Advantages of Electric Power

July 2010 39
It’s all about
by Bob Aberle
I WROTE AN article about electric-powered
flight, titled “Introduction to Electric Power,”
that was published in the July 2003 MA. You
can find that feature at the Web site address
that is included in the “Sources” list at the end
of this article.
Seven years later, electric-power
technology has changed tremendously.
Because of the technical advances that have
been made, “e-power,” as it is sometimes
called, now offers many more advantages than
ever!
With that in mind, I am presenting this
updated article. It is a basic introduction, to let
you know what is going on and what is
available in the realm of electrics.
As time goes on,
I plan on writing
more detailed
information that will enable
you to fully appreciate this
exciting form of model propulsion.
If you have thought about trying electric
power, please read on.
What Is Electric Power? It is a system that
operates a motor using electrical energy
stored in a battery, opposed to a fuel tank
feeding an engine. Electric power offers the
model aircraft enthusiast several basic and
important advantages, such as:
1. Quietness:Minimal noise is created
when the motor is operated. It is so quiet that
no mufflers are necessary. This major
advantage has helped aeromodelers obtain
flying fields; silent models will not annoy the
public!
Soundless flying capabilities have
contributed to the establishment of small
aircraft we refer to as “park flyers” or
“backyard flyers.” The inference is that these
models can be flown at local fields without
attracting attention. Public acceptance of
electric-powered models has led to the
development of the AMA’s Park Pilot
Program membership category.
2. Cleanliness: No residue is left on an
airplane after a flight. As a result, no special
finishes need to be applied to the aircraft.
Even more important is the fact that residual
fuel, or even spilled fuel, will not get into our
ground water and create serious ecological
problems in the future. This is another way
our hobby supports the “green” movement.
What Comprises an Electric Power System?
This means of propulsion basically includes a
motor (that turns the propeller), a speed
controller, or ESC, and a battery that provides
electrical energy to operate the motor.
The most efficient motors that modelers
use are the brushless types. These are
basically AC motors that do not require
brushes; therefore, they have nothing to wear
out or need replacing.
Motors are available in two categories:
“outrunner” and “inrunner.” The outrunner
type is the most popular. By design, it can
turn a propeller directly, without a
mechanical gear train.
The author hand-launches his electric FF model. These
power systems work well in all types of aircraft.
Advantages
Electric Power
of
electrons!
Photos by the author
The FMA Direct Cellpro Multi4 charger is
connected to a Li-Poly pack via a node
connector adapter. Different adapters are
available to fit various battery packs.
At the opposite end of the e-power
spectrum are models such as this Hellcat by
Joe Malinchak, a US Airways Captain and
MA “Micro-Flying” columnist. It can’t weigh
more than several grams (not even ounces)
and uses a magnetic actuator for rudder
control.
A basic electric model system has three major components: motor, ESC, and
battery. R-L: typical brushless outrunner and APC electric propeller, brushless
ESC, and Li-Poly pack.
In addition to Li-Poly, there are now several types
of Li-ion batteries. Such a pack that A123Systems
sells is on the right.
The popular Watt’s Up digital meter
stood out because of the excellent 35-
page user’s manual that is supplied
with it. It also stores the highest
readings while connected to a battery.
A great advantage of electric-powered
flight is ROW (rise-off-water) models on
floats. Going electric will give you peace
of mind, knowing that your aircraft
won’t suffer a stalled engine out on the
water.
These are the kinds of connectors you might
encounter when you get involved in electric
power. These devices allow you to unplug
everything for substitution and replacement
purposes.
One of the most important tools you will
need—to be able to fully enjoy and use
electric power for your models—is a device
that can read the most important motor
parameters: current (amperes), voltage, and
the product of the two, which is watts
(power).
The second thing you need is a meter—
preferably digital. Plan on spending probably
$50-$60 for one. There are several good ones
on the market, and all will do the same job.
I especially like the Watt’s Up wattmeter,
because the manufacturer, RC Electronics,
supplies a 35-page user’s manual that covers
all of the various applications for this
product. You can find the manual on the
company’s Web site.
There are numerous types of battery
chargers on the hobby market. Many are used
for a specific type or brand of battery.
My favorite is the FMA Direct Multi4,
because it can charge almost any battery
chemistry, packs with as many as four cells,
and up to 4 amps of current. FMA Direct also
sells a variety of node connector adapters that
will allow you to charge nearly any brand of
battery you can obtain.
Rather than spend several pages
describing all that the Multi4 can do, check
out the user’s manual, located on the FMA
Direct Web site. FMA Direct also sells the
Cellpro 10S charger, for those who need to
charge packs with as many as 10 cells at 10
amps.
Connectors are a vital part of electric
power systems. These connectors allow
y ou to plug toge ther all of the
co m po nents that make a f ull system.
Many of the individual components
come with connectors already installed.
Unfortunately not all do, so you might be
required to install your own. In some cases
you can do that with a mechanical crimping
tool, but you will usually need to solder the
connectors.
