ITS-IVB

ITS-IVB
Role	High performance research glider
National origin	Poland
Manufacturer	ZASPL
Designer	Adam Nowotny, Franciszek Kotowski
First flight	30 July 1935
Number built	1

Last updated September 08, 2019

The ITS-IVB was a 1930s Polish two seat research sailplane designed to gather meteorological and airframe stress data. The sole example remained in service up to outbreak of World War II.

Poland, officially the Republic of Poland, is a country located in Central Europe. It is divided into 16 administrative subdivisions, covering an area of 312,696 square kilometres (120,733 sq mi), and has a largely temperate seasonal climate. With a population of approximately 38.5 million people, Poland is the sixth most populous member state of the European Union. Poland's capital and largest metropolis is Warsaw. Other major cities include Kraków, Łódź, Wrocław, Poznań, Gdańsk, and Szczecin.

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 70 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.

Design and development

The ITS-IV was a high performance, two seat research sailplane designed initially by Adam Nowotny to gather meteorological and airframe stress data. It was also intended to provide blind flying training. Franciszek Kotowski took over the design work after Nowotny's death in July 1934,^[1] producing the ITS-IVB.^[1]

It was an all-wood aircraft. The two part wing had a rectangular plan central section and gently tapering trapezoidal outer panels with blunted tips. Each part was built around a single plywood D-box spar which formed the leading edge. On each side an internal auxiliary drag strut ran diagonally from the spar at about mid-span to the rear of the wing root and the whole area between spar and strut was ply-covered, forming another box. Elsewhere, the wings were fabric-covered, as were the differential ailerons which filled the trailing edges of the outer panels. The wing bracing was unusual, with the normal rigid struts replaced by upper and lower steel ribbons on each side. Each upper ribbon ran from a central cabane, formed from three steel tubes, to a reinforced region of the spar. The lower ribbons ran from the spars to the lower fuselage. They offered less air resistance and also provided a way to measure wing loads in flight.^[1]^[2]

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).

The leading edge is the part of the wing that first contacts the air; alternatively it is the foremost edge of an airfoil section. The first is an aerodynamic definition, the second a structural one. As an example of the distinction, during a tailslide, from an aerodynamic point of view, the trailing edge becomes the leading edge and vice versa but from a structural point of view the leading edge remains unchanged.

The wing root is the part of the wing on a fixed-wing aircraft or winged-spaceship that is closest to the fuselage. On a simple monoplane configuration, this is usually easy to identify. On parasol wing or multiple boom aircraft, the wing may not have a clear root area.

The fuselage was a ply-covered semi-monocoque structure with an oval cross-section. It was unusually wide and deep in the central section, tapering away strongly aft of the wings. This variation allowed an uncramped, enclosed pilot's cockpit ahead of the wing and a very generous cabin for the observer, with celluloid-paned underwing windows on each side and accessed via a port side door. The cabin also had a table which could be folded away to allow use of the dual flight controls under blind flying conditions. A sprung landing skid was mounted below.^[1]^[2]

Monocoque, also structural skin, is a structural system where loads are supported through an object's external skin, similar to an egg shell. The word monocoque is a French term for "single shell" or "single hull". First used in boats, a true monocoque carries both tensile and compressive forces within the skin and can be recognised by the absence of a load-carrying internal frame.

Celluloids are a class of compounds created from nitrocellulose and camphor, with added dyes and other agents. Generally considered the first thermoplastic, it was first created as Parkesine in 1856 and as Xylonite in 1869, before being registered as Celluloid in 1870. Celluloid is easily molded and shaped, and it was first widely used as an ivory replacement.

The empennage was conventional, with a cantilever, tapered tailplane and elevators mounted on top of the fuselage^[1] and a fin carrying a full, rounded, deep, rudder hinged behind the elevators. The fixed surfaces were ply-covered and the control surfaces fabric-covered.^[2]

The empennage, also known as the tail or tail assembly, is a structure at the rear of an aircraft that provides stability during flight, in a way similar to the feathers on an arrow. The term derives from the French language word empenner which means "to feather an arrow". Most aircraft feature an empennage incorporating vertical and horizontal stabilising surfaces which stabilise the flight dynamics of yaw and pitch, as well as housing control surfaces.

A cantilever is a rigid structural element, such as a beam or a plate, anchored at one end to a support from which it protrudes; this connection could also be perpendicular to a flat, vertical surface such as a wall. Cantilevers can also be constructed with trusses or slabs. When subjected to a structural load, the cantilever carries the load to the support where it is forced against by a moment and shear stress.

A tailplane, also known as a horizontal stabiliser is a small lifting surface located on the tail (empennage) behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed-wing aircraft such as helicopters and gyroplanes. Not all fixed-wing aircraft have tailplanes. Canards, tailless and flying wing aircraft have no separate tailplane, while in V-tail aircraft the vertical stabiliser, rudder, and the tail-plane and elevator are combined to form two diagonal surfaces in a V layout.

Operational history

The ITS-VB's first flight was on 30 July 1935, piloted by its designer and towed by a RWD 8 from Lwów-Skniłów. This revealed aileron flutter and required aileron redesign, after which the glider was stable and handled well. It participated in the Third National Glider Contest held at Ustjanowa Górna in the autumn of 1935 and continued research flying until the start of World War II, based at Bezmiechowa Górna and mostly flown by Piotr Mynarski.^[1]

The RWD 8 was a Polish parasol monoplane trainer aircraft produced by RWD. It was used from 1934 to 1939 by the Polish Air Force and civilian aviation.

Ustjanowa Górna is a village in the administrative district of Gmina Ustrzyki Dolne, within Bieszczady County, Subcarpathian Voivodeship, in south-eastern Poland. It lies approximately 6 kilometres (4 mi) west of Ustrzyki Dolne and 79 km (49 mi) south-east of the regional capital Rzeszów.

Bezmiechowa Górna is a village in the administrative district of Gmina Lesko, within Lesko County, Subcarpathian Voivodeship, in south-eastern Poland. It lies approximately 7 kilometres (4 mi) north-east of Lesko and 65 km (40 mi) south-east of the regional capital Rzeszów.

Specifications (ITS-IVB)

Data from J. Cynk (1971)^[1] except where noted

General characteristics

Crew: Two
Length: 8.42 m (27 ft 7 in)
Wingspan: 20 m (65 ft 7 in)
Height: 2.2 m (7 ft 3 in) ^[2]
Wing area: 24.3 m² (262 sq ft)
Aspect ratio: 15.8
Airfoil: Göttingen Gö 655
Empty weight: 254 kg (560 lb)
Gross weight: 431 kg (950 lb)

Performance

Maximum glide ratio: 22.5 at 73 km/h (45 mph; 39 kn) best
Rate of sink: 0.82 m/s (161 ft/min) at 63 km/h (39 mph; 34 kn) minimum^[2]
Minimum speed: 48 km/h (30 mph; 26 kn)}^[2]

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References

1 2 3 4 5 6 7 Cynk, Jerzy (1971). Polish Aircraft 1893-1939 . London: Putnam Publishing. p. 700-2. ISBN 0 370 00085 4.
1 2 3 4 5 6 "ITS-IVb (ITS-IVb, 1935" . Retrieved 16 October 2018.

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[Cynk-1] 1 2 3 4 5 6 7 Cynk, Jerzy (1971). Polish Aircraft 1893-1939 . London: Putnam Publishing. p. 700-2. ISBN 0 370 00085 4.

[LOT-2] 1 2 3 4 5 6 "ITS-IVb (ITS-IVb, 1935" . Retrieved 16 October 2018.