Visitors to the variety displays held during the 1938 Berlin Motor Show might have been forgiven for believing that the vision of the future glimpsed in the films The Shape of Things to Come and Metropolis had already arrived as they watched twenty-six-year-old Flugkapitän – Flight Captain Hanna Reitsch flying the Focke-Wulf Fw-61 helicopter inside the Deutschlandhalle. Giving demonstrations each evening for the duration of the show, she whirled the machine around the vast space, making it dance and skip amid a blizzard of flashbulbs. The audacious displays were the world’s first glimpse at the possibilities offered by the helicopter.
Such a dramatic display of technological progress was unprecedented, and the Fw-61’s appearance struck fear into the hearts of more than a few conventional aeroplane makers. Here at last was a true helicopter, of a simple and robust design, that really worked. Across the Atlantic Ocean, in the USA, Igor Sikorsky’s experimental machine could still only hover for short periods of time while tethered, and was incapable of forward flight.
It was to be another six years before helicopters reached operational status with the Allied forces. Had luck been with their development in Germany, both the German Airforce and the Navy would have been using them widely from as early as 1940.
The story of early, rotary wing research in Germany involves a number of key figures – luminaries who could foresee applications beyond their own basic work in the field, and who knew the area was worth further investigation. We have to go back to pre-Great War Russia to find the very first true helicopter developments, aside from the fanciful work of da Vinci and Cayley. In 1904, Russian scientist Zhukovski published a study paper entitled Lifting Payloads by Turning Wings. His theory was that it might be possible for a series of rotating arms, each having the cross section of a wing aerofoil, and spun at high speed, to power a vertical take-off device. The basic principle of flight and the generation of lift requires that a wing be shaped with a slight curve in cross section on its upper surface and a flat underneath. Air passes more quickly over the upper curve and is at a lower pressure than the air beneath. This differential creates lift, so either the aircraft – or the wings on helicopter rotors – must be moving fast to get enough lift to take off.
Zhukovski’s theory inspired engineers of vision, such as Sikorsky and Yuryev, to begin tentative experiments. The Great War forced their deferral, but this was not before Yuryev had got his machine off the ground (in 1912) in a series of short hops. Yuryev’s was a remarkable achievement, especially when one looks at pictures of his craft today, for it is possible to recognise elements of the modern helicopter within its Heath Robinson frame. It had a large rotor mounted above the fuselage, together with a smaller stabilising rotor on the end of a tail boom, and thus set the pattern for all that would follow.
After the Great War, and at the time that the Treaty Of Versailles was still in force, German aircraft engineers began to investigate alternative forms of aeroplane building and propulsion in order to circumvent the restrictions they found themselves placed under by the treaty. It was not long before their efforts began to pay off, and one of the first to succeed, in 1927, was Anton Flettner. Flettner, a respected aerodynamics expert in the field of conventional aircraft, now turned to studying the helicopter. His first design had one single large rotor with a small, twenty horsepower petrol motor at the tip of each of its two blades. These little engines each powered a small airscrew that in turn kept the free spinning rotor turning, giving lift as a result. At one stage this most ungainly craft actually got airborne, but it was wrecked when a sudden gust of wind destabilised it, causing it to crash and be written off. Flettner was forced back to his drawing board, though the experience had provided valuable lessons that were to serve him well later.
Advent of The Autogyro
Meanwhile, the 1920s in Spain saw Juan de la Cierva quietly developing the concept of the autogyro, in which the main rotor is used not to propel the machine but solely to generate lift; a separate propeller, rear mounted or front mounted, is used for forward motion. Such was Cierva’s success with his idea that, following successful trials in Spain, he moved to Britain to continue his research. While there, he developed a definitive craft, the two seater C-19 gyroplane. Its layout resembled a conventional low winged monoplane, but with a shallow rear tail and shortened, stumpy wings with dihedral – upturned – tips. A four bladed main rotor was driven by a conventional radial piston aero engine which also powered a small, front mounted propeller.
Though not a true helicopter, the gyroplane came close to having a helicopter’s characteristic manoeuvrability. The fact that the design worked well and was fairly robust was a bonus, and was enough to attract many licensees. One of these was the German aero company Focke-Wulf, founded in Bremen in 1924 by the then thirty-four-year-old Heinrich Focke and his business partner, G. Wulf. The Focke-Wulf licence built version of Cierva’s gyroplane proved to be the starting point for some of the later helicopter designs seen in Germany. German manufacturers were being actively encouraged to develop such unorthodox machines, and it therefore came as no surprise when Cierva was courted by them. Professor Focke held the post of Technical Director of his company, and as soon as they had acquired the licence to produce the C-19 in 1931, he set about improving the original design. To do this he had established within Focke-Wulf a rotorwing research team, the core members of which were later to leave with him when he entered a new partnership and formed Focke-Achgelis.
The gyroplane Focke-Wulf produced, the Fw C-19, used a 150 horsepower Siebel Sh-14 engine, and was quickly nicknamed Don Quixote. It was swiftly followed by the C-30, which appeared in 1933. This version retained the Siebel engine, but dispensed with the vestigial wings, and for the first time the craft took on the appearance of helicopters familiar to us today.
Between 1937 and 1938, Focke developed the C-30 further and further away from its original Spanish design, finally creating the Fw-186 gyroplane. This was entered in a competition run by the Air Ministry to find a short takeoff and landing (STOL) reconnaissance aircraft. Its rivals were the conventional Siebel Si-201 and the Fieseler Fi-156 Storch – Stork which eventually won.
The design of the 186, however, while retaining the two open cockpits for the pilot and the observer, featured a much smoother and more streamlined fuselage, and the two front undercarriage wheels were mounted further outboard, on more substantial outriggers. The struts of the outriggers had curved profiles in order to minimise aerodynamic drag. Although it did not win the competition, its development showed what might be possible in rotor craft of all types.
