Project Extra Volume VI: Setup and Flight Preparation

May 2003 63
Setup and Flight
Preparation
Volume VI:
ON A RECENT trip to the local flying field, one of the members had
brought his latest project, shiny and new, ready for the initial test
flight. I watched as he and his buddies began to go over the aircraft,
checking this and checking that. They adjusted the servo throw, and
two or three guys started to remove pieces from the airplane while
others made adjustments. Soon there was a large crowd around the
airplane. After some time it was determined that the owner needed to
take the airplane back home for some finishing before it could be
flown.
Sound familiar? You might have seen this happen at one time or
another. This particular flier was not a novice pilot; he had years of
experience and was considered by many to be one of the best pilots in
the area. Yet he came to the field with the intention of flying an
unprepared and untested aircraft with the idea that a few last-minute
items would be no big deal once he was there.
Come on! Don’t go to the field and install your servos! Make all of
your last-minute adjustments in the workshop and be 100% prepared
to fly when you leave your shop. It’s important to fully finish and
ready any aircraft before it goes to the field, but it is especially
■ Mike Hurley
important with an aircraft the size of the 35% Extra 300LX.
If you need the help of others in your club, ask those who you know
have the experience you need rather than taking the chance on whoever
may be present the day you go out for the initial flight. Get the help
you need and test every aspect of your airplane, then you can be
confident that you’re ready when you finally do get to that first flight.
Setup: Volume VI is the last installment of Project Extra and it will
help you get started with the process of setting up your airplane, but the
final outcome is entirely in your hands. No one can tell you exactly
how to set up your model to work just right for your personal
preferences. In fact, Erik Richards and I will be setting up two separate
programs/models on his radio for this Extra—one for his style of flying
and one for mine. Our preferences and styles are that different. Only
you know how you like your airplane to fly and feel.
Anyone setting up an aircraft of this size and caliber should have
plenty of experience with final adjustments by the time he or she gets
to this model. One of the last things to think about before flying an
airplane equipped with a gasoline engine (that you may not do with the
Erik Richard (standing) and Mike Hurley show off their completed Extra 300LXs. Erik’s is the one built throughout the
course of the construction articles.
June 2003 64
smaller models) is to Loctite all of the metalto-
metal hardware that does not need field
assembly. Use thread locker that is made for
hand-tool removal. That usually means the
blue formula, but check the label.
I’m assuming that you know about basic
preflight and finishing procedures for a new
aircraft: installing, charging, and checking
your batteries, sealing any exposed wood in
the engine compartment, range checking, and
other procedures common to modeling, so I
won’t go into those steps. But you know as an
experienced modeler that all of those things
are important for a successful aircraft. Again,
if you have questions, get help from someone
who has the experience. There’s a terrific
article on range checking at http://horizon.
hobbyshopnow.com/articles/1079.asp.
In this issue we’ll look at basic
programming for the Extra so that all of the
servos work together and you have some idea
of how to set up a large aerobatic airplane. I’ll
give you some guidelines for balance and
control throws and discuss standard trimming
for a precision aircraft. I’ll use the JR 10X
radio for the examples because that’s what I
use, but you can do most of these things with
any of today’s computer radios.
Refer to your transmitter’s instruction
manual, and remember that many functions
that perform the same tasks are referred to
with different names by the different
manufacturers. Each of these topics could
encompass an entire article in itself, so I’ll be
limited to the basics. You’ll want to expand
the information on your own with a little
experimentation, practice, and some help from
your friends. Another source of information
on how to set up an aerobatic airplane is
http://horizon.hobbyshopnow.com/articles/11
69.asp. Click on the PDF download for the
whole article.
Mixing: If you followed our plan for Project
Extra, the airplane uses two rudder servos
ganged inline and connected to a bellcrank for
the pull-pull system. I like to match my rudder
servos utilizing a multipoint mix in my
transmitter. Even with four servos on the
rudder of my 40% models, I match two sets of
two servos with MatchBoxes then use a
multipoint mix to match the two pairs.
With the JR 10X the two servos are
plugged into separate channels: Rudder and
Aux2. Since the servos will be hard connected
to each other, it’s important that each servo’s
full range of motion matches perfectly.
A multipoint mix has the advantage over
other methods, including MatchBoxes, in that
there are as many as five positions that can be
adjusted, and you can tailor the mixing points
to just those spots that need attention. For the
servo/bellcrank arrangement, first adjust the
linkages between the aft servo and the
bellcrank. As we discussed in Volume IV of
this series, the linkages must be centered and
run parallel to each other so that they have
equal movement without binding. Check that
there is no binding in any movement before
you power up any servos.
It’s also a good idea to have any servo
arms and linkages removed before powering
up a servo for the first time. We found some
interference between the ball link and the
bellcrank and had to add some washers to the
inside of the connection to spread the arms
slightly and make clearance. The bind was
not visually evident, and we wouldn’t have
found this problem if the servos had been
powered up.
Once the movement is clean, you can
install the second set of linkages, but don’t
connect them to the second servo arm just
yet. I like to adjust the linkage so I can see
the connection point looking through the hole
in the ball links. Then with the transmitter,
move through the travel and note where the
ball doesn’t follow the connection point
precisely. I usually adjust the endpoints and
neutral first. Most of the time that’s all that’s
needed, but if there are places during
transition that do not line up, create an
adjustment point and line it up. Bolt it up,
and you’re ready to hook the cables to the
rudder.
Follow the same basic procedures with
the ailerons, but the mix is done using the
MatchBox. The instructions that come with
the MatchBox are clear, and the procedure is
simple. The 10X has a preprogrammed mix
for dual elevators, and we used flaperons for
the ailerons so that differential mixing was
available if needed. I’ll write more about that
later.
Before we get to the point of setting up
any part of the radio, we need to ensure that
all of the controls are working in the correct
direction—especially the ailerons. Don’t go
any further until everything is correct!
Standing behind the airplane looking at it as
if it were flying away, move the aileron stick
left; the left aileron should be up and the right
aileron should be down. Move the stick right,
and the right aileron is up and the left aileron
is down. Do it now; don’t wait ’til later.
Control Throws: Here’s where things can
get sticky and settings will really vary with
each pilot’s personal abilities and
preferences. I use JR’s flight modes to
Field assembly is rather straightforward. Slide the wings onto the wing tube. Hook up
the servos. Fasten the wing to the fuselage, and bolt on the hatch.
With the proper setup and some practice, this Extra excels at 3-D maneuvers. Note the
extreme 45° elevator deflection.
June 2003 65
When ganging two servos for rudder pull-pull system, bolt one
end of control rod to servo arm; leave other open for alignment.
Make sure that your servos are correctly centered before you
make any adjustments. Erik used a set of dial calipers.
Be very careful to always check for correct control-surface
directions before the airplane leaves your shop.
Erik and Mike used a CRC deflection gauge to ensure the
desired (and equal) amount of deflection on both sides.
To ensure that the elevator deflection is equal in the center and
at its maximum endpoints, Erik used a set of carbon rods taped
to each elevator half as a pointer.
control all of my rates with a single switch. For me, using flight
modes helps me avoid confusion.
However, you should set up your radio close to the manner with
which you are most comfortable. After you get more comfortable with
the airplane, you can experiment with new switches and rate types,
such as flight modes. If you’re fairly new to 3-D, be sure to have a
quick and easy way to escape the 3-D setting, and never fly a new
model that does not have the option for a reduced-rate elevator.
For starters, let’s set up the Extra with two sets of control rates.
The elevator is the control that can get you into a lot of trouble fast, so
I’ll concentrate on that. We’ll have a standard rate for everyday flying,
which can be later optimized for precision, and a setting for maximum
control throw, which is the 3-D mode.
Setting surface deflection is another initial step where so many
pilots tend to rely on the TLAR (“that looks about right”) method. But
really, this stuff is critical to an airplane that flies in a neutral manner
and won’t fight your every input. For control setup I use CRC Throw
Meters to tell me, in degrees, exactly where the control surfaces are
set. The CRC gauges are available from Central Hobbies at
www.centralhobbies.com/.
One often-overlooked step in setup is matching aileron throw left
The Project Extra series is presented on the
AMA Web site at www.modelaircraft.org.
to right and up and down. It’s nice to have
two gauges for matching ailerons. Before
you adjust throw, match the neutral and
endpoints for the ailerons. I make these
adjustments at maximum deflection or 100%
travel. Then as you adjust the total throws or
rate settings, the control surfaces should stay
in sync.
To make sure the elevators are in sync,
Erik likes to use a 24-inch length of carbon
tubing taped to each elevator half as a
pointer. The carbon rod is stiff and does not
flex at this long length, so it stays accurate.
Line up the elevators at the counterbalances
to make sure they’re level, then tape the
tubes to the surface so that they point directly
to each other when centered. Erik used a
toothpick in the end of each tube for further
accuracy.
Move the surfaces slowly and watch for
differences along the length of travel; some
offset as the elevators move is normal. The
pointers are so long that a fairly large gap of,
say, a half inch only reflects a minute offset,
so don’t get too worried unless the
differences are huge. With the transmitter
you can now adjust the endpoints to match
perfectly at the extremes of each throw, and
you are assured of even elevator adjustment.
For the beginning setup and initial flight
testing, set the ailerons to 15° of throw each
way and the elevators to 20° each way. To
set the rudder, you must turn the fuselage on
its side with the wings and stabilizers
66 MODEL AVIATION
removed from the airplane. Initially set the
rudder to 35° each way. After you get
comfortable with the model, readjust all of the
deflections and settings to suit your flying
style.
The Dead Zone: Before we get into the setup
for 3-D, let’s discuss flying with huge throws
and some of the things to understand before
you try flying with 3-D throws the first time.
With a little bit of exponential, or “expo,” and
some experience, this Extra can be flown with
any amount of control throw. I fly mine on
full maximum 3-D rate all the time. That
includes takeoff, landing, and everything in
between. The only time I switch out of 3-D is
to fly a precision flight where I want more
exacting control of the airplane.
For a while I was starting to think that the
model couldn’t be induced to snap with
elevator alone and that anyone could fly it in
3-D mode, but I was brought back to reality
when I let a friend fly the airplane. My friend
was an experienced pilot who I trusted
completely, but he had never flown an
airplane set up for 3-D.
At first when I handed him the transmitter
set to precision rates, he had a ball doing
rolling loops, knife-edge circles, and multiple
snaps; you name it, and he was doing it! He
became comfortable with the airplane and
started to try some of the 3-D stuff that he had
seen me do. “You can’t do those things in low
rate,” I said. “I’ll switch to 3-D for you.” I hit
the switch, and the smile on his face started to
relax; he was beginning to look worried.
Suddenly just controlling the airplane
through a loop was difficult, and he snapped
the model without provocation within a
couple of seconds. “Shut it off!” he yelled,
and I hit the switch back to low rate. That
episode made me realize that, without
knowing it, I had become used to flying the
Extra in a manner that worked with extreme
surface deflection, but the model could still be
a handful to pilots who are just learning 3-D.