When you get down to the multipin node
connectors that allow you to balance-charge
battery packs, there is no industry standard
or convention. There are currently at least
six types of node connectors you might have
to deal with: PolyQuest, Thunder Power,
FMA Direct Revolution, Kokam, Horizon
Hobby (E-flite and ParkZone), and Great
Planes (ElectriFly). Most manufacturers sell
balanced charge adapters to satisfy these
connectors. MA
—Bob Aberle
[email protected]
Sources:
RC Electronics
(408) 705-1980
www.rc-cars-planes.com
Thunder Power
(702) 228-8883
www.thunderpowerrc.com
Horizon Hobby
(800) 338-4639
www.horizonhobby.com
Essential Tools for the Electric Modeler
40 MODEL AVIATION
07sig2_00MSTRPG.QXD 5/26/10 9:50 AM Page 40
July 2010 41
Electric-powered aircraft benefit from their power-to-weight
ratios and quick throttle responses, making them an excellent
choice for hovering and 3-D. Those maneuvers also require
the model to have extreme control-surface movement.
Bob Hunt, an international CL Precision Aerobatics champion, holds
his Genesis Extreme design. Power is an AXI 2826-10 brushless
outrunner motor, Castle Creations Phoenix-45 ESC, and Thunder
Power 4S2P Li-Poly pack. Bob flew this model in the 2006 World
Championships in Spain, which made him the first pilot to ever fly an
electric CL model at a World Champs.
Andrew Jesky took first place in F3A at the 2009 Nats
with this Krill Spark. It uses a Hacker brushless power
system and Thunder Power batteries.
Electrified jets are hugely popular and as capable as
those powered by turbines. E-power allows jets
constructed from foam, such as this SR-71, to be an
exciting, low-cost alternative for RC pilots.
There are many more advantages to using electric power for
models than the fact that it is quiet and clean. I mentioned those
attributes in the main text of this article, but following is a summary
of its other benefits.
• Improved motor efficiency by going brushless.
• Reduced system weight. Motors and batteries weigh less than
engines and their related components, making for lighter models.
• Longer motor run times. Batteries have become lighter in weight and
have more capacity.
• Faster battery recharging. This quickly gets your aircraft back into
the air.
• Safer operation.
• Improved linear throttle response for more precise model flight
control, especially with 3-D-type hovering maneuvers.
Electric-power enthusiasts enjoy several prominent events across
the country. It is common to see 300-500 registered electric-power
pilots and several thousand spectators at these gatherings.
The annual NEAT (Northeast Electric Aircraft Technology) Fair in
upstate New York, held every September, is one of the largest
electric-flight gatherings. The big SEFF (Southeast Electric Flight
Festival) in the Atlanta, Georgia, area is held every May. For micro
and indoor electric-power aeromodelers, there is the new KIEF
(Keystone Indoor Electric Fly), which takes place each October in
Muncy, Pennsylvania.
These are just a few of the fly-ins on the schedule. More are being
added each year. MA
—Bob Aberle
[email protected]
Electric Events:
NEAT Fair
www.neatfair.org
SEFF
http://seff2010.com
KIEF
www.pafunfly.com
Where Are Electrics Today?
This 68-inch-wingspan E-flite Beaver was designed
from the ground up to be electric. It can be flown
with a brushless motor that is equivalent to
a .25 or .32 glow engine.
National Electric Fly-In (NEFI)
www.modelaircraft.org/events/
NEFI.aspx
Arizona Electric Festival (AEF)
www.azmodelaviators.com
07sig2_00MSTRPG.QXD 5/26/10 9:53 AM Page 41
42 MODEL AVIATION
Dave Baron with his scale, multimotor
Boeing B-17 that features a retract landing
gear system. He has been performing demo
flights with this model at the NEAT Fair
for many years. Dave recently updated
the B-17 with brushless motors and
Li-Poly batteries.
Darrell Sprayberry builds and competes with RC electric
Scale helicopters. This one, detailed as one
flown by the Georgia State Police,
weighs 37 pounds and uses an
AXI motor for power.
References for Electric Power
MA
(765) 287-1256
www.modelaircraft.org/mag
Park Pilot
(765) 287-1256
www.theparkpilot.org
Model Aviation’s Sport Aviator
www.masportaviator.com
Flying Models
(888) 526-5365
www.flying-models.com
RC Micro World
www.cloud9rc.com
AMA’s Forum
www.modelaircraft.org/forums/default.aspx
WattFlyer
www.wattflyer.com/forums
The E Zone
www.ezonemag.com/pages
RCGroups
www.rcgroups.com/forums/index.php
RC Universe (Select “Electric Flight.”)
www.rcuniverse.com
Everything You Wanted To Know About Electric Powered Flight:
www.tcws.org/aeajr_eflight_ebook.pdf
Barnes & Noble
(800) 843-2665
www.barnesandnoble.com
RCAdvisor.com
(505) 206-1569
www.rcadvisor.com
AMA retail store
(765) 287-1256
www.modelaircraft.org/shopama
The World of Indoor/Micro Radio Controlled Model Aircraft
(all electric) By Bob Aberle on CD. Web site: www.cloud
9rc.com.
