1/18 scale Flettner Fl-282 V21 Kolibri scratchbuild model

After request, a 1/18 scale Fl-282 V6 helicopter with WWII Kriegsmarine markings built for a wealthy collector from Kiel, Germany. A second Luftwaffe’s Fl-282 V21 model followed for my own personal collection at home. Since the whole project cost (CAD design, 3D printing & model building) was entirely funded by the client, I did not hesitate to use the best available materials & machines to do the job. The text follows, is to describe the Flettner Fl-282 Kolibri (“B-0” series) helicopter as manufactured by Anton Flettner Flugzeugbau GmbH on early 1940ies, used by Kriegsmarine & Luftwaffe during WWII and scratch built by me as a 1/18 scale model, now days.





Anton Flettner was a German aviation engineer & inventor who made important contributions on airplane & helicopter design. During the WWI, Anton Flettner developed remote control & pilotless aircraft projects, which culminated in the prototype Siemens Schuckert Werke 1000 kg wire guided air to surface missile of 1918. Following WWI, he directed aeronautical & hydrodynamic research institute in Amsterdam and during the WWII, he headed the Anton Flettner Flugzeugbau GmbH, which specialized in helicopters. It is believed that the firm was founded in Berlin in 1935. By this time, however, Flettner had developed the idea of counter-rotating, intermeshing twin rotors. Many of his advisers thought that the airflow disturbed by the intermeshing blades would make this system less efficient than one using a single rotor; but Flettner believed that any problems thus encountered would be more than offset by the reduced drag resulting from having no external rotor-carrying structure. His pioneer work is often overshadowed by the more publicised activities of his contemporaries Heinrich Karl Johann Focke and Igor Sikorsky; yet Flettner’s helicopter, was far superior to the Henrich Focke’s FW-61 and made a successful free flight several months before Igor Sikorsky’s VS-300 began tethered flights.

Following pictures taken at Pfaffenwiesbach a district of the municipality Wehrheim, Germany. This artistic wall painting cultural monument, created by the local municipal council in memory of Anton Flettner who was the village teacher in Pfaffenwiesbach from 1906 to 1909.





Although Anton Flettner built his helicopters for the German military, his wife Lydia Freudenberg Flettner was Jewish. Because of his personal friendship relationship with head of Gestapo, Heinrich Himmler, Anton Flettner’s Jewish wife and their family safely moved to Sweden for the duration of World War II. Anton Flettner’s partner and confidant was Dr. Kurt Hohenemser, a brilliant and thorough engineer who developed the details necessary for the helicopter’s success. Dr. Hohenemser's father was also Jewish, yet the pair remained unharmed during their tenure together throughout the War as they worked to develop the helicopter for military use. While the final product could be factory assembled, Anton Flettner and his partner Dr. Kurt Hohenemser insisted that they were the only ones who were capable of assembling the complex intermeshing rotor gearbox assembly. However, plans for 1000 helicopters mass production were made, the project was disrupted by the destruction of the designated factory by Allied bombing.



In following pictures, Anton Flettner is proudly posing in front of his Fl-282s fleet at Schweidnitz (today Świdnica, Poland), on October 1944. The first helicopter is a V14 registered as CJ-SH.





Upon the WWII conclusion, Anton Flettner was held in the “Dustbin” interrogation camp at Kransberg castle. After 1945, Flettner, along with many other aviation pioneers, was brought to the United States as part of Operation Paperclip. He started Flettner Aircraft Corporation, which developed helicopters for the US military. His company was not commercially successful, but his work was shared with the Army Air Corps. Many of his designs, such as intermeshing rotor concept, saw widespread use in a series of postwar helicopters built by Kaman for the US Navy and USAF. Anton Flettner moved to the United States in 1947 to work as a consultant to the Office of Naval research and became the chief designer of Kaman Aircraft, creating the Kaman HH-43 Huskie, a concept with intermeshing rotors. He died at age 76 in New York City, USA on December 29th, 1961 and buried in Eddersheim cemetery at Frankfurt, Germany where he was born. In following photograph, Anton Flettner (2nd from left) meets Wernher von Braun (3rd from left).



