Three times, in a glider, I have realised on aerotow that the ASI made no sense at all. Though the tow plane was climbing steadily, the ASI read ZERO!, and then the needle moved right round the dial until it read 350 k...
Clearly it was lying. As we were still flying.
So on coming off tow I did a bit of flying round, actually quite a lot as it was a good day, to get used to the air sounds, the attitude. Coming in to land, a little bit faster than normal, but on all three occasions no problem.
Must remember to take the electrician's tape off the pitot and static ports...