Several print and online magazines cater to the electric-powered
aeromodeler. Following are a few to which you can refer.
• MA features five columns that contain information about electrics:
“Electrics” by Greg Gimlick, “The Battery Clinic” by Red Scholefield,
“Small-Field Flying” by Paul Bradley, “Micro-Flying” by Joe Malinchak,
and “Frequently Asked Questions,” which I write.
My column is not exclusive to electric power, but it includes many
inquiries about the topic. Feel free to e-mail or write to any of us
columnists with your questions. MA also publishes reviews and articles
about electric power or featuring product reviews.
Each month MA publishes product reviews and articles about electric
power products.
• Park Pilot magazine continually publishes product reviews and articles
that feature electric power.
• Model Aviation’s Sport Aviator online magazine contains loads of reviews
and feature articles about electric-powered aircraft and electric power.
• Flying Models magazine has a column titled “Electric Flight,” which
Don Belfort and Stew Meyers alternate writing each month.
• RC Micro World Online Magazine is for micro and indoor electricpower
fliers.
Hobby forums provide an excellent opportunity to ask questions and
receive answers. Not all those who respond to inquiries are experts, but
their replies can still prove to be helpful.
There are five forums that I use and recommend.
• AMA’s Forum
• Watt Flyer
• The E Zone
• RCGroups
• RC Universe
Following are some good books about using electric power in our
models.
• Everything You Wanted To Know About Electric Powered Flight is an
online “E-Book” by Ed Anderson. You can find it on the Tri-County
Wing Snappers Web site; the address is in the “Sources” list.
• How to Build and Fly Electric Model Aircraft is by Robert Schleicher.
You can find it at Barnes & Noble.
• RCadvisor’s Modi-Fly by Carlos Reyes takes you through designing and
building an electric-powered model from scratch—in one day. It is
available from RCadvisor.com.
• Getting Started in Backyard Flying is a book that I wrote. You can get it
from AMA Headquarters’ retail store.
• The World of Indoor/Micro Radio Controlled Model Aircraft (all
electric) is another book that I wrote, available on CD. It’s available from
RC Micro World. MA
—Bob Aberle
[email protected]
07sig2_00MSTRPG.QXD 5/26/10 9:56 AM Page 42
Unlike fueled engines, which are
categorized by cu. in. displacement, motors
are generally rated by input power measured
in watts. If you multiply the motor current
(in amperes) by the voltage applied from the
battery, you obtain the wattage, or the power
input.
To size a motor, use the parameter called
“power loading”; it relates power input
(watts) to the total weight of an aircraft. The
resulting watts-per-pound figure is the key
to determining the correct-size motor for
your model. Later you will find many
references to this all-important parameter.
It is important to know that when dealing
with electric flight, each motor can provide a
broad range of power. The size, weight, and
armature windings are one consideration.
The choice of propeller size is a second.
Voltage applied to the motor is a third.
Coordinating those three variables is the
secret to enjoying all of the advantages of
electric-powered flight.
The ESC is inserted between the motor
and the battery. It essentially takes the place
of the servo that would control the
carburetor of a fueled engine. The servo
cable that exits every ESC is plugged into
the throttle port (connector) on your RC
receiver.
Moving the throttle-channel control stick
on an RC transmitter will turn a motor on or
off and provide variable speeds from idle to
full power. Besides the servo cable, there is
a three-wire cable that goes to the brushless
motor and a two-wire cable that goes to the
battery pack.
Modern ESC technology includes some
sophisticated electronics that provides, by
itself, many advantages for electric flight. A
modeler can program most of today’s ESCs
for specific operations, such as the direction
of the motor rotation.
An ESC will also prevent a motor from
starting, unless the transmitter throttle stick
is at the dead low or idle position. This
eliminates any chance of a motor
accidentally starting and causing an injury.
An ESC will shut down the motor when
a preset voltage level is reached. This is
necessary, because Li-Poly batteries can be
permanently damaged if the voltage drops to
a certain level. And if any kind of
interference hits your RC system, the motor
will be shut down as a warning that you had
best land your model in a hurry.
A unique feature of most ESCs is the
battery eliminator circuit, or BEC. This
enables your motor battery to also provide
power to your RC system. By doing this,
only one battery pack is required on your
aircraft. Although this BEC feature had its
limits years ago (such as current demands
and voltage), most airplanes today, except
for the very large models, can be flown off
of a BEC on a single battery pack.
Currently, the most popular battery for
electric-powered flight is the Lithium
Polymer type, or “Li-Poly.” This technology
emerged in our hobby approximately seven
years ago and completely changed the way
we fly electric models.
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These batteries offer much more
capacity and are available in packages that
weigh much less than the older Ni-Cd and
NiMH batteries. And because of the
popularity of Li-Polys, their prices have
come way down in recent times.
Li-Poly battery cells have a
characteristic voltage of 4.20 when fully
charged. They should be recharged at a 1C
rate, which can take as long as an hour;
that depends on the state of charge at the
time the charging started.
