DFS 346
DFS 346 | |
---|---|
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Aircraft 346-P | |
Role | Research aircraft |
Manufacturer | Siebel OKB-2 |
Designer | Felix Kracht |
First flight | 346-P in 1948 as glider 346-3 in 13.08 1951 with engine[1] |
Retired | 14 September 1951 |
Status | Project cancelled |
Primary user | Soviet Air Force
|
Number built | 4[2] |
Variants | Bisnovat 5 |
The DFS 346 (Samolyot 346) was a German rocket-powered swept-wing aircraft which began development during World War II in Germany. It was designed by Felix Kracht at the Deutsche Forschungsanstalt für Segelflug (DFS), the "German Institute for Sailplane Flight". A prototype was constructed but did not reach completion before the end of the war. It was taken to the Soviet Union where it was completed, tested and flown (with indifferent success).[3]
Design
The DFS-346 was a midwing design of all-metal construction. The front fuselage of the 346 was a body of rotation based on the NACA-Profile 0012-0,66-50. The middle part was approximately cylindrical and narrowed to the cut off to accommodate vertically arrayed nozzles in back. Probably for volume and weight reasons the DFS-346 was equipped with landing skids, both in the original German design and in the later Soviet prototypes; this caused trouble several times.
The wings had a 45° swept NACA 0012-0,55-1,25 profile of 12% thickness. The continuously varying profile shape caused a stall in certain flight conditions, which caused complete loss of control. This was later corrected by use of fences on the top of the wings.
Development
Concept
![](http://upload.wikimedia.org/wikipedia/en/thumb/7/72/DFS_228_cockpit_test.jpg/250px-DFS_228_cockpit_test.jpg)
The DFS 346 was a parallel project to the
Like its stablemate, it also featured a self-contained escape module for the pilot, a feature originally designed for the
The 346 design was intended to be air-launched from the back of a large mother ship aircraft for air launch, the carrier aircraft being the Dornier Do 217. After launch, the pilot would fire the 346's Walter 509B/C twin-chamber "cruiser" engine to accelerate to a proposed speed of Mach 2.6 and altitude of 30,500 meters (100,000 ft). This engine had two chambers — the main, upper Hauptofen combustion chamber as used on the earlier HWK 509A motor; but capable of just over two short tons (4,410 lbf) of thrust at full power (more at altitude), and the lower-thrust Marschofen throttleable chamber below the main unit of either 300 kg (B-version) or 400 kg (C-version) top thrust levels mounted beneath the main chamber. After reaching altitude, the speed could be maintained by short bursts of the lower Marschofen cruise chamber. The question of what rocket-motor subtype was to be used (the 509B or -C) is not adequately addressed here.
In an operational use the plane would then glide over England for a photo-reconnaissance run, descending as it flew but still at a high speed. After the run was complete the engine would be briefly turned on again, to raise the altitude for a long low-speed glide back to a base in Germany or northern France.