Don’t get caught in the trap. Some of you
may read the preceding account and think to
yourself, I’ll just tone it down a bit by
Defying the Limits
Learning to fly 3-D maneuvers is fun
and satisfying, and the Project Extra
model is a great aircraft with which to
learn 3-D. Another advantage is to gather
information to help you get started. If
you’d like to learn more about high-alpha
flight, 3-D maneuvers, aircraft
preparation, equipment, and setup,
Robin’s View Productions has released a
video called Defying the Limits, featuring
world-renowned 3-D and precision pilot
Jason Shulman. I developed and filmed
the video.
Defying the Limits is available on
DVD with convenient searchable
chapters. For more information or to
order the video, contact Robin’s View
Productions at (610) 746-0106. MA
—Mike Hurley
68 MODEL AVIATION
reducing the control throw and work up to
more throw as I get comfortable. That’s
exactly what can get you into more trouble.
The secret to entering and exiting 3-D is
to have the pitch authority to power past a
stalled attitude and hold it with massive
surfaces, deflection, and a powerful
propeller blast. If you tone it down by
lowering the surface deflection and try the
maneuver, the airplane won’t have the
required pitch authority and will stall. I call
the lowered surface deflection “the dead
zone.” The dead zone is too low for 3-D
and too high for precision control. The dead
zone will get you into trouble in a hurry.
Flying 3-D: When flying the model,
remember that you need to be committed to
getting into and out of a high-alpha (HA)
attitude. It’s important to have enough
airspeed or power to transition into a high
angle of attack. I’ve noticed that people get
into trouble when they move too slowly
into the transition or don’t use enough
elevator deflection or engine power.
I’m not saying you need to perform 3-D
maneuvers with a higher airspeed, but if the
speed is low you must use the power from
your engine to move the airplane’s tail into
position. Indeed you can slow the model to
a stall as long as you keep inducing the
power needed to keep the tail below the
airplane. At that point you can transition
into a hover with no forward airspeed.
Inversely, you can transition into HA with
power off if you maintain the airspeed to
pop your model into position, but once in
position you need to power up to hold
altitude.
Learning to fly into and out of HA
safely is the beginning of learning to fly 3-
D; it’s not hard to do, but it takes a little
finesse. If you’re not getting it quite right,
the aircraft will let you know with a nice
wing drop or an all-out snap.
My recommendation, even if you’re
experienced, is to start slow and use the rate
switch. Have enough expo dialed in to keep
the airplane controllable, and only switch
into 3-D mode to execute a specific 3-D
maneuver, then switch back to low rate to
fly out. Set your elevator to 45° for 3-D
deflection. The dead zone for the elevator is
27-37°; try to avoid those settings. For the
ailerons, you can 3-D nicely at 25-30°
deflection, and the rudder should be 45°.
There is no dead zone for the rudder or
ailerons.
Remember that these rates can get you
into trouble fast and are not recommended
for beginning pilots. If you have to
significantly reduce the travel on your radio
from 100% to get the ailerons down to 30° of
deflection, I recommend moving the controlrod
mounting position on the servo arm
inboard toward the output shaft until you get
the desired deflection with the radio
programmed to 100%.
Exponential: Expo is a program on most
computer radios that allows you to adjust a
nonlinearity of the stick movement relative
to the servo arm output. In most cases
pilots use expo to soften the feel of the
stick around the neutral position, especially
when there is a lot of surface deflection. To
create a softer feel you are moving a
portion of the servo travel to a different
area of the stick deflection—in this case,
farther out in the travel. So the servo moves
less near the center of the stick position and
exponentially moves more as the stick moves
toward full travel.
Here’s a funny fact that shows a need for
standardization. With a JR radio you want to
dial in positive expo for a softer neutral area,
but a negative value is needed with Futaba.
Be sure to read your owner’s manual!
Because I can’t climb into your shoes, I
cannot give you a positive starting point for
setting expo on this airplane. You will need
to do it for yourself. The trick is to set a value
and try it. Change one setting at a time and
find the value that works best for you.
Following is what I have set on my Extra
at max 3-D deflection: aileron, +50%;
elevator, +55%; and rudder +30%. I have
expo for precision too, but it’s slightly
different; aileron is +30%, elevator is +30%,
and rudder is +40%.
You can see that my rudder expo is higher
for precision than for 3-D. That’s to try to
smooth out any rudder wobble while flying
precision maneuvers. You can really effect
some big changes with expo that can gain big
advantages by smoothing out your flying
around the center of the stick while allowing
a large amount of control deflection right at
your fingers if you need it. There’s also the
possibility of too much of a good thing, so be
careful and don’t numb out the center of
your radio’s stick completely. Once you’re
comfortable with the airplane, give it a try
and don’t be afraid to experiment.
Balance: The center of gravity (CG) located
on the plans is conservative, at
approximately 32% of the chord at the mean
aerodynamic center (MAC). I fly my
airplane at this forward position, and it
works great for 3-D and precision flying.
It’s safe to locate the CG anywhere between
F3 and the forward edge of the wing tube
socket. I feel that, within limits, CG
location can be a personal preference. Many
of the top pilots fly with a forward CG for
precision and move the CG aft for freestyle.
Some people believe that you must have
a rear-biased CG to perform any 3-D
maneuvers; that simply is not true. In some
3-D maneuvers a rearward CG will slightly
enhance the model’s performance, but in
most other flight attitudes the performance
will suffer. I prefer to lose a tiny amount of
3-D performance to keep the rest of the
aircraft’s integrity intact, yet with practice
I’m able to perform any 3-D maneuver.
Trimming: Decidedly, trimming your
airplane for neutral flight is the difference
between a model that flies well and one that
you fight to keep on track. Trimming a
model properly is also one of the most
overlooked steps in readying it for
competition. Hey, it flies pretty well right
off the blocks, so why spend so much time
on a few minor changes? It does take a bit
of time to get everything right. I’ve spent
almost 100 flights getting one of my
competition airplanes to where I wanted it.
No, it wasn’t a problem airplane; on the
contrary, it was fantastic, and that’s why I
knew it had so much potential to be close to
perfect.
Some of the things you want to look for
are the ability to fly precision up- and
down-lines, 45s, and loops without the need
for stick input. There are many good
trimming procedures and charts available
that can take you step by step through the
procedure, and I would most likely be
doing you a disservice if I tried to make a
condensed version here, so take a look
online. You can download a chart from the
National Society of Radio Controlled
Aerobatics at www.nsrca.org/
trimA.htm. While you’re at it, take a look at
the Web site; these are the people who lead
the way in precision aerobatics.
Common Mixes: Most Scale Aerobatics
(SA) airplanes have some form of unwanted
coupling to the rudder. In an ideal scenario,
rudder movement would impart yaw only,
but with many Scale aircraft the rudder will
also effect some roll and/or some pitch.
Those are things we do not want for
precision flying, so it’s a common practice to
create a mix to trim those attributes out.
After you’re comfortable with how the
airplane flies, you can start to add these
trimming mixes.
For the rudder coupling, check the trim
by flying the airplane in knife edge. Set the
mix by flying at an even medium speed with
only enough rudder to sustain level knifeedge
flight. Many of today’s computer
radios have special mixes just for this
trimming procedure. I believe that all of
JR’s computer radios from the 662 up to the
10X have this specific feature.
The rudder is always the master channel.
Aileron will be slaved for roll, and elevator
will be slaved for pitch. The amount of mix
depends on your model and a variety of
dynamic forces that can change, such as
atmospheric density, balance, airspeed,
servo power, and so on. So no matter how
well you dial in the mix, it will never be
100% foolproof, and your model will more
than likely be somewhat different from the
next flier’s.
It’s also quite common for the mix for
left rudder to be slightly different from the
mix for right rudder, so you will have to trim
those tendencies out one step at a time. Our
Extra does not have any roll coupling, but
Scale aerobatic airplanes will commonly
have a 2-4% mix. This model does tuck
slightly, so I have 10% up-elevator mixed
for left and right rudder. That number would
decrease with a more rearward balance. To
be conservative, start with approximately
5% up if it tucks to the gear or down if it
pulls to the canopy, and decide from that
point if you need more or less mix.
I like to put my mix on a switch so it
can be defeated if necessary. The switch
could be useful when performing rolling
maneuvers such as a slow roll or a rolling
circle, where you are flying through the
maneuver with all of the controls in sync,
but (to be honest!) I leave the switch on all
the time.
More Mixes: Other mixes that are common
to SA aircraft are a throttle curve and aileron
differential. I don’t use either of them with
my airplane, but I thought it prudent to
touch on them here.
A throttle curve is used to make the
engine power feel more linear through the
entire range of stick motion. Since
carburetor butterfly position does not
usually translate to engine rpm, most of the
change in power comes at the lower end of
the stick movement. You can set a curve to
give you a more even feel. Some people use
this for torque rolling if the throttle is too
touchy at the hovering rpm range. I had
throttle curves in all of my models when I
flew at sea level, but since moving to the
high altitude in Colorado I’ve taken the
curves back out.
Aileron differential is a means to even
out the drag on each wing of the aircraft
while rolling. If one aileron has more drag
than the other it can cause the airplane to
yaw off line as it rolls, giving you a wobble.
Normally the down aileron creates more
drag than the up side, giving us what is
commonly known as adverse yaw. Most
differential programs work well at adjusting
the down aileron for either roll direction.
Actually seeing this happen can be tricky,
so often it comes down to extensive
experimentation until you get a roll that
looks good.
Before computer radios, pilots and
designers used to adjust differential by
changing the location of the aileron hinge
line! Can you imagine the work involved in
doing that for each adjustment? You can
also see the importance of starting with
properly set aileron deflection. The key to
making intelligent adjustments is knowing
what you have to start with. Our Extra has
an axial roll, so I have no differential
programmed into the airplane.
Ready to Fly! If all is going well and
Who would have ever imagined five
years ago when I started to dream about the
type of Scale aerobatic model I wanted for
myself that it would turn into a major project
I would be able to share with the whole
modeling community? It has been my hope
that you come away from reading this series
with new knowledge or ideas about your
own modeling experiences. And if you come
away from it with a new airplane, that’s so
much the better!
It’s been incredibly gratifying to read so
many letters and E-mails from AMA
members who have followed and enjoyed
the series, and it’s been equally gratifying to
be able to forge ahead essentially with a
blank sheet and help the MA staff create a
model for future Web-based construction
articles and start the ball rolling for an
information database that will spread to all
aspects of the hobby.
The entire process of bringing this
airplane to you and documenting it as the
construction progressed would not have been
possible without Erik Richard’s tireless
effort and perfectionism. When we started
this project for Model Aviation, Erik’s wife
Angela was newly expecting their first child.
Erik’s daughter Julia is a year old now!
Throughout it all, Erik’s commitment to the
project has been unwavering.
Oh, don’t think for a minute that he’s
going to have time to spend at home with
his family now. We have plenty more ideas
and projects ready to get started on, and we
can stay busy for a long, long time … MA
Mike Hurley
11542 Decatur Ct.
Westminster CO 80234
[email protected]
78 MODEL AVIATION
you’ve followed Project Extra through the
building process, you’re probably just
putting the last drops of Loctite on your
bolts and checking throw directions one
final time before you head out to the field
for the first flights with your new airplane.