Improved Li-Poly cells that have
recently been released are capable of
charging at 2C rates in 30 minutes and 3C
rates in 20 minutes. Another characteristic
of Li-Polys is that they should not be
discharged lower than roughly 3.0 volts
(per cell).
Early on it was determined that Li-Poly
batteries, contained in packs of two or
more cells, needed to be balanced. This
simply means that every cell in the pack
should have the same voltage at full
charge.
To make that happen, battery packs are
assembled in such a way that each cell can
be separately charged and monitored. This
requires a special connector that is
attached to every Li-Poly battery pack
containing two or more cells.
The multipin connectors are referred to
07sig2_00MSTRPG.QXD 5/26/10 9:59 AM Page 43
44 MODEL AVIATION
as “node connectors.” Modern battery
chargers provide the necessary interface with
the various node connectors used throughout
our hobby.
Besides Li-Poly, popular battery chemistry
involves Lithium-ion, or Li-ion, technology.
These batteries are referred to by several
names, but the most common cells and packs
are produced by A123Systems.
I urge you to read the three-part article
titled “Those Things We Call Batteries,”
which you can find on Model Aviation’s Sport
Aviator Web site. The address is in the
“Sources” list.
And to learn more, you can read MA’s
popular bimonthly “The Battery Clinic”
column. It is written by Red Scholefield, who
is a noted battery expert.
Most SIGs in our hobby are using electric
power. It has been integrated into almost all
aspects of aeromodeling, including trainers,
sport fliers, park flyers, standoff-scale, Scale
(national and international), Aerobatics
(national and international), 3-D (hovering and
demonstrations), sailplanes, Old-Timers, FF,
micro and indoor flyers, CL (national and
international), vintage RC, helicopters, and
giant scale.
The AMA Nats that traditionally runs the
entire month of July at AMA Headquarters in
Muncie, Indiana, now has many competitors
who use electric power. This is especially true
with CL, Scale, Aerobatics, and helicopters.
Further advancing the growing popularity
of electric power is the fact that so many
hobby manufacturers are now offering ARF
and RTF models. Many of them arrive with
the motor, ESC, and batteries installed at the
factory. And there are numerous fueled aircraft
that can be converted to electric power.
This increased popularity has resulted in
considerable component price reductions that
make electrics affordable. That popularity has
also expanded the market, and the result is that
aeromodelers have more choices of motors,
ESCs, and batteries.
Today’s electric power systems for models
are probably easier to operate than fueled
engines. Ample information is available about
electrics, and you can get all the details you
need to be able to assemble, install, and
operate your own system.
The “Sources” list includes several key
manufacturers in the electric-power market.
You can obtain products and advice from
them.
You don’t need an electrical engineering
degree to enjoy all the advantages of
electrics. Yes, you will have to learn to
solder. But as time passes, the
manufacturers might do much of that type
of work for you.
Battery care and feeding is also
benefiting from better products and more
sophisticated chargers that automatically do
practically everything for you. With so
many people into electrics now, you might
find plenty of aeromodelers to answer
questions as you learn.
Sizing electric power systems to fit your
models is probably the most important
aspect of this type of flight and will require
you to learn several things. Recognizing
that this might prevent some modelers from
getting into electrics, I decided to write an
article about the subject.
The two-part feature is posted on the Sport
Aviator Web site, and you can find it at the
address in the “Sources” listing. This piece
covers all aspects of the watts-per-pound
parameter that is the key to motor selection.
Make sure you read every word. MA
Bob Aberle
[email protected]
Sources:
“Introduction to Electric Power”
www.modelaircraft.org/mag/FTGU/Part5/5m
ain.html
A123Systems
(617) 778-5700
www.a123systems.com
“Those Things We Call Batteries”
Part One:
www.masportaviator.com/ah.asp?CatID=2&I
D=146
Part Two:
www.masportaviator.com/ah.asp?CatID=2&I
D=149
Part Three:
www.masportaviator.com/ah.asp?CatID=2&I
D=164&index=0
“Selecting Electrical Power Systems”
Part One:
www.masportaviator.com/ah.asp?CatID=2&I
D=76
Part Two:
www.masportaviator.com/ah.asp?CatID=2&I
D=77
BSD Micro RC
(417) 358-9521
www.bsdmicrorc.com
BP Hobbies
(732) 287-3933
www.bphobbies.com
Castle Creations
(913) 390-6939
www.castlecreations.com
FMA Direct
(800) 343-2934
www.fmadirect.com
Great Planes (ElectriFly)
(800) 637-7660
www.greatplanes.com
Hitec RCD/Multiplex USA
(858) 748-8440
www.hitecrcd.com
www.multiplexusa.com
Hobby Lobby International
(866) 512-1444
www.hobby-lobby.com
Hobby People
(800) 854-8471
www.hobbypeople.net
Hobby Zone/E-flite RC:
Horizon Hobby
(800) 338-4639
www.horizonhobby.com
New Creations R/C
(936) 856-4630
www.newcreations-rc.com
RC Electronics Cars and Planes Inc.
