FTSearch / ß = ss and ss = ß

In the german language you have the so called sharp s = ‘ß’. This character is written in Switzerland as ‘ss’ and since the German language reform a few years ago also in Germany and Austria.

For years we have already the issue that the users have always to search twice or three times to find the information they want if they search with words containing the sharp s.

We update our web app about once a week with the new information. The new words in there do not contain the sharp s anymore. But some documents could be connected to old documents which contain still the sharp s.

For instance the word ‘Beßerung’ is now written as ‘Besserung’.

What would help us if the sharp s would match also ss as well as ss matchs the sharp s.

ss = ß

ß = ss

Just like it is with

è = e

ä = a

ü = u

Is there a way that I accomplish this or is this inside of the FTIndex?

Note: To change the old documents is not possible because the information is officialy public published information and has to remain unchanged. Also I would have to change about 12Mio documents.