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The Junkers Ju-288 suffered from unrealistic specifications and overly complex design.

Junkers’ Engineering Overkill

By Robert Guttman
10/23/2017 • Aviation History Magazine

Germany’s “Bomber B” program probably contributed more to victory than any other Luftwaffe project—Allied victory, that is.

The Germans have long been known for their engineering genius, but it could sometimes be carried to counterproductive extremes. Such was the case  with the “Bomber B” program initiated in July 1939, an extremely ambitious project to replace the medium bomber types then in Luftwaffe service. The Bomber B was to offer considerably higher speed and altitude performance, as well as more formidable offensive and defensive armament. The two leading contenders were the Focke-Wulf Fw-191 and Junkers Ju-288. Both were extremely advanced in concept, featuring pressurized crew compartments for high-altitude operations and remotely controlled defensive armament. And both were hamstrung by overly complex engineering.

The otherwise-promising Fw-191 was handicapped from the outset by the insistence of the German air ministry (Reichsluftfahrtministerium, or RLM) on two fatal criteria: that it be powered by only two engines, and that it be designed to have every conceivable function operated electrically. As a result, the bomber was encumbered with hundreds of pounds of servo motors and wiring. What’s more, the Junkers Jumo 222 power plants the airplane was designed to use never materialized, so the prototype had to make do with a pair of considerably less powerful engines. Inevitably the bomber turned out to be overweight and underpowered.

Focke-Wulf proposed a simplified version, with more suitable hydraulic and pneumatic systems and four engines instead of two. It was a solution not dissimilar to the one employed by Britain’s A.V. Roe, which salvaged its ill-starred twin-engine Manchester bomber by turning it into the highly successful four-engine Lancaster. Unlike the British Air Ministry, however, the RLM refused to accept such a straightforward engineering solution. Instead it simply canceled the project.

Part of the reason for the Fw-191’s cancellation was that the German high command favored the Junkers design. In the end, however, the Ju-288 degenerated into an even greater technological quagmire than its Focke-Wulf rival. Bearing no resemblance to its predecessor, the famously versatile Ju-88, the Ju-288 was to be a fast high-altitude bomber, but also function equally well in such varied roles as torpedo bomber, dive bomber and photoreconnaissance platform.

Like the Fw-191, the Ju-288 was designed to be powered by a pair of 2,500-hp Jumo 222 engines, a type that had yet to be perfected, let alone enter production. The bomber’s three crewmen were housed in a compact, pressurized capsule in the nose, where they were expected to perform multiple tasks: piloting, bomb aiming, navigation, radio communications and air defense. The 39-inch-wide compartment into which they were shoehorned made the infamously cramped cockpit of Handley Page’s Hampton bomber seem positively spacious by comparison.

The first Ju-288 prototype flew on November 29, 1940. Since the Jumo 222s were not yet available, it was fitted with lower-powered BMW 801 air-cooled radials, similar to those used on the Fw-190. The underpowered prototype was destroyed in a crash-landing brought about by an engine fire, the first of many such mishaps that would plague its successors.

As if the engine problems weren’t serious enough, the Ju-288’s landing gear proved— literally—to be another chronic weakness. Several prototypes came to grief when their undercarriages collapsed upon landing.

It wasn’t until 1942, several prototypes later, that a pair of Jumo 222s finally became available for flight-testing. The water-cooled engine boasted six banks of four cylinders per bank, arranged in the form of a hexagon around a common crankshaft. In front of the power plant was a large annular radiator, concealed behind an equally large ducted propeller spinner that reduced drag but also promoted overheating. Despite its great promise, the extremely complex Jumo 222 never proved to be very reliable—but Junkers never gave up trying to perfect it. By the time the manufacturer finally managed to get the bugs out, it was too late. Only 289 of the engines were ever completed, and none was installed in a production aircraft.

Once again rejecting the simple expedient of redesigning the bomber’s wings to incorporate four engines in individual nacelles, the RLM came up with a different engine solution in the form of the Daimler-Benz DB 606, which was almost as unsatisfactory as the Jumo 222. The DB 606 consisted of a pair of V-12 liquid-cooled DB 601 engines, the type installed in the Messerschmitt Me-109E, coupled together onto a common driveshaft. It offered nearly as much power as the perfected Jumo 222, but weighed half a ton more. The DB 606 was already in use in the infamous Heinkel He-177 heavy bomber, with which it had established a reputation for mechanical problems, maintenance headaches and inflight engine fires.

In the United States, the Allison Engine Company came up with a somewhat similar power plant at roughly the same time as Daimler-Benz. It coupled two of its V-1710 engines—the liquid-cooled V-12 installed in the Army Air Forces’ P-38, P-39, P-40 and P-51 fighters—into the monstrous 24-cylinder V-3420. Unlike the Germans, however, the Americans realized the impracticality of installing such a massive, complicated engine in a frontline combat plane, regardless of its power output, and terminated the program.

Despite the Ju-288’s power problems, the RLM and the Junkers engineering staff persisted with efforts to refine it. Apparently conceding the inefficiency of the three-man crew crammed into the narrow confines of the Ju-288’s pressurized cabin, Junkers redesigned it with a larger and more spacious compartment that had room for four. Wider than the rest of the fuselage, the bulbous new nose compartment made the bomber look somewhat like a flying tadpole.

In addition to installing three different types of engines and two different crew cabins, the Ju-288 project went through three different fuselages, two sets of tail surfaces and three entirely different wing designs. There were also a variety of arrangements for defensive and offensive armament. Each of the 22 flying prototypes was different, and none was ever judged entirely satisfactory.

Undoubtedly the most bizarre of the many permutations proposed for the Ju-288 was an anti-shipping version. Possibly learning about the successes the USAAF had achieved attacking Japanese ships with North American B-25 Mitchell medium bombers armed with a 75mm cannon, the Germans proposed a similarly armed version of the Ju-288. The Germans, however, intended their ship-killer to pack nothing less than a 14-inch single-shot recoilless cannon. The idea was that the pilot would execute a diving attack and fire his battleship-sized shell through the armored decks of Allied warships. That version of the Ju-288 was never built, so no Luftwaffe aircrew was ever called upon to try it out.

After the expenditure of 84 million Reichsmarks—the most expensive aircraft development program undertaken by Germany during the war—and untold man-hours, the Ju-288 project was finally terminated in mid- 1944. By that time the Luftwaffe finally realized that Germany needed defensive fighters more than it needed offensive bombers. Moreover, by then the Luftwaffe had developed the world’s first jet-powered combat airplanes, including Junkers’ own four-jet Ju-287 bomber, making any version of the Ju-288 that could ever achieve production already obsolete.

In many ways the Ju-288 was analogous to the much larger American Boeing B-29. Both airplanes were highly advanced and innovative, incorporating cutting-edge technology in the design of their pressurized cabins, engines and remotely controlled defensive armament systems. Unlike the B-29, however, the Ju-288 program was never able to produce a viable production aircraft. In terms of the German war effort, the Ju-288’s failure was as great as if all the time, money and effort expended by Boeing and the USAAF had failed to produce the superbomber capable of bombing Japan into submission.

Considered objectively, the entire Bomber B program in general, and particularly the Ju-288, made a far greater contribution to the Allied cause than to the Nazi war effort. It did so by virtue of the vast amount of resources the project absorbed, which could otherwise have been put to more effective use. After spending five years, countless man-hours and vast sums of money on the project, all the Luftwaffe had to show for its trouble was 22 unsatisfactory prototypes, a handful of which briefly flew reconnaissance missions on the Eastern Front.

 

Originally published in the September 2011 issue of Aviation History. To subscribe, click here

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