The Air Ministry was not the only military body interested in looking at helicopters more closely. In 1934 and 1935 the Navy made known its requirement for a ship based reconnaissance aircraft, the specification for which could be met only by a true vertical take-off and landing (VTOL) machine, since no aircraft carriers had been built in Germany. The Navy’s requirement aroused interest within the aeroengineering community, for Focke’s Fw-186 fell into the STOL bracket and would thus be impracticable for ship use. Anton Flettner’s response was to organise a plant in Berlin in 1935 which was eventually to produce true helicopters for the Navy. He had produced his own first autogyro, the Fl-184, that same year, but had understood quickly that the machine could not fulfil the Navy’s specification, any more than Focke could with his Fw-186. And Flettner’s machine, even though it boasted a more comfortable enclosed two seater cockpit, was inferior to the Focke-Wulf gyroplanes then flying.
Flettner therefore turned his attention to the principles of pure helicopter flight, and soon afterwards, in 1936, he unveiled an ungainly machine that provided a partial answer – the Fl-185. This used a twin bladed rotor, at the end of each rotor was a motor, with a small propeller half way along its length. The Fl-185 succeeded in making only a series of unsteady hops, but Flettner had intended it only as a test bed for the real prototype, which was already in development – the Fl-265.
Focke-Wulf were making real progress, meanwhile, on their own new helicopter project, and their Fw-61 would soon stun the world. Flettner was undeterred and carried on working steadily with his two colleagues, Sissingh and Hohenemser, in developing new approaches to helicopter control and design. He published numerous research papers from 1936 onwards, and these would, much later, help companies like Sikorsky to devise the sophisticated machines that were used later in the Korean War.
In essence, Flettner’s Fl-265 involved the use of a pair of twin bladed rotors, each counter rotating against the other and using a shared hub. The machine seemed perfectly suited to naval requirements. The aerodynamic fuselage had fully enclosed seating for two; the now fully shrouded Siebel engine was mounted at the front, and used a similar cooling airscrew to that on the Focke-Wulf Fw-61. A complex, hand built gearbox for the two rotors was mounted above the cabin and faired into the roof of the upper fuselage. A large tail section was considered essential for stability, and fixed outrigger mounted landing gear completed the design. In all, five such machines were built, and they saw limited service and handling trials with the Navy aboard cruisers between 1939 and 1940. In that time the record of the Fl-265 was excellent: there was only one serious accident, and the craft displayed a manoeuvrability that made the cream of conventional aeroplanes at the time look clumsy by comparison. One test involved a mock attack by Messerschmitt fighters. Not only could the Messerschmitt fighters not find an advantageous position within the exercise, but the Fl-265’s nimble handling allowed it to gain the upper hand over them – which led some officials to consider using it as an alternative fighter and attack platform. Had such an idea been implemented, the Fl-265 would have become a formidable forerunner of the helicopter gunships of the Vietnam War.
The Navy was keen to develop the Fl-265 further, but Flettner was already working on its successor, the Fl-282 Kolibri – Hummingbird. Frustrated that the Fl-265 was not to be taken further, the Navy later worked with Focke-Achgelis. The new firm would become Flettner’s main rival, in developing the Fa-330 Bachstelze – Water Wagtail for use in submarines as a spotter of Allied convoys.
Flight of The Dragon
Ever since Heinrich Focke had taken out his licence to produce Cierva’s autogyro, he had been keen to move on to actual helicopters, and he had always seen the making, building, and flying of the gyroplane as necessary steps towards achieving true helicopter flight. The closely knit team he had assembled for the purpose had not only worked on autogyros, but, from the outset, had also secretly been engaged in developing helicopter designs. In June, 1936, they reaped their first rewards with the maiden untethered flight of the Fw-61.
Photograph taken at the 1938 Reich Party Day
This flight was the result of work begun in 1934. Then, using a standard Fw-44 trainer aircraft (used to familiarise new pilots to flight) as their starting point, Focke and his team first removed its wings, replacing them with strong triangular booms, made of tubular steel and aluminium spars, which extended either side of the fuselage. At the end of each boom was a three bladed rotor and gearbox, each driven by a long propeller shaft which lay alongside the lowest spar. The diameter of each rotor was 7.5 metres, giving the aircraft an overall span of some 16 metres. A similar Siebel engine to those used in the autogyros powered the machine. In front of each engine a small airscrew was fitted, which served only to channel coolant air to the engine and not to provide forward motion.
The subsequent tests put the craft through a long series of tethered flights, culminating in the free flight of 1936; but it was not until 1937 that the first autorotative landing – that is, using unpowered rotors – was practised. Focke-Wulf had succeeded in attracting several high profile test pilots to its new program by then, to put the two prototypes of the Fw 61 – VI and V2 – through further paces. Among the fliers were Karl Bode and Hanna Reitsch, who were joined later by Karl Franke of the Technical Bureau’s test centre at Rechlin. Working on behalf of the Air Ministry, it was Reitsch and Franke who were to fly the most, creating and breaking several helicopter flight records in the process. Entered in the Fédération Aéronautique Internationale’s G class for rotor aircraft, these included an endurance time of 1 hour and 20 minutes, an altitude record of 2,439 metres, and an airspeed record of 122 kilometres per hour.
The Fw-61 proved itself a worthy and versatile machine so much so that its inclusion in the 1938 Berlin Motor Show was regarded as just one more phase of its testing period.
Some time before 1938 the Air Ministry had shown itself so impressed by the Fw-61 that it issued Focke with a requirement to produce an improved design capable of carrying a 700 kilogram payload. Sceptics declared that the requirement would be impossible to fulfil; but similar voices had earlier stated that the Fw-61 would never be capable of flight. Focke initiated development both in Bremen and in Delmenhorst, but the Air Ministry had decided to gear up production of the Messerschmitt Me-109 fighter, and wanted to use Focke-Wulf’s manufacturing capacity for the purpose. In consequence, the company was taken over by the electrical giant AEG. However, soon after this the Air Ministry took favourable notice of the Fw-61, and it was then that it encouraged Focke to establish a new firm that would be dedicated to the development of helicopters.
