Optimal fire angle to target in scope at different ranges and speeds

[Pisces]

[QUOTE=Paul Riley;1101607]

Originally Posted by RoaldLarsen

here? 11. When gyro angle reaches 0, unlock scope from target. quote]

I think this is the crucial factor,as far as releasing the torpedo in good time.You mean the gyroangle that rotates when locked on the target,something I DONT look at if I was to be honest,I have been looking soley at the bearing in the scope when to fire.
To try and be more precise,lets say I am at 500m,and I have an electric ready,and the target is passing me right to left on a good perpendicular intersection,tube is open well in advance,I released the torpedo when the ship was just entering bearing 10 in the scope.
You mention fire when bearing is 0 in gyroangle,bottom right of screen.If I am correct in what you are trying to explain to me this is something I havent been doing.

Please,bear with me,it is simply something that has momentarily put me on the back foot,after many good successes prior to this incident with the electric,and can strangely put you back to where you started many years ago it seems.Back to square one as it were.

I'll get it sorted before long,dont worry,its coming clearer now

That event with the electric torpedo was 99% sure due to a bug, so I would not dwell onto it for too long. Just make it a compulsory habbit to set that torpedo speed selector even after triple checking.

But it is ofcourse good to start asking question on how to improve your understanding of this complicated subject. Don't worry. You'll be a sharp shooter before not long.

The bearing in the scopes (or uzo, or even hydrophone though it cannot be linked to the TDC) is like a pointing-direction referenced to your bow. But a gyro angle (digital counter under the notepad, and 2 dials lower right of TDC F6-page) is the direction the torpedo turns to after it leaves the tube and follow a small straight run. The difference is the amount of leading the torpedo. The lead is in essence the following formula:

sin(lead_angle)=sin(AOB)*target_speed/torpedo_speed

lead_angle= asin ( sin(AOB)*target_speed/torpedo_speed )

(And is identical to how you compute lead when intercepting a distant target where the uboat replaces the torpedo, but I digress...)

If your were standing on the bridge firing a bullet with a handgun (that is just as fast as a torpedo) the 'gyro' would be bearing+lead from the formula above. This is computed by the TDC completely. There is absolutely no reason to adjust this or delay/shorten the time, assuming the dials (AOB, target speed, torpedo speed) are set correct.

Because the forward position of the tubes and this straight run and turning room for the torpedo, that gyro angle is slightly different from the 'bearing+lead' that is from the bridge/periscope point-of-view. (In the shotgun example above we ignored the width of your shoulder ) It needs a further correction for range (also done by TDC completely, but range is not updated for changing bearing as you turn the scopes). But this correction infact becomes 0 when the target is at an infinitely far range. The correction is biggest at close range, and if the target is not infront of the tubes but near your beam (like that 'parallel' shot) Therefore it is advised to only fire torpedo's when the target is roughly infront of the particular tube. Here the range correction is minimal. But this has nothing to do with the actual course of the target (or in relation to the uboat course).

The suggestion of being on a course perpendicular to the target course is due to different reasons, and more prefference than neccesity. Infact, it mostly boils down to a 90 AOB as seen by the torpedo, or in other words 90 degrees impact angle. The 90-degree-impact and the zero-gyro 'requirements' lead to the perpendicular course set-up. That's all.

'nescesity':

- If you want to make sure impact detonators work reliably instead of bounce off. (magnetics would preffer the opposite, along the length of the keel)

- It makes the target as big as possible when it is right infront of the tubes because it shows it's full length to the torpedo, alowing to shoot further away for the same lead-inaccuracy. (for magnetics aswel)

- 90 degree impact to the hull softens the effect of inaccurate AOB/course by roughly 10-fold compared to bow-on shots.

Prefference:
- It's simple to calculate the uboat course: target course +100-10 or -100+10 depending on which side. (or use a 90 degree protractor between your ship position and targetcourse on the map and place a waypoint on the corner)

- It's is simple to set up the AOB/periscope link: periscope at 0/180 bearing-> AOB at 90 port/stb.

- The bearing/AOB relation ship is very simple: AOB=(90-degrees_from_bow_or_aft)

I do it mostly because it makes things easier, not as a requirement (but I'm big on accuracy anyway). I hope this clarifies the bearing gyroangle issue a bit.