility rates) adds up to a direct and indirect battery charge of $9.02 per 

flight, or around $6.00 per hour if each charge does allow 1-1/2 hours duration. 

MMark k Brierle, B i l fl flying i at t a similar i il di discharge h rate t at t a slightly li htl slower l speed d i in hi his 

ultralight Gull 2000, should experience much the same battery life and costs, but 

with less range per charge because of his slower cruise speed. 


49

“Axel Lange, Chief Executive of Lange Aviation GmbH, said ‘We use Saft Li-ion 

batteries in this demanding application simply because we have found them to be the 

best on the market. The Antares demonstrator LF-20E flew on Ni-MH batteries and 

performed well. But the extra power available when we switched to the Saft Li-ion 

batteries has enabled us to more than double the launch height using a battery system 

that weighs 26 per cent less.’ 

Battery system 

“The Antares 20E is equipped with a custom-designed modular battery-system, utilizing 

Saft Sa t VL V 41 M Li-ion o ce cells, s, tthat at pack as much uc po power e as possible poss b e into to a lightweight g t e g t and a d 

space efficient package. The battery system weighs 80 kg, which is around 12 per cent of 

the sailplane’s typical launch weight (with pilot and ballast) of 660 kg. 

“The battery system is split into two packs positioned in the leading edges of both inner 

wings. Each pack consists of 36 cells in series, divided into 12 three-cell modules. 

Together, both battery packs provide an operating voltage of 212 V to 288 V, depending 

on the state of charge (SOC). The dedicated battery management system ensures each 

cell is carefully and redundantly monitored and controlled to ensure that it delivers 

maximum performance while remaining within its safe operational parameters parameters. 

“A full nine-hour charge from the onboard charger will deliver the Antares 20E 

approximately 3000 m above its launch point. It is also possible to use the available 

battery power for one or more takeoffs and powered climbs. Each extra takeoff costs 

approximately 100 m final climb altitude. Partial charges and discharges have no 

adverse impact on the battery life.” 


http://www.saftbatteries.com/SAFT/UploadedFiles/PressOffice/2009/CP http://www.saftbatteries.com/SAFT/UploadedFiles/PressOffice/2009/CP_2020- 09_en.pdf 

http://www.lange-aviation.com/ 

50

M My friend f i d and d mentor, t MMarshall h ll HHouston, t provided id d th the ffollowing ll i t to close l out t th the 

presentation, thus ending things as we started, with the prescience of Jules Verne. 

It reflects the optimism and faith in the future that Victorian writers often espoused. 

"And what will they burn instead of coal?" 

"Water," replied Harding. 

"Water!" cried Pencroft, "water as fuel for steamers and engines! water 

to heat water!" 

"Yes, but water decomposed into its primitive elements," replied Cyrus 

Harding, "and decomposed doubtless, by electricity, which will then have 

become a powerful and manageable force, for all great discoveries, by some 

inexplicable laws, appear to agree and become complete at the same time. 

Yes, my friends, I believe that water will one day be employed as fuel, 

that hydrogen and oxygen which constitute it, used singly or together, will 

furnish an inexhaustible source of heat and light, of an intensity of which 

coal is not capable. Some day the coalrooms of steamers and the tenders of 

locomotives oco ot ves w will, , instead stead o of coal, coa , be sto stored ed wwith t tthese ese two co condensed de sed 

gases, which will burn in the furnaces with enormous calorific power. There 

is, therefore, nothing to fear. As long as the earth is inhabited it will 

supply the wants of its inhabitants, and there will be no want of either 

light or heat as long as the productions of the vegetable, mineral or 

animal kingdoms do not fail us. I believe, then, that when the deposits of 

coal are exhausted we shall heat and warm ourselves with water. Water will 

be the coal of the future." 


The Mysterious Island Island, Jules Verne 

51

Thank you to Bruce Carmichael for getting me started in making these 

presentations, and Dr. Brien Seeley for inviting me to this Symposium. 

Special thanks to David Bettencourt, Patrick McLaughlin, Anne Lavrand, Roman 

Susnik, Michael Baker, Alan Cocconi, Steve Neu, Manfred Ruhmer, Bob Boucher, 

Otmar Ebenhech, Edwin Brekke, and Marshall Houston, for guiding my research 

and testing my conceptual understanding. 

This presentation is dedicated to the memory of Jocelyn Latka, my late 

granddaughter, who showed a courage and willingness to test the limits of her 

capabilities that has been an inspiration to her grandfather and would be to anyone. 


52

Electric Motors and Controllers for Use in ... - CAFE Foundation

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