by Brian Ford
The Natter
In August 1944 the Chief of Development for the German Air Ministry (Reichsluftfahrtministerium), Colonel Siegfried Knemayer, was asked for new proposals for a hard-hitting plane that would be difficult to disable, and he listed the criteria that such an aircraft should satisfy. The result was the Natter. Knemayer decided to take a cheap rocket-powered aircraft that could fly near the speed of sound, fit it with armaments, and blast it from a vertical launch to attack enemy planes. A full set of control surfaces and landing gear would not be necessary, as the pilot would simply bail out and return to earth by parachute as soon as the attack was over.
Work began at the Bachem-Werke in Waldensee in 1944 and the result was the Ba-349 Natter, which translates as Adder or Viper. This was destined to become one of the oddities of World War II. It was intended to bring down the formations of Allied bombers that were relentlessly pounding German factories and cities in the latter years of the war. The Ba-349 followed a simple design that even semi-skilled workers could construct in less than 1,000 hours. The control surfaces were confined to the tail fins, making it easy to fly and simple to manufacture. It was powered by a Walter 109-509A rocket motor generating 3,700lb (1,700kg) of thrust and was equipped with 4 Schmidding 109–533 solid-fuel booster rockets fixed to the fuselage to assist the launch. Fully laden, the Natter weighed 4,800lb (2,177kg) of which 1,400lb (635kg) was fuel. The plane measured 21ft 3in (6.5m) in overall length and was fitted with two sets of 12 solid-fuel 2.84in (73mm) rockets to be fired in a single volley.
Flight testing of unpowered prototypes began in November 1944 at Neuburg an der Donau. The first was towed up to nearly 10,000ft (3,000m) by a Heinkel He-111 bomber and the test pilot, Erich Klöckner, reported that it handled well. In December 1944 vertical take-off tests were started at Truppenübungsplatz near Lager Heuberg yet the first manned flight in March 1945 soon ran into difficulties and the pilot, Lothar Sieber, was killed when his parachute failed to open. Problems were experienced from the start; even with the rocket boosters the velocity of the Natter when launched was too low for the control fins to work effectively, so steel vanes were fitted to deflect the rocket exhaust. They were prone to melting in the heat, so they were filled with water; although the water soon boiled away and the vanes were destroyed by the temperature of the rocket fame, the Natter had — by that time — gained enough speed to be conventionally controlled.
As the war was ending, the factory was closed down and a Dutch designer named Botheder was dispatched to take four of the Natters to a new base. Botheder was reported to have a ski chalet, the Einen Achalpe, in the nearby mountains and it was apparently agreed that this is where the teams would rendezvous after the troubles were over. In the event, he was intercepted en route to this eagle’s lair by advancing American forces in May 1945 and the truth was out. Botheder explained that the remaining staff members were a test pilot named Zeubert, who had successfully flown an unpowered gliding version of the prototype, an engineer called Granzow, who was in charge of the rocket motor, and a coordinator who kept a watchful eye on the proceedings. This man’s name was Schaller, and Botheder said he was convinced he was a Nazi party member put there to report back, secretly, on everything that was happening.
In total, 36 Natters were constructed during the war. Of these, 18 were used as test vehicles and two were destroyed in crashes. Ten were destroyed at the end of the war. One Natter was taken by the British, and another by the Soviet Army. Four of the surviving Natter rocket planes were taken back to the United States. One of these was test-fired, unmanned, from the Muroc Army Air Base in 1946. It was the first manned surface-to-air interceptor. Only three of the Natters have survived. There is a Ba-349A at the Deutsches Museum in Munich, now painted in the markings of one of the unmanned test aircraft. A second Natter is in the collections of the National Air & Space Museum in Washington DC. There is also a Ba-349A on show at the Planes of Fame Museum in Chino, California; this one, however, is only a wooden copy. In Japan during the last days of the Pacific War, the Mizuno aircraft company began constructing an aircraft that was based on the concept of the Natter. The Mizuno Shinryu interceptor rocket plane was the result. It would have been equipped with rockets fired from under its wings and could also have been fitted with a warhead in the nose, to be used for a suicide attack. Development was still underway at the end of the war.
And this provides us with a fascinating thought. The rate at which these new designs were realized seems extraordinary in a modern world, hide-bound by administration, bureaucracy, health and safety directives and the need to comply with regulations. From the viewpoint of wartime Germany, work began too late. Had the Axis powers begun work on their secret weapons earlier, many of these extraordinary innovations would have been proved a success and the course of the war might have turned out very differently.
