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

[RoaldLarsen]

May I immodestly suggest the post linked here?

Perhaps what is confusing is the question of when target's AOB is 90. If you are facing perpendicular to target's true course, AOB is only 90 when target is directly in front of you, at bearing 0, or right behind you at bearing 180. Waiting until then to set up TDC isn't much use to you. For any other bearing, AOB differs from 90 by the amount bearing differs from 0 or 180. For instance, if target is moving from left to right on a course perpendicular to yours, then when target is at bearing 340 degrees, AOB is 70.

A) As long as you really are facing perpendicular to target's true course, a modification of the method in my link above can also give you true current AOB. Replace steps 8 to 11 with :
8. Rotate scope until you are pointing at target.
9. Lock scope on to target.

AOB readout will be correct and will be correctly updated automatically by the TDC, unless you alter course, until you unlock scope from target. To fire correctly:

10. Open tube doors.
11. Fire when gyro angle reaches 0.

B) Note that the above method A) aims the torpedo at the centre of the ship. To aim at a point aft of the centre, replace step 11 with:

11. When gyro angle reaches 0, unlock scope from target.
12. Fire when desired aiming point crosses vertical line in centre of scope.

C) To fire at an aiming point forward of the centre of the target, replace step 11 and 12 with:
11. When gyro angle is about 5 degrees from 0 (355 degrees if target is moving L to R, 5 degrees when target is moving R to L), unlock scope from target
12. Rotate scope in direction of target movement (i.e. away from target) until gyro angle reaches 0.
13. Fire when desired aiming point crosses vertical line in centre of scope.

D) To go to full TDC firing for any target bearing angle, as long as your course is perpendicular to target's course, replace steps 11 and after with:
11. Get a range reading
12. Immediately decouple TDC from scope to allow manual input.
13. Immediately set range on the TDC
14. Immediately couple scope to TDC.
15. Fire immediately, rather than waiting for gyro angle 0.

E) Method D) also fires at the centre of the target. To fire from any bearing angle at a point other than the centre of the target, replace step 15 in D) with:

15. Immediately unlock scope from target,
16. Immediately rotate scope to desired aiming point.
17. Fire immediately.

F) Finally, to fire at any part of target at any bearing angle when you are not headed perpendicular to target's true course, but you know target's true course and speed, follow these steps:

1. Lock periscope on target.
2. Decouple periscope from TDC to allow manual input.
3. Enter target speed on TDC.
4. Read bearing from periscope.
5. Instantly calculate AOB from your course, target's course and bearing to target.
6. Instantly enter AOB in TDC
7. Instantly couple TDC to periscope.
8. Get a range reading
9. Instantly decouple periscope from TDC to allow manual input.
10. Instantly enter range on TDC
11. Instantly couple scope to TDC
12. Instantly unlock scope from target
13. Instantly rotate scope to desired aiming point.
14. Fire immediately

If you don't know target's course and speed, you are going to need to first measure target speed, at least. If this doesn't also give you course, you will need to eyeball AOB or take careful measurements to determine course and then caculate AOB.

Since steps 5 to 7 and 9 to 14 all need to happen instantly, but this isn't really possible, you may need to adjust the values that you enter to take into account any change in AOB from the time you allow manual input to the time you couple the TDC to the scope, and any change in range between the time you measure it and the time you fire. For typical merchant speeds the changes will be negligable as long as you do not hesitate. To avoid hesitating while calculating AOB from two courses and a bearing, do most of the calculation in advance, and then just plug in the bearing to do the final step in the calculation.

[onelifecrisis]

Originally Posted by RoaldLarsen

1. Lock periscope on target.
2. Decouple periscope from TDC to allow manual input.
3. Enter target speed on TDC.
4. Read bearing from periscope.
5. Instantly calculate AOB from your course, target's course and bearing to target.
6. Instantly enter AOB in TDC
7. Instantly couple TDC to periscope.
8. Get a range reading
9. Instantly decouple periscope from TDC to allow manual input.
10. Instantly enter range on TDC
11. Instantly couple scope to TDC
12. Instantly unlock scope from target
13. Instantly rotate scope to desired aiming point.
14. Fire immediately

Since steps 5 to 7 and 9 to 14 all need to happen instantly, but this isn't really possible, you may need to...

