Soviet fighters and 4.12

[gaunt1]

The problem is that FM of most fighters are based on the performance of prototypes, not serial production aircrafts.

I dont really think that Lerche's report is biased. Germans had to know about the real capabilities of the russian fighters, which became better and better during the war. I dont think that there were any propaganda in these tests. He also tested the Yak-3, and he praised it. But back to the La-5FN: It was in very good condition, the only defect of the aircraft was the supercharger, probably the second gear didnt work properly, this is why the speed data at altitude is so low. The turning performance in the test is quite accurate I think. Lerche found out that it was similar (or a bit worse) to the Bf-109, just compare the wing loading of the Lavochkin and the Messerschmitt, they are about the same. But ingame, La-5 can outturn even the Yak-3, the best dogfighter of the VVS in RL.
About the LaGG-3, I read everywhere that it was a terrible aircraft. Every pilot hated it. As I mentioned here, the Series4 model ingame is quite well modeled, (maybe except that it should be prone to stall without using combat flaps) but later versions gradually reach the level of the Yak-1B. This never happened in RL. If the LaGG became so good eventually, why was necessary to replace its weak VK-105 engine with the M82? I did some tests ingame, I was flying a LaGG-3 S66, vs. 2 ace AI Bf-109G6. I easily shot them down in 3 minutes. Dont say that its realistic. I tried it against a Yak-9 (1942), it was a tougher fight, but I didnt feel the LaGG inferior. The LaGG never had the performance to do this.