I don't want to stink up Dowly's 1xTC thread, so I'll post this here.
To get accurate torpedoes again, edit the file named SH5\data\UPCDataGE\UPCCrewData\SpecialAbilities.up c and change the last line listed below. This will keep the damage increase part of the special ability, but restore accurate TDC calculations.
Code:
;TORPEDOMAN - Passive abilities
[SpecialAbility 15]
ID=Ability-Increase-Torpedo-SpeedDamage
NameDisplayable=Ability-Increase-Torpedo-SpeedDamage-Name
Description=Ability-Increase-Torpedo-SpeedDamage-Description, Ability-Increase-Torpedo-SpeedDamage-Description, Ability-Increase-Torpedo-SpeedDamage-Description, Ability-Increase-Torpedo-SpeedDamage-Description, Ability-Increase-Torpedo-SpeedDamage-Description
Levels= 5
AbilityType=TorpedoSpeed, TorpedoDamage ;increase in torpedo speed and damage (in percents)
AbilityValue= 0, 4, 0, 8, 0, 12, 0, 16, 0, 20
I tested this out on a saved game I had where I ran across a Queen Elizabeth Battleship being escorted by 10 destroyers, on a westward course north of Scotland. I set up my shot 3850 meters from impact zone, set all TDC input data appropriately and fired off my 2 fish, set 1 meter below the Battleship's keel at medium speed.
My first torpedo was a dud and sailed clean under the keel, but the second one was good! The notable part is they went exactly where I was aiming.
She's taking on water sir!
She's going down sir!