126 MODEL AVIATION
Also included in this column:
• Programming Techniques 101
• Dealing with blowback
The Rolling Circle
[[email protected]]
Radio Control Scale Aerobatics John Glezellis
These are possible downgrades on the Rolling Circle according to IMAC rules.
A Composite-ARF Sukhoi performs a
low pass for the camera. This airplane is
a perfect candidate for this month’s
topic. Andreas Geitz photo.
Downgrades:
a: Performing more or fewer rolls than Aresti description
calls for or rolling in a direction different than depicted on the
Aresti results in the figure being zeroed.
b: All rolls in a rolling turn are standard rolls. If a snap roll
is performed, the figure is zeroed.
c: Each stoppage of the rate of roll is a deduction of one
(1) point.
d: Each variation in the rate of roll is a one (1) point
deduction.
e: Each variation in the rate of turn is a one (1) point
deduction.
f: Variations in altitude are deducted using 0.5 points per
every 5 degrees difference.
g: 0.5 points per every 5 degrees that the aircraft is not in
level flight when reversing roll direction.
h: 0.5 points per every 5 degrees of roll remaining when
the aircraft has reached its heading.
i: 0.5 points per every 5 degrees of turn remaining when
the aircraft has completed its last roll.
Shown here is the Aresti diagram for the
Two-Roll Rolling Circle.
BECAUSE the aerobatic flying season is in
full swing, I would like to break this month’s
column into a few different sections. First, I
will take a look at a Rolling Circle that can be
found in the 2011 Unlimited International
Miniature Aerobatic Club (IMAC) routine.
After I discuss the specifics on performing
this show-stopping stunt, I’ll examine various
programming techniques to assist you, as well
as a few things to watch out for.
Without further hesitation, let’s get down
to business!
The Two-Roll Rolling Circle: In the 2011
Unlimited schedule, one can find a Two-Roll
Rolling Circle, often referred to as a “roller”
in the aerobatic world, that starts and ends in
upright level flight. Note that roll directions
are critical.
In this maneuver, the first roll is performed
to the inside; the second roll is done to the
outside. This means that the first will roll to
the inside of the circle. If you were to fly your
aircraft parallel to the runway from right to
left, the first roll would be to the right and the
second roll to the left, provided that you wish
to push the circle out. Whether you are
planning to compete or are just trying to hone
your aerobatic flight skills, always begin this,
and similar maneuvers, parallel to the runway.
Throughout the circle, please ensure that
the cardinal points are met. For instance,
because this is a two-roll circle that begins
from upright level flight, as the aircraft
reaches the first quadrant, the model should be
inverted. Once it approaches the second
quadrant, it should be upright momentarily
until it starts the second roll in the opposite
direction, and so on.
08sig4xx_00MSTRPG.QXD 6/23/11 1:39 PM Page 126
August 2011 127
Blowback? Let’s discuss troubleshooting
this maneuver. Sometimes, you may run out
of rudder authority during the Two-Roll
Rolling Circle, especially if you need to
utilize a fair amount of engine power to meet
a given cardinal point in the circle.
If you need to use maximum rudder stick
and the airplane is still not responding to the
rudder input, you may be experiencing what
is called “blowback.” This means that
although you may obtain 45° of rudder
deflection on the ground, you may only have
20° in the air under load; you simply do not
have enough servo power or poor linkage
geometry exists.
Throughout the years, I’ve had airplanes
with multiple rudder-servo setups. When they
began their lives, they had more than enough
rudder authority; however, 300 or so flights
later, I would need to add more rudder input
to perform the same maneuver, and
sometimes I didn’t have enough rudder!
If you find this is the case, check the
rudder servos. Sometimes, a rudder servo
may strip a gear or you simply may not have
enough rudder authority/power. In that case,
choose a servo that has more torque or look
at different mounting options.
For a typical 40% airplane when using
“pull-pull,” I prefer to use three servos, and
that is with servos that have nearly 500 inchounce
of torque. When using “push-pull,” I
only employ two servos optimally installed in
the tail of the aircraft. Interestingly, servos
can fail as they become weary in time.
Final Thoughts: In closing, you have now
had a brief introduction into the world of
rollers. Rolling Circles are elegant to watch
when performed correctly, but they are
demanding on the pilot. Performing a roller
Finally, the maneuver should be centered
on the pilot, which means that it will begin
and end directly in front of the pilot.
