Forward, march …

One of the most unique aircraft configurations is the forward swept wing, which is only rarely seen and almost exclusively on jet aircraft.

First proposed in 1936 by German designers, the first use of this configuration was on the German four jet Junkers 287 jet bomber.

The original point of using the swept forward wing was not to improve performance at high speed, but to mount the wing box further back on the fuselage to clear the center fuselage for a large bomb bay.

The first Junkers 287, the V1 (Versuchs – test/research/prototype), had fixed landing gear and was pieced together from the fuselage of a Heinkel He 177, the tail of a Junkers Ju 388, main undercarriage from a Junkers Ju 352 and the nose wheels from a crashed American B-24 Liberator.

To add to its distinctly odd appearance, the Ju 287 had its four 1,984 pound thrust Jumo 004B engines mounted in unique locations – two engines on the trailing edge of the wing and two engines on the chin, just behind the cockpit on either side of the forward part of the fuselage.

Flight tests began in August 1944 and were basically satisfactory, but showed that the engines would be better mounted in a more conventional fashion on the forward part of the wing.

An entirely new Ju 287, the V2, was designed with no borrowed parts and six jet engines, clustered three each on a mounting on each wing. It was nearing completion in the spring of 1945 when Soviet forces captured the Junker complex and its facilities.

The Soviets had no jet bomber on the drawing board, just piston engine bombers re-engined with jet engines, so they were fascinated by the Ju 287.

They finished the second prototype with four 004B engines and flew it in 1946. The story goes that the Soviets gave the German crew insufficient fuel to escape and had a member of the Soviet national rugby team in the cockpit to keep an eye on them.

After the first flights, the entire project moved to the Soviet Union for more development, along with the chief designer, German professor Brunholff Baade. The design unit was called OKB-1.

In the USSR, Baade began work on a Soviet version of the Ju 287 called the Type 131. It only had two Lulko jet engines, Soviet versions of the British Rolls-Royce-Nene engines, with 7,055 pounds of thrust. The engines were in large nacelles attached to the underside of the wing.

The Type 131 was followed by a tactical jet bomber/reconnaissance aircraft, the EF-140, that used the same airframe with the classic Junkers style crew compartment in the nose. The wings swept forward about 20 degrees with marked dihedral and the under-slung engine nacelles extended forward off the leading-edge.

Defensive armament consisted of dorsal and ventral remotely controlled turrets armed with two 23 millimeter cannons each controlled by a gunner in the rear of the crew compartment.

Flight testing in the USSR began on May 23, 1947, under extreme pressure to get the aircraft ready to appear in the 1947 Aviation Day at Tushino airfield. But on the first flight, the main undercarriage collapsed and subsequent flight tests revealed major deficiencies, including tail surface vibration and severe problems with the engine fuel control units.

A new model, the 140-R, was developed. The engines were replaced by two fat Klimov VK-1 centrifugal flow turbo-jets, and flight testing commenced in October 1948. Four flights were carried out, but they all suffered from severe vibration of the wings.

This was the first appearance of the main problem with forward swept wings. At high speeds, or even maneuvering at moderate speeds, the wing tips tended to bend upward and cause the plane to stall. The state of metallurgy at the time meant the only way to fix it was to significantly reinforce the wing with a concomitant increase in weight and reduction in performance.

Given that aerodynamic benefits of the swept forward wing seemed minimal or nonexistent and the 140-R’s performance was not exceptional, on Aug. 23, 1948, the Soviet Ministry of Aircraft Industry terminated the program.

The swept forward wing concept continued to be highly impractical until the late 1970s, when it was found that new composite materials could be incorporated into the wings and eliminate the tendency of the wing tips to twist. It was also found that aircraft with forward-swept wings were highly maneuverable at transonic speeds and had advantages in terms of low-speed handling since tip stall problems disappeared because air flows over a forward-swept wing and toward the fuselage, rather than away from it.

However, this forward sweep also had serious stability problems and was generally impossible to use until the introduction of fly-by-wire systems that could react quickly enough to damp out these instabilities. It was in the late 1970s when Grumman, using fly-by-wire and parts from several different aircraft (shades of the Ju-287), developed an experimental forward sweep lightweight airplane called the X-29.

But today, fly-by-wire has made a variety of wings possible and forward sweep wings are rarely seen in the pure form, except in a few gliders and business jets where the original concept, the clearing of the main fuselage, is important.

Dr. Michel is currently deployed downrange.