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Mil V-12
The Mil V-12 (NATO reporting name Homer), given
the project number Izdeliye 65, is the largest helicopter ever
built. The designation "Mi-12" would have been the name for the
production helicopter, and was not applied to the V-12
prototypes.
Design studies for a giant helicopter were
started at the Mil OKB in 1959, receiving official sanction in 1961
by the GKAT (Gosudarstvenny Komitet Po Aviatsionnoy Tekhnike -
"state committee on aircraft technology") instructing Mil to
develop a helicopter capable of lifting 20 to 25 t (44,000 to
55,000 lb). The GKAT directive was followed by a more detailed
specification for the V-12 with hold dimensions similar to the
Antonov An-22, intended to lift major items of combat materiel as
well as 8K67, 8K75 and 8K82 inter-continental ballistic missiles
(ICBM).
Design limitations forced Mil to adopt a twin
rotor system but design studies of a tandem layout, similar to the
Boeing CH-47 Chinook, revealed major problems. The single rotor
layouts also studied proved to be non-viable, leading to the
transverse layout chosen for the finished article.
The transverse rotor system of the V-12, which
eliminates the need for a tail rotor, consists of two Mi-6
transmission systems complete with rotors mounted at the tips of
the approximately 30 m (98 ft) span inverse tapered wings. Although
the first use by Mil, the transverse system had been used by
several of the early helicopters, including the Focke-Wulf Fw 61,
Focke-Achgelis Fa 223 Drache and Kamov Ka-22 Vintokryl
convertiplane.
Construction of the V-12 first prototype, after
exhaustive testing with test-rigs and mock-ups including a complete
transmission system, began at Panki in 1965. The airframe was
largely conventional, using stressed skin construction methods with
high strength parts machined from solid. The large fuselage
accommodated the 28.15?4.4?4.4 m (92.4?14.4?14.4 ft) cabin and crew
section in the extreme nose, housing pilot, co-pilot, flight
engineer and electrical engineer in the lower cockpit, with the
navigator and radio operator in the upper cockpit.
At the aft end of the fuselage access to the
cabin is gained by large clamshell doors and drop down cargo ramp
with inbuilt retractable support jacks. Doors in the fuselage also
give access to the cargo hold: two on the starboard side and three
on the port side. Above the rear fuselage is a very large fin and
rudder, with a moderately sized tailplane with dihedral fitted with
end-plate fins (not fitted for the first flight).
The fixed undercarriage consists of large paired
main-wheel units on oleo-pneumatic levered shock absorbers mounted
at the junction of a strut system supporting the rotor systems and
wings and connected to the centre fuselage by a tripod strut
structure with the nose-leg attached aft of the crew section. A
pair of bumper wheels are mounted at the rear of the fuselage keel
and fixed support pads ensure that the cargo ramp is extended to
the correct angle. Long braced struts also connected the
transmission units to the rear fuselage forward of the fin. Cargo
handling is by forklift or electric hoists on travelling beams.
The power system and wings are mounted above the
centre fuselage with interconnecting shafts ensuring
synchronisation of the main rotors which overlapped by about 3 m
(9.8 ft). Drag and lift losses are reduced by the inverse taper
wings with minimum chord in regions of strongest down-wash. The
interconnecting shafts also ensured symmetrical lift distribution
in event of engine failure. To optimise control in roll and yaw the
rotors are arranged to turn in opposite directions with the port
rotor turning anti-clockwise and the starboard rotor turning
clockwise, ensuring that the advancing blades pass over the
fuselage.
Each power unit comprises two Soloviev D-25VF
turbo-shaft engines mounted below main gearboxes which each drive
five-bladed 35 m (115 ft) diameter rotors and the synchronisation
shafts which run from wing-tip to wing-tip. Each paired engine pod
has large access panels which open up for maintenance access and
also form platforms for servicing crews to operate from.
Control of the V-12 presented several problems
to the designers and engineers due to the sheer size as well as the
rotor layout. The pilot and co-pilot sat in the lower flight deck
with a wide expanse of windows to give excellent visibility. Using
conventional cyclic stick, collective lever and rudder pedals the
pilots input their commands in a conventional fashion. Roll control
is by differential collective pitch change on the left and right
rotors, ensuring that sufficient lift is generated to prevent
inadvertent sink. Yaw in the hover or low air speeds is achieved by
tilting the rotor discs forward and backward deferentially
depending on direction of yaw required. At higher air speeds
differential rotor control is gradually supplanted by the large
aerodynamic rudder on the fin. Ascent and descent are controlled by
the collective lever increasing or decreasing pitch of both rotors
simultaneously. Large elevators on the tailplane control fuselage
attitude and provide reaction to pitching moments from the wing and
variation on rotor disc angle.
The control system is complex due to the sheer
size of the aircraft and the need to cater for aeroelastic
deformation of the structure, as well as the very large friction
loads of the control rods, levers etc.. To keep control forces felt
by the pilots to a minimum the control system is in three distinct
phases. Phase one is direct mechanical control from pilot inputs
which is fed into phase two. Phase two is the intermediate powered
control system with low powered hydraulic boosters transferring
commands to the third phase. Phase three is the high powered rapid
action control actuators at the main gearboxes operating the
swashplates directly.
