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Ryan
Taylor and John Heigl both fly 39% Radiocraft Extras in the
unlimited category. The airplanes
have wingspans of 123 inches, weight is
around 38 lbs, and power is
supplied by 150cc engines.
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Let’s
face it, we are all aviation nut cases. We grew up with the
dream that if we had the opportunity to fly Thunderbolts,
Corsairs, and Mustangs in World War II, we would be elbowing
with Gabby and Pappy and Chuck. As time went on we learned
about Duane, Betty, Henry, Leo, and Charlie and what they were
doing in the world of competitive aerobatics. These
world-class pilots became our new heroes, and the fact that
you are reading Sport Aerobatics means you are involved
in some way with aerobatics. For some of you, that might mean
you fly aerobatics for recreation or competition, that you
help in the all-important duties of judging and running a
contest, or that as a growing number of IAC members are
doing, you fly scale aerobatics with radio-controlled model
aircraft.
IMAC History
IMAC (International
Miniature Aerobátic Club) is the organization that grew out
of the interest of flying scale aerobatics. The group was
founded in 1974 with 97 charter members. Their intent was to
emulate the IAC, which was dominated by biplanes at the time,
so the IMAC initially called themselves the National Sport
Biplane Association. In 1976 the National Sport Biplane
Association became affiliated with the IAC and became IMAC.
In the next few
years, membership in IMAC grew, and more model aircraft
manufacturers began producing scale acrobatic aircraft. The
Pitts still was popular, but monoplanes like Leo’s Laser and
CAP 21s were also being built. At this time (early to
mid-80s), most of the scale aerobatic models used in
competition were 1/4 scale or less, meaning they had wingspans
between 60 and 80 inches and engines ranging from 0.60 to 2.0
cubic inches running on model airplane fuel (glow fuel).
In the late 80s and
early 90s, new high-performance mono-planes began to appear on
the IAC flight line and also at IMAC contests. Extras, Sukhois,
and CAPs became the hot ride of choice. Here is one major
advantage of flying models over their full-scale counterparts—the
price difference between a clipped-wing Cub and an Extra is a
nonissue!
During the 90s every
kit manufacturer was producing these hot rods in sizes from
1/6 scale to 35 percent scale (54- to 105-inch wingspans),
with the larger aircraft powered by gas engines in the 2.4-to
6.0-cubic-inch range. These scale acrobatic aircraft were very
popular with all modelers. This trend was helpful to IMAC.
Formerly, the soley recognized form of model aerobatic
competition involved "pattern" aircraft that
appeared dissimilar to their full-size cousins- narrow,
ultra streamlined, and unnaturally long moments.
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Rich Rottenberk and his 33 percent
Ohio RC Extra 300L.
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For IMAC, the only
aircraft requirement for classes above Basic is that it is a
faithful scale model of a known aerobatic aircraft. With all
the Extras, CAPs, and Sukhois out on the market, many fliers
already had what was needed to be competitive, so IMAC
membership grew steadily. From the late 90s to the present,
growth was not only in membership, but also in the size of the
airplanes themselves. It’s not a shock to see models 40 to
46 percent scale on the IMAC flight line. These large scale
models are powered by twin-cylinder gas engines that are 9.0
cubic inches (150 cc) and produce close to 20 hp!
You might ask why so
big and will they get bigger? For the first question, size
does count. Big tends to fly and present better than small.
But size alone does not make you a winner. Many contests still
are won, even in the upper classes, by smaller aircraft flown
by highly skilled pilots. For the second question, I would say
we have reached the max size. Our sanctioning body, the
Academy Model Aeronautics (AMA), limits takeoff weight to 55
pounds. Typically, 40 percent aircraft weigh 35 to 40 pounds,
and this combination of power, weight, and size perform the
best.
IMAC
Contests—How They Compare to lAC
First let me quote
the opening rule in the IMAC rule book. Objective: To
duplicate full-scale sport aerobatics with miniature
radio-controlled aircraft in a realistic manner that is
challenging for the contestants as well as interesting for the
spectators.
