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Chetverikov ARK-3 / MP-2

Chyetverikov ARK-3

As early as 1933, while still working at OSGA, Chetverikov had begun the development of a hydrofoil designed to patrol the Arctic areas. As there was no defined technical task, Chetverikov set the goal of obtaining a speed of 300 km / h and a range of 3000 km. Around 1936 the GlavsievMorPuti became interested in this development and decided to contract Chetverikov for its construction. This event marked the emergence of the ARK-3. The objective of the model was Arctic exploration and patrol, liaison with ships, and the transfer of personnel and assets north.
Chetverikov received the necessary funds for development, the allocation of his own production base in Sevastopol and a major change of subordination, moving from the civil structure of the GVF to work under the direction of the State Directorate for the Aeronautical Industry (GUAP).
The Chyetverikov ARK-3 (ARKtichyeskii - arctic) (Russian: Четвериков АРК-3) was a multi-role flying boat designed for Arctic operations. It featured a conventional flying boat hull, with high cantilever wings equipped with floats at mid-span. The two piston engines were mounted in tractor-pusher fashion on a pylon above the fuselage.
The first ARK-3/1 during testing
The ARK-3 was designed as a cantilever high-wing hydrofoil with two Shvetsov M-25 635 hp engines installed in tandem on a pylon located in the center, braced by struts, which were later replaced by rigid uprights. The two engines powered variable pitch VISh (Hamilton Standard) propellers.
The ARK-3 was of mixed construction, with a 14-metre (45.9 ft) long Duralumin stressed skin fuselage; wooden wings of MOS-27 aerofoil section and set at 5° angle; duralumin tubing tail surfaces; and ailerons with fabric covering. The dual control enclosed cockpit housed two pilots sided by side with two gunners/observers in bow and dorsal positions where a 7.62 mm machine gun could be installed. In the first prototype built these areas were simply left open. The second prototype built installed turrets in both positions. Strut-supported wooden floats, at approximately half-span; and a pylon-supported engine nacelle housing tandem radial engines with Townend ring cowlings; completed the structural elements, built with a safety factor of 5.5.
At the beginning of 1936, the construction of the first АРК-3 prototype was finished in Sevastopol Factory No.45, which was tested in the summer of that year, showing quite acceptable results. The tests culminated in September, achieving a speed at sea level of 252 km / h and 2600 meters reached 308 km / h. The flight ceiling was above 7600 meters. Shortcomings were also highlighted: poor design of the bow splash deflectors, weakness in the powertrain. Even a small 0.25 meter wave ran across the entire bow in front of the cockpit and the splashes reached the propellers.
This was considered to be due to the short length of the bow and its narrow width of only 1.7 meters. There were hardly any problems for take-off, but during the landing on the water there were commonly waves that swept over the bow.
Performance was deemed to be good, prompting an order for a second prototype with the fuselage lengthened by 60 centimetres (24 in) to 14.6 metres (47.9 ft) and a slightly enlarged wing chord; this was designated ARK-3-2 and the first prototype was re-designated ARK-3-1 or MP-2 (Mosrkoi Passazhirski or Naval Passenger Transport). The second prototype ARK-3 featured more powerful engines, longer hull, and manual guns fitted in a manual gun turret in the bows and a dorsal sliding hatch. The APK-3/2, already equipped with weapons, was released in May 1938 with two M-25A engines. The weight of this model increased by 400 kg. A production order for five aircraft was placed, with production commencing immediately.
This first model was modified in order to eliminate the defects indicated. Splashes were considerably reduced with the installation of deflector blades forward. The fastening straps of the driving nacelle were replaced by rigid supports.

On 25 April 1937 Russian pilot A.V. Erchov reached a height of 9160 meters with a payload of 1000 kg in the Crimea with a Chetnerikov A.R.K. 3 twin-engine flying boat, so he surpassed the existing world record, which was still held by the Frenchman Bourdin, who took off in 1933 with a load of 1000 kg 8864 m high.

On 14 July 1937 the ARK-3-1 was destroyed following a structural failure when after a sudden landing the engine fell forward causing the death of the pilot; the ARK-3-2 lost its tail in flight and was destroyed exactly one year later.
At that time, five other copies were found in a different state of completion in addition to the prototypes, and the programme was cancelled.
The ARK-3 formed the basis for the MDR-6 (Che-2) hydrocanoa.
ARK-3-1 / MP-2
The first prototype ARK-3 renamed after the second prototype was ordered
Engines: 2 x M-25, 710 hp takeoff / 630 nominal hp
Wingspan: 20.00 m
Length: 14.60 m
Wing area: 59.5 m²
Wing profile: MOS-27
Empty weight: 3,242 kg
Normal takeoff weight: 4787 kg
Overloaded weight: 5800 kg
Oil weight: 150 kg
Fuel weight: 870 kg
Total load capacity: 1545 kg
Wing loading: 83 kg / m²
Power load: 3.4kg / hp
Maximum speed at sea level: 252 km / h
Maximum speed at 2,600 meters: 308 km / h
Landing speed: 105 km / h
Practical ceiling: 7600 m
Range: 3000 km
Endurance: 7 hours
Ascent time to:
1000 m - 3.5 min
2000 m - 7.0 min
3000 m - 10.0 min
4000 m - 14.0 min
5000 m - 18 min
Accommodation: 3
The second prototype ARK-3.
Engine: 2 × Shvetsov M-25A, 544.36 kW (730 hp) takeoff / 650 hp nominal
Wingspan: 20 m (65 ft 7-1/4 in)
Wing area: 59.5 m2 (640 ft2)
Length: 14.6 m (47 ft 11 in)
Empty weight: 3,642 kg (8,029 lb)
Normal takeoff weight: 4787 kg
Overloaded weight: 5800 kg
Fuel weight: 820 kg
Oil weight: 160 kg
Total load capacity: 1958 kg
Wing loading: 94 kg / m²
Power load: 3.8kg / hp
Maximum speed at sea level: 260 km / h
Maximum speed at 2600 m: 320 km/h (199 mph)
Landing speed: 110 km / h
Endurance: 7 hours
Range: 3000 km
Ascent time to:
1000 m - 3.5 min
2000 m - 7.0 min
Service ceiling: 8,500 m (27,890 ft)
Rate of climb: 4.76 m/s (937.4 ft/min)
Crew: 4
Capacity: 10 pax
Armament: 2 x 7.62 mm machine gun
Bombload: 1,100 kg
Designation of the five production aircraft and the initial designation of the first prototype.



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