Junkers Ju 287

https://en.wikipedia.org/wiki/Junkers_Ju_287

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.

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 forward of the main wing spar. 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.
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.


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

Flight tests began on 16 August 1944 (pilot: Siegfried Holzbaur), 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
inflight 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. 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, 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 RATO booster units, 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 evaluation 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, along with the two incomplete prototypes,
were taken to the Soviet Union. There, the third prototype (returned to its
original Junkers in-house designation, EF 131) was eventually finished 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)

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; 302 kn (347 mph) at 6,000 m (19,685 ft)
Cruise speed: 512 km/h; 276 kn (318 mph) at 7,000 m (22,966 ft)
Range: 1,570 km (976 mi; 848 nmi)
Service ceiling: 9,400 m (30,800 ft)
Rate of climb: 9.67 m/s (1,904 ft/min)




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