I72 driver
Sorry – not very fair of me to set you up like that. Well not you particularly but just anybody who came out with that sort of standard comment.
I said it depended on how quickly you turned and I stick by that. If your mount is a 172 you are quite correct. However some other aircraft have very different capabilities which can change the situation.
Take a Harrier on a heading of north doing 60 kt IAS on a flat calm day. Now change you heading to south in three to four seconds (easily done with full rudder I can assure you). I think you will probably be able to see for yourself that you will end up not with less than about 45 kt of backwards velocity (a bit more than a ‘reduction’ in IAS) because the drag that acts for that brief period of sideways flight is fighting the momentum of eight tons of aircraft doing 60 kt and does not represent much of a 'brake'.
Do this same downwind turn manoeuvre into an original headwind of say 30 kt and you might even die should you let the nose drop a tad so that the backwards IAS can get under your tailplane and blow it over your head.
BOAC knows ‘cos he was a Harrier pilot too.
Regards
JF