Construction of the first prototype was
completed in 1968. A first flight on 27 June 1967 ended prematurely
due to oscillations caused by control problems; one set of main
wheels contacted the ground hard bursting a tyre and bending a
wheel hub. The cause of the oscillations proved to be a harmonic
amplification of vibrations in the cockpit floor feeding back into
the control column when a roll demand was input into the cyclic
stick. It was widely but erroneously reported in the Western press
that the aircraft had been destroyed.
The first prototype, given the registration
SSSR-21142, made its first flight on 10 July 1968 from the Mil
factory pad in Panki to the Mil OKB test flight facility in
Lyubertsy. In February 1969, the first prototype lifted a record
31,030 kg (68,410 lb) payload to 2,951 m (9,682 ft). On 6 August
1969, the V-12 lifted 44,205 kg (97,455 lb) to a height of 2,255 m
(7,398 ft), also a world record.
The second prototype was also assembled at the
Mil experimental production facility in Panki but sat in the
workshop for a full year awaiting engines, flying for the first
time in March 1973 from Panki to the flight test facilities in
Lyubertsy. Curiously the second prototype was also registered
SSSR-21142.
The prototype V-12s outperformed their design
specifications, setting numerous world records which still stand
today, and brought its designers numerous awards such as the
prestigious Sikorsky Prize awarded by the American Helicopter
Society for outstanding achievements in helicopter technology. The
V-12 design was patented in the USA, Great Britain and other
countries.
Despite all of these achievements the Soviet Air
Force refused to accept the helicopter for state acceptance trials
for many reasons, the main one being that the V-12´s most important
intended mission no longer existed, i.e. the rapid deployment of
strategic ballistic missiles. This also led to a reduction in
Antonov An-22 production.
In May–June 1971, the first prototype V-12
SSSR-21142 made a series of flights over Europe culminating in an
appearance at the 29th Paris Air Show at Le Bourget wearing exhibit
code H-833.
V-12 No.1 at the Mil Helicopter Plant in Panki. Note that the rotor
blades are removed.
All development on the V-12 was stopped in 1974.
The first prototype remained at the Mikhail Leontyevich Mil Moscow
helicopter plant in Panki-Tomilino, Lyuberetsky District near
Moscow and is still there today (17 August 2013) at 55°40?2?N
37°55?56?E. The second prototype was donated to Monino Air Force
Museum 50 km (31 mi) east of Moscow for public display.
World records
Records are certified by the Federation
Aeronautique Internationale. The V-12 first prototype has held
eight world records, four of which are still current, in the FAI E1
General class for rotorcraft powered by turbine engines. The
aircraft was crewed by:
22 February 1969
Pilot - Vasily Kolochenko
Crew - L.V. Vlassov, V.V. Journaliov, V.P. Bartchenko, S.G.
Ribalko, A.I. Krutchkov
6 August 1969
Pilot - Vasily Kolochenko
Crew - L.V. Vlassov, V.V. Juravlev, V.P. Bartchenkov, S.G. Ribalko,
A.I. Krutchkov
Variants:
V-12
OKB designation of the two prototypes of the proposed Mi-12
production version.
Mi-12
Designation reserved for the expected production version.
Mi-12M
A further proposed refinement of the V-16 with two 15,000 kW
(20,000 hp) Soloviev D-30V (V - Vertolyotny - helicopter)
turboshafts driving six bladed rotors, to transport 20,000 kg
(44,000 lb) over 500 km (310 mi) or 40,000 kg (88,000 lb) over 200
km (120 mi). The M-12M was cancelled at the mock-up stage when the
V-12 development programme was cancelled.
Specifications (V-12)
General characteristics:
Crew: 6 (pilot, copilot, flight engineer, electrician,
navigator, radio operator)
Capacity: 196 passengers
normal 20,000 kg (44,000 lb)
maximum 40,000 kg (88,000 lb)
Length: 37 m (121 ft 5 in)
Wingspan: 67 m (219 ft 10 in) across rotors
Height: 12.5 m (41 ft 0 in)
Empty weight: 69,100 kg (152,339 lb)
Gross weight: 97,000 kg (213,848 lb)
Max takeoff weight: 105,000 kg (231,485 lb)
Freight compartment: 28.15?4.4?4.4 m (92.4?14.4?14.4 ft)
Powerplant: 4 ? Soloviev D-25VF turboshaft engines, 4,800 kW (6,500
shp) each
Main rotor diameter: 2? 35 m (114 ft 10 in)
Main rotor area: 962 m2 (10,350 sq ft) 5-bladed rotors located
transversely
Performance
Maximum speed: 260 km/h (162 mph; 140 kn)
Cruising speed: 240 km/h (149 mph; 130 kn)
Range: 500 km (311 mi; 270 nmi)
Ferry range: 1,000 km (621 mi; 540 nmi) with external fuel
tanks
Service ceiling: 3,500 m (11,483 ft)
Disk loading: 50.5 kg/m2 (10.3 lb/sq ft) at gross weight
Hovering ceiling in ground effect: 600 m (2,000 ft)
Hovering ceiling out of ground effect: 10 m (33 ft)
Avionics
AP-44 autopilot
VUAP-2 EXPERIMENTAL AUTOPILOT
ROZ-1 Lotsiya weather and navigational radar
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