Now, let me discuss control inputs.
Depending on your aircraft’s power-to-weight
ratio, you will need to adjust your throttle
setting accordingly. However, as a starting
point, use 70% throttle.
If you are flying from right to left, start
this maneuver with a right roll. As the airplane
passes directly in front your pilot position,
gently apply right aileron input to initiate the
roll. At first you will have to hold left top
rudder and up-elevator to keep the airplane
rolling and pulling into the first quadrant of
the circle. Adding rudder and elevator at the
proper times helps keep the circle shape and
ensures that there is no loss in altitude.
As the airplane passes the first quadrant,
hold left rudder to make the airplane come
around. When it passes approximately 60% of
the first roll, apply right rudder and elevator
input as needed to keep both heading and
altitude. The first roll should be complete
directly in front of you; once this is
accomplished, begin a roll to the left.
Start by adding left aileron and right top
rudder, and elevator as needed, to maintain
altitude and heading around the circle. As the
model nears the third quadrant, hold left
rudder. The amount will vary depending on
the aircraft’s throttle setting as well as how
close it is to meeting the next cardinal point of
the circle.
When the maneuver is complete, the
airplane should stop its second roll directly in
front of the pilot. This is a maneuver that takes
time to master and a certain rhythm must exist
between the pilot and his or her aircraft so that
the airplane does not look “forced.” One
constant roll rate should exist throughout.
The throttle amount you need throughout
this maneuver will vary depending on your
model and the flight conditions. If you are
starting this maneuver into a strong headwind,
enter with more power until you perform 25%
of the circle. At that point, decrease throttle
because the wind will “push” the aircraft.
At the 50% point, you may have to utilize
the rudder and elevator control functions more
to prevent the model from being pushed.
After you have 75% of the maneuver
completed, you will need to add more power.
Next, let’s talk shop!
Programming Techniques 101: Now that
you understand the basics of performing the
Two-Roll Rolling Circle, let’s discuss my
radio setup. If you read my columns, you
know that I prefer to assign my aileron,
elevator, and rudder rates to one switch. For a
maneuver such as the Rolling Circle, I prefer
to use a flight mode that has maximum
rudder, but only roughly 15° of elevator, and
approximately 30° of aileron deflection.
Although my exponential settings vary
from airplane to airplane, I average roughly
30-40% of exponential on the aileron and
elevator surface, and 50% or so of exponential
on the rudder surface.
If you are new to aerobatics, you may not
have heard of the term “exponential.” By
definition in the RC world, exponential is an
adjustment to the actual curve of how the
inputs are given to a servo in relation to how
you move that servo’s control stick. If your
airplane is extremely sensitive to any change
in rudder deflection, you may have to add
exponential to soften the servo’s feel around
neutral.
Remember that JR radios utilize positive
exponential and Futaba radios use negative
exponential to achieve the same purpose.
Always consult the instruction manual
supplied with your radio before attempting to
add exponential of any sort.
I employ two rudder servos using pull-pull on my Composite-ARF Edge 540. If you are
using a similar rudder setup and notice that there is a significant loss in rudder authority
over time, check both servos to make sure that one doesn’t have a stripped gear.
On my Hangar 9 3.1m Sukhoi Su-26MM, I
use two JR DS8911HV servos to power
the rudder. Both are mounted in the tail,
providing stunning rudder authority using
direct voltage from a two-cell lithium
battery.
08sig4xx_00MSTRPG.QXD 6/23/11 1:40 PM Page 127
to perfection will take a novice pilot endless
hours of practice; however, like all things in
life, practice makes perfect.
On the contrary, if you are an experienced
pilot and you find yourself facing a consistent
problem such as the rudder scenario I
mentioned, look at the setup of your aircraft.
Something may be wrong. You should only
seek the advice from fellow expert modelers
or write to me!
