How do i bomb ships,and other questions regarding A20 bombs

[jokash]

I'm playing "Havocs over Kuban" and 2nd mission is shipping attack. I haven't seen any of my bombs detonate (did they sink)? I have them on 1 second timer (250kg)...do they need to be on contact or do they have to land exactly on the ship (target ships are schnellbots and landing barges).Also it says i have 8 100kg FAB's but i wasn't able to throw them (nor could i open the bomb bay door to see if they are inside)?.