(408) 705-1980
www.rc-cars-planes.com
07sig2_00MSTRPG.QXD 5/26/10 10:02 AM Page 44

July 2010 39
It’s all about
by Bob Aberle
I WROTE AN article about electric-powered
flight, titled “Introduction to Electric Power,”
that was published in the July 2003 MA. You
can find that feature at the Web site address
that is included in the “Sources” list at the end
of this article.
Seven years later, electric-power
technology has changed tremendously.
Because of the technical advances that have
been made, “e-power,” as it is sometimes
called, now offers many more advantages than
ever!
With that in mind, I am presenting this
updated article. It is a basic introduction, to let
you know what is going on and what is
available in the realm of electrics.
As time goes on,
I plan on writing
more detailed
information that will enable
you to fully appreciate this
exciting form of model propulsion.
If you have thought about trying electric
power, please read on.
What Is Electric Power? It is a system that
operates a motor using electrical energy
stored in a battery, opposed to a fuel tank
feeding an engine. Electric power offers the
model aircraft enthusiast several basic and
important advantages, such as:
1. Quietness:Minimal noise is created
when the motor is operated. It is so quiet that
no mufflers are necessary. This major
advantage has helped aeromodelers obtain
flying fields; silent models will not annoy the
public!
Soundless flying capabilities have
contributed to the establishment of small
aircraft we refer to as “park flyers” or
“backyard flyers.” The inference is that these
models can be flown at local fields without
attracting attention. Public acceptance of
electric-powered models has led to the
development of the AMA’s Park Pilot
Program membership category.
2. Cleanliness: No residue is left on an
airplane after a flight. As a result, no special
finishes need to be applied to the aircraft.
Even more important is the fact that residual
fuel, or even spilled fuel, will not get into our
ground water and create serious ecological
problems in the future. This is another way
our hobby supports the “green” movement.
What Comprises an Electric Power System?
This means of propulsion basically includes a
motor (that turns the propeller), a speed
controller, or ESC, and a battery that provides
electrical energy to operate the motor.
The most efficient motors that modelers
use are the brushless types. These are
basically AC motors that do not require
brushes; therefore, they have nothing to wear
out or need replacing.
Motors are available in two categories:
“outrunner” and “inrunner.” The outrunner
type is the most popular. By design, it can
turn a propeller directly, without a
mechanical gear train.
The author hand-launches his electric FF model. These
power systems work well in all types of aircraft.
Advantages
Electric Power
of
electrons!
Photos by the author
The FMA Direct Cellpro Multi4 charger is
connected to a Li-Poly pack via a node
connector adapter. Different adapters are
available to fit various battery packs.
At the opposite end of the e-power
spectrum are models such as this Hellcat by
Joe Malinchak, a US Airways Captain and
MA “Micro-Flying” columnist. It can’t weigh
more than several grams (not even ounces)
and uses a magnetic actuator for rudder
control.
A basic electric model system has three major components: motor, ESC, and
battery. R-L: typical brushless outrunner and APC electric propeller, brushless
ESC, and Li-Poly pack.
In addition to Li-Poly, there are now several types
of Li-ion batteries. Such a pack that A123Systems
sells is on the right.
The popular Watt’s Up digital meter
stood out because of the excellent 35-
page user’s manual that is supplied
with it. It also stores the highest
readings while connected to a battery.
A great advantage of electric-powered
flight is ROW (rise-off-water) models on
floats. Going electric will give you peace
of mind, knowing that your aircraft
won’t suffer a stalled engine out on the
water.
These are the kinds of connectors you might
encounter when you get involved in electric
power. These devices allow you to unplug
everything for substitution and replacement
purposes.
One of the most important tools you will
need—to be able to fully enjoy and use
electric power for your models—is a device
that can read the most important motor
parameters: current (amperes), voltage, and
the product of the two, which is watts
(power).
The second thing you need is a meter—
preferably digital. Plan on spending probably
$50-$60 for one. There are several good ones
on the market, and all will do the same job.
I especially like the Watt’s Up wattmeter,
because the manufacturer, RC Electronics,
supplies a 35-page user’s manual that covers
all of the various applications for this
product. You can find the manual on the
company’s Web site.
There are numerous types of battery
chargers on the hobby market. Many are used
for a specific type or brand of battery.
My favorite is the FMA Direct Multi4,
because it can charge almost any battery
chemistry, packs with as many as four cells,
and up to 4 amps of current. FMA Direct also
sells a variety of node connector adapters that
will allow you to charge nearly any brand of
battery you can obtain.
Rather than spend several pages
describing all that the Multi4 can do, check
out the user’s manual, located on the FMA
Direct Web site. FMA Direct also sells the
Cellpro 10S charger, for those who need to
charge packs with as many as 10 cells at 10
amps.
Connectors are a vital part of electric
power systems. These connectors allow
y ou to plug toge ther all of the
co m po nents that make a f ull system.
Many of the individual components
come with connectors already installed.
Unfortunately not all do, so you might be
required to install your own. In some cases
you can do that with a mechanical crimping
tool, but you will usually need to solder the
connectors.