May 2003 63
Setup and Flight
Preparation
Volume VI:
ON A RECENT trip to the local flying field, one of the members had
brought his latest project, shiny and new, ready for the initial test
flight. I watched as he and his buddies began to go over the aircraft,
checking this and checking that. They adjusted the servo throw, and
two or three guys started to remove pieces from the airplane while
others made adjustments. Soon there was a large crowd around the
airplane. After some time it was determined that the owner needed to
take the airplane back home for some finishing before it could be
flown.
Sound familiar? You might have seen this happen at one time or
another. This particular flier was not a novice pilot; he had years of
experience and was considered by many to be one of the best pilots in
the area. Yet he came to the field with the intention of flying an
unprepared and untested aircraft with the idea that a few last-minute
items would be no big deal once he was there.
Come on! Don’t go to the field and install your servos! Make all of
your last-minute adjustments in the workshop and be 100% prepared
to fly when you leave your shop. It’s important to fully finish and
ready any aircraft before it goes to the field, but it is especially
■ Mike Hurley
important with an aircraft the size of the 35% Extra 300LX.
If you need the help of others in your club, ask those who you know
have the experience you need rather than taking the chance on whoever
may be present the day you go out for the initial flight. Get the help
you need and test every aspect of your airplane, then you can be
confident that you’re ready when you finally do get to that first flight.
Setup: Volume VI is the last installment of Project Extra and it will
help you get started with the process of setting up your airplane, but the
final outcome is entirely in your hands. No one can tell you exactly
how to set up your model to work just right for your personal
preferences. In fact, Erik Richards and I will be setting up two separate
programs/models on his radio for this Extra—one for his style of flying
and one for mine. Our preferences and styles are that different. Only
you know how you like your airplane to fly and feel.
Anyone setting up an aircraft of this size and caliber should have
plenty of experience with final adjustments by the time he or she gets
to this model. One of the last things to think about before flying an
airplane equipped with a gasoline engine (that you may not do with the
Erik Richard (standing) and Mike Hurley show off their completed Extra 300LXs. Erik’s is the one built throughout the
course of the construction articles.
June 2003 64
smaller models) is to Loctite all of the metalto-
metal hardware that does not need field
assembly. Use thread locker that is made for
hand-tool removal. That usually means the
blue formula, but check the label.
I’m assuming that you know about basic
preflight and finishing procedures for a new
aircraft: installing, charging, and checking
your batteries, sealing any exposed wood in
the engine compartment, range checking, and
other procedures common to modeling, so I
won’t go into those steps. But you know as an
experienced modeler that all of those things
are important for a successful aircraft. Again,
if you have questions, get help from someone
who has the experience. There’s a terrific
article on range checking at http://horizon.
hobbyshopnow.com/articles/1079.asp.
In this issue we’ll look at basic
programming for the Extra so that all of the
servos work together and you have some idea
of how to set up a large aerobatic airplane. I’ll
give you some guidelines for balance and
control throws and discuss standard trimming
for a precision aircraft. I’ll use the JR 10X
radio for the examples because that’s what I
use, but you can do most of these things with
any of today’s computer radios.
Refer to your transmitter’s instruction
manual, and remember that many functions
that perform the same tasks are referred to
with different names by the different
manufacturers. Each of these topics could
encompass an entire article in itself, so I’ll be
limited to the basics. You’ll want to expand
the information on your own with a little
experimentation, practice, and some help from
your friends. Another source of information
on how to set up an aerobatic airplane is
http://horizon.hobbyshopnow.com/articles/11
69.asp. Click on the PDF download for the
whole article.
Mixing: If you followed our plan for Project
Extra, the airplane uses two rudder servos
ganged inline and connected to a bellcrank for
the pull-pull system. I like to match my rudder
servos utilizing a multipoint mix in my
transmitter. Even with four servos on the
rudder of my 40% models, I match two sets of
two servos with MatchBoxes then use a
multipoint mix to match the two pairs.
With the JR 10X the two servos are
plugged into separate channels: Rudder and
Aux2. Since the servos will be hard connected
to each other, it’s important that each servo’s
full range of motion matches perfectly.
A multipoint mix has the advantage over
other methods, including MatchBoxes, in that
there are as many as five positions that can be
adjusted, and you can tailor the mixing points
to just those spots that need attention. For the
servo/bellcrank arrangement, first adjust the
linkages between the aft servo and the
bellcrank. As we discussed in Volume IV of
this series, the linkages must be centered and
run parallel to each other so that they have
equal movement without binding. Check that
there is no binding in any movement before
you power up any servos.
It’s also a good idea to have any servo
arms and linkages removed before powering
up a servo for the first time. We found some
interference between the ball link and the
bellcrank and had to add some washers to the
inside of the connection to spread the arms
slightly and make clearance. The bind was
not visually evident, and we wouldn’t have
found this problem if the servos had been
powered up.
Once the movement is clean, you can
install the second set of linkages, but don’t
connect them to the second servo arm just
yet. I like to adjust the linkage so I can see
the connection point looking through the hole
in the ball links. Then with the transmitter,
move through the travel and note where the
ball doesn’t follow the connection point
precisely. I usually adjust the endpoints and
neutral first. Most of the time that’s all that’s
needed, but if there are places during
transition that do not line up, create an
adjustment point and line it up. Bolt it up,
and you’re ready to hook the cables to the
rudder.
Follow the same basic procedures with
the ailerons, but the mix is done using the
MatchBox. The instructions that come with
the MatchBox are clear, and the procedure is
simple. The 10X has a preprogrammed mix
for dual elevators, and we used flaperons for
the ailerons so that differential mixing was
available if needed. I’ll write more about that
later.
Before we get to the point of setting up
any part of the radio, we need to ensure that
all of the controls are working in the correct
direction—especially the ailerons. Don’t go
any further until everything is correct!
Standing behind the airplane looking at it as
if it were flying away, move the aileron stick
left; the left aileron should be up and the right
aileron should be down. Move the stick right,
and the right aileron is up and the left aileron
is down. Do it now; don’t wait ’til later.
Control Throws: Here’s where things can
get sticky and settings will really vary with
each pilot’s personal abilities and
preferences. I use JR’s flight modes to
Field assembly is rather straightforward. Slide the wings onto the wing tube. Hook up
the servos. Fasten the wing to the fuselage, and bolt on the hatch.
With the proper setup and some practice, this Extra excels at 3-D maneuvers. Note the
extreme 45° elevator deflection.
June 2003 65
When ganging two servos for rudder pull-pull system, bolt one
end of control rod to servo arm; leave other open for alignment.
Make sure that your servos are correctly centered before you
make any adjustments. Erik used a set of dial calipers.
Be very careful to always check for correct control-surface
directions before the airplane leaves your shop.
Erik and Mike used a CRC deflection gauge to ensure the
desired (and equal) amount of deflection on both sides.
To ensure that the elevator deflection is equal in the center and
at its maximum endpoints, Erik used a set of carbon rods taped
to each elevator half as a pointer.
control all of my rates with a single switch. For me, using flight
modes helps me avoid confusion.
However, you should set up your radio close to the manner with
which you are most comfortable. After you get more comfortable with
the airplane, you can experiment with new switches and rate types,
such as flight modes. If you’re fairly new to 3-D, be sure to have a
quick and easy way to escape the 3-D setting, and never fly a new
model that does not have the option for a reduced-rate elevator.
For starters, let’s set up the Extra with two sets of control rates.
The elevator is the control that can get you into a lot of trouble fast, so
I’ll concentrate on that. We’ll have a standard rate for everyday flying,
which can be later optimized for precision, and a setting for maximum
control throw, which is the 3-D mode.
Setting surface deflection is another initial step where so many
pilots tend to rely on the TLAR (“that looks about right”) method. But
really, this stuff is critical to an airplane that flies in a neutral manner
and won’t fight your every input. For control setup I use CRC Throw
Meters to tell me, in degrees, exactly where the control surfaces are
set. The CRC gauges are available from Central Hobbies at
www.centralhobbies.com/.
One often-overlooked step in setup is matching aileron throw left
The Project Extra series is presented on the
AMA Web site at www.modelaircraft.org.
to right and up and down. It’s nice to have
two gauges for matching ailerons. Before
you adjust throw, match the neutral and
endpoints for the ailerons. I make these
adjustments at maximum deflection or 100%
travel. Then as you adjust the total throws or
rate settings, the control surfaces should stay
in sync.
To make sure the elevators are in sync,
Erik likes to use a 24-inch length of carbon
tubing taped to each elevator half as a
pointer. The carbon rod is stiff and does not
flex at this long length, so it stays accurate.
Line up the elevators at the counterbalances
to make sure they’re level, then tape the
tubes to the surface so that they point directly
to each other when centered. Erik used a
toothpick in the end of each tube for further
accuracy.
Move the surfaces slowly and watch for
differences along the length of travel; some
offset as the elevators move is normal. The
pointers are so long that a fairly large gap of,
say, a half inch only reflects a minute offset,
so don’t get too worried unless the
differences are huge. With the transmitter
you can now adjust the endpoints to match
perfectly at the extremes of each throw, and
you are assured of even elevator adjustment.
For the beginning setup and initial flight
testing, set the ailerons to 15° of throw each
way and the elevators to 20° each way. To
set the rudder, you must turn the fuselage on
its side with the wings and stabilizers
66 MODEL AVIATION
removed from the airplane. Initially set the
rudder to 35° each way. After you get
comfortable with the model, readjust all of the
deflections and settings to suit your flying
style.
The Dead Zone: Before we get into the setup
for 3-D, let’s discuss flying with huge throws
and some of the things to understand before
you try flying with 3-D throws the first time.
With a little bit of exponential, or “expo,” and
some experience, this Extra can be flown with
any amount of control throw. I fly mine on
full maximum 3-D rate all the time. That
includes takeoff, landing, and everything in
between. The only time I switch out of 3-D is
to fly a precision flight where I want more
exacting control of the airplane.
For a while I was starting to think that the
model couldn’t be induced to snap with
elevator alone and that anyone could fly it in
3-D mode, but I was brought back to reality
when I let a friend fly the airplane. My friend
was an experienced pilot who I trusted
completely, but he had never flown an
airplane set up for 3-D.
At first when I handed him the transmitter
set to precision rates, he had a ball doing
rolling loops, knife-edge circles, and multiple
snaps; you name it, and he was doing it! He
became comfortable with the airplane and
started to try some of the 3-D stuff that he had
seen me do. “You can’t do those things in low
rate,” I said. “I’ll switch to 3-D for you.” I hit
the switch, and the smile on his face started to
relax; he was beginning to look worried.
Suddenly just controlling the airplane
through a loop was difficult, and he snapped
the model without provocation within a
couple of seconds. “Shut it off!” he yelled,
and I hit the switch back to low rate. That
episode made me realize that, without
knowing it, I had become used to flying the
Extra in a manner that worked with extreme
surface deflection, but the model could still be
a handful to pilots who are just learning 3-D.
