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From: raveling@unify.com (Paul Raveling)
Newsgroups: rec.aviation,rec.birds
Subject: Re: The most competent soaring pilots are...
Keywords: nostalgia
Message-ID: <1990Sep14.164721@unify.com>
Date: 14 Sep 90 23:47:21 GMT
References: <1990Sep11.125658@unify.com> <658@sun13.scri.fsu.edu>
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Reply-To: raveling@unify.com (Paul Raveling)
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In article <658@sun13.scri.fsu.edu>, sandee@sun16 (Daan Sandee) writes:
> In article <1990Sep11.125658@unify.com> raveling@unify.com (Paul
Raveling) writes:

> But they have those advantages ... what about variable geometry? And
those
> self-adjusting slots at the wingtips?

	California Condors may be among the most advanced fliers I've seen.
	Feathers at their wingtips can splay out into an excellent likeness
	of winglets to reduce induced drag in slow flight.  In the late
	'70's I saw some in relatively high altitude high speed flight,
	folding their wings enough to increase wing loading by at least
	50% for better cruise efficiency.  They might even have been
	pushing doubled wing loading.  It also appears to me that they
	reduce their wings' camber in cruising flight, just as flapped
	sailplanes benefit by using negative flaps for cruising.

> Buteos circle at very low speeds - less than 20 mph, I think.

	The hawk who circled with me last weekend appeared to be keeping
	his speed up to more than what he otherwise would have used.
	It's possible that hawks use yet another standard practice of
	safety-conscious soaring pilots:  Keeping a speed that allows
	always easily keeping the neighboring traffic in sight and
	allowing the traffic to keep you in sight.  Of course that's
	lots easier for the hawk because of its superior field of vision
	and visual acuity.

	In this case I was thermaling at 40 knots in about a 45 degree
	bank, so that my turn radius was about 140 feet.  Deriving the
	hawk's speed from his apparent radius suggests about 30 knots.
	From past experience of trying to pace red-tailed hawks in a 1-26
	I'd estimate that 20-25 knots would be a more natural speed
	for them, and they can probably fly comfortably at about 15.
	I haven't yet had a chance to see how fast they fly to penetrate
	heavy sink.


------------------
Paul Raveling
Raveling@Unify.com