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Rutan 27 / 32 VariViggen

rut-v-v


In 1968 Rutan began the design of his Model 27, which first flew on 27 February 1972 and then became the VariViggen canard lightplane for the homebuilder market. The VariViggen is a tandem two- or four-seat lightplane of canard layout with a cropped delta main wing, and the 150 hp (112 kW) of its Avco Lycoming 0-320-A2A flat-four piston engine provides a sea level maximum speed of 163 mph (262 km/h) at a maximum take-off weight of 1700 lb (771 kg), together with a range of 400 miles (644 km) on 35 US gal (132 litres) of fuel. The VariViggen is an application of the low-speed aerodynamics of the Viggen canard arrangement, with various changes, to a general aviation purpose: a tandem two-seat pusher with a 150-hp Lycoming engine and a fixed-pitch wood propeller. It is an old project; Rutan started developing the configuration when he was still at Cal Poly. He tested models on a "car-top wind tunnel" of his own invention, flew Styrofoam gliders and an 18-percent scale, radio-controlled model to investigate his design's flying qualities and finally completed the full-size prototype at Lancaster, California. It flew almost exactly as his scale tests had predicted it would.

Optimized for low-speed maneuverability, it is not a particularly fast airplane - 130 knots cruise on 113 hp - and its climb performance is only just adequate, because its low aspect-ratio lifting surfaces produce a lot of drag at high lift coefficients. What makes the VariViggen unique is its low-speed handling, in which it has little in common with conventional airplanes.

On the face of it, it appears that what makes the VariViggen a slow climber and mediocre cruiser is simply its short span. The canard, which is only eight feet across, carries a quarter of the airplane's weight while the main wing, carrying the rest, has a span of 19 feet. The aspect ratios of the fore- and main-planes are 3.5 and three, respectively. The wing loading is 14.3 lb/sq.ft. and the power loading is 11.31 lb/hp. The weighted average of spans (weighted in proportion to surface loading) is only 16.25 ft. giving a linear span loading of more than 100 lb/ft.

The VariViggen is not stressed for aerobatics in the RA's limited definition of the term. The limit load factor is five. The airplane will roll nicely, Rutan says, but is too draggy for high-G maneuvers like loops and is characteristically incapable of snapping or spinning.

Its cruising range is short: 326 nm, with no reserve on internal tankage. The cockpit is reasonably comforta-ble (25 inches wide and amply long and high) and its noise level is moderate, at least partly thanks to the wooden structure and the placement of the engine and prop at the rear. There is a large baggage compartment be-hind the back seat with a 180-pound capacity.

Approach and landing are quite conventional, until the time comes to flare; then the airplane seems to give itself over completely to ground effect and to want to go on gliding forever, unless you simply drive it down onto the runway. Rutan is able to achieve remarkable accuracy in his landings, and he wins all the spot landing contests he enters, because he can maneuver widely on final approach in order to position himself and can also land at any of a variety of speeds. The brakes are very powerful; Rutan gives the landing roll as 400 feet.

The VariViggen's low-speed maneuverability is of limited usefulness in everyday transportation flying-as is obvious from the fact that most airplanes don't have it, and one hardly even notices the lack. A gusty crosswind during landing is about the only normal circumstance in which low-speed maneuverability comes in handy; here the Vari-Viggen's high roll rate at low speed and its ability to turn and sidestep sharply give it the advantage over a conventional airplane.

The Model 27 version of the VariViggen proved incapable of stalling or spinning in the conventional sense of the words, though the stall was restored in the Model 32 version with revised outer wing panels (of urethane foam/unidirectional glassfibre rather than aluminium alloy construction) for higher performance.

The VariEze had well over 4000 sets of plans sold and in various stages of construction; some 400 are already flying in 1980.

 

Variants:
Microstar Variviggen


Gross Wt. 1700 lb
Empty Wt. 950 lb
Fuel capacity 25 USG
Wingspan 19’
Length 19’
Engine 150-hp Lycoming
Top speed 160 mph
Cruise 150 mph @ 7000 ft
Stall. 53 mph
Climb rate 800 fpm
Takeoff run 800 ft
Landing roll 500 ft
Range 400 sm

 

 


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