Sukhoi SU-31 was designed in Russia by the Sukhoi Design Bureau.
While Sukhoi is probably better known in aviation circles for
their military fighter planes, they also produce a line of high
performance aerobatic aircraft that includes the SU-26, SU-29,
and SU-31. While outwardly similar to the SU-26, the SU-31
replaces the tubular steel construction with an all composite
airframe and an available 400hp engine that swings a 100"
composite 3 blade prop.
So capable are the Sukhoi aerobatic aircraft that during the FAI
Aerobatic World Championships in 2007 that took place in Spain,
the SU-31 was flown to first place in two of the three
categories (men's and overall) and took 4 of the top 9 spots.
It may also
be interesting to note that the SU-26 took 3 more of those spots,
including the women's championship.
So what does all that mean to us? The Great Planes
ElectriFly SU-31 Sukhoi is a small model that has big shoes to
fill. Read on and we will see how it compares to it's full
ElectriFly SU-31 Sukhoi EP ARF Price: $109.98 Wing Span: 41" (1040mm) Flying Weight as tested: 2 lbs 0
oz (907g) Propeller Used: APC 10x7e Motor Used: RimFire 35-30-1250 Battery used: ElectriFly Power
Series 20C 2100mAh
Speed Controller Used: ElectriFly Silver
Series 35Amp Radio equipment: Futaba 9C with FAAST
module, R617FS FAAST reciever, S3154 digital
After inspecting the contents of the box, the first order of
business is always to examine the instruction manual.
Great Planes aircraft usually have excellent instructions and
the manual that came with the SU-31 ARF is no exception.
Spanning 28 pages, it includes a full inventory, precise
building directions, clear photographs, and even a section on
doing some advanced aerobatic maneuvers.
put the Sukhoi together over the span of three evenings, keeping
in mind that a review model needs to be photographed and
documented along the way. If you have everything ready to
go when you start, the average modeler with a few airplanes
under his or her belt could easily assemble the SU-31 in two
evenings or a rainy day.
I'll be using ZAP adhesives throughout this project as I have
had excellent results with them in the past. As with the
use of any chemicals, ensure you have adequate ventilation while
Wings ready for servos
Futaba's TINY digital servos
unpacked the kit a few things stood out at me. The covering
job was excellent and the airplane is covered in real Top Flight
MonoKote. After making sure the parts in the kit matched the
inventory I heated up the sealing iron and put a fresh blade in my
hobby knife. This is one of those areas that reading the
manual will let you consolidate a little bit of work. It will
also save you time waiting for your covering tools to heat up each
time if you do them all at once.
your hobby knife and a sealing iron, cut out and seal the edges of
the following areas.
Wings: Aileron servo bays and aileron control horn slots (watch you
don't do lightening holes by accident!)
Fuselage: Wing tube hole, wing mounting hook area, aileron servo lead
holes, wing anti rotation pin holes, horizontal and vertical stabilizer
slots, elevator and rudder servo bays (again, watch the lightening
holes), and the landing gear slots.
surfaces: Rudder control horn slot, and the elevator control horn
all of the holes were cut and sealed I went ahead and gently used my
my heat gun to shrink down any areas of loose covering. A poor
covering job will look shabby fairly quickly in the Florida sun but
the Sukhoi didn't need much work with the heat gun and iron to get
things tight. I would rate the covering job above average in
workmanship and outstanding in looks.
Aileron servo installation
Wings held in with rubber bands.
Wings are done, time to move on to the tail.
ailerons come pre-hinged so there's not much work to do here.
Several trees of plastic parts are provided with the Sukhoi that
appear to be generic and contain parts for several kits so don't
be alarmed at the quantity of left over parts at the end of the
Locate all of the plastic parts you will need for the two
pushrods and control horns. Install the servos in the wing
and fish the wires through to the center. You can either
glue the servos into the wing or use small self tapping screws.
I used small screws so I marked the holes and then moved the
servos off to the side while I threaded the hole and hardened it
with thin CA.
would go ahead and start setting up your transmitter and
receiver at this point. Hook up the ailerons using a Y
harness or using transmitter mixing and make sure the servos are
centered. Locate the appropriate control arm provided with
the kit for the servos you are using. If you are using
servos that the provided servo arms do not fit perfectly on the
output shaft, obtain the correct servo arms from your servo
manufacturer. I am using Futaba micro digital servos,
so it was no surprise that the provided arms fit perfectly.
When you get the servos secure, build the pushrods and install
the control horn. Note that you have to trim the control
horn, if you skip this step it will pop out of the top of the
aileron. Trim the ends of the pushrods and the wings are
ready for the installation step.
Rough up about half of the anti-rotation pin with 80 grit sand
paper and glue it into the wing root rib using either medium CA
or epoxy. Install the very nice carbon fiber wing tube and
slide the wings into the fuselage sides. The carbon wing
tube was a perfect fit and didn't need any sanding or tape to
get things to fit together nicely. The wings are held in
place by two large rubber bands that pull them together by
attaching to hooks that are pre-installed in the wing root.
