Junkers Ju 287
| Ju 287 | |
|---|---|
| |
| Photo of a Ju-287 scale model | |
| Role | Bomber prototype |
| Manufacturer | Junkers |
| Designer | Philipp von Doepp |
| First flight | 8 August 1944 |
| Number built | 2 |
| Variants | OKB-1 EF 131 |
| Developed into | OKB-1 140 |
The Junkers Ju 287 was an aerodynamic testbed built in Nazi Germany to develop the technology required for a multi-engine jet bomber. It was powered by four Junkers Jumo 004 engines, featured a revolutionary forward-swept wing, and apart from the wing was assembled largely from components scavenged from other aircraft. It was one of the first jet propelled aircraft built with fixed landing gear.
The unfinished second and third prototypes, which far more accurately reflected the design of the eventual production bomber, were captured by the Red Army in the closing stages of World War II and the design was further developed in the Soviet Union after the end of the war as the basis for the two OKB-1 EF 131 airframes, and later developed by the Soviets into the OKB-1 140.
Development
The Ju 287 was intended to provide the Luftwaffe with a bomber that could avoid interception by outrunning enemy fighters. The swept-forward wing was suggested by the project's head designer, Dr. Hans Wocke as a way of providing extra lift at low airspeeds - necessary because of the poor responsiveness of early turbojets at the vulnerable times of takeoff and landing. A further structural advantage of the forward-swept wing was that it would allow for a single massive weapons bay in the best location, the centre of gravity of the plane, with the main wing spar passing behind the bomb bay. The same structural requirement meant the wing could then be located at the best aerodynamic location, the centre of fuselage. [1]Prior to the assembly of the first Ju 287, an He 177 A-5 (designated as a 177 prototype, V38) was modified at the Letov plant in Prague to examine the technical characteristics of this single large bomb bay design.
The first prototype was intended to evaluate the concept, and was assembled from the fuselage of an He 177 A-5, the tail of a Ju 388, main undercarriage from a Ju 352, and nosewheels taken from crashed B-24 Liberators, all of which were fixed to lower weight and complexity, and equipped with spats to reduce drag. The fixed undercarriage was used as the wing box couldnt have cutouts for wheel stowage which would reduce wing torsion box stiffness required for the forward sweep design. Later protoypes with higher power engines and higher top speed would have the undercarriage stowage in the centre fuselage sides[1] Two of the Jumo 004 engines were hung in nacelles (pods) under the wings, with the other two mounted in nacelles added to the sides of the forward fuselage.
Flight tests began on 16 August 1944 (pilot: Siegfried Holzbaur[2]), with the aircraft displaying extremely good handling characteristics, as well as revealing some of the problems of the forward-swept wing under some flight conditions. The most notable of these drawbacks was 'wing warping', or excessive in flight flexing of the main spar and wing assembly. Tests suggested that the warping problem would be eliminated by concentrating greater engine mass under the wings. This technical improvement would be incorporated in the subsequent prototypes with under wing engines moved forward under leading edge as a mass balance. [1] The 287 was intended to be powered by four Heinkel-Hirth HeS 011 engines, but because of the development problems experienced with that engine, the BMW 003 was selected in its place. The second and third prototypes, V2 and V3, were to have employed six of these engines, in a triple cluster under each wing. Both were to feature the all-new fuselage and tail design intended for the production bomber, the Ju 287A-1. V3 was to have served as the pre-production template, carrying defensive armament, a pressurised cockpit and full operational equipment.