Düzenleyen Nick_Karatzides - 27/07/2018 Saat 11:58

It was equipped with flight and navigation instruments such as an ASI - AirSpeed Indicator, an altimeter, a VSI - Vertical Speed Indicator, a turn & bank indicator, RPM indicator for rotors, rotor blade angle indicator, a master compass and a dashboard clock. Radio & signalling equipment consisted of a FuG 19 ultra short wave radio installation. Back type parachute, first aid kit, signal flare pistol and one-man inflatable raft were also present. In following pictures, the instrument panel of the first three prototype helicopters with fully enclosed cabins made up of a series of optically flat plexiglass panels.







The Flettner Fl-282 Kolibri was equipped with a Bramo Siemens Halske SH-14A, 7-cylinders radial engine of 119 kW (160 hp) mounted in the center of the fuselage, with a transmission unit on the front of the engine from which a drive shaft ran to an upper gearbox, which then split the power to a pair of opposite drive shafts to turn the rotors. The SH-14A was an already tried engine design that only required servicing every 400 operating hours.







A drive shaft with universal joints took the drive from the engine transmission unit to the upper transmission unit, which consisted of gears and shafts connecting the two rotor shafts. The final cross-shaft between the two rotor shafts was fitted with a free wheeling unit to disconnect the engine drive, and also with a rotor brake. On the drive-shaft from the engine, a friction disc clutch was fitted which was used for running up the rotors until there was no slippage, when a positive dog-type clutch, on the same shaft, was then engaged. Total reduction through all the transmission units was 12.2 to 1. Cooling air for the enclosed engine was drawn in through openings beneath the fuselage by an eight blade wooden cooling fan with direct drive from the engine and a high pressure air tank was connected to the engine cylinders through a distributor for starting.



Düzenleyen Nick_Karatzides - 27/07/2018 Saat 11:59

The Kriegsmarine HQs was impressed with the Flettner Fl-282 Kolibri and wanted to evaluate it for submarine spotting duties, ordering an initial 15 helicopters, to be followed by 30 production models. Flight testing of the first two prototypes (with enclosed plexiglass panelled cabins and 3-bladed rotors installed, instead of the 2-bladed rotors on production models) was carried out through 1941, including repeated takeoffs and landings from a 13 m² wide platform pad mounted on the German cruiser “Köln”. Intended roles of Flettner Fl-282 Kolibri included ferrying items between Kriegsmarine ships and naval reconnaissance operation from cruisers and other warships. The entire Fl-282 flight test program was not conducted at Rechlin, as was customary for land based aircraft; instead, from August 1942, trials were carried out at E-Stelle See Travemünde. Travemünde was selected because the air traffic safety ship “Greif” was based there and could be used for deck landing trials. The site also simplified helicopter sea trials with the navy, it was also imperative to move the site of the trials from Flettner's facility in Berlin, where there was a greater risk from the growing Allied bombing raids.





On September 1942 a Fl-282 Kolibri V12 version with registration CJ-SF, was initially tested by Anton Flettner's chief pilot Oberleutnant (Luftwaffe 1st Lieutenant) Hans E. Fuisting, aboard the Kriegsmarine's ship “Greif'”, a 2000 ton aircraft salvage ship. Few weeks later, in October 1942, another two Fl-282 helicopters, one V6 version with registration GF-YF and one V10 version with CJ-SD registration, were delivered to Trieste with their personnel, including Hauptmann (Luftwaffe Captain) Klaus von Winterfeldt, Anton Flettner’s chief pilot Oberleutnant (Luftwaffe 1st Lieutenant) Hans E. Fuisting and a 3rd pilot (his name & rank are unknown) plus three mechanics for technical support. From November 1942 until February 1943, the Fl-282 V6 registered as GF-YF, had been extensively tested aboard the Kriegsmarine's minelayer “Drach” (“Schiff 50”, ex-Yugoslavian “Zmaj”) while operating in Aegean Sea, north of Crete, Greece, following the absence of RAF aircrafts in the area for few months. The second V10 Kolibri registered as CJ-SD, was a reserve machine that stayed ashore.

