58 MODEL AVIATION
FMA DIRECT’S Flight Systems 5 (FS5) is a
new concept in RC receiver circuit design.
Although the company does offer complete
RC systems (transmitter, receiver, servos,
batteries, etc.), one of its primary product
lines for many years has been what are called
“aftermarket” RC receivers. They have been
designed so that almost any FM (also known
as Pulse Position Modulation, or PPM)
transmitter on the market can operate them.
Most RC transmitters employing a
microcomputer chip can provide model
memory or data storage for four, six, seven,
eight, and more aircraft. The idea is that you
need only one transmitter, and that unit is
capable of operating as many as eight
Te c h n i c a l R e v i e w Bob Aberle
E-mail: [email protected]
Besides FS5 receiver, system includes external switch/LED assembly, PC interface
module, and CD containing special viewer software program information.
Receiver with remote switch and LED assembly which allows you
to extend switch/LED function to outside model’s fuselage.
Close-up of FMA Co-Pilot control unit that goes inside an aircraft.
This device was reviewed in the August 2002 MA.
receivers and more in different aircraft. FMA
Direct has made a business of supplying these
individual (or extra) receivers to the RC
enthusiast.
The FS5 is the company’s newest
aftermarket RC receiver. It is small,
measuring 15⁄8-inch long, 13⁄16-inch wide, 9⁄16-
inch high, and weighing a mere .4 ounce. It
employs FM dual-conversion circuitry. The
current model has five channel functions, but
an eight-channel-capable version will be
available soon.
You must purchase the operating crystal
separately from FMA Direct. The FS5
receiver—part 905FM72—has a retail price
of $99.95. The crystal—part RXQTM72-XX
(where “XX” is the channel number)—is an
additional $12.95.
The FS5 is also a universal receiver, in the
sense that it can operate with high or low FM
deviation automatically. So whether you have
Futaba or Hitec on the high side or JR or
Airtronics on the low side, you will be able to
operate this unit.
Probably one of the FS5 receiver’s most
distinctive features is a new concept called
“Digital Signal Recognition” (DSR). This
proprietary circuit allows the receiver to
measure and store your RC transmitter’s
unique characteristics. Then throughout a
flight, this DSR circuit continuously compares
the incoming signals against your
transmitter’s stored “signature.” The claim is
that the DSR rejects signals from sources
other than your transmitter.
I tried to verify that claim by placing a
second RC transmitter nearby, operating on
the same frequency (channel number). How
60 MODEL AVIATION
close that interfering transmitter was to the
operating transmitter made a difference in the
final outcome.
Close by, the FS5 sensed massive
interference and went into fail-safe. At a
distance from the operating transmitter, I was
able to obtain control of the aircraft while the
DSR circuit was obviously working hard to
maintain the primary control. In this regard,
the FS5 offers a significant amount of
protection against even direct on-channel
interference.
As you will learn in this review, the FS5
receiver is part of an overall system
containing many features that can benefit the
RC flier and promote safety at the same time.
With all of the features together, you end up
with a moderately complex system operation.
If you read the excellent 22-page
document “The FMA Flight System: New
technologies for protecting RC aircraft” (go to
www.fmadirect.com/site/fma.htm?body=Sup
port, scroll down to “Technical Documents,”
and then select “FMA Flight Systems White
An up-close look at the switch/LED
assembly. This is an optional item that
Infrared sensor module portion of Co- you must purchase separately.
Pilot that is usually mounted on top of
wing or bottom of fuselage, where it can
view out front and sides.
On component side of the FS5 receiver,
knife blade points to the push-button
switch that is referenced in the text.
Remote switch/LED assembly cable plugs
into socket on FS5 below switch button.
External switch/LED then parallel same
items mounted on receiver PC board.
Bob’s Playboy Sr. test model. Switch button and LED are mounted
on fuselage side. Li-Poly pack is mounted below motor.
Remote switch/LED assembly mounted
on typical model fuselage. This way you
can push switch button and observe
glowing LED from outside of fuselage.
Co-Pilot’s two major parts. System can be integrated into FS5 so
model will always be righted or guided to level flight.
Paper”), you might feel that this system is too
much for you. Don’t get scared way!
If you purchase only the FS5 receiver and
install it in your model, as you would any
other RC receiver, you will come out ahead.
The rest of the features, such as setting up
fail-safe positions, knowing when interference
strikes your receiver, retrieving stored control
Photos by the author
data on a personal computer (PC), and even
integrating the FMA Co-Pilot selfstabilizing
device into the system, can be
added later, as you gain experience or get
curious!
Let’s say you bought an FS5 receiver. What
benefits would you derive by installing it in
your aircraft?
The FS5 provides all the fail-safe
features that can normally only be obtained
from an expensive Pulse Code Modulation
(PCM) RC system; now you can obtain
those same fail-safe features with your
regular FM RC system just by employing
the FS5 receiver.
The way this works, if your model is inflight
and interference is received from
another RC system (at your field or nearby),
is that all the primary controls (aileron,
elevator, rudder, and throttle) on your
model will be held (frozen) at their last
known positions before receiving the
interference. They won’t jitter around or go
hard over when that interference is received.
Another scenario might be an out-ofrange
situation in which the aircraft goes
too far away and the signal is lost. Again,
the controls lock up on the last known
position. That same situation might occur if
your transmitter dropped out of service in
flight (unlikely!) or if the transmitter battery
ran out of charge or failed. Any radio-signal
loss also prompts all the controls to freeze
at their last known position.
I know exactly what you are going to say
at this point! “If my aircraft is in a turn or a
dive at the moment interference is received
and the controls freeze, it is surely going to
head right for the ground and likely at full
power.”
That may be true because you can’t
predict a particular attitude at any given
time during a flight. So now comes the next
feature; the FS5 will allow you to program
preset control positions for each of the four
primary flight controls, as well as the
auxiliary (fifth) channel.
You might set the controls for a slight
amount of up-elevator, a bit of right rudder
and/or right aileron, and low speed or idle
speed on the engine/motor. Then if
interference is received or the transmitter
signal is lost, all of the controls will
immediately go to these preprogrammed
positions. These presets will remain in the
receiver’s memory even after the power is
turned off. They won’t change until you
change them.
Admittedly, the aircraft might be in a
banking or diving attitude when the fail-safe
kicks in. Even though you have the controls
set for engine low and a slight climbing
turn, it might not be enough to level the
model, and, as a result, a crash can still
happen.