From this statement
you can see why many IMAC members also are IAC members. Our
rules and sequences match very closely. We do have some
inherent differences we take into consideration. The most
obvious, besides size and cash outlay, is that we fly with
both feet on the ground! This has some advantages and
disadvantages. Because we generally don’t gray or red out
from G loads (I always say we only gray out after a crash),
our sequences in the upper classes will have more snap and
outside figures. However, since we are not in the cockpit,
some figures like rollers and tailslides are more difficult.
Because we fly remotely and our aircraft are more affected by
the wind, the judging downgrade is one point for every
10-degree deviation instead of the lAC’s 5-degree deviation.
One of the other distinctions is that we wind correct all our
figures. Because we are on the ground, we can control flight
path and correct for drift, even in uplines.
IMAC has four
classes: Basic, Sportsman, Advanced, and Unlimited. Our class
structure is similar to IAC’s, except our Basic flies a
sequence that more closely matches the lAC Sportsman. IMAC
Sportsman is based on the IAC Intermediate sequence. Advanced
and Unlimited follow the same sequence as JAG. The IMAC and
IAC boards have a very good working relationship. Because of
this relationship, IMAC typically receives the new year's
sequences upon IAC approval. The IMAC board then reviews the
sequences and make changes to meet the needs of scale
aerobatics.
IMAC contests are
much like IAC contests, but for a few differences:
- IMAC
aerobatic box is 1,800 by 1,000 feet with a 20-foot minimum
altitude and a 60-degree line-of- sight maximum altitude.
-
All classes fly
Knowns. Sportsman, Advanced, and Unlimited also fly a round of
Unknowns. IMAC does not fly a Free program.
- Generally, at most
contents each pilot will fly the Known sequence twice in each
round. Unknown sequences only are flown once.
- A 3-Minute Freestyle
might be offered and flown as a separate event.
- IMAC usually relies
upon contestant judging, but many IAC judges find IMAC judging
enjoyable and useful in keeping current.
- It is quite common at
most contests to fly two flight lines. Two different classes
will fly at the same time.
- Pilots will have a
"caller" nearby to remind him or her of the figures
required and also to act as a safety spotter for other
aircraft.
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Part
of the flight at the 2000
Nationals in Muncie, Indiana.
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We have divided the
country into six regions. Each region runs a season series
with a point system to award year-end champions. My North
Central region will have 17 contests this summer, almost one
every weekend. This year’s National IMAC/AMA Championship
will be in Muncie, Indiana, July 12-15.
Even though it is
competition, fun seems to be the common goal. It is not
unusual for a pilot to lend equipment or aircraft to a fellow
pilot that has trouble with his or hers. Much the same as in
the IAC, all of the contestants across the country know one
another; it's like a big family.
NUTS and Bolts
What is involved
technically and financially with an inexpensive smaller size
aircraft and, at the other end, an all-out, spare-no-expense
40 percent ship? For the smaller aircraft I will use a 25
percent scale CAP 232 that is made by Sig Manufacturing. This
kit is one of the more popular ARF (almost ready-to-fly) kits.
It has a wingspan of 73 inches and a ready-to-fly weight of
about 11 pounds. ARF means the airframe comes pre-built and
covered. All you have to do is some minor assembly, like
installing the engine and radio gear. This CAP sells for about
$350. The cost for a good 1.8-cubic-inch, two- or four-stroke
engine is around $400. You also will need at least five
high-quality servos, setting you back another $400. A simple
$100 radio will work, but you are much better off spending the
extra bucks for a basic computer radio ($400). So for a total
of $1,550 you can be competitive in IMAC.
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Joe
DiDia and his 25 percent CAP 231 EX and
Jim Gatewood and his 46 percent CAP 232.
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On the other end of
the spectrum is a 40 percent (116-inch wingspan) CAP 232 made
by Carden Aircraft. This is a kit in the more traditional
sense, since you must build from plans with balsa,
spruce, ply, and foam. The lower part of the fuselage is built
up from these woods with formers and longerons as in a
full-scale airplane. The front and rear turtledecks, wings,
and tail group are foam core that is sheeted with balsa. The
wings and stabilizer are removed for transportation. The cost
of this kit is about $1,000. You will need another $400 just
for hardware, glue, covering, and other nickel-and-dime items.
