Manual Targeting Failure

[Zosimus]

Well, the way I understand it is this: If you have all the data correctly input into the computer for the range, bearing, AOB, and speed of the target as it truly is at the moment of firing then the torpedo will unerringly cross the ship at the correct point; provided, of course, that the ship does not change course or speed. Obviously you want to hit the ship at or as close as possible to broadside because it seems that the more oblique the angle of intersection is, the more likely the torpedo is to bounce off the ship without exploding.

In my experience, the TDC range does not update automatically. I have only seen the AOB update automatically and this only on change in bearing.

I know that people say that in 90º AOB shots the range doesn't matter. I have tested it by changing the range on the F6 screen and I agree that if the ship is at 0º bearing and 90º AOB then the range will not matter. However, at other angles, when dialing the range I have seen what appears to be a change in the angle of launch. Obviously it's hard to measure with a protractor on the F6 screen as the drawing tools are unavailable.

Additionally, there are other good reasons for having the range correctly entered. If you put in the wrong range you will see your stopwatch tick past the red mark with no explosion, think you've missed, and fire another eel at the ship only to find the torpedo intersecting the ship seconds later. The second shot is invariably wasted.

Additionally it may be impossible for you to fire at the perfect 000 gyroangle, especially in choppy water, as you may temporarily lose sight of the target and have to wait a second or two to reacquire it or you may have to delay precious seconds to verify the flag. Is it just me or does the smokestack often obscure the flag at the precise moment you desperately need to see it?

In my experience measuring the range down the firing line is only important when making very long shots or when the target is traveling at a high speed. Normally my crude instruments cannot tell the difference between the range at intersection or at firing as they usually read something like 0.4 rather than 0.39. They can, however, tell me the difference between 4.0 and 3.9. My scientific calculator tells me that at a 12º lead the range will be 2.185% less at the moment of impact. My precious TDC does not permit me to enter the range with that degree of precision, but I try to give it the very highest qualify information possible.

[vanjast]

Have a look at this..

http://www.subsim.com/radioroom/showthread.php?t=213971

There's an adjustment error in the last stage, but up to stage 5 you should get within +-1 knot of ship speed and low AOBs.

At AOBs at 45-90 you should get within +-0.5 Knots.

I'm still busy with the last correction stage, but have parties to attend to
(aaahhhh ...the life of the rich and famous )

[P_Funk]

Originally Posted by GalaKev

As stated above, the range updating, is not shown anywhere, but is updating in the background.

I challenge you to show, using maths only, that you can hit a non standard 90% perpendicular vessel. At 90 AOB, without having a range. I'm not talking a AOB of 89 or 91, but something like 110 degrees. It must update, you could not hit without getting updated calculation. Just because it does not show anywhere does not mean it its not updating.

I haven't played much in a while but this feels incorrect to me. The only thing the TDC really needs in order to hit something is a lead angle, all the variables you feed it serve this end only. Range just never figured as that important in my experience, not insofar as actually getting a valid solution from the TDC at the point of firing.

Perfect example though is the OLC Gui tutorial video. When OLC goes to set up an attack he reads a range of 2600m to the target but mistakenly inputs 1600m. When he fires the torpedo it hits the target anyway (dud from high angle impact but oh well hit is a hit).

That attack actually perfectly meets your criteria too. AOB 55 STB, 7 Knots, with an error in range of around 1000m for a shot above 2000m. I think that says it all.

[Pisces]

Originally Posted by GalaKev

...
This is incorrect, you hit a non 90 shot. You need bearing, speed and range, so that the torp will go off at the correct angle to intercept the target. The AOB is an additional part of the maths, to ensure you hit it square on the side. You will see that the torp will go off at and angle and sweep around after firing to hit the side.

...

I challenge you to show, using maths only, that you can hit a non standard 90% perpendicular vessel. At 90 AOB, without having a range. I'm not talking a AOB of 89 or 91, but something like 110 degrees. It must update, you could not hit without getting updated calculation. Just because it does not show anywhere does not mean it its not updating.

I'm afraid you are incorrect here. Range does not enter the equation for calculating the lead angle (with reference to periscope bearing) to get the torpedo to a moving target. It only determines how long the torpedo takes to get there. AOB, target speed and torpedo speed is sufficient to determine the angle between the periscope bearing and the gyro-angle. Only when the torpedoes have to make a turn after leaving the tube (not 0 gyro angle) does the range get important to correct for a parallax angle offset( the straight run out of the tube and subsequent turn make it come from a slightly different direction) But going straight out of the tube range is no factor in getting it to hit.

The equation for the lead angle of the torpedo towards a moving target can be created from a triangle composed of the target speed, torpedo speed and the AOB. The 'range'-edge of the triangle can be calculated entirely from the other values with trigonometry. And it is a speed also. Again, we rely on the assumption that the gyro angle is 0. (torpedoes do not turn and curve and the uboat/sub is oriented correctly previously) No matter the initial range to the target, the shape of the triangle stays the same. So all angles inside it do also.

According to the "Law of Sines" (wiki) the ratio of opposing sides to the sine of angle is constant for all corners. So:

torpedo speed/sin (AOB) = target speed/sin(lead angle) { = torpedo 'closure rate to target'/ sin(impact angle) }

If you re-arrange it you get:

sin(lead angle) = sin(AOB)* target speed/torpedo speed

And by using the inverse sine function you get the lead angle of course.

As stated above, the range updating, is not shown anywhere, but is updating in the background.

