Full-scale development of the LaG-5, as the aircraft was now designated, began, and simultaneously problems arose concerning the initiation of the production process. Especially difficult to build were the first ten aircraft, assembled early in June 1942, which were manufactured in dreadful haste, with numerous errors. While it is normal practice to make parts from drawings, this time, on the contrary, final drawings were sometimes made from the parts. At the same time the tooling was being prepared and the process of producing new components was being mastered.
Aircraft Plant No.21 handled the task well. The transition to the modified fighter was effected almost without any reduction in the delivery rate to the air force. Following delivery of the first fully operational LaG-5 on 20th June 1942, the Gorkii workers turned out 37 more by the end of the month. In August the plant surpassed the production rate of all the previous months, 148 LaGG-3s being added to 145 new LaG-5s.
Series produced aircraft were considerably inferior to the prototype in speed, being some 24.8 to 31 mph (40 to 50km/h) slower. On the one hand this is understandable, as the LaGG-3 M-82 prototype lacked the radio antenna, bomb carriers and leading edge slats fitted to production aircraft. But there were other contributory causes, particularly insufficiently tight cowlings. Work carried out by Professor V Polinovsky with the workers of the design bureau of Plant No.21 enabled the openings to be found and eliminated.
Series built aircraft were sent to war, and the LaG-5's combat performance was proved in the 49th Red Banner Fighter Air Regiment of the 1st Air Army. In the unit's first 17 battles 16 enemy aircraft were shot down at a cost of ten of its own, five pilots being lost. Command believed that the heavy losses occurred because the new aircraft had not been fully mastered and, as a consequence, its operational qualities were not used to full advantage. Pilots noted that, owing to the machine's high weight and insufficient control surface balance, it made more demands upon flying technique than the LaGG-3 and Yak-1. At the same time, however, the LaG-5 had an advantage over fighters with liquid-cooled engines, as its double-row radial protected its pilot from frontal attacks. Aircraft survivability increased noticeably as a consequence. Three fighters returned to their airfield despite pierced inlet nozzles, exhaust pipes and rocker box covers.
The involvement of LaG-5s of the 287th Fighter Air Division, commanded by Colonel S Danilov, Hero of the Soviet Union, in the Battle of Stalingrad was a severe test for the aircraft. Fierce fighting took place over the Volga, and the Luftwaffe was stronger than ever before. The division experienced its first combats on 20th August 1942 with 57 LaG-5s, of which two-thirds were combat capable. Four regiments of the division were to have 80 fighters on strength, but a great many deficiencies prevented this. Serious accidents occurred; one fighter crashed during take-off, and two more collided while taxying owing to the pilots' poor view. During the first three flying days the LaGs shot down eight German fighters and three bombers. Seven were lost, including three to 'friendly' anti-aircraft fire.
Subsequently, the division pilots were more successful. There were repeated observations of attacks against enemy bombers, of which 57 were destroyed within a month, but the division's own losses were severe.
Based on experience gained during combat, the pilots of the 27th Fighter Air Regiment, 287th Fighter Air Division, concluded that their fighters were inferior to Bf109F-4s and, especially, 'G-2s in speed and vertical manoeuvrability. They reported: 'We have to engage only in defensive combat actions. The enemy is superior in altitude and, therefore, has a more favourable position from which to attack.'
Hitherto, it has often been stated in Soviet and other historical accounts that the La-5 (the designation assigned to the fighter in early September 1942) had passed its service tests during the Stalingrad battle in splendid fashion. In reality, this advanced fighter still had to overcome some 'growing pains'.
This was proved by state tests of the La-5 Series 4 at the NII WS during September and October 1942. At a flying weight of 7,4071b (3,360kg) the aircraft attained a maximum speed at ground level of 316mph (509km/h) at its normal power rating, 332.4mph (535 km/h) at its augmented rating and 360.4mph (580km/h) at the service ceiling of 20,500ft (6,250m) The Soviet-made M-82 family of engines - derived from the US-designed Wright R-1820 Cyclone - had an augmented power rating only at the first supercharger speed). The aircraft climbed to 16,400ft (5,000m) in 6.0 minutes at normal power rating and in 5.7 minutes with augmentation. Its armament was similar to that of the prototype. Horizontal manoeuvrability was slightly improved, but in the vertical plane it was decreased. Many defects in design and manufacture had not been corrected.
In combat Soviet pilots flew the La-5 with the canopy open, the cowling side flaps fully open and the tailwheel down, and this reduced its speed by another 18.6 to 24.8mph (30 to 40km/h). As a result, on 25th September 1942 the State Defence Committee issued an edict requiring that the La-5 be lightened, and that its performance and operational characteristics be improved.
The industry produced 1,129 La-5s during the second half of 1942, and these saw use during the counter attack by Soviet troops near Stalingrad. Of 289 La-5s in service with fighter aviation, the majority, 180 aircraft, were assigned to the forces of the Supreme Command Headquarters Reserve. The Soviet Command was preparing for a general winter offensive, and was building up reserves to place in support. One of these strong formations became the 2nd Mixed Air Corps under Hero of the Soviet Union Major-General I Yeryomenko, the two fighter divisions of which had five regiments (the 13th, 181st, 239th, 437th and 3rd Guards) equipped with the improved La-5. The new aircraft proved to be 11 to 12.4mph (18 to 20km/h) faster than the fighter which had passed the state tests at the NII WS in September and October 1942.
When the 2nd Mixed Air Corps, with more than 300 first class combat aircraft, was used to reinforce the 8th Air Army, the latter had only 160 serviceable aircraft. The 2nd Mixed Air Corps, reliably protecting and supporting the counter offensive by troops along the lines of advance, flew over 8,000 missions and shot down 353 enemy aircraft from 19th November 1942 to 2nd February 1943.
Progress made in combat activities by the Air Corps aviators in co-operation with joint forces during offensive operations on the Stalingrad and Southern fronts were noted by the ground forces Command. General Rodion Malinovsky, Commander of the 2nd Guards Army (later Defence Minister), wrote:
'The active warfare of the fighter units of the 2nd Mixed Air Corps [of which 80% of its aircraft were La-5s], by covering and supporting combat formations of Army troops, actually helped to protect the army from enemy air attacks. Pilots displayed courage, heroism and valour in the battlefield. With appearance of the Air Corps fighters the hostile aircraft avoided battle.