I was a little skeptical of this arrangement but as of this
writing the plane has been flown for three weekends without any
problems. I'll keep a close eye on these and replace them
Horizontal stab installation
Elevator with pins to ensure CA hinges are centered
Notice the large control surfaces, this should be fun
secret to good flying ARF planes is to make sure to assemble
them straight. With that in mind, pay careful attention to
the steps outlined in the manual to make sure the wing and
stabilizer alignment are correct. Test fit the elevator
joiner rod and make sure everything is straight before you glue
anything. Rough up the ends of the elevator joiner for
maximum glue adhesion and coat the center section with petroleum
jelly or WD-40 so you don't get any inadvertent adhesion to the
stabilizer. The wing and stabilizer alignment on my kit
was right on and it was a good tight fit so I used thin ZAP CA
to secure it in to place.
The hinges are small so be sure to center them using pins.
This will ensure you get a good grip on both sides of the hinge.
You can get a lot of control throw and do some pretty wild stuff
with this plane so make sure the hinges are glued properly.
The rudder is pre-hinged to the vertical stabilizer but you
still need to install a hinge between the rudder and the
fuselage. Be sure to center and pin this hinge as well.
I dry fit the rudder and made sure it was straight and used thin
CA to secure it and the lower hinge into place.
all the glue has dried it's time to install the servos.
Again, you want to make sure the servos are centered and the
servo arms fit the servos properly. I've seen servo arms
slip a spline or two in flight, the results are either humorous
or scary (depending on if you own the plane in question).
Mount the servos the same way you mounted your aileron servos by
either gluing them in place or using small wood screws.
Locate all of the plastic parts you will need for the push rods
and install the pushrods and control horns. I also made
sure I glued the control horn keeper to the control horn with
thin CA and then trimmed it flush. Once you have all
the servos and control surfaces centered go ahead and trim off
the ends of the pushrods. I used a high speed rotary tool
with a cutting wheel. If you wrap the rods with Scotch
tape it will make a nice clean cut with no splintering. I
put a SMALL drop of thin CA on the end of each rod when I was
Ready for servos
Landing gear parts, note the thread lock, be sure to use
Completed landing gear, ready to install in fuselage
can build the landing gear then insert them into the fuselage.
However if you need to be careful to note that the struts only
mount one way and after carefully making sure I had everything
right I proceeded to build them backwards. If you want to
do it once just mount the struts first, then assemble the wheels
and spats. Make sure you use thread locker on the nuts and
let it cure ensuring that the wheels rotate freely but don't
wobble. The landing gear installation is solid and you can
remove the struts fairly easily if you happen to bend one or
rear wheel on the full scale airplane is replaced by a simple
tail skid on the model. The skid is split and you glue a
washer into the skid. It's a great theory and works fine
in the grass but after the first day out on a paved runway my
Sukhoi was missing both the washer and about half the skid.
I glued a small carbon rod on the bottom of the skid and it's
been fine since then.
It's time to build the motor box and get the business end
finished. ElectriFly has provided a clever, laser cut,
interlocking firewall. If you use the recommended power
system, the hard part is already done for you. If not
there are some options on mounting the firewall to accomodate
other motors but you will likely have to drill your own holes.
When installing the blind nuts, rather than simply pressing them
into the firewall, get them started by hand but don't press them
all the way in. Use the mounting bolts to pull them down
tight, this will ensure they are straight. I installed
mine with medium ZAP CA. You can do this one of two ways.
You can coat the bolts with WD-40 so you if you get any glue on
them they don't get glued to the firewall or blind nut and let
the medium CA cure. This will entail cleaning the bolts
later so you can thread lock them in place. The other
option, and what I did, was to pull the nuts tight and remove
the bolt immediately before the medium CA set.
Test fit and thread lock
Tail skid and washer
Laser cut firewall box
Completed motor box
RimFire electric motor
fit everything to make sure you have all the pieces in the right
place. When you're satisfied, mix up some 30 minute epoxy
and assemble the motor box. I wrapped blue painters tape
around the box and then glued the motor box to the fuselage and
set the whole thing aside to dry.
While I was waiting on the glue to dry I installed the magnets
in the cowl ring, battery hatch, and firewall. When
installing the magnets, make sure to get the polarity correct.
There's a simple way to do this. Separate the magnets into
pairs that are stuck together. Mark the exposed sides with
a felt tip marker. Install the magnets so that neither
mark is visible and the polarity of each pair will be correct.
I used medium CA to install all of the magnets. Also, when
installing the magnets and backing plates on the cowl ring, be
careful that you don't cover up the lower two holes, they are
were the dowel pins slide into and hold the battery compartment
hatch in place.
the glue on the motor box is dry you can install the motor and
speed controller. The location in the manual for the speed doesn't quite
work out when you try to install the cowl ring so move it
forward about half an inch or so. I mounted the receiver
on the bulkhead under the cockpit so I had to run a short
extension on the speed controller line going to the receiver.
hatch battery hatch is located on the bottom of the plane right
behind the cowling. It provides very easy battery access
and a good bit of room to move the battery back and forth to
make CG adjustments. The last plane I assembled in this
size range required removing the wing bolts and wing to get to
the battery; this is a much better arrangement.
