This applies to all AA that fires missiles, but is specifically awful for Flail and Tarantula.
Flail:
StartVelocity: 200 elmo/s
Acceration: 300 elmo/s^2
Flight Time: 3.5s
Range: 800 elmo
Max speed: 1400 elmo/s
If you plug that into calculator you get this:
Calculated Range: 2537 elmo
Max Speed Reached: 1250 elmo/s
So not only is the velocity shown incorrect, but the range the missile can fly is absolutely ridiculous. Combined with the turn rate being so high it makes it basically IMPOSSIBLE to evade this missile. Which means if you fly even slightly into range of Flail the missile will fire and WILL hit you. No matter if you boost with swift or not.
This feels awful in the game as it does not reward micro skill at all. You are just doomed to lose the unit that is targeted.
It is especially horrid when you encounter a ball of cloaked AA, in which case you might as well resign immediately.
I am planning to have a look at reworking some air ground interaction over Christmas holidays to at least try and make air slightly less painful to play. So far have made a mod for tweaking things and came up with this so far:
Will post here every so often with how its going.