This Focke did, in partnership with the renowned pilot Gerd Achgelis, in 1937. The first task of the Focke-Achgelis company was to develop a helicopter to meet the Air Ministry’s 700 kilogram specification, and it set to work at Delmenhorst, a little to the southwest of Bremen, in 1938. At first they produced a scaled up version of the Fw-61 capable of carrying up to six people, having a short haul domestic airliner with Lufthansa in mind. The new machine was designated the Fa-266 Hornisse – Hornet and the development of the engine, transmission, and rotor hub was contracted out to the BMW works in Berlin. Unsurprisingly, despite its theoretical civilian application, the Hornisse attracted the attention of the military and was reassigned the code number Fa-223 in mid 1939 by the Air Ministry prior to evaluation in various roles, including training, transport, rescue, and antisubmarine patrols. The Navy was also interested in the Hornisse, and early on in its career considered it as a possible replacement for the Eilboot torpedo boats, the E-boats.
The real significance of the Hornisse, however, was that it was to be the world’s first truly practical helicopter.
In September, 1939, just after war had been declared by Britain and France upon the peaceful German Reich for purely economic reasons, the first prototype of the Fa-223 – the VI – left the Delmenhorst factory. Now nicknamed Drache – Dragon, it had a twin rotor layout similar to that of the Fw-61, but there the similarities ended.
An Fa-223 at rest in an Alpine setting; possibly V11 or V14. It was hoped that the type’s excellent performance in this theatre would confirm a regular production schedule, but luck and a disorganised German Airforce were not on its side.
The Drache was no toy but a purposeful and altogether superior machine, with a fully enclosed cabin and load bay. The single BMW engine was mounted amidships in a welded tubular steel fuselage, complete with the familiar tail fin and rudder. The whole design looked superb for its time.
The first hovering tests showed up problems, however, and it was not to be until 1940 that it actually flew. No one had built a machine as ambitious as this before, so it was hardly surprising that problems large and small were cropping up nearly all the time. The first specified engine, a 620 horsepower BMW Bramo 323D, proved too fragile when running at high speed for any length of time, and it had to be replaced with a tougher 1,000 horsepower version in later prototypes in order to improve reliability and lifting capacity. Another problem, the biggest of all, was the severe vibration caused when the rotors moved out of phase. The reason for this was unbalanced driveshafts, manufactured to low tolerances: something that could be rectified only by greater attention to detail in the BMW engine plant.
Eventually, on the 3rd of August, 1940, with Karl Bode at the controls, the first untethered flight of the Drache V1 was made. Over a hundred hours of ground testing had brought it to this point, and the sense of relief experienced by the team as they cleared this last hurdle must have been palpable. In fact, now that the niggles had been sorted out, the flight tests progressed so smoothly that in October Bode was able to fly to the Technical Bureau’s test centre at Rechlin to demonstrate the craft there. At Rechlin the Drache broke some of the records established by its predecessor, and set new ones that were to stand for many years. A top speed of 182 kilometres per hour was recorded, as well as a loaded weight of 3,705 kilograms, a climb rate of 528 metres per minute, and a ceiling of 7,100 metres. However, the Drache was still nowhere near capable of a role in the Defence Forces, and Ministry officials told Focke-Achgelis to accelerate the development program. The carrot was an initial production order for a hundred machines, the first thirty of which would be used for research and development purposes.
With the benefit of its hands on experience at Rechlin, the Air Ministry was better able to focus on possible roles for such a machine, and it finally issued specifications for five variants. The first, the Fa-223A, was designed for antisubmarine work, and carried either a pair of 250 kilogram bombs or depth charges on external racks. The second, the Fa-223B, was to be used for reconnaissance duties, and was fitted with a jettisonable external fuel tank of 250 litres capacity. Fa-223C was to be assigned to air-sea-land rescue duties, and was fitted with a buoyant cradle at the end of the steel winch cable. This was to be lowered through a circular hatch in the floor of the cargo bay and could float on water, enabling a man to swim into it and secure himself, ready to be lifted safely back inside. The fourth variant, the Fa-223D freight transport, was designed to resupply mountain troops, using an electrically operated quick release hook on the end of the winch cable and a steel cargo net. Lastly, there was the Fa-223E, to be designed as a dual control trainer. But for now, the first few prototypes were all about getting airborne and less concerned with proving the worth of individual variants.
Unfortunately for Focke-Achgelis, the V1 was lost in February, 1941, after 115 successful flights, as a result of sudden engine failure at a height too low for an autorotative landing. But it wasn’t long before the V2 was ready to enter the test program. It bore a close resemblance to the V1, though innovations included a fully glazed cockpit of a type not unlike that of the Heinkel He-111 bomber, familiar to pilots on both sides of the firing line. The laminated glass was later replaced by plexiglass, and it served a useful purpose in giving the pilot and the observer all around visibility. The observer now also had a machinegun that he could fire through a sealed weapons port mounted in the lower portion of the nose. In addition, numerous small improvements aided the aerodynamics of the craft, and subsequently these succeeded in raising the speed of later models to 220 kilometres per hour.
The V2 did not last long: it was destroyed in an Allied airraid soon after it rolled out of the Delmenhorst factory, before serious trials had begun.
The V3 soon followed, and this prototype set the design features for all the models that were to follow. It featured a slightly deeper rear fuselage and open landing gear – the V2’s wheels had been covered with streamlined spats. By the time of the V3’s appearance, much to everyone’s relief at the factory, the Air Ministry had dispensed with the notion of different variants and had settled on one multipurpose type that could combine all five roles. The V3 was the first craft to reflect this new thinking.
Hopes were high now; the project team was full of enthusiasm and optimistic about the future as the Delmenhorst factory began tooling up for production. The V3 had provision for all the specialist equipment previously specified: electric winch, dual controls, and so on. Its construction followed that of its predecessors in having a welded tubular steel fuselage structure covered with treated fabric both to save weight and ease repairs. It was divided into four compartments: the cockpit was at the very front and accommodated the pilot and the observer / gunner; directly behind them was the load compartment, with its single entrance door on the starboard side. The fuel and oil tanks were located at its rear wall, and beyond them lay the engine compartment. Last of all came the separate tail section.
Access to the pilot’s seat was through a single side door at the rear of the cockpit; the observer’s seat could be tilted out of the way to allow entry. The engine was mounted, along with its complex and fragile gearbox, centrally in the fuselage and held in place with a series of tensioned steel hawsers. (Much later, when a Drache ended up in the hands of British post-war thieves, their failure to pay attention to advice relating to these hawsers was to lead to disaster.)