Prototype construction
Since the aircraft was to be of all-metal construction, the DFS lacked the facilities to build it and construction of the prototype was assigned to
Post-War
On 22 October 1946, the Soviet OKB-2 (Design Bureau 2), under the direction of Hans Rössing and Alexandr Bereznyak, was tasked with continuing its development. The captured DFS 346, now simply called "Samolyot 346" (samolyot "aircraft") to distance it from its German origins, was completed and tested in TsAGI
This solution was used on the majority of Soviet planes with swept wings of the 1950s and 1960s. In the meantime, the escape capsule system was tested from a
Operational use
In 1947, an entirely new 346 prototype was constructed, incorporating refinements suggested by the tests. This was designated 346-P ("P" for planer - "glider"). No provision was made for a powerplant, but ballast was added to simulate the weight of an engine and fuel. This was carried to altitude by a
First accidents
![](http://upload.wikimedia.org/wikipedia/commons/thumb/c/c3/346_ES.svg/150px-346_ES.svg.png)
Newly built 346-1 incorporated minor aerodynamic refinements over the 346-P, and was first flown by Ziese on September 30, 1948, with dummy engines installed. The glider was released at an altitude of 9700 m, and the pilot realised that he hardly could maintain control of the aircraft. Consequently, while attempting to land, he
The pilot seat structure and
The damaged 346-1 was later repaired and modified to 346-2 version. It was successfully flown by test pilot P. Kazmin in 1950-1951 winter, but nonetheless these flights also ended "on fuselage". Furthermore, after the last flight of these series, the airframe again required major repairs. On 10 May 1951, Ziese returned to the program, flying final unpowered test flights with the 346-2, and from 6 June, unpowered tests of the 346-3 without accidents.[4]
Final flights
By the mid-1951 346-3 was completed, and Ziese flew it under power for the first time on 13 August 1951, using only one of the engines. Continuing concerns about the aircraft's stability at high speeds had led to a VNE limit of Mach 0.9 being placed during test flights. Ziese flew it again on 2 September and 14 September. On this last flight, however, things went drastically wrong. Separating from the carrier plane at 9,300 meters (30,500 ft) above Lukovici airfield, the pilot fired the engine and accelerated to a speed of 900 km/h (560 mph). The rocket engine worked as expected, and 346-3, quickly accelerating, started ascending and soon had flown in very close proximity of its carrier aircraft.[4]
Ziese then reported that the plane was not responding to the controls, and was losing altitude. Ground control commanded him to bail out. He used the escape capsule to leave the stricken aircraft at 6,500 meters (21,000 ft) and landed safely by parachute. With the loss of this aircraft, the 346 program was abandoned.[4]
Variants
- DFS-346 - First prototype built by Siebel Werke in the early 1940s. Later taken to TsAGI wind tunnel. Later scrapped, because it was not flyable.
- 346-P - This airframe was first post-war build of this plane, and was completed in 1948 by German engineers. Visually 346-P was identical to the earlier design, excepting a landing gear cowl which was removed primarily for lightening the airframe. This prototype also featured mounted under wing supports, to help stop the plane when landed.
- 346-1(A) - On 5 May 1949, construction of 346-1 was finished. It had a rocket engine mock up installed, and incorporated some minor changes in the rudder and tail design.
- 346-2(D) - The same as 346-1, but the rocket engines fitted.
- 346-3 - Only plane that flew rocket-engine powered, and twice went transonic.
Specifications (346-3)
![](http://upload.wikimedia.org/wikipedia/commons/thumb/7/73/DFS-346-1.svg/300px-DFS-346-1.svg.png)
![](http://upload.wikimedia.org/wikipedia/commons/thumb/1/11/346_ST.svg/300px-346_ST.svg.png)
General characteristics
- Crew: one, pilot
- Length: 44 ft 1 in (13.45 m)
- Wingspan: 29 ft 6 in (9 m)
- Height: 11 ft 7 in (3.54 m)
- Wing area: 213 ft2 (19.9 m2)
- Airfoil: DFS 346#Design
- Empty weight: 4,806 lb (2,100 kg)
- Loaded weight: 11,506 lb (5,230 kg)
- Powerplant: 1× Walter HWK 109-509 rocket, 33.4 kN (7,500 lbf) 33.4 kN
Performance
- Never exceed speed: 2,765 km/h (estimated) (1,723 mph)
- Maximum speed: 900 km/h (verified) (560 mph)
- Service ceiling: 35,000 m (estimated) (114,800 ft)
- Rate of climb: 6,000 m/min (estimated) (19,680 ft/min)
See also
Related development
Related lists
- List of World War II military aircraft of Germany
- List of military aircraft of Germany
- List of rocket planes
- List of World War II Luftwaffe aircraft prototype projects
References
![](http://upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png)
- ^ Sultanov, I: "German Experimental Design Bureaus in USSR"
- ^ Aircraft construction history in USSR 1951-1965, 2002
- ^ Hallion, Richard, P. "The NACA, NASA, and the Supersonic-Hypersonic Frontier" (PDF). NASA. NASA Technical Reports Server. Retrieved 7 September 2011.
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: CS1 maint: multiple names: authors list (link) - ^ a b c d e Deutsche Flugzeuge in russischen und sowjetischen Diensten