Don’t get caught in the trap. Some of you
may read the preceding account and think to
yourself, I’ll just tone it down a bit by
Defying the Limits
Learning to fly 3-D maneuvers is fun
and satisfying, and the Project Extra
model is a great aircraft with which to
learn 3-D. Another advantage is to gather
information to help you get started. If
you’d like to learn more about high-alpha
flight, 3-D maneuvers, aircraft
preparation, equipment, and setup,
Robin’s View Productions has released a
video called Defying the Limits, featuring
world-renowned 3-D and precision pilot
Jason Shulman. I developed and filmed
the video.
Defying the Limits is available on
DVD with convenient searchable
chapters. For more information or to
order the video, contact Robin’s View
Productions at (610) 746-0106. MA
—Mike Hurley
68 MODEL AVIATION
reducing the control throw and work up to
more throw as I get comfortable. That’s
exactly what can get you into more trouble.
The secret to entering and exiting 3-D is
to have the pitch authority to power past a
stalled attitude and hold it with massive
surfaces, deflection, and a powerful
propeller blast. If you tone it down by
lowering the surface deflection and try the
maneuver, the airplane won’t have the
required pitch authority and will stall. I call
the lowered surface deflection “the dead
zone.” The dead zone is too low for 3-D
and too high for precision control. The dead
zone will get you into trouble in a hurry.
Flying 3-D: When flying the model,
remember that you need to be committed to
getting into and out of a high-alpha (HA)
attitude. It’s important to have enough
airspeed or power to transition into a high
angle of attack. I’ve noticed that people get
into trouble when they move too slowly
into the transition or don’t use enough
elevator deflection or engine power.
I’m not saying you need to perform 3-D
maneuvers with a higher airspeed, but if the
speed is low you must use the power from
your engine to move the airplane’s tail into
position. Indeed you can slow the model to
a stall as long as you keep inducing the
power needed to keep the tail below the
airplane. At that point you can transition
into a hover with no forward airspeed.
Inversely, you can transition into HA with
power off if you maintain the airspeed to
pop your model into position, but once in
position you need to power up to hold
altitude.
Learning to fly into and out of HA
safely is the beginning of learning to fly 3-
D; it’s not hard to do, but it takes a little
finesse. If you’re not getting it quite right,
the aircraft will let you know with a nice
wing drop or an all-out snap.
My recommendation, even if you’re
experienced, is to start slow and use the rate
switch. Have enough expo dialed in to keep
the airplane controllable, and only switch
into 3-D mode to execute a specific 3-D
maneuver, then switch back to low rate to
fly out. Set your elevator to 45° for 3-D
deflection. The dead zone for the elevator is
27-37°; try to avoid those settings. For the
ailerons, you can 3-D nicely at 25-30°
deflection, and the rudder should be 45°.
There is no dead zone for the rudder or
ailerons.
Remember that these rates can get you
into trouble fast and are not recommended
for beginning pilots. If you have to
significantly reduce the travel on your radio
from 100% to get the ailerons down to 30° of
deflection, I recommend moving the controlrod
mounting position on the servo arm
inboard toward the output shaft until you get
the desired deflection with the radio
programmed to 100%.
Exponential: Expo is a program on most
computer radios that allows you to adjust a
nonlinearity of the stick movement relative
to the servo arm output. In most cases
pilots use expo to soften the feel of the
stick around the neutral position, especially
when there is a lot of surface deflection. To
create a softer feel you are moving a
portion of the servo travel to a different
area of the stick deflection—in this case,
farther out in the travel. So the servo moves
less near the center of the stick position and
exponentially moves more as the stick moves
toward full travel.
Here’s a funny fact that shows a need for
standardization. With a JR radio you want to
dial in positive expo for a softer neutral area,
but a negative value is needed with Futaba.
Be sure to read your owner’s manual!
Because I can’t climb into your shoes, I
cannot give you a positive starting point for
setting expo on this airplane. You will need
to do it for yourself. The trick is to set a value
and try it. Change one setting at a time and
find the value that works best for you.
Following is what I have set on my Extra
at max 3-D deflection: aileron, +50%;
elevator, +55%; and rudder +30%. I have
expo for precision too, but it’s slightly
different; aileron is +30%, elevator is +30%,
and rudder is +40%.
You can see that my rudder expo is higher
for precision than for 3-D. That’s to try to
smooth out any rudder wobble while flying
precision maneuvers. You can really effect
some big changes with expo that can gain big
advantages by smoothing out your flying
around the center of the stick while allowing
a large amount of control deflection right at
your fingers if you need it. There’s also the
possibility of too much of a good thing, so be
careful and don’t numb out the center of
your radio’s stick completely. Once you’re
comfortable with the airplane, give it a try
and don’t be afraid to experiment.
Balance: The center of gravity (CG) located
on the plans is conservative, at
approximately 32% of the chord at the mean
aerodynamic center (MAC). I fly my
airplane at this forward position, and it
works great for 3-D and precision flying.
It’s safe to locate the CG anywhere between
F3 and the forward edge of the wing tube
socket. I feel that, within limits, CG
location can be a personal preference. Many
of the top pilots fly with a forward CG for
precision and move the CG aft for freestyle.
Some people believe that you must have
a rear-biased CG to perform any 3-D
maneuvers; that simply is not true. In some
3-D maneuvers a rearward CG will slightly
enhance the model’s performance, but in
most other flight attitudes the performance
will suffer. I prefer to lose a tiny amount of
3-D performance to keep the rest of the
aircraft’s integrity intact, yet with practice
I’m able to perform any 3-D maneuver.
Trimming: Decidedly, trimming your
airplane for neutral flight is the difference
between a model that flies well and one that
you fight to keep on track. Trimming a
model properly is also one of the most
overlooked steps in readying it for
competition. Hey, it flies pretty well right
off the blocks, so why spend so much time
on a few minor changes? It does take a bit
of time to get everything right. I’ve spent
almost 100 flights getting one of my
competition airplanes to where I wanted it.
No, it wasn’t a problem airplane; on the
contrary, it was fantastic, and that’s why I
knew it had so much potential to be close to
perfect.
Some of the things you want to look for
are the ability to fly precision up- and
down-lines, 45s, and loops without the need
for stick input. There are many good
trimming procedures and charts available
that can take you step by step through the
procedure, and I would most likely be
doing you a disservice if I tried to make a
condensed version here, so take a look
online. You can download a chart from the
National Society of Radio Controlled
Aerobatics at www.nsrca.org/
trimA.htm. While you’re at it, take a look at
the Web site; these are the people who lead
the way in precision aerobatics.
Common Mixes: Most Scale Aerobatics
(SA) airplanes have some form of unwanted
coupling to the rudder. In an ideal scenario,
rudder movement would impart yaw only,
but with many Scale aircraft the rudder will
also effect some roll and/or some pitch.
Those are things we do not want for
precision flying, so it’s a common practice to
create a mix to trim those attributes out.
After you’re comfortable with how the
airplane flies, you can start to add these
trimming mixes.
For the rudder coupling, check the trim
by flying the airplane in knife edge. Set the
mix by flying at an even medium speed with
only enough rudder to sustain level knifeedge
flight. Many of today’s computer
radios have special mixes just for this
trimming procedure. I believe that all of
JR’s computer radios from the 662 up to the
10X have this specific feature.
The rudder is always the master channel.
Aileron will be slaved for roll, and elevator
will be slaved for pitch. The amount of mix
depends on your model and a variety of
dynamic forces that can change, such as
atmospheric density, balance, airspeed,
servo power, and so on. So no matter how
well you dial in the mix, it will never be
100% foolproof, and your model will more
than likely be somewhat different from the
next flier’s.
It’s also quite common for the mix for
left rudder to be slightly different from the
mix for right rudder, so you will have to trim
those tendencies out one step at a time. Our
Extra does not have any roll coupling, but
Scale aerobatic airplanes will commonly
have a 2-4% mix. This model does tuck
slightly, so I have 10% up-elevator mixed
for left and right rudder. That number would
decrease with a more rearward balance. To
be conservative, start with approximately
5% up if it tucks to the gear or down if it
pulls to the canopy, and decide from that
point if you need more or less mix.
I like to put my mix on a switch so it
can be defeated if necessary. The switch
could be useful when performing rolling
maneuvers such as a slow roll or a rolling
circle, where you are flying through the
maneuver with all of the controls in sync,
but (to be honest!) I leave the switch on all
the time.
More Mixes: Other mixes that are common
to SA aircraft are a throttle curve and aileron
differential. I don’t use either of them with
my airplane, but I thought it prudent to
touch on them here.
A throttle curve is used to make the
engine power feel more linear through the
entire range of stick motion. Since
carburetor butterfly position does not
usually translate to engine rpm, most of the
change in power comes at the lower end of
the stick movement. You can set a curve to
give you a more even feel. Some people use
this for torque rolling if the throttle is too
touchy at the hovering rpm range. I had
throttle curves in all of my models when I
flew at sea level, but since moving to the
high altitude in Colorado I’ve taken the
curves back out.
Aileron differential is a means to even
out the drag on each wing of the aircraft
while rolling. If one aileron has more drag
than the other it can cause the airplane to
yaw off line as it rolls, giving you a wobble.
Normally the down aileron creates more
drag than the up side, giving us what is
commonly known as adverse yaw. Most
differential programs work well at adjusting
the down aileron for either roll direction.
Actually seeing this happen can be tricky,
so often it comes down to extensive
experimentation until you get a roll that
looks good.
Before computer radios, pilots and
designers used to adjust differential by
changing the location of the aileron hinge
line! Can you imagine the work involved in
doing that for each adjustment? You can
also see the importance of starting with
properly set aileron deflection. The key to
making intelligent adjustments is knowing
what you have to start with. Our Extra has
an axial roll, so I have no differential
programmed into the airplane.
Ready to Fly! If all is going well and
Who would have ever imagined five
years ago when I started to dream about the
type of Scale aerobatic model I wanted for
myself that it would turn into a major project
I would be able to share with the whole
modeling community? It has been my hope
that you come away from reading this series
with new knowledge or ideas about your
own modeling experiences. And if you come
away from it with a new airplane, that’s so
much the better!
It’s been incredibly gratifying to read so
many letters and E-mails from AMA
members who have followed and enjoyed
the series, and it’s been equally gratifying to
be able to forge ahead essentially with a
blank sheet and help the MA staff create a
model for future Web-based construction
articles and start the ball rolling for an
information database that will spread to all
aspects of the hobby.
The entire process of bringing this
airplane to you and documenting it as the
construction progressed would not have been
possible without Erik Richard’s tireless
effort and perfectionism. When we started
this project for Model Aviation, Erik’s wife
Angela was newly expecting their first child.
Erik’s daughter Julia is a year old now!
Throughout it all, Erik’s commitment to the
project has been unwavering.
Oh, don’t think for a minute that he’s
going to have time to spend at home with
his family now. We have plenty more ideas
and projects ready to get started on, and we
can stay busy for a long, long time … MA
Mike Hurley
11542 Decatur Ct.
Westminster CO 80234
[email protected]
78 MODEL AVIATION
you’ve followed Project Extra through the
building process, you’re probably just
putting the last drops of Loctite on your
bolts and checking throw directions one
final time before you head out to the field
for the first flights with your new airplane.

