Nach gründlicher Überlegung muss ich zugeben dass die "Theoretiker" rund um Torsten vermutlich doch Recht gehabt haben; die nachfolgende Erklärung hat meine Zweifel dann beseitigt:
A lot of folks will ask "...but what about the acceleration required
when the airplane turns form into the wind to an away from the wind
("downwind") direction? This is also a myth. There is no net
acceleration due to the wind in that situation.
Assume we have a plane flying north with a 30 knot airspeed, into a 10
knot headwind. Another way to describe that is to say the plane has a 10
knot "drift" to the south due to the effects of the wind. It's
groundspeed is its airspeed, vector summed with this "drift" due to the
wind speed. In this case, the drift and airspeed are opposite in
direction, so the groundspeed is 20 knots.
Now let's start a 360 degree turn to the left. As the plane reaches a
westerly heading, it's airspeed is still 30 knots, but now to the west
instead of to the north. However, its drift is still 10 knots to the
south, and therefore there has been no acceleration due to the wind. The
drift is at right angles to the plane's path, causing its flight path
to drift sideways over the ground. Its speed through the air
("airspeed") is 30 knots to the west (i.e.: a compass direction of 270
degrees), but its groundspeed is the vector sum of that plus the 10 knot
southward drift, for a groundspeed of about 32 knots to the
west-southwest.
As the plane turns to a southerly heading (course 180 degrees), the
drift due to the wind is still that same 10 knots to the south (and
therefore there has been no acceleration due to the wind), and the
groundspeed is now 10+30, or 40 knots to the south. The airspeed is
still 30 knots, same as before, only its direction has changed.
As the plane turns to the east (heading 90 degrees), the airspeed is
still 30 knots (no change, except it's now to the east), and the wind
drift is still 10 knots to the south (same as it has been, so no
acceleration there), so the groundspeed is now about 32 knots to the
east-southeast.
As the plane turns back to a northerly heading (course 360 degrees) to
complete the turn, the wind drift is still 10 knots to the south, the
airspeed is still 30 knots (but now to the north due to the turn), so
the groundspeed is once again 20 knots to the north.
Note that throughout the turn, the wind drift was always a CONSTANT 10
knots to the south, and therefore imparted no acceleration to the
airplane. The drift that subtracted from the plane's groundspeed when
heading upwind, and added to it when headed downwind, existed as a
sideways drift when the plane was headed crosswind. The drift due to the
wind was always constant in magnitude and direction, and so it never
caused any acceleration of the aircraft, and therefore no change in
airspeed.
Erstaunlich dass man durch selbst Erlebtes (IAS-loss during turn) zufällig eine voreingenommene (falsche) Darstellung in der Ausbildung vermeintlich bestätigt bekommt.
Diverse Spitzen gegen "schicke Streifen" (würde auch lieber im T-Shirt fliegen) oder AF-Unfall in ganz anderem causalen Zusammenhang sind dennoch unangebracht.
