During the war, Germany also employed the Focke-Wulf Fw-186 and experimented with the Focke-Achgelis Fa-225 and the two-seater Flettner Fl-184. But it was the Spanish design of the La Cierva C.30A that was most successful. The United States used a version which they named the Kellet KD-1A; Britain and Canada produced their own models as the Avro 671 Rota Mark.1 and the French called theirs the Lioré-et-Olivier LeO C.30/31. The Soviets had their own design, the TsAGI (Kamov) A-7 observation autogyro. In the Pacific arena, the Japanese produced their Kayaba Ka-1 Autogyro for reconnaissance and for use as an anti-submarine observation aircraft. Although the war brought helicopters visibly into use as a crucial means of transporting men and materiel, we should also remember the small, secret ‘spy in the sky’ that was the autogyro. Autogyros remain popular to the present day, mostly as the aircraft of hobbyists, yet they flourished only because of the pressures of secret weapons development in the war.
The flowering of innovation in the development of German secret weapons during the war years was especially pronounced in the field of revolutionary aeronautics. Britain was consumed with finding responses to the German onslaught, but the German High Command became fanatical about the domination of the Western world. The engineers and visionaries came up with startling, stunning concepts, and the rate at which they progressed was astonishing. Some of the ideas could never reach fulfilment. One was for the 3 x 1,000 project, intended to bomb English cities. This was the aim of Reichsmarschall Hermann Göring, and would have involved a bomber carrying 1,000kg of explosives for 1,000km at 1,000km/h, equivalent to 2,200lb of bombs for 625 miles at 625mph.
The birth of the ‘flying wing’ had been in the USA where Jack Northrop had experimented with delta-wing designs in the late 1920s. Little came of it, however, until the pressures of World War II led to new calls for revolutionary aircraft designs. Both the United States and Germany began development, but research took longer than expected. In Germany, two brilliant brothers, Walter and Reimar Horten, revived the concept during war and planned to take it to unprecedented heights. Both were members of the Hitler Youth and later of the Nazi Party. They first designed an unpowered delta-wing glider, the Ho-229, for flight testing, and its initial flight was in March 1944. After this successful test, the development was taken over by the Gothaer Waggonfabrik Company. They installed an ejector seat for the pilot, and added systems to carry air to the jet engine with which it was proposed to power the plane. Even before the aircraft had flown under jet power, Göring had an order placed for 40 of these aircraft with the designation Ho-229. Further test flights showed that the plane had superb handling qualities, though there were some tragic accidents during the test flights of prototypes. The Germans were building a twin-engined Ho-229 V3 when the Americans arrived during the liberation of Europe at the end of the war.
During the final stages of the conflict, the United States military initiated Operation Paperclip, a top-secret initiative by the United States intelligence agencies to capture advanced German weapons research, and keep it out of the hands of advancing Soviet troops. A Horten test glider, and the partly built Ho-229 V3, were packed up and shipped to the United States, and the Hortens — for all their active Nazi participation — were secretly taken to America and given sanctuary. Their hardware was sent to Jack Northrop.
The first of Jack Northrop’s new generation of planes, the N-1M, had taken to the air in July 1941 at Baker Dry Lake, California. These pioneering test flights showed that the design clearly had a future, though the plane’s twin 65hp (48kW) Lycoming 0-145 four-cylinder engines left it low on power and the construction was too heavy. The power-plants were replaced with 120hp (88kW) six-cylinder air-cooled Franklin engines and the design was modified though, in spite of it all, the plane never went into production.
Engineering design of the first American delta-winged planes started in 1942. The aircraft would be constructed of the latest light-alloy sheet. There would be a cabin embedded in the delta wing with bunk beds for crew to sleep on during prolonged flights. Bomb bays would be fitted in each wing with seven gun turrets carrying machine guns. Yet progress was slow and the XB-35 did not make her first successful flight until June 1946 when she flew from Hawthorne, California, to Muroc Dry Lake. By May 1948 the plane was ready to start production, but the planes — powered by propeller engines — were rendered obsolete by the advent of the jet bomber. Jet engines were fitted to a few but they were not successful, though one plane, designated the YRB-49A, was tested as a reconnaissance aircraft. Although the United States Air Force had originally ordered 200 of the original B-35 planes, they proved unsatisfactory and not worth converting to jet propulsion so the entire project was peremptorily cancelled. It was a controversial decision, and Jack Northrop later stated that it was due to his refusal to accede to the wishes of Secretary of the Air Force Stuart Symington, who wanted Northrop to merge with the Convair Company. Jack Northrop insisted that unfair terms were being imposed on him, and that it was Symington who suddenly cancelled the flying wing. Northrop may have been right; Symington subsequently became President of the Convair Company when he resigned from government service shortly afterwards.
The final legacy of the Horten brothers’ original design lives on, however. Their aircraft were intended not only to be aerodynamically efficient, but also to reduce the radar signature. As the British began to develop and improve radar technology, the Germans were increasingly aware of the need to defeat its penetrating gaze. The Hortens used a unique glue in their planes, rather than metal nails or rivets; the glue — a carbon composite — and the low profile meant that the aircraft were far harder to see on radar. In 2009, a full-size reproduction of the Ho-229 V3 was constructed for a television documentary. It cost $250,000 (£160,000) and took 2,500 hours to build, but its radar profile was found to be less than 40 per cent of a World War II fighter (such as the Messerschmitt Bf-109). Not only was this a revolution in design, but the plane, had it gone into production, would have been the world’s first stealth bomber.
An Olympic vision — the Adolphine
An aircraft with a greatly extended range had begun as an idea before the war and by the war’s end it was envisaged as a plane that could span the world from high altitude. It is a remarkable story of both brilliance and foolhardy adventurism that far out-reached itself.
This story had its roots in 1936 in Berlin, site of the XI Olympiad. The city selected to host the next Olympics was Tokyo, Japan, and Hitler had a vision that the German team would fly direct from Germany to Japan in a record-breaking non-stop flight aboard a futuristic aircraft designed especially for the event. As it happens, plans for the Olympics were agreed at the Cairo Conference of the International Olympic Committee held in 1938 but Japan renounced the conference because of the Second Sino-Japanese War. Japan was thus stripped of her right to hold the games, which were rescheduled to be held in Helsinki, Finland. By this time, the Germans were already developing the super-plane Hitler had envisaged: work had started in 1937, when the Messerschmitt Company launched Projekt P-1064. It was viewed as a development of the Messerschmitt Bf-110 twin-engined heavy fighter into a reconnaissance plane that had unprecedented range. Conceived with a slender fuselage and with two engines, this was the Messerschmitt Me-261 and it was seen as spearheading German superiority in long-range flight. The Luftwaffe designated it the 8-261. Since it had the backing of the Führer, the projected aircraft was named Adolphine.