Until next time, fly hard! MA
Sources:
IMAC
www.mini-iac.com
Composite-ARF Models
www.carf-models.com
Futaba
(800) 637-7660
www.futaba-rc.com
Horizon Hobby
(800) 338-4639
www.horizonhobby.com
Edition: Model Aviation - 2011/08
Page Numbers: 126,127,128
Edition: Model Aviation - 2011/08
Page Numbers: 126,127,128
126 MODEL AVIATION
Also included in this column:
• Programming Techniques 101
• Dealing with blowback
The Rolling Circle
[[email protected]]
Radio Control Scale Aerobatics John Glezellis
These are possible downgrades on the Rolling Circle according to IMAC rules.
A Composite-ARF Sukhoi performs a
low pass for the camera. This airplane is
a perfect candidate for this month’s
topic. Andreas Geitz photo.
Downgrades:
a: Performing more or fewer rolls than Aresti description
calls for or rolling in a direction different than depicted on the
Aresti results in the figure being zeroed.
b: All rolls in a rolling turn are standard rolls. If a snap roll
is performed, the figure is zeroed.
c: Each stoppage of the rate of roll is a deduction of one
(1) point.
d: Each variation in the rate of roll is a one (1) point
deduction.
e: Each variation in the rate of turn is a one (1) point
deduction.
f: Variations in altitude are deducted using 0.5 points per
every 5 degrees difference.
g: 0.5 points per every 5 degrees that the aircraft is not in
level flight when reversing roll direction.
h: 0.5 points per every 5 degrees of roll remaining when
the aircraft has reached its heading.
i: 0.5 points per every 5 degrees of turn remaining when
the aircraft has completed its last roll.
Shown here is the Aresti diagram for the
Two-Roll Rolling Circle.
BECAUSE the aerobatic flying season is in
full swing, I would like to break this month’s
column into a few different sections. First, I
will take a look at a Rolling Circle that can be
found in the 2011 Unlimited International
Miniature Aerobatic Club (IMAC) routine.
After I discuss the specifics on performing
this show-stopping stunt, I’ll examine various
programming techniques to assist you, as well
as a few things to watch out for.
Without further hesitation, let’s get down
to business!
The Two-Roll Rolling Circle: In the 2011
Unlimited schedule, one can find a Two-Roll
Rolling Circle, often referred to as a “roller”
in the aerobatic world, that starts and ends in
upright level flight. Note that roll directions
are critical.
In this maneuver, the first roll is performed
to the inside; the second roll is done to the
outside. This means that the first will roll to
the inside of the circle. If you were to fly your
aircraft parallel to the runway from right to
left, the first roll would be to the right and the
second roll to the left, provided that you wish
to push the circle out. Whether you are
planning to compete or are just trying to hone
your aerobatic flight skills, always begin this,
and similar maneuvers, parallel to the runway.
Throughout the circle, please ensure that
the cardinal points are met. For instance,
because this is a two-roll circle that begins
from upright level flight, as the aircraft
reaches the first quadrant, the model should be
inverted. Once it approaches the second
quadrant, it should be upright momentarily
until it starts the second roll in the opposite
direction, and so on.
08sig4xx_00MSTRPG.QXD 6/23/11 1:39 PM Page 126
August 2011 127
Blowback? Let’s discuss troubleshooting
this maneuver. Sometimes, you may run out
of rudder authority during the Two-Roll
Rolling Circle, especially if you need to
utilize a fair amount of engine power to meet
a given cardinal point in the circle.
If you need to use maximum rudder stick
and the airplane is still not responding to the
rudder input, you may be experiencing what
is called “blowback.” This means that
although you may obtain 45° of rudder
deflection on the ground, you may only have
20° in the air under load; you simply do not
have enough servo power or poor linkage
geometry exists.
Throughout the years, I’ve had airplanes
with multiple rudder-servo setups. When they
began their lives, they had more than enough
rudder authority; however, 300 or so flights
later, I would need to add more rudder input
to perform the same maneuver, and
sometimes I didn’t have enough rudder!
If you find this is the case, check the
rudder servos. Sometimes, a rudder servo
may strip a gear or you simply may not have
enough rudder authority/power. In that case,
choose a servo that has more torque or look
at different mounting options.
For a typical 40% airplane when using
“pull-pull,” I prefer to use three servos, and
that is with servos that have nearly 500 inchounce
of torque. When using “push-pull,” I
only employ two servos optimally installed in
the tail of the aircraft. Interestingly, servos
can fail as they become weary in time.
