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Rans S-4 Coyote I

Rans is one of the American companies that, right from its beginning, has enjoyed a very rapid growth, especially in terms of market share. This is owed to the ability founder Randy Schlitter (hence the acronym RanS) has always had in understanding what the market needs and in providing products which would satisfy those needs more than adequately. One of Randy's great ideas has been to offer kit airplanes which need hardly any covering or painting work (and any homebuilder knows what that means). The quality of the kits made up for the rest.
The Rans Coyote I, S-4, was one of the first aircraft conceived by Schlitter's fervid and ingenious mind in 1983. At the time it was powered by a KFM, soon to be replaced by a Rotax 277. It is a classic single-seat tube and fabric aircraft with a double-strut high wing, front engine, conventional tail and tail-dragger configuration (there is a trigear version called S-5).

All the structural parts are in 6061 anodized aluminum alloy, with the cabane struts, the engine mount and part of the landing gear in 4130 steel. The dacron covering is prefabricated and just needs to be slipped on. The wings are made up of two tubular spars (one forms the leading edge and the other the trailing edge) joined by other tubes of smaller diameter. The ribs are replaced by about ten simple curved battens which are inserted in suitable sleeves obtained in the dacron covering, giving the wing its proper shape. Indeed, looking inside the wing you can see much more open space than in a traditional wing. It all combines to produce a very light and easy to build structure. The real backbone of the entire aircraft is the keel, consisting of a large diameter tube located on the upper portion of the fuselage, in between the wings. The keel truly holds everything together: the wings, the cabane, the cockpit, the engine mount and landing gear as well as the remaining portion of the fuselage and the tail planes. The front gear is equipped with classic Piper Cub style bungees as shock absorbers.
The cockpit is quite roomy, yet it is not quite suitable for tall pilots who will find themselves touching their heads on the keel tube. The seat is adjustable front and back as well as in height, while all controls are within easy reach and in a natural position. The stick has a typical curved shape and controls the elevator by means of two rigid tubes connected to the ailerons using two bowden cables. Flaps are operated through a cable and pulley system, just like the rudder. The flap lever, which is located on the left beside the seat, is the only control that is somewhat difficult to activate as it forces the pilot to bring his or her arm to the back and very close to the door.
Actually, as far as doors are concerned, the Coyote I has none in its standard version. They are an optional which is quite recommended for colder climates. The fact that they can be removed in a few minutes allowing one to fly almost open air is, in my opinion, one of the most attractive features of this ultralight. In this configuration, visibility is exceptional; not to the front, of course, but this is something most pilots who do not fly trikes are used to. Another peculiar characteristic of the S-4 is the possibility to remove, without any tool, the front canopy and side windows, which can be quite simply forced in place through a clever system of snap joints. The version of the Coyote that I tested (built in 1992) originally had a Rotax 447 as standard engine, later to be replaced by the more powerful 503.
The Rotax 503 has become a standard engine on the '98 model of the S-4. The engine mount and the cowlings have been slightly modified as well and allow for the engine to be mounted in an "upright" position. This avoids the typical inconveniences of engines mounted upside down: difficulties in starting up and plugs clogging up easily. No other major modifications have been made, with the exception of a few minor details. For example, the new trimming system, now a standard feature, has been obtained with the typical tab attached to the elevator, while on the model I tested it consisted of a simple system for regulating the tension in a bungee chord attached to the control stick.
The fuel tank is located behind the seat inside the fuselage, and holds 18 litres. One can add an additional 20-litre tank between the two wings, on top of the keel. In this manner, maximum flight duration is increased to approximately 2.5 hours, assuming an hourly fuel consumption of 14 litres.
. Pre-flight checks are quite straightforward, thanks to the tube and fabric construction. To check the engine, one needs to undo about fifteen screws and remove the top cowling. Starting the engine (by hand) is not as simple as it may seem. One needs to be careful with primer and throttle and, even so, it is rather easy to dirty-up spark plugs. The fact that the pilot has to pull the starter chord from within the cockpit complicates things even more. Once the engine is started, one begins to appreciate the good qualities of the Coyote, commencing with the great ease of handling on the ground. The Rans almost does 360's just by using the rudder pedals; if you then apply the (differential) brakes you can literally turn the aircraft about one of the front wheels.
Taxiing is simple even though the tail-dragger configuration requires one to perform the usual s-turns.
Take off requires just a few dozen metres. A notch of flaps, throttle, stick forward and the aircraft starts to jump upwards in its natural tendency to leave earth. The Rotax 503 provides plenty of power and a climb rate of 800-1000 fpm at a speed of 50 mph. It is absolutely necessary to fly with ear plugs or a headset due to the high noise level, especially with the doors on. Cruise speed varies between 55 and 65 mph. This depends on how many rpms one likes to fly at. Personally, I find it somewhat disturbing to fly at 5500 rpm with an engine that redlines at 6200. This measures up to about 90% of maximum rpms. Yet, even the Rans manual talks of an ideal cruise speed of 65 mph at a "comfortable" 5500 rpm. Indeed, at about 5000 rpm you get no more than 55 mph, and for a faster cruise (and higher fuel consumption!) one needs necessarily to push more rpm. Turns are entirely conventional. Adverse yaw is minimal and consequently little rudder is required. Among the manoeuvres that the manual indicates as suitable, we find: all types of stall, chandelles, falling leaf (with engine rpm below 4000), Cuban eight, spins (at low rpm and no flaps). During cruise one can feel the decreasing fuel load and as the tank gets progressively emptier one must work on the trim system to allow for a truly pleasant flight, in non-turbulent conditions. Controls are very homogeneous and all it takes is a little stick or rudder to bring the aircraft back to level and straight flight.
Stall without flaps is preceded by a fair amount of shaking, made even more obvious by the dacron covering. The Coyote finally lowers the nose at about 29-30 mph; it just takes a little forward stick to return to controlled flight. The approach is done at 50 mph, down to 45 on short final. A three-point landing will bring the aircraft to a complete stop in a few dozen metres and, as is routine on this type of aircraft, a lot of time is spent taxiing to the nearest parking spot!
In any case, leaving all raw performance figures behind (I am not a test pilot), I can say that flying this aircraft is truly a pleasant experience, thanks to its excellent visibility, precise controls and comfortable seat. When I bought this small airplane I flew it for about a half hour, doing a few touch-and-go's, and after careful pre-flight checks, I brought it home on a 5-hour flight, with two full hours flying over the Appenines. This just to tell you how familiar and secure the airplane feels. A feeling which is further confirmed by the S-4's good reputation.

Flavio Giacosa

Technical data
ModelCoyote I S-4
Wing spanmt 8,96
Wing surfacemq 11,80
Lenghtmt 5,20
Gross weightKg 266
Empty weightKg 142
Standard fuel tankLt. 18
Stall speedKm/h 56
Stall speed w. flapsKm/h 43
Cruise speed @ 5000 rpmKm/h 90
Max speedKm/h 152
EngineRotax 447-503
Fuel consumptionlt 14/h
Take-off rollmt 30
Landing rollmt 50
Price10.900 US$
ManufacturerRANS Co.
4600 Highway 183 Alternate
Hays, KS 67601 U.S.A.
tel. (913)625-6346 - fax: (913)625-2795
e-mail: rans@media-net.net
Website: www.rans.com

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