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Rans S-9 Chaos
The S-9 Chaos has been in
production since 1986. The Chaos is popular the world over in
aerobatic competitions and sport flying. A Chaos airframe is a
perfect match for the new breed of powerful two stroke engines. A
stock S-9 equipped with a Rotax 503 47hp engine is potent enough to
compete in sportsman class aerobatics. S-9's have been equipped with
up to 100 hp engines with spectacular results. With full inverted
capability, a Chaos can whip through an advanced routine leaving
little doubt about the plane and pilot's ability to finesse the
figures.
Aerobatics is the intent of the Chaos, but the well behaved plane
serves well for cross country or around the patch flights. Pilot
workload is minimal due to the light control pressures. As with all
RANS kits, the Chaos comes welded and pre-fabricated, reducing
assembly time and increasing precision.
specifications |
47 HP |
65 HP |
Wing Span |
22.0 ft |
22.0 ft |
Area |
91.5 sq ft. |
91.5 sq ft |
Mean Chord |
4 ft 2 in. |
4 ft 2 in |
Aspect |
5.3:1. |
5.3:1 |
Length |
15 ft 8 in |
15 ft 8 in |
Height |
4 ft 10 in |
4 ft 10 in |
Cockpit Width. |
26 in |
26 in |
Headroom |
38 in |
38 in |
Legroom |
45.5 in |
45.5 in |
Number of Seats |
1 |
1 |
Doors. |
1 |
1 |
Landing Gear* |
F/TD |
F/TD |
Baggage Volume. |
n/a |
n/a |
Baggage
Capacity |
n/a |
n/a |
Auxiliary
Baggage Volume |
n/a |
n/a |
Auxiliary
Baggage Capacity |
n/a |
n/a |
Fuel Capacity * |
9 or 18 gal US |
9 or 18 gal US |
|
|
|
power plant |
503 |
582 |
Engine |
Rotax 503 |
Rotax 582 |
Output |
47 hp |
65 hp |
Oil Capacity. |
n/a |
2.5 qts |
Coolant
Capacity |
n/a |
4.4 qts |
Propeller
Diameter |
68 in to 70 in |
68 in to 70 in |
Propeller Type |
Wood |
Wood |
Gear Reduction. |
1:2.58 |
1:2.58 |
Fuel G.P.H.
|
4.0 gal @ 85% |
5.75 gal @ 85% |
|
|
|
performance |
|
|
Take Off Roll |
250 ft |
200 ft |
Rate of Climb. |
800 fpm |
1000 fpm |
Service Ceiling |
13,500 ft |
15,000 ft |
Cruise. |
90 mph |
100 mph |
VNE. |
130 mph |
130 mph |
Stall Clean |
38 mph. |
41 mph |
Stall Flaps |
n/a |
n/a |
Roll Rate |
100°
/sec
|
100°
/sec |
Glide Ratio |
8:1 |
8:1 |
Landing Roll |
400 ft. |
400 ft |
Endurance |
2.25 hrs/4.5
hrs |
1.56 hrs/3.13
hrs |
Range** |
202.5 miles/405
miles |
156.5 miles/313
miles |
|
|
|
weights and loadings |
|
|
Gross Weight. |
670 lbs. |
710 lbs. |
Empty Weight. |
340 lbs. |
375 lbs. |
Useful Load. |
330 lbs. |
335 lbs. |
Wing Loading. |
7.32 lbs. |
7.76 lbs. |
Power Loading |
14.2 lbs. |
11.0 lbs. |
Limit Load
Factors |
+6-3 |
+6-3 |
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|
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*
F/TD = Fixed Taildragger |
**
Double the Range with a second optional wing tank |
flight report
The S-9 Chaos has been in production since May of 1987, and
has remained virtually unchanged since production began. Minor refinements
have been implemented to the fuel, control, and cooling systems. A new
cowl and landing gear changed the looks a tad a few years back, but for
the most part the plane has remained close to original form. It is simply
hard to solve the equation significantly better than the way the S-9 does.
Maybe with improvements in engines, some weight reduction, and control
system upgrades we could see a crisper S-9, even so the stock Chaos is
pretty well dialed in for the mission at hand. That mission is low cost,
exciting aerobatics. Lots of ultra light type planes claim Akro status but
none can do the figures with the agility and precision of the S-9. The
reason is the mid wing design allows amazing strength to weight. The
original S-9 weighs in at 280 lbs. with the Rotax 503. It seems incredible
to roll and loop a plane that light at speeds near 100 MPH.