The helicopter was operated from a 15 m² wide platform pad, while the ship was moving. It was no simple matter setting a helicopter down on the waving deck of a ship, so a special system was designed to bring the two vehicles together. A 10 meters long cable was attached to a swiveling fixture on the bottom of the helicopter. The pilot would bring the helicopter in to hover just out of ground effect over the platform and release the free end of the cable. Two men on the deck would grab the cable and hook it onto the winch drum, pulling the helicopter down to the deck. While this was going on the pilot applied enough power to keep the cable taunt, thus the helicopter took the waves in unison with the ship. The reverse procedure would be performed for take-off. A similar method is still used today for operating helicopters off of ships in rough weather.



By 1943, the Fl-282s were routinely being used by the Kriegsmarine for convoy protection and reconnaissance. Usually they flew from platforms above the gun turrets of convoy escort vessels in the Aegean, Baltic and Mediterranean Seas, often in extreme weather conditions. The Flettner Fl-282s revealed control & performance qualities well above expectations and found to be especially valuable at dawn or dusk when fixed wing aircraft pilots did not have good visual contact in the poor light. As an important area of operations, the Mediterranean Sea offered the promise of worthwhile missions for the Kolibri and the tactical trials could be conducted into the most favourable weather conditions. As well, the U-617 submarine was also available to participate to the trials. During the day, helicopter crews could spot the submarine as deep as 130 ft. Once a sub was spotted the Kolibri could easily match the speed & course of the submarine, which was impossible for the fixed wing aircraft with stall speeds higher than the cruise speed of a submarine. The Fl-282 would then radio transmit the sub's position to the convoy and if a warship was dispatched to attack on sub, the helicopter would mark the target's position with a magnesium flash bomb or marker flares. The V9 helicopter registered as CJ-SC was the prototype for a version to be operated by the Navy from large submarines and designated as Fl-282 U (Umbau) “Modified Model in Form of a Standing Cylinder” version. Although the Fl-282 was designed so the rotor blades and landing gear could be removed and the helicopter stored in a compact area such as the pressure tank of a U-boat, there is no evidence that it was ever used this way.



Further service trials carried out later in the Baltic Sea aboard the anti-submarine vessel KUJ 13 (type KUJ 41) from 24th April 1943 to 15th May 1943, in conjunction with the 21st U-boat training flotilla, as part of the Kriegsmarine’s ongoing exercises for sea missions in the area of Danzig Bay and the north tip of Gotland island. The fleet exercises involved underwater attacks on simulated convoys consisting of target vessels & escorts. Once, over a convoy, test pilot Hauptmann (Luftwaffe Captain) Klaus von Winterfeldt was able to make out all twelve (!!!) submarines that sent against convoy.



On May 3rd and 4th 1943, a special experiment took place in cooperation with the DVL's Institute for Marine Aviation. It involved ‘towing tests with a 50 kg gliding body”. The proposal originated from Hauptmann (Luftwaffe Captain) Klaus von Winterfeldt, director of the Erprobungs und Lehrkommando (Testing and Instruction Detachment) that time, who carried out the towing flights from an anti-submarine vessel in Gotenhafen. In addition to its role as a reconnaissance aircraft in support of the sub-chasers, armed with bombs the Fl-282 was also to participate actively in the anti-submarine role. Unfortunately, on May 10th 1943, Hauptmann (Luftwaffe Captain) Klaus von Winterfeldt (pictured in following photograph) run out of fuel, crashed in sea (35 nm NE from Christlansoya island) and killed, while flown the GF-YF registered V6 testing helicopter. He was posthumously promoted to Luftwaffe Major for his work in helicopter development.



