Aeronautical engineer Anton Flettner began his career fascinated with the flow of air. He designed a ship powered by the "Magnus effect," the spinning of an object that puts "English" on a basketball shot. And he also designed the Flettner ventilator, the fan powered only by the heat rising from an attic, found in many vehicles and buildings today.
Devoted to his inventions, and made rich by his ventilator, Flettner at first set up shop in the Netherlands in the 1920's before returning to Germany in the 1930's to found a firm to build autogyros. Despite the fact that his wife and best friend were both Jewish, Flettner worked for the Nazis and received special dispensation for his associations: his wife and her family were taken to Sweden by a special SS escort. His friend and colleague, Kurt Hohenemser, remained at Flettner Flugzeugbau GmbH throughout the war and apparently was never threatened by the Nazi mass murder machine.
Flettner's Fl.184 autogyro (an aircraft assisted by a rotor) attracted the German Navy's attention in 1935, but during some final tests before its presentation to the Navy it caught fire and was destroyed. He then developed an improved version, the Fl.185, but abandoned the project when he hit on the notion of using intermeshed, counter-rotating rotors to cancel out the torque caused by a single rotor. With this arrangement, the propeller used in autogyro designs would not be necessary and the rotor itself could provide power as well as lift.
The Fl.185 autogyro, Flettner's last such design.
The German Navy also showed intense interest in Flettner's first true helicopter, the Fl.265, placing an order for six machines even before the design was complete and providing a cruiser for shipboard testing. Flettner used an airframe very similar to the Fl.185, with the engine mounted in the traditional nose position. Critics claimed the intermeshing rotors would inevitably collide and bring the machine to earth in flames, and true to predictions the first prototype met exactly that fate. The second crashed when it ran out of fuel a few minutes into a flight.
An Fl.265 comes in for a landing on the light cruiser Köln.
The remaining four machines had very successful tests, taking off and landing from ships and even submarines, and locating submerged u-boats. The Army learned of the tests and expressed interest as well, and Flettner organized some demonstrations for Wehrmacht officers. The Fl.265 assisted in river crossing exercises with Army troops, towing inflatable boats and lifting bridge sections into place.
The Army officers were impressed, but wondered how the helicopter would fare if attacked by enemy fighter planes. Flettner arranged a demonstration in the summer of 1939, and Luftwaffe Bf.109 fighters tried to "shoot down" the helicopter in simulated air combat. No "hits" showed on gun camera footage - but a demonstration arranged by the contractor in the Germany of 1939 was no more likely to show an unfavorable result than one arranged by another great power decades years later.
One of the four surviving Fl.265 helicopters, sometime in the winter of 1939-1940.
Enthused, the Navy ordered series production to begin, but Flettner believed his new design, the Fl.282 "Kolibri" ("Hummingbird"), would be a far more capable machine, and persuaded the Navy to shift its order to the as-yet-unbuilt aircraft. Thirty prototypes and fifteen more pre-production models were ordered, and Flettner's firm began building them in the spring of 1940. With Flettner and Hohenemser insisting they had to personally assemble the complicated gearboxes that drove the counter-rotating rotors, production moved very slowly and it was a year before the first Kolibri took to the air.
Despite this slowdown, the Fl.282 was indeed a far superior observation craft than its predecessor: with the engine moved to the center of the craft, the pilot had an unobstructed view ahead and below. While the earlier machines showed their obvious roots in the inter-war German obsession with gliders and sailplanes, the Kolibri was intended from the start as a military aircraft. It would carry two people: a pilot and an observer. The observer sat facing rearward, with the engine between his compartment and that of the pilot. This arrangement allowed the Kolibri to fly with the rear seat unoccupied without trim problems. The very first machines had glassed-in canopies for both crew positions, but these proved awkward and later versions had none. The small machine had two twin-bladed rotors, slightly offset from each other, and a large rudder for steering (varying the pitch of the rotors also contributed to steering).
It was not a perfect machine. A crashed Kolibri at the Travemunde testing facility.
Flettner foresaw his helicopter being used for artillery spotting on land and anti-submarine work at sea. On seeing the helicopter demonstrated, military liaison officers immediately agreed and placed orders. The Fl.282 could also be disassembled and stored in a pressurized tube for operations from a submarine, but Flettner and his team never tested this mode of operation.
Flettner finished the design in the summer of 1940, and began construction of the 45 helicopters. Flight tests commenced the following spring. The aircraft proved very maneuverable, though prone to heavy vibration. With this problem solved it proved very stable in flight, though it still rocked badly on the ground. With the pilot alone they could do about 150 kilometers per hour, and had a range of roughly 260 kilometers. With an observer, performance dropped to 105 kilometers per hour and a range of about 200 kilometers.
In 1942, production versions began to appear, with the first of these delivered to the German Navy. Some of these had a small bomb bay to carry a depth charge in place of the observer. These machines operated from the repair ship Grief and cruiser Köln in the Baltic and the helicopter carrier/minelayer Drache in the Aegean Sea.
The German Army appreciated the machine’s qualities, and saw a great future for it as an artillery spotter. The Kolibri and its support staff could be set up and operate from very rough field conditions, allowing batteries to always have aerial spotting as long as the weather permitted. In 1944, plans called for a helicopter spotting section for each artillery brigade, and the small helicopters also would take a role in reconnaissance battalions.
A Kolibri with glazed cockpit.
Helicopters appealed to the German Army and Navy for one of the same reasons they later became very popular with the corresponding American branches. Operating them exercised a loophole in the rules giving the Air Force sole authority over anything that flew. Even though the Luftwaffe operated the lone German unit to use helicopters during the war, the machines were always projects of the Army (sometimes joint Army/Navy) or the civilian Air Ministry.
Civilian contractors played a major role in the helicopter establishment. Instead of going through a formal helicopter flight school, many of the Army and Navy pilots seem to have gained their knowledge from the Flettner and Focke-Achgelis test teams. Civilian test pilots accompanied their helicopters to the front, serving aboard Navy ships to observe the helicopters in action and even fly them there.
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Mike Bennighof is president of Avalanche Press and holds a doctorate in history from Emory University. A Fulbright Scholar and award-winning journalist, he has published over 100 books, games and articles on historical subjects.
He lives in Birmingham, Alabama with his wife, three children and his dog, Leopold.