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Niemi Sisu 1A
Arlington Aircraft Sisu 1A




The prototype, designed and built over a period of six years by Convair engineer Leonard Niemi in his garage workshop and known as the Sisu 1, 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 had a lighter wing structure, and 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.
Sisu 1A
Flown for the first time on 20 December 1958, 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,.
The Sisu 1 A set three world records for Alvin Parker out of Odessa, Texas: 784 km/ 487.24 mileson 27 August 1963, 1963; free distance 1,041.52 km. /647.17 milesto Kimball, Nebraska, on 31 July 1964; and goal, 930.6 km. / 578.27 miles, 1969. For the free distance flight Parker had an aero-tow to 2000 ft, soared to 14,300 ft and was airborne for more than 10.5 hours.

The Sisu 1A N1100Z, the second 1A to be built, that set the world distance record was donated to the Smithsonian Air & Space Museum and another was donated to the National Soaring Museum.

The type has won the US National Soaring Championships three times, in 1962,1965 and 1967, flown by different pilots (John Ryan, 1962; Dean Svec, 1965; and A.J. Smith 1967). A. J. Smith, winner of the 1967 US Championships, further lightened his ship, and flew his Sisu for a time with wing tip extensions to increase the span from the standard 50ft 0in.
Span: 15.24m / 50 ft 0 in
Length: 6.46 m / 21 ft 2.5 in
Wing area: 10.03sq.m / 108.0 sq.ft
Aspect ratio: 23.1
Airfoil: NACA 65 (3)-418
Empty Weight: 222kg / 490lb
Gross Weight: 347kg / 765lb
Payload: 125kg / 275lb
Wing Load: 34.6kg/sq.m / 7.1lb/sq.ft
Max speed: 161 mph / 140 kt / 260 km/h (in smooth air)
Stalling speed: 35.5 kt / 68 km/h
Max rough air speed 70 kt (130 km/h)
Min sinking speed: 0.64 m/s / 2.07 ft/sec / 1.24 kt at 55 mph / 47.5 kt / 88 km/h
L/DMax: 37 @ 92 kph / 50 kt / 57 mph
Best glide ratio: 41.4:1 at 62 mph / 54 kt / 100 km/h
No. of Seats: 1
No. Built: 11






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