Niemi Sisu 1A

M.Hardy. Gliders & Sailplanes of the world

Sisu 1A

Designed and built over a period of six years by Convair engineer Leonard Niemi in his garage workshop, this American high performance single-seater was noteworthy in being the first sailplane ever to exceed 1,000km in a soaring flight when, flown by Alvin H. Parker, it set up an international straight line distance record of 1,041.52km (647.17 miles) in a flight from Odessa, Texas, to Kimball, Nebraska, on 31 July 1964. Alvin Parker also set up two other world records in the Sisu 1A, including a goal flight record of 487.24 miles on 27 August 1963, and the type has won the US National Soaring Championships three times, in 1962, 1965 and 1967, flown by different pilots. The Sisu 1A N1100Z, the second 1A to be built, which set the straight line distance record, is now in the Smithsonian Institute and A. J. Smith, winner of the 1967 US Champion ships, flew his Sisu for a time with wing tip extensions to increase the span from the standard 50ft 0in. The prototype, known as the Sisu 1, flew for the first time on 20 December 1958, and was a cantilever shoulder-wing type of all-metal construction with a laminar flow wing of NACA 65-series section to provide very low drag over a broad speed range, with forward sweep to delay tip stall. The 'butterfly'-type V-tail has an included angle of 90°. The two-spar wing has an aluminium alloy skin and plate stringers, with glassfibre/foam stiffening in the leading edge and camber-changing flaps. To achieve the smoothness and accuracy necessary for laminar flow, wing contours were filled and sanded, and all control surface hinge lines and joints in the canopy and removable fairings were sealed. The Sisu 1A was the production version, 10 of which were built by Arlington Aircraft at Arlington, Texas, and later at Greenville, South Carolina, between 1960 and 1965. This version featured vented air brakes and large-span slotted flaps. Landing gear consists of a retractable monowheel and a miniature fixed tailwheel; the pilot sits under a flush-fitting two-piece canopy.

Span: 50 ft 0 in
Length: 21 ft 2 1/2 in
Wing area: 108.0 sqft
Aspect ratio: 23.1
Empty weight: 546 lb
Max weight: 755 lb
Max speed: 161 mph (in smooth air)
Min sinking speed: 2.07 ft/sec at 55 mph
Best glide ratio: 41.4:1 at 62 mph