The hope is that the preprogrammed
control positions will keep your airplane in
the air until the interference clears. In many
cases that may only be a few seconds in real
time; but just to provide added safety, FMA
Direct has taken that extra step to integrate
its popular Co-Pilot self-stabilizing system
into the FS5.
Therefore, if interference occurs in
flight, the fail-safe operates to its preset
controls and the Co-Pilot will stabilize the
aircraft back to straight and level flight. If
you are interested, I reviewed the FMA
Direct Co-Pilot in the August 2002 MA
(pages 77-79).
Since setting the fail-safe preset control
positions is important, I’ll take you through
how easy it is to do. Before I begin, you
need to know that on the component side of
the FS5 receiver is a push-button switch and
an LED that glows a bright orange or red
when it’s on. That switch button and the
LED allow you to program the control
positions. They also let you use many other
receiver features, which I will get into later.
Because the receiver will more than
likely be inside your aircraft’s fuselage,
having access to the switch and the LED
could be a problem. To rectify that, FMA
Direct has come up with a remote switch and
LED (part FSRES1) that has a cable that
plugs into a connector on the receiver. You
can mount the switch/LED assembly on a
fuselage side, top, or bottom, so that the
LED is visible and you can operate the
switch from the outside of the aircraft. I
chose this option, as shown, and it makes
total sense!
To set up a preset fail-safe control
position, turn on your transmitter and make
sure that all three primary control functions
(aileron, elevator, and rudder) have their
sticks in the neutral position and that the
throttle stick is in the low or idle position.
Depress the switch button, and while holding
the button down, turn on the receiver power.
Let go of the button and the LED will begin
to “twinkle” (flash extremely fast).
Let’s say you want to preset up-elevator.
Using the transmitter elevator control stick,
apply some up-elevator. While holding that
position, press the button (on the side of the
fuselage) once and then immediately let go of
the elevator stick so that it springs back to
neutral. When you turn the receiver power
off, you will have left the setup mode, and the
elevator preset will be stored for good in the
receiver memory.
To make sure you did this correctly,
power up the receiver with the transmitter on.
Move the control sticks, and you should note
normal control. Turn off the transmitter
(simulating loss of signal), and the elevator
should move to your preset fail-safe position.
Turning the transmitter back on, your controls
go back to neutral and work in a normal
manner. You should experience the same
reaction if interference hits your FS5 receiver.
But beyond the fail-safe operation and the
fail-safe preset control capabilities, there are
many other features in the FMA FS5
receiver’s operation. When at the flying field,
you can turn on the receiver, leaving the
transmitter off, and watch the LED. If you see
one blink, it means your frequency is clear
and you can proceed to fly.
A continuous series of blinks means that
your receiver just experienced some form of
interference and you best investigate before
attempting to fly your model. Someone may
already be flying on your channel and forgot
to take the frequency control clip.
A bonus is that you can read your receiver
battery’s voltage by counting blinks on the
LED. Press the button once. The LED will
provide a long blink for every 1.0 volt and a
short blink for every 0.1 volt. Therefore, four
long blinks and nine short blinks would be
4.9 volts.
The FS5 will also let you know, after a
flight, if the fail-safe activated for any reason
during the flight. After landing, keep the
transmitter and receiver on. Immediately
observe the LED. If it glows a solid or steady
orange/red color, you did not experience any
interference. If it blinks, you experienced failsafe
during that particular flight. You can
count the number of blinks to determine how
many times the receiver went into fail-safe.
After observing that condition, you can
read the number of “bad frames” that
occurred during the flight if you press the
button three times. Thus you have a
sophisticated and highly accurate “glitch
counter.”
I learned that it takes 50 consecutive bad
frames before the receiver enters fail-safe. So
it is possible to have experienced something
such as 30 bad frames in a flight and still not
enter fail-safe. Keep in mind that when you
turn the power off, you lose that saved data
from the last flight.
You can also use the FS5 to help you
range-check your entire RC system. You
traditionally perform the ground range test by
collapsing the transmitter antenna (to reduce
its power) and having someone walk away
with the transmitter while continuously
operating one channel control, such as
elevator.
Have the person walk out the distance the
RC manufacturer recommends; let’s say it’s
100 feet. With the transmitter and receiver
power still on, observe the LED. If it is not
blinking, you have a perfect range test. If it is
blinking, the number of blinks indicates the
number of “bad frames” you received during
the test.
If that happens, you will have to explore
the usual possibilities, such as equipment
problems or an antenna placed too close to a
noise-generating component such as a servo!
The LED gives you an exact measure of what
is going on!
So far you have learned that the FS5
receiver can output data by counting the
blinks of a single LED. As part of the entire
flight system, FMA Direct also offers a
Flight Systems Receiver Viewer Software
package. It consists of a PC interface module
(part FSIM1) that connects between the FS5
receiver (Channel 1 port) and the serial port
on a PC.
For added convenience, a nine-pin-tonine-
pin serial cable is provided, which will
extend the distance between the interface
module and the PC. Along with this, you get
a CD containing the viewer software
program itself. The software is intended for
PCs with Windows 98 or a later version of
Windows, along with Internet Explorer 6.0 or
later.
Since the data is only stored while the
power is still applied to the receiver, it is
assumed that you will use a laptop-type
portable computer and download the data at
the flying field, unless you are doing your
own testing within the confines of your home
shop.
I won’t get any further into the FS5’s details
in this review. The previously referenced
white paper will provide much more
information. The FMA Direct Web site
provides component and system part
numbers and prices.
The key thing to remember is that first
and foremost, you are getting an excellent
new RC receiver. It is lightweight and small.
That makes it suitable for indoor and parking
lot RC, the largest 1⁄4-scale models, and
more!
It is of dual-conversion circuitry, featuring
excellent sensitivity, selectivity, and the
ability to reject second- and third-order
intermodulation situations. All these features,
along with programmable fail-safe, are
essentially available right out of the box.
To gain these features, you do not need
the computer interface or the Co-Pilot selfstabilizing
system, but these extras are
available as options when you feel you need
them or want to try them. MA
Manufacturer:
FMA Direct Inc.
5716A Industry Ln.