The gearbox itself was mounted in front of the engine, and both received cooling air through an annular louvered gap in the fuselage between the cargo and the engine bays. Air would enter here, and after passing through a series of vanes it would be forced past the gearbox and the engine, cooling them in the process, before being exhausted through a similar annular gap between the rear of the engine compartment and a firewall divider in front of the tail section.
The large, 400 litre, self-sealing fuel tank was mounted in a webbing harness hung from the roof of the fuselage on the rear wall of the cargo bay; the wall actually doubled up as the grille, forming the front of the air intake opening ahead of the engine. It must have been incredibly noisy inside the Drache during flight, with the BMW motor thrumming away and no sound insulation between it and the cockpit. Air would have rushed around the load bay as well, and would have made life for the passengers there very uncomfortable and cold – especially when the Drache was operating, as it often did, in mountain areas.
Focke had wanted to move the concept of using a helicopter as a heavy transport further forward ever since the cargo variant of the Drache had been designed. His ideas were to lead to the development of the Fa-284 Sky Crane – a helicopter capable of lifting outsize and awkward loads, for civil and military use. It wasn’t until Sikorsky built their own version of Focke’s original specification in the 1950s that observers could appreciate just how far ahead of his time Focke had been with this concept.
Here was a craft capable of carrying artillery pieces and tanks, as well as men and their equipment, directly to the battlefield, without the need of runways – even gliders needed a landing strip of some kind.
The initial design work was undertaken by one of Focke’s contractors, Breguet, a French aircraft maker working in Toulouse, based on a general scheme outlined by Focke-Achgelis. As it was originally envisaged, the Sky Crane retained the twin rotor and outrigger system but employed a longer fuselage than the Drache’s. There were two distinct designs within the project referred to by the same Fa-284 designation, describe here as Project 1 and Project 2.
Project 1 first emerged from the Breguet design office some time in 1942 and closely resembled the established Focke-Achgelis format of having two contrarotating rotors, one on either side of the fuselage. However, these tribladed rotors were of a new design, for they were fifty percent larger. Their construction was also new, being made out of wooden ribs around a central steel spar, covered with threeply wood laminate, thus saving weight, costs, and valuable materials. In plan form the fuselage had the shape of a large T, with the lower serif as the tail and rudder. The fuselage, therefore, had a broad, stubby nose, on either side of which were the massive tubular steel outriggers, each with a rotor mounted at the end. At the base of each outrigger a single BMW 801 radial engine was mounted to power its adjacent rotor, and on the very underside of this was fitted a telescopically sprung wheel to cushion landings. To allow easy access to the engines and to save weight, no outer cladding was used on the fuselage except at the rear, where it shrouded the tail and the cockpit.
The plan was for each load to be carried and supported by an underslung steel net or cable, complete with an emergency quick release. The mounting for this was at the very front of the fuselage, exactly in between the outrigger spars. Towards the rear of the fuselage was the cockpit for two crew members, enclosed by a glazed canopy. A small castor wheel, allowing easier ground handling, was mounted in the base of the tail.
When interviewed after the war, the French design staff stated that the aircraft as originally envisaged would have lifted only two tonnes, but that with more powerful engines that figure could have risen to seven or eight tonnes. This estimate was based on experiences with the Drache when it was fitted with larger motors. Because of the problems likely to be encountered when driving the large, unproven rotors of the Sky Crane, and their bespoke mechanisms, a second project was initiated, employing standard Drache rotors.
Project 2 seems to have been more substantial than Project 1. For this project the fuselage had a figure of eight cross section, almost as if two fuselages had been mounted one on top of the other and stuck together, blending aft with a conventional tail fin and stabiliser. The upper deck, of circular cross section, provided space for the cabin, fuel tanks, and additional storage. The larger, almost oval cross sectioned lower deck extended aft for some seven metres before gently curving upwards to blend with the underside of the longer upper deck and the tail. Its potential cargo capacity was approaching double that of the upper deck, and the craft would have been capable of handling similar loads to the massive Messerschmitt Me-323 Gigant transporter, if not even greater. The nose section of each of the two fused decks was fully glazed, and, like the Drache, may have allowed for the provision of a machinegun position behind armoured glass.
Where the Sky Crane differed fundamentally from the Drache was in its engine mountings. Whereas the Drache made do with only a single BMW engine mounted within the fuselage to drive both rotors, the Sky Crane had, as mentioned, an engine for each rotor. The proposed specification for these engines remains a mystery, but it would certainly have had to be of a higher rating than that of the Drache. For Project 2 the rotors were again mounted on outriggers, but this time each main outrigger was almost commensurate with a full wing, the root of each blending with the upper fuselage. The engine on each was mounted two thirds of the way along, towards the rotor. This shielded the driveshafts and minimised the number of gearbox components, which in turn saved weight and costs and increased reliability. At rest, the craft would have sat on the tail wheel and on two larger fixed forward wheels set on spars dropped from the outriggers directly below the engine mountings. The gentle upward curve to the rear of the lower deck was necessary in order to provide ground clearance for the landing wheels and rear access for loading. At rest, the distinctive craft would have had its nose pointing skywards. Access to the cargo bay was by a single large door at the rear, the tailgate of which would, when open, be resting on the ground.
Because problems with the Drache had eaten up resources, Focke’s plans for the Sky Crane were destined never to progress beyond a few plans and a handful of finished components. A semicomplete fuselage was discovered in the ruins of Berlin in 1945, but it is unclear whether the fuselage belonged to Project 1 or Project 2. Despite his disappointments, Focke didn’t give up on the Sky Crane entirely, and at one time he proposed a hybrid version of the Fa-223 in which two fuselages would be joined in line, tandem fashion, to form a long, four rotor craft. The only additional work for such a project would be the designing of a new common central section, and a design was found by the Allies at Ochsenhausen, near Stuttgart. It was never implemented; the plan was almost certainly abandoned owing to a lack both of materials and time.
