One person suggested they could feel their plane "weathervane" into a crosswind right after takeoff. Another poster concurred.
I suspected we had a "Stick and Rudder" teaching moment. I'll copy and paste a couple of my comments:
Post #1:
A weathervane and a plane on the ground have something in common: a pivot point that the wind can work against. In each case the larger vertical surface aft of the pivot point causes the weathervane or the plane to point into the wind.
But...
At the very instant the plane's tires leave the surface, there's no longer a pivot point for the wind to work against. From that point on, barring gusts, the plane will simply move sideways with the moving air mass with no tendency to point into the wind.
So, where does this illusion come from? I think you hinted at it with "holding correct crosswind control inputs". As the plane leaves the ground, some aileron should still be held into the wind. So the plane begins a turn into the wind, not due to "weathervaning" but simply due to the control inputs.
I'm pretty sure I'm right on this one, but am open to persuasion.
Post #2:
Let me restate that I am perfectly willing to accept that there may be a brief period right after takeoff when a crosswind can weathervane a plane.
But let me make one of two observations...
On zero-zero practice instrument takeoffs and departures, I never recall anyone telling me to look out for weathervaning right after takeoff that would need to be corrected. And I don't think I ever felt a need to warn my students about that.
For instance, taking off on RWY5 with an easterly wind, we would set the heading indicator to the runway heading and apply gradually decreasing right aileron into the wind, maintaining 050° with rudder. By takeoff, if no WCA was called for ("Maintain runway heading") a firm rotation would have the plane climbing wings level on a heading of 050°. I don't ever recall the plane "weathervaning" to 060° or 070° and needing to be steered back to the left to maintain runway heading.
But maybe it's subtle and I missed it. Do any CFII's recall having to teach that weathervaning after takeoff was something that one needed to routinely correct for?
Second observation to follow...
Post #3:
Observation(s) the second...
I have logged about 4,500 hours of dual given over the years, including lots of crosswind takeoffs.
And so I've seen my fair share of takeoffs with inadequate crosswind technique applied.
It sure seems to me that when that happens, the plane just gets "pushed" downwind on whatever heading it's on. Absent any turn to a wind correction angle to compensate for drift, it has not seemed to me that the crosswind "assists" the student in any way by making his WCA for him, via weathervaning or whatever.
Curious as to what other instructors have found.
One fellow, who was an engineer, suggested that for a brief period right after takeoff there would be a "weathervaning" tendency, the "pivot point" being the inertia of the CG, whereby the wind would tend to yaw the plane into it.
Anyway, I channeled Mythbusters and came up with this:
![Image](https://farm4.staticflickr.com/3864/15259501311_0424b47d86.jpg)
Here's the result:
http://youtu.be/NhCFAJybVyw?list=UUIRbX ... AUSLfkBO7w
Probably not a perfect experiment, but to scale the leaf blower was probably producing at least gale force winds at 90º. I would have thought if "weathervaning" was a real thing, we should have seen at least a tiny amount of yaw into it.
Interested in everyone's take, but especially the Professor's!