Frederick MD 21704
Sales: (800) 343-2934
Technical: (301) 668-7614
Edition: Model Aviation - 2004/11
Page Numbers: 58,60,62,64
Edition: Model Aviation - 2004/11
Page Numbers: 58,60,62,64
58 MODEL AVIATION
FMA DIRECT’S Flight Systems 5 (FS5) is a
new concept in RC receiver circuit design.
Although the company does offer complete
RC systems (transmitter, receiver, servos,
batteries, etc.), one of its primary product
lines for many years has been what are called
“aftermarket” RC receivers. They have been
designed so that almost any FM (also known
as Pulse Position Modulation, or PPM)
transmitter on the market can operate them.
Most RC transmitters employing a
microcomputer chip can provide model
memory or data storage for four, six, seven,
eight, and more aircraft. The idea is that you
need only one transmitter, and that unit is
capable of operating as many as eight
Te c h n i c a l R e v i e w Bob Aberle
E-mail: [email protected]
Besides FS5 receiver, system includes external switch/LED assembly, PC interface
module, and CD containing special viewer software program information.
Receiver with remote switch and LED assembly which allows you
to extend switch/LED function to outside model’s fuselage.
Close-up of FMA Co-Pilot control unit that goes inside an aircraft.
This device was reviewed in the August 2002 MA.
receivers and more in different aircraft. FMA
Direct has made a business of supplying these
individual (or extra) receivers to the RC
enthusiast.
The FS5 is the company’s newest
aftermarket RC receiver. It is small,
measuring 15⁄8-inch long, 13⁄16-inch wide, 9⁄16-
inch high, and weighing a mere .4 ounce. It
employs FM dual-conversion circuitry. The
current model has five channel functions, but
an eight-channel-capable version will be
available soon.
You must purchase the operating crystal
separately from FMA Direct. The FS5
receiver—part 905FM72—has a retail price
of $99.95. The crystal—part RXQTM72-XX
(where “XX” is the channel number)—is an
additional $12.95.
The FS5 is also a universal receiver, in the
sense that it can operate with high or low FM
deviation automatically. So whether you have
Futaba or Hitec on the high side or JR or
Airtronics on the low side, you will be able to
operate this unit.
Probably one of the FS5 receiver’s most
distinctive features is a new concept called
“Digital Signal Recognition” (DSR). This
proprietary circuit allows the receiver to
measure and store your RC transmitter’s
unique characteristics. Then throughout a
flight, this DSR circuit continuously compares
the incoming signals against your
transmitter’s stored “signature.” The claim is
that the DSR rejects signals from sources
other than your transmitter.
I tried to verify that claim by placing a
second RC transmitter nearby, operating on
the same frequency (channel number). How
60 MODEL AVIATION
close that interfering transmitter was to the
operating transmitter made a difference in the
final outcome.
Close by, the FS5 sensed massive
interference and went into fail-safe. At a
distance from the operating transmitter, I was
able to obtain control of the aircraft while the
DSR circuit was obviously working hard to
maintain the primary control. In this regard,
the FS5 offers a significant amount of
protection against even direct on-channel
interference.
As you will learn in this review, the FS5
receiver is part of an overall system
containing many features that can benefit the
RC flier and promote safety at the same time.
With all of the features together, you end up
with a moderately complex system operation.
If you read the excellent 22-page
document “The FMA Flight System: New
technologies for protecting RC aircraft” (go to
www.fmadirect.com/site/fma.htm?body=Sup
port, scroll down to “Technical Documents,”
and then select “FMA Flight Systems White
An up-close look at the switch/LED
assembly. This is an optional item that
Infrared sensor module portion of Co- you must purchase separately.
Pilot that is usually mounted on top of
wing or bottom of fuselage, where it can
view out front and sides.
On component side of the FS5 receiver,
knife blade points to the push-button
switch that is referenced in the text.
Remote switch/LED assembly cable plugs
into socket on FS5 below switch button.
External switch/LED then parallel same
items mounted on receiver PC board.
Bob’s Playboy Sr. test model. Switch button and LED are mounted
on fuselage side. Li-Poly pack is mounted below motor.
Remote switch/LED assembly mounted
on typical model fuselage. This way you
can push switch button and observe
glowing LED from outside of fuselage.
Co-Pilot’s two major parts. System can be integrated into FS5 so
model will always be righted or guided to level flight.
Paper”), you might feel that this system is too
much for you. Don’t get scared way!
If you purchase only the FS5 receiver and
install it in your model, as you would any
other RC receiver, you will come out ahead.
The rest of the features, such as setting up
fail-safe positions, knowing when interference
strikes your receiver, retrieving stored control
Photos by the author
data on a personal computer (PC), and even
integrating the FMA Co-Pilot selfstabilizing
device into the system, can be
added later, as you gain experience or get
curious!
Let’s say you bought an FS5 receiver. What
benefits would you derive by installing it in
your aircraft?
The FS5 provides all the fail-safe
features that can normally only be obtained
from an expensive Pulse Code Modulation
(PCM) RC system; now you can obtain
those same fail-safe features with your
regular FM RC system just by employing
the FS5 receiver.
The way this works, if your model is inflight
and interference is received from
another RC system (at your field or nearby),
is that all the primary controls (aileron,
elevator, rudder, and throttle) on your
model will be held (frozen) at their last
known positions before receiving the
interference. They won’t jitter around or go
hard over when that interference is received.
Another scenario might be an out-ofrange
situation in which the aircraft goes
too far away and the signal is lost. Again,
the controls lock up on the last known
position. That same situation might occur if
your transmitter dropped out of service in
flight (unlikely!) or if the transmitter battery
ran out of charge or failed. Any radio-signal
loss also prompts all the controls to freeze
at their last known position.
I know exactly what you are going to say
at this point! “If my aircraft is in a turn or a
dive at the moment interference is received
and the controls freeze, it is surely going to
head right for the ground and likely at full
power.”
That may be true because you can’t
predict a particular attitude at any given
time during a flight. So now comes the next
feature; the FS5 will allow you to program
preset control positions for each of the four
primary flight controls, as well as the
auxiliary (fifth) channel.
You might set the controls for a slight
amount of up-elevator, a bit of right rudder
and/or right aileron, and low speed or idle
speed on the engine/motor. Then if
interference is received or the transmitter
signal is lost, all of the controls will
immediately go to these preprogrammed
positions. These presets will remain in the
receiver’s memory even after the power is
turned off. They won’t change until you
change them.