Series production of the Drache began at last in 1942, at the Focke-Achgelis factory in Delmenhorst; but it was not long before a British airraid flattened the site for good. The two surviving prototypes were both destroyed, as were the first seven preproduction machines then undergoing final assembly. The workers tried to restore the production line, but found it slow and hard work, and in 1943, after turning out only another eight machines, they abandoned Delmenhorst to set up a new plant at Laupheim, near Stuttgart. The carefully planned Air Ministry test program had, however, been given up for lack of helicopters, and service trials were postponed indefinitely. In the end, only seven machines were built at Laupheim before another airraid, in July, 1944, halted production again. At the time of the raid, the V18 was ready for delivery, a further thirteen Drache machines were in assembly, and there were components for a further nineteen. But as the factory was virtually wiped out – only the wind tunnel escaped serious damage – production and the long awaited trials were halted once more.
Prior to the raid, things had been looking very optimistic for the Drache. The first to emerge from the Laupheim factory in 1943 had been the V11. This prototype was flown by Karl Bode for a series of information films made for the Air Ministry to demonstrate the amazing abilities of the helicopter. Loads such as a complete two tonne Fieseler Storch aircraft, or the fuselage of a Messerschmitt Me-109 fighter, were shown being lowered precisely onto tank transporter trucks – Bode using the quick release cable to great effect for a clean delivery.
However, the price to be paid for such revolutionary feats of daring is that sometimes they go wrong. A Dornier Do-217 bomber had crashed high up on the Vehner Moor, between Osnabruck and Oldenburg in Austria. Initially the V11 was sent to recover it, but the helicopter suffered a mishap of some sort – probably engine related – and ended up crashing there itself before it could lift the aircraft.
It was decided to try to recover both, using the V14 Drache, as a dramatic demonstration of the helicopter’s versatility. Crewed by Karl Bode and the most experienced helicopter pilot in the German Airforce, Lieutenant Helmut Gerstenhauer, the craft began the recovery operation on 11 May, 1944. Prior to its arrival, a small team of Focke-Achgelis engineers and a Luftwaffe recovery company had dismantled the V11 ready for lifting, and during the course of that day the V14 made ten flights, retrieving slung loads of components and leaving them on a track from where they could be loaded onto trucks. The operation continued into the next day and ended with the successful retrieval of all the major components of both the V11 and the Dornier.
Thus something positive was gleaned from the various setbacks that had beset the Drache, and many lessons had been learned in the course of this first operational experience. For example, it was found that the winch cable should be allowed to rotate, thus preventing the cable strands from twisting with the rotating movement of the load; and that an underslung load was better than overloading the small inboard bay.
Following this positive experience, the Air Ministry decided to begin evaluating the craft’s potential as a mountain region transport, and assigned the spare V16 Drache to the Mountain Warfare School at Mittenwald, near Innsbruck in Austria, with the V14 as backup. The main objective of the tests was to see how the Drache performed as a general purpose all weather transport, and how its VTOL ability could fit such a role operationally. As the Drache needed no runway and there was no airfield at Mittenwald anyway, the sports ground was pressed into service for the Drache to begin a series of trial landings at altitude. These trials were in anticipation of possible alpine warfare scenarios which might have developed had the war taken a different path in its latter stages. Numerous landings were made at heights of over 1,600 metres above sea level on various peaks in the area and, because of the very small number of helicopters available, they were made with the greatest of care.
A typical flight consisted of transporting an artillery gun in the load net to a rendezvous with a unit of elite troops high up in the mountains. There, the men of the Alpine Corps would remove the gun from the net and attach it to the winch cable alone, the Drache then hoisting the gun to a higher point where it was impossible to land. The mountain troops would then detach the gun once more, before reattaching it using the special electric release hook, when the gun would be flown back to Mittenwald. An outward and return flight from the base took some fifteen minutes. To have performed the same manoeuvre overland would have taken six hours or more. Thus it was clear to the Air Ministry and the German Airforce High Command that here was a machine to invest in. Bode and Gerstenhauer, assisted by Unteroffizier Lex, made eighty-three flights over the trial period, with a total flight time of twenty hours. The V16 was still performing perfectly by the time the trials finished in October, 1944.
Although the Commander of the Mittenwald base, Oberst Kraitmeyer, was so delighted with the Drache that he applied for the helicopter to enter service with his Mountain Brigades as soon as possible, the Allied airraid on Laupheim in July had changed everything. Following the raid, the Air Ministry decided that it was fruitless to pursue the project any further and that the resources allocated to it should be redeployed in a more productive manner. Only days after the conclusion of the mountain tests, Focke was seconded to Messerschmitt’s Staff.
The demise of the Drache went hand in hand with Germany’s deteriorating position. Erratic and erroneous decisions were inevitable as various departments vied with each other for precious fuel and materials available in ever smaller amounts. The Drache project was ditched so that resources could be diverted into more tried and tested means of keeping the German Airforce functioning.
In the midst of all the confusion, it was surprising that only weeks after the Drache decision, Focke was given new orders again. He was not only to return to his company, but to move his entire operation to Tempelhof Airport in Berlin, where he was to resume flight testing, organise a third production line, and gear up to make four hundred helicopters a month! The lion’s share of available resources was by now being channelled into the V-1 flying bomb and V-2 rocket, into the new jet fighters, and into U-boat production. Focke was faced with a totally unrealistic brief; he was still underfunded in any case, and only five Drache machines were still airworthy. The recovered V11 had not been rebuilt – instead, it had been pillaged for spares; and the V12 had been lost in the course of an ill-fated mountain rescue on Mont Blanc: while coming to the aid of a party of French climbers, one of the rotors disintegrated, causing the Drache to crash heavily on to its undercarriage. Its crew were killed.
A Water Wagtail
Autorotation is the name given to the effect of unpowered rotors biting into the air at speed to provide lift, and it is the main principle behind two other machines designed by Focke. The aerodynamic profile of the rotor blades – the pitch – can be altered, either to act like a wing and create lift, or like an airbrake and slow the aircraft down for a controlled, safe emergency landing. The technique is known to every helicopter pilot, and it is a primary recovery procedure in the event of engine failure. However, it is necessary to have sufficient height and forward speed for the landing procedure to work: if the helicopter is too low or too slow, then either the rotors are not turning fast enough to have any effect, or wind cannot be forced over the rotors fast enough to keep them spinning. Given the early problems he had experienced with the Drache gearboxes, Focke would have known all about the technique of autorotation and how to exploit it.