May 2003 63
Setup and Flight
Preparation
Volume VI:
ON A RECENT trip to the local flying field, one of the members had
brought his latest project, shiny and new, ready for the initial test
flight. I watched as he and his buddies began to go over the aircraft,
checking this and checking that. They adjusted the servo throw, and
two or three guys started to remove pieces from the airplane while
others made adjustments. Soon there was a large crowd around the
airplane. After some time it was determined that the owner needed to
take the airplane back home for some finishing before it could be
flown.
Sound familiar? You might have seen this happen at one time or
another. This particular flier was not a novice pilot; he had years of
experience and was considered by many to be one of the best pilots in
the area. Yet he came to the field with the intention of flying an
unprepared and untested aircraft with the idea that a few last-minute
items would be no big deal once he was there.
Come on! Don’t go to the field and install your servos! Make all of
your last-minute adjustments in the workshop and be 100% prepared
to fly when you leave your shop. It’s important to fully finish and
ready any aircraft before it goes to the field, but it is especially
■ Mike Hurley
important with an aircraft the size of the 35% Extra 300LX.
If you need the help of others in your club, ask those who you know
have the experience you need rather than taking the chance on whoever
may be present the day you go out for the initial flight. Get the help
you need and test every aspect of your airplane, then you can be
confident that you’re ready when you finally do get to that first flight.
Setup: Volume VI is the last installment of Project Extra and it will
help you get started with the process of setting up your airplane, but the
final outcome is entirely in your hands. No one can tell you exactly
how to set up your model to work just right for your personal
preferences. In fact, Erik Richards and I will be setting up two separate
programs/models on his radio for this Extra—one for his style of flying
and one for mine. Our preferences and styles are that different. Only
you know how you like your airplane to fly and feel.
Anyone setting up an aircraft of this size and caliber should have
plenty of experience with final adjustments by the time he or she gets
to this model. One of the last things to think about before flying an
airplane equipped with a gasoline engine (that you may not do with the
Erik Richard (standing) and Mike Hurley show off their completed Extra 300LXs. Erik’s is the one built throughout the
course of the construction articles.
June 2003 64
smaller models) is to Loctite all of the metalto-
metal hardware that does not need field
assembly. Use thread locker that is made for
hand-tool removal. That usually means the
blue formula, but check the label.
I’m assuming that you know about basic
preflight and finishing procedures for a new
aircraft: installing, charging, and checking
your batteries, sealing any exposed wood in
the engine compartment, range checking, and
other procedures common to modeling, so I
won’t go into those steps. But you know as an
experienced modeler that all of those things
are important for a successful aircraft. Again,
if you have questions, get help from someone
who has the experience. There’s a terrific
article on range checking at http://horizon.
hobbyshopnow.com/articles/1079.asp.
In this issue we’ll look at basic
programming for the Extra so that all of the
servos work together and you have some idea
of how to set up a large aerobatic airplane. I’ll
give you some guidelines for balance and
control throws and discuss standard trimming
for a precision aircraft. I’ll use the JR 10X
radio for the examples because that’s what I
use, but you can do most of these things with
any of today’s computer radios.
Refer to your transmitter’s instruction
manual, and remember that many functions
that perform the same tasks are referred to
with different names by the different
manufacturers. Each of these topics could
encompass an entire article in itself, so I’ll be
limited to the basics. You’ll want to expand
the information on your own with a little
experimentation, practice, and some help from
your friends. Another source of information
on how to set up an aerobatic airplane is
http://horizon.hobbyshopnow.com/articles/11
69.asp. Click on the PDF download for the
whole article.
Mixing: If you followed our plan for Project
Extra, the airplane uses two rudder servos
ganged inline and connected to a bellcrank for
the pull-pull system. I like to match my rudder
servos utilizing a multipoint mix in my
transmitter. Even with four servos on the
rudder of my 40% models, I match two sets of
two servos with MatchBoxes then use a
multipoint mix to match the two pairs.
With the JR 10X the two servos are
plugged into separate channels: Rudder and
Aux2. Since the servos will be hard connected
to each other, it’s important that each servo’s
full range of motion matches perfectly.
A multipoint mix has the advantage over
other methods, including MatchBoxes, in that
there are as many as five positions that can be
adjusted, and you can tailor the mixing points
to just those spots that need attention. For the
servo/bellcrank arrangement, first adjust the
linkages between the aft servo and the
bellcrank. As we discussed in Volume IV of
this series, the linkages must be centered and
run parallel to each other so that they have
equal movement without binding. Check that
there is no binding in any movement before
you power up any servos.
It’s also a good idea to have any servo
arms and linkages removed before powering
up a servo for the first time. We found some
interference between the ball link and the
bellcrank and had to add some washers to the
inside of the connection to spread the arms
slightly and make clearance. The bind was
not visually evident, and we wouldn’t have
found this problem if the servos had been
powered up.
Once the movement is clean, you can
install the second set of linkages, but don’t
connect them to the second servo arm just
yet. I like to adjust the linkage so I can see
the connection point looking through the hole
in the ball links. Then with the transmitter,
move through the travel and note where the
ball doesn’t follow the connection point
precisely. I usually adjust the endpoints and
neutral first. Most of the time that’s all that’s
needed, but if there are places during
transition that do not line up, create an
adjustment point and line it up. Bolt it up,
and you’re ready to hook the cables to the
rudder.
Follow the same basic procedures with
the ailerons, but the mix is done using the
MatchBox. The instructions that come with
the MatchBox are clear, and the procedure is
simple. The 10X has a preprogrammed mix
for dual elevators, and we used flaperons for
the ailerons so that differential mixing was
available if needed. I’ll write more about that
later.
Before we get to the point of setting up
any part of the radio, we need to ensure that
all of the controls are working in the correct
direction—especially the ailerons. Don’t go
any further until everything is correct!
Standing behind the airplane looking at it as
if it were flying away, move the aileron stick
left; the left aileron should be up and the right
aileron should be down. Move the stick right,
and the right aileron is up and the left aileron
is down. Do it now; don’t wait ’til later.
Control Throws: Here’s where things can
get sticky and settings will really vary with
each pilot’s personal abilities and
preferences. I use JR’s flight modes to
Field assembly is rather straightforward. Slide the wings onto the wing tube. Hook up
the servos. Fasten the wing to the fuselage, and bolt on the hatch.
With the proper setup and some practice, this Extra excels at 3-D maneuvers. Note the
extreme 45° elevator deflection.
June 2003 65
When ganging two servos for rudder pull-pull system, bolt one
end of control rod to servo arm; leave other open for alignment.
Make sure that your servos are correctly centered before you
make any adjustments. Erik used a set of dial calipers.
Be very careful to always check for correct control-surface
directions before the airplane leaves your shop.
Erik and Mike used a CRC deflection gauge to ensure the
desired (and equal) amount of deflection on both sides.
To ensure that the elevator deflection is equal in the center and
at its maximum endpoints, Erik used a set of carbon rods taped
to each elevator half as a pointer.
control all of my rates with a single switch. For me, using flight
modes helps me avoid confusion.
However, you should set up your radio close to the manner with
which you are most comfortable. After you get more comfortable with
the airplane, you can experiment with new switches and rate types,
such as flight modes. If you’re fairly new to 3-D, be sure to have a
quick and easy way to escape the 3-D setting, and never fly a new
model that does not have the option for a reduced-rate elevator.
For starters, let’s set up the Extra with two sets of control rates.
The elevator is the control that can get you into a lot of trouble fast, so
I’ll concentrate on that. We’ll have a standard rate for everyday flying,
which can be later optimized for precision, and a setting for maximum
control throw, which is the 3-D mode.
Setting surface deflection is another initial step where so many
pilots tend to rely on the TLAR (“that looks about right”) method. But
really, this stuff is critical to an airplane that flies in a neutral manner
and won’t fight your every input. For control setup I use CRC Throw
Meters to tell me, in degrees, exactly where the control surfaces are
set. The CRC gauges are available from Central Hobbies at
www.centralhobbies.com/.
One often-overlooked step in setup is matching aileron throw left
The Project Extra series is presented on the
AMA Web site at www.modelaircraft.org.
to right and up and down. It’s nice to have
two gauges for matching ailerons. Before
you adjust throw, match the neutral and
endpoints for the ailerons. I make these
adjustments at maximum deflection or 100%
travel. Then as you adjust the total throws or
rate settings, the control surfaces should stay
in sync.
To make sure the elevators are in sync,
Erik likes to use a 24-inch length of carbon
tubing taped to each elevator half as a
pointer. The carbon rod is stiff and does not
flex at this long length, so it stays accurate.
Line up the elevators at the counterbalances
to make sure they’re level, then tape the
tubes to the surface so that they point directly
to each other when centered. Erik used a
toothpick in the end of each tube for further
accuracy.
Move the surfaces slowly and watch for
differences along the length of travel; some
offset as the elevators move is normal. The
pointers are so long that a fairly large gap of,
say, a half inch only reflects a minute offset,
so don’t get too worried unless the
differences are huge. With the transmitter
you can now adjust the endpoints to match
perfectly at the extremes of each throw, and
you are assured of even elevator adjustment.
For the beginning setup and initial flight
testing, set the ailerons to 15° of throw each
way and the elevators to 20° each way. To
set the rudder, you must turn the fuselage on
its side with the wings and stabilizers
66 MODEL AVIATION
removed from the airplane. Initially set the
rudder to 35° each way. After you get
comfortable with the model, readjust all of the
deflections and settings to suit your flying
style.
The Dead Zone: Before we get into the setup
for 3-D, let’s discuss flying with huge throws
and some of the things to understand before
you try flying with 3-D throws the first time.
With a little bit of exponential, or “expo,” and
some experience, this Extra can be flown with
any amount of control throw. I fly mine on
full maximum 3-D rate all the time. That
includes takeoff, landing, and everything in
between. The only time I switch out of 3-D is
to fly a precision flight where I want more
exacting control of the airplane.
For a while I was starting to think that the
model couldn’t be induced to snap with
elevator alone and that anyone could fly it in
3-D mode, but I was brought back to reality
when I let a friend fly the airplane. My friend
was an experienced pilot who I trusted
completely, but he had never flown an
airplane set up for 3-D.
At first when I handed him the transmitter
set to precision rates, he had a ball doing
rolling loops, knife-edge circles, and multiple
snaps; you name it, and he was doing it! He
became comfortable with the airplane and
started to try some of the 3-D stuff that he had
seen me do. “You can’t do those things in low
rate,” I said. “I’ll switch to 3-D for you.” I hit
the switch, and the smile on his face started to
relax; he was beginning to look worried.
Suddenly just controlling the airplane
through a loop was difficult, and he snapped
the model without provocation within a
couple of seconds. “Shut it off!” he yelled,
and I hit the switch back to low rate. That
episode made me realize that, without
knowing it, I had become used to flying the
Extra in a manner that worked with extreme
surface deflection, but the model could still be
a handful to pilots who are just learning 3-D.
