OKB-2 346

OKB-2 346
Photo of a 1:72 scale model
Type:	experimental high-speed aircraft
Design country:	German Empire Soviet Union
Manufacturer:	DFS / OKB-2
First flight:	September 30, 1949
Production time:	1946-1950
Number of pieces:	3

The DFS 346 was a German and later Soviet experimental rocket-propelled high-speed aircraft, which was designed by Felix Kracht at DFS during World War II as a further development of a reconnaissance aircraft idea.

At the end of the Second World War, the half-finished machine was captured by the Soviet Union , where it was completed and flown.

history

The DFS 346 was a parallel project to the DFS 228 , a glider for extreme altitudes. The DFS 346 was extremely aerodynamic and streamlined. The designers hoped to break the sound barrier in this way. The machine contained an escape pod for the pilot, which was derived from the pre-war machine DFS 54 . As in the DFS 228, the pilot was lying on his stomach in the cockpit.

The plans envisaged a take-off from a carrier aircraft. The Germans had planned the Dornier Do 217 for this. After take-off, two Walter 509B engines should accelerate the aircraft to Mach 2.6 and heights of 30,500 m and the aircraft should glide to its target area. After completing its reconnaissance mission, it should accelerate again and gain altitude, ultimately returning to its base as a glider.

DFS 346 rescue system

The plane was to be manufactured as an all-metal mid - decker at Siebel in Schkeuditz , but it was no longer done because the war ended. Only the design and production documents were captured after the American occupation of the plant. After the factory had been handed over to the Soviet troops, the OKB-3 experimental design office, which was specially formed for this purpose, was commissioned to continue development on October 22, 1946, under the management of Heinz Roessing and Alexander Beresnjak . The aircraft was completed as the 346-P (also referred to as DFS 301 according to other sources) and transferred to the Soviet Union in October 1946 as part of the Ossawakim campaign, including the associated specialist group, where it was tested in the ZAGI wind tunnel ; it revealed some aerodynamic weaknesses. The rescue system was tested on a North American B-25 in 1947 and found to be suitable.

In 1947, the wind tunnel tests were so far completed that the development department, now called OKB-2, was working on testing the 346-P as a pure glider without a drive. However, ballast was used to simulate the weight of the engine and fuel. The machine was mounted under a B-29 Superfortress , which had made an emergency landing in the USSR after a bombing raid on Japan and was not returned to the USA, and was flown by Wolfgang Ziese in a series of tests from Tjoply Stan airfield . This led to two further prototypes, the first 346-I with small aerodynamic improvements and two HWK 109-510 engines being completed in 1948. The first flight took place on September 30, 1949 and was again operated by Ziese. As previously practiced, the aircraft was towed to altitude with the B-29, disengaged at 9700 meters and controlled in gliding flight. Because control problems arose, Ziese made an immediate landing, but the skid did not lock after it was extended and was pushed back into the shaft when it touched down, so that the 346-I slid across the runway on its stomach. Ziese was thrown forward by the braking forces and suffered injuries to his head on impact, which forced him to take a break from testing. The aircraft, which was only slightly damaged, was repaired and the Soviet test pilot Pyotr Kasmin continued testing the 346-I from November, whereby the same problem of improperly locking landing skids and subsequent belly landing occurred on his first flight, the cause of which was resolved over the entire following year 1950 moved there. The glider trials were continued with both the 346-P and the 346-I . At the same time, another prototype called the 346-III was created . This was also equipped with two engines, but had modified wings, which were equipped with a different profile and boundary layer fences based on wind tunnel knowledge . At the beginning of 1951, Tjoply Stan relocated the entire project to the Luchowizy airfield , where the now convalescent Wolfgang Ziese resumed the tests with a first glide flight on April 6 with the 346-III . On May 10, 1951, Ziese flew the 346-I again without propulsion.

The first flight with activated rocket propulsion took place on August 15, 1951 with the 346-III , but only one engine was ignited. Apart from the already known problems with lateral stability, it went without complications. A second followed on September 2nd. The ignition of both drives was planned for the third. On September 14, 1951, Ziese was thrown from the B-29 with the 346-III at 9,300 meters and activated the engines at 8,500 meters. The aircraft went into a steep climb with steadily increasing speed. At an altitude of 12,000 meters, it reached 950 km / h. There the machine got into the transonic area, where, according to Ziese, it was rudderless and went into a steep dive. After unsuccessful attempts to bring the machine under control, Ziese received the instruction to leave the aircraft and finally activated the rescue system at an altitude of 6,500 m, which worked without any problems. The machine was completely destroyed in the impact, but not the recording container on board, the so-called measuring barrel behind the pilot's cabin. The evaluation of the instruments inside revealed a sudden increase in speed of 280 km / h at 11,200 meters at 950 km / h, which may have led to the overloading of the structure and the subsequent loss of control. The effect probably arose when the aircraft suddenly got into the jet stream, the presence of which was not yet known at the time, against its direction of flow. After the crash, the program was discontinued.

Technical specifications

Three-sided view of the DFS 346-I

Longitudinal section through the 346-III

Parameter	Data (OKB-2 346-III)
crew	a pilot
length	13.75 m
span	9.00 m
height	3.54 m
Wing area	19.9 m²
Empty mass	k. A.
Takeoff mass	5,230 kg
drive	Walter HWK 109-509 with 33.4 kN
Top speed	2,765 km / h (planned), reached 950 km / h
Range	1,223 km
Service ceiling	30,500 m (planned)

literature

• Horst Lommel: Siebel / DFS 346. The world's first supersonic research aircraft . In: Aviation History . No. 17 . Lautec, Siegen.
• Horst Lommel: Junkers Ju 287. The world's first jet bomber and other swept wing projects . Aviatic, Oberhaching 2003, ISBN 3-925505-74-1 .
• Dimitri Alexejewitsch Sobolew: German traces in Soviet aviation history. The participation of German companies and professionals in aviation development in the USSR . Mittler, Hamburg, Berlin, Bonn 2000, ISBN 3-8132-0675-0 .
• Joachim Dressel, Manfred Griehl: The German rocket planes 1935-1945. The development of a revolutionary technique . Weltbild, Augsburg 1995, ISBN 3-89350-692-6 (licensed edition).

Web links

Commons : DFS 346  - Collection of Images, Videos and Audio Files

• DFS 346 at Luftarchiv.de
• DFS 346 at 48specialmodels.de

Individual evidence

1. ↑ Bart Hendrikx, Bert Vis: Energiya-Buran The Soviet Space Shuttle , Springer Science & Business Media, 2007, Post-War Rocket Planes, page 11, ISBN 978-0-387-69848-9
2. ^ Dressel, Griehl: rocket planes. P. 90.