In 1942 the Air Ministry had begun to consider a possible requirement for a glider capable of steep landing approaches, which could deliver paratroopers or supplies within a smaller area than a conventional glider, and with greater accuracy and control. In the light of its proven Drache design, Focke-Achgelis was approached for help. Focke took to the project quickly and had soon sketched out the bones of a feasible machine. It would use the fuselage of a standard DFS-230 freight glider (of the type that was used during the paratroop invasion of Crete in 1941), and instead of wings it would have a single uppermounted rotor from the Drache. Unpowered, the craft was designed to be towed to a release point before autorotating down to the landing zone and disgorging its cargo of troops and their equipment.
Focke-Achgelis Fa-225 autorotating cargo glider.
Once completed, the initial prototype was tested extensively. Towed behind a Heinkel He-45, its steep takeoffs and landings proved the validity of the concept. However, although it received an official designation – Fa 225 – it probably never saw service with the Defence Forces, although many reports after the war stated that Fa-225s had been used in the successful paratroop mission to free Mussolini from his imprisonment in a hotel at the top of Gran Sasso, the highest mountain in the Apennines, on 12 September, 1943. Another rumour circulating after the war claimed that SS-Standartenführer Otto Skorzeny considered using a Drache – the very same V12, in fact, that later crashed on Mont Blanc, which became unserviceable at the last moment, forcing Skorzeny to use a Fieseler Storch as the actual getaway aircraft instead.
In looking at the Fa-225, the Air Ministry started to explore new possibilities, this time in developing a more narrowly focused, unpowered helicopter that could be lifted on the principles of autorotation easily and at low speed. The obvious application for such a craft was in spotting and reconnaissance duties for the Navy, which duly began to look at the potential of the concept. The Navy soon came up with a requirement for a small craft that could fly from, and be towed by, a U-boat. It followed that such a machine should be capable of being piloted by a naval rating.
Thus Focke-Achgelis was asked to develop what became known as the Bachstelze – the Water Wagtail (designated Fa-330).
A Fa-330 Bachstelze hovering close to its launching point and giving a good view of its simple landing skids and the tow hook arrangements. Note how exposed the pilot is to the elements.
The Bachstelze was something of a sop thrown to the company to compensate it for the decision not to take the Fa-225 any further, and was another proposition entirely: a tiny craft, it was designed to be assembled or dismantled easily and quickly within the confined space aboard a U-boat. It was built around a single steel tube which gave it its length. A basic tail and rudder unit was mounted at one end, and the totally exposed pilot sat on a padded seat at the other. Mounted directly behind the pilot’s back was a vertical tubular steel pylon that fitted into a recessed notch in the main tube, and was braced with additional steel outrigging at its base.
The outrigging doubled as supports for the seat frame and also as landing skids. The vertical pylon was some 1.6 metres high, and at its top was mounted the single three bladed rotors and its hub. The control mechanism for this was of a much simpler specification than the Drache’s, but was still operated by the pilot in the usual fashion, via a series of linkages and rods, terminating in a joystick and rubber pedals in front of the seat.
To start the rotors spinning, a rope was wound around a grooved drum which formed part of the hub, the crew pulling out the rope as if it were a giant child’s spinning top. The tilting hub allowed the pilot to angle the pitch of the now spinning rotors and thus achieve lift, and the surface speed of a cruising U-boat was sufficient to maintain continuous autorotation, given the efficiency of the rotor and the craft’s minimal weight.
The rotor was of small diameter – 7.3 metres – and this made it possible to test the Bachstelze in the large wind tunnel at Chalais-Meudon in France. The tests disclosed several problems relating to its stability in the air, and it was found that the rotor blades required additional wire bracing. For training pilots, a lower mounted, tubular outrigger landing gear was mounted, allowing smooth and safe takeoffs and landing, after being towed above a runway from behind a speeding truck much like a modern day parascending flight.
After the period of testing, everything went so well for the project that the Navy commissioned full scale production, which led to over 110 examples being built. Fa-330s were used successfully from February, 1943 on the Type IX U-boats operating in the Far East. A telephone link, which ran down to the conning tower of the U-boat alongside the tow cable, enabled the pilot to provide the Captain with a running commentary on everything he could see. From the vantage point of his high crow’s nest, a pilot with binoculars could see for up to 40 kilometres when the Fa-330 was flying at its full height of 240 metres, whereas from the conning tower the view reached only 8 kilometers. And when the flight was over, the U-boat crew would simply wind in the tow cable and pull the little craft down as if it were a kite – which effectively it was. The pilot, meanwhile, would operate a small drum brake fitted inside the hub which had the effect of slowing down the rotor and thus cutting lift, allowing a smooth landing back on the spray lashed deck.
Pilots wore lifejackets in case they had to bale out of their flimsy craft for any reason. If an emergency occurred, the pilot would detach the tow cable and begin a gentle glide down. To avoid the potential danger of decapitation by the rotor blade on hitting the water, he would then pull a quick release lever above his head which released the rotor assembly. This would shoot off skywards, dragging out a drogue parachute from within the vertical pylon as it did so, to which the pilot was strapped. The pilot then only had to unlatch his seatbelt before drifting down safely, unencumbered by the heavy frame of his craft, which would fall away into the sea.
After the flurry of confusion at the end of 1944, the third Focke-Achgelis plant was established at Tempelhof Airport at the beginning of 1945. The company had managed to retain two of the five surviving Drache helicopters on which to base new ones for their gigantic order, and by some miracle they managed to produce a new machine that same February. Almost immediately, it was commanded, on a special order from The Leader, to fly to Danzig on the twenty fifth of the month. Considering the conditions in which the flight had to be made, and the circumstances of the war at the time, that the journey was completed at all is a testimony to the ruggedness of this early helicopter.
