The Flettner Fl-282 (Hummingbird) was designed from the outset as a two-seater, so that, at the expense of range, an observer could be carried, with obvious benefits in the roles of army and navy spotting and anti-submarine work. The observer was to be accommodated in a seat facing rearwards and positioned behind the rotor shafts, and the design provided for a permissible center of gravity travel which allowed the helicopter to fly with or without the observer without trim changes. The design was finalized by about July 1940 and work began on 30 prototypes and 15 pre-production machines at Flettner's Johannisthal and Bad Tolz factories. Although the alrframes had prototype and pre-production designations, this was in fact the world's first helicopter production program. It would be 1943 before Sikorsky got its R-4 production line underway. For early flight trials, which began in 1941, the first three Fl-282 prototypes were built as single-seaters and had enclosed Plexiglas-paneled cabins, but subsequent machines were built as open two-seaters.

The Fl-282 was powered by the same Siemens-Halske Sh 14A engine used on previous Flettner helicopters. Depending on the source the engine was rated at 150 or 160 horsepower. The radial engine was located in the center fuselage with a wooden bladed fan drawing in cooling air through openings in the fuselage underside. Engine starting was by use of a compressed air tank to engage the engine cylinders via a distributor. A transmission was mounted on the engine crankcase front and changed the direction from horizontal to an axis upward and slightly aft. A driveshaft connected via universal joints, from the engine transmission to an upper gearbox which split the power into two opposite rotating rotor driveshafts. These driveshafts were inclined 12 degrees outward and 6 degrees forward of vertical. The twin two bladed rotors were synchronized to be parallel when they were in the 45 degree position. The blades were attached to the hubs with hinges and friction dampers that allowed a limited range of flapping, but kept the blades from touching.

In order to ensure that power-off autorotation was not lost, the governor was set for a minimum rotor speed of 160 rpm. With the use of his collective-pitch lever, the pilot could override the governor but only to increase rpm. Under certain conditions, self-excited oscillations could occur in the rotor; this phenomenon happened in flight on one occasion when an Fl-282 was being flown with a high collective pitch and the low rotor speed of 140 rpm (compared with the recommended 175 rpm). Vibration became so severe that the pilot prepared to bale out, but, before he could do so, the machine went into autorotation and the vibration ceased.

At the rear end of the fuselage, a horizontal stabilizer was provided for trimming purposes and a fin and rudder of very generous area. This large area was necessary because much of it was ineffective due to the poor aerodynamic shape of the fuselage causing rearwards Row separation and turbulence. Steering of the Fl-282 was by a combination of the rudder and differential collective pitch change on the two rotors, but only the rudder could give steering during autorotation since collective pitch was then ineffective (another reason for the large rudder area).
For lateral control the pilot used rudder pedals which were connected not only to the rudder, but also actuated a differential collective pitch change on the two rotors. This differential collective pitch was not available during autorotation and this absence resulted in the requirement for the large area rudder and vertical tail used on the Kolibri. The rudder pedals were also connected to the steerable nosewheel of the fixed tricycle landing gear. Longitudinal trim was manifested by an adjustable horizontal stabilizer.

The Kolibri had a fuselage constructed of welded steel tubing that was sized so that it could be stowed with rotor blades and landing gear removed in a compact area, 5.9 feet in diameter by 18 feet long, built as a pressure tank for carriage on a U-boat. However there is no evidence that any Fl-282 was deployed on a German submarine. The undercarriage was of the non-retractable tricycle type with the nosewheel connected to the rudder pedals for steering.
The Fl-282 was more highly developed and flew more hours than any other German helicopter, and very extensive tests and measurements were made of all flight aspects. Most of this test work was done by Flettner's chief pilot, Hans E. Fuisting, who also undertook blind lying and trained many of the 50 pilots who learned to fly the Fl-282. Some new pilots ran into trouble when flying near the ground, because, as they turned with the wind, they lost lift and struck the ground. One new pilot had a fatal accident when flying his Fl-282 blind in cloud, and the assumed cause of the accident was that the machine had been dived and the controls then pulled back so violently that the blades were forced into each other or into the tail. The diving speed thereafter was restricted to 175 km/h (109 mph). On occasions, the Kolibri was landed autogyro fashion and without the use of collective pitch. This was done by descending vertically, diving nose- down and then pulling back on the controls to lands but, on one occasion at least, the tail hit the ground and was damaged.

Extremely maneuverable and very stable, even in gusty conditions, the machine could be flown hands-off in forward flight above 60 km/h (37 mph) for indefinite periods by making an adjustment to neutralize the loads on the controls. However, in forward Right at speeds below 60 km/h (37 mph) there was some longitudinal instability which reached a maximum at about 40 km/h (25 mph). Another slight criticism of the Fl-282 was that it vibrated rather badly while the rotor was running up on the ground, but this vibration decreased upon lifting off, although there was still a certain amount of vibration transmitted to the control column, which was sluggish and tended to overshoot the requisite amount of movement. Although many of the mechanical components were unnecessarily complicated and heavy, the general design and workmanship we're of excellent quality, and, as an endurance test, one machine was flown 95 hours in all without replacements or repairs. The engine, which had a long development history, was said to be capable of 400 hours between overhauls.