Admittedly, the aircraft might be in a
banking or diving attitude when the fail-safe
kicks in. Even though you have the controls
set for engine low and a slight climbing
turn, it might not be enough to level the
model, and, as a result, a crash can still
happen.
The hope is that the preprogrammed
control positions will keep your airplane in
the air until the interference clears. In many
cases that may only be a few seconds in real
time; but just to provide added safety, FMA
Direct has taken that extra step to integrate
its popular Co-Pilot self-stabilizing system
into the FS5.
Therefore, if interference occurs in
flight, the fail-safe operates to its preset
controls and the Co-Pilot will stabilize the
aircraft back to straight and level flight. If
you are interested, I reviewed the FMA
Direct Co-Pilot in the August 2002 MA
(pages 77-79).
Since setting the fail-safe preset control
positions is important, I’ll take you through
how easy it is to do. Before I begin, you
need to know that on the component side of
the FS5 receiver is a push-button switch and
an LED that glows a bright orange or red
when it’s on. That switch button and the
LED allow you to program the control
positions. They also let you use many other
receiver features, which I will get into later.
Because the receiver will more than
likely be inside your aircraft’s fuselage,
having access to the switch and the LED
could be a problem. To rectify that, FMA
Direct has come up with a remote switch and
LED (part FSRES1) that has a cable that
plugs into a connector on the receiver. You
can mount the switch/LED assembly on a
fuselage side, top, or bottom, so that the
LED is visible and you can operate the
switch from the outside of the aircraft. I
chose this option, as shown, and it makes
total sense!
To set up a preset fail-safe control
position, turn on your transmitter and make
sure that all three primary control functions
(aileron, elevator, and rudder) have their
sticks in the neutral position and that the
throttle stick is in the low or idle position.
Depress the switch button, and while holding
the button down, turn on the receiver power.
Let go of the button and the LED will begin
to “twinkle” (flash extremely fast).
Let’s say you want to preset up-elevator.
Using the transmitter elevator control stick,
apply some up-elevator. While holding that
position, press the button (on the side of the
fuselage) once and then immediately let go of
the elevator stick so that it springs back to
neutral. When you turn the receiver power
off, you will have left the setup mode, and the
elevator preset will be stored for good in the
receiver memory.
To make sure you did this correctly,
power up the receiver with the transmitter on.
Move the control sticks, and you should note
normal control. Turn off the transmitter
(simulating loss of signal), and the elevator
should move to your preset fail-safe position.
Turning the transmitter back on, your controls
go back to neutral and work in a normal
manner. You should experience the same
reaction if interference hits your FS5 receiver.
But beyond the fail-safe operation and the
fail-safe preset control capabilities, there are
many other features in the FMA FS5
receiver’s operation. When at the flying field,
you can turn on the receiver, leaving the
transmitter off, and watch the LED. If you see
one blink, it means your frequency is clear
and you can proceed to fly.
A continuous series of blinks means that
your receiver just experienced some form of
interference and you best investigate before
attempting to fly your model. Someone may
already be flying on your channel and forgot
to take the frequency control clip.
A bonus is that you can read your receiver
battery’s voltage by counting blinks on the
LED. Press the button once. The LED will
provide a long blink for every 1.0 volt and a
short blink for every 0.1 volt. Therefore, four
long blinks and nine short blinks would be
4.9 volts.
The FS5 will also let you know, after a
flight, if the fail-safe activated for any reason
during the flight. After landing, keep the
transmitter and receiver on. Immediately
observe the LED. If it glows a solid or steady
orange/red color, you did not experience any
interference. If it blinks, you experienced failsafe
during that particular flight. You can
count the number of blinks to determine how
many times the receiver went into fail-safe.
After observing that condition, you can
read the number of “bad frames” that
occurred during the flight if you press the
button three times. Thus you have a
sophisticated and highly accurate “glitch
counter.”
I learned that it takes 50 consecutive bad
frames before the receiver enters fail-safe. So
it is possible to have experienced something
such as 30 bad frames in a flight and still not
enter fail-safe. Keep in mind that when you
turn the power off, you lose that saved data
from the last flight.
You can also use the FS5 to help you
range-check your entire RC system. You
traditionally perform the ground range test by
collapsing the transmitter antenna (to reduce
its power) and having someone walk away
with the transmitter while continuously
operating one channel control, such as
elevator.
Have the person walk out the distance the
RC manufacturer recommends; let’s say it’s
100 feet. With the transmitter and receiver
power still on, observe the LED. If it is not
blinking, you have a perfect range test. If it is
blinking, the number of blinks indicates the
number of “bad frames” you received during
the test.
If that happens, you will have to explore
the usual possibilities, such as equipment
problems or an antenna placed too close to a
noise-generating component such as a servo!
The LED gives you an exact measure of what
is going on!
So far you have learned that the FS5
receiver can output data by counting the
blinks of a single LED. As part of the entire
flight system, FMA Direct also offers a
Flight Systems Receiver Viewer Software
package. It consists of a PC interface module
(part FSIM1) that connects between the FS5
receiver (Channel 1 port) and the serial port
on a PC.
For added convenience, a nine-pin-tonine-
pin serial cable is provided, which will
extend the distance between the interface
module and the PC. Along with this, you get
a CD containing the viewer software
program itself. The software is intended for
PCs with Windows 98 or a later version of
Windows, along with Internet Explorer 6.0 or
later.
Since the data is only stored while the
power is still applied to the receiver, it is
assumed that you will use a laptop-type
portable computer and download the data at
the flying field, unless you are doing your
own testing within the confines of your home
shop.
I won’t get any further into the FS5’s details
in this review. The previously referenced
white paper will provide much more
information. The FMA Direct Web site
provides component and system part
numbers and prices.
The key thing to remember is that first
and foremost, you are getting an excellent
new RC receiver. It is lightweight and small.
That makes it suitable for indoor and parking
lot RC, the largest 1⁄4-scale models, and
more!
It is of dual-conversion circuitry, featuring
excellent sensitivity, selectivity, and the
ability to reject second- and third-order
intermodulation situations. All these features,
along with programmable fail-safe, are
essentially available right out of the box.
To gain these features, you do not need
the computer interface or the Co-Pilot selfstabilizing
system, but these extras are
available as options when you feel you need
them or want to try them. MA
Manufacturer:
FMA Direct Inc.
5716A Industry Ln.
