Niemi Sisu 1-A

Glider Reg. Number: N1003

1964

Design & Development

The Sisu 1A is a competition sailplane built in the United States in the late 1950s and early 1960s. Originally designed by Leonard Niemi as a home built sailplane, its first flight in 1958 showed such promise that Niemi decided instead to manufacture it in series production.

Niemi formed the Arlington Aircraft Company for this purpose. The Sisu 1A quickly proved itself as the most competitive American sailplane ever developed, winning the 1962, 1965, and 1967 U.S. National Soaring Championships. On July 31, 1964, a Sisu 1A, piloted by Alvin H. Parker, became the first sailplane ever to fly farther than 1000 km

Specifications

General characteristics

• Crew: 1
• Length: 20 ft 10 in (6.35 m)
• Wingspan: 50 ft 0 in (15.25 m)
• Height: 3 ft 5 in (1.04 m) at cockpit
• Wing area: 108.5 sq ft (10.08 m²)
• Aspect ratio: 23.1
• Airfoil: NACA 653 418 a=0.5
• Empty weight: 493 lb (223.5 kg)
• Gross weight: 712 lb (323 kg)

Performance

• Stall speed: 41 mph; 36 kn (66.2 km/h)
• Never exceed speed: 162 mph; 140 kn (260 km/h)
• Rough air speed max: 135.5 mph (218.1 km/h; 117.7 kn)
• Aerotow speed: 118 mph (189.9 km/h; 102.5 kn)
• Winch launch speed: 80 mph (128.7 km/h; 69.5 kn)
• g limits: +6 -4 at 135.5 mph (218.1 km/h; 117.7 kn)
• Maximum glide ratio: 41.4 at 62 mph (99.8 km/h; 53.9 kn)
• Rate of sink: 123.0 ft/min (0.625 m/s) at 55 mph (88.5 km/h; 47.8 kn)
• Wing loading: 6.56 lb/sq ft (32.05 kg/m²)