Final Thoughts: In closing, you have now
had a brief introduction into the world of
rollers. Rolling Circles are elegant to watch
when performed correctly, but they are
demanding on the pilot. Performing a roller
Finally, the maneuver should be centered
on the pilot, which means that it will begin
and end directly in front of the pilot.
Now, let me discuss control inputs.
Depending on your aircraft’s power-to-weight
ratio, you will need to adjust your throttle
setting accordingly. However, as a starting
point, use 70% throttle.
If you are flying from right to left, start
this maneuver with a right roll. As the airplane
passes directly in front your pilot position,
gently apply right aileron input to initiate the
roll. At first you will have to hold left top
rudder and up-elevator to keep the airplane
rolling and pulling into the first quadrant of
the circle. Adding rudder and elevator at the
proper times helps keep the circle shape and
ensures that there is no loss in altitude.
As the airplane passes the first quadrant,
hold left rudder to make the airplane come
around. When it passes approximately 60% of
the first roll, apply right rudder and elevator
input as needed to keep both heading and
altitude. The first roll should be complete
directly in front of you; once this is
accomplished, begin a roll to the left.
Start by adding left aileron and right top
rudder, and elevator as needed, to maintain
altitude and heading around the circle. As the
model nears the third quadrant, hold left
rudder. The amount will vary depending on
the aircraft’s throttle setting as well as how
close it is to meeting the next cardinal point of
the circle.
When the maneuver is complete, the
airplane should stop its second roll directly in
front of the pilot. This is a maneuver that takes
time to master and a certain rhythm must exist
between the pilot and his or her aircraft so that
the airplane does not look “forced.” One
constant roll rate should exist throughout.
The throttle amount you need throughout
this maneuver will vary depending on your
model and the flight conditions. If you are
starting this maneuver into a strong headwind,
enter with more power until you perform 25%
of the circle. At that point, decrease throttle
because the wind will “push” the aircraft.
At the 50% point, you may have to utilize
the rudder and elevator control functions more
to prevent the model from being pushed.
After you have 75% of the maneuver
completed, you will need to add more power.
Next, let’s talk shop!
Programming Techniques 101: Now that
you understand the basics of performing the
Two-Roll Rolling Circle, let’s discuss my
radio setup. If you read my columns, you
know that I prefer to assign my aileron,
elevator, and rudder rates to one switch. For a
maneuver such as the Rolling Circle, I prefer
to use a flight mode that has maximum
rudder, but only roughly 15° of elevator, and
approximately 30° of aileron deflection.
Although my exponential settings vary
from airplane to airplane, I average roughly
30-40% of exponential on the aileron and
elevator surface, and 50% or so of exponential
on the rudder surface.
If you are new to aerobatics, you may not
have heard of the term “exponential.” By
definition in the RC world, exponential is an
adjustment to the actual curve of how the
inputs are given to a servo in relation to how
you move that servo’s control stick. If your
airplane is extremely sensitive to any change
in rudder deflection, you may have to add
exponential to soften the servo’s feel around
neutral.
Remember that JR radios utilize positive
exponential and Futaba radios use negative
exponential to achieve the same purpose.
Always consult the instruction manual
supplied with your radio before attempting to
add exponential of any sort.
I employ two rudder servos using pull-pull on my Composite-ARF Edge 540. If you are
using a similar rudder setup and notice that there is a significant loss in rudder authority
over time, check both servos to make sure that one doesn’t have a stripped gear.
On my Hangar 9 3.1m Sukhoi Su-26MM, I
use two JR DS8911HV servos to power
the rudder. Both are mounted in the tail,
providing stunning rudder authority using
direct voltage from a two-cell lithium
battery.
08sig4xx_00MSTRPG.QXD 6/23/11 1:40 PM Page 127
to perfection will take a novice pilot endless
hours of practice; however, like all things in
life, practice makes perfect.
On the contrary, if you are an experienced
pilot and you find yourself facing a consistent
problem such as the rudder scenario I
mentioned, look at the setup of your aircraft.
Something may be wrong. You should only
seek the advice from fellow expert modelers
or write to me!
