Schweizer SGS 1-35
Encyclopedia
The Schweizer SGS 1-35 is a United States
15 Meter Class
, single-seat, mid-wing glider built by Schweizer Aircraft
of Elmira, New York
.
The 1-35 was first flown in 1973 and a total of 101 were completed by the time production was completed in 1982.
sailplanes. Schweizer Aircraft evaluated the use of fiberglass for sailplane construction but rejected it for several reasons:
The company believed that it could get equivalent performance to fiberglass from the material that it knew best, aluminum. Experiments with the laminar flow
wing Schweizer SGS 1-29
in the late 1950s had shown that there was laminar flow potential in metal wings.
One of factors that convinced the company that there was a market for a US-made competition sailplane was the great loss of value of the United States Dollar
in the early 1970s which had made European sailplanes prohibitively expensive to US buyers.
The 1-35 is an all-metal aircraft with a monocoque
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 15 Metre Class allows flaps, the SGS 1-35 is equipped with plain flaps that can be selected from −8 to +32 degrees for soaring and inter-thermal speed and +32 to +82 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
. K & L Soaring now provides all parts and support for the Schweizer line of sailplanes.
The original 1-35 model has water ballast and retractable landing gear
1-35A
The "A" model incorporated several minor changes, including a sharper nosecone but retained the water ballast and retractable landing gear of the 1-35.
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.
, both introduced in 1976, out-classed it. The metal wing, while of good quality construction, just could not be made to hold an airfoil
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.
There are also five SGS 1-35s registered in Canada.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
15 Meter Class
Glider Competition Classes
Competition classes in gliding, as in other sports, mainly exist to ensure fairness in competition. However the classes have not been targeted at fostering technological development as in other sports...
, single-seat, mid-wing glider built by Schweizer Aircraft
Schweizer Aircraft
The Schweizer Aircraft Corporation is a manufacturer of sailplanes, agricultural aircraft and helicopters located in Horseheads, New York. It was incorporated in 1939 by three Schweizer brothers , who built their first glider in 1930...
of Elmira, New York
Elmira, New York
Elmira is a city in Chemung County, New York, USA. It is the principal city of the 'Elmira, New York Metropolitan Statistical Area' which encompasses Chemung County, New York. The population was 29,200 at the 2010 census. It is the county seat of Chemung County.The City of Elmira is located in...
.
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 fiberglassFiberglass
Glass fiber is a material consisting of numerous extremely fine fibers of glass.Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the invention of finer machine tooling...
sailplanes. Schweizer Aircraft evaluated the use of fiberglass for sailplane construction but rejected it for several reasons:
- The high cost of demonstrating to the Federal Aviation AdministrationFederal Aviation AdministrationThe Federal Aviation Administration is the national aviation authority of the United States. An agency of the United States Department of Transportation, it has authority to regulate and oversee all aspects of civil aviation in the U.S...
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 high degree of manual labor required to do fiberglass lay-ups at that time and the associated cost.
The company believed that it could get equivalent performance to fiberglass from the material that it knew best, aluminum. Experiments with the laminar flow
Laminar flow
Laminar flow, sometimes known as streamline flow, occurs when a fluid flows in parallel layers, with no disruption between the layers. At low velocities the fluid tends to flow without lateral mixing, and adjacent layers slide past one another like playing cards. There are no cross currents...
wing Schweizer SGS 1-29
Schweizer SGS 1-29
|-See also:-External links:*...
in the late 1950s had shown that there was laminar flow potential in metal wings.
One of factors that convinced the company that there was a market for a US-made competition sailplane was the great loss of value of the United States Dollar
United States dollar
The United States dollar , also referred to as the American dollar, is the official currency of the United States of America. It is divided into 100 smaller units called cents or pennies....
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
Monocoque is a construction technique that supports structural load by using an object's external skin, as opposed to using an internal frame or truss that is then covered with a non-load-bearing skin or coachwork...
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 15 Metre Class allows flaps, the SGS 1-35 is equipped with plain flaps that can be selected from −8 to +32 degrees for soaring and inter-thermal speed and +32 to +82 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, New York
Cayuta is a town in Schuyler County, New York, United States. The population was 545 at the 2000 census.The Town of Cayuta occupies the southeast corner of the county and is northeast of Elmira, New York.- History :...
. K & L Soaring now provides all parts and support for the Schweizer line of sailplanes.
Variants
1-35The original 1-35 model has water ballast and retractable landing gear
1-35A
The "A" model incorporated several minor changes, including a sharper nosecone but retained the water ballast and retractable landing gear of the 1-35.
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.
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 and the Glasflügel MosquitoGlasflügel 303
|-See also:-References:*Thomas F, Fundamentals of Sailplane Design, College Park Press, 1999*Simons M, Segelflugzeuge 1965-2000, Eqip, 2004-External links:**...
, both introduced in 1976, out-classed it. The metal wing, while of good quality construction, just could not be made to hold an airfoil
Airfoil
An airfoil or aerofoil is the shape of a wing or blade or sail as seen in cross-section....
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
World Gliding Championships
The World Gliding Championships is a gliding competition held every two years or so by the FAI Gliding Commission. The dates are not always exactly two years apart, often because the contests are sometimes held in the summer in the Southern Hemisphere....
competition, has proved popular due to its rugged metal airframe and aesthetic appeal.
In service
In May 2008 there were still 81 1-35s registered in the USA including:- 44 SGS 1-35
- 2 SGS 1-35A
- 35 SGS 1-35C
There are also five SGS 1-35s registered in Canada.
