Mil Wed-12
| Mil Mi-12 (W-12) | |
|---|---|
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| Type: | Experimental helicopter |
| Design country: | |
| Manufacturer: | |
| First flight: |
July 10, 1968 |
| Commissioning: |
Development stopped in 1974 |
| Number of pieces: |
2 |
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The Soviet Mil Mi-12 ( Russian Миль Ми-12 , NATO code name "Homer" ) is the largest helicopter ever built . The actual name is W-12 (for Wertoljot, helicopter), but is often replaced in publications by the abbreviation of the chief designer Mil . However, since this was only officially used when a model was transferred from its design office to series production, but the W-12 remained a prototype, the designation Mi-12 is incorrect. Mils employees also referred to the type as "Slon" (elephant) or as a reference to the predecessor Mi-6 as "Double Six".
The Mi-12 is a helicopter with two side, counter-rotating rotors , which means that no tail rotor is required. There are two shaft turbines on each side arm , which, like the rotors , were borrowed from the Mil Mi-6 , which with just one of these rotors is one of the largest transport helicopters in the world. The first flight of the Mi-12 was on July 10, 1968.
history
As early as 1959, Mil designed concepts for an “ultra-heavy-duty helicopter” under the project name W-12 or “Isdelije (product) 65 (Изделие 65)”. In 1961 the OKB got the official order to construct a helicopter that should be able to lift a weight of 20 to 25 tons. This was later supplemented by the Council of Ministers directive that the helicopter should have a cargo volume similar to that of the Antonov An-22 . This cargo volume (4.40 m high, 4.40 m wide and 28.15 m long) was also required to transport ICBMs with nuclear warheads of the type 8K67 (Scarp). Up to this point in time (1961), the rockets with a total weight of more than 20 tons (unfueled) were tied to rail transport. This made enemy aerial reconnaissance of the locations of Soviet ICBMs relatively easy. Like almost all technical constructions from the time of the Soviet Union, the W-12 also had to cover the requirements of large construction projects and be usable in geo-exploration. When it comes to the usefulness of such a helicopter, which can transport heavy loads over a distance of up to 1000 kilometers without a runway, roads or rails, different standards are to be applied than in Central Europe or North America, for example , against the background of the undeveloped expanse of Siberia .
Until 1965 they worked on the designs and models under the direction of Genrich W. Remissow. A 1: 1 model was required to test the engines, controls and rotor dynamics. The construction, which resembled a railroad car with two engines and helicopter rotors, was built together with another 1: 1 model for the design of the fuselage and cargo space. These models were presented to the client in April 1965. Loading and unloading with 36 heavy-duty war machines were tested in the cargo hold model. After a positive inspection and evaluation of the work results, the order was placed in 1966 to design the first airworthy prototype. At the same time, the aircraft factory No. 292 in Saratow with preparations for series production of the first five machines.
In the summer of 1967 the first prototype was ready for use and could be used for flight tests. However, an incident occurred during the planned first flight of the prototype in Panki on June 18, 1967 in the presence of the military. Shortly after take-off, the helicopter, controlled by the chief test pilot Vasily Koloshenko, got into a partially uncontrollable flight state just above the ground and after 23 seconds hit the ground hard with the left main landing gear, the two tires bursting and the undercarriage being compressed. As was later found out, natural vibrations and resonances in the cockpit and fuselage were the reason why the pilot could not avoid unintentional steering movements. However, this problem could be remedied relatively quickly using damping measures. On July 10, 1968 Koloshenko was able to carry out the first successful flight, the day has been the official date of the first flight ever since. The further course of the tests turned out to be very successful, a sign of the good theoretical preparatory work of the development team. In December 1968, the first prototype with the registration number СССР-21142 was transferred to the Institute for Flight Tests at the Zhukovsky Air Force Base for flight testing.
According to official reports, there were only two prototypes. According to reports, a prototype crashed in 1969, suggesting the existence of a third machine. However, a crash was never officially confirmed in the Soviet Union media. Two years later, the W-12 was presented to the public on a 3600-kilometer tour through several European countries. Finally, it landed on May 26, 1971 at Paris Le Bourget Airport, where it was exhibited at the 29th Aérosalon . On the return trip, the helicopter and the Tu-144 made a stopover in Berlin-Schönefeld from June 14th to 17th . The designer Michail Mil did not live to see the successful presentation. After the failed first flight in 1967, he was already in poor health and was only able to lead the revision of the project with considerable restrictions. Mil eventually died on January 31, 1970.
A series production of the Mi-12 did not take place anymore. The program was discontinued in 1974. The work on the Mi-12M as a "super-ultra heavy-duty helicopter" with more powerful engines and two by six rotor blades was completed before the actual prototype was built. From a military point of view, the main purpose of the helicopter had become obsolete. The expansion of the silo-based ICBMs was not pursued any further. The Soviet armed forces had had much lighter ICBMs of the type R-29 (SS-8, SS-18, SS-23) since 1969 and, from the beginning of 1975, medium-range missiles of the type RS-16 (SS-17), which were launched by mobile launch pads (all-terrain trucks), ships or submarines could be fired. However, much of the knowledge gained during the construction of the Mi-12 was incorporated into the development of the Mil Mi-26 heavy transport helicopter , which began in the early 1970s. The Mi-26 is now the largest production helicopter in the world and is still in production.
technology
The two engines per rotor, the gearbox and the rotor blades for the Mil Mi-12 were taken from the production of the Mi-6 . In this way, considerable costs could be saved. A separate gearbox was used for each engine to drive the rotor head. The larger rotor diameter was achieved by using longer rotor head shanks. It is the only double rotor configuration Mil has ever built.
