ON THE OTHER HAND

When entering a thermal not already marked by a circling glider, which way should you turn?  Toward it of course, if you know which side it’s on.  But that’s not always certain at first, so what other rationales might there be?

Everyone agrees on flying our circles against any lateral rotation, if it exists, but that’s seldom apparent either.  One old timer said that since most dust devils in the northern hemisphere rotate counterclockwise due to Coreolis effect, he always turned clockwise, i.e. to the right.  Okay, but even if there is lateral rotation, it’s typically very minor (except in dust devils) and will approach zero not far above ground level anyway…   Another pilot always turned left regardless of any other considerations, because that’s required for competition where he came from in Europe.  Other than solving the problem of folks occasionally circling opposite directions, these strategies seem more trouble than they’re worth.  And there are others that confuse the issue even further.

All other factors being equal, I nearly always make that first turn into the prevailing wind, left or right.  My rationale:  every thermal drifts in the wind as it rises, so an infrared snapshot would show the thermal leaning downwind (visualize this schematically and think it through so you really understand it).  Because air rising toward you comes from the windward direction, if you turn downwind and don’t find lift you descend through the sinking air beneath the thermal while it continues to rise, and you’ll need to fly an upwind leg to relocate that thermal at some lower point further away.  But if you turn into the wind and away from lift you’ll be descending into space from which lower, newer pulses continue to rise, and simply continuing your circle will probably bring you back into lift with minimal loss of altitude or time.

It’s a big sky and which way you turn for any particular thermal is, usually, a small stakes gamble.  There’s plenty of room up there for you to devise your own strategy.  Meanwhile, in any possible scenario from aborted takeoff to crash landing, if you’re unsure which way to turn, the best default is into the wind.