intentionally removed by NT developer, you should go ask him over here
his comment in the code:
"There is no way anyone was actually using these right? I think its fine to just simplify it into a flat attack upgrade instead of needing to create entirely new designs around AP bombs"
I will reenable it. They actually quite powerful before tier 3 torpedo unlock.

Not sure if this is intended or not but the armor piercing bombs tech under the airplane tab only gives stat increases. It does not give the unlock for the armor piercing bomb module. The tech doesn't event show the module being registered as being an unlock, which makes it really annoying to try and design Dive Bomber CAS planes (which historically were more effective against ships in WW2 than torpedo Bombers).

Cheers mate.

@siveen fixed; the rocket's aspiration should be now in experimental rocketry and same tech that unlock 2nd tier rocket engine

Hey SSD. I think Rocket Interceptors/Rocket Engines are broken right now - I can't find a compatible Engine Aspiration module for Rocket Engines, but it's a required module.

it is in separate tab

i want question again new technology don't have a helicopter tech yet?

you sure are a scholar and a gentlemen