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Ultrasports RB1

RB1 / Lightning DS

The Ultrasports/Southdown Sailwings RB1/Lightning DS is a single-seat single-engined flex-wing aircraft with weight-shift control. Rogallo wing with fin. Pilot suspended below wing in trike unit, using bar to control pitch and yaw/roll by altering relative positions of trike unit and wing. Wing braced from above by kingpost and cables, from below by cables; floating cross-tube construction with > 75 % double-surface enclosing cross-tube; pre-formed ribs. Undercarriage has three wheels in tricycle formation; optional steel-spring suspension on nosewheel and no suspension on main wheels. Push-right go-left nosewheel steering independent from yaw control. No brakes. Aluminium-tube trike unit, with optional pod. Engine mounted below wing driving pusher propeller. Trike unit has pod.

The RB1/Lightning DS was constructed specially for an attempt on the world microlight altitude record, it consists of a specially lightened Tripacer trike unit with a big Southdown Sailwings Lightning DS wing, more usually found on two-seaters.

The engine, an experimental unit from British Robin importer Nicklow Engineering, consisted basically of two Robin 250 cc barrels on a 440cc crankcase, giving the benefit of 488cc without expensive machining. To in-crease the power still further, the cooling fan is removed, the engine relying on free-air cooling.

Even in its original form the trike did the job it was designed to do, taking Bob Calvert to a new world record of 19,250ft (5900m) off the Lan-cashire coast on 19 February 1983 and breaking by over 3000 ft (900 m) Bob's own record set a year earlier in a Mainair Tri-Flyer 330.

Engine: Robin EC488PM, 65 hp at 6500 rpm
Prop-eller diameter and pitch 60x30ft, 1.52x0.76m
Toothed-belt reduction, ratio 2.8/1
Max static thrust 350 lb, 159 kg
Power per unit area 0.33 hp/sq.ft, 3.6 hp/sq.m
Fuel capacity 4.8 US gal, 4.0 Imp gal, 18.2 litre
Wing span 32.0ft, 9.75m
Chord at root 8.0ft, 2.44m
Chord at tip 3.0ft, 0.91m
Dihedral 0 deg
Sweepback 30 deg
Total wing area 175 sq.ft, 16.3 sq.m
Wing aspect ratio 5.8/1
Height overall 11.0 ft, 3.35 m
Empty weight 231 lb, 105kg
Max take-off weight 531 lb, 241kg
Payload 300 lb, 136kg
Max wing loading 2.72 lb/sq.ft, 13.3 kg/sq.m
Max power loading 8.2 lb/hp, 3.7kg/hp
Load factors +4.0, -2.0 design; +6.0, -3.0 ulti-mate
Never exceed speed 65mph, 105kph
Max cruising speed 50 mph, 80 kph
Economic cruising speed 40 mph, 64 kph
Stalling speed 28 mph, 45 kph
Max climb rate at sea level 1700 ft/min, 8.6 m/s
Min sink rate 300 ft/min at 32 mph, 1.5 m/s at 51 kph
Best glide ratio with power off 6/1 at 35 mph, 56 kph
Take-off distance 30ft, 10 m
Landing distance 40ft, 12 m
Range at average cruising speed 345 mile, 555 km


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