Düzenleyen Nick_Karatzides - 27/07/2018 Saat 12:04

Towards the end of World War II, most of the surviving Flettner Fl-282s were stationed at Rangsdorf AB & Ainring AB at Mühldorf, Bavaria, in their role as artillery spotters, assigned to TransportStaffel (transport squadron) TS40, the Luftwaffe's only operational helicopter squadron but gradually fell victim to Soviet fighters and anti-aircraft fire. During the last few months of the War the Luftwaffe's TransportStaffel TS40 squadron made many flights into and out of besieged and encircled towns transporting dispatches, mail and key personnel. It was possibly one of this unit's Fl-282s that flew Gauleiter (governor of Lower Silesia, Bavaria), Reichsführer SS and Chief of the Deutschen Polizei Karl August Hanke, to his escape out of besieged Breslau, on May 5th 1945, letting him escape to Prague, just one day before the capture of that city. It seems that it was the CI-TU registered Fl-282 V21, as the only available two-seater helicopter in squadron that date, since the other V23 (registered as CI-TW) two-seater, had been flown away and hidden at Bad Tölz few days earlier (on April 26th 1945 flown by company’s chief pilot Hans E. Fuisting). By May 7th 1945, the Soviets were located less than 19 miles away from Fl-282 base and orders were received to transfer westward to avoid capture. On May 8th 1945, the ground element of TransportStaffel TS40 set out by road to Zell-am-See. Since there were no available pilots for the remaining Fl-282s, attempts were made to destroy the helicopters. Unfortunately, very few Fl-282s survived the War and only five found by the Allies in a serviceable condition for testing and evaluating. Also unfortunately, the Fl-282 helicopter was not so much photographed and there are not available photographic records of each one of these 24 helicopters produced. Actually, the total (known) photographs while serving under Kriegsmarine’s & Luftwaffe’s markings, might not exceed total 100 - in which more usual protagonists are the V6 (naval tests) and the V21 (double seats), both typical examples of the type but both did not survive the War.

Captured helicopters #1 & #2: The first two flyable helicopters were found intact by US Army troops. One V23 helicopter registered as CI-TW and one V15 registered as CJ-SI. These two Fl-282s, received the FE-4613 and FE-4614 US numbers after been captured and transported from Cherbourg Octeville, France to Newark New Jersey, USA (Operation “Seahorse” from July 12nd 1945 to July 19th 1945) aboard HMS “Reaper” D82 (a “Bogue” class escort aircraft carrier of US Navy, leased to the Royal Navy during WWII) for further investigation. The Fl-282 V23 Kolibri was a two-seater similar to the V21, with V-shaped stabilizer fins. Into following pictures, notice the exact same V23 helicopter as seen with pre-capture Luftwaffe’s CI-TW registration & swastika markings and later in USAAF service with the FE-4613 US numbers visible, after been captured.





These two Fl-282s found & captured by the US Army troops were actually revealed by Anton Flettner himself. These two helicopters were flown from Schweidnitz to Bad Tölz, few days earlier, on April 26th 1945. The first (CI-TW registered V23) flown by company’s chief pilot Oberleutnant (Luftwaffe 1st Lieutenant) Hans E. Fuisting, was hidden in a barn near Bad Tölz. The other (CJ-SI registered V15) helicopter flown by pilot Ernst Remain, was hidden in a mill near Penzburg, 15 km west of Bad Tölz. Following the arrival of the US Army forces, Anton Flettner reported the hiding places to the US military administration in Bad Tölz. The two US held Fl-282s were first taken to Munich and then to Stuttgart (Nellingen flugplatz) where been demonstrated to Allied officers by German pilots. Since USAAF officers were impressed with the helicopters, the captured Fl-282 V23 (CI-TW / FE-4613 registered) Kolibri transferred to St. Dizier, France on June 15th 1945 and been demonstrated by Anton Flettner’s chief pilot Oberleutnant (Luftwaffe 1st Lieutenant) Hans E. Fuisting. By December 1945, the Air Technical Intelligence collection and evaluation process for Luftwaffe technology officially transferred from London, UK to Wilbur Wright Field (officially “Area B” of Wright Patterson AFB) near Riverside Ohio, USA.