This aircraft will need one of the 150-cc twin-cylinder gas
monsters ($1,600). You need the best servos you can get and
many of them. Typically that means three to four for the
rudder, two for the elevators, two on each aileron, and one
more for the throttle. That’s ii servos, and the best ones
run about $115 each, totaling $1,265. Other miscellaneous
items like a carbon fiber prop and spinner, servo leads,
batteries, switches, etc. will add another $600. The total for
this big ride is a little under $5,000, and that’s without
the radio transmitter. Pilots who fly these 40 percent
aircraft tend to buy the top of the line computer radio, so
add $1,500. You could spend even more money and buy an
all-composite airframe. That airframe alone can run as high as
$5,000, and you still need the same items as the wood kit to
complete it. To some this might sound expensive, but when I
hear how much an MT or Hartzell three-blade propeller goes
for, we look positively parsimonious.
Performance
This is where the
scale models really excel. How would you like a
thrust-to-weight ratio greater than i-to-i? I believe Wayne
Handley’s Turbo Raven was the first and only full-scale
aerobat to achieve this goal. With our
models, 2-to-i is very typical, and some are close to 3-to-i!
Can you say vertical? In the above example, the 40 percent CAP
has a finished weight of about 38 pounds, and the thrust of
the 150-cc engine would be close to 100 pounds. What this
means is that our flying style is a little different than
full-scale, with many of our figures flown at half power or
less. Full power is used mostly for the vertical figures.
To fully experience
the power these scale models have, come to an IMAC meet and
watch the Freestyle event. We can pull some incredible
maneuvers, including some really wild stuff called
"3-i)." How about starting a torque roll at 10 feet
AGL and letting it slide down to the runway (torque rolling
all the way), touching the rudder on the ground, and then
going to full power, shooting up like a bottle rocket? Or how
about doing the "elevator?" This is a very high
alpha maneuver where the aircraft is pitched up to about 60
degrees with zero ground speed and then descends to a landing.
There are many more figures, and this style of flying could be
the subject of an article itself.
IAC and
IMAC Working Together
IMAC members
usually attend IAC’s Intro to Judging schools. This has been
a great help in training IMAC judges. Along with seven other
IMAC members, I was able to attend Brian Howard’s intro
class in 1999 hosted by IAC Chapter 88. I have been an TAC
member since 1995 and also a member of Chapter 88 since 1998.
The members of Chapter 88 have shown continued support for
local IMAC events by serving as judges. The IAC judges seem to
enjoy and benefit from the experience. This is appreciated,
and to return the favor, IMAC members volunteer at Chapter 88
contests. As a matter of fact, we are so tied together that
our local IMAC Chapter also is called 88 in reference to our
big brother.
A most recent example
of cooperation between the IMAC and IAC boards is the writing
of our proposed Flying and Judging Guide (F&JG). Our
present document is very outdated, and IMAC was allowed by IAC
and further endorsed by FAI/CIVA to use the JAG Red Book as a
template for our new F&JG. A big thanks to Rob Dorsey,
Brian Howard, Mike Heuer, and Fred Johnson for helping IMAC
Rules Chairman Ben Perreau create and check our new F&JG.
For more information
about IMAC, please go to our website at www.mini-iac.com.
From there you can click on your region and check out the
contest schedule in your area, or you can use the pull-down
menu for more information, pictures, and videos.
Sharing Common
Goals - IAC and IMAC
Anna Wood IAC 17966
Over the last few
years the Phoenix Aerobatic Club and the Southern Arizona
Aerobatic Club have been working to build stronger ties with
the International Miniature Aerobatic Club (IMAC) fliers here
in Arizona. Between our two IAC Chapters, we have many MAC
members and RC fliers within our ranks. Several of the MAC
fliers participate in IAC contests as full-scale pilots. The
IMAC pilots also participate in our sport as judges and as
volunteers at our local aerobatic contests.
