Spalinger S.25

Last updated
S.25
RoleTwo-seat training glider
National origin Switzerland
ManufacturerAG Wynau
DesignerJakob Spalinger
First flightJune 1946
Number built3
Developed from Spalinger S.21

The Spalinger S.25 is a 1940s development of the S.21 two seat trainer with much improved visibility from the rear seat. Three examples were completed, each different to the others.

Spalinger S.21 Swiss 1930s trainer glider

The Spalinger S.21 is a Swiss two-seat trainer glider flown in the late 1930s. They were heavily used as trainers but also set many new Swiss national records in the two-seat category.

Contents

Design and development

When the design of the S.25 began in 1942 it was seen as a version of the two seat S.21 but the problem of providing a good view from the rear cockpit, which was under the wing in the S.21, whilst keeping it close to the c.g. resulted in a serious change in wing plan and with it, a change of designation. Though Switzerland remained neutral during World War II, associated supply restrictions delayed the completion of the S.25 and its first flight was not made until June 1946. [1]

Switzerland federal republic in Central Europe

Switzerland, officially the Swiss Confederation, is a sovereign state situated in the confluence of western, central, and southern Europe. It is a federal republic composed of 26 cantons, with federal authorities seated in Bern. Switzerland is a landlocked country bordered by Italy to the south, France to the west, Germany to the north, and Austria and Liechtenstein to the east. It is geographically divided between the Alps, the Swiss Plateau and the Jura, spanning a total area of 41,285 km2 (15,940 sq mi). While the Alps occupy the greater part of the territory, the Swiss population of approximately 8.5 million is concentrated mostly on the plateau, where the largest cities are located, among them the two global cities and economic centres of Zürich and Geneva.

World War II 1939–1945 global war

World War II, also known as the Second World War, was a global war that lasted from 1939 to 1945. The vast majority of the world's countries—including all the great powers—eventually formed two opposing military alliances: the Allies and the Axis. A state of total war emerged, directly involving more than 100 million people from over 30 countries. The major participants threw their entire economic, industrial, and scientific capabilities behind the war effort, blurring the distinction between civilian and military resources. World War II was the deadliest conflict in human history, marked by 50 to 85 million fatalities, most of whom were civilians in the Soviet Union and China. It included massacres, the genocide of the Holocaust, strategic bombing, premeditated death from starvation and disease, and the only use of nuclear weapons in war.

Like the S.21, the S.25 has a high-mounted, strut-braced gull wing. Apart from the revised plan, the two aircraft's wings are similar in construction, span and area. Both are built around a single spar with ply covering ahead of it forming a torsion-resistant D-box and have internal, angled drag struts from the inner spar to the wing mounting on the upper fuselage which act also as the rear of longer-chord D-boxes. Externally the wings are braced with a single strut on each side from spar to the fuselage keel. Both are fabric-covered behind spars and drag struts. The outer wings of both designs are straight-tapered out to elliptical tips and carry fabric-covered ailerons. However, the leading edge of the outer part of the S.25's wing is unswept over the outer 67% and the rest is reverse swept at about 11°. The straight trailing edge is parallel to the reverse-swept leading edge, continuing out to the tips. Both designs have airbrakes mounted on the rear of the spars, though the more angled drag struts of the S.25 allow its airbrakes to be wider. [1] [2]

Strut structural component designed to resist longitudinal compression

A strut is a structural component commonly found in engineering, aeronautics, architecture and anatomy. Struts generally work by resisting longitudinal compression, but they may also serve in tension.

Gull wing Aircraft wing configuration with bend at root

The gull wing is an aircraft wing configuration with a prominent bend in the wing inner section towards the wing root. Its name is derived from the seabirds which it resembles. It has been incorporated in aircraft for many reasons.

Spar (aeronautics) Main structural member of the wing of an aircraft

In a fixed-wing aircraft, the spar is often the main structural member of the wing, running spanwise at right angles to the fuselage. The spar carries flight loads and the weight of the wings while on the ground. Other structural and forming members such as ribs may be attached to the spar or spars, with stressed skin construction also sharing the loads where it is used. There may be more than one spar in a wing or none at all. However, where a single spar carries the majority of the forces on it, it is known as the main spar.

