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

[Paul Riley]

Can anyone provide me with a link to any information regarding the optimal firing angle to use to a target (bearing to target in scope),taking into account current range and speed of target.Due to my recent failure at only 500m using a slow electric I am eager to learn the optimal firing angles to use,particularly with electrics.This of course I could figure out myself in the academy,but would prefer a working listing in here using all possible variables.

So for example -

Target speed = 7kts
Range to target = 500m
Torpedo speed = 30kts
Fire angle = ?

This would be greatly appreciated

[Kubryk]

I think you must take AOB into consideration. If targets speed and distance from you is constant in your query, all you got to do is choose some AOB (likely 90) and bearing with that AOB, and then check with TDC. Set torpedo speed to slow, check on what bearing you get 000 gyroangle, change torp. speed to medium, repeat and then change speed to fast and check again. Write everything down, you can get all needed information in couple of minutes, using imaginary target.

This is the simplest solution, or I misunderstood your request totally

[Paul Riley]

No no no,you misunderstand me
You are talking about a 90 degree parallel shot while moving with your target,I am pretty much a master at this now,at least I feel very confident with these shots (using steam torpedoes that is).I am talking about shooting while FACING (facing perpendicular at 90deg to his course) your target from a dead stop.So,If I was at 1000m,and I was using an ETorp,waiting for a firing angle of 10deg in the scope would no doubt be too late,yet firing on say 20-25deg in the scope would give a better lead on the target with more time to hit it.
Ultimately,I desire info on the optimal TIME to release the torpedo,because if the release is too late it passes harmlessly across his stern,as happened to me earlier tonight.

This info would also greatly benefit those trying to shoot at extreme range and beyond.

Do you understand what I mean now?

[sharkbit]

I saw within the last week or so a post with the answer you're looking for, but for the life of me, I can't find it. I searched some but without luck. I think it was for fast torpedoes and 90AOB though.

One thing that you can try is to build you hitman's Kriegsmarine Whizwheel. It gives you the ability to figure out lead angle for various torpedo speeds, target speeds, and AOB's. If you don't want to build it, I believe there used to be or still is a flash player version that you can use on your computer. I have it at work and play around with it some.
I built one to use during the game, but I use it for other things mostly. There are a ton of other uses for it-intercept courses, target speeds through bearing observations, etc.

The TDC should figure out lead angle for you. The whizwheel does the same thing as the TDC but you do the solution yourself and a lot slower.


Link below:
http://www.subsim.com/radioroom/show...t=kriegsmarine

[Paul Riley]

I think we are on the same wavelength here mate,yet whats REALLY important for me is the release time for the torpedo,the firing angle as I call it,the optimal time taking into account target range,speed,and more importantly torpedo speed.I find using steam torpedoes the problem isnt as great because their great speed allows for good shooting scenarios at ranges upto about 3000m,however the slow speed of the early ETorps and things become slightly harder,making the optimal time to release it even more important.

[sharkbit]

Paul,
I keep feeling like I'm missing something:
The TDC should figure out your firing angle based on the target's range, speed, and AOB. If that data is correctly input at the time of firing, the torpedo should hit the ship at exactly where you point the cross hair of your UZO/scope. You shouldn't have to lead the ship at all with your scope.

Please forgive me if I'm being dense and not fully understanding your issue(I'm still at work and have a couple more hours to go). You have obviously had much success judging by your posts (which I always enjoy reading, by the way ) and that may be why I'm having a problem fully understanding your issue.

[Kubryk]

Originally Posted by Paul Riley

No no no,you misunderstand me
You are talking about a 90 degree parallel shot while moving with your target,I am pretty much a master at this now,at least I feel very confident with these shots (using steam torpedoes that is).I am talking about shooting while FACING (facing perpendicular at 90deg to his course) your target from a dead stop.

I was talking about the same thing as you, I rarely perform parallel shots, two times lately in heavy fog from a very close distance. I was talking about dead-stop AOB 90 method.

Originally Posted by Paul Riley

So,If I was at 1000m,and I was using an ETorp,waiting for a firing angle of 10deg in the scope would no doubt be too late,yet firing on say 20-25deg in the scope would give a better lead on the target with more time to hit it.
Ultimately,I desire info on the optimal TIME to release the torpedo,because if the release is too late it passes harmlessly across his stern,as happened to me earlier tonight.

This info would also greatly benefit those trying to shoot at extreme range and beyond.

OK, so why can't you use TDC for this?
1. you're dead stop, perpendicular to targets course
2. you know the distance to target, put it into TDC
3. you know targets speed, put it into TDC.
4. you know AOB (90), into TDC
5. you set torpedos speed
6. you check on what bearing you got gyroangle 000. when important part of the ship crosses that bearing, los, you shoot.

When you know that bearing you know the angle for a given target speed and distance, providing you stick with AOB 90. Changing torpedoes speed would give you different bearings, thus different angles.

Am I making an ass of myself here and am not aware of that fact?

Man, I'm either really stupid or extremly blind, because I have no idea what's wrong with TDC method

[sharkbit]

Originally Posted by Kubryk

6. you check on what bearing you got gyroangle 000. when important part of the ship crosses that bearing, los, you shoot.

Right.
If you set your scope so that the gyro angle reads 000, your scope/UZO will be on a different bearing. This is how much the lead angle will be.

[Kubryk]

Originally Posted by sharkbit

Right.
If you set your scope so that the gyro angle reads 000, your scope/UZO will be on a different bearing. This is how much the lead angle will be.

Exactly, one would get different bearing (calculated from 0 or 360 = angle) for different torpedo speed.

[onelifecrisis]

Paul, I'm also confused at your reluctance to use the TDC.

Originally Posted by Paul Riley

I am talking about shooting... from a dead stop.

Be aware that at a dead stop your boat can and will "drift" (read: turn) without you asking it to.

[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.

[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.