In Phoenix, two of
the more active participants in IMAC flying, Jim Dornberger
and John Heigl, first started coming to our aerobatic contests
out of curiosity of what our sport was about. One of the main
missions of IMAC flying is presenting a scale version of
full-scale aerobatics—flying scale versions of competition
aerobatic aircraft—using the IAC Red Book for their
standard. What better way to understand the goal of their
sport than by participating in full-scale contests?
It was a very
eye-opening experience for them. Their impressions were that
AC conte~ts are very well run operations, with our IAC Red
Book providing the framework for judging and running a
contest. This, of course, led to them aft ending our IAC
judges’ school and working toward getting their IAC judge
certifications. They have also held judging seminars the past
few years for the local IMAC fliers. IMAC does not have a
formal training program for judges, and the seminars have been
well received by the IMAC fliers here in Arizona. Each year
the level of participation has gone up among the MAC fliers.
Later this summer, Brian Howard will be teaching a judging
seminar for the fliers down in Tucson. The main goal will be
to raise the level of knowledge, of both the IMAC fliers and
judges, on Aresti figures and judging criteria.
The full-scale
aerobatic community has been supportive of the MAC fliers in
Arizona by volunteering at their contests as judges. At the
2001 Cactus Classic held in February, Phoenix Aerobatic Club
members Len Rulason, Ben Peltzer, Jack Allenberg, and Mike
Steveson worked the judging line for the two-day event. John
Heigl and Jim Dornberger were the contest directors for the
event. The Cactus Classic was very well attended, with 45
contestants competing. It offered the judges a great tuneup
before the IAC contests in February and March.
In April, the
teamwork continued at the MAC contest at the Tucson Radio
Control Club. Brian Howard and Jim Dornberger volunteered as
judges. I volunteered as an assistant judge/scribe. AC
Advanced competitor Len Rulason competed in his first IMAC
contest in the Sportsman category, earning a second-place
finish. John Heigl competed in the Unlimited category.
The contest also
offered our two groups an opportunity to talk and outline some
plans for the upcoming Tucson Aerobatic IMAC Championship this
October in Avra Valley. We met with Dave Johnson of Desert
Aircraft and Mike Marcellin, contest director for the Tucson
Aerobatic MAC Championship. They have asked for our help in
putting together a premier IMAC event in Tucson.
Brian Howard and I
have volunteered to coordinate the judging and scoring
activities for the contest. Brian will start oft the
activities with the judging seminar in August. We will both be
actively seeking commitments from the IAC judges in our area
to judge the three-day event to be held October 19-21. It
promises to be a great event, with all categories flying and
many of the top IMAC and Tournament of Champions Unlimited
pilots attending.
The latest event was
held on May 20. The Southern Arizona Aerobatic Club hosted the
local EM membership and the Tucson-area IMAC fliers at Avra
Valley airport for a picnic. It was a nice afternoon for all
of our groups to share some great food and camaraderie.
John Heigl
demonstrated the IMAC Unlimited sequence and some 4-Minute
Freestyle flying for the IAC folks. John demonstrated how
realistically the IMAC scale aircraft fly a sequence. He also
showed us some of the things AC competitors can only dream
about doing with their airplanes—some hover and super slow
flight maneuvers.
Maryilln Holland
pulled names from a hat and two folks, Ann Tuttobene and Terry
Langen, went with Brain Howard fir an aerobatic ride in
Brian's Extra 300. Both returned with some of the biggest
smiles anyone has ever seen.
IAC and IMAC share
many common goals. At the local level here in Arizona, we look
forward to the continued growth of our partnership. Working
together to help promote both of our activities is a win-win
for both IAC and IMAC.
Judging the (not
so) Little Guys
Brian Howard IAC 18141
If you have never
seen an International Miniature Aerobatic Club (IMAC) contest,
you probably envision judging a radio-controlled model
airplane as being only slightly more difficult than scoring
the flight of an angry little bee. Very wrong! These models
are built to a scale ranging from 20 percent to 40 percent of
full size, with the categories above Basic mostly populated by
aircraft in the 35 percent to 40 percent range. A 40 percent
scale model equates to an airplane with a 10-foot wingspan, or
about half the size of a Pills S-i. More condor than bee!