Frederick MD 21704
Sales: (800) 343-2934
Technical: (301) 668-7614
Edition: Model Aviation - 2004/11
Page Numbers: 58,60,62,64
58 MODEL AVIATION
FMA DIRECT’S Flight Systems 5 (FS5) is a
new concept in RC receiver circuit design.
Although the company does offer complete
RC systems (transmitter, receiver, servos,
batteries, etc.), one of its primary product
lines for many years has been what are called
“aftermarket” RC receivers. They have been
designed so that almost any FM (also known
as Pulse Position Modulation, or PPM)
transmitter on the market can operate them.
Most RC transmitters employing a
microcomputer chip can provide model
memory or data storage for four, six, seven,
eight, and more aircraft. The idea is that you
need only one transmitter, and that unit is
capable of operating as many as eight
Te c h n i c a l R e v i e w Bob Aberle
E-mail: [email protected]
Besides FS5 receiver, system includes external switch/LED assembly, PC interface
module, and CD containing special viewer software program information.
Receiver with remote switch and LED assembly which allows you
to extend switch/LED function to outside model’s fuselage.
Close-up of FMA Co-Pilot control unit that goes inside an aircraft.
This device was reviewed in the August 2002 MA.
receivers and more in different aircraft. FMA
Direct has made a business of supplying these
individual (or extra) receivers to the RC
enthusiast.
The FS5 is the company’s newest
aftermarket RC receiver. It is small,
measuring 15⁄8-inch long, 13⁄16-inch wide, 9⁄16-
inch high, and weighing a mere .4 ounce. It
employs FM dual-conversion circuitry. The
current model has five channel functions, but
an eight-channel-capable version will be
available soon.
You must purchase the operating crystal
separately from FMA Direct. The FS5
receiver—part 905FM72—has a retail price
of $99.95. The crystal—part RXQTM72-XX
(where “XX” is the channel number)—is an
additional $12.95.
The FS5 is also a universal receiver, in the
sense that it can operate with high or low FM
deviation automatically. So whether you have
Futaba or Hitec on the high side or JR or
Airtronics on the low side, you will be able to
operate this unit.
Probably one of the FS5 receiver’s most
distinctive features is a new concept called
“Digital Signal Recognition” (DSR). This
proprietary circuit allows the receiver to
measure and store your RC transmitter’s
unique characteristics. Then throughout a
flight, this DSR circuit continuously compares
the incoming signals against your
transmitter’s stored “signature.” The claim is
that the DSR rejects signals from sources
other than your transmitter.
I tried to verify that claim by placing a
second RC transmitter nearby, operating on
the same frequency (channel number). How
60 MODEL AVIATION
close that interfering transmitter was to the
operating transmitter made a difference in the
final outcome.
Close by, the FS5 sensed massive
interference and went into fail-safe. At a
distance from the operating transmitter, I was
able to obtain control of the aircraft while the
DSR circuit was obviously working hard to
maintain the primary control. In this regard,
the FS5 offers a significant amount of
protection against even direct on-channel
interference.
As you will learn in this review, the FS5
receiver is part of an overall system
containing many features that can benefit the
RC flier and promote safety at the same time.
With all of the features together, you end up
with a moderately complex system operation.
If you read the excellent 22-page
document “The FMA Flight System: New
technologies for protecting RC aircraft” (go to
www.fmadirect.com/site/fma.htm?body=Sup
port, scroll down to “Technical Documents,”
and then select “FMA Flight Systems White
An up-close look at the switch/LED
assembly. This is an optional item that
Infrared sensor module portion of Co- you must purchase separately.
Pilot that is usually mounted on top of
wing or bottom of fuselage, where it can
view out front and sides.
On component side of the FS5 receiver,
knife blade points to the push-button
switch that is referenced in the text.
Remote switch/LED assembly cable plugs
into socket on FS5 below switch button.
External switch/LED then parallel same
items mounted on receiver PC board.
Bob’s Playboy Sr. test model. Switch button and LED are mounted
on fuselage side. Li-Poly pack is mounted below motor.
Remote switch/LED assembly mounted
on typical model fuselage. This way you
can push switch button and observe
glowing LED from outside of fuselage.
Co-Pilot’s two major parts. System can be integrated into FS5 so
model will always be righted or guided to level flight.
Paper”), you might feel that this system is too
much for you. Don’t get scared way!
If you purchase only the FS5 receiver and
install it in your model, as you would any
other RC receiver, you will come out ahead.
The rest of the features, such as setting up
fail-safe positions, knowing when interference
strikes your receiver, retrieving stored control
Photos by the author
data on a personal computer (PC), and even
integrating the FMA Co-Pilot selfstabilizing
device into the system, can be
added later, as you gain experience or get
curious!
Let’s say you bought an FS5 receiver. What
benefits would you derive by installing it in
your aircraft?
The FS5 provides all the fail-safe
features that can normally only be obtained
from an expensive Pulse Code Modulation
(PCM) RC system; now you can obtain
those same fail-safe features with your
regular FM RC system just by employing
the FS5 receiver.
The way this works, if your model is inflight
and interference is received from
another RC system (at your field or nearby),
is that all the primary controls (aileron,
elevator, rudder, and throttle) on your
model will be held (frozen) at their last
known positions before receiving the
interference. They won’t jitter around or go
hard over when that interference is received.
Another scenario might be an out-ofrange
situation in which the aircraft goes
too far away and the signal is lost. Again,
the controls lock up on the last known
position. That same situation might occur if
your transmitter dropped out of service in
flight (unlikely!) or if the transmitter battery
ran out of charge or failed. Any radio-signal
loss also prompts all the controls to freeze
at their last known position.
I know exactly what you are going to say
at this point! “If my aircraft is in a turn or a
dive at the moment interference is received
and the controls freeze, it is surely going to
head right for the ground and likely at full
power.”
That may be true because you can’t
predict a particular attitude at any given
time during a flight. So now comes the next
feature; the FS5 will allow you to program
preset control positions for each of the four
primary flight controls, as well as the
auxiliary (fifth) channel.
You might set the controls for a slight
amount of up-elevator, a bit of right rudder
and/or right aileron, and low speed or idle
speed on the engine/motor. Then if
interference is received or the transmitter
signal is lost, all of the controls will
immediately go to these preprogrammed
positions. These presets will remain in the
receiver’s memory even after the power is
turned off. They won’t change until you
change them.
