The Lavochkin La-5 was a Soviet fighter aircraft of the World War 2 which was itself an improvement from the previous LaGG-1 and LaGG-3.
The LaGG-1 was underpowered and the LaGG-3, couldn't overcome that lack of power, in spite of its lighter airframe and stronger engine, so in early 1942, LaGG-3 factories were converted to manufacture the Yakovlev Yak-1 and Yak-7. In late 1941 Lavochkin worked unofficially to improve the LaGG-3. The work centred mainly in replacing the underpowered Klimov M-105 inline engine of the LaGG-3 with a stronger Shvetsov ASh-82 radial engine. The nose section was replaced with one taken from a Sukhoi Su-2, as the Su-2 was also powered by the Shvetsov engine.
The new engine required a shift in aircraft's balance and some other fittings but by December 1941 it was completed. However, ground testing showed several problems with the new engine so its maiden flight was delayed and it wasn't until March 1942 took off with Aleksei I. Nikashin, a highly experienced pilot of the Soviet Air Force Scientific Research, at the commands.
The prototype showed good flying characteristics, although it didn't completely overcome the flaws present at the LaGG-3. Therefore, many detail improvements were made before the La-5 prototype was passed to Scientific Research Institute for state acceptance trials in April 1942.
Overall, in the evaluation made by the Scientific Research Institute, the radial engine-powered La-5 demonstrated its superiority over the LaGG-3 and they considered that it had potential to be an excellent fighter, at least for VVS' (Soviet Air Force) standards of the time. Trials were carried out in less than a month and the aircraft was given green light for mass production by the People's Commissariat for Aviation Industry (NKAP), beginning mass production in July 1942. At first the new fighter was called 'LaG-5' but since Mikhail Gudkov, one of the original designers of the LaGG-3 was no longer involved in the programme, both letter Gs were dropped, although Gorbunov was still involved.
However, since there were doubts about La-5's empirical performance at the battlefields, for a time both LaGG-3 and the La-5 were manufactured alongside each other at the State Aircraft Factories, so new features and improvements were introduced in both types.
The first production batch of the La-5 was basically a LaGG-3 with the ASh-82A engine and many inherited features, such as the widescreen, canopy or pitot tubes, which were improved upon the war was going on.
The main differences between the prototype and the production series were the inclusion of armament (two 20 mm ShVAK cannons mounted in the forward fuselage), which also required the adaptation of enlarged breech gun covers on the nose, plus some added fairing, an ASh-82A engine, as already mentioned and an enlarged oil cooler, situated below the engine. It could also carry up to 50 kg (110 lb) of bombs in underwing racks, although very few La-5s were equipped with underwing racks. It was also equipped with radio system, although not in every aircraft.
The Central Aerodynamic Institute (TsAGI) tested the first branches of the La-5 against the prototype and found a considerable loss of speed, mainly due to the poor coupling of the engine to the fuselage, given wartime shortages in the factories. This problem was addressed over the time.
The first La-5 were assigned to VVS' Fighter Regiments (the Soviet equivalent to a squadron sized unit) in the fall of 1942, although in August it seems that some few of had the type in their ranks. The main foe of the La-5 at the time of its introduction was the German Messerschmitt Bf.109G-2 which was superior to the La-5 in every aspect as checked after having captured on in the Stalingrad area.
Anyway, most Soviet fighter pilots, used to fly the MiG-3, the LaGG-3 or even the Polikarpov I-16 were quickly accustomed to their new fighter and were pleased by the performance improvement. Ground crews were also satisfied as it was easier to maintain and, therefore, to enhance La-5's service rate.
The La-5 saw action during major Soviet battle from the fall of 1942 to the summer of 1943 when it was gradually replaced by more advanced variants of the type, although some remained in service until well entered 1944.
The first produced La-5s were deployed straight from production lines to the Stalingrad area and the La-5 was also deployed in the Kuban area fighting Luftwaffe's Luftflotte 4 over the North Caucasus during that campaign that took place between April and May 1943.
The La-5 was also widely employed in July 1943 at the Battle of Kursk. It was during the course of this battle that Ivan N. Kozhedub, later to be USSR's top ace, made his combat debut in a La-5.
One La-5 was captured by the Germans on 30th July 1942 when Lt. Col. Nikolai Vlasov flew made an emergency landing at Larisov airfield, near Ostrov in Pskov, while a second La-5, belonging to the famous Valery Chkalov squadron was also captured and tested at the Rechlin Test Centre.
During the whole year of 1942 a total of 1.129 La-5 were manufactured at State Aircraft Factory 21 in Nizhny-Novgorod, while State Aircraft Factory 31 at Tblisi built additional 22 machines. In comparison a total of 2.771 LaGG-3 were built during that same year.
This was because the La-5 was regarded as an interim step to adopt the M-82/ASh-82A radial engines without disrupting production lines. This gave Lavochkin Design Bureau enough time to develop a more sophisticated variant of the La-5 eliminating the lack of backward visibility and its short range. The last Shvetsov M-82F powered La-5s were delivered in early 1943.
Sources:
1st Signal Squadron - Aircraft In Action 169 - La5-7 Fighters in Action
2nd https://en.wikipedia.org/wiki/Lavochkin_La-5