From: jfb@ihlpl.att.com (Joseph F Baugher)
Newsgroups: sci.military
Subject: Re: The German Technology
Summary: Junkers Ju 287 swept-forward bomber
Date: 29 Sep 92 13:07:38 GMT
Organization: AT&T Bell Laboratories -  Naperville, Illinois


From Joseph F Baugher <jfb@ihlpl.att.com>

In article <Buq5En.Jz4@lawday.DaytonOH.NCR.COM>, rlwst8+@pitt.edu (Robert L Williamson) writes:
> 
> I guess this is really more of a Luftwaffe question so here goes.  I read 
< a book on all of the major Luftwaffe planes during the second World War 
< (this book is huge...it has pictures for every plane too) and I saw a Junker 
< jet bomber that had a swept wing>  design.  My question is did the Germans 
< invent this design?     
> 

I think that you probably saw a picture of the swept-FORWARD Junkers Ju 
287, an experimental aircraft which first appeared in the summer of 
1944.  The book that you read was probably the excellent "Warplanes of 
the Third Reich" by William Green, which I cannot recommend too 
highly.  The following account is drawn largely from that book.  

Early in 1943, a Junkers design team lead by Dipl.-Ing.  Hans Wocke 
was assigned the task of developing a high-speed heavy bomber which 
could outrun any contemporary Allied fighter.  They first looked at a 
turbojet- powered swept-back wing design.  The swept-back wing offered 
advantages at the upper end of the performance envelope, but they were 
accompanied by disadvantages at low speeds.  As a sweptback-winged 
aircraft slows down, its wingtip stalls first, causing a loss of roll 
control just when you need it the most.  The Junkers team proposed a 
unique solution to this problem, a swept-FORWARD wing.  It was hoped 
that this wing would transfer the stability problems to the high-speed 
end of the performance envelope, where they could more easily be 
handled.  In theory, the swept-forward wing would have its highest 
lift coefficient at the root, decreasing towards the tip.  
Consequently, the tip would be the last to stall as the aircraft 
slowed down, aileron control being available beyond the main 
center-section flow breakaway.  

The downside of the swept-forward wing design is in its elastic 
behavior, specifically the phenomenon of "aeroelastic divergence".  As 
an airplane flies through the air, its wing is subjected to a 
more-or-less random twisting moment exerted by variable aerodynamic 
forces caused by rapid changes in wind currents or by rapid maneuvers.  
If the wing is swept forward, a small increase in the angle of attack 
at the tip will increase the lift, causing a twisting moment at the 
tip, which in turn will cause an increased angle of attack, which will 
cause still more lift, etc.  This causes the aircraft to become 
seriously unstable.  In the worst case, the wing can undergo a 
catastrophic structural failure.  This can make for a real bad day.  
:-) 

The Reichsluftfahrtministerium (State Ministry of Aviation, better 
known as the RLM) gave the project the go-ahead and assigned it the 
designation Ju 287.  The first prototype, the Ju 287 V1, was to be a 
flying testbed to check out the low-speed characteristics of the 
swept-forward wing.  In order to get something in the air as soon as 
possible, parts were scavenged from existing aircraft to the extent 
feasible.  The Ju 287 V1 used a fuselage from a He 177A bomber, a tail 
assembly from a Ju 388, and a massive fixed undercarriage consisting 
of Ju 352 mainwheels enclosed by large fairings and a pair of 
nosewheels scavenged from a B-24 Liberator.  Virtually only the 
swept-forward wing was new.  The wing used a Junkers reverse-camber, 
high speed airfoil section with a two-spar all-metal structure.  The 
inner leading edges were fitted with fixed slats to delay the initial 
root stall, and large slotted flaps were fitted which extended down to 
40 degrees.  The ailerons were arranged to droop 23 degrees to provide 
a completely cambered wing for maximum lift coefficients.  Power was 
provided by four 1984 lb.  st.  Junkers Jumo 004B turbojets, two 
mounted on the sides of the forward fuselage and two slung under the 
rear edges of the wings.  

The Ju 287 V1 flew for the first time on August 16, 1944.  Flight 
testing proceeded without any serious incidents, and the aircraft 
turned out to have rather pleasant flying characteristics.  There were 
virtually no trim changes with flap operation, and landings were 
fairly easy.  Lateral control was good except when yaw was applied, a 
pronounced wing drop then being experienced.  The aircraft reached 
speeds as high as 404 mph in a dive, and confirmed the aeroelastic 
problems inherent in the swept-forward wing, with decreasing elevator 
forces during tight turns and pull outs from shallow dives.  

Testing revealed that it would be a good idea to mount the engines on 
the forward edges of the wings in order to provide a mass balance, and 
this was to be done for the high-speed second prototype, the Ju 287 
V2.  The Ju 287 V3 was to be the production prototype with full 
military equipment being provided.  

The wing of the Ju 287 V2 was similar to that of the V1, but the 
fuselage was entirely different, being quite similar to that of the 
propeller-driven Ju 388.  A fully-retractable undercarriage was to be 
fitted, all members being stowed inside the fuselage.  Originally, the 
plane was to be powered by four 2866 lb. st. Heinkel-Hirth 011A 
turbojets mounted in pairs and projecting ahead of the wing leading 
edges.  However, owing to delays in the availability of this power 
plant, Junkers decided to power both the V2 and the V3 with six 1760 
lb. st. BMW 003A-1 turbojets.  Two different arrangements were to be 
tried, one with a cluster of three engines under each wing and the 
other with two engines underneath each wing and one on each side of 
the fuselage nose a la Ju 287 V1.  The former engine arrangement was 
to power the V2, whereas the V3 and the pre-production Ju 287A-0 were 
to be powered by the second engine arrangement.  

The V3 was to be the first prototype to carry armament--a tail 
barbette containing a pair of MG 131 machine guns operated remotely by 
a periscopic sight from the crew compartment.  The cockpit was fully 
pressurized.  A maximum bombload of 8800 lbs was envisaged.  It was 
anticipated that the V3 could achieve a maximum speed of 509 mph at 
sea level and 537 mph at 16,400 feet.  Range was expected to be 985 
miles with an 8800 lb bombload.  The V3 was expected to be able to 
attain an altitude of 19,700 feet in 10.5 minutes.  Weights were 
estimated to be 26,278 lbs empty, and 47,398 lbs fully loaded.  

The Ju 287 V2 was undergoing final assembly when the Junkers factory 
was overrun by Soviet forces in 1945.  The incomplete prototype, 
Dipl.-Ing Wocke, plus his design team, were all carted off to the 
Soviet Union.  The Junkers team continued to work on the project in 
the Soviet Union, and the Ju 287 V2 was flown for the first time in 
1947.  So far as I am aware, the Soviets did not exhibit any further 
interest in the project.  

Source: 

  Warplanes of the Third Reich, William Green, Doubleday, 1970.  

Joe Baugher       AT&T Bell Laboratories    2000 North Naperville Road 
		  Naperville, Illinois 60566-7033.   (708) 713-4548
Newsgroups: sci.military