Until next time, fly hard! MA
Sources:
IMAC
www.mini-iac.com
Composite-ARF Models
www.carf-models.com
Futaba
(800) 637-7660
www.futaba-rc.com
Horizon Hobby
(800) 338-4639
www.horizonhobby.com
Edition: Model Aviation - 2011/08
Page Numbers: 126,127,128
126 MODEL AVIATION
Also included in this column:
• Programming Techniques 101
• Dealing with blowback
The Rolling Circle
[[email protected]]
Radio Control Scale Aerobatics John Glezellis
These are possible downgrades on the Rolling Circle according to IMAC rules.
A Composite-ARF Sukhoi performs a
low pass for the camera. This airplane is
a perfect candidate for this month’s
topic. Andreas Geitz photo.
Downgrades:
a: Performing more or fewer rolls than Aresti description
calls for or rolling in a direction different than depicted on the
Aresti results in the figure being zeroed.
b: All rolls in a rolling turn are standard rolls. If a snap roll
is performed, the figure is zeroed.
c: Each stoppage of the rate of roll is a deduction of one
(1) point.
d: Each variation in the rate of roll is a one (1) point
deduction.
e: Each variation in the rate of turn is a one (1) point
deduction.
f: Variations in altitude are deducted using 0.5 points per
every 5 degrees difference.
g: 0.5 points per every 5 degrees that the aircraft is not in
level flight when reversing roll direction.
h: 0.5 points per every 5 degrees of roll remaining when
the aircraft has reached its heading.
i: 0.5 points per every 5 degrees of turn remaining when
the aircraft has completed its last roll.
Shown here is the Aresti diagram for the
Two-Roll Rolling Circle.
BECAUSE the aerobatic flying season is in
full swing, I would like to break this month’s
column into a few different sections. First, I
will take a look at a Rolling Circle that can be
found in the 2011 Unlimited International
Miniature Aerobatic Club (IMAC) routine.
After I discuss the specifics on performing
this show-stopping stunt, I’ll examine various
programming techniques to assist you, as well
as a few things to watch out for.
Without further hesitation, let’s get down
to business!
The Two-Roll Rolling Circle: In the 2011
Unlimited schedule, one can find a Two-Roll
Rolling Circle, often referred to as a “roller”
in the aerobatic world, that starts and ends in
upright level flight. Note that roll directions
are critical.
In this maneuver, the first roll is performed
to the inside; the second roll is done to the
outside. This means that the first will roll to
the inside of the circle. If you were to fly your
aircraft parallel to the runway from right to
left, the first roll would be to the right and the
second roll to the left, provided that you wish
to push the circle out. Whether you are
planning to compete or are just trying to hone
your aerobatic flight skills, always begin this,
and similar maneuvers, parallel to the runway.
Throughout the circle, please ensure that
the cardinal points are met. For instance,
because this is a two-roll circle that begins
from upright level flight, as the aircraft
reaches the first quadrant, the model should be
inverted. Once it approaches the second
quadrant, it should be upright momentarily
until it starts the second roll in the opposite
direction, and so on.
08sig4xx_00MSTRPG.QXD 6/23/11 1:39 PM Page 126
August 2011 127
Blowback? Let’s discuss troubleshooting
this maneuver. Sometimes, you may run out
of rudder authority during the Two-Roll
Rolling Circle, especially if you need to
utilize a fair amount of engine power to meet
a given cardinal point in the circle.
If you need to use maximum rudder stick
and the airplane is still not responding to the
rudder input, you may be experiencing what
is called “blowback.” This means that
although you may obtain 45° of rudder
deflection on the ground, you may only have
20° in the air under load; you simply do not
have enough servo power or poor linkage
geometry exists.
Throughout the years, I’ve had airplanes
with multiple rudder-servo setups. When they
began their lives, they had more than enough
rudder authority; however, 300 or so flights
later, I would need to add more rudder input
to perform the same maneuver, and
sometimes I didn’t have enough rudder!
If you find this is the case, check the
rudder servos. Sometimes, a rudder servo
may strip a gear or you simply may not have
enough rudder authority/power. In that case,
choose a servo that has more torque or look
at different mounting options.
For a typical 40% airplane when using
“pull-pull,” I prefer to use three servos, and
that is with servos that have nearly 500 inchounce
of torque. When using “push-pull,” I
only employ two servos optimally installed in
the tail of the aircraft. Interestingly, servos
can fail as they become weary in time.
