Purpose: To use a rocket engine to boost a fighter's flight performance.
Design Bureau: OKB of Semyon A Lavochkin.
By early 1944 the all-wood La-5 fighter had given way in production to the La-7, with metal spars and other modifications. The en- gine remained the ASh-82FN 14-cylinder radi- al rated at 1,600hp. One of the first production aircraft was fitted with an RD-1 rocket engine in order to boost its performance, especially at extreme altitudes where the ASh-82 family of engines were less impressive. The installa- tion was completed in the late autumn of 1944, and ground testing occupied nine weeks. In the last week of the year the as- signed pilot, Georgii M Shiyanov, began the flight-test programme. Together with AVDavydov the La-7R was flown 15 times without serious malfunction, though the pro-
Above: Ground test of '120R' rocket engine. Opposite: Two views of La-7R.
gramme had to be abandoned because of progressive weakening of the rear fuselage by vapour and accidental spillage of the acid. Testing was continued with the RD-lKhZ in- stalled in a second La-7R in early 1945. Brief testing was also carried out with a similar en- gine installed in the '120R'. On 18th August 1946 this aircraft excited spectators at the Avi- ation Day at Tushino by making a low flypast with the rocket in operation.
Both the La-7R test aircraft were originally standard production fighters. The RD-1 was one of the world's first liquid-propellant rock- et engines to fly in a manned aircraft, the de- signer being V P Glushko. The thrust chamber was mounted on a framework of welded steel tubes carried behind a modified rear fuselage frame, which merged at the top into the fin trailing edge. To accommodate the rocket the lower part of the rudder was re- moved. In the fuselage behind the cockpit were a stainless-steel tank for 180 litres (39.6 Imperial gallons) of RFNA (concentrated red fuming nitric acid) and 90 litres (19.8 Imperi- al gallons) of kerosene. These propellants were supplied by a turbopump energised by hot gas bled from the main thrust chamber. The turbine had a governed speed of 26,000rpm, and drove pumps for the two pro- pellants plus lubricating oil and water sup- plied from a small tank to cool the turbine and thrust chamber walls. Mass of the installation was approximately 100kg (220 Ib), or 215kg (474 Ib) complete with propellants and water. The basic RD-1 had electrical ignition, while the RD-1 KhZ had automatic chemical ignition from hypergolic liquids. The rocket was of the on/off type, cut in or out by a switch on the main throttle lever. It could not be varied in thrust (300kg, 661 Ib, at sea level), but could be shut off before the tanks were empty, nor-
mal duration being 3 to 31/2min. Both La-7R air- craft retained their armament of two UB-20 cannon. The ' 120R' differed in having an ASh- 83 engine, rated at 1,900hp, armament of two NS-23 guns and in other details.
Together with such other aircraft as the Pe- 2RD and Yak-3RD these test-beds confirmed the value of a rocket engine in boosting per- formance at high altitude. On the other hand they also confirmed that RFNA is not compat- ible with a wooden structure, and in any case the value of three minutes of boost was con- sidered questionable. Dimensions (both) Span Length Wing area Weights (La-7R) Empty
Fuel and propellants Loaded
Weights ('120R') Empty
Fuel and propellants Loaded 9.8m 8.6m 17.59m2 2,703kg. 604kg 3,500kg 2,770kg 470kg 3,470kg 32 ft IK in 28 ft TM 189ft2 5,959 Ib l,3321b 7,716 Ib 6,107 Ib l,0361b 7,650 Ib A standard La-7 typically had empty and loaded weights of 2,600kg and 3,260 kg
Performance
(La-7R) generally unchanged, but maximum speed at 6 km (19,685 ft) altitude was increased from 680 km/h (422.5 mph) to 752 km/h (467 mph).
Service ceiling was increased from 10,700 m (35,105 ft) to 13,000 m (42,651 ft).
The only figure recorded for the '120R' is a speed (height unstated) of 725 km/h (450.5 mph), but this speed (at 7,400 m) is also recorded for the unboosted '120'.
L A V O C H K I N L a - 7 R A N D ' 1 2 0 R ' / ' 1 6 4 ' ( L a - 1 2 6 P V R D ) A N D ' 1 3 8 ' ( 1 3 0 P V R D - 4 3 0 )
Lavochkin '164' (La-126PVRD) and '138' (130PVRD-430)
Purpose: To test the use of ramjets to boost propulsion of a fighter.
Design Bureau: The OKB of S A Lavochkin. By 1942 M M Bondaryuk had achieved reli- able operation with the VRD-430. By this time this refined subsonic ramjet had flown over 200 times on test-bed aircraft. In early 1946 two were attached under the wings of' 126', a slightly modified La-7, to produce the La- 126PVRD, given the OKB number '164'. The assigned pilot was A V Davidov, and he tested this aircraft between June and September 1946.
The VRD-430 was a simple ramjet designed for subsonic operation. It was made mainly of steel, and had a diameter of 400mm (1ft 3%in).
Able to burn almost any thin hydrocarbon fuel, including high-octane petrol (gasoline), it had a thrust in the region of 300kg (661 Ib), but performance data for this engine have not been found, neither have details of its fuel and control system. The La-126 was based on the La-7 but had a completely metal stressed- skin airframe, a new wing of so-called lami- nar profile, a modified canopy and many other changes, including the devastating ar- mament of four NS-23 guns firing projectiles with more than twice the mass of the 20mm ShVAK. The La-138 was basically an La-9 fighter, in which the new wing and armament of the La-126 were matched with a com- pletely redesigned fuselage. As before, a VRD-430 ramjet was hung under each wing,
to produce the '164'. The '138' was the desig- nation of the '130' after it had been fitted with two VRD-430 ramjets. It emerged in this form at the end of 1946, and flight tested 20 times between March and August 1947. Very few details survive regarding this aircraft, possibly because in the turbojet era it did not appear to be important.
The VRD-430 demonstrated its ability to boost speed (see below) but at the expense of high fuel consumption and a serious in- crease in drag when the ramjets were not being used. It is not clear why the La- 126PVRD speed was 'boosted by 64km/h' by the ramjets, while the corresponding figure for the La-138 was almost twice as great.
L A V O C H K I N ' 1 6 4 ' ( L a - 1 2 6 P V R D A N D ' 1 3 8 ' ( 1 3 0 P V R D - 4 3 0 )
La-126PVRD, also called La-7/2PVRD-430 or La-164.
La-138, also called La-130/2PVRD-430.
Top left and right, bottom left: Three views of La-126PVRD Bottom right: La-138.
Dimensions (164) Span Length Wing area Weights Empty Loaded 9.8m 8.64m 17.59m2 2,710kg 3,275kg Performance Max speed at 2,340 m (7,678 ft) 694 km/h Range with brief VRD usage 730 km Landing speed 145.6 km/h /run 688 m 32 ft 1% in 28 ft 41i in 189.3ft2 5,974lb 7,22011) 431 mph 454 miles 90.5 mph 2,257 ft Dimensions (138) Span 9.8m 32 ft \% in Length 8.625 m 28 ft 3^ in Wing area 17.59nf 189.3ft2 Weights Empty 3,104kg 6,843 Ib Loaded 3,730kg 8,223 Ib Performance Max speed at 6,000 m (19,685 ft) 760 km/h 472 mph which does not quite equate with the contemporary claim of 'boosted by 107-1 12 km/h'
Range with brief VRD usage 1,100km 683.5 miles Take-off run 450m 1,476ft Landing speed 139 km/h 86.4 mph
M A I E M A I - 1