Combine that large
aircraft size with the fact that the flying takes place much
closer to the judge and lower than full-scale aircaft, and the
effective, or visual, size of the model is very similar to
judging full-scale aircraft. Even the visual appearance you
are used to is preserved because IMAC members fly scale models
of actual aerobatic aircraft: mainly, Extra 300s/330s, Edge
540s, and CAP 232s. Other factions of the modeling world fly
smaller airplanes specifically designed for aerobatics, but
they are not representative of any "real" (i.e.,
full-scale) airplanes. Contests are run with those aircraft as
well, but their rules diverge considerably from the AC. And I
am only addressing the MAC scale contests here.
I recently had the
pleasure of judging another scale aerobatics contest and came
away more convinced than ever that IAC judges would do
themselves, the IAC, and IMAC a big favor by seeking out and
participating in MAC contests. More on the benefits of judging
a "not-so-miniature" contest later. First, let’s
take a look at what IMAC judging is all about and perhaps
dispel a couple more misconceptions you may have.
IMAC contests follow
most AC grading criteria, although there are both general and
even contest-to-contest differences. A 30-minute briefing with
a knowledgeable IMAC person is all it takes to learn where the
IAC and IMAC criteria differ. Your first bit of culture shock
when preparing to judge a scale contest is to learn that there
will be two judges’ lines and two airplanes in the box at
the same time. Each of the judges’ lines is only watching
one of the airplanes, of course. This is a timesaver I don’t
see the local FSDOs approving any time soon for IAC contests!
IMAC has the same
issues with getting volunteers to help at contests that we do
in AC. For example, even though the last contest I judged had
27 competitors, we could only muster the judges and scribes
(recorders) to form two judging teams for each line (eight
people total). No assistant judges, no chief judges, no chief
judge assistants, no panel flippers, and no runners, though
not every contest is necessarily like this. For example, the
Tournament of Champions invitational held in Las Vegas last
year had all those people except the panel flipper (because
there are no panels!).
IMAC contests take
place at "Scale" airports, which vary from basic to
deluxe. Usually there is a paved runway a couple of hundred
feet long and a ramp area along with support structures like
ramadas to shade the pilots and their entourages when they
aren’t flying. As the contest begins, the first pilot hands
the judges his score sheets and takes his place in a
rectangular area painted on the ramp quite close to the
judges. First thing 1 do at this point is note the paint
scheme of the pilot’s aircraft in case I lose track of which
of the two airplanes in the box is "mine" during the
flight. Following takeoff, the sequence begins with very
little fanfare. At most, one straight-and-level
"trim" pass through the box. If only IAC pilots
could start their sequences as quickly! Be ready to change
flimsies though, because each pilot chooses in which direction
to fly the sequence and announces that choice to the judges
before entering the box for the first figure.
There are four
categories (no Intermediate) in MAC, and competitors fly only
Knowns and Unknowns, no Free programs (except the Unlimited
4-Minute Free). Basic pilots fly only the Knowns. If there’s
enough time, each pilot flies a total of six Known flights
(all the same) and one Unknown flight. Seven flights— wouldn’t
you like to get seven flights at your next IAC contest?
Speaking of time, to minimize it, for each turn in the box the
pilot flies the sequence twice, one immediately following the
other. You will also notice that each pilot has a
"caller" who stands immediately behind the pilot and
does what an IAC assistant iudge dies: Calls each figure
before it's flown. With both hands on the radio-control box
and both eyes fixed on the aircraft, you can see the
logistical problems if the pilot had to deal with a sequence
card as well. Many of the MAC participants don’t read Aresti
(something I hope to change, at least in Arizona), so the
sequences are always published with both the Aresti symbology
and a word description of each figure. Fortunately, judges get
the normal Aresti flimsies to use. This is particularly
important if there aren’t any assistant judges helping out.
Comparing the two methods of describing the figures
(symbolic and verbal) really gives you an appreciation for how
efficient the Aresti symbols are at conveying a lot of
information very quickly.