When you get down to the multipin node
connectors that allow you to balance-charge
battery packs, there is no industry standard
or convention. There are currently at least
six types of node connectors you might have
to deal with: PolyQuest, Thunder Power,
FMA Direct Revolution, Kokam, Horizon
Hobby (E-flite and ParkZone), and Great
Planes (ElectriFly). Most manufacturers sell
balanced charge adapters to satisfy these
connectors. MA
—Bob Aberle
[email protected]
Sources:
RC Electronics
(408) 705-1980
www.rc-cars-planes.com
Thunder Power
(702) 228-8883
www.thunderpowerrc.com
Horizon Hobby
(800) 338-4639
www.horizonhobby.com
Essential Tools for the Electric Modeler
40 MODEL AVIATION
07sig2_00MSTRPG.QXD 5/26/10 9:50 AM Page 40
July 2010 41
Electric-powered aircraft benefit from their power-to-weight
ratios and quick throttle responses, making them an excellent
choice for hovering and 3-D. Those maneuvers also require
the model to have extreme control-surface movement.
Bob Hunt, an international CL Precision Aerobatics champion, holds
his Genesis Extreme design. Power is an AXI 2826-10 brushless
outrunner motor, Castle Creations Phoenix-45 ESC, and Thunder
Power 4S2P Li-Poly pack. Bob flew this model in the 2006 World
Championships in Spain, which made him the first pilot to ever fly an
electric CL model at a World Champs.
Andrew Jesky took first place in F3A at the 2009 Nats
with this Krill Spark. It uses a Hacker brushless power
system and Thunder Power batteries.
Electrified jets are hugely popular and as capable as
those powered by turbines. E-power allows jets
constructed from foam, such as this SR-71, to be an
exciting, low-cost alternative for RC pilots.
There are many more advantages to using electric power for
models than the fact that it is quiet and clean. I mentioned those
attributes in the main text of this article, but following is a summary
of its other benefits.
• Improved motor efficiency by going brushless.
• Reduced system weight. Motors and batteries weigh less than
engines and their related components, making for lighter models.
• Longer motor run times. Batteries have become lighter in weight and
have more capacity.
• Faster battery recharging. This quickly gets your aircraft back into
the air.
• Safer operation.
• Improved linear throttle response for more precise model flight
control, especially with 3-D-type hovering maneuvers.
Electric-power enthusiasts enjoy several prominent events across
the country. It is common to see 300-500 registered electric-power
pilots and several thousand spectators at these gatherings.
The annual NEAT (Northeast Electric Aircraft Technology) Fair in
upstate New York, held every September, is one of the largest
electric-flight gatherings. The big SEFF (Southeast Electric Flight
Festival) in the Atlanta, Georgia, area is held every May. For micro
and indoor electric-power aeromodelers, there is the new KIEF
(Keystone Indoor Electric Fly), which takes place each October in
Muncy, Pennsylvania.
These are just a few of the fly-ins on the schedule. More are being
added each year. MA
—Bob Aberle
[email protected]
Electric Events:
NEAT Fair
www.neatfair.org
SEFF
http://seff2010.com
KIEF
www.pafunfly.com
Where Are Electrics Today?
This 68-inch-wingspan E-flite Beaver was designed
from the ground up to be electric. It can be flown
with a brushless motor that is equivalent to
a .25 or .32 glow engine.
National Electric Fly-In (NEFI)
www.modelaircraft.org/events/
NEFI.aspx
Arizona Electric Festival (AEF)
www.azmodelaviators.com
07sig2_00MSTRPG.QXD 5/26/10 9:53 AM Page 41
42 MODEL AVIATION
Dave Baron with his scale, multimotor
Boeing B-17 that features a retract landing
gear system. He has been performing demo
flights with this model at the NEAT Fair
for many years. Dave recently updated
the B-17 with brushless motors and
Li-Poly batteries.
Darrell Sprayberry builds and competes with RC electric
Scale helicopters. This one, detailed as one
flown by the Georgia State Police,
weighs 37 pounds and uses an
AXI motor for power.
References for Electric Power
MA
(765) 287-1256
www.modelaircraft.org/mag
Park Pilot
(765) 287-1256
www.theparkpilot.org
Model Aviation’s Sport Aviator
www.masportaviator.com
Flying Models
(888) 526-5365
www.flying-models.com
RC Micro World
www.cloud9rc.com
AMA’s Forum
www.modelaircraft.org/forums/default.aspx
WattFlyer
www.wattflyer.com/forums
The E Zone
www.ezonemag.com/pages
RCGroups
www.rcgroups.com/forums/index.php
RC Universe (Select “Electric Flight.”)
www.rcuniverse.com
Everything You Wanted To Know About Electric Powered Flight:
www.tcws.org/aeajr_eflight_ebook.pdf
Barnes & Noble
(800) 843-2665
www.barnesandnoble.com
RCAdvisor.com
(505) 206-1569
www.rcadvisor.com
AMA retail store
(765) 287-1256
www.modelaircraft.org/shopama
The World of Indoor/Micro Radio Controlled Model Aircraft
(all electric) By Bob Aberle on CD. Web site: www.cloud
9rc.com.
