1:72 Rostov Tilt Rotor Aircraft Company РТАК-30 (NATO ASCC code “Hemlock”); 3rd prototype "33 Yellow" during state acceptance trials; Zhukovsky (Moscow Oblast), 1987 (Whif/kitbashing)
+++ DISCLAIMER +++
Nothing you see here is real, even though the conversion or the presented background story might be based on authentic facts. BEWARE!
The РТАК-30 attack vintoplan (also known as vintokryl) owed its existence to the Mil Mi-30 plane/helicopter project that originated in 1972. The Mil Mi-30 was conceived as a transport aircraft that could hold up to 19 passengers or two tons of cargo, and its purpose was to replace the Mi-8 and Mi-17 Helicopters in both civil and military roles. With vertical takeoff through a pair of tiltrotor engine pods on the wing tips (similar in layout to the later V-22 Osprey) and the ability to fly like a normal plane, the Mil Mi-30 had a clear advantage over the older models.
Since the vintoplan concept was a completely new field of research and engineering, a dedicated design bureau was installed in the mid-Seventies at the Rostov-na-Donu helicopter factory, where most helicopters from the Mil design bureau were produced, under the title Ростов Тилт Ротор Авиационная Компания (Rostov Tilt Rotor Aircraft Company), or РТАК (RTRA), for short.
The vintoplan project lingered for some time, with basic research being conducted concerning aerodynamics, rotor design and flight control systems. Many findings later found their way into conventional planes and helicopters. At the beginning of the 1980s, the project had progressed far enough that the vintoplan received official backing so that РТАК scientists and Mil helicopter engineers assembled and tested several layouts and components for this complicated aircraft type.
At that time the Mil Mi-30 vintoplan was expected to use a single TV3-117 Turbo Shaft Engine with a four-bladed propeller rotors on each of its two pairs of stub wings of almost equal span. The engine was still installed in the fuselage and the proprotors driven by long shafts.
However, while being a very clean design, this original layout revealed several problems concerning aeroelasticity, dynamics of construction, characteristics for the converter apparatuses, aerodynamics and flight dynamics. In the course of further development stages and attempts to rectify the technical issues, the vintoplan layout went through several revisions. The layout shifted consequently from having 4 smaller engines in rotating pods on two pairs of stub wings through three engines with rotating nacelles on the front wings and a fixed, horizontal rotor over the tail and finally back to only 2 engines (much like the initial concept), but this time mounted in rotating nacelles on the wing tips and a canard stabilizer layout.
In August 1981 the Commission of the Presidium of the USSR Council of Ministers on weapons eventually issued a decree on the development of a flyworthy Mil Mi-30 vintoplan prototype. Shortly afterwards the military approved of the vintoplan, too, but desired bigger, more powerful engines in order to improve performance and weight capacity. In the course of the ensuing project refinement, the weight capacity was raised to 3-5 tons and the passenger limit to 32. In parallel, the modified type was also foreseen for civil operations as a short range feederliner, potentially replacing Yak-40 and An-24 airliners in Aeroflot service.
In 1982, РТАК took the interest from the military and proposed a dedicated attack vintoplan, based on former research and existing components of the original transport variant. This project was accepted by MAP and received the separate designation РТАК-30. However, despite having some close technical relations to the Mi-30 transport (primarily the engine nacelles, their rotation mechanism and the flight control systems), the РТАК-30 was a completely different aircraft. The timing was good, though, and the proposal was met with much interest, since the innovative vintoplan concept was to compete against traditional helicopters: the design work on the dedicated Mi-28 and Ka-50 attack helicopters had just started at that time, too, so that РТАК received green lights for the construction of five prototypes: four flyworthy machines plus one more for static ground tests.
The РТАК-30 was based on one of the early Mi-30 layouts and it combined two pairs of mid-set wings with different wing spans with a tall tail fin that ensured directional stability. Each wing carried a rotating engine nacelle with a so-called proprotor on its tip, each with three high aspect ratio blades. The proprotors were handed (i.e. revolved in opposite directions) in order to minimize torque effects and improve handling, esp. in the hover. The front and back pair of engines were cross-linked among each other on a common driveshaft, eliminating engine-out asymmetric thrust problems during V/STOL operations. In the event of the failure of one engine, it would automatically disconnect through torque spring clutches and both propellers on a pair of wings would be driven by the remaining engine.
Four engines were chosen because, despite the weight and complexity penalty, this extra power was expected to be required in order to achieve a performance that was markedly superior to a conventional helicopter like the Mi-24, the primary Soviet attack helicopter of that era the РТАК-30 was supposed to replace. It was also expected that the rotating nacelles could also be used to improve agility in level flight through a mild form of vectored thrust.