The first two Fl-282 helicopters had all metal streamlined fuselages with streamline fairings around the rotor masts, and a fully enclosed plexiglass paneled single seat cockpit. The tails were mostly fabric covered. These two machines were designated Fl-282A. Test flying began in 1941 and was conducted by Flettner's (chief Test Pilot, Hans Fuisting.

During 1942, a more productionized version, the Fl-282B-1 was developed. The fuselage was redesigned to use only flat wrapped (no multi-contour) sheet metal covering over the engine compartment, and the aft fuselage became fabric covered. The tail surfaces were redesigned to simplify construction and became entirely fabric covered. The streamline rotor mast fairings were eliminated. This was still a single seater, but now the pilot sat completely in the open. An exception was the third ship which had a nose similar to the first two, but the upper cockpit panels were deleted making it a semi-enclosed cockpit. The airframe weight was reduced by 110 pounds when compared to the Fl-282A, but some of this reduction was added back with the addition of a small bomb bay, a rubber life raft, and mooring gear for shipboard use.

Like the earlier Fl-265, the Fl-282 was designed for shipboard operation and an early production ship was operated from a 13 foot square platform on the Grief, a 2,000 ton aircraft salvage ship. In 1942, the fifth Fl-282 participated in naval trials in the Baltic, operating from a platform on an aft gun turret of the cruiser Koln.

It was no simple matter setting a helicopter down on the heaving deck of a ship, so a special system was designed to bring the two vehicles together. A ten meter 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 throw a switch which would 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, twenty Fl-282s had been built and they were routinely being used by the Kriegsmarine for convoy protection and reconnaissance from ships in the Aegean, Baltic, and Mediterranean Seas. The helicopter was found to be especially valuable at dawn and dusk when pilots of fixed wing aircraft did not have good visual contact in the poor light. During the day observation was especially favorable in the Mediterranean where the clear water allowed the helicopter crews to 'see' submarines as deep as 130 feet. Once a sub was spotted the Kolibri could easily match the speed and course of the submarine task 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 the sub's position to the convoy, and if a warship was dispatched to attack it, the helicopter would mark the target's position with a magnesium flash bomb or a smoke bomb. Unfortunately, little is known of the operational employment of the machine.

The German Army also appreciated the usefulness of the helicopter and ordered a two seat version of the Kolibri, known as the Fl-282B-2. It was similar to the navy ships, but a rear facing seat was fitted in the fuselage behind,the engine. Space for the extra seat and passenger was obtained by remodeling the standard fuel tank and special naval radio equipment. A 25 liter cylindrical fuel tank was mounted an the outside of the fuselage, adjacent to the pilot's cockpit and the long range naval radio was replaced with a smaller and lighter short range radio.

The Fl-282B had a maximum speed of 93 mph. at sea level. Range was 166 miles as B single seater at 71 mph., or 106 miles as a two seater at 68 mph.. Gross weight was 2205 pounds, with useful load of 529 pounds. Maximum rate of climb was 300 feet per minute. with a hover ceiling of 985 feet and a service ceiling of 10,800 feet. The Fl-282B-2 was used for such military tasks as directing artillery fire and guiding tanks over rough terrain. Beginning in 1944, the army began to implement a program to provide a helicopter to each independent artillery brigade.
A combined Army-Navy order for 1,000 Fl-282s was given to Flettner and BMW in 1944. Tooling up was begun, but heavy aerial bombardment of the Flettner and BMW factories resulted in none of these machines being built. Only a total of 25 Kolibris had been manufactured by Flettner at war's end. Luft-Transportstaffel 40 based at Ainring in April 1945, had at least three Fl-282s (and also three Focke Achgelis Fa-223s) at its disposal. during the last few months of the war and this unit 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 Hanke out of besieged Breslau just before the capture of that city.

During 1944, when the Fl-282 was considered fully developed, Anton Flettner turned to the design of the Fl-339, using all the experience gained with the Fl-282. The Fl-339, which never got beyond the project stage, was to have been a much larger helicopter weighing some 3,000 kg (6,615 lb) empty, carrying about 20 passengers and being powered by a single engine.

After the war, only three Fl-282s were discovered by the Allies in a serviceable condition for testing, the Fl-252 V15 and V23 being taken to the USA and a third machine to the USSR. Examples, known to have survived are the Fl-282 (c/n 28368) at the Cranfleld Institute of Technology, and the Fl-282 V23 at the United States Air Force Museum, Dayton, Ohio.

Flettner's intermeshinig rotor concept saw widespread use in a series of postwar helicopters built by. Kaman for the U.S. Navy and Air Force. Anton Flettner moved to the United States in 1947 to work as a consultant to the Office of Naval research and continued his rotary wing research until his death in 1962.

Rotor Diameter - 39 ft 2 3/4"
Maximum Speed - 93 mph
Fuselage Length - 21 ft 6 1/4"
Maximum Diving Speed - 109 mph
Height - 7 ft 2 1/2"
Vertical Rate of Climb - 300 ft per min.
Disc Area - 1.281 sq ft
Hovering Ceiling - 985 ft
Empty Weight - 1,675 lbs
Service Ceiling - 10,800 ft
Loaded Weight - 2,205 lbs
Range - 1 crew 186 miles
Range - 2 crew 112 miles

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