There's a way around that slight problem that you can use if you posistion your u-boat very well (90 AOB). It requries a lot of marks on the map, but it's worth it. You line up your shot at 90, and then move your periscope up at 360 or 180 (bow or aft shot), then you AOB calculator on the spreadsheet and set it to 90 (sbd or port) and enter it into the TDC. I adjust the range and speed manually, and then set it to automatic calculation. For example, on the shot I'm lineing up as I type, my 000 gyroagle shot on a 9Knt target is actually at 345 (est 600m range). This thing is wonderful :)

P.S. don't put the periscope up all the way, just barely over the water, helps with the detection factor a lot.

Edit: and it was all for naught. I had this heavy cargo lined up perfectly, and around bearing 310 I made out the flag.... Norwegan! If only I could follow him for 2 months I could sink him!!

AoB 090 is at bearing 000 whether pt or stb. Even approaching at a perpendicular attack angle (not to be confused with AoB 90°), I find I have more success by firing with a 10° or 20° lead.

Before Black May but depending on the escort makeup, may times you can determine speed using the Matching Speed method. The beauty of this the Speed is determined long before you even get in attack position.

Take this time to also determine target course. Overhaul using the dogleg course, and get on a perpendicular attack course.

If you are approaching the target perpendiculary, you will notice a relationship between AoB and Bearing.

For example:

A ship is crossing your path from right to left, and you are on a perpendicular course to the course of the target.

So we know the AoB will be PT because we will be firing at the PT side of the target.

Now when the bearing is 45° you will notice that the AoB is 45° pt. You will also notice that as the bearing moves towards 000°, the AoB moves towards 090°. (If the ship was crossing your path from left to right the AoB would move towards 090° as the bearing moved from 270° towards 000°.)

So if we have the good perpendicular attack course, we know we want to lead the target, so if we are going to fire at bearing 010°, we know the AoB will be 080°pt.

And we figured out the speed by matching our speed on the surface at the edge of visibility. If you receive a contact report on a convoy, the speed is generally within a knot or 2 of the actual convoy speed.

Finally you need range. I use the MILS method, although I'm not sure if the scale on the periscope is actually a MILS scale. Basically, if you measure the length of a ship with the scale on the periscope, it will give you the range if you know the width at a given range.

For example, a C2 Cargo ship is 6 MILS long at 1200m.
A C2 Cargo ship is 12 MILS long at 600m.
A C3 Cargo is 7 MILS long at 1200m and 14 MILS long at 600m.
So by measuring the length of the ship it instantly tells me its range.
The close you are to bearing 000 and AoB 090°, the more accurate the measurement will be. Otherwise you will have to estimate a little bit.

I do not use the notepad, but enter the solution into the TDC manually.