Even during the
initial takeoff and positioning, the speed of the model
airplanes may surprise you. They fly much slower than you
would expect. Because these airplanes have tremendous
thrust-to-weight ratios (2- or 3-to-i), they relatively
low airspeeds and simply add power as necessary to pull
through a figure. Further debunking the "angry bee"
myth is roll rate. These scale models are capable of
tremendously high roll rates, but because of some carry-over
habits from another form of model competition called pattern
flying," the pilots tend to roll much slower than
full-scale competitors do. Judging Unlimited flights, for
example, is actually much easier in IMAC because of these slow
roll rates.
After the trim pass
has been flown, it’s time to start handing out the grades.
The most glaring change for an IAC judge is that everything is
wind corrected. That is, you always grade flight path, never
attitude. Vertical lines, 45-degree lines, turns, rolling
circles, and even flying between figures are all wind
corrected. When judging a vertical line, you can’t deduct
for positive or negative, wing low, and so on because it could
all be wind correction. Just like IAC 45-degree lines, you
have to ignore the airplane and judge only the
"verticalness" of the flight path. I don’t have a
problem with judging most of the wind correction differences,
but someday I’d like to convince "the powers that
be" to remove wind correction from vertical lines in MAC
competition. On a windy day, the verticals can really be ugly.
Picture a hammerhead with a strong cross-box wind from the
airplane’s left. Going up the line, the left wing will be
low to keep the line straight (a vertical crab). At the top,
the airplane pivots as you would expect in a hammerhead, but
much less than 180 degrees because now the right wing must be
held high (crabbing again) on the downline to wind correct.
Like I said: ugly. However, rules are rules, and as
experienced judges we judge to the criteria at hand, so you
try to ignore all that and concentrate on the flight path.
The biggest problem I
have is recalibrating my cranial calculator to deduct one
point for every 10 degrees of geometric error. Once you start
thinking in terms of half a point everywhere you used to
deduct one point, you’ll be there. All the other grading
criteria are identical to IAC. Snap rolls are a special
challenge because with the smaller (than full-size) airplanes,
it’s harder to see the nose displace prior to the auto
rotation. The "scaleness" of the model airplanes
also cause difficulties properly executing spins and
tailslides, but that is the pilot’s problem, not yours. You
judge to the criteria. Period. Actually, when watching you’re
watching an RC model. There are no high or low calls to judge
either. Hitting the ground has its own special penalty and
normally zeros all maneuvers after that point!
Following the final
figure of the first sequence in the flight, the pilot will ask
the judges if they are ready and then the pilot will
immediately reposition his model and re-enter the box for the
second sequence of that flight. When the second sequence is
complete and the airplane is back on the ground, the pilot
picks up the score sheets (hence no need for a runner) from
the scribes, and you are ready to repeat the process with the
next competitor. Zeros stand as scores, by the way, so there
are no judges’ conferences to slow the contest.
I started this
article by saying that I believed it would benefit IAC judges
to seek out and participate in IMAC contests. Why? Although
many of us are crazy enough to travel all over the country and
judge several AC contests each year, many others judge only
one or two contests a year. Sometimes not even that. Add the
regional IMAC contests to your judging calendar, and now you
have an excellent way of tuning your eyes before the first AC
contest and staying ‘tuned" between contests. For
example, at the last
IMAC regional I judged, in two days I scored 117 flights. That’s
a pretty good warm-up exercise before I judge my first
full-scale contest of the year.
If you are looking to
gain experience in the upper categories, judging IMAC Advanced
or Unlimited will be excellent training because of the slower
pace. Remember, too, that IMAC fliers don’t need the level
of good weather IAC does, and they can complete contests on
days when we full-scale people can only sit and watch the
clouds go by. I also mentioned benefits to the IAC and IMAC
organizations. Neither group can run contests without
volunteers. Lots of volunteers. Besides the obvious
camaraderie shared by the two groups (the only difference is
the size of the toys), if IAC people (not just judges!)
volunteer for IMAC events, you will be helping them immensely,
and the likelihood is that IMAC people will return the favor
by showing up to help out at your IAC contest.
Here is an
opportunity to enjoy aerobatics more frequently or when you
otherwise might not see any; improve your judging skills;
"tune up" your eyes before, during, and after the
IAC season; help a like-minded group of people put on a
successful contest; and enlist their help with your contest in
return. Sounds like the way to fly to me!
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