Our latest demo plane weighed in at 430 pounds with 220 pounds of fuel and
pilot that comes out to a power to weight of 10 per horsepower with the
582. 10 to 1 is a decent ratio, bettering that makes it even more
exciting. The goal of anyone building an aerobatic plane should be to keep
the weight down, and making a lighter S-9, although a challenge could be
possible. Most of the ideas I have center around making the plane more
mission specific, for example, our new S-9 has two tanks for the
occasional cross country. Dropping one tank saves 8 pounds. It may be a
little spendy, but titanium landing gear might shave 4 to 5 pounds, and
lighter fabric and paint overall could kick out another 2 to 4. Close
study and diligent attention to detail could eventually decrease a typical
S-9 with a 582 down to fewer than 400 pounds empty. That would be almost a
˝ pound per horsepower less!
The first flight found me with a plane nearly in perfect rig. After a
20-minute flight confirming all was in the green and buttoned down, it was
time to test the aerobatic side. I could tell from the climb performance
(well above a 1000 FP) and the light handling that this was going to be
fun.
I did a couple of clearing turns, checked altitude and let it rip. From
level flight I rolled into a tight right aileron roll. Level again for a
brief moment, I repeated the right roll connecting it to three more,
holding a level line. The roll rate is impressive between 110 to 120
degrees per second.
Next I did a series of left roll, stop level and right roll, left or right
the roll seemed symmetrical. I did four, eight and sixteen point rolls
followed by 12 to 14 second slow rolls. All was purring along fine, the
S-9 was in its element, the engine never skipped a beat inverted or not.
Throttle response was smooth and power was at about 75%.
From level flight I pulled a loop, goosing the throttle to full power on
the up line, making a tight round loop that I let continue into several
more. I studied the altimeter noting the loop was less than 300 feet in
diameter. Several more loops later I had found great fun in giving it a
shot of power on the up line. It was a neat way to make a tight loop. It
reminded me of riding a powerful Sea-Doo, pumping the throttle when
ramping up a wave to get max airtime, only this was much drier and total
three-dimensional fun!
Ok the basic roll and loop come off without a hitch, it was time to rock
and roll, and that is what the S-9 does best. I pulled into a long
vertical line topping out in a hammerhead to the right, with a half roll
on the down line I entered a hammer to the left, just a little more rudder
on these would be nice.
The vertical line was at least 300 to 400 feet, and allowed a complete
vertical roll with barley enough to hammer out at the top. Takes a lot to
go straight up, but I was quite pleased with what 65 HP could do.
On the down line the S-9 has plenty of drag, so you are not easily busting
redline, so you have time to adjust the line or roll either way. Keeping
it pegged straight down requires a little stick and rudder, but small
moves here.
I performed some lomcevacks by taking it on a 45 up line then hard over to
the right with forward stick and punching left rudder. From the ground
these look slow motion, and may even be hard to recognize as a lomcevacks,
but they are a gas, since the Gs are low. In fact that is one of the
pleasures of doing Akro in a light energy plane the g-load are never more
than +4mostly under +3.5.
The optional Hooker harness goes a long way to feeling secure in the
plane. I noted no adverse body movement, making it very relaxing to
execute a figure knowing not matter the motion I was firmly behind the
controls.
Stalls came off with the traditional buffet with a straight-ahead drop. A
slight relaxing of the stick and you are flying again. Noting the
indicated airspeed at stall was 45MPH; I was looking forward to gentle
landings. At 800 AGL, I slowed to 70MPH for the pattern then on final kept
is nailed on 60MPH. Kissing the pavement at just above 50MPH, the landing
was something any experienced tailwheeler could do. This is a short quick
plane and paying attention on landing is required (as with any tailwheel
plane!). However to learn the S-9's traits takes only a few minutes, and
it is forgiving enough to allow some less than professional moves. A bonus
is the awesome crosswind capacity, 90 degrees at 20 kts is easily
demonstrated. Again it is simply getting to know the breed.
I have heard about pilots not being so enthused about the S-9's runway
manners. In most cases pilot skill not being a factor, the planes that
would not behave, the builders had made changes to the main gear or
tailwheel. On one occasion a builder simply did not have the tailwheel
steer springs tight enough.
In other cases it was not following the recommended procedure. We stress
to take off and land with the plane in the three-point position. This is
the trick to easy tailwheel operation in both the S-9 and S-10. It is hard
for experienced tailwheel pilots to follow this simple advice, but to
understand the design of the S-9 is to know why this advice works. The
static angle of the S-9 is 9 degrees; that was done on purpose. It placed
the gear far enough forward to prevent nose over, and it gave it short,
light, and strong gear. There is also very little prop clearance. At such
a shallow angle there is no need to get the tail up to rotate, the S-9
lifts off when it has flying speed, and does so in the same distance with
tail up or down. In fact the tail down take off comes out a little
shorter. That is the science behind it, now if we can just get the point
across to the veteran tailwheel pilot!
After a few touch and goes, it was time to call it a day. With just a few
minutes of sunlight left, I closed the hanger door thinking about the
shiny new plane left inside. How a humble little plane has the ability to
take a normal day in a pilot's life and turn it upside down literally, I
guess that is why it is called the Chaos!
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