The Soviet aircraft designers started actively incorporating the rapidly developing jet technologies into already proven piston-powered fighter designs from the mid-1940s. Various jet engines and boosters were tested on several successful fighters, including the Yak-1, LaGG-3, La-7 and others. For the most part, those designs consisted of liquid fuel rockets and jet motors installed in the tail section of the fuselage for use as boosters. Nevertheless, those projects had both the general problems of early jet engine designs (low thrust, complications in manufacturing) and quite dangerous operational troubles. For instance, usage of liquid fuel necessitated fueling the aircraft with toxic and highly corrosive oxidants that were dangerous to handle at the airfields and caused several incidents in the air during tests.
The next step was to install the jet engines in underwing pylons installed on the fighters. This design was used for the La-9RD.
The first successful experiment with modifying the current fighters was equipping the “130” fighter model with PVRD-430 ramjets. The machine was designated “138” and tested in 1947. Yet it could only be considered successful because there were no significant technical issues. The desired flight parameters were not achieved: to reach maximum thrust, the ramjet required a speed of at least 700 km/h, which the “138” could not achieve. Instead of the expected 70-100 km/h of boost, the ramjets provided only 45 km/h, but consumed so much fuel that the flight range was reduced to a mere 112 km. As a result, the fighter was only capable of operating around airfields and intercepting heavy bombers, but could not counter any potential enemy fighters.
But the experiments continued. Later on, the La-7 was equipped with D-10 pulsejets. Interestingly, those engines were initially developed for the Soviet analogs of the German V-10 rocket (projectile-aircraft in Soviet terminology). The test prototype showed much more promise: with the pulsejets active, it reached speeds 119 km/h higher and was limited by the structural weaknesses of the wings that carried the jets.
Later the project switched to the La-9. The design bureau at plant 51, headed by Vladimir Chelomey, equipped 12 fighters with upgraded D-13 ramjets and prepared 10 of them for the air parade. The motors were installed on pylons fixed to the reinforced wings’ consoles. The additional weight had to compensated in other parts of the fighters, so the armored pilot seats and two cannons were removed, and a 60 kg counterweight was added to the engine reductor to counter changes to the center of gravity. The fuel system was also changed to power fuel pumps and feed the pulsejets. Ten fighters were presented to the country’s leaders and public at the parade in Tushino on 30 August 1947, impressing them with their deafening roar when flying overhead.
One of the 12 modified machines, #48210509, was designated La-9RD and tested from 21 November 1947 till 13 January 1948. With the pulsejets active, the fighter showed 70 km/h increase in maximum speed, but they created a lot of vibration and noise. The motor fittings made aerodynamic parameters significantly worse and piloting, landing and takeoff became difficult. Since the pulsejets used the same fuel as the main piston engine, their operation drastically reduced the fighter’s flight range and duration.
As a result, these hybrid-powered projects were eventually abandoned. Nevertheless, they influenced development of the jet engines that were designed for rockets and missiles. Even though the D-13’s used on the La-9RD were never used later on, numerous designs from Chelomey’s design bureau eventually turned it into one of the world’s largest developers of rocket and space technology.
The La-9RD in game is a Tier VII fighter that naturally resembles regular fighters from the Lavochkin branch. Two pulsejets provide great advantages in speed and dynamic parameters. La-9RD can fight effectively at higher altitudes than its same-tier La-7 brother, and is more than capable of catching up and causing a lot of trouble to speedy enemies, including heavy fighters. The main disadvantages are caused by the same jet engines: the La-9RD is somewhat less maneuverable than the regular Lavochkins, so dogfighting should be done with caution. Additionally, the machine only has two 23-mm NS-23 cannons, so its firepower is lower than that of the La-7 in top configuration. Gameplay of the La-9RD can be both aggressive (intercepting and destroying high-speed enemy fighters) and careful (picking a target and immediately boosting to close range, where most aircraft simply won’t be able to shake the fighter from their tail). Its main feature is its ability to catch up to any enemy and stay on its tail, dealing consistent damage with its pair of accurate medium-caliber cannons.