Bombers taking a lot of damage

Details, please . . .

How many heavy tank brigades in the enemy stack? Any other units in the enemy stack, and if so, how many? What research level are the enemy units? On what type of terrain is the enemy stack located? Are there any enemy fighters patrolling above the enemy stack?

How many tactical bomber and fighter squadrons are in your attacking wing? What research level are your aircraft units?

We need these details to properly analyze your case.

An HT unit has an anti-aircraft strength of only 0.6 (L1) to 1.4 (L4 "elite" with complete blueprints), but a large number of HT units could still have a decent collective AA defense, especially if combined with AA and other units. HT brigades have 45 hit points ---- more than any other ground unit ---- and an attacking TB wing often requires multiple sorties to destroy a single HT unit.

2 Lvl.6 fighters& 2 lvl.6 tac. bombers vs 2 Lvl.3 HTs

They were on plains so I'll give them that(but 20% should not see a triple damage increase)

2 L6 TBs vs armored-class unit:

> > > > 6.1 anti-armor strength points x 2 = 12.2

2 L3 HTs (on plain terrain) vs aircraft:

> > > > 1.2 anti-aircraft strength points x 2 = 2.4 x (1.5) = 3.6

Your TBs should have taken some damage, but 20% of the two TB squadrons' total of 50 hit points seems like an extreme result. Was that the result of a single direct attack, or were your TBs on patrol? How much damage was done to the HTs' total of 90 hit points?

I was using single attacks, and I only check the condition meter of the tanks, showing a 10% difference