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From: sandee@sun16 (Daan Sandee)
Newsgroups: rec.aviation,rec.birds
Subject: Re: The most competent soaring pilots are...
Keywords: nostalgia
Message-ID: <658@sun13.scri.fsu.edu>
Date: 12 Sep 90 13:37:03 GMT
References: <1990Sep11.125658@unify.com>
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In article <1990Sep11.125658@unify.com> raveling@unify.com (Paul Raveling) writes:
>	Sunday, while soaring near Minden, I had another of those
>	rare encounters with a red-tailed hawk -- with the hawk joining
>	up in the thermal I'd found.  I still find it damned exhilarating
>	and take it as a compliment from the expert -- the hawk, that is.
That brings back fond memories of long ago ... the same thing happened to me
several times, in Europe. My soaring companion then was the Common Buzzard
(Buteo buteo).
>
>	A sign that I'd centered the thermal well was that the hawk
>	flew a smaller circle, concentric with mine, and even briefly
>	flew in formation about 10 meters off my inside wingtip.  Note
>	that hawks obey the same safety rule that we sailplane pilots do:
>	Anyone entering a thermal circles in the same direction as
>	whoever is already in it.
>	[...]            I have nothing but admiration for these
>	feathered folks' flying skills, and they're probably exercising
>	some skills that we're not even aware of.
But they have those advantages ... what about variable geometry? And those
self-adjusting slots at the wingtips? And all those multiple flexible
control surfaces at the rear end? Note also that raptors have a trick of 
extending their landing gear to slow down, something that sailplane pilots
wouldn't want to do.
Buteos circle at very low speeds - less than 20 mph, I think. This makes for
a smaller turning circle, so they can use the core of the thermal ; or,
fly a bigger circle at less angle of bank, with a lesser rate of sink. From
what I've noticed, their angle of bank is usually somewhat less than a
sailplane's. Their gliding performance between thermals is lousy, though ;
their cross-country performance can't be much. If a migrating soaring bird
meets a headwind, it just gives up and waits for the wind to change. I know
there are records of migrating species that average hundreds of miles a day,
but they must be wind-assisted. Still, Swainson's Hawk does a 7,000-mile
trip twice yearly between the U.S. and Argentina ; in the Old World, White
Stork (alas, much less common than formerly) travels between N.W.Europe and
Southern Africa, which is about the same distance.
Once I had a similar encounter with a gull - I am ashamed to say, I didn't
notice which species, but I can assume it was Herring Gull (Larus argentatus).
This species circles at a much higher speed - 40 mph, I suppose - because of
the much higher wing loading. I got on its tail and was overtaking it ; it
kept looking nervously over its shoulder and tried evasive action ; I chased
it around the thermal for several minutes (please, no flames ; this was before
my birding days, and it was only a stupid gull) and I kept up with it nicely
- it had the advantage of mobility and I of speed - until the bird cheated :
it started flapping its wings and left me in an upward direction. Another
unfair advantage ...
>
>------------------
>Paul Raveling
>Raveling@Unify.com

Daan Sandee                                           sandee@sun16.scri.fsu.edu
Supercomputer Computations Research Institute
Florida State University, Tallahassee, FL 32306-4052  (904) 644-7045