5 to 7 need not be instant, and 9-14 can be greatly speeded up by any GUI mod that adds the TDC controls to the periscope screen (i.e. basically any GUI mod). Allow me to demonstrate with this... improved version of your method.

1) Set the TDC to Auto.
2) Go to the periscope view and lock on to the target, then unlock the scope. Between now and step 5 do not move the scope and do not change course.
3) Set the TDC to Manual.
4) The bearing in the TDC will now match that of your scope as it was when you unlocked it (and you have not moved it since then). Taking as long as you need, and using any method you like (map plotting, whiz wheel, etc.) calculate the AOB that the target ship had when it was at the bearing shown on the TDC i.e. the AOB it had when you unlocked the scope in step 2. Enter that AOB into the TDC, along with the target speed.
5) Set the TDC to Auto. You may now move the scope, but you must still not change course. Go to the periscope and lock it to the target.
6) This bit does need to be done as quickly as possible. Calculate the current range to the target using whatever method you like. As soon as you have calculated the range unlock the scope, set the TDC to Manual, enter the range into the TDC, set the TDC back to Auto, lock the scope to the target again (or manually aim the scope at the part of the ship you want to hit) and fire.

[Paul Riley]

To prevent further confusion and frustration I think this post then is effectively closed,thanks for the replies.
Let me just finish by saying,its hard to explain exactly what I was trying to explain,and I DO use the TDC for the record.
This all started by my strange miss with the electric yesterday at only 500m.
I will be studying these last posts for a while,to compare what I did and what is being said here.

Thanks.

[RoaldLarsen]

Originally Posted by onelifecrisis

1) Set the TDC to Auto.
2) Go to the periscope view and lock on to the target, then unlock the scope. Between now and step 5 do not move the scope and do not change course.
3) Set the TDC to Manual.
4) The bearing in the TDC will now match that of your scope as it was when you unlocked it (and you have not moved it since then). Taking as long as you need, and using any method you like (map plotting, whiz wheel, etc.) calculate the AOB that the target ship had when it was at the bearing shown on the TDC i.e. the AOB it had when you unlocked the scope in step 2. Enter that AOB into the TDC, along with the target speed.
5) Set the TDC to Auto. You may now move the scope, but you must still not change course. Go to the periscope and lock it to the target.
6) This bit does need to be done as quickly as possible. Calculate the current range to the target using whatever method you like. As soon as you have calculated the range unlock the scope, set the TDC to Manual, enter the range into the TDC, set the TDC back to Auto, lock the scope to the target again (or manually aim the scope at the part of the ship you want to hit) and fire.

Wow!

Of course, that works perfectly. I'm kicking myself for not having worked it out on my own.

Thanks, OLC.

[onelifecrisis]

[Paul Riley]

[quote= RoaldLarsen;1101580]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

[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.

[Paul Riley]

Many thanks for your replies on this issue,it is appreciated.
I am taking careful notes from all this info and will keep my answer here short to reflect that.Can't really say any more on this now

[Paul Riley]

Finally ironed out my firing woes,everything is back on track.Been practicing a lot using 30kt torpedoes,to simulate the slower electrics,and to be honest I was quite thrilled by my level of accuracy,from many different angles and ranges

[RoaldLarsen]

Originally Posted by Paul Riley

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.

From your descriptions, that's what I figured, so that's why I wrote the instructions as I did. If you are setting yourself up 90 degrees to target course, you really should be firing with a gyro angle of 0, which means you really should be reading the gyro angle. Otherwise you are giving up the advanatge of being at 90 degrees.

Originally Posted by Paul Riley

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.

