The Grigorovich MR-5 flying boat was built at Factory No.22 and in the summer of 1929 it was sent to Taganrog for testing. During its development it was found that the hull behaved correctly in the water, but during takeoff operations a large curtain of water formed in front of the plane, which made the process difficult. The take-off run distance was also getting too long. The commission that studied the possible destiny of the model concluded on December 1, 1929, that the problems were due to a bad design of the bow section of the hull.
Grigorovich had been arrested, so trying to save the model, the development was transferred at the beginning of 1930 to the construction bureau OPO-4, directed by the Frenchman Paul Aimé Richard . The development was included in the KB ‘s work plan for the year, but very little attention was paid there to improving one design created by another, so finally, at the time of Richard ‘s departure from the USSR , the MR-5 had received no attention.
The need for reconnaissance flying boats was great so in 1931 the MR-5 was delivered to the new TsKB of Factory No.39, where the head of the naval department IV Chetverikov was in charge of the modifications to achieve better behavior in the water.
For this purpose Chetverikov decided to build a new wooden hull with better lines and the empennage underwent modifications, increasing its area. The new model was numbered 10 within the TsKB designations, but was generally known as the Chetverikov MR-5bis (Russian: Четвериков МР-5бис/ЦКБ-10).
In January 1932 Chetverikov read a report that the tests of the TsKB-10 had started, but at that time it referred only to the tests on skis. The complete cycle of tests was completed by the summer of 1932, being developed in the section of the Moscow River where the Gorky Central Park of Culture and Rest (TsPKO) is located today.
In these tests, the hull behaved positively, noting a noticeable decrease in splashes. Despite this, the long-awaited serial production was not approved. The Italian Savoia S-62 flying boat, which had entered service with the VVS RKKA under the designation MR-4, was successfully produced in the Taganrog workshops. Only the on MR-5bis was built.
The MR-5bis differed fundamentally from the original model in its new hull
In some sources Grigorovich ‘s original model has been named as MR-3 and Chetverikov’s version as MR-3bis. This presumably constitutes an error, which has become widespread on multiple sites on the internet that reference these sources. The searches carried out by the Soviet researcher M. Maslov in the original documents of the time show that the term MR-3 was used only to designate the reconnaissance flying boat ROM-1 and MR-3bis designated the improved version ROM-2.
Type: MR-5bis
Powerplant: 1 x 680/500 hp M-17
Wingspan: 15.60m
Wing area: 53.00 m²
Length: 11.40m
Empty weight: 2050kg
Maximum takeoff weight: 3100 kg
Wing loading: 59.0 kg/m²
Power Load: 6.2kg/hp
Fuel + oil load: 440+30 kg
Full load capacity: 1050kg
Top speed: 190km/h
Cruising speed: 162km/h
Landing speed: 85km/h
Practical range: 720 km
Endurance: 4 hours
Practical ceiling: 4000 m
Landing Time: 22s
Take off time: 35s
Accommodation: 2
All Aero 