The danger of assumption

"Jay Honeck" wrote in message
news:HLAVe.346894$xm3.194258@attbi_s21...
The other night, as we approached rotation speed, we skipped half a dozen
times before breaking cleanly.


1. If there has been a night inversion already starting to develop, your
own motion through the air is causing turbulence and breaking down the
inversion, bringing down air of a different temperature and wind structure.
The conditions that you had while standing still on the apron, are not
exactly the conditions that you are experiencing while hurtling down the
centre line. Whether your AI is reacting quickly enough to the changing
conditions is probably open to debate.

2. A small corollary of 1. If the surface winds were calm, did you check a
recent surface weather chart to see the *likely* wind aloft? If the
pressure configuration indicated a tailwind, the combination of 1 and 2
might result in your symptom.

3. Even if 1 and 2 were not the case, calm winds still have to be watched
carefully. They easily switch to a small tailwind with no notice, which
could make the difference for a light (and lightly-loaded) aircraft. I make
a point to rotate a few knots higher in calm winds just to compensate for
the possibility of a sudden tailwind gust.