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La-7R

Fighter

Lavochkin

By September 1944, the decision of the State Defense Committee was supposed to build and submit for flight tests modifications of the Yak-9, La-5 and Su-6 2TK-3 fighters with additional RD-1 rocket engines developed by V. P. Glushko in the NKVD Design Bureau at the plant no. 16. During the operation of the boosters on the Yak-9 and La-5 aircraft, the climb time of 5000 m should have been reduced to three minutes, and the maximum horizontal flight speed should have increased to 780 km / h in a time interval of up to three minutes.

S.A. Lavochkin entrusted the execution of this task to the branch of the design bureau organized in March 1944 in Moscow (the main design bureau remained for the time being in Gorky at plant No. 21), which was led by S.M. Alekseev. The branch was called "Experimental Plant No. 81" and was located on a part of the serial Moscow aircraft plant No. specially allocated for it. 381, which produced La-7 aircraft at that time. The alteration of the first serial La-7, which received the new La-7R-1 index, was completed by October 21, 1944. On this aircraft and on the La-7R-2 that followed it, the tail section of the fuselage was finalized to accommodate the RD-1 in it, mounted the engine itself and additional equipment related to the operation of the LRE. The place of the central gas tank was taken by a bank of nitric acid, and a tank of kerosene was installed in the right wing console. The stock of nitric acid was 270 kg, kerosene - 60 kg. This amount of fuel was sufficient for the operation of the RD-1 for 3.5 - 3.8 minutes. The stock of gasoline was reduced from 340 to 210 kg. To supply fuel components to the RD-1 combustion chamber, a pump was used, which was driven by a special shaft frictionally connected to a ratchet on the rear cover of the ASh-82FN engine. In the lines of acid and kerosene, a pressure of 40-50 atm was provided. (pressure in the combustion chamber of the engine - up to 23 atmospheres). The control of the rocket engine was fully automated and was reduced only to the use of the gas sector handle and the starting air cock. In order to avoid corrosion, which even a small amount of acid fumes led to, the aircraft structure was carefully insulated. Acid-resistant materials were used in the acid system: aluminum - both pure and some of its alloys, as well as certain grades of stainless steel.

Factory tests of the La-7R-1 began on October 27, 1944. In early November, two flights were made on it to test the propeller group (VMG) without turning on the rocket engine. During subsequent ground tests of the RD-1, it was found that the torque generated by the drive from the ASh-82FN to the LRE pump unit is insufficient. After the defect was eliminated, flight tests continued. In order to test the RD-1 at altitudes of 3000-3200 m, 6-8 ignitions and 4 fire starts of the RD-1 engine were carried out, and two fire starts - until the fuel components were completely exhausted. Ignition and fire launch proceeded normally. But as the fuel ran out, after about two and a half minutes, a pulsation arose in the exhaust of the RD-1 and the pressure in the combustion chamber fluctuated up to 8 atmospheres. Three flights were devoted to the development of repeated fire launches of the liquid-propellant rocket engine. In the first of these, the engine failed completely; in the second - after the first launch, it worked for 15 seconds, and when it was repeated, it failed; in the third - in two launches, the RD-1 worked for 15 seconds, but failed with another launch attempt. It was not possible to establish the cause of the failures. In three other flights, the maximum horizontal speeds were determined at an altitude of 3000 meters in the nominal mode of operation of the ASh-82FN with the idle and operating LRE. In the most successful third flight, the increase in speed due to the operation of the RD-1 amounted to 85 km/h. Program factory tests were completed on February 24, 1945, and the aircraft was put under repair. In total, test pilot A.V. Davydov made 15 flights, including five with the inclusion of the RD-1. The total number of fire launches of rocket engines was: fifty-seven on the ground and six in the air.

The second copy of the La-7R-2 was built at the 81st plant, mainly from the La-7 units of the fifty-first series. Unlike La-7R-1, which was only a flying laboratory, this aircraft had better aerodynamics. In 1945, the La-7R-2 entered flight tests. From January 26 to March 27, 19 flights were made on it, 45 LRE launches, including six in the air. In two launches of the RD-1, the platforms were removed in flight. On March 1, at an altitude of 2700 m, the engine ran for a minute and a half, after which, due to pulsation in the combustion chamber, it had to be turned off. The increase in speed was 80 km / h on the instrument, and on March 10, at an altitude of 2600 meters, the RD-1 added about 95 km / h. In general, the engine worked poorly, in 15 starts out of 45 it failed, and in six cases - due to the fault of the ignition.

March 27, in a test flight at the La-7 in flight at an altitude of 6000 m, the additional engine did not turn on, an attempt to restart at an altitude of 3000 m ended in a strong explosion in the combustion chamber of the RD-1. The rudders were badly damaged. The plane lost control and rolled over. Being in a cockpit filled with nitric acid vapors, test pilot G. M. Shiyanov was able to land the car with great difficulty. Until April 14, the damaged empennage and combustion chamber were replaced on the La-7, minor defects that appeared as a result of the accident were eliminated.