Don’t get caught in the trap. Some of you
may read the preceding account and think to
yourself, I’ll just tone it down a bit by
Defying the Limits
Learning to fly 3-D maneuvers is fun
and satisfying, and the Project Extra
model is a great aircraft with which to
learn 3-D. Another advantage is to gather
information to help you get started. If
you’d like to learn more about high-alpha
flight, 3-D maneuvers, aircraft
preparation, equipment, and setup,
Robin’s View Productions has released a
video called Defying the Limits, featuring
world-renowned 3-D and precision pilot
Jason Shulman. I developed and filmed
the video.
Defying the Limits is available on
DVD with convenient searchable
chapters. For more information or to
order the video, contact Robin’s View
Productions at (610) 746-0106. MA
—Mike Hurley
68 MODEL AVIATION
reducing the control throw and work up to
more throw as I get comfortable. That’s
exactly what can get you into more trouble.
The secret to entering and exiting 3-D is
to have the pitch authority to power past a
stalled attitude and hold it with massive
surfaces, deflection, and a powerful
propeller blast. If you tone it down by
lowering the surface deflection and try the
maneuver, the airplane won’t have the
required pitch authority and will stall. I call
the lowered surface deflection “the dead
zone.” The dead zone is too low for 3-D
and too high for precision control. The dead
zone will get you into trouble in a hurry.
Flying 3-D: When flying the model,
remember that you need to be committed to
getting into and out of a high-alpha (HA)
attitude. It’s important to have enough
airspeed or power to transition into a high
angle of attack. I’ve noticed that people get
into trouble when they move too slowly
into the transition or don’t use enough
elevator deflection or engine power.
I’m not saying you need to perform 3-D
maneuvers with a higher airspeed, but if the
speed is low you must use the power from
your engine to move the airplane’s tail into
position. Indeed you can slow the model to
a stall as long as you keep inducing the
power needed to keep the tail below the
airplane. At that point you can transition
into a hover with no forward airspeed.
Inversely, you can transition into HA with
power off if you maintain the airspeed to
pop your model into position, but once in
position you need to power up to hold
altitude.
Learning to fly into and out of HA
safely is the beginning of learning to fly 3-
D; it’s not hard to do, but it takes a little
finesse. If you’re not getting it quite right,
the aircraft will let you know with a nice
wing drop or an all-out snap.
My recommendation, even if you’re
experienced, is to start slow and use the rate
switch. Have enough expo dialed in to keep
the airplane controllable, and only switch
into 3-D mode to execute a specific 3-D
maneuver, then switch back to low rate to
fly out. Set your elevator to 45° for 3-D
deflection. The dead zone for the elevator is
27-37°; try to avoid those settings. For the
ailerons, you can 3-D nicely at 25-30°
deflection, and the rudder should be 45°.
There is no dead zone for the rudder or
ailerons.
Remember that these rates can get you
into trouble fast and are not recommended
for beginning pilots. If you have to
significantly reduce the travel on your radio
from 100% to get the ailerons down to 30° of
deflection, I recommend moving the controlrod
mounting position on the servo arm
inboard toward the output shaft until you get
the desired deflection with the radio
programmed to 100%.
Exponential: Expo is a program on most
computer radios that allows you to adjust a
nonlinearity of the stick movement relative
to the servo arm output. In most cases
pilots use expo to soften the feel of the
stick around the neutral position, especially
when there is a lot of surface deflection. To
create a softer feel you are moving a
portion of the servo travel to a different
area of the stick deflection—in this case,
farther out in the travel. So the servo moves
less near the center of the stick position and
exponentially moves more as the stick moves
toward full travel.
Here’s a funny fact that shows a need for
standardization. With a JR radio you want to
dial in positive expo for a softer neutral area,
but a negative value is needed with Futaba.
Be sure to read your owner’s manual!
Because I can’t climb into your shoes, I
cannot give you a positive starting point for
setting expo on this airplane. You will need
to do it for yourself. The trick is to set a value
and try it. Change one setting at a time and
find the value that works best for you.
Following is what I have set on my Extra
at max 3-D deflection: aileron, +50%;
elevator, +55%; and rudder +30%. I have
expo for precision too, but it’s slightly
different; aileron is +30%, elevator is +30%,
and rudder is +40%.
You can see that my rudder expo is higher
for precision than for 3-D. That’s to try to
smooth out any rudder wobble while flying
precision maneuvers. You can really effect
some big changes with expo that can gain big
advantages by smoothing out your flying
around the center of the stick while allowing
a large amount of control deflection right at
your fingers if you need it. There’s also the
possibility of too much of a good thing, so be
careful and don’t numb out the center of
your radio’s stick completely. Once you’re
comfortable with the airplane, give it a try
and don’t be afraid to experiment.
Balance: The center of gravity (CG) located
on the plans is conservative, at
approximately 32% of the chord at the mean
aerodynamic center (MAC). I fly my
airplane at this forward position, and it
works great for 3-D and precision flying.
It’s safe to locate the CG anywhere between
F3 and the forward edge of the wing tube
socket. I feel that, within limits, CG
location can be a personal preference. Many
of the top pilots fly with a forward CG for
precision and move the CG aft for freestyle.
Some people believe that you must have
a rear-biased CG to perform any 3-D
maneuvers; that simply is not true. In some
3-D maneuvers a rearward CG will slightly
enhance the model’s performance, but in
most other flight attitudes the performance
will suffer. I prefer to lose a tiny amount of
3-D performance to keep the rest of the
aircraft’s integrity intact, yet with practice
I’m able to perform any 3-D maneuver.
Trimming: Decidedly, trimming your
airplane for neutral flight is the difference
between a model that flies well and one that
you fight to keep on track. Trimming a
model properly is also one of the most
overlooked steps in readying it for
competition. Hey, it flies pretty well right
off the blocks, so why spend so much time
on a few minor changes? It does take a bit
of time to get everything right. I’ve spent
almost 100 flights getting one of my
competition airplanes to where I wanted it.
No, it wasn’t a problem airplane; on the
contrary, it was fantastic, and that’s why I
knew it had so much potential to be close to
perfect.
Some of the things you want to look for
are the ability to fly precision up- and
down-lines, 45s, and loops without the need
for stick input. There are many good
trimming procedures and charts available
that can take you step by step through the
procedure, and I would most likely be
doing you a disservice if I tried to make a
condensed version here, so take a look
online. You can download a chart from the
National Society of Radio Controlled
Aerobatics at www.nsrca.org/
trimA.htm. While you’re at it, take a look at
the Web site; these are the people who lead
the way in precision aerobatics.
Common Mixes: Most Scale Aerobatics
(SA) airplanes have some form of unwanted
coupling to the rudder. In an ideal scenario,
rudder movement would impart yaw only,
but with many Scale aircraft the rudder will
also effect some roll and/or some pitch.
Those are things we do not want for
precision flying, so it’s a common practice to
create a mix to trim those attributes out.
After you’re comfortable with how the
airplane flies, you can start to add these
trimming mixes.
For the rudder coupling, check the trim
by flying the airplane in knife edge. Set the
mix by flying at an even medium speed with
only enough rudder to sustain level knifeedge
flight. Many of today’s computer
radios have special mixes just for this
trimming procedure. I believe that all of
JR’s computer radios from the 662 up to the
10X have this specific feature.
The rudder is always the master channel.
Aileron will be slaved for roll, and elevator
will be slaved for pitch. The amount of mix
depends on your model and a variety of
dynamic forces that can change, such as
atmospheric density, balance, airspeed,
servo power, and so on. So no matter how
well you dial in the mix, it will never be
100% foolproof, and your model will more
than likely be somewhat different from the
next flier’s.
It’s also quite common for the mix for
left rudder to be slightly different from the
mix for right rudder, so you will have to trim
those tendencies out one step at a time. Our
Extra does not have any roll coupling, but
Scale aerobatic airplanes will commonly
have a 2-4% mix. This model does tuck
slightly, so I have 10% up-elevator mixed
for left and right rudder. That number would
decrease with a more rearward balance. To
be conservative, start with approximately
5% up if it tucks to the gear or down if it
pulls to the canopy, and decide from that
point if you need more or less mix.
I like to put my mix on a switch so it
can be defeated if necessary. The switch
could be useful when performing rolling
maneuvers such as a slow roll or a rolling
circle, where you are flying through the
maneuver with all of the controls in sync,
but (to be honest!) I leave the switch on all
the time.
More Mixes: Other mixes that are common
to SA aircraft are a throttle curve and aileron
differential. I don’t use either of them with
my airplane, but I thought it prudent to
touch on them here.
A throttle curve is used to make the
engine power feel more linear through the
entire range of stick motion. Since
carburetor butterfly position does not
usually translate to engine rpm, most of the
change in power comes at the lower end of
the stick movement. You can set a curve to
give you a more even feel. Some people use
this for torque rolling if the throttle is too
touchy at the hovering rpm range. I had
throttle curves in all of my models when I
flew at sea level, but since moving to the
high altitude in Colorado I’ve taken the
curves back out.
Aileron differential is a means to even
out the drag on each wing of the aircraft
while rolling. If one aileron has more drag
than the other it can cause the airplane to
yaw off line as it rolls, giving you a wobble.
Normally the down aileron creates more
drag than the up side, giving us what is
commonly known as adverse yaw. Most
differential programs work well at adjusting
the down aileron for either roll direction.
Actually seeing this happen can be tricky,
so often it comes down to extensive
experimentation until you get a roll that
looks good.
Before computer radios, pilots and
designers used to adjust differential by
changing the location of the aileron hinge
line! Can you imagine the work involved in
doing that for each adjustment? You can
also see the importance of starting with
properly set aileron deflection. The key to
making intelligent adjustments is knowing
what you have to start with. Our Extra has
an axial roll, so I have no differential
programmed into the airplane.
Ready to Fly! If all is going well and
Who would have ever imagined five
years ago when I started to dream about the
type of Scale aerobatic model I wanted for
myself that it would turn into a major project
I would be able to share with the whole
modeling community? It has been my hope
that you come away from reading this series
with new knowledge or ideas about your
own modeling experiences. And if you come
away from it with a new airplane, that’s so
much the better!
It’s been incredibly gratifying to read so
many letters and E-mails from AMA
members who have followed and enjoyed
the series, and it’s been equally gratifying to
be able to forge ahead essentially with a
blank sheet and help the MA staff create a
model for future Web-based construction
articles and start the ball rolling for an
information database that will spread to all
aspects of the hobby.
The entire process of bringing this
airplane to you and documenting it as the
construction progressed would not have been
possible without Erik Richard’s tireless
effort and perfectionism. When we started
this project for Model Aviation, Erik’s wife
Angela was newly expecting their first child.
Erik’s daughter Julia is a year old now!
Throughout it all, Erik’s commitment to the
project has been unwavering.
Oh, don’t think for a minute that he’s
going to have time to spend at home with
his family now. We have plenty more ideas
and projects ready to get started on, and we
can stay busy for a long, long time … MA
Mike Hurley
11542 Decatur Ct.
Westminster CO 80234
[email protected]
78 MODEL AVIATION
you’ve followed Project Extra through the
building process, you’re probably just
putting the last drops of Loctite on your
bolts and checking throw directions one
final time before you head out to the field
for the first flights with your new airplane.

