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Aviation History
1983
1983 - 0349.PDF
PRIVATE FLIGHT Schweizer motorglider nears certification Schweizer's 2-37 motorglider is expected to be certificated in the USA by March. It will be the country's first domes tically-produced aircraft of this kind to be certificated, and one of the first to be designed to Joint Air worthiness Requirements. The specific regulation will be JAR 22, covering sailplanes and motorgliders, plus rele vant parts of the usual FAR 23. The aircraft, which has been under development for more than two years, was designed specifically to meet USAF Aeronautical Systems proposals for an off-the-shelf motorglider. Other aircraft considered included the Grob G109 and the Ryson ST-100 Cloudster. The Schweizer best fits the Air Force specifica tions, and a contract for eight 2-37s has been awarded. These should go to the USAF Academy at Colorado Springs by the summer. Schweizer's motorglider is described as being a "powered aircraft with sailplane capabilities". The USAF Academy has included a soar ing stage in its syllabus since the Fifties. Gliding has been found to be very beneficial in pilot training, with records indicating that a pilot with sailplane experience makes better progress. Cadets will initially fly the 2-37, then change to conventional sail- m AtmiBSSm^ *MiUJM»fr |ri •iimi _ » Schweizer plans high-altitude surveillance developments of the 2-37, following civil applications planes. The Academy now has some 15 Schweizer sail planes—one 2-33, one 1-34, seven 2-32s, and l-26s for the remainder. The Schweizer SGM 2-37 for the USAF will be powered by a 112 h.p. Lycoming 0-235, derated to 105 h.p. and swing ing a two-bladed Sensenich metal propeller. The whole engine package, from the fire wall forward, comes from the Piper Tomahawk. Schweizer has also used time-proven and highly effi cient components from some of its other sailplanes on the 2-37. The rear tail cone and tail surfaces are from the SGS Aft fuselage section in jig, with completed unit alongside 2-32; the wing panels, includ ing the air brakes and ailerons, are from the 1-36 Sprite, although strength ened. The structure is all- metal except for the fabric- covered rudder and tubular steel landing gear, and is of conventional construction. The wing employs a built-up aluminium spar in three sections—centre and out board. Strengthening has been accomplished by using additional reinforcing strips in the wing at the root ends and heavier gauge aluminium in the spar butt plates. The fuselage is a modified monocoque structure with bulkheads, stringers, and skins. The wing has a Wort- mann FX 61-163 laminar flow aerofoil section from the root running outboard to the ailerons, and an FX 60-126 aerofoil at the tips. The stabilator is constructed simi larly to the wing; the rudder has a fabric-covered alumi nium frame. The 9ft track fixed landing gear is fitted with 5-00 x 5 main wheels for the USAF aircraft, which will be operating from hard surfaces. Schweizer plans to build a ninth 2-37 to be used for research and commercial development. It will be powered by a 150 h.p. Lyco ming O-320 with a feathering propeller, plus 6 00 x 6 wheels for grass field and rougher terrain operations. At a later point it could also be fitted with a Limbach/Hoff- mann engine/propeller, as Schweizer is looking towards a wide range of derivations from the basic 2-37. An Air Force 2-37 will not employ a stop/start in-flight procedure as with most other motorgliders, because of the fixed pitch propeller. Instead, it will be flown as a glider, with the engine idling. Schweizer will probably have the follow-on commercial and derivative craft with stop/ start capability. Retractable gear is also being considered. The cockpit has a large aft- sliding canopy which provides excellent visibility. Width of the cockpit is 43in at the widest point, and the control arrangement allows student and instructor to fly with their right hands on the control stick, and their left on the airbrake lever. The two- surface brakes cover an area of 5 • 88ft2, but they will prob ably be lengthened to increase the area by about 30 per cent. A glide ratio of 27:1 is claimed at gross weight, and at 64 m.p.h. (engine idle). Schweizer expects a similar glide ratio with a feathered propeller. With extended dive brakes the glide ratio is said to be approximately 10:1. A single throttle is in the panel centre. A 15 US gal fuel tank is in the leading edge of the left wing inboard section on the first aircraft, but another 15 gal tank will probably be added to the starboard wing, and will be standard in the other seven Air Force machines. The SGM 2-37 is FLIGHT International, 26 February 1983 517
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