The designers originally wanted to arrange the two rotors one behind the other, as is common then and still today for a number of US transport helicopters ( tandem configuration ). With this arrangement, however, there was a risk of sucking in the hot exhaust gases from the front twin engine under unfavorable conditions. This would have led to a sudden loss of power on the rear twin engine and thus endangered the ability to fly. Therefore, the side arrangement was finally implemented. The Mi-12 is the last helicopter to be built with this configuration.
The side assembly of the rotors and the turbines in free-hanging nacelles at the ends of the wings also ensured that the engine components could be easily reached during maintenance work. For this purpose, there is a "roof hatch" on the top of the Mi-12, through which the maintenance personnel can access the top of the machine and the wings. The equipment on board the helicopter also includes a plug-in railing and the necessary hanging platforms for maintenance work on the engine nacelles. Their panels can be opened quickly using a folding mechanism.
The connecting surfaces to the motor nacelles were designed as hydrofoils with ailerons , so that they contributed to the lift in the faster forward flight and improved the maneuverability of the Mi-12 around the roll axis.
Despite the large dimensions, the rotor circles had an overlapping area of about three meters in the middle. In order to prevent contact with the rotors rotating in opposite directions at 112 min −1 and to synchronize the gears and also for balancing power transmission, both rotors were connected to a central shaft. Due to the "kink" in the wing construction, a universal joint in the form of an additional gear inside the fuselage was required. Due to the central shaft and the use of twin engines, the Mi-12 remained airworthy even if both engines failed on one side.
The control of the rudder and the rotor blade pitch was taken over by three independent hydraulic systems, each of which consisted of a main and a replacement component. The Mi-12 was also equipped with the latest electronic developments of the time, including weather radar and autopilot.
Records and whereabouts
Various records were set with the Mi-12. Among other things, the Mi-12 lifted a record load of 31,030 kg to 2,951 m on February 22, 1969. On August 6, 1969, the crew Vasili Kolochenko reached a height of 2,000 m with a payload of 40,204.5 kg and 2,255 m with a payload of 35,000 kg. In theory and in practice, the Mi-12 could carry even heavier loads at a lower altitude (greater air density). By "rolling" the helicopter on the runway, the lift under the wings was even used. However, nothing is known about the payloads moved during these “heavy load experiments”.
The public demonstrations of the Mi-12, as well as in Copenhagen , Groningen and Le Bourget in 1971 , flew a machine with the registration number СССР-21142 / H-833 . Here, it was the first of the two prototypes, the forward to the site of the Michail Leontievich--Mil -Hubschrauberfabrik in Ljuberzy is -Panki near Moscow ( 55 ° 40 ' N , 37 ° 56' O ).
Another still preserved Mi-12 can be seen in the Central Museum of the Air Force of the Russian Federation in Monino (about 50 km east of Moscow). This is likely the second prototype. Most of the images in this article are from this machine that no longer has a registration number; a display also gives 1967 as the year of manufacture.
Technical specifications
| Parameter | Data |
|---|---|
| crew | 6–10 (pilot, co-pilot, navigator, flight engineer, radio operator, 1–5 electricians) |
| Passengers | 196 |
| Rotor diameter | each 35.00 m |
| overall length | 37.00 m |
| Span with rotors | 67.00 m |
| height | 12.50 m |
| Cabin (length × width × height) |
28.15 m × 4.40 m × 4.40 m |
| Empty mass | 69,100 kg |
| payload | normal 20,000 kg maximum 40,000 kg |
| Takeoff mass | normal 97,000 kg maximum 105,000 kg |
| drive | four wave turbines Solovyov D-25WF |
| Starting power: | 4 × 4,800 kW (4 × 6,500 WPS ) |
| Top speed | 260 km / h |
| Cruising speed | maximum 240 km / h economical 200 km / h |
| Service ceiling | 3,500 m |
| Range | 1,000 km 500 km with a 25,000 kg payload |
See also
literature
- Heinz A. F. Schmidt: Airplanes from all over the world. Volume IV . Transpress, Berlin 1973, p. 133 .
Web links
Individual evidence
- ^ Karl-Heinz Eyermann: The elephant - the double six. In: Flieger Revue 11/82. Pp. 506-511.
- ↑ Youtube: Video of the first flight in 1968 and from the Paris Aviation Salon in 1971
- ^ Heinz A. F. Schmidt: Aviation data from March 1971 to February 1972 . In: Flieger-Jahrbuch 1973 . Transpress, Berlin 1972, p. 164 .
- ^ Heinz A. F. Schmidt: Aviation data from March 1, 1969 to February 28, 1970 . In: Flieger-Jahrbuch 1971 . Transpress, Berlin 1970, p. 165 .