The evaluation flights in US (115 hours) were conducted at Benedict airport, Booth Corners Pennsylvania, USA by Prewitt Aircraft company test pilot Captain Dave Driskill. The objectives of the tests were to determine power requirements, control response, stability measurements & a comparison between a straight and a V-shaped stabilizer. In March 1946, the Air Technical Service Command became Air Material Command and it was around this time the “FE” numbers, assigned to captured Luftwaffe aircrafts, became “T2” being the organization designator for Air Technical Intelligence. The prefix “FE” (meaning Foreign Equipment) changed to “T2” but the inventory numbers did not change. This probably reflected the organizational changes taking place. Now days, the Fl-282 V15 is presented at the Cranfleld Institute of Technology. On the other hand, although the V23 helicopter was transported and placed at the National Museum of the United States Air Force, located at Wright Patterson AFB 6 miles NE of Dayton Ohio USA, its current whereabouts are unknown.







Captured helicopter #3: On May 9th 1945, pilot Max Schmid (pictured in following photograph) trying to escape capturing by Red Army, flown with the CI-TV registered V22 helicopter to his home village of Wallern (about 130 km SE of Vienna, Austria) to rejoin his wife & children. He landed at his family farmhouse backyard and with the help of his wife he managed to hide the helicopter in the barn. Unfortunately his flight did not go unnoticed and soon US troops arrived and arrest him. Max Schmid refused to fly and demonstrate the Fl-282 for the Americans. Instead he helped them dismantle the Kolibri for transport. Unfortunately, no more info is available about the fate of Max Schmid’s CI-TV registered Fl-282 V22 helicopter after the War.



Düzenleyen Nick_Karatzides - 27/07/2018 Saat 12:05

CHAPTER II - Converting Mbytes into actual physical objects

Before start building a new scale model, I always try to study as much as possible the object of construction. Any available references such as technical manuals and detailed photos always help during building process. As described into my previously uploaded WIPs into this forum (feel free to have a look on the IS-A Salamandra glider and the Wallis WA-116 autogyro 3D printed models under 1/18 scale), the plan is to design a detailed CAD file and then print it, on a 3D replicator. Following this method helps a lot and gives the opportunity to scratchbuild almost anything, under any scale, within short time. The 3D printing technology introduction into scale modelling and free access to the average modeller is a great evolution in the hobby and a creative tool that helps us to build better and more realistic models. Certainly the new technologies and gadget tools in the hands of talented enthusiasts open new horizons and provide almost unlimited potentials on scale model building.



Because the detail complexity of the model, the present Kolibri project took approx 150 hours of computer work, to CAD design within a hundredth of a mm accuracy, scale into correct 1/18 size and then digitally cut the helicopter’s compartments into virtual pieces, having always in mind that the later 3D printed parts, should perfectly fit and finally become a fine scale model. Most amazing part is that after the CAD file is ready, the model can be produced under any scale, as many times as you like, just by clicking a button. And voilà, a new digitally created Flettner Fl-282 Kolibri model is ready to be forwarded to the 3D replicator and become an actual physical object under 1/18 scale, within short time.















Düzenleyen Nick_Karatzides - 27/07/2018 Saat 12:07

The biggest part of the kit are the 4 rotor blades measuring approx 28 cm long each. The fuselage was CAD designed such way and later 3D printed into two main section parts with all included truss-type welded tubes and drive shaft rods with universal joints inside. That was mostly preferred for me, because all basic parts should be accurately pre-installed in place without any glue, putty, sanding etc. On the other hand, that could arise some minor difficulties while painting, but I think that proper masking & airbrushing could lead on good results.











Düzenleyen Nick_Karatzides - 27/07/2018 Saat 12:08

This is the 3D design of one of the two rotor heads, equipped with vibration dampers “pots” on the blade roots. Each one of the separately 3D printed rotor blades, will be later attached on the blade root connecting hinges and the outcome will be installed on gearbox shafts, having an included angle of 24° between the two rotor heads and an inclination forward of 6°.





Totally four seat frames produced. One for the single seat V6, another two for the double seater V21 model and an additional one for spare in case something breaks. These seat frames are only 0.6 mm thick and proved to be much stronger than expected.





