Intro to K-8
As Kamov settled his OKB down after its forced evacuation from Moscow in late 1941 he realised that his A-7 and AK autogiros were at the bottom of Stalin’s priority list for aircraft. Despite pleas for support these were not forthcoming and after some desultory work Kamov’s design and production staffs were disbanded in 1943. Within two years, as the war ended, he resolutely gathered together some of his erstwhile colleagues and began work on what is sometimes sportively called his Vozdushnyi Mototsiki (Flying Motorcycle). The dimensions and weight of this machine were such that it could be operated from ships. This fact intrigued the Soviet Navy and Merchant Navy who saw in it respectively an excellent observation platform for military purposes and the location of whales and various obstructions. It was to incorporate the distinctive design feature common to all but one of his subsequent helicopters: two co-axial, contra-rotating rotors. Such a configuration was hardly an innovation — Sikorsky, d’Ascanio, Breguet-Dorand and others had all used it — but it was still the best way to counter torque although demanding a heavy and complex transmission.
First K-8 Helicopter
Kamov’s intention was to build the simplest single-seat helicopter that man could devise. To a modified 27 hp M-76 ( BMW) two-cylinder motorcycle engine, an as uncomplicated transmission as he could design to two three-bladed contra-rotating rotors, a fuel tank and a tubular steel framework mounted on two flotation bags, he added one luxury: a seat for the dubious pilot. Originally designated the K-17 Vertolet (Helicopter), the Ka-8 helicopter, as the machine came to be called later, weighed just 183 kg (403 lb) empty. In accordance with traditional motorcycle practice the flying controls consisted of handlebars: push them forward for forward flight, sideways for lateral flight and rotate them for turns. This system was a complete failure and Mikhail Gurov, the test pilot, soon let it be known that he preferred a less frivolous arrangement. Conventional controls were substituted. The throttle was placed on the starboard side with the collective lever attached to the seat. For directional control rudder pedals were installed. The machine boasted only two instruments: an airspeed indicator and an rpm tachometer. The first was quickly seen to be superfluous, merely adding unwanted weight: the engine was simply not powerful enough to lift the ‘motorcycle’ off the ground with its rider in attendance and sufficient fuel to do anything useful.
For the first test the Ka-8 was tethered to the ground by ropes. Gurov climbed aboard and started the engine. In the words of Vladimir Barshevsky, Kamov’s chief engineer: “The engine roared and the Ka-8 vibrated but it showed no inclination to leave the ground. We then siphoned off most of the fuel, removed several accessories, including the airspeed indicator, and Gurov tried again, revving the engine for all it was worth. But still the Ka-8 would not budge. In fact, it was not until Gurov had climbed from the seat leaving the engine running that the Ka-8 left the ground, fortunately restrained by the ropes. We had a helicopter but it would only take-off without the pilot!”
K-8 upgrades and crash
Eventually in 1947 a few extra horsepower – another 17.8 to be exact – were coaxed out of the engine by changing the cylinder heads, plugs and carburettor, and beefing up the compression ratio. This enabled the helicopter to take along Gurov with it and attain a hover ceiling of 4m (13ft) and a maximum speed of 80 km/h (50mph). Intensive flight testing took place during the winter of 1947/48 resulting in numerous modifications. The groaning engine one day failed at 79 m (260 ft) and the machine was damaged after an autorotational descent: two of the rotor blades snapped and the structure was badly distorted. Fortunately Gurov escaped with minor injuries. The Ka-8 was rebuilt.
The K-8 Loser
The heat of the summer in 1948 was such that the rotor blades could not provide sufficient lift for the machine to climb. Power was enhanced by using a mixture of alcohol and petrol, called by Barshevsky Spirtzin. The drawback was that the plugs had to be changed after every flight. However, it was found possible to demonstrate the machine publicly at Tushino in July 1948. The performance stunned the onlookers who were amazed by the manoeuvrability of the Ka-8 and its ability to take-off and land on the back of a lorry. Although two more examples were built it had become quite clear that this helicopter was not going far, either figuratively or physically. The Kamov bureau had not really succeeded in building a true Vozdushnyi Mototsikl but many important lessons had been learned. The engine designer, Aleksandr Ivchenko, was now invited to develop a more powerful engine for the Ka-8. The four cylinders AI-4V of 55 hp, however, was rather too grand for the humble Ka-8 and the Ka-10 had to be designed to incorporate it.