According to Shavrov the Grigorovich M-8 (Russian: Григорович М-8) was a new prototype on the way to the M-9, in which the contours of the hull were once again modified with a higher recess (about 150 mm). In this case the prototype did not even manage to take off from the water.
AO Alexandrov handles another theory since the following statement appears in a Navy document dated October 26, 1915:
“Currently at the Schetinin factory two large experimental flying boats with increased range are being built. At this time one of them (the minor) is ready and is in the testing stage…”
According to Alexandrov this document refers to the M-7 and M-8 models.
The idea of creating the M-8 as a large flying boat with a long range could respond to a request from the pilots of the Baltic Fleet. In the Naval General Staff, many plans related to naval aviation were related to the giant models of Igor Sikorski and their possible modification to navalized versions. Unfortunately, the only example of the Ilya Múromets bomber in floatplane configuration with floats was destroyed by an accident caused by its pilot’s error during landing in the first days of the war.
At the end of July or beginning of August 1915 D. P. Grigorovich presented to the Aviation Committee of the Baltic Fleet the project of a biplane and twin-engine flying boat with an empty weight of 3.1 tons and a payload capacity of 2 tons. The large fuel capacity (970 kg) allowed it a range of 8 hours of flight at cruise power from its 600 total hp engines. The calculated speed was about 105 km/h.
On August 12, the military pilots supported the idea and proposed giving the aeronautical manufacturer an advance of 50% of the value requested to start the construction of the experimental prototype. The other 50% would be delivered once the specimen was finished and successfully tested, considering that the data presented could only reach a deviation of 10% with respect to the calculated ones.
On August 22, Captain 2nd Rank BP Dudorov, Head of the Aviation Department of the Baltic Sea Liaison Service , approved the idea, but expressed his disagreement with the proposed form of payment. Instead he proposed that the firm apply for a loan and deliver the engines of the requested power.
Everything indicates that SS Shchetinin put great hopes in the project, for which he ordered to start its construction at risk. It was also oriented to expand the factory with new workshops capable of accommodating large flying boats under its roof.
According to a report from the Naval General Staff (MGSh), issued on September 24, the model was built with two 220 hp engines, which would allow a horizontal speed of 95 km/h with a climb of 2,000 meters in 30 minutes. Cargo capacity was also reduced to only 1.7 tons, including crew, weapons and fuel capacity for 7 hours of patrolling. Neither the Navy nor the company were able to obtain the long-awaited 300-hp engines, but hope remained that they could be delivered before construction of the prototype was completed.
From then on, all the evidence that could link the fate of the M-8 disappears. Probably the requested power plant could not be obtained and the performance with the 220 hp engines ceased to be of interest to the Navy, but these are only guesses.
In a paper presented to a meeting of the Imperial Flying Club on November 25, 1915 , AO Alexandrov found some technical data on an airplane that he associated with the M-8. These data are the following:
Number of motors: 2
Total power: 600 hp
Take-off weight: 5100kg
Payload Capacity: 2000kg
Endurance: 8 hours
Fuel weight for 10 hours of flight: 970 kg
Armament weight in 5-hour flight: 650 kg
Armament weight in 10-hour flight: 135 kg
Crew: 5 people
Speed with maximum load: 105 km/h
Wingspan of upper plane: 33 m
Wingspan of the lower plane: 24 m
Height: 3.8m
Length: 14.6m
All Aero 