Several print and online magazines cater to the electric-powered
aeromodeler. Following are a few to which you can refer.
• MA features five columns that contain information about electrics:
“Electrics” by Greg Gimlick, “The Battery Clinic” by Red Scholefield,
“Small-Field Flying” by Paul Bradley, “Micro-Flying” by Joe Malinchak,
and “Frequently Asked Questions,” which I write.
My column is not exclusive to electric power, but it includes many
inquiries about the topic. Feel free to e-mail or write to any of us
columnists with your questions. MA also publishes reviews and articles
about electric power or featuring product reviews.
Each month MA publishes product reviews and articles about electric
power products.
• Park Pilot magazine continually publishes product reviews and articles
that feature electric power.
• Model Aviation’s Sport Aviator online magazine contains loads of reviews
and feature articles about electric-powered aircraft and electric power.
• Flying Models magazine has a column titled “Electric Flight,” which
Don Belfort and Stew Meyers alternate writing each month.
• RC Micro World Online Magazine is for micro and indoor electricpower
fliers.
Hobby forums provide an excellent opportunity to ask questions and
receive answers. Not all those who respond to inquiries are experts, but
their replies can still prove to be helpful.
There are five forums that I use and recommend.
• AMA’s Forum
• Watt Flyer
• The E Zone
• RCGroups
• RC Universe
Following are some good books about using electric power in our
models.
• Everything You Wanted To Know About Electric Powered Flight is an
online “E-Book” by Ed Anderson. You can find it on the Tri-County
Wing Snappers Web site; the address is in the “Sources” list.
• How to Build and Fly Electric Model Aircraft is by Robert Schleicher.
You can find it at Barnes & Noble.
• RCadvisor’s Modi-Fly by Carlos Reyes takes you through designing and
building an electric-powered model from scratch—in one day. It is
available from RCadvisor.com.
• Getting Started in Backyard Flying is a book that I wrote. You can get it
from AMA Headquarters’ retail store.
• The World of Indoor/Micro Radio Controlled Model Aircraft (all
electric) is another book that I wrote, available on CD. It’s available from
RC Micro World. MA
—Bob Aberle
[email protected]
07sig2_00MSTRPG.QXD 5/26/10 9:56 AM Page 42
Unlike fueled engines, which are
categorized by cu. in. displacement, motors
are generally rated by input power measured
in watts. If you multiply the motor current
(in amperes) by the voltage applied from the
battery, you obtain the wattage, or the power
input.
To size a motor, use the parameter called
“power loading”; it relates power input
(watts) to the total weight of an aircraft. The
resulting watts-per-pound figure is the key
to determining the correct-size motor for
your model. Later you will find many
references to this all-important parameter.
It is important to know that when dealing
with electric flight, each motor can provide a
broad range of power. The size, weight, and
armature windings are one consideration.
The choice of propeller size is a second.
Voltage applied to the motor is a third.
Coordinating those three variables is the
secret to enjoying all of the advantages of
electric-powered flight.
The ESC is inserted between the motor
and the battery. It essentially takes the place
of the servo that would control the
carburetor of a fueled engine. The servo
cable that exits every ESC is plugged into
the throttle port (connector) on your RC
receiver.
Moving the throttle-channel control stick
on an RC transmitter will turn a motor on or
off and provide variable speeds from idle to
full power. Besides the servo cable, there is
a three-wire cable that goes to the brushless
motor and a two-wire cable that goes to the
battery pack.
Modern ESC technology includes some
sophisticated electronics that provides, by
itself, many advantages for electric flight. A
modeler can program most of today’s ESCs
for specific operations, such as the direction
of the motor rotation.
An ESC will also prevent a motor from
starting, unless the transmitter throttle stick
is at the dead low or idle position. This
eliminates any chance of a motor
accidentally starting and causing an injury.
An ESC will shut down the motor when
a preset voltage level is reached. This is
necessary, because Li-Poly batteries can be
permanently damaged if the voltage drops to
a certain level. And if any kind of
interference hits your RC system, the motor
will be shut down as a warning that you had
best land your model in a hurry.
A unique feature of most ESCs is the
battery eliminator circuit, or BEC. This
enables your motor battery to also provide
power to your RC system. By doing this,
only one battery pack is required on your
aircraft. Although this BEC feature had its
limits years ago (such as current demands
and voltage), most airplanes today, except
for the very large models, can be flown off
of a BEC on a single battery pack.
Currently, the most popular battery for
electric-powered flight is the Lithium
Polymer type, or “Li-Poly.” This technology
emerged in our hobby approximately seven
years ago and completely changed the way
we fly electric models.
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These batteries offer much more
capacity and are available in packages that
weigh much less than the older Ni-Cd and
NiMH batteries. And because of the
popularity of Li-Polys, their prices have
come way down in recent times.
Li-Poly battery cells have a
characteristic voltage of 4.20 when fully
charged. They should be recharged at a 1C
rate, which can take as long as an hour;
that depends on the state of charge at the
time the charging started.