May 2003 63
Setup and Flight
Preparation
Volume VI:
ON A RECENT trip to the local flying field, one of the members had
brought his latest project, shiny and new, ready for the initial test
flight. I watched as he and his buddies began to go over the aircraft,
checking this and checking that. They adjusted the servo throw, and
two or three guys started to remove pieces from the airplane while
others made adjustments. Soon there was a large crowd around the
airplane. After some time it was determined that the owner needed to
take the airplane back home for some finishing before it could be
flown.
Sound familiar? You might have seen this happen at one time or
another. This particular flier was not a novice pilot; he had years of
experience and was considered by many to be one of the best pilots in
the area. Yet he came to the field with the intention of flying an
unprepared and untested aircraft with the idea that a few last-minute
items would be no big deal once he was there.
Come on! Don’t go to the field and install your servos! Make all of
your last-minute adjustments in the workshop and be 100% prepared
to fly when you leave your shop. It’s important to fully finish and
ready any aircraft before it goes to the field, but it is especially
■ Mike Hurley
important with an aircraft the size of the 35% Extra 300LX.
If you need the help of others in your club, ask those who you know
have the experience you need rather than taking the chance on whoever
may be present the day you go out for the initial flight. Get the help
you need and test every aspect of your airplane, then you can be
confident that you’re ready when you finally do get to that first flight.
Setup: Volume VI is the last installment of Project Extra and it will
help you get started with the process of setting up your airplane, but the
final outcome is entirely in your hands. No one can tell you exactly
how to set up your model to work just right for your personal
preferences. In fact, Erik Richards and I will be setting up two separate
programs/models on his radio for this Extra—one for his style of flying
and one for mine. Our preferences and styles are that different. Only
you know how you like your airplane to fly and feel.
Anyone setting up an aircraft of this size and caliber should have
plenty of experience with final adjustments by the time he or she gets
to this model. One of the last things to think about before flying an
airplane equipped with a gasoline engine (that you may not do with the
Erik Richard (standing) and Mike Hurley show off their completed Extra 300LXs. Erik’s is the one built throughout the
course of the construction articles.
June 2003 64
smaller models) is to Loctite all of the metalto-
metal hardware that does not need field
assembly. Use thread locker that is made for
hand-tool removal. That usually means the
blue formula, but check the label.
I’m assuming that you know about basic
preflight and finishing procedures for a new
aircraft: installing, charging, and checking
your batteries, sealing any exposed wood in
the engine compartment, range checking, and
other procedures common to modeling, so I
won’t go into those steps. But you know as an
experienced modeler that all of those things
are important for a successful aircraft. Again,
if you have questions, get help from someone
who has the experience. There’s a terrific
article on range checking at http://horizon.
hobbyshopnow.com/articles/1079.asp.
In this issue we’ll look at basic
programming for the Extra so that all of the
servos work together and you have some idea
of how to set up a large aerobatic airplane. I’ll
give you some guidelines for balance and
control throws and discuss standard trimming
for a precision aircraft. I’ll use the JR 10X
radio for the examples because that’s what I
use, but you can do most of these things with
any of today’s computer radios.
Refer to your transmitter’s instruction
manual, and remember that many functions
that perform the same tasks are referred to
with different names by the different
manufacturers. Each of these topics could
encompass an entire article in itself, so I’ll be
limited to the basics. You’ll want to expand
the information on your own with a little
experimentation, practice, and some help from
your friends. Another source of information
on how to set up an aerobatic airplane is
http://horizon.hobbyshopnow.com/articles/11
69.asp. Click on the PDF download for the
whole article.
Mixing: If you followed our plan for Project
Extra, the airplane uses two rudder servos
ganged inline and connected to a bellcrank for
the pull-pull system. I like to match my rudder
servos utilizing a multipoint mix in my
transmitter. Even with four servos on the
rudder of my 40% models, I match two sets of
two servos with MatchBoxes then use a
multipoint mix to match the two pairs.
With the JR 10X the two servos are
plugged into separate channels: Rudder and
Aux2. Since the servos will be hard connected
to each other, it’s important that each servo’s
full range of motion matches perfectly.
A multipoint mix has the advantage over
other methods, including MatchBoxes, in that
there are as many as five positions that can be
adjusted, and you can tailor the mixing points
to just those spots that need attention. For the
servo/bellcrank arrangement, first adjust the
linkages between the aft servo and the
bellcrank. As we discussed in Volume IV of
this series, the linkages must be centered and
run parallel to each other so that they have
equal movement without binding. Check that
there is no binding in any movement before
you power up any servos.
It’s also a good idea to have any servo
arms and linkages removed before powering
up a servo for the first time. We found some
interference between the ball link and the
bellcrank and had to add some washers to the
inside of the connection to spread the arms
slightly and make clearance. The bind was
not visually evident, and we wouldn’t have
found this problem if the servos had been
powered up.
Once the movement is clean, you can
install the second set of linkages, but don’t
connect them to the second servo arm just
yet. I like to adjust the linkage so I can see
the connection point looking through the hole
in the ball links. Then with the transmitter,
move through the travel and note where the
ball doesn’t follow the connection point
precisely. I usually adjust the endpoints and
neutral first. Most of the time that’s all that’s
needed, but if there are places during
transition that do not line up, create an
adjustment point and line it up. Bolt it up,
and you’re ready to hook the cables to the
rudder.
Follow the same basic procedures with
the ailerons, but the mix is done using the
MatchBox. The instructions that come with
the MatchBox are clear, and the procedure is
simple. The 10X has a preprogrammed mix
for dual elevators, and we used flaperons for
the ailerons so that differential mixing was
available if needed. I’ll write more about that
later.
Before we get to the point of setting up
any part of the radio, we need to ensure that
all of the controls are working in the correct
direction—especially the ailerons. Don’t go
any further until everything is correct!
Standing behind the airplane looking at it as
if it were flying away, move the aileron stick
left; the left aileron should be up and the right
aileron should be down. Move the stick right,
and the right aileron is up and the left aileron
is down. Do it now; don’t wait ’til later.
Control Throws: Here’s where things can
get sticky and settings will really vary with
each pilot’s personal abilities and
preferences. I use JR’s flight modes to
Field assembly is rather straightforward. Slide the wings onto the wing tube. Hook up
the servos. Fasten the wing to the fuselage, and bolt on the hatch.
With the proper setup and some practice, this Extra excels at 3-D maneuvers. Note the
extreme 45° elevator deflection.
June 2003 65
When ganging two servos for rudder pull-pull system, bolt one
end of control rod to servo arm; leave other open for alignment.
Make sure that your servos are correctly centered before you
make any adjustments. Erik used a set of dial calipers.
Be very careful to always check for correct control-surface
directions before the airplane leaves your shop.
Erik and Mike used a CRC deflection gauge to ensure the
desired (and equal) amount of deflection on both sides.
To ensure that the elevator deflection is equal in the center and
at its maximum endpoints, Erik used a set of carbon rods taped
to each elevator half as a pointer.
control all of my rates with a single switch. For me, using flight
modes helps me avoid confusion.
However, you should set up your radio close to the manner with
which you are most comfortable. After you get more comfortable with
the airplane, you can experiment with new switches and rate types,
such as flight modes. If you’re fairly new to 3-D, be sure to have a
quick and easy way to escape the 3-D setting, and never fly a new
model that does not have the option for a reduced-rate elevator.
For starters, let’s set up the Extra with two sets of control rates.
The elevator is the control that can get you into a lot of trouble fast, so
I’ll concentrate on that. We’ll have a standard rate for everyday flying,
which can be later optimized for precision, and a setting for maximum
control throw, which is the 3-D mode.
Setting surface deflection is another initial step where so many
pilots tend to rely on the TLAR (“that looks about right”) method. But
really, this stuff is critical to an airplane that flies in a neutral manner
and won’t fight your every input. For control setup I use CRC Throw
Meters to tell me, in degrees, exactly where the control surfaces are
set. The CRC gauges are available from Central Hobbies at
www.centralhobbies.com/.
One often-overlooked step in setup is matching aileron throw left
The Project Extra series is presented on the
AMA Web site at www.modelaircraft.org.
to right and up and down. It’s nice to have
two gauges for matching ailerons. Before
you adjust throw, match the neutral and
endpoints for the ailerons. I make these
adjustments at maximum deflection or 100%
travel. Then as you adjust the total throws or
rate settings, the control surfaces should stay
in sync.
To make sure the elevators are in sync,
Erik likes to use a 24-inch length of carbon
tubing taped to each elevator half as a
pointer. The carbon rod is stiff and does not
flex at this long length, so it stays accurate.
Line up the elevators at the counterbalances
to make sure they’re level, then tape the
tubes to the surface so that they point directly
to each other when centered. Erik used a
toothpick in the end of each tube for further
accuracy.
Move the surfaces slowly and watch for
differences along the length of travel; some
offset as the elevators move is normal. The
pointers are so long that a fairly large gap of,
say, a half inch only reflects a minute offset,
so don’t get too worried unless the
differences are huge. With the transmitter
you can now adjust the endpoints to match
perfectly at the extremes of each throw, and
you are assured of even elevator adjustment.
For the beginning setup and initial flight
testing, set the ailerons to 15° of throw each
way and the elevators to 20° each way. To
set the rudder, you must turn the fuselage on
its side with the wings and stabilizers
66 MODEL AVIATION
removed from the airplane. Initially set the
rudder to 35° each way. After you get
comfortable with the model, readjust all of the
deflections and settings to suit your flying
style.
The Dead Zone: Before we get into the setup
for 3-D, let’s discuss flying with huge throws
and some of the things to understand before
you try flying with 3-D throws the first time.
With a little bit of exponential, or “expo,” and
some experience, this Extra can be flown with
any amount of control throw. I fly mine on
full maximum 3-D rate all the time. That
includes takeoff, landing, and everything in
between. The only time I switch out of 3-D is
to fly a precision flight where I want more
exacting control of the airplane.
For a while I was starting to think that the
model couldn’t be induced to snap with
elevator alone and that anyone could fly it in
3-D mode, but I was brought back to reality
when I let a friend fly the airplane. My friend
was an experienced pilot who I trusted
completely, but he had never flown an
airplane set up for 3-D.
At first when I handed him the transmitter
set to precision rates, he had a ball doing
rolling loops, knife-edge circles, and multiple
snaps; you name it, and he was doing it! He
became comfortable with the airplane and
started to try some of the 3-D stuff that he had
seen me do. “You can’t do those things in low
rate,” I said. “I’ll switch to 3-D for you.” I hit
the switch, and the smile on his face started to
relax; he was beginning to look worried.
Suddenly just controlling the airplane
through a loop was difficult, and he snapped
the model without provocation within a
couple of seconds. “Shut it off!” he yelled,
and I hit the switch back to low rate. That
episode made me realize that, without
knowing it, I had become used to flying the
Extra in a manner that worked with extreme
surface deflection, but the model could still be
a handful to pilots who are just learning 3-D.
