I've bought some new U-boat books recently, and noticed a bit confusion about the abbreviation FAT, of the FAT-torpedo.

The first that caught my attention was in the book "Endgame The U-boat inshore campaign" by John White (ISBN 978 1 86227 485 3): "Fluecher Absuchender Torpedo"
This one I found quite funny, at least it was a very advanced torpedo:-)
White, like many English speaking dosen't use letters like ü and writes it "ue" Then it becomes Flücher ... which leads me to think about the word "Fluch" which means something like "curse" - a curse seeking torpedo!

Then on to Lawrence Paterson
Both in "Dönitz's last gamble. The inshore U-boat Campaign" (ISBN 978 1 84415 714 3) and "Black Flag The surrender of Germany's U-boat forces" (ISBN 978 0 7603 3754 7) in the glossaries, he states that FAT= "Felderapparattorpedo"

It's getting closer, but not quite there, as this would mean something like "Fields apparatus torpedo"

If we go to Jak. P. Mallmann Showell's second US edition (1977) of "U-boats under the swastika" (ISBN 0 668 04290 7), we can read: Flächenabsuch Torpedo. This is close to White's typo and probably the most common wrongly used name for these torpedoes. Fläche means something like "wide area."

Then in Showell's German Navy Handbook (1999) (ISBN 0 7509 3205 8) we finally find the correct definition:
"FAT stood officially for Federapparat-Torpedo, although many people also used the wrong name of Flächenabsuch-Torpedo".
Federapparat would translate into "Spring Apparatus"

Oh by the way, "Federapparat" is also used by Eberhard Rössler in his book "Die Torpedos der deutschen U-Boote" (ISBN 3 8132 0842 7)

Cheers
Vidar