Improved Li-Poly cells that have
recently been released are capable of
charging at 2C rates in 30 minutes and 3C
rates in 20 minutes. Another characteristic
of Li-Polys is that they should not be
discharged lower than roughly 3.0 volts
(per cell).
Early on it was determined that Li-Poly
batteries, contained in packs of two or
more cells, needed to be balanced. This
simply means that every cell in the pack
should have the same voltage at full
charge.
To make that happen, battery packs are
assembled in such a way that each cell can
be separately charged and monitored. This
requires a special connector that is
attached to every Li-Poly battery pack
containing two or more cells.
The multipin connectors are referred to
07sig2_00MSTRPG.QXD 5/26/10 9:59 AM Page 43
44 MODEL AVIATION
as “node connectors.” Modern battery
chargers provide the necessary interface with
the various node connectors used throughout
our hobby.
Besides Li-Poly, popular battery chemistry
involves Lithium-ion, or Li-ion, technology.
These batteries are referred to by several
names, but the most common cells and packs
are produced by A123Systems.
I urge you to read the three-part article
titled “Those Things We Call Batteries,”
which you can find on Model Aviation’s Sport
Aviator Web site. The address is in the
“Sources” list.
And to learn more, you can read MA’s
popular bimonthly “The Battery Clinic”
column. It is written by Red Scholefield, who
is a noted battery expert.
Most SIGs in our hobby are using electric
power. It has been integrated into almost all
aspects of aeromodeling, including trainers,
sport fliers, park flyers, standoff-scale, Scale
(national and international), Aerobatics
(national and international), 3-D (hovering and
demonstrations), sailplanes, Old-Timers, FF,
micro and indoor flyers, CL (national and
international), vintage RC, helicopters, and
giant scale.
The AMA Nats that traditionally runs the
entire month of July at AMA Headquarters in
Muncie, Indiana, now has many competitors
who use electric power. This is especially true
with CL, Scale, Aerobatics, and helicopters.
Further advancing the growing popularity
of electric power is the fact that so many
hobby manufacturers are now offering ARF
and RTF models. Many of them arrive with
the motor, ESC, and batteries installed at the
factory. And there are numerous fueled aircraft
that can be converted to electric power.
This increased popularity has resulted in
considerable component price reductions that
make electrics affordable. That popularity has
also expanded the market, and the result is that
aeromodelers have more choices of motors,
ESCs, and batteries.
Today’s electric power systems for models
are probably easier to operate than fueled
engines. Ample information is available about
electrics, and you can get all the details you
need to be able to assemble, install, and
operate your own system.
The “Sources” list includes several key
manufacturers in the electric-power market.
You can obtain products and advice from
them.
You don’t need an electrical engineering
degree to enjoy all the advantages of
electrics. Yes, you will have to learn to
solder. But as time passes, the
manufacturers might do much of that type
of work for you.
Battery care and feeding is also
benefiting from better products and more
sophisticated chargers that automatically do
practically everything for you. With so
many people into electrics now, you might
find plenty of aeromodelers to answer
questions as you learn.
Sizing electric power systems to fit your
models is probably the most important
aspect of this type of flight and will require
you to learn several things. Recognizing
that this might prevent some modelers from
getting into electrics, I decided to write an
article about the subject.
The two-part feature is posted on the Sport
Aviator Web site, and you can find it at the
address in the “Sources” listing. This piece
covers all aspects of the watts-per-pound
parameter that is the key to motor selection.
Make sure you read every word. MA
Bob Aberle
[email protected]
Sources:
“Introduction to Electric Power”
www.modelaircraft.org/mag/FTGU/Part5/5m
ain.html
A123Systems
(617) 778-5700
www.a123systems.com
“Those Things We Call Batteries”
Part One:
www.masportaviator.com/ah.asp?CatID=2&I
D=146
Part Two:
www.masportaviator.com/ah.asp?CatID=2&I
D=149
Part Three:
www.masportaviator.com/ah.asp?CatID=2&I
D=164&index=0
“Selecting Electrical Power Systems”
Part One:
www.masportaviator.com/ah.asp?CatID=2&I
D=76
Part Two:
www.masportaviator.com/ah.asp?CatID=2&I
D=77
BSD Micro RC
(417) 358-9521
www.bsdmicrorc.com
BP Hobbies
(732) 287-3933
www.bphobbies.com
Castle Creations
(913) 390-6939
www.castlecreations.com
FMA Direct
(800) 343-2934
www.fmadirect.com
Great Planes (ElectriFly)
(800) 637-7660
www.greatplanes.com
Hitec RCD/Multiplex USA
(858) 748-8440
www.hitecrcd.com
www.multiplexusa.com
Hobby Lobby International
(866) 512-1444
www.hobby-lobby.com
Hobby People
(800) 854-8471
www.hobbypeople.net
Hobby Zone/E-flite RC:
Horizon Hobby
(800) 338-4639
www.horizonhobby.com
New Creations R/C
(936) 856-4630
www.newcreations-rc.com
RC Electronics Cars and Planes Inc.
(408) 705-1980
www.rc-cars-planes.com
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