The Schweizer SGS 1-35 is a United States 15 Meter
Class
Class, Classes, or The Class may refer to:
Common uses not otherwise categorized
* Class (biology), a taxonomic rank
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, single-seat, mid-wing glider built by
Schweizer Aircraft
The Schweizer Aircraft Corporation was an American manufacturer of sailplanes, agricultural aircraft and helicopters located in Horseheads (town), New York, Horseheads, New York. It was incorporation (business), incorporated in 1939 by three Sc ...
of
Elmira, New York
Elmira () is a Administrative divisions of New York#City, city in and the county seat of Chemung County, New York, United States. It is the principal city of the Elmira, New York, metropolitan statistical area, which encompasses Chemung County. ...
.
[Said, Bob: ''1983 Sailplane Directory, Soaring Magazine'', page 33. Soaring Society of America, November 1983. USPS 499-920]
The 1-35 was first flown in 1973 and a total of 101 were completed by the time production was completed in 1982.
Background
By the early 1970s competition in the open, standard and 15 meter classes was dominated by
fiberglass
Fiberglass (American English) or fibreglass (English in the Commonwealth of Nations, Commonwealth English) is a common type of fibre-reinforced plastic, fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened i ...
sailplanes. Schweizer Aircraft evaluated the use of fiberglass for sailplane construction but rejected it for several reasons:
[Schweizer, Paul A: ''Wings Like Eagles, The Story of Soaring in the United States'', pages 159-209. Smithsonian Institution Press, 1988. ]
*The high cost of demonstrating to the
Federal Aviation Administration
The Federal Aviation Administration (FAA) is a Federal government of the United States, U.S. federal government agency within the United States Department of Transportation, U.S. Department of Transportation that regulates civil aviation in t ...
that this new material could safely be used for aircraft primary structure.
*Problems with crash resistance of fiberglass structures in high-impact accidents.
*The unknown service life of fiberglass.
*The large amount of manual labor required to do fiberglass lay-ups at that time and the associated cost.
The company believed it could get performance equivalent to fiberglass from the material it knew best –
aluminum
Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
. Experiments with the
laminar flow
Laminar flow () is the property of fluid particles in fluid dynamics to follow smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing. At low velocities, the fluid tends to flow without lateral m ...
wing of the
Schweizer SGS 1-29 in the late 1950s had shown there was potential for laminar flow around metal wings.
[Said, Bob: ''1983 Sailplane Directory, Soaring Magazine'', page 32. Soaring Society of America, November 1983. USPS 499-920]
One of the factors that convinced the company there was a market for a US-made competition sailplane was the loss of value of the
United States Dollar
The United States dollar (Currency symbol, symbol: Dollar sign, $; ISO 4217, currency code: USD) is the official currency of the United States and International use of the U.S. dollar, several other countries. The Coinage Act of 1792 introdu ...
in the early 1970s which had made European sailplanes prohibitively expensive to US buyers.
Development
Schweizer Aircraft started construction of the 1-35 prototype in late 1972 and it first flew in April 1973. The company carried out side-by-side comparisons with fiberglass sailplanes as part of 50 hours of flight evaluations before making the decision to proceed with manufacturing the design on 10 May 1973.
The 1-35 is an all-metal aircraft with a
monocoque
Monocoque ( ), also called structural skin, is a structural system in which loads are supported by an object's external skin, in a manner similar to an egg shell. The word ''monocoque'' is a French term for "single shell".
First used for boats, ...
fuselage. The wing has a single spar and the stressed skin features multi-stringers for stiffness, to best retain airfoil shape and laminar flow. The aircraft's elevator and rudder are fabric covered. The 1-35 carries 320 lb (145 kg) of water ballast in two wing tanks.
Because the 1969 design rules for the
Standard Class allowed flaps, the SGS 1-35 is equipped with plain flaps that can be selected from −8 to +18 degrees for soaring and inter-thermal speed and +30 to +80 degrees for landing.
The 1-35 received type certificate G4EA on 25 April 1974.
The type certificate is currently held by K & L Soaring of
Cayuta, New York
Cayuta is a town in Schuyler County, New York, United States. As of the 2020 census, the population was 508.
The Town of Cayuta occupies the southeastern corner of the county and is northeast of Elmira. It is part of the Elmira Metropolitan ...
. K & L Soaring now provides all parts and support for the Schweizer line of sailplanes.
Variants
;1-35
The original 1-35 model has water ballast and retractable landing gear
58 built.
;1-35A
The "A" model moved the retractable main wheel further forward to allow the deletion of the nose skid. It also included a number of small aerodynamic refinements to further increase performance, including a sharper nosecone which was also used on regular 1-35s later in production. 2 built.
;1-35B
There was no 1-35B model
;1-35C
The "C" stood for "Club" as this model was intended to be a high-performance sailplane for recreational, as opposed to competition, flying. It was designed to appeal to private owners, commercial rental operations and gliding clubs. The "C" has fixed landing gear and no provisions for water ballast.
41 built.
Competition use
The 1-35 was only competitive for a very short period of time in the early 1970s before European sailplanes such as the
Schempp-Hirth Mini-Nimbus
The Schempp-Hirth Mini Nimbus is a 15 Metre-class glider designed and built by Schempp-Hirth GmbH in the late 1970s.
Design and development
In designing the Mini-Nimbus, Klaus Holighaus incorporated the flapped wings from the Glasflügel 3 ...
and the
Glasflügel Mosquito
The firm Glasflügel () was founded by Eugen Hänle in 1962 and was located in Schlattstall, south of Kirchheim unter Teck. It was the first firm to manufacture a glass-fibre sailplane in large numbers. It was also responsible for a large number ...
, both introduced in 1976, out-classed it. The metal wing, while of good quality construction, just could not be made to hold an
airfoil
An airfoil (American English) or aerofoil (British English) is a streamlined body that is capable of generating significantly more Lift (force), lift than Drag (physics), drag. Wings, sails and propeller blades are examples of airfoils. Foil (fl ...
profile to the same accuracy as a fiberglass wing.
The SGS 1-35 would mark the last attempt by the company to produce a competition sailplane.
The 1-35 quickly found a home as a club and personal glider and, other than in national or
world-class competition, has proved popular due to its rugged metal airframe and aesthetic appeal.
In service
As of May 2025 there were still 55 1-35s registered in the USA including:
*27 SGS 1-35
*2 SGS 1-35A
*26 SGS 1-35C
There are also five SGS 1-35s registered in Canada.
Museum aircraft
The prototype SGS 1-35, N17900 is on display in the
National Soaring Museum
The National Soaring Museum (NSM) is an aviation museum whose stated aim is to preserve the history of motorless flight. It is located in Big Flats Town, New York, on top of Harris Hill near Elmira.
The NSM is the Soaring Society of America's ...
.
A SGS 1-35, N135V is hung from the ceiling inside the UTA Engineering building in Arlington, Texas.
Specifications
See also
References
External links
Side view photo of SGS 1-35 prototype N17900 in the NSMFront view photo of SGS 1-35 prototype N17900 in the NSMPhoto of an SGS 1-35APhoto of an SGS 1-35C
{{Schweizer aircraft
1970s United States sailplanes
Schweizer aircraft
Mid-wing aircraft
Aircraft first flown in 1973