PEACETIME DESIGNS IN WAR
Many of the secretly designed planes of World War II came from more conventional sources. For example, the Heinkel He-111 had been developed in peacetime in direct defiance of the Treaty of Versailles. Although claimed to be a commercial transport aircraft it had been covertly designed for easy conversion to military purposes. It became the Luftwaffe’s standard twin-engined bomber and was produced in scores of different variations. Typical of the type were planes with a wingspan of 82ft (25m) and length of 52ft 6in (16m), with an operating speed of 280mph (450km/h). In 1940, 750 of the planes were under construction; the number doubled during 1942, with the result that this bomber was produced in greater numbers than any other German plane during the early years of the war. It took part in the Battle of Britain, but the superiority of the British fighters proved that its time had passed. It had poor manoeuvrability, limited operating speed, and its armaments were inferior. However, it could often remain flying even when badly damaged and so was eventually employed on many fronts during the war. As well as serving as a bomber it was useful as a transport aircraft on the Eastern, Western, Mediterranean, Middle East and North African Fronts, and was successfully used to drop torpedoes in the North Atlantic campaign. As the war ended, the He-111 re-emerged in a different guise, ensuring the design remained in use for many years. It was produced in Spain under licence by Construcciones Aeronáuticas SA, and the first of these planes flew before the war ended in May 1945. After the war, since it was no longer possible for the manufacturers to obtain the Junkers engines, they installed the Rolls-Royce Merlin 500 instead. Over 170 Merlin engines were ordered in 1953 alone. A nine-passenger transport aircraft, the 2.111T8, was to follow. Many of these planes found a use in movies about World War II, repainted to look like the original Heinkels. The Spanish planes continued in daily use until they were finally withdrawn from service in 1973.
The strangest version of the He-111 was the top-secret heavy-duty version designed to tow gliders filled with tanks, artillery and troops. It was manufactured as a pair of conjoined He-111 aircraft with a common wing upon which a fifth engine was mounted. The entire wingspan was some 125ft (38m) and the pilot flew the plane from a cockpit in the left-hand fuselage using identical, linked control levers. Towing a glider of over 35 tons, this twin aircraft was said to have flown to 30,000ft (9,100m) in 1942. The large numbers of these vast tow-trucks that would have been necessary for large-scale invasions were never produced. Certainly the handling and aerodynamics of this bastard giant would have been intimidating at the very least.
Following the success of the He-111 came the He-115, a seaplane comparable to the Sunderland Flying Boat that was produced in large numbers by the British. The He-116 was designed for long-distance cargo transportation and was used for flights to Japan; the He-117 and He-118 were tactical developments that never got off the ground and the He-119 — which could travel up to 375mph (600km/h) and was to be powered by two DB-603 engines — was never put into production.
A revolutionary high-altitude bomber was proposed as the He-274, intended to be a four-engined bomber with a number of advanced features. Development began in
October 1941 and the prototypes of the new bomber were contracted for construction in France by the Société Anonyme des Usines Farman (SAUF) firm in Suresnes, near Paris. The He-274 dispensed with twin coupled engines and instead featured four independent DB-603 A-2 engines with a greater wingspan and a lengthened fuselage. The cockpit would be double-glazed and pressurized to maintain an air pressure for the crew equivalent to an altitude of 8,200ft (2,500m). The aircraft was designed to fly up to 47,000ft (14,300m), far higher than any Allied fighter. In 1937 a Bristol Type 138 high altitude monoplane had reached a world record altitude of 49,967ft (15,230m) but this was an experimental aircraft; the highest a Spitfire XIX ever flew was 44,000ft (13,400m).
As a consequence, the He-274 would require little defensive armament and the plane was designed to carry a forward-firing 13mm (0.51in) MG 131 machine gun with a further two pairs of these guns in turrets. Work on manufacture of the prototypes did not start until 1943 and the advance of Allied forces on Paris in July 1944 forced the evacuation of the German employees before the first flight had taken place. Here too, the German technology pointed to the future. After the war, the French Air Force (Armée de l’Air) finished building the first He-274 and renamed it the AAS-01A. The second prototype was flown in December 1947 AAS-01B. Both were employed as test-bed mother ships for the launch of rockets and advanced jet planes at high altitude, and were in use until they were broken up at the end of 1953.
