DAR (ДАР) long range reconnaissater by R.L.Bartini

In the 1933 famous polar pilot B.G.Chukhnovskij (Б.Г.Чухновский) came up with idea of the Polar "all-terrain" aircraft, capable to operate from water, ice and snow. Proposal received warm welcome at the High Offices, and B.G.Chukhnovskij was put in charge for the aircraft: he had to put together technical requirements, participate (as a practical pilot) in the design and organize the production. Aircraft was designated DAR according to it's supposed role: Long-Range Arctic Reconnaissater.

R&D took place at the NII GVF, chief designer R.L.Bartini. Assembly of prototype and following production - at ZOK NII GVF and Leningrad Shipyard.

R.L.Bartini remained loyal to his tradition - design was unique in many respects.

First of all, the proposed installation of the engines. Pair of Hispano-Suiza 12Ydrs were installed "face-to-face", driving coaxial propellers. Moreover, the wing was transformed into a ring forming a tunnel around the propellers. This was a first practical implementation of the so called "effect Bartini". Calculated by talented scientist and tested in the TsAGI, this effect is responsible for sharp increase of the propellers efficiency, sometimes called a negative drag. The tunnel also linked the wing to the aircraft fuselage.

Some sources mention that it is impossible to optimize the "effect Bartini" for wide range of speeds. But for the long-range reconnaissance plane which travels on the optimal cruising speed most of the time this restriction is not a problem.

Unfortunately, this installation "consumed" near 15m² of the wing area. Construction complicity and service inconvenience also resulted in rejection of this novelty. Today "effect Bartini" is used on propellers of high speed air cushion boats. Conventional back-to-back tandem with common chin radiator was installed on the strut-mounted parasol wing.

Wing of the DAR was similar to one of the Stal-6 - wielded stainless steel tubes and frames. Airfoil of the 10% thickness was calculated by R.L.Bartini himself. More than 3/4 of the wing span was occupied by very effective flaps. Two-section (tandem) floating ailerons on the very wing tip provided excellent handling despite of their small span. This unusual installation was never used again, but the airfoil (also designer's own) was re-used on other planes.

Stainless steel hull was of entirely-wielded type. The slightly corrugated thin skin (0.5mm, hull bottom up to 1.5mm) was wielded together and to the frame from inside, while held in place by numerous thick copper outer electrodes. Wielding was performed from inside, very quickly and with very good quality.

For ice/snow landing DAR used pair of pneumatic skis. Those skis (5m long, 0.32m wide) were fixed at the bottom of the hull. Inside each ski had five 1m rubber air chambers. Ski surface - 20mm plywood with 0.8mm stainless steel cover. Ski sides - thin Enerzh-6 corrugated steel walls. Air chambers made a perfect shock absorber, and ice landing was very soft and easy (tested on Dornier Wal in late 1935 and on DAR in Spring 1936).

DAR was assembled in the very end of 1935 and flown by B.G.Chukhnovskij in Spring 1936. Performance and handling were considered as good.

After the trials Glavsevmorput ordered batch of five aircraft for Arctic operations, but all works were scrapped after R.L.Bartini was arrested.

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Created November 09, 2001

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