Which is why you are missing. I don't buy the "It's a bug" explanation. Yeah, there's a bug, but even if you set your torp speed properly, you'd still miss a smaller ship by about 20 meters with the solution you were using.

How did you happen to select 10 degrees, BTW?

Originally Posted by Paul Riley

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

There are three places you can read the gyroangle. On the <F6> TDC screen, it is produced on the two dials in the botom right part of the screen. However, the better place to read it is on the periscope screen or on the UZO screen. In stock, and some supermods, you will find a readout that looks a bit like an older car's odometer on the right hand edge of the screen, just above the forward torpedo ready indicator lights.

[Paul Riley]

[quote=RoaldLarsen;1102613] Which is why you are missing.

How did you happen to select 10 degrees, BTW? quote]

I havent normally being missing,I have had some good successes lately,admittedly using STs,and not ETs.That one event with the ET was the first major miss ive had in a long time.It was a simple error and misunderstanding on my part,and I believe is now sorted out,finally.

I guess the 10deg was guesswork on my part,and I obviously wasnt paying enough attention to the gyroangle readout.I may have also been using the STs speed advantage too much,without considering what would happen if the speed was set to slow...and thats exactly what happened

BTW,sorry about highlighting the quote,I seem to be having an issue displaying the default quote with the box around it.

[RoaldLarsen]

OLC and Pisces have made me think about this even more, and I now think there is an even better method to fire at an arbitrary angle from an arbitrary course, if you know target's course and speed:

0. Select tubes, torpedo depth, torpedo speed, and salvo spread, and open tube doors any time before step 9
1. Unlock periscope from target.
2. Rotate periscope to bearing 0 degrees (or 180 for stern tube shot).
3. Decouple periscope from TDC to allow manual input.
4. Enter target speed on TDC.
5. Set AOB on TDC as 180 minus the difference between your course and target's course. (or AOB = difference in course for stern tube shot)
6. Couple TDC to periscope.
7. Rotate scope to target
8. Lock scope on target
9. Get a range reading
10. Instantly unlock scope from target.
11. Instantly decouple periscope from TDC to allow manual input.
12. Instantly enter range on TDC
13. Instantly couple scope to TDC
14. Instantly rotate scope to desired aiming point.
15. Fire immediately

And to avoid having to take a range reading, if you can afford to wait for a 0 gyro angle shot:
0. Select tubes, torpedo depth, torpedo speed, and salvo spread, and open tube doors any time before step 9
1. Unlock periscope from target.
2. Rotate periscope to 0 degrees. (or 180 for stern tube shot).
3. Decouple periscope from TDC to allow manual input.
4. Enter target speed on TDC.
5. Set AOB on TDC as 180 minus the difference between your course and target's course. (or AOB = difference in course for stern tube shot)
6. Couple TDC to periscope.
7. Rotate scope to target
8. Lock scope on target
9. Fire when gyroangle reads 0.

To fire at an aiming point other than centre of target, adjust final steps as in my earlier post ITT.

[onelifecrisis]

Yup, that works, in fact it's the same as my method except you assume that the player knows the target course. The method I described was more generic: it will work with any type of AOB calculation, including the use of an AOB Finder (U-Jagd Tools mod and all derivatives) and/or an eyeball estimate, neither of which require the target course to be known.

[Paul Riley]

Originally Posted by RoaldLarsen

5. Set AOB on TDC as 180 minus the difference between your course and target's course. (or AOB = difference in course for stern tube shot

I was just wondering,is it neccessary to input the actual AOB at that moment?,as the TDC updates the AOB when you set it back to auto.What I have been doing is,if firing at SB side of a ship set angle of bow to 90deg SB respectively,and bearing to 90deg PS,set to auto and the correct AOB at that moment is updated,of course checking all other settings are correct.
Again,am I missing the crucial thing here?

Thanks.

[onelifecrisis]

Paul, that's actually the method I use when I know the target course and my own course is perpendicular to it (which is at least 90% of all my attacks).

They say the best mathematician is a lazy mathematician.