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Ultra Light Aircraft Corp (ULAC) X-99


Tandem two-seat single-engined high-wing monoplane with conventional three-axis control. Wing has unswept leading and trailing edges, and constant chord; V-tail. Pitch/yaw control by elevon; roll control by one-third-span spoilers; control inputs through stick for pitch/roll and pedals for yaw. Wing braced from above by kingpost and cables, from below by cables; wing profile 100% double-surface. Undercarriage has three wheels in tail-dragger formation; steel-spring suspension on tailwheel and suspension on main wheels. Push-right go-right tailwheel steering connected to yaw control. Brakes on main wheels. Aluminium-tube framework, with optional pod. Engine mounted below wing driving pusher propeller.

Georges Borgeaud, the president of ULAC, acquired on the 14 August 1981 the rights to sell in Europe and Africa the Maxair Hummer. Starting with the basic single-seater model designed by the late Klaus Hill, ULAC has developed its own tandem two-seater, the X-99. The transformation principally involved raising and reinforcing the wing, increasing the track of the undercarriage, the addition of spoilers to change the machine into a conventional three-axis control aircraft and finally the adoption of the Hirth motor.

The prototype made its first flights at the beginning of 1982 above the Californian desert near to Salton Sea. For the distribution of this aircraft, George Borgeaud built a factory at Monthey in the Vallais area in Switzerland. Shown at the first European Salon of Microlights at Lyon-Bron in Septem-ber 1982, and later at the microlight assembly at Blois in France, this machine met with considerable success amongst the established pilots at whom it is aimed. Georges has consistently followed an intelligent sales policy, hinged on safety, and will only sell this aircraft in Europe to qualified private pilot's licence holders.

Ready-to-fly X-99s cost US$8650 in 1983 ex-works for the standard version, trailer included. Standard are compass, ASI, altimeter, rev counter and CHTG. As an option, it can have climb, turn and slip gauges. Its spoilers can be used together as air brakes and the machine can be flown solo (from the front seat) without any modification. The rear seat can be replaced by a large supplementary fuel tank and other options include skis, floats, pod, main wheel fairings, dual controls, a second instrument panel for the rear seat and a three-blade propeller.

Georges was working on a new wing design which can be rigged in two different spans - 32.8 ft or 45.9 ft (10.00 or 14.00 m), and the larger span would bring the X-99 comfortably within British ultralight law.

Length overall 17.1 ft, 5.75 m]
Height overall 8.8 ft, 2.65 m
Wing span 34.1 ft, 10.40 m
Constant chord 4.4ft, 1.32 m
Sweepback 0 deg
Tailplane span 8.2 ft, 2.50 m
Fin height 2.1ft, 0.90m
Total wing area 147 sq.ft, 13.7 sq.m
Total spoiler area 1.9 sq.ft, 0.18 sq.m
Tailplane area 19.4 sq.ft, 1.8 sq.m
Total elevon area 13.6 sq.ft, 1.3 sq.m
Wing aspect ratio 7.9/1
Wheel track 4.1 ft, 1.24 m
Wheelbase 7.5 ft, 2.25 m
Tailwheel diameter overall 10 inch, 26 cm
Main wheels diameter overall 14 inch, 35 cm
Floats, dimensions 10. 1 x 2.0 ft, 3.30 x 0.59 m
Skis, dimensions 2.1 x 0.6 ft, 0.87 x 0.14 m
Engine: Hirth 272R 438 cc, 40 hp at 7000 rpm
Prop-eller diameter and pitch 54 x 30 inch, 1.37x0.76m
Toothed-belt reduction, ratio 2.2/1
Max static thrust 252 lb, 114 kg
Power per unit area 0.27 hp/sq.ft, 2.9 hp/sq.m
Fuel capacity 3.2 US gal, 2.7 Imp gal, 12.0 litre in main tank
Fuel capacity 21.7 US gal, 18.1 Imp gal, 82.0 litre in reserve
Empty weight 320 lb, 145kg
Max take-off weight 662 lb, 300kg
Payload 3421b, 155 kg
Max wing loading 4.501b/sq.ft, 21.9kg/sq.m
Max power loading 16.6 lb/hp, 7.5kg/hp
Load factors; +5.0, -3.0 ultimate
Max level speed 62 mph, 100 kph
Never exceed speed 71 mph, 115 kph
Max cruising speed 53 mph, 85 kph
Economic cruising speed 44 mph, 70 kph
Stalling speed 24 mph, 38 kph
Max climb rate at sea level 350 ft/min, 1.8 m/s
Min sink rate 680 ft/min at 28 mph, 3.5 m/s at 45 kph
Best glide ratio with power off 7/1 at 37 mph, 60 kph
Take-off distance 180 ft, 55 m
Land-ing distance 80ft, 24m
Service ceiling 13,100ft, 4000 m
Range at average cruising speed 75 mile, 120 km



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