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The Kitfox STi is the STOL-optimised flagship variant of the Kitfox Series 7, a side-by-side two-seat, steel-tube, fabric-covered kit aircraft with folding wings, built by Kitfox Aircraft in the USA. Fitted with a high-lift wing and the powerful 141-horsepower Rotax 915 iS (or optionally a Titan X340), it is the manufacturer's most powerful and highest-performing model, designed for backcountry flying, short-field work and STOL competition. For the simulator pilot it represents the pinnacle of the modern kitbuilt bush-plane genre, offering strong power-to-weight, huge flaps-and-flaperons, and genuine off-airport capability.
The Kitfox STi is a variant within the Kitfox Series 7 line, a side-by-side two-seat, high-wing, tailwheel or tricycle-gear kit aircraft built around a precision-welded 4130 chromemoly steel fuselage with fabric covering. STi stands for 'STOL Inspired', and the designation marks it out as the STOL-focused, highest-performance model in the Kitfox range, sitting above the standard Super Sport on which it is based. Like all Series 7 Kitfoxes it features folding wings as standard, allowing the aircraft to be folded within about 15 minutes for storage or transport.
Kitfox was founded in 1984, and by the time of later reporting the company had delivered more than 7,000 kits into over 43 countries, with more than 3,500 of its aircraft registered and flown in the United States. The STi grew out of Kitfox's own development airframe, N81KA, a silver and green demonstrator built as a testbed for new wing and engine configurations rather than as company president John McBean's personal aircraft. That airframe was, at its heart, a standard Super Sport that was progressively modified with different wings and powerplants so the factory could explore the edges of the design's performance envelope. The new high-lift STOL wing that defines the STi was designed by McBean with greater span, greater chord and a customised, under-cambered airfoil, replacing the leading-edge slats of earlier wings with vortex generators; it was first offered as the S7 STi option about a year before it was flown with the Titan engine, and had previously flown on the same testbed with a standard wing and a Rotax engine. A key design goal was full backwards compatibility with existing Kitfox fuselages, so the new wing can be retrofitted to already-built aircraft without losing the folding-wing feature. Kitfox has continued to develop the STi as its flagship, and by the early 2020s it had become the company's most popular model, with the factory reporting sales of around 120 kits in a year across the range and six complete light sport aircraft built annually.
The STi shares the Series 7 fuselage: a precision-welded 4130 chromemoly steel structure for the fuselage, rudder, stabiliser and elevator, with flight controls built from 4130 chromemoly push-pull tubes and a stainless-steel cable-controlled rudder. The cockpit has a dual control stick with ball-bearing pivots and adjustable stops, a hydraulic toe-brake system, a locking flap deployment system, fibreglass bucket seats with formed storage areas, and four-point seat belts with shoulder harnesses. A removable full Lexan turtledeck, pre-formed acrylic windshield and full-length Lexan gull-wing doors that can be opened in flight are standard, and the convex Plexiglas gives a good view whether the doors are open or closed. Baggage capacity is 150 lb. Landing gear is convertible between tailwheel and tricycle configuration, using certified aluminium spring gear by Grove Aircraft with a Grove 600-6 wheel and brake system on a 1 1/4 inch axle, hydraulic brakes with a remote reservoir, and standard 600-6 aircraft tyres; the STi package adds a Cabane 'V' style gear with nitrogen-filled shocks. The tailwheel is steerable and the nosewheel is 90-degree full-castoring. Covering uses Stitts Poly Fiber, with 2.7 oz stamped certified fabric, finish tapes, cement and sealer. The defining feature of the STi is its high-lift STOL wing: longer span and greater chord than the standard wing, with a customised under-cambered airfoil, vortex generators on the upper leading edge in place of leading-edge slats, and flaperons that run nearly the full wingspan, combining flap and aileron function with limited flap deflection to prevent the surface stalling when deflected down for roll input. The wing was originally longer before Kitfox shortened it by one rib bay after determining the bending moments near the tips were excessive. Engine options include the Rotax 915 iS, rated at 141 horsepower, which AOPA describes as the STi's most powerful and highest-performing configuration, and the Titan X340, a carbureted engine putting out 180 hp with a full carbon plenum for a clean cowling installation; Kitfox has noted that cooling and prop pitch optimisation for the Titan option were still being refined. The tight cowl and wide-chord, three-blade propeller associated with the Rotax 915 iS installation give the aircraft a look likened to a turboprop.
Factory-quoted performance figures for the Kitfox Series 7 (calculated using factory demonstration aircraft with professional pilots at standard sea-level conditions) show a rate of climb of 1000 fpm, a cruise speed of 130 mph TAS, a full-flap stall speed of 46 mph, a takeoff ground roll of 330 feet and a landing ground roll of 350 feet, with maximum gross weight of 1550 lb in experimental configuration or 1320 lb as a Light Sport Aircraft, and an empty weight of around 750 lb, noting that configuration choices affect both empty weight and performance. The standard Kitfox wing yields a cruise speed of close to 120 mph and has proven capable of operating from marvellously short strips in mountain terrain. Adding horsepower, as with the Titan X340 installation, directly increases both lift capability and climb rate. The aircraft has been reported to shrug off the performance penalties of hot weather and high altitude that affect most other types, and its short-field capability is described as quite good, suited to operating from just about anywhere a pilot might want to go. Trim-related handling refinements were still being worked on the development testbed at the time of reporting.
The STi is a variant of the Kitfox Series 7, distinguished from the standard Super Sport by its high-lift STOL wing with vortex generators, extended span and chord, and by the availability of higher-power engine options. The factory demonstrator and development airframe, registration N81KA, has itself worn multiple configurations over time, including a standard wing paired with a Rotax engine and, later, the STOL wing paired with the Titan X340, illustrating how the STi option can be combined with different engine choices. Engine options quoted for the STi include the Rotax 915 iS at 141 hp and the Titan X340 at 180 hp, with pilots reporting differing views on how the heavier, more powerful Titan affects the aircraft's handling compared with the lighter Rotax installation.
The Kitfox STi is most commonly seen exploring the backcountry or competing in short-takeoff-and-landing demonstrations, reflecting Kitfox's broader role in popularising backcountry flying among owners of experimental/amateur-built aircraft. It is flown by factory pilot, mountain flying instructor and transition trainer Paul Leadabrand for airshows and demonstrations around the country. As Kitfox's most powerful and highest-performing model, the STi had become the company's most popular Series 7 model, with the manufacturer building complete light sport aircraft for those who prefer not to build their own kit. Buyers have noted that a kit-built STi with the Titan X340 can be assembled for meaningfully less than the cost of a comparable factory-built example, though pricing and engine choice remain points of ongoing discussion among owners.
The Kitfox STi is a stick-and-rudder machine built for off-airport adventure, and that character carries through into how it should be flown: full attention to flaperon inputs across a nearly full-span control surface, active management of a high-lift STOL wing, and confidence operating from very short strips. Its swing-up gull-wing doors can be flown open, and the wide, convex glazing gives excellent visibility whether the doors are open or shut, which is part of what makes it well suited to the low-level canyon and backcountry flying it is associated with. Handling is lively due to its light weight and strong power-to-weight ratio, particularly in Rotax 915 iS-powered form, though it is correspondingly less settled in turbulence than heavier types. Pilots comparing engine options note the Titan X340 installation noticeably changes the handling feel relative to the standard Rotax powerplant, giving more punch on takeoff and climb at the cost of some of the lighter, more nimble feel of the standard STi.
