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Rans S9 "Chaos"

The RANS S 9 "CHAOS" is a single-place ultralight monoplane with a strut braced mid-wing. It is built by the RANS Co. of Hays, Kansas, U.S.A., and is sold in kit form by the same company.
It's design characteristic, perhaps a very unique one in the ultralight field, is that the aircraft has been optimized for aerobatics, having an ultimate load factor of +9 and -6 G's.
It's structure is entirely metallic and surfaces are covered with heat-shrink dacron from STITS POLYFIBER.
Assembly time is estimated at around 500 hours, although it may vary from builder to builder.
The kit is one of the most complete I have ever seen, and contains clear and highly detailed instructions. The plane can be built rapidly and with no particular difficulties, as long as one remembers to read the instructions and suggestions before hand.
The fuselage, which is built out of chrome-molybdenum steel tubing like the tail surfaces, is shipped completely welded. The horizontal tail surfaces are made of welded steel tubing and are braced by four steel cables, without screw couplings, which are supplied already assembled and clamped.

The wing has a trapezoidal planform and is strongly tapered, in thickness as well. It is constructed with 4046 T6 aluminum tubing and must be completely assembled; its structure is very simple yet strong and light (a real engineering masterpiece). The ribs are in Avional aircraft tubing, and consist of two preformed halves to be joined with pop rivets; they can be built quite easily on two saw-horses with no need for a perfect work bench. The leading edge is reinforced on the top by an aluminum sheet glued and riveted to the structure; wing struts, in the latest version, consist of large section streamlined aluminum tubes.

The tail dragger landing gear simply consists of a pair of thick-wall steel tubes with a large cross-sectional area, and has no shock absorbers (Wittman style). The tail wheel is non castering and supported by a steel leaf spring. The aircraft can be powered by one of the ubiquitous two-cylinder, two-stroke Rotax engines, from the 503 (52 HP) to the 582 (65 HP), preferably the latter if you are going to do any aerobatics. With this in mind, the manufacturer offers a kit for inverted flight containing everything from the Mikuni pump carburetors to a five-point safety harness, as in the best aerobatic tradition, and fuel feed system with inverted pickup tubes.
The Chaos features a fully enclosed cockpit with a large lexan canopy. It is roomy enough for fairly large pilots; the seat is reclined quite a bit, but is still comfortable especially if you use a sailplane type parachute, which will support your spine.
Controls are traditional, with pedals connected to the rudder by two steel cables, and a control stick which is connected to the elevator through a rigid aluminum tube and to the ailerons by means of Bowden cables. The elevator trim is on the left, next to the throttle: it is of the wheel type and is connected via cable to the Flettner tab on the right half of the elevator; it is very efficient and may cause somewhat of a difficulty during the first flights.

FLYING CHARACTERISTICS

The plane is not too difficult to handle on the ground, as long as you have good experience with taildraggers. The independent drum brakes on the two main wheels are rather effective and are cable operated by pressing on two small pedals located on the inner side of each rudder pedal.
Takeoff is at around 60 mph after a run of approximately 100 metres (110 yards); we recommend a three-point takeoff the first few times. Reduce power slightly and you'll find yourself climbing away at 65-70 mph IAS and at a rate of 700 feet per minute (the initial rate of climb at full power can exceed 1500 fpm). Once you level off you can hold a cruising speed of about 85 mph at 5800 RPM (Rotax 582 and a very low pitch propeller); top speed is over 110 mph.

Controls are well coordinated in flight, with the elevator being somewhat more authoritative than the ailerons. The rudder is precise and very effective even at low speeds. As you bring the power back to minimum and hold the rate of climb indicator on zero, you will get a 1 G stall at about 40 mph IAS, preceded by slight buffeting, showing no abnormal behaviour.
Bring the stick back against your belly and the nose will drop noticeably below the horizon, at which point easing the stick forward will get the plane flying again with minimal loss of altitude. Stalls at over 1 G, instead, are quite sudden and sharp with a definite tendency to enter a spin, if you don't have the ball right in the centre (be careful pulling tight turns at low altitude!). This is not at all abnormal for any aerobatic machine; you just have to be a little careful.
The approach to the landing field is flown at 60 mph and the actual landing itself is made slightly difficult by the very poor forward visibility (visibility in the Chaos, in any flight condition, is not that great due to the wing being placed right about at the pilot's shoulders). Given that the nose must be kept well above the horizon, in order to keep flying at 60 mph, you won't see much of the runway. After a three-point landing, without any considerable ground effect, you can start the usual tip toe dance on the rudder pedals and stop the plane in about 150 metres (165 yards).

AEROBATIC FLIGHT

I must point out before hand that the Chaos' aerobatic capabilities are somewhat hampered by the limited available power and by its small total mass. Basically, the plane lacks the inertia that becomes most useful in those manoeuvres (especially vertical ones) where speed can be lost very rapidly; nonetheless, the aircraft behaves well and if you find yourself in a difficult situation and with sufficient height, all you need to do is cut the throttle and centre the stick .... your small Sukhoi will take care of the rest.
Here are the main classic aerobatic manoeuvres you can perform with your RANS, in complete safety:
LOOPS - this particular one requires a little extra speed; just don't expect to pull loops as wide as the air force jet aerobatic teams do.
TONNEAUX (ROLLS) - there are two ways of doing them: an easy way offering a great show (barrel roll), and a much more difficult one (straight roll). You friends will appreciate them both .......
FIESLER- a fairly easy manoeuvre, unless your planning to compete in the world championship.
INVERTED FLIGHT - Oh yes indeed! The Chaos can fly upside down too! It just remains to be seen whether YOU are willing to do it.
SPINS - it is best to enter them intentionally and with plenty of altitude. Don't you agree?

CONCLUSIONS

From the above description, I suppose one could discern that I am the lucky owner of an S9, built from a kit. I am very satisfied with the Chaos, although I must admit that its highly specialized design makes it hard to sell on the used market.
I don't believe the aircraft is suited for long trips, due to its short maximum range and the less than exciting view: you won't enjoy much of the scenery on your cross country flights. You must also consider that, after hardly half an hour being strapped to the seat without even being able to reach the instrument panel (sometimes I reset my G meter with the help of my feet), the flight becomes hardly enjoyable.
All of this means that you won't sell you Rans S9 easily. You might just have to be content with doing a little aerobatics from time to time. If you think that sucks....!

Sandro Brecciaroli

mod.	S9 CHAOS	Vne	170 mph	Address
wing design	mid wing	cruise speed	85 mph	RANS Co. 4600 Highway 183 Alternate Hays, KS 67601 U.S.A. tel. (913)625-6346 - fax: (913)625-2795
materials	metal	stall speed (flaps)	-
engine	Rotax 582	stall speed	40 mph
empty weight	lbs 420	rate of climb	1500 fpm
gross weight	lbs 883	takeoff roll	110 yards
height	60"	landing roll	170 yards
wing span	24'	plans	-
lenght	15'	Kit price	--
wing area	95 s.f.'	dealer	---