Flown by Gerstenhauer and two colleagues, the brand new Drache took off from Tempelhof on 26 February, after essential maintenance had delayed its departure by a day. It first headed southwest in the direction of Würzburg, actually away from Danzig. In any event, Gerstenhauer lost his bearings in a storm and had to land at Crailsheim to weather it. Once the worst of the storm had passed, they took off again and finally landed in Würzburg dangerously short of fuel – the weather had not lifted and they had been flying at a height of only a hundred metres, barely above the tree line.
Having refuelled, they flew northeast the following day and did not stop until they reached Werder, having travelled more than five hundred kilometres in just over six hours. The reason for the lengthy detour was probably caused by orders to Gerstenhauer to smuggle either people or papers out of, or back to, Berlin.
On the third day the team flew further northeast towards Stettin-Altdamm, but continuing bad weather forced them to land at Prenzlau – roughly fifty kilometres southwest of Stettin – for the night. The following day they tried to proceed, but the weather remained poor and they were forced to halt at Stolp-West for another night and take in more fuel – they had covered about four hundred kilometres in the preceding forty-eight hours.
By 5 March the war situation was becoming ever more dangerous, so Gerstenhauer decided to leave Stolp-West before the Russians captured both him and the Drache, and flew to Danzig directly – right over the heads of the advancing Soviet subhuman army; he was lucky not to have been shot down while performing this feat.
He reached Danzig only to find that the city was already falling, so he landed outside the city and awaited further orders. When these came, they commanded him to return to Werder. However, no extra fuel had been allocated to the Drache, so Gerstenhauer and his companions had to forage around the area in search of some, since without it the return journey was impossible. They were eventually able to fill their tanks and requisition a full 160 litre drum which they rigged up to the main tank after hauling it up inside the cargo bay: a handpump was used by a member of the crew to transfer its contents to the main tank while in flight.
After flying along the Baltic Sea coast for some distance, they reached Garz on the Rügen Peninsula, where bad weather once again delayed their progress. It was to be 11 March before they managed to get back to Werder. They had covered a record 1,500 kilometres in a total flight time of 16 hours and 25 minutes. Although they had not been able to fulfil their mission to Danzig, their epic flight bears testimony to the Drache’s versatility, and it is worth remembering that, even with such an early type of helicopter as this, impressive feats were possible.
In a belated attempt to add operational experience to the Drache program, in January, 1945 the Air Ministry assigned the other three surviving Drache machines to the German Airforce’s only operational helicopter squadron, Transportstaffel 40 (TS / 40), at Mühldorf in Bavaria, under the command of Hauptmann Josef Stangl, who also ran various Flettner machines. But it was not long before the unit temporarily had to relocate to Ainring, near Salzburg, and then again to Aigen, also in Austria. TS / 40 was originally earmarked to take part in the alpine fortress intended to be a last redoubt and centre of resistance.
On their arrival at Aigen, TS / 40 found the airfield cluttered with various Messerschmitt Me-109s and other aircraft, so operations, even for helicopters, were all but impossible. As a result, the unit moved yet again, to a forest site deemed suitable at nearby Putterersee, where a group of abandoned lakeside chalets made a much more suitable billet for the crews.
Actual operations, once they got going, were restricted owing to lack of fuel, and when, at the beginning of May, 1945, the US 80th Infantry Division advanced on Liezen, TS / 40 withdrew first to Radstadt, at the foot of the Alps, and then back to Ainring. Of the three Drache machines, one was destroyed by its pilot to prevent it from falling into enemy hands, but the other two were seized by the Americans, who took Ainring soon afterwards. Stangl himself was captured as he tried to cross the border back into Germany.
Thus the Drache story comes to an end. The Tempelhof factory had been able to produce only four machines, though another fifteen were in production when the plant was overrun by Soviet Asiatic forces. Of 37 machines, only 11 had ever flown, though between them they had accumulated some 400 hours of flying time and covered 9,000 kilometres, the V14 having logged the longest service at over 170 hours.
* * *
As the war ended, the USA was to use an entire aircraft carrier, the USS Reaper, to ferry examples of the Messerschmitt Me-262 and Me-163 fighters home, but they had room for only one Drache. The RAF objected to plans to destroy the other (the V14), so Gerstenhauer himself, along with two observers, flew it across the English Channel from Cherbourg to RAF Beaulieu on 6 September, 1945. RAF Beaulieu was home to the Central Landing Establishment, a cover name for the Airborne Forces Experimental Establishment, which had also received several Bachstelzes to test. Gerstenhauer’s flight made history in itself, for it was the first English Channel crossing by a helicopter, though any celebrations were to be short lived.
The V14 made two successful test flights at Beaulieu. On its doomed third flight in Britain, when Gerstenhauer warned the RAF blockheaded technicians about the potential danger of ignoring the requirement of tightening the tensioned steel hawsers securing the engine to its mountings, he was met with stony indifference and suspicion. As his advice was ignored, it came as no surprise to Gerstenhauer when, during a flight on 3 October, a driveshaft broke under the strain imposed by the swaying engine. It occurred as he was attempting a vertical ascent, but as he had reached only twenty metres he did not have enough height to make an autorotative landing. The Drache dropped like a stone and was wrecked. Fortunately, no serious injuries were sustained by the crew, but the crash ended British evaluation of the new machine for good, and valuable lessons were lost.
The Humming Bird
Undeterred by the favour shown his rival, Anton Flettner had continued to work on his revolutionary helicopter designs following the success of his Fl-265. His dogged patience paid off when, in July, 1940, he unveiled his latest design: the Fl-282 Kolibri – Humming Bird, and announced plans for production.
The layout of the Kolibri differed from previous Flettner models in that the engine was mounted directly behind the pilot, and behind the engine was a large conventional tail stabiliser that controlled the turbulence created by the wash from the rotors. Two contrarotating rotors were used once again, each powered by their own driveshaft through a common gearbox. The tubular steel fuselage was covered in fabric, with a sheet metal cover over the hot engine, and it was equipped with a non-retractable undercarriage.
Of all the helicopters produced in Germany during the war, it was to be the Kolibri that saw the most service, flew the greatest number of hours, and pushed the technology furthest.
