soviet pilot training WWII, what aircraft and hours?

[zan64]

Been reading about American training and it got me curious, what was Soviet training like? I assume in the early years of the war it was a lot briefer than American and British. So did the Soviet have a tier system like the Americans (primary/basic/advanced), if so how did they transition, U2 straight into an IL-2 or or was there an intermediate aircrft like a harvard or BT-13 they trained on?

[Pahec97]

Primary training was in U-2, later pilots moved to UT-1/UT-2. Advanced training was on 2-seat variants of fighters- UTI-4(2-seater I-16) or UTI-26(what would become Yak-7)