Gluing the cowl ring to the engine cowling was the only step
that gave me any trouble while building the Sukhoi. Of
course, now that I know how to do it, doing it again would be a
snap. Tack gluing the cowl to the cowl ring like shown in
the manual only made me get glue all over the place.
Install the spinner back plate, install the cowl ring on to the
firewall, then slip the cowl in place. Using the spinner
back plate as a guide, fit the cowl to the cowl ring. I
used a Sharpie marker and marked the cowl on the top and bottom,
then remove both the cowl and cowl ring from the plane.
With the cowl off of the plane it's easy to glue it to the cowl
using CA and kicker to make a nice fillet.
Battery hatch and magnets
Cowl ring magnet installation
Motor and esc mounted
the cowl mounting complete there's only a few quick steps left
before we head to the field. The Sukhoi decal sheet has an
instrument panel decal which I cut out and applied to the
cockpit. The canopy I attached using strips of clear
packing tape. You could also glue it on with RC-56 canopy
glue but mine has held up fine with the tape and its almost
impossible to see.
business end then received an APC 10x7E composite propeller.
I ran the motor up in my shop and it had plenty of power to fly
right out of my hand so flight testing should be fun. I'll
be using the Electri-Fly 2100mah 20C LiPo and this combination
pulled 384 watts and about 33 amps on the bench. The
plane came in at two pounds even with this battery and I can't
see sacrificing flight time or performance with a smaller
battery to save weight.
set the control throws exactly as shown in the manual using my
9C with a 3 position switch. The combination of the
3154 digital servos, along with the FAAST module in my 9C gave
instantaneous control response. The servos may be small
but they are very fast and precise.
normally cut my own vinyl markings but the decals that came with
the SU-31 were very attractive so I went ahead and applied
several to the airplane. The only thing left now is to see
what she's got in the air.
Cat not included.
Completed cowl installation
APC 10x7E propeller
Heli battery from previous review worked well
Electri-Fly 2100mah 20C Lithium battery
firmly believe that the most difficult part of any review is
getting a weekend, good weather, and a pilot or camera operator,
to come together at the same time. Even though I didn't
have either a test pilot or cameraman handy I was very excited
to fly the Sukhoi so I went ahead and did a few test flights
when weekend and good weather intersected.
On low rates, with the CG in the center of its range, the Sukhoi
is very docile. I don't mean to imply that it's a trainer,
the Sukhoi is a high performance aircraft with large control
surfaces and a high power to weight ratio. As such it's
intended for pilots with some experience flying tail dragger
style airplanes. On low rates however, it goes where you
point it and doesn't have any alarming habits. It was
obvious the instructions were written by someone who has
actually flown the plane so start at the recommended throws.
Using mid rates the Sukhoi is capable of an impressive array of
aerobatics. I would say I did about 70 percent of my
overall flying with the Sukhoi in mid rates. Snaps were
crisp both inside and outside and stopped immediately when the
sticks were centered. Spins were tight and easily entered
but wouldn't flatten out. I moved the battery back in
increments until it was pushed back against the wing tube.
Now we are talking!
With the CG as far back as I could get it with the battery, and
switch set for high rates, it was time to get it on. This
plane does the best looking blender of any plane I've ever
flown. Period. When crossing the ailerons in a spin the
spin would flatten out at just past neutral and with a little
power the Sukhoi would come down like a leaf in a fall breeze.
The Sukhoi will hover in high rates but lacks the power with
this prop for an authoritative punch out. I may give a few
more propellers a try. Harriers and rolling harriers are
easy to accomplish but look better in mid rate than they do in
The SU-31 Sukhoi ARF from ElectriFly
has proven to be a very capable aircraft. Its a very light
aircraft that sports an attractive covering job in real Monokote.
The control surfaces are generous and the optional S3154 servos
provide plenty of zip. The light wing loading makes
advanced aerobatics impressive and landings easy. The
carbon wing tube and rubber band and hooks stood up to some very
violent flying without any issues.
Review models always seem to
get a lot of attention at the flying field and our clubs recent
electric fly in provided plenty of onlookers when I took out the
Sukhoi. I brought several batteries and let a variety of
people have a turn flying the Sukhoi. I could sum up the
impressions by the number of offers I had to buy the plane that
day. No thanks, I'm keeping mine.
ElectriFly and Futaba
exclusively by: Great Planes Model Distributers
The comments, observations and conclusions made in this review are solely with respect to the particular item the editor reviewed and may not apply generally to similar products by the manufacturer. We cannot be responsible for any manufacturer defects in workmanship or other deficiencies in products like the one featured in the review.