An RD-1 engine was installed on the aircraft, which has special diaphragms with a hole up to 20 mm in diameter to ensure pressure from the ether-air ignition on the ground to 0.5 atmospheres. However, attempts to launch it at altitudes from 5000 to 6000 meters ended in vain. Due to the large number of RD-1 failures associated with ignition problems, the OKB-SD of plant No. 16 developed a version of the RD-1X3 engine with chemical ignition instead of electric. The following fuel components were used as starting fuel components: B23-75 fuel (a solution of synthetic rubber intermediate in B-70 gasoline) and an oxidizing agent (nitric acid). The installation of the RD-1X3 on the La-7 began on April 29, however, the RD-1X3 was not more reliable than its predecessor - accidents continued. The very next day, May 12, during ground fire tests on the La-7, the engine combustion chamber exploded. Of the four RD-1X3 assembled and put on flight tests, three crashed. The fourth, intended for the Su-6, was received only on May 11, and now it was mounted on the aircraft. The last of the remaining RD-1X3 was sent to OKB-16 for overhaul.

Laboratory studies have shown that the explosions were caused by hydraulic shocks in the combustion chamber, which occurred as a result of a sharp increase in pressure in the "shirts" of the combustion chamber at the moment the fuel valves were opened. The hydraulic shock knocked down the ignition torch, there was an accumulation of components inside the chamber, the ignition of which led to an explosion. Three RD-1X3 engines of a new modification for the Yak-3, La-7 and Su-6 aircraft arrived from OKB-16 already on July 14, 1945. They were equipped with special starting and drain valves, and the injectors of both fuel components were switched on in series, which significantly increased efficiency incendiary torch and making the engine start smoothly, without impact.

The engine was installed on the La-7R-2 on July 25th. On this aircraft in the period up to September 16, 1945, 14 flights were made. Of the 49 engine starts, 8 were made in the air, and 5 of them were used to remove sites. During this time, four engine chambers and two pumps were replaced. RD-1X3 failed 23 times, but only two failures fell to the share of ignition.

Despite all the difficulties, the tests still managed to be completed. On La-7R, a maximum flight speed of 795 km / h was obtained at an altitude of 6300 meters.

Specification La-7R
Crew 1
Dimensions
Wing span, m 9.80
Wing area, m² 17.59
Length, m 8.67
Powerplant
1 PE ASh-82FN + 2 с LRE RD-1X3, hp 1 × 1850 + 300
Weight, kg:
Weight, kg: 2,703
Loaded weight 3,500
Maximum rate of climb, m/min 1,340
Performance
Maximum speed, km/h 795 at altitude 6300 m
Service ceilling, m 13,000
Armament
2 × 20 mm ShVAK guns
Photo Description

Drawing La-7R with ASh-82FN and RD-1X3


NKVD - Narodnyy komissariat vnutrennikh del - People's Commissariat of Internal Affairs

PuVRD - Pul'siruyushchiy vozdushno-reaktivnyy dvigatel' - Pulse jet engine

GKO - Gosudarstvennyy komitet oborony - State Defense Committee

VMG - Vinto-motornaya gruppa - Propeller group

La-9RD

Fighter

The Lavochkin La-9 serial fighter was equipped with the additional RD-13 pulsjet engines, August 1947.

From November 21, 1947 to January 13, 1948, the serial La-9 No. 48210509 (La-9RD), equipped at the 51st plant with two RD-13 autopulse jet engines designed by V.N. Chelomey, passed state tests. The lead test pilot was I.M. Dziuba. On the plane, they changed the fuel supply system, removed the armored back, and two NS-23 guns, strengthening the airframe design. The increase in speed was 70 km / h. The pilot noted strong vibrations and noise when the PuVRD was turned on. The suspension of the PuVRD worsened the maneuvering and takeoff and landing characteristics of the aircraft. Starting the engines was unreliable, the flight duration was sharply reduced, and operation became more complicated. The work carried out was beneficial only in the development of ramjet engines intended for installation on cruise missiles. Aircraft participated in air parades and invariably made a strong impression on the public with their roar. According to eyewitnesses, from three to nine machines with PuVRD participated in different parades. The culmination of the PuVRD tests was the flight of nine La-9RDs in the summer of 1947 at an air parade in Tushino.

In the spring of 1946, the construction of the "130R" aircraft with an additional rocket engine began. In those years, despite their "gluttony" and the high toxicity of the oxidizer, LREs were installed on many fighters. When installing the RD-1X3 rocket engine, the machine had to be reconfigured. Instead of the central, gasoline, tank with nitric acid was installed. Pump drives for supplying fuel components were connected to the ASh-83FN engine. And the kerosene tank was placed between the ASh-83FN and the cockpit, under the carriage, on which only two guns were left.

In 1946, when the airframe was already being assembled, all work but "130R" stopped. The reason for this was the successful testing of the first domestic aircraft with turbojet engines and, in general, unsuccessful attempts to install still "raw" and dangerous liquid propellant engines in operation on other types of aircraft.

Specification La-9RD
Crew 1
Dimensions
Wing span, m 9.80
Wing area, m² 17.72
Length, m 8.625
Height, m 3.56
Powerplant
1 PE ASh-82FN + 2 × D-13, power hp 1 × 1850
Weight, kg:
Empty 3,150
Loaded weight 3,815
Performance
Maximum speed, km/h 760
Service ceilling, m 10,800
Armament
2 × 23-mm cannons NS-23

Bibliography

  • "The history of designs of planes in USSR 1938-1950" /Vadim Shavrov/
  • "Planes of Stalin falcons" /Konstantin Kosminkov and Dmitriy Grinyuk/
  • "The Soviet planes" /Alexander Yakovlev/