Birth of jet planes
These amazing aircraft clearly show that Ernst Heinkel was a leading innovator on many fronts, and the best example of this is the introduction of the jet fighter. Jet-propelled planes could have radically altered the course of the war, but they arrived on the scene too late to make a crucial difference. The origin of the aircraft jet engine dates back to July 1926, when a young British engineer named A. A. Griffith published a paper on jet turbines. The idea was followed up by Frank Whittle, then an enthusiastic Royal Air Force (RAF) recruit, but Griffith dismissed the idea of a jet plane since he was convinced that a turbine could never generate the efficiencies needed for flight. Undeterred, in January 1930 Whittle took out a patent for the first jet engine. It attracted little interest with the RAF and they placed no restrictions upon the concept. Whittle made great progress as a pilot, and yet although companies showed some interest in his proposals for a jet plane none were willing to put up the money necessary to build a prototype.
During the following year, an Italian experimenter named Secondo Campini sent a paper on jet propulsion to the Italian Royal Air Force (Regia Aeronautica Italiana) and in 1932 he demonstrated a jet-propelled boat on the Venice lagoon. In 1934 he received the agreement of the Italian Royal Air Force for the development of a jet aircraft. Campini commissioned the Caproni factory to build his prototype. On 27 August 1940 test pilot Mario De Bernardi took the plane into the air and the World Air Sports Federation (Fédération Aéronautique Internationale) recognized this at the time as the first successful flight by a jet aeroplane, until news came of the Heinkel He-178 V1. This had flown for the first time in August 1939, powered by the HeS-3B engine invented by a German designer named Hans Joachim Pabst von Ohain. As we shall see, this highly innovative aircraft would give rise to a revolution in aircraft design — one we are still experiencing today.
However, the reality is that Campini’s aircraft did not have a jet turbine at all. His design featured a 670hp (500kW) Isotta Fraschini piston engine which drove an air compressor, forcing air into the combustion chamber where it mixed with a spray of fuel. Although the exhaust gases propelled the device forward, the use of a piston engine as the compressor means that it was not a jet turbine. Another Italian named Luigi Stipa also designed the Stipa-Caproni experimental aircraft in 1932, which had a ducted fan, and he also tried to claim it as the first jet aircraft. Both his plane and the Caproni-Campini used a jet of gas to propel the plane along, but neither was a pure jet turbine.
Meanwhile, in Britain, Whittle was still trying to develop his jet turbine idea, and in 1934 he was authorized to take the two-year engineering course at Peterhouse College, University of Cambridge, where he graduated with a first-class degree in Mechanical Sciences. Whittle received a note in the mail to remind him that his patent for a jet engine was due for renewal in January 1935. He could not afford the £5 fee. The Air Ministry told him that it was not interested in funding the renewal either, and so the patent lapsed. However, in September 1935 Whittle was introduced to two investment bankers at O. T. Falk & Partners, Sir Maurice Bonham-Carter and Lancelot Law Whyte. Whittle explained that a reciprocating engine, with its metallic components jerking up and down, seemed to him condemned to extinction. He insisted that the smooth-running jet turbine was obviously the way ahead. Whyte felt that this was a proposal of sheer genius, and in January 1936 Power Jets Ltd was formally established.
On 12 April 1937 the Whittle jet engine ran for the first time. It was a stunning success. There was a growing sense that the jet engine had immense promise, but not until March 1938 did the Air Ministry offer any funding. This funding proved to be a mixed blessing, for the project was now subject to Ministerial bureaucracy and the Official Secrets Act made it impossible to discuss the developments as widely as before. From being a topic of growing interest, it suddenly became a matter of the utmost secrecy. Nonetheless, work proceeded on constructing a prototype jet plane, the Gloster-Whittle E 28/39, and on 7 April 1941 near Gloucester the first few hops into the air were made. Whittle himself was at the controls, but had in fact been specifically ordered not to fly the plane as the Ministry did not wish to risk both the aircraft and its designer if anything went wrong. Whittle told the senior officers that he would just take out the plane for some taxi runs, which would warm up the engine; but he accelerated along the runway and (as he later said) ‘it just took off’. The next month, on 15 May, the first formal test flight took off from Cranwell at 7.40pm. The plane flew for 17 minutes at speeds of up to 340mph (545km/h). Days later, it was flying at 370mph (600km/h) up to 25,000ft (7,600m) which was better than anything a conventional fighter could achieve.