The РТАК-30’s streamlined fuselage provided ample space for avionics, fuel, a fully retractable tricycle landing gear and a two man crew in an armored side-by-side cockpit with ejection seats. The windshield was able to withstand 12.7–14.5 mm caliber bullets, the titanium cockpit tub could take hits from 20 mm cannon. An autonomous power unit (APU) was housed in the fuselage, too, making operations of the aircraft independent from ground support.
While the РТАК-30 was not intended for use as a transport, the fuselage was spacious enough to have a small compartment between the front wings spars, capable of carrying up to three people. The purpose of this was the rescue of downed helicopter crews, as a cargo hold esp. for transfer flights and as additional space for future mission equipment or extra fuel.
In vertical flight, the РТАК-30’s tiltrotor system used controls very similar to a twin or tandem-rotor helicopter. Yaw was controlled by tilting its rotors in opposite directions. Roll was provided through differential power or thrust, supported by ailerons on the rear wings. Pitch was provided through rotor cyclic or nacelle tilt and further aerodynamic surfaces on both pairs of wings. Vertical motion was controlled with conventional rotor blade pitch and a control similar to a fixed-wing engine control called a thrust control lever (TCL). The rotor heads had elastomeric bearings and the proprotor blades were made from composite materials, which could sustain 30 mm shells.
The РТАК-30 featured a helmet-mounted display for the pilot, a very modern development at its time. The pilot designated targets for the navigator/weapons officer, who proceeded to fire the weapons required to fulfill that particular task. The integrated surveillance and fire control system had two optical channels providing wide and narrow fields of view, a narrow-field-of-view optical television channel, and a laser rangefinder. The system could move within 110 degrees in azimuth and from +13 to −40 degrees in elevation and was placed in a spherical dome on top of the fuselage, just behind the cockpit.
The aircraft carried one automatic 2A42 30 mm internal gun, mounted semi-rigidly fixed near the center of the fuselage, movable only slightly in elevation and azimuth. The arrangement was also regarded as being more practical than a classic free-turning turret mount for the aircraft’s considerably higher flight speed than a normal helicopter. As a side effect, the semi-rigid mounting improved the cannon's accuracy, giving the 30 mm a longer practical range and better hit ratio at medium ranges. Ammunition supply was 460 rounds, with separate compartments for high-fragmentation, explosive incendiary, or armor-piercing rounds. The type of ammunition could be selected by the pilot during flight.
The gunner can select one of two rates of full automatic fire, low at 200 to 300 rds/min and high at 550 to 800 rds/min. The effective range when engaging ground targets such as light armored vehicles is 1,500 m, while soft-skinned targets can be engaged out to 4,000 m. Air targets can be engaged flying at low altitudes of up to 2,000 m and up to a slant range of 2,500 m.
A substantial range of weapons could be carried on four hardpoints under the front wings, plus three more under the fuselage, for a total ordnance of up to 2,500 kg (with reduced internal fuel). The РТАК-30‘s main armament comprised up to 24 laser-guided Vikhr missiles with a maximum range of some 8 km. These tube-launched missiles could be used against ground and aerial targets. A search and tracking radar was housed in a thimble radome on the РТАК-30’s nose and their laser guidance system (mounted in a separate turret under the radome) was reported to be virtually jam-proof. The system furthermore featured automatic guidance to the target, enabling evasive action immediately after missile launch. Alternatively, the system was also compatible with Ataka laser-guided anti-tank missiles.
Other weapon options included laser- or TV-guided Kh-25 missiles as well as iron bombs and napalm tanks of up to 500 kg (1.100 lb) caliber and several rocket pods, including the S-13 and S-8 rockets. The "dumb" rocket pods could be upgraded to laser guidance with the proposed Ugroza system. Against helicopters and aircraft the РТАК-30 could carry up to four R-60 and/or R-73 IR-guided AAMs. Drop tanks and gun pods could be carried, too.
When the РТАК-30's proprotors were perpendicular to the motion in the high-speed portions of the flight regime, the aircraft demonstrated a relatively high maximum speed: over 300 knots/560 km/h top speed were achieved during state acceptance trials in 1987, as well as sustained cruise speeds of 250 knots/460 km/h, which was almost twice as fast as a conventional helicopter. Furthermore, the РТАК-30’s tiltrotors and stub wings provided the aircraft with a substantially greater cruise altitude capability than conventional helicopters: during the prototypes’ tests the machines easily reached 6,000 m / 20,000 ft or more, whereas helicopters typically do not exceed 3,000 m / 10,000 ft altitude.
