Hi Vecko, right now I'm shadowing my next large convoy and strange things are happening
I'm about 10km out if them at ideal visible conditions, but they cannot see me at such distances -that's ok.
I'm at diesel standard ahead, when i order periscope depth to check hydrophone picture, we switch to electric standard ahead.
The problem is, their escorts can hear my electric engines standard ahead while I'm 10 km away.
I found u-boat sound emission model is such as this:
-Diesel is completely silent for enemies and that's ok, because you cannot use it in deep and while you are shallow you are much less able to be heard because of escorts hydrophone cone logic.
- Electric engines are to be heard very very distant while you are between about 0-30m depth from my experiences.
If you are below 50m, you are less able to be detected by hydrophone
The problems about this are these:
- You should be totally stealth just below waterline from few kilometres away because surface ships hydrophones cannot scan surface for such distance, it's illogical even if you imagine, your sound emissions spread much better at between 50-100m and that's even reason while you want to be at this depth if you want to be able to detect ships by your hydrophone at long distances.
- Maybe more important, if you order submerge with standard ahead, 10km away from escort, your crew switch to electric engine and you are detected immediately, until you reach maybe 50m depth, i don't know exactly.
This force me to always shut down engines if i want to submerge and not being detected.
From what i studied submarine war at ww2 at internet, ships hydrophones had simple cone below them, which cannot detect shallow emissions even at few kilometres away, while they could hear more distant engines if they was deeper.
That was reason why German uboats stayed at shallow depths while raided convoys as you can hear at yt directly from Erich Topp interview..
Why i write it here
If you would be able to set condition for escorts to not to hear anything more distant then 5km away while it's between 0-20m depth let's say, even if it's flank ahead, it would remove strange situations like when you submerge 10km away, high wave comes, engines switches to electric for few seconds and you are immediately detected at 10km distance by escorts hydrophone..