Admittedly, the aircraft might be in a
banking or diving attitude when the fail-safe
kicks in. Even though you have the controls
set for engine low and a slight climbing
turn, it might not be enough to level the
model, and, as a result, a crash can still
happen.
The hope is that the preprogrammed
control positions will keep your airplane in
the air until the interference clears. In many
cases that may only be a few seconds in real
time; but just to provide added safety, FMA
Direct has taken that extra step to integrate
its popular Co-Pilot self-stabilizing system
into the FS5.
Therefore, if interference occurs in
flight, the fail-safe operates to its preset
controls and the Co-Pilot will stabilize the
aircraft back to straight and level flight. If
you are interested, I reviewed the FMA
Direct Co-Pilot in the August 2002 MA
(pages 77-79).
Since setting the fail-safe preset control
positions is important, I’ll take you through
how easy it is to do. Before I begin, you
need to know that on the component side of
the FS5 receiver is a push-button switch and
an LED that glows a bright orange or red
when it’s on. That switch button and the
LED allow you to program the control
positions. They also let you use many other
receiver features, which I will get into later.
Because the receiver will more than
likely be inside your aircraft’s fuselage,
having access to the switch and the LED
could be a problem. To rectify that, FMA
Direct has come up with a remote switch and
LED (part FSRES1) that has a cable that
plugs into a connector on the receiver. You
can mount the switch/LED assembly on a
fuselage side, top, or bottom, so that the
LED is visible and you can operate the
switch from the outside of the aircraft. I
chose this option, as shown, and it makes
total sense!
To set up a preset fail-safe control
position, turn on your transmitter and make
sure that all three primary control functions
(aileron, elevator, and rudder) have their
sticks in the neutral position and that the
throttle stick is in the low or idle position.
Depress the switch button, and while holding
the button down, turn on the receiver power.
Let go of the button and the LED will begin
to “twinkle” (flash extremely fast).
Let’s say you want to preset up-elevator.
Using the transmitter elevator control stick,
apply some up-elevator. While holding that
position, press the button (on the side of the
fuselage) once and then immediately let go of
the elevator stick so that it springs back to
neutral. When you turn the receiver power
off, you will have left the setup mode, and the
elevator preset will be stored for good in the
receiver memory.
To make sure you did this correctly,
power up the receiver with the transmitter on.
Move the control sticks, and you should note
normal control. Turn off the transmitter
(simulating loss of signal), and the elevator
should move to your preset fail-safe position.
Turning the transmitter back on, your controls
go back to neutral and work in a normal
manner. You should experience the same
reaction if interference hits your FS5 receiver.
But beyond the fail-safe operation and the
fail-safe preset control capabilities, there are
many other features in the FMA FS5
receiver’s operation. When at the flying field,
you can turn on the receiver, leaving the
transmitter off, and watch the LED. If you see
one blink, it means your frequency is clear
and you can proceed to fly.
A continuous series of blinks means that
your receiver just experienced some form of
interference and you best investigate before
attempting to fly your model. Someone may
already be flying on your channel and forgot
to take the frequency control clip.
A bonus is that you can read your receiver
battery’s voltage by counting blinks on the
LED. Press the button once. The LED will
provide a long blink for every 1.0 volt and a
short blink for every 0.1 volt. Therefore, four
long blinks and nine short blinks would be
4.9 volts.
The FS5 will also let you know, after a
flight, if the fail-safe activated for any reason
during the flight. After landing, keep the
transmitter and receiver on. Immediately
observe the LED. If it glows a solid or steady
orange/red color, you did not experience any
interference. If it blinks, you experienced failsafe
during that particular flight. You can
count the number of blinks to determine how
many times the receiver went into fail-safe.
After observing that condition, you can
read the number of “bad frames” that
occurred during the flight if you press the
button three times. Thus you have a
sophisticated and highly accurate “glitch
counter.”
I learned that it takes 50 consecutive bad
frames before the receiver enters fail-safe. So
it is possible to have experienced something
such as 30 bad frames in a flight and still not
enter fail-safe. Keep in mind that when you
turn the power off, you lose that saved data
from the last flight.
You can also use the FS5 to help you
range-check your entire RC system. You
traditionally perform the ground range test by
collapsing the transmitter antenna (to reduce
its power) and having someone walk away
with the transmitter while continuously
operating one channel control, such as
elevator.
Have the person walk out the distance the
RC manufacturer recommends; let’s say it’s
100 feet. With the transmitter and receiver
power still on, observe the LED. If it is not
blinking, you have a perfect range test. If it is
blinking, the number of blinks indicates the
number of “bad frames” you received during
the test.
If that happens, you will have to explore
the usual possibilities, such as equipment
problems or an antenna placed too close to a
noise-generating component such as a servo!
The LED gives you an exact measure of what
is going on!
So far you have learned that the FS5
receiver can output data by counting the
blinks of a single LED. As part of the entire
flight system, FMA Direct also offers a
Flight Systems Receiver Viewer Software
package. It consists of a PC interface module
(part FSIM1) that connects between the FS5
receiver (Channel 1 port) and the serial port
on a PC.
For added convenience, a nine-pin-tonine-
pin serial cable is provided, which will
extend the distance between the interface
module and the PC. Along with this, you get
a CD containing the viewer software
program itself. The software is intended for
PCs with Windows 98 or a later version of
Windows, along with Internet Explorer 6.0 or
later.
Since the data is only stored while the
power is still applied to the receiver, it is
assumed that you will use a laptop-type
portable computer and download the data at
the flying field, unless you are doing your
own testing within the confines of your home
shop.
I won’t get any further into the FS5’s details
in this review. The previously referenced
white paper will provide much more
information. The FMA Direct Web site
provides component and system part
numbers and prices.
The key thing to remember is that first
and foremost, you are getting an excellent
new RC receiver. It is lightweight and small.
That makes it suitable for indoor and parking
lot RC, the largest 1⁄4-scale models, and
more!
It is of dual-conversion circuitry, featuring
excellent sensitivity, selectivity, and the
ability to reject second- and third-order
intermodulation situations. All these features,
along with programmable fail-safe, are
essentially available right out of the box.
To gain these features, you do not need
the computer interface or the Co-Pilot selfstabilizing
system, but these extras are
available as options when you feel you need
them or want to try them. MA
Manufacturer:
FMA Direct Inc.
5716A Industry Ln.