Flight tests in general and flight control system refinement in specific lasted until late 1988, and while the vintoplan concept proved to be sound, the technical and practical problems persisted. The aircraft was complex and heavy, and pilots found the machine to be hazardous to land, due to its low ground clearance. Due to structural limits the machine could also never be brought to its expected agility limits
During that time the Soviet Union’s internal tensions rose and more and more hampered the РТАК-30’s development. During this time, two of the prototypes were lost (the 1st and 4th machine) in accidents, and in 1989 only two machines were left in flightworthy condition (the 5th airframe had been set aside for structural ground tests). Nevertheless, the РТАК-30 made its public debut at the Paris Air Show in June 1989 (the 3rd prototype, coded “33 Yellow”), together with the Mi-28A, but was only shown in static display and did not take part in any flight show. After that, the aircraft received the NATO ASCC code "Hemlock" and caused serious concern in Western military headquarters, since the РТАК-30 had the potential to dominate the European battlefield.
And this was just about to happen: Despite the РТАК-30’s development problems, the innovative attack vintoplan was included in the Soviet Union’s 5-year plan for 1989-1995, and the vehicle was eventually expected to enter service in 1996. However, due to the collapse of the Soviet Union and the dwindling economics, neither the РТАК-30 nor its civil Mil Mi-30 sister did soar out in the new age of technology. In 1990 the whole program was stopped and both surviving РТАК-30 prototypes were mothballed – one (the 3rd prototype) was disassembled and its components brought to the Rostov-na-Donu Mil plant, while the other, prototype No. 1, is rumored to be stored at the Central Russian Air Force Museum in Monino, to be restored to a public exhibition piece some day.
Crew: Two (pilot, copilot/WSO) plus space for up to three passengers or cargo
Length: 45 ft 7 1/2 in (13,93 m)
Rotor diameter: 20 ft 9 in (6,33 m)
Wingspan incl. engine nacelles: 42 ft 8 1/4 in (13,03 m)
Total width with rotors: 58 ft 8 1/2 in (17,93 m)
Height: 17 ft (5,18 m) at top of tailfin
Disc area: 4x 297 ft² (27,65 m²)
Wing area: 342.2 ft² (36,72 m²)
Empty weight: 8,500 kg (18,740 lb)
Max. takeoff weight: 12,000 kg (26,500 lb)
4× Klimov VK-2500PS-03 turboshaft turbines, 2,400 hp (1.765 kW) each
Maximum speed: 275 knots (509 km/h, 316 mph) at sea level
305 kn (565 km/h; 351 mph) at 15,000 ft (4,600 m)
Cruise speed: 241 kn (277 mph, 446 km/h) at sea level
Stall speed: 110 kn (126 mph, 204 km/h) in airplane mode
Range: 879 nmi (1,011 mi, 1,627 km)
Combat radius: 390 nmi (426 mi, 722 km)
Ferry range: 1,940 nmi (2,230 mi, 3,590 km) with auxiliary external fuel tanks
Service ceiling: 25,000 ft (7,620 m)
Rate of climb: 2,320–4,000 ft/min (11.8 m/s)
Glide ratio: 4.5:1
Disc loading: 20.9 lb/ft² at 47,500 lb GW (102.23 kg/m²)
Power/mass: 0.259 hp/lb (427 W/kg)
1× 30 mm (1.18 in) 2A42 multi-purpose autocannon with 450 rounds
7 external hardpoints for a maximum ordnance of 2.500 kg (5.500 lb)
The kit and its assembly:
This exotic, fictional aircraft-thing is a contribution to the “The Flying Machines of Unconventional Means” Group Build at whatifmodelers.com in early 2019. While the propulsion system itself is not that unconventional, I deemed the quadrocopter concept (which had already been on my agenda for a while) to be suitable for a worthy submission.
The Mil Mi-30 tiltrotor aircraft, mentioned in the background above, was a real project – but my alternative combat vintoplan design is purely speculative.
I had already stashed away some donor parts, primarily two sets of tiltrotor backpacks for 1:144 Gundam mecha from Bandai, which had been released recently. While these looked a little toy-like, these parts had the charm of coming with handed propellers and stub wings that would allow the engine nacelles to swivel.
The search for a suitable fuselage turned out to be a more complex safari than expected. My initial choice was the spoofy Italeri Mi-28 kit (I initially wanted a staggered tandem cockpit), but it turned out to be much too big for what I wanted to achieve. Then I tested a “real” Mi-28 (Dragon) and a Ka-50 (Italeri), but both failed for different reasons – the Mi-28 was too slender, while the Ka-50 had the right size – but converting it for my build would have been VERY complicated, because the engine nacelles would have to go and the fuselage shape between the cockpit and the fuselage section around the original engines and stub wings would be hard to adapt. I eventually bought an Italeri Ka-52 two-seater as fuselage donor.