The watch or weapon officer assistance might calculate and show an updating range on the notepad, but that is more likely due to the guy cheating with his divine knowledge of the targets coordinates. Not a sign of TDC functionality. Also, (un)locking the periscope from the target and manuall moving it should (dis)prove the range-updating by the TDC based on target bearing. I've never noticed this. And if he is disabled then this info is not available to the manual operator anyway. Aside from correcting the torpedo turn for this off-bow aiming, the range dial on the F6 page is only used for calculating the impact time.

[EDIT]As for the notepad procedure itself, using this method range is an integral part in this calculation of the target speed. Range that you measured with the stadimeter determines the size of the triangle, and thus speed. AOB that you sighted and entered determines the shape or slenderness of the aiming triangle. The periscope bearing drift while locked on the target, determines how much the target moved in a certain time frame. And this is the angle that closes the aiming triangle. So if you consider it using this method as Ubisoft suggested, then yes range is quite important to get the result. But in reality, only target speed and AOB is important to get the torpedo moving in the right direction.


Also, the perpendicular 90 degree hitting of the target hull is NOT sacred! You can orient your sub any way you like against the target course. It's just wise to do it perpendicular as his broadside gives the most margin against incorrect measurements. Even if your bow is pointed 45 degrees to the target course (or whatever is your fancy) can you get a perfect torpedo-target-encounter! In this case you'll be more successful explosion-wise with magnetic torpedoes passing under the target, rather than impact torpedoes on the hull as they would bounce off. But for the purpose of aiming alone, torpedo steel will meet hull steel no matter what. (assuming no errors made , and no detection in the process)

Make sure the bow is pointed 45 (or 135) degrees to the target course. Set your periscope to 0, flip the update switch on the TDC page to 0, set AOB to 45 (or 135 depending on moving away or closing) in the direction to where the target moves to in the view, and set up target speed. Flip the update switch back to 1. Then swing the periscope until the gyro angle is 0. You are all set (after opening the tube doors. Torpedo will move straight ahead out of the tube to meet the target under a 45 degree angle.

Whatever range angle you enter, the torpedo and TDC won't care. The stopwatch time indicator might show a false impact time. But the torpedo will be on target anyway.

[Zosimus]

I undertook a simple experiment to determine whether the range was important. This was the procedure I followed:

First, I set my TDC speed to zero and turned the bearing until the gyroangle read 000. This is the "true zero" bearing, which on my screen is a hair to the right of the 0º on the slightly-raised observation scope.

Next I set the range for 300 (the minimum), speed 10 knots, AOB 90º Port (I'm currently following a ship and 90º port will be the final AOB at the moment of impact [fingers crossed]). At that point I set the TDC, returned to the observation scope, and turned the scope until the gyroangle read zero.

Next I returned to the TDC, and changed the range to 50,000m. I reset the TDC and returned to the observation scope. The gyroangle now reads 359.

Accordingly I conclude, as a practical matter independent of math concerns, that range can matter in the game I am playing but that such variance will be slight and will not matter for most shots.

[Andrewsdad]

Just two anecdotes regarding two topics raised here.

Target sighted at high stbd angle on bow so I made a end-around approach. This allowed me to make a lot of measurements, including a good 10 minute apart measurement and using the nomograph, determined the tgt speed at 9.5 knots.

It was night and weather was 15 m/s wind with moderate visibility the periscope was difficult to use....

However I got set up for a 90 degree shot with a torpedo run of 700 meters.

Alas... periscope observation and mast-height measurement showed that the target would get pretty close to the arming distance so I needed to shoot early so the torp would arm for sure. So I switched to magnetic exploder and fired with a gyro angle of 320 degrees.

I used the external camera to watch the shot... The torp made the big turn and hit the target right on the bow. Almost a miss ahead !!! I figure that my failure to update the range to target at time of firing was why I almost missed !!! She sank in 10 minutes.


As to the time it takes a target to sink... I hit a tanker straggling from a convoy. Got her just aft the bridge structure. Again the wind/sea were running high. After two hours I put another into her, unfortunately it struck in almost the same place. No more internal torps and couldnt reload externals in the bad weather so I hung around waiting for her to sink or the weather to improve so I could use the deck gun.

"She's going down!" was reported 37 hours later !!!!!! At that point I departed the scene never seeing it actually sink.

One more just for fun.... Another straggler struggling in the heavy seas. End around approach. Target making 3.5 knots, Ideal setup. Observing thru the attack scope, tube #3 open, 15 more degrees to go when..... The crew starts to cheer and she sinks !!!!! A victim of King Neptune seconds before I was to fire !!!!

Ach du Lieber !!!!

AD

[maillemaker]

The short answer is, if you shoot with a 000 gyro angle, range to target does not matter. All that matters is target speed and AOB.

However, a 90 degree AOB attack makes the chance of hit and good impact more likely.

Steve

[Pisces]

Originally Posted by maillemaker

The short answer is, ...

I don't care a bout TL/DR reponses.

[vanjast]

Originally Posted by Andrewsdad

I figure that my failure to update the range to target at time of firing was why I almost missed !!!
AD

You are correct... the TDC range setting is important for Close and Far range targets.
At medium ranges (approx 1500 - 3000m) you can get away with incorrect range settings... but it still effects accuracy if you are looking at 'sniping'.

[Pisces]

With a gyro angle of 320, and the uboat perpendicular to the target track, it's apparent length does seem 25 percent shorter than if it got hit at gyro angle 0. So yeah, significant reduction in margin of error.The range dial could have made a difference. As the correction it makes is larger at short range compared to long range.

[Andrewsdad]

I do believe it is a good habit for Kaleuns to always input range data into the firing solution even if it is a 90 degree shot.
Having a firing routine on a checklist will go a long way toward not missing when the action gets going !!!

Salute !!
AD