The main instrument panel with opened areas for gauges and 0.2 mm embossed detail around it to simulate the support bezels. Each gauge was 3D printed separately and will be added later, after placing the proper water slide decals.





Most of available B&W and some coloured (during evaluation flights in USA) photographs are not detailed enough to reveal if the landing gear wheels had engraved tread grooves (and how many) or embossed lugs running circumferentially around the tire. The Fl-282 wheels found nowadays in museums could not be considered as a reliable reference, because the original tires could not last after 70+ years and would probably be replaced by other similar size & shape. Anyway, since I was aware for the exact 350x150 mm size for the nose wheel and 465x165 mm size for the main gear tires, I created a set of wheels, which looked realistic to me. Also, in most pictures the helicopters seemed to have slightly conical shaped caps installed over wheel rims, but there are also some pictures revealing uncovered wheel rims. Having these photos in mind plus some diagrams of Fl-282’s undercarriage system, I thought that it would be quite interesting and challenging to present the wheels without rim caps.





The two 25 litres cylindrical fuel tanks mounted externally on both sides of the pilot seat, were designed such way to get 3D printed as hollow parts and be presented with lids open to show the interior area.





Düzenleyen Nick_Karatzides - 27/07/2018 Saat 12:09

Some additional parts unrelated to the helicopter structure, also designed to get 3D printed later and be used later as part of a diorama scene. For example a couple of 200 litres fuel drums (also known as 55 gallons drums in USA) and few 20 litres (4.4 imp gal; 5.3 US gal) “Jerrycan” fuel canisters (originally called “Wehrmacht einheitskanister”) designed in Germany during 1930ies for military use. These fuel drums & canisters used by Wehrmacht, Luftwaffe & Kriegsmarine during WWII had the “Kraftstoff 200L Feuergefährlich Luftwaffe” and the “Kraftstoff 20 L Feuergefährlich 1941” inscriptions, engraved or embossed on side. Actually it took only 15 minutes of CAD work on my laptop to have this result under 1/18 scale. As previously described, the CAD file can be easily scaled up or down to reach the desired dimensions, with few mouse clicks only and later be 3D printed under any scale. Yes, I could scratchbuild some WWII Wermacht style fuel drums or canisters with my own hands, using metal foil or by vaccumforming styrene sheet, or simply by solid epoxy putty, but it would take much more time and I would surely get some dirt under my nails. The easier, the better! Actually, I’m not really sure if the handmade result would be so accurate in scale or if I could possibly build it within few minutes only. Notice that the fuel drum & canisters are not solid - they were CAD designed such way (width of skin is about 0.3 to 0.4 mm), aiming both to represent as closely as possible to real ones and also could be later filled with transparent resin material to simulate liquid fuel, always visible through the opened filler cap.















At last, a final piece also 3D designed to be used as a wooden 3-steps ladder as used by Luftwaffe WWII ground crews and technician personnel for ground vehicle & aircraft maintenance procedures.







Düzenleyen Nick_Karatzides - 27/07/2018 Saat 12:11

Shortly thereafter, the 3D printing proceeding outcome pleased me while watching the Mbytes, magically converting into actual physical objects. Yeah, that’s what I call “cool gadgets” on a scale modeler’s service. As soon as 3D printing process completed, the produced parts were cleaned & checked for broken parts or imperfections by Shapeways 3D printing lab specialized personnel. Later, everything carefully packed and shipped to my home address using UPS 24hrs delivery service. Next day, I got home to find a Shapeways box on my doorstep. After a long eye roll from my wife, I quickly grabbed a knife and opened it like all kids open their presents on Christmas morning. Nothing out of the ordinary, I decided to take a few photos to illustrate the experience of receiving my own custom designed & 3D printed model kits package and get in my hands the result of my very own custom-made kit, designed with laptop mouse clicks only and built from zero by converting a CAD binary file into an actual physical object, under my preferable 1/18 scale. Cool stuff, isn’t it?











Düzenleyen Nick_Karatzides - 27/07/2018 Saat 12:12