Final Thoughts: In closing, you have now
had a brief introduction into the world of
rollers. Rolling Circles are elegant to watch
when performed correctly, but they are
demanding on the pilot. Performing a roller
Finally, the maneuver should be centered
on the pilot, which means that it will begin
and end directly in front of the pilot.
Now, let me discuss control inputs.
Depending on your aircraft’s power-to-weight
ratio, you will need to adjust your throttle
setting accordingly. However, as a starting
point, use 70% throttle.
If you are flying from right to left, start
this maneuver with a right roll. As the airplane
passes directly in front your pilot position,
gently apply right aileron input to initiate the
roll. At first you will have to hold left top
rudder and up-elevator to keep the airplane
rolling and pulling into the first quadrant of
the circle. Adding rudder and elevator at the
proper times helps keep the circle shape and
ensures that there is no loss in altitude.
As the airplane passes the first quadrant,
hold left rudder to make the airplane come
around. When it passes approximately 60% of
the first roll, apply right rudder and elevator
input as needed to keep both heading and
altitude. The first roll should be complete
directly in front of you; once this is
accomplished, begin a roll to the left.
Start by adding left aileron and right top
rudder, and elevator as needed, to maintain
altitude and heading around the circle. As the
model nears the third quadrant, hold left
rudder. The amount will vary depending on
the aircraft’s throttle setting as well as how
close it is to meeting the next cardinal point of
the circle.
When the maneuver is complete, the
airplane should stop its second roll directly in
front of the pilot. This is a maneuver that takes
time to master and a certain rhythm must exist
between the pilot and his or her aircraft so that
the airplane does not look “forced.” One
constant roll rate should exist throughout.
The throttle amount you need throughout
this maneuver will vary depending on your
model and the flight conditions. If you are
starting this maneuver into a strong headwind,
enter with more power until you perform 25%
of the circle. At that point, decrease throttle
because the wind will “push” the aircraft.
At the 50% point, you may have to utilize
the rudder and elevator control functions more
to prevent the model from being pushed.
After you have 75% of the maneuver
completed, you will need to add more power.
Next, let’s talk shop!
Programming Techniques 101: Now that
you understand the basics of performing the
Two-Roll Rolling Circle, let’s discuss my
radio setup. If you read my columns, you
know that I prefer to assign my aileron,
elevator, and rudder rates to one switch. For a
maneuver such as the Rolling Circle, I prefer
to use a flight mode that has maximum
rudder, but only roughly 15° of elevator, and
approximately 30° of aileron deflection.
Although my exponential settings vary
from airplane to airplane, I average roughly
30-40% of exponential on the aileron and
elevator surface, and 50% or so of exponential
on the rudder surface.
If you are new to aerobatics, you may not
have heard of the term “exponential.” By
definition in the RC world, exponential is an
adjustment to the actual curve of how the
inputs are given to a servo in relation to how
you move that servo’s control stick. If your
airplane is extremely sensitive to any change
in rudder deflection, you may have to add
exponential to soften the servo’s feel around
neutral.
Remember that JR radios utilize positive
exponential and Futaba radios use negative
exponential to achieve the same purpose.
Always consult the instruction manual
supplied with your radio before attempting to
add exponential of any sort.
I employ two rudder servos using pull-pull on my Composite-ARF Edge 540. If you are
using a similar rudder setup and notice that there is a significant loss in rudder authority
over time, check both servos to make sure that one doesn’t have a stripped gear.
On my Hangar 9 3.1m Sukhoi Su-26MM, I
use two JR DS8911HV servos to power
the rudder. Both are mounted in the tail,
providing stunning rudder authority using
direct voltage from a two-cell lithium
battery.
08sig4xx_00MSTRPG.QXD 6/23/11 1:40 PM Page 127
to perfection will take a novice pilot endless
hours of practice; however, like all things in
life, practice makes perfect.
On the contrary, if you are an experienced
pilot and you find yourself facing a consistent
problem such as the rudder scenario I
mentioned, look at the setup of your aircraft.
Something may be wrong. You should only
seek the advice from fellow expert modelers
or write to me!
Until next time, fly hard! MA
Sources:
IMAC
www.mini-iac.com
Composite-ARF Models
www.carf-models.com
Futaba
(800) 637-7660
www.futaba-rc.com
Horizon Hobby
(800) 338-4639
www.horizonhobby.com