Frederick MD 21704
Sales: (800) 343-2934
Technical: (301) 668-7614
Edition: Model Aviation - 2004/11
Page Numbers: 58,60,62,64
58 MODEL AVIATION
FMA DIRECT’S Flight Systems 5 (FS5) is a
new concept in RC receiver circuit design.
Although the company does offer complete
RC systems (transmitter, receiver, servos,
batteries, etc.), one of its primary product
lines for many years has been what are called
“aftermarket” RC receivers. They have been
designed so that almost any FM (also known
as Pulse Position Modulation, or PPM)
transmitter on the market can operate them.
Most RC transmitters employing a
microcomputer chip can provide model
memory or data storage for four, six, seven,
eight, and more aircraft. The idea is that you
need only one transmitter, and that unit is
capable of operating as many as eight
Te c h n i c a l R e v i e w Bob Aberle
E-mail: [email protected]
Besides FS5 receiver, system includes external switch/LED assembly, PC interface
module, and CD containing special viewer software program information.
Receiver with remote switch and LED assembly which allows you
to extend switch/LED function to outside model’s fuselage.
Close-up of FMA Co-Pilot control unit that goes inside an aircraft.
This device was reviewed in the August 2002 MA.
receivers and more in different aircraft. FMA
Direct has made a business of supplying these
individual (or extra) receivers to the RC
enthusiast.
The FS5 is the company’s newest
aftermarket RC receiver. It is small,
measuring 15⁄8-inch long, 13⁄16-inch wide, 9⁄16-
inch high, and weighing a mere .4 ounce. It
employs FM dual-conversion circuitry. The
current model has five channel functions, but
an eight-channel-capable version will be
available soon.
You must purchase the operating crystal
separately from FMA Direct. The FS5
receiver—part 905FM72—has a retail price
of $99.95. The crystal—part RXQTM72-XX
(where “XX” is the channel number)—is an
additional $12.95.
The FS5 is also a universal receiver, in the
sense that it can operate with high or low FM
deviation automatically. So whether you have
Futaba or Hitec on the high side or JR or
Airtronics on the low side, you will be able to
operate this unit.
Probably one of the FS5 receiver’s most
distinctive features is a new concept called
“Digital Signal Recognition” (DSR). This
proprietary circuit allows the receiver to
measure and store your RC transmitter’s
unique characteristics. Then throughout a
flight, this DSR circuit continuously compares
the incoming signals against your
transmitter’s stored “signature.” The claim is
that the DSR rejects signals from sources
other than your transmitter.
I tried to verify that claim by placing a
second RC transmitter nearby, operating on
the same frequency (channel number). How
60 MODEL AVIATION
close that interfering transmitter was to the
operating transmitter made a difference in the
final outcome.
Close by, the FS5 sensed massive
interference and went into fail-safe. At a
distance from the operating transmitter, I was
able to obtain control of the aircraft while the
DSR circuit was obviously working hard to
maintain the primary control. In this regard,
the FS5 offers a significant amount of
protection against even direct on-channel
interference.
As you will learn in this review, the FS5
receiver is part of an overall system
containing many features that can benefit the
RC flier and promote safety at the same time.
With all of the features together, you end up
with a moderately complex system operation.
If you read the excellent 22-page
document “The FMA Flight System: New
technologies for protecting RC aircraft” (go to
www.fmadirect.com/site/fma.htm?body=Sup
port, scroll down to “Technical Documents,”
and then select “FMA Flight Systems White
An up-close look at the switch/LED
assembly. This is an optional item that
Infrared sensor module portion of Co- you must purchase separately.
Pilot that is usually mounted on top of
wing or bottom of fuselage, where it can
view out front and sides.
On component side of the FS5 receiver,
knife blade points to the push-button
switch that is referenced in the text.
Remote switch/LED assembly cable plugs
into socket on FS5 below switch button.
External switch/LED then parallel same
items mounted on receiver PC board.
Bob’s Playboy Sr. test model. Switch button and LED are mounted
on fuselage side. Li-Poly pack is mounted below motor.
Remote switch/LED assembly mounted
on typical model fuselage. This way you
can push switch button and observe
glowing LED from outside of fuselage.
Co-Pilot’s two major parts. System can be integrated into FS5 so
model will always be righted or guided to level flight.
Paper”), you might feel that this system is too
much for you. Don’t get scared way!
If you purchase only the FS5 receiver and
install it in your model, as you would any
other RC receiver, you will come out ahead.
The rest of the features, such as setting up
fail-safe positions, knowing when interference
strikes your receiver, retrieving stored control
Photos by the author
data on a personal computer (PC), and even
integrating the FMA Co-Pilot selfstabilizing
device into the system, can be
added later, as you gain experience or get
curious!
Let’s say you bought an FS5 receiver. What
benefits would you derive by installing it in
your aircraft?
The FS5 provides all the fail-safe
features that can normally only be obtained
from an expensive Pulse Code Modulation
(PCM) RC system; now you can obtain
those same fail-safe features with your
regular FM RC system just by employing
the FS5 receiver.
The way this works, if your model is inflight
and interference is received from
another RC system (at your field or nearby),
is that all the primary controls (aileron,
elevator, rudder, and throttle) on your
model will be held (frozen) at their last
known positions before receiving the
interference. They won’t jitter around or go
hard over when that interference is received.
Another scenario might be an out-ofrange
situation in which the aircraft goes
too far away and the signal is lost. Again,
the controls lock up on the last known
position. That same situation might occur if
your transmitter dropped out of service in
flight (unlikely!) or if the transmitter battery
ran out of charge or failed. Any radio-signal
loss also prompts all the controls to freeze
at their last known position.
I know exactly what you are going to say
at this point! “If my aircraft is in a turn or a
dive at the moment interference is received
and the controls freeze, it is surely going to
head right for the ground and likely at full
power.”
That may be true because you can’t
predict a particular attitude at any given
time during a flight. So now comes the next
feature; the FS5 will allow you to program
preset control positions for each of the four
primary flight controls, as well as the
auxiliary (fifth) channel.
You might set the controls for a slight
amount of up-elevator, a bit of right rudder
and/or right aileron, and low speed or idle
speed on the engine/motor. Then if
interference is received or the transmitter
signal is lost, all of the controls will
immediately go to these preprogrammed
positions. These presets will remain in the
receiver’s memory even after the power is
turned off. They won’t change until you
change them.