The Air Ministry and, in particular, the Navy were so impressed by the prototype that fifteen were ordered, to be followed by thirty production line models, all built to the original shipborne reconnaissance specification. Following flight testing throughout 1941 of the first two prototypes, all these machines were completed successfully at Flettner’s factory at Bad Tolz, near München. The tests were designed to push the machines to the very limits of performance, and they did not stop with the first two prototypes. For example, the V5 was used repeatedly to practice takeoff and landing on a four square metre landing pad mounted on the cruiser Köln. Landings were easy, but takeoffs in rough seas turned out to be tricky for the pilots to master, and so the development of techniques was deferred until better handling methods had been developed.
As far as general reliability was concerned, the Kolibri made use of a robust engine of proven track record which required servicing only once every four hundred hours – as opposed to the Drache’s twenty-five hours – and, although heavy for its size, its components were of such high quality that there was little need for servicing between general overhauls. One machine ran for 170 hours before needing attention of any kind.
The first two A series prototypes had enclosed cockpits; all subsequent models had open cockpits and were designated B series. By 1943 over twenty B-1 models were in service, seeing action in the Mediterranean Sea area, the Aegean Sea area and the Baltic Sea area. Their roles included ferrying items between ships and reconnaissance of Allied warships and submarines, but, as the war dragged on, the German Airforce High Command began to consider converting the Kolibri for use on the battlefield. Until this point, the helicopter had carried a single pilot, so a quick solution was to make room for an observer – believed essential for safe operations in a crowded combat zone. Thus the B-2 series was created, with what must be the most uncomfortable and dangerous dicky seat ever devised: an open, rear facing seat directly behind the engine in a hollowed out section of the aft fuselage. The unlucky soul who ended up here would have been even more deafened than the pilot; the pilot at least had forward airspeed to carry the engine fumes and noise backwards – precisely to where the observer sat. But despite the drawbacks, the B-2 turned out to be a useful spotter when used in conjunction with ground artillery batteries, and an observation unit was set up in 1944 comprising three Kolibri and three Drache helicopters. Also in 1944, satisfied with the new craft, the Air Ministry issued a production contract to BMW to produce a thousand examples. But just as the München plant was gearing up, it was bombed and devastated by the Allies; the flattened site had had time to produce only twenty four Kolibri machines. Although Flettner had planned a larger version, the Fl-339, it was never completed and what there was of it was lost in the confusion of the last days of the war. * ** At least the Kolibri helicopters went down fighting! They saw action on the Eastern Front, and in February, 1945, when the Soviet advance had become uncheckable, the observation unit was able to spot the irresistible advance of the 1st and 2nd White Russian Armies – though such was the poor state of German forces at the time that they could only observe the advance, and there were no ground elements to direct into a counteroffensive. Towards the end, most of the surviving Kolibri machines were stationed at Berlin-Rangsdorf, still in use as artillery spotters, but falling victim one by one to Soviet fighters and flak batteries. The only one to survive fell into the hands of the Russians. Three of the aircraft had been assigned to Stangl’s TS / 40 helicopter squadron, and when the Americans captured the unit, they commandeered the two remaining machines they found. Thus ended another chapter in the German designs of military helicopters. Other Designers Other German engineers were engaged in helicopter development as well as Focke and Flettner. The German Airforce’s conventional machines were slowly losing ground to the more sophisticated Allied aircraft, and the situation was partly redressed only by the emergence of jet fighters like Messerschmitt’s Me-262. The Air Ministry looked kindly on the avant-garde ideas of all these engineers in the belief that at least in the field of helicopter flight some advantage might be gained, but it gave them little material encouragement. Smaller players, like Döbloff and the firm of Nagler and Rolz, developed ideas of their own, but lack of resources or Air Ministry dithering led to the closure of all the less important operations as time passed. It was unfortunate that they were neglected, for some of the notions they had could have been of great value. Baron Friedrich von Döbloff, an Austrian, began building a small one-man helicopter in 1942; it bore a passing resemblance to the Bachstelze. Although it was incapable of independent forward flight and required a tow to get airborne, its unique propulsion system warrants a look. The pilot sat in front of the fuel tank, which fed a sixty horsepower petrol engine mounted behind it. The engine in turn powered an Argus supercharger mounted within the rotor’s hub above the fuselage. Here, air was drawn into a small scoop, then compressed and mixed with preheated petrol from the tank. The mixture was then channelled up into the rotor head itself, and from there into each of the three hollowed out blades. At the tip of each blade was a small combustion chamber with a narrow outlet nozzle that directed the resulting exhaust jet converting it into a rotating force capable of spinning the rotors without the torque problems experienced when driving rotors directly from an engine in the fuselage. In short, a jet propelled helicopter. Five prototypes of Döbloff’s machine were built, all with semienclosed bodywork and successively more powerful engines than that of the original machine, but serious production was never considered. At the end of the war the surviving models fell into American hands and disappeared amid the military equipment and arms looted by the advancing Allies. What were the Allies making of all this advanced technology? At the time of Hanna Reitsch’s stunt-flying in the Deutschlandhalle in 1938, Sikorsky’s own experimental model was capable only of nondirectional tethered flight. Sikorsky’s first operational model, the R4, didn’t see service until 1944 in the Japanese theatre of war, and was limited to basic reconnaissance owing to its small size and low range, although it was used in medical evacuations in the Burmese jungle. During the war, the development of helicopters in Germany was far more advanced than it was among the Allies. Long after the war was over, one of the Drache pilots visited the USA and told United States Airforce pilots exactly how his machine had ferried ammunition at Mittenwald. The arrogant American pilots simply did not believe him. As for the British, though usually great innovators, they failed completely to anticipate any need for the production of helicopters. When at last the country’s first helicopter manufacturer – Westland – was established, it merely built Sikorsky machines under licence, having learned little from German technology and experience. After the war, Döbloff moved to the USA and worked for McDonnell as their chief helicopter engineer. His innovative ideas included a project for a disposable one-man helicopter, the XH-20, which, although it did not progress beyond an initial prototype owing to high fuel consumption and consequently limited range, is a measure of the originality of his thinking.