Don’t get caught in the trap. Some of you
may read the preceding account and think to
yourself, I’ll just tone it down a bit by
Defying the Limits
Learning to fly 3-D maneuvers is fun
and satisfying, and the Project Extra
model is a great aircraft with which to
learn 3-D. Another advantage is to gather
information to help you get started. If
you’d like to learn more about high-alpha
flight, 3-D maneuvers, aircraft
preparation, equipment, and setup,
Robin’s View Productions has released a
video called Defying the Limits, featuring
world-renowned 3-D and precision pilot
Jason Shulman. I developed and filmed
the video.
Defying the Limits is available on
DVD with convenient searchable
chapters. For more information or to
order the video, contact Robin’s View
Productions at (610) 746-0106. MA
—Mike Hurley
68 MODEL AVIATION
reducing the control throw and work up to
more throw as I get comfortable. That’s
exactly what can get you into more trouble.
The secret to entering and exiting 3-D is
to have the pitch authority to power past a
stalled attitude and hold it with massive
surfaces, deflection, and a powerful
propeller blast. If you tone it down by
lowering the surface deflection and try the
maneuver, the airplane won’t have the
required pitch authority and will stall. I call
the lowered surface deflection “the dead
zone.” The dead zone is too low for 3-D
and too high for precision control. The dead
zone will get you into trouble in a hurry.
Flying 3-D: When flying the model,
remember that you need to be committed to
getting into and out of a high-alpha (HA)
attitude. It’s important to have enough
airspeed or power to transition into a high
angle of attack. I’ve noticed that people get
into trouble when they move too slowly
into the transition or don’t use enough
elevator deflection or engine power.
I’m not saying you need to perform 3-D
maneuvers with a higher airspeed, but if the
speed is low you must use the power from
your engine to move the airplane’s tail into
position. Indeed you can slow the model to
a stall as long as you keep inducing the
power needed to keep the tail below the
airplane. At that point you can transition
into a hover with no forward airspeed.
Inversely, you can transition into HA with
power off if you maintain the airspeed to
pop your model into position, but once in
position you need to power up to hold
altitude.
Learning to fly into and out of HA
safely is the beginning of learning to fly 3-
D; it’s not hard to do, but it takes a little
finesse. If you’re not getting it quite right,
the aircraft will let you know with a nice
wing drop or an all-out snap.
My recommendation, even if you’re
experienced, is to start slow and use the rate
switch. Have enough expo dialed in to keep
the airplane controllable, and only switch
into 3-D mode to execute a specific 3-D
maneuver, then switch back to low rate to
fly out. Set your elevator to 45° for 3-D
deflection. The dead zone for the elevator is
27-37°; try to avoid those settings. For the
ailerons, you can 3-D nicely at 25-30°
deflection, and the rudder should be 45°.
There is no dead zone for the rudder or
ailerons.
Remember that these rates can get you
into trouble fast and are not recommended
for beginning pilots. If you have to
significantly reduce the travel on your radio
from 100% to get the ailerons down to 30° of
deflection, I recommend moving the controlrod
mounting position on the servo arm
inboard toward the output shaft until you get
the desired deflection with the radio
programmed to 100%.
Exponential: Expo is a program on most
computer radios that allows you to adjust a
nonlinearity of the stick movement relative
to the servo arm output. In most cases
pilots use expo to soften the feel of the
stick around the neutral position, especially
when there is a lot of surface deflection. To
create a softer feel you are moving a
portion of the servo travel to a different
area of the stick deflection—in this case,
farther out in the travel. So the servo moves
less near the center of the stick position and
exponentially moves more as the stick moves
toward full travel.
Here’s a funny fact that shows a need for
standardization. With a JR radio you want to
dial in positive expo for a softer neutral area,
but a negative value is needed with Futaba.
Be sure to read your owner’s manual!
Because I can’t climb into your shoes, I
cannot give you a positive starting point for
setting expo on this airplane. You will need
to do it for yourself. The trick is to set a value
and try it. Change one setting at a time and
find the value that works best for you.
Following is what I have set on my Extra
at max 3-D deflection: aileron, +50%;
elevator, +55%; and rudder +30%. I have
expo for precision too, but it’s slightly
different; aileron is +30%, elevator is +30%,
and rudder is +40%.
You can see that my rudder expo is higher
for precision than for 3-D. That’s to try to
smooth out any rudder wobble while flying
precision maneuvers. You can really effect
some big changes with expo that can gain big
advantages by smoothing out your flying
around the center of the stick while allowing
a large amount of control deflection right at
your fingers if you need it. There’s also the
possibility of too much of a good thing, so be
careful and don’t numb out the center of
your radio’s stick completely. Once you’re
comfortable with the airplane, give it a try
and don’t be afraid to experiment.
Balance: The center of gravity (CG) located
on the plans is conservative, at
approximately 32% of the chord at the mean
aerodynamic center (MAC). I fly my
airplane at this forward position, and it
works great for 3-D and precision flying.
It’s safe to locate the CG anywhere between
F3 and the forward edge of the wing tube
socket. I feel that, within limits, CG
location can be a personal preference. Many
of the top pilots fly with a forward CG for
precision and move the CG aft for freestyle.
Some people believe that you must have
a rear-biased CG to perform any 3-D
maneuvers; that simply is not true. In some
3-D maneuvers a rearward CG will slightly
enhance the model’s performance, but in
most other flight attitudes the performance
will suffer. I prefer to lose a tiny amount of
3-D performance to keep the rest of the
aircraft’s integrity intact, yet with practice
I’m able to perform any 3-D maneuver.
Trimming: Decidedly, trimming your
airplane for neutral flight is the difference
between a model that flies well and one that
you fight to keep on track. Trimming a
model properly is also one of the most
overlooked steps in readying it for
competition. Hey, it flies pretty well right
off the blocks, so why spend so much time
on a few minor changes? It does take a bit
of time to get everything right. I’ve spent
almost 100 flights getting one of my
competition airplanes to where I wanted it.
No, it wasn’t a problem airplane; on the
contrary, it was fantastic, and that’s why I
knew it had so much potential to be close to
perfect.
Some of the things you want to look for
are the ability to fly precision up- and
down-lines, 45s, and loops without the need
for stick input. There are many good
trimming procedures and charts available
that can take you step by step through the
procedure, and I would most likely be
doing you a disservice if I tried to make a
condensed version here, so take a look
online. You can download a chart from the
National Society of Radio Controlled
Aerobatics at www.nsrca.org/
trimA.htm. While you’re at it, take a look at
the Web site; these are the people who lead
the way in precision aerobatics.
Common Mixes: Most Scale Aerobatics
(SA) airplanes have some form of unwanted
coupling to the rudder. In an ideal scenario,
rudder movement would impart yaw only,
but with many Scale aircraft the rudder will
also effect some roll and/or some pitch.
Those are things we do not want for
precision flying, so it’s a common practice to
create a mix to trim those attributes out.
After you’re comfortable with how the
airplane flies, you can start to add these
trimming mixes.
For the rudder coupling, check the trim
by flying the airplane in knife edge. Set the
mix by flying at an even medium speed with
only enough rudder to sustain level knifeedge
flight. Many of today’s computer
radios have special mixes just for this
trimming procedure. I believe that all of
JR’s computer radios from the 662 up to the
10X have this specific feature.
The rudder is always the master channel.
Aileron will be slaved for roll, and elevator
will be slaved for pitch. The amount of mix
depends on your model and a variety of
dynamic forces that can change, such as
atmospheric density, balance, airspeed,
servo power, and so on. So no matter how
well you dial in the mix, it will never be
100% foolproof, and your model will more
than likely be somewhat different from the
next flier’s.
It’s also quite common for the mix for
left rudder to be slightly different from the
mix for right rudder, so you will have to trim
those tendencies out one step at a time. Our
Extra does not have any roll coupling, but
Scale aerobatic airplanes will commonly
have a 2-4% mix. This model does tuck
slightly, so I have 10% up-elevator mixed
for left and right rudder. That number would
decrease with a more rearward balance. To
be conservative, start with approximately
5% up if it tucks to the gear or down if it
pulls to the canopy, and decide from that
point if you need more or less mix.
I like to put my mix on a switch so it
can be defeated if necessary. The switch
could be useful when performing rolling
maneuvers such as a slow roll or a rolling
circle, where you are flying through the
maneuver with all of the controls in sync,
but (to be honest!) I leave the switch on all
the time.
More Mixes: Other mixes that are common
to SA aircraft are a throttle curve and aileron
differential. I don’t use either of them with
my airplane, but I thought it prudent to
touch on them here.
A throttle curve is used to make the
engine power feel more linear through the
entire range of stick motion. Since
carburetor butterfly position does not
usually translate to engine rpm, most of the
change in power comes at the lower end of
the stick movement. You can set a curve to
give you a more even feel. Some people use
this for torque rolling if the throttle is too
touchy at the hovering rpm range. I had
throttle curves in all of my models when I
flew at sea level, but since moving to the
high altitude in Colorado I’ve taken the
curves back out.
Aileron differential is a means to even
out the drag on each wing of the aircraft
while rolling. If one aileron has more drag
than the other it can cause the airplane to
yaw off line as it rolls, giving you a wobble.
Normally the down aileron creates more
drag than the up side, giving us what is
commonly known as adverse yaw. Most
differential programs work well at adjusting
the down aileron for either roll direction.
Actually seeing this happen can be tricky,
so often it comes down to extensive
experimentation until you get a roll that
looks good.
Before computer radios, pilots and
designers used to adjust differential by
changing the location of the aileron hinge
line! Can you imagine the work involved in
doing that for each adjustment? You can
also see the importance of starting with
properly set aileron deflection. The key to
making intelligent adjustments is knowing
what you have to start with. Our Extra has
an axial roll, so I have no differential
programmed into the airplane.
Ready to Fly! If all is going well and
Who would have ever imagined five
years ago when I started to dream about the
type of Scale aerobatic model I wanted for
myself that it would turn into a major project
I would be able to share with the whole
modeling community? It has been my hope
that you come away from reading this series
with new knowledge or ideas about your
own modeling experiences. And if you come
away from it with a new airplane, that’s so
much the better!
It’s been incredibly gratifying to read so
many letters and E-mails from AMA
members who have followed and enjoyed
the series, and it’s been equally gratifying to
be able to forge ahead essentially with a
blank sheet and help the MA staff create a
model for future Web-based construction
articles and start the ball rolling for an
information database that will spread to all
aspects of the hobby.
The entire process of bringing this
airplane to you and documenting it as the
construction progressed would not have been
possible without Erik Richard’s tireless
effort and perfectionism. When we started
this project for Model Aviation, Erik’s wife
Angela was newly expecting their first child.
Erik’s daughter Julia is a year old now!
Throughout it all, Erik’s commitment to the
project has been unwavering.
Oh, don’t think for a minute that he’s
going to have time to spend at home with
his family now. We have plenty more ideas
and projects ready to get started on, and we
can stay busy for a long, long time … MA
Mike Hurley
11542 Decatur Ct.
Westminster CO 80234
[email protected]
78 MODEL AVIATION
you’ve followed Project Extra through the
building process, you’re probably just
putting the last drops of Loctite on your
bolts and checking throw directions one
final time before you head out to the field
for the first flights with your new airplane.