With the rear seat now ahead of the wing leading edge, only the forward part of the fuselage of the S.25 differs from that of the S.21. The tandem seats are under a single, multi-framed canopy reaching back to the wing leading edge, though the upward field of view from the rear seat is enhanced by a transparency in the wing which extends back to the drag strut. The wing is attached to the upper fuselage instead of the S.21's pedestal, which provided headroom for its rear seat. Otherwise, the two designs share a wood-framed fuselage, oval in section and plywood-skinned. which tapers rearwards to a small fin that carries a large, curved balanced rudder with a rather pointed tip. Its nearly triangular tailplane is largely forward of the rudder hinge. The elevators are rounded in plan. [1] [2]

Tandem arrangement in which people, machines, or animals are in line behind one another facing forward

Tandem, or in tandem, is an arrangement in which a team of machines, animals or people are lined up one behind another, all facing in the same direction.

Plywood manufactured wood panel made from thin sheets of wood veneer

Plywood is a material manufactured from thin layers or "plies" of wood veneer that are glued together with adjacent layers having their wood grain rotated up to 90 degrees to one another. It is an engineered wood from the family of manufactured boards which includes medium-density fibreboard (MDF) and particle board (chipboard).

Fin flight control surface

A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. Fins are also used to increase surface areas for heat transfer purposes, or simply as ornamentation.

The S.25 lands on a rubber-sprung skid which reaches forward from mid-chord nearly to the nose. [1]

Chord (aeronautics) imaginary straight line joining the leading and trailing edges of an aerofoil

In aeronautics, a chord is the imaginary straight line joining the leading and trailing edges of an aerofoil. The chord length is the distance between the trailing edge and the point on the leading edge where the chord intersects the leading edge.

Most of Spalinger's designs had wooden fuselages but he also built one-off, steel tube-framed versions of both the S.21 (the S.21-III or S.21M) and the S.25. The latter, like the wooden S.25, was completed in 1946 [3] and was designated the S.24 even though it seems to have flown after the wooden original. [1] It appears on the Swiss register as the S.25M. [3]

In Brazil a second S.25 was built with Spalinger's approval by two Swiss nationals, Hans Widmer and Kurt Hendrich in 1954. Designated S.25A, it has a revised canopy which provided more headroom and a monowheel for landing. [1]

Operational history

In 1947 the two pilots Hans Würth and K. Haberstich brought the S.25 to England for the National Gliding Contests based at Bramcote. They did not compete but set a new Swiss two-seat glider distance record of 210 km (130 mi; 110 nmi) with a flight to the east coast of Norfolk. [1] [4] Members of the Great Hucklow-based Derbyshire and Lancashire Gliding Club taking part in the contest saw it and expressed an interest in its purchase, so it was air-towed to their ground. After several months of testing did not lead to a sale, the S.25 was air-towed back home. [1]

The Brazilian S.25A PT-PBR was bought by the Aeroclub de Bauru. It was placed third in the 1955 Brazilian National Gliding Championships and continued to compete for that club until at least December 2014. [5]

The history of the metal-framed S.25M is not known in detail. Owned by Peter Kindler, it remains on the Swiss register in June 2019 as HB-437. [3]

Variants

S.25
Swiss built example with wooden fuselage. One only.
S.25A
Brazilian example built in 1954, with modified, raised canopy and a landing wheel. One only.
S.24
Swiss example with tube-frame fuselage. One only, sometimes referred to as the S.25M.

Specifications (S.25)

Data from j2mc planeurs - Spalinger S-25 [6]

General characteristics

Performance

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References

  1. 1 2 3 4 5 6 7 8 Simons, Martin (2006). Sailplanes 1945-1965 (2nd revised ed.). Königswinter: EQIP Werbung & Verlag GmbH. pp. 114–6. ISBN   3 9807977 4 0.
  2. 1 2 Pedrielli, Vincenzo; Camastra, Francesco (2011). Italian Vintage Sailplanes. Königswinter: EQIP Werbung & Verlag GmbH. pp. 242–3. ISBN   9 783980 883894.
  3. 1 2 3 "Swiss Aircraft Register" . Retrieved 19 June 2019.
  4. ↑ "National Gliding Contests". Flight . LII (2010): 10–13. 3 July 1947.
  5. ↑ "US nightly soaring" . Retrieved 17 June 2019.
  6. ↑ "Spalinger S-25" . Retrieved 31 May 2019.
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