The Robertson B1-RD STOL ultralight was designed to comply with the US FAR 103 Ultralight Vehicles rules, including the category’s maximum empty weight of 254 lb (115 kg). The B1-RD has a standard empty weight of 220 lb (100 kg). It has a cable-braced high-wing, single-seat, open cockpit, single engine in tractor engine configuration, and is equipped with conventional landing gear.
The aircraft is made from bolted together aluminum tubing with the wings and tail surfaces covered in Dacron sailcloth. Its 32 ft (9.8 m) span wing is cable-braced to a top surface inverted “V” kingpost. The wing is a single-surface airfoil with a double-surface wing covering optional. The controls are conventional three-axis, including Junkers-style flaperons. The main fuselage structure is an aluminum keel tube that runs from the tail, mounts the wings and then the engine at the front.
The original standard engines were the 30 hp (22 kW) Cuyuna 430R and the 20 hp (15 kW) Cuyuna 215. The landing gear has bungee-suspension on all three wheels and the tailwheel is steerable.
Designed and developed as a high-wing, single-engine monoplane with tractor configuration, the Bl-RD was the initial model for Robertson Aircraft Corporation, the first major aircraft company to enter the ultralight field. Among features incorporated in this “BIRD” are large-span, hanging ailerons to enhance roll control in a conventional three-axis control system. A center-mounted stick activates the displaced ailerons and elevator, and pedals control the rudder.
A single-surface wing, versus double-surface design, is used in keeping with the builder’s intention to provide “superior handling at minimum risk.” This results in slower cruising speed, but also substantially reduces stall speed (from around 25 mph. to about 15 mph. ).
Robertson’s ultralight is designed for a 260-pound payload, and because fuel is limited to a maximum of 3.6 gallons (22 pounds), the pilot can weigh as much as 238 pounds without pushing the B1 -RD beyond limits.
Standard engine is the 20-hp. single-cylinder Cuyuna 215R (mounted ahead of wing) with 3.65 reduction and recoil restart capability. An optional engine was the Cuyuna 430R, a 30-hp., 429 cc. twin-cylinder powerplant.
The undercarriage features taildragger landing gear with bungee shock cord suspension, 16-inch main wheels and steerable tailwheel.
Options include remote starter and choke kit, 4-gallon fuel tank, 20-inch wheels, windscreen, chrome fenders and hardware, chromed axle, instruments, floats, custom sails, parachute, and storage bags.
Specifications:
Wingspan: 32 ft 0 in (9.75 m)
Wing area: 162 sq ft (15.1 m2)
Empty weight: 220 lb (100 kg)
Gross weight: 500 lb (227 kg)
Fuel capacity: 4 U.S. gallons (15 L; 3.3 imp gal)
Powerplant: 1 × Cuyuna 430R two-cylinder, two-stroke aircraft engine, 30 hp (22 kW)
Maximum speed: 50 mph (80 km/h; 43 kn)
Cruise speed: 38 mph (61 km/h; 33 kn)
Stall speed: 15 mph (24 km/h; 13 kn)
Never exceed speed: 75 mph (121 km/h; 65 kn)
Range: 125 mi (109 nmi; 201 km)
Service ceiling: 14,000 ft (4,300 m)
g limits: +3/-2
Maximum glide ratio: 8.5:1
Rate of climb: 850 ft/min (4.3 m/s)
Rate of sink: 300 ft/min (1.5 m/s)