I believe this is the old wives tale, that does not go away.
WRT the A-320, it may affect ground speed mini, perhaps that is why you are seeing and increase, although, I cannot say what would cause it in a 76.
Spent 12000 hrs in anything from J-3 Cubs to DC-8, never seen anything remotely like it.
Have done slow flight in the J 3 going backwards over the ground, but even wehen I turned, I did not fail out of the sky.
GS and IAS are to entirely different creatures.
The windshear scenario does not apply, windshear is an abrupt change in wind over a very short distance, it would take some interesting (not to say impossible) maneuvering to achieve this change while turning.
As far as the a/c that crashed into the lake, stallspeed increase with angle of bank, so if the a/c was close to stall, it could very well perpetrate an into the drink, because it stalled. Or, as an aircraft is turned, the pitch has to be increased due to loss of vertical lift component, failure to do so, may cause a/c to go swimming. Then again, perhaps he caught the wingtip, or was flying in ground effect.
The only scenario I can imagine, is one that really cannot be considered flying. See if you can guess it