Admittedly, the aircraft might be in a
banking or diving attitude when the fail-safe
kicks in. Even though you have the controls
set for engine low and a slight climbing
turn, it might not be enough to level the
model, and, as a result, a crash can still
happen.
The hope is that the preprogrammed
control positions will keep your airplane in
the air until the interference clears. In many
cases that may only be a few seconds in real
time; but just to provide added safety, FMA
Direct has taken that extra step to integrate
its popular Co-Pilot self-stabilizing system
into the FS5.
Therefore, if interference occurs in
flight, the fail-safe operates to its preset
controls and the Co-Pilot will stabilize the
aircraft back to straight and level flight. If
you are interested, I reviewed the FMA
Direct Co-Pilot in the August 2002 MA
(pages 77-79).
Since setting the fail-safe preset control
positions is important, I’ll take you through
how easy it is to do. Before I begin, you
need to know that on the component side of
the FS5 receiver is a push-button switch and
an LED that glows a bright orange or red
when it’s on. That switch button and the
LED allow you to program the control
positions. They also let you use many other
receiver features, which I will get into later.
Because the receiver will more than
likely be inside your aircraft’s fuselage,
having access to the switch and the LED
could be a problem. To rectify that, FMA
Direct has come up with a remote switch and
LED (part FSRES1) that has a cable that
plugs into a connector on the receiver. You
can mount the switch/LED assembly on a
fuselage side, top, or bottom, so that the
LED is visible and you can operate the
switch from the outside of the aircraft. I
chose this option, as shown, and it makes
total sense!
To set up a preset fail-safe control
position, turn on your transmitter and make
sure that all three primary control functions
(aileron, elevator, and rudder) have their
sticks in the neutral position and that the
throttle stick is in the low or idle position.
Depress the switch button, and while holding
the button down, turn on the receiver power.
Let go of the button and the LED will begin
to “twinkle” (flash extremely fast).
Let’s say you want to preset up-elevator.
Using the transmitter elevator control stick,
apply some up-elevator. While holding that
position, press the button (on the side of the
fuselage) once and then immediately let go of
the elevator stick so that it springs back to
neutral. When you turn the receiver power
off, you will have left the setup mode, and the
elevator preset will be stored for good in the
receiver memory.
To make sure you did this correctly,
power up the receiver with the transmitter on.
Move the control sticks, and you should note
normal control. Turn off the transmitter
(simulating loss of signal), and the elevator
should move to your preset fail-safe position.
Turning the transmitter back on, your controls
go back to neutral and work in a normal
manner. You should experience the same
reaction if interference hits your FS5 receiver.
But beyond the fail-safe operation and the
fail-safe preset control capabilities, there are
many other features in the FMA FS5
receiver’s operation. When at the flying field,
you can turn on the receiver, leaving the
transmitter off, and watch the LED. If you see
one blink, it means your frequency is clear
and you can proceed to fly.
A continuous series of blinks means that
your receiver just experienced some form of
interference and you best investigate before
attempting to fly your model. Someone may
already be flying on your channel and forgot
to take the frequency control clip.
A bonus is that you can read your receiver
battery’s voltage by counting blinks on the
LED. Press the button once. The LED will
provide a long blink for every 1.0 volt and a
short blink for every 0.1 volt. Therefore, four
long blinks and nine short blinks would be
4.9 volts.
The FS5 will also let you know, after a
flight, if the fail-safe activated for any reason
during the flight. After landing, keep the
transmitter and receiver on. Immediately
observe the LED. If it glows a solid or steady
orange/red color, you did not experience any
interference. If it blinks, you experienced failsafe
during that particular flight. You can
count the number of blinks to determine how
many times the receiver went into fail-safe.
After observing that condition, you can
read the number of “bad frames” that
occurred during the flight if you press the
button three times. Thus you have a
sophisticated and highly accurate “glitch
counter.”
I learned that it takes 50 consecutive bad
frames before the receiver enters fail-safe. So
it is possible to have experienced something
such as 30 bad frames in a flight and still not
enter fail-safe. Keep in mind that when you
turn the power off, you lose that saved data
from the last flight.
You can also use the FS5 to help you
range-check your entire RC system. You
traditionally perform the ground range test by
collapsing the transmitter antenna (to reduce
its power) and having someone walk away
with the transmitter while continuously
operating one channel control, such as
elevator.
Have the person walk out the distance the
RC manufacturer recommends; let’s say it’s
100 feet. With the transmitter and receiver
power still on, observe the LED. If it is not
blinking, you have a perfect range test. If it is
blinking, the number of blinks indicates the
number of “bad frames” you received during
the test.
If that happens, you will have to explore
the usual possibilities, such as equipment
problems or an antenna placed too close to a
noise-generating component such as a servo!
The LED gives you an exact measure of what
is going on!
So far you have learned that the FS5
receiver can output data by counting the
blinks of a single LED. As part of the entire
flight system, FMA Direct also offers a
Flight Systems Receiver Viewer Software
package. It consists of a PC interface module
(part FSIM1) that connects between the FS5
receiver (Channel 1 port) and the serial port
on a PC.
For added convenience, a nine-pin-tonine-
pin serial cable is provided, which will
extend the distance between the interface
module and the PC. Along with this, you get
a CD containing the viewer software
program itself. The software is intended for
PCs with Windows 98 or a later version of
Windows, along with Internet Explorer 6.0 or
later.
Since the data is only stored while the
power is still applied to the receiver, it is
assumed that you will use a laptop-type
portable computer and download the data at
the flying field, unless you are doing your
own testing within the confines of your home
shop.
I won’t get any further into the FS5’s details
in this review. The previously referenced
white paper will provide much more
information. The FMA Direct Web site
provides component and system part
numbers and prices.
The key thing to remember is that first
and foremost, you are getting an excellent
new RC receiver. It is lightweight and small.
That makes it suitable for indoor and parking
lot RC, the largest 1⁄4-scale models, and
more!
It is of dual-conversion circuitry, featuring
excellent sensitivity, selectivity, and the
ability to reject second- and third-order
intermodulation situations. All these features,
along with programmable fail-safe, are
essentially available right out of the box.
To gain these features, you do not need
the computer interface or the Co-Pilot selfstabilizing
system, but these extras are
available as options when you feel you need
them or want to try them. MA
Manufacturer:
FMA Direct Inc.
5716A Industry Ln.
Frederick MD 21704
Sales: (800) 343-2934
Technical: (301) 668-7614