In order to mount the four engines to the fuselage I’d need two pairs of wings of appropriate span – and I found a pair of 1:100 A-10 wings as well as the wings from an 1:72 PZL Iskra (not perfect, but the most suitable donor parts I could find in the junkyard). On the tips of these wings, the swiveling joints for the engine nacelles from the Bandai set were glued. While mounting the rear wings was not too difficult (just the Ka-52’s OOB stabilizers had to go), the front pair of wings was more complex. The reason: the Ka-52’s engines had to go and their attachment points, which are actually shallow recesses on the kit, had to be faired over first. Instead of filling everything with putty I decided to cover the areas with 0.5mm styrene sheet first, and then do cosmetic PSR work. This worked quite well and also included a cover for the Ka-52’s original rotor mast mount. Onto these new flanks the pair of front wings was attached, in a mid position – a conceptual mistake…
The cockpit was taken OOB and the aircraft’s nose received an additional thimble radome, reminiscent of the Mi-28’s arrangement. The radome itself was created from a German 500 kg WWII bomb.
At this stage, the mid-wing mistake reared its ugly head – it had two painful consequences which I had not fully thought through. Problem #1: the engine nacelles turned out to be too long. When rotated into a vertical position, they’d potentially hit the ground! Furthermore, the ground clearance was very low – and I decided to skip the Ka-52’s OOB landing gear in favor of a heavier and esp. longer alternative, a full landing gear set from an Italeri MiG-37 “Ferret E” stealth fighter, which itself resembles a MiG-23/27 landing gear. Due to the expected higher speeds of the vintoplan I gave the landing gear full covers (partly scratched, plus some donor parts from an Academy MiG-27). It took some trials to get the new landing gear into the right position and a suitable stance – but it worked. With this benchmark I was also able to modify the engine nacelles, shortening their rear ends. They were still very (too!) close to the ground, but at least the model would not sit on them!
However, the more complete the model became, the more design flaws turned up. Another mistake is that the front and rear rotors slightly overlap when in vertical position – something that would be unthinkable in real life…
With all major components in place, however, detail work could proceed. This included the completion of the cockpit and the sensor turrets, the Ka-52 cannon and finally the ordnance. Due to the large rotors, any armament had to be concentrated around the fuselage, outside of the propeller discs. For this reason (and in order to prevent the rear engines to ingest exhaust gases from the front engines in level flight), I gave the front wings a slightly larger span, so that four underwing pylons could be fitted, plus a pair of underfuselage hardpoints.
The ordnance was puzzled together from the Italeri Ka-52 and from an ESCI Ka-34 (the fake Ka-50) kit.
Painting and markings:
With such an exotic aircraft, I rather wanted a conservative livery and opted for a typical Soviet tactical four-tone scheme from the Eighties – the idea was to build a prototype aircraft from the state acceptance trials period, not a flashy demonstrator. The scheme and the (guesstimated) colors were transferred from a Soviet air force MiG-21bis of that era, and it consists of a reddish light brown (Humbrol 119, Light Earth), a light, yellowish green (Humbrol 159, Khaki Drab), a bluish dark green (Humbrol 195, Dark Satin Green, a.k.a. RAL 6020 Chromdioxidgrün) and a dark brown (Humbrol 170, Brown Bess). For the undersides’ typical bluish grey I chose Humbrol 145 (FS 35237, Gray Blue), which is slightly lighter and less greenish than the typical Soviet tones. A light black ink wash was applied and some light post-shading was done in order to create panels that are structurally not there, augmented by some pencil lines.
The cockpit became light blue (Humbrol 89), with medium gray dashboard and consoles. The ejection seats received bright yellow seatbelts and bright blue pads – a detail seen on a Mi-28 cockpit picture.
Some dielectric fairings like the fin tip were painted in bright medium green (Humbrol 101), while some other antenna fairings were painted in pale yellow (Humbrol 71).
The landing gear struts and the interior of the wells became Aluminum Metalic (Humbrol 56), the wheels dark green discs (Humbrol 30).
The decals were puzzled together from various sources, including some Begemot sheets. Most of the stencils came from the Ka-52 OOB sheet, and generic decal sheet material was used to mark the walkways or the rotor tips and leading edges.
Only some light weathering was done to the leading edges of the wings, and then the kit was sealed with matt acrylic varnish.
A complex kitbashing project, and it revealed some pitfalls in the course of making. However, the result looks menacing and still convincing, esp. in flight – even though the picture editing, with four artificially rotating proprotors, was probably more tedious than building the model itself!