Meanwhile, under conditions of top secrecy, jet planes were already taking shape in Germany. In 1936, the gifted young engineer Hans Joachim Pabst von Ohain had taken out a patent for the use of the exhaust thrust from a gas turbine as a means of propulsion. This was six years behind Whittle’s original patent. Ohain presented his ideas to Heinkel, who agreed to help develop the concept. The prototype was speedily developed and built, and Ohain successfully demonstrated his first engine in 1937. It was powered by hydrogen gas which quickly burned through the components, and was extremely simple in design, but it proved that a jet turbine could run just five months after Whittle’s prototype engine. It is remarkable to think of these two gifted young men, each constructing and testing the first jet engines in the world, separately in England and Germany, and at the same time. Although Whittle had been unable to find finance for a year, plans were quickly made in Germany to construct one of these engines to power an aircraft.
Ohain had joined the staff of the Heinkel Company as a designer, and subsequent developments were rapid — in complete contrast to the lack of interest shown by the British authorities in Whittle’s earlier design. As Ohain’s first experimental jet engine had used hydrogen as fuel, it burned with too much heat and produced too little thrust to be operationally viable, so his designs for a more compact version were intended to burn conventional liquid fuels instead. The He-178 jet plane, the first to be designed in the world, was based on Ohain’s third design, the HeS-3, which now burned diesel fuel. All the flight tests were carried out under conditions of total secrecy and on 27 August 1939 the first flight of the Heinkel He-178, with Erich Warsitz at the controls, was successfully completed. The entire project had been privately conducted at the expense of Heinkels, and the test flight of the German plane was two years ahead of the British.
The aircraft was a small plane with a metal fuselage of conventional configuration
and construction. The jet intake was in the nose, and the plane was fitted with a tail-wheel undercarriage. The main landing gear was intended to be made retractable eventually, but was fixed in the down position throughout the flight trials. The plane proved the principle, but had a combat duration time of only 10 minutes so it was never going to be a production-line success. It inspired the design of the twin-jet He-280 which became the first prototype jet fighter in history. These remarkable designs were privately financed by Heinkels, as the German authorities were, much like the British, slow to be convinced of the merits of jet-propelled aircraft.
Although the fact is usually forgotten, the Russians were also developing a jet engine at this time. This was the brainchild of a relatively unknown engineering pioneer named Arkhip Lyulka from Kiev Oblast in Ukraine. Lyulka’s first interests were in turbofans as superchargers of piston engines on the Petlyakov Pe-8 bomber. Between 1939 and 1941 Lyulka worked on what was to become the first double-jet turbofan engine in the world, which he patented in April 1941. Work began on building a prototype fighter aircraft, but as the Nazis invaded Russia, Lyulka stopped his work and evacuated to the Ural mountains.
Heinkel realized that the time had come to convince the German High Command of the importance of the jet plane, and so in 1941 a contest flight was organized in Germany between a jet-powered He-280 and a propeller-driven Focke-Wulf Fw-190 fighter. The He-280 completed four laps of the course in less time than the Fw-190 could finish three. The jet plane was designed to be light, in order to match the relatively low thrust of the jet engines, it burned kerosene, instead of the more costly aviation spirit, and it had shown jet fighters to be a success. Yet the Nazis put their weight behind a rival design for a jet aircraft designed by Messerschmitt, the Me-262 Schwalbe (Swallow) or Sturmvogel (Stormbird). In July 1944 the Me-262 came into service. It is heralded as the world’s first jet fighter. In the same month the Gloster Meteor came into use, too; some people believe that the Meteor may have been in service several days before the Messerschmitt, in which case the British would take the claim. What is remarkable, however, is the astonishing synchronicity of the dates. We have seen that the German and British jet engines were being developed at exactly the same time and each nation had the first jet fighters ready at the same time. The ideas had progressed in Germany and in Britain at exactly the same rate. Which was the better plane? There is no question about that. The Me-262 was faster and better armed than the Gloster Meteor. The new British jet could fly at 410mph (660km/h) whereas the German Me-262 flew at 560mph (900km/h). The German jet fighters were an unquestionable success, and the German pilots would claim a total of over 500 Allied aircraft shot down for the loss of 100 Me-262 fighters. In contrast, the British jets were forbidden to fly near continental Europe, in case they were brought down and revealed design secrets to the enemy. Although they helped to intercept V-1 drones heading for London, they had little military impact. The Meteor did set a world airspeed record in November 1945 at Herne Bay in the UK, when Group Captain H. J. Wilson set the world’s first airspeed record by a jet aircraft. He flew a Meteor F Mk 4 at 606mph (975km/h). Macari’s Café, near the beach in Herne Bay, still has a small plaque on the wall to commemorate the event. The next year the record was raised to 616mph (991km/h), also by a Gloster Meteor.