Work on the Ju 287 programme, along with all other pending German bomber projects (including Junkers' other ongoing heavy bomber design, the piston-engined Ju 488) came to a halt in July 1944,[3] but Junkers was allowed to go forward with the flight testing regime on the V1 prototype. The wing section for the V2 had been completed by that time. Seventeen test flights were undertaken in total, which passed without notable incident. Minor problems, however, did arise with the turbojet engines and the equally-experimental HWK 109-501 higher-thrust (14.71 kN apiece) bipropellant Starthilfe RATO booster units,[4] which proved to be unreliable over sustained periods. This initial test phase was designed purely to assess the low-speed handling qualities of the forward-swept wing, but despite this the V1 was dived at full jet power on at least one occasion, attaining a speed in the medium dive-angle employed of 660kph. To gain data on airflow patterns, small woolen tufts were glued to the airframe and the "behavior" of these tufts during flight was captured by a cine camera mounted on a sturdy tripod directly ahead of the plane's tailfin. After the seventeenth and last flight in late autumn of 1944, the V1 was placed in storage and the Ju 287 programme came to what was then believed to be its end. However, in March 1945, for reasons that are not entirely clear, the 287 programme was restarted, with the RLM issuing a requirement for mass production of the jet bomber (100 airframes a month) as soon as possible. The V1 prototype was taken out of storage and transferred to the Luftwaffe's primary Erprobungsstelle evaluation and test centre at Rechlin, but was destroyed in an Allied bombing raid before it could take to the air again. Construction on the V2 and V3 prototypes was resumed at the Junkers factory near Leipzig, and intended future variant designs (meant for service in 1946) were dusted off. These included the Ju 287B-1, seeing a return to the original powerplant choice of four 1,300 kg (2,900 lb) thrust HeS 011 turbojets; and the B-2, which was to have employed two 3,500 kg (7,700 lb) thrust BMW 018 turbojets. While the Heinkel turbojet was in the pre-production phase at war's end, work on BMW's radical and massively powerful turbine engine never proceeded past three barely-tested prototypes. The final Ju 287 variant design to be mooted was a Mistel combination-plane ground attack version, comprising an unmanned explosives-packed "drone" 287 and a manned Me 262 fighter attached to the top of the bomber by a strut assembly. The cockpit of the 287 would be replaced by a massive impact-fused warhead. Takeoff and flight control of the combination would be under the direction of the 262's pilot. The 262 would disengage from the 287 drone as the Mistel neared its target, the pilot of the fighter remotely steering the 287 for the terminal phase of its strike mission.
The Junkers factory building the V2 and V3 was overrun by the Red Army in late April 1945; at that time, the V2 was 80% complete, and construction of the V3 had just begun. Wocke and his staff were captured by the Red Army and taken to the Soviet Union. There, the second prototype was eventually finished as the EF 131 and flown on 23 May 1947, but by that time, jet development had already overtaken the Ju 287. A final much-enlarged derivative, the EF 140, was tested in prototype form in 1949 but soon abandoned.
Specifications (Ju 287 V1)
Data from [5]
General characteristics
- Crew: two
- Length: 18.30 m (60 ft 0 in)
- Wingspan: 20.11 m (66 ft 0 in)
- Height: 4.70 m (15 ft 5 in)
- Wing area: 61 m2 (660 sq ft)
- Empty weight: 12,500 kg (27,558 lb)
- Gross weight: 20,000 kg (44,092 lb)
- Powerplant: 4 × Junkers Jumo 004B-1 turbojet engines, 8.825 kN (1,984 lbf) thrust each :::Ju 287 V2 and Ju 287 V3: 6 x Junkers Jumo 004B-1
Performance
- Maximum speed: 558 km/h (347 mph, 302 kn) at 6,000 m (19,685 ft)
- Cruise speed: 512 km/h (318 mph, 276 kn) at 7,000 m (22,966 ft)
- Range: 1,570 km (980 mi, 850 nmi)
- Service ceiling: 9,400 m (30,800 ft)
- Rate of climb: 9.67 m/s (1,904 ft/min)
See also
Related development
Related lists
References
Notes
- ^ a b c "Swept-Forward Bomber". Flying Review International. Vol 20, Number 4: 43–45. Jan 1965.
{{cite journal}}:|volume=has extra text (help) - ^ Wochenbericht der Erprobungsstelle Rechlin der Woche vom 6. bis zum 12. August 1944
- ^ Ford 2013, p. 224.
- ^ Krakow Polish Aviation Museum's page on the HWK 109-501 Starthilfe RATO pod
- ^ Green 1970, pp. 493–496.
Bibliography
- Ford, Roger. Germany's Secret Weapons of World War II. London, United Kingdom: Amber Books, 2013. ISBN 978-1-9091-6056-9.
- Green, William. Warplanes of the Third Reich. New York: Doubleday & Company Inc., 1970. ISBN 0-385-05782-2.
- Hitchcock, Thomas H. Junkers 287 (Monogram Close-Up 1). Acton, Massachusetts: Monogram Aviation Publications, 1974. ISBN 0-914144-01-4.
- Ransom, Stephen, Peter Korrell and Peter D. Evans.Junkers Ju 287. Hersham, UK: Ian Allan, 2008. ISBN 978-1-903223-92-5.
External links
