Birds I have thermalled with -

Cape Griffon (White Backed Vultures) thermal very well, but you have to
be careful there is a "vulture restaurant" near the Drakensberg Club
outside Underberg. (Natal Province - South Africa) So sometimes you join
them in a thermal, only to discover they have sought out the descending
air so they can get on the ground for grub. They are gregarious and join
the gliders quite happily. Occasionally you get one clown who thermals
the wrong way and causes chaos.

Bearded vulture - this is a huge bird, which I have only had the
priviledge of flying with once as they don't like gliders and get
aggressive - Based on a sample of one Two up in a K13, and trying to
stay up in the only thermal in the sky trickling off a stony conical
hill. Desperately clinging to about .5kt we got thrashed in the Grob 103
Twin Astir - The Cape Griffon with us were also left in his dust. One
assumes that the massive wings help. I was interested to see the camber
on the wings changing as the bird optimised the smallest variations in
lift. They eat the marrow in bones, so meal times consist of descend to
a carcass, lift off with a heavy ungainly load and climb high - then
drop the bone onto rocks to break it - descend to eat - fly back to
carcase. Repeat. Clearly those that can thermal well get to eat best.

Tawny Eagle on the Platberg ridge also out climbed me - this time in a
K13 - maybe it is the way I fly. We met doing the 180 turn at the end of
one beat. The Eagle turned well inside us and was clearly able to stay
in a very tight , very strong core of lift rising up from a gulley.

Gymnogene - flew a couple of turns with me in a Bergfalke II-55. It was
late afternoon, and I think the motivation was curiosity on the way to
it's roost for the night. I got carefully inspected and then left - at
about the same height. Sample of one does not say much, but despite the
wing aspect ration he was not climbing well. Also - This is the only
solo bird I have had join me in a thermal and turn opposite.

Yellow Billed thermal very well. They have often helped me over the
Vredefort dome - generally marking good lift.Problem is they are so
agile they can use lift which even the Cirrus can't turn in...

European swifts are often to be seen right in the core of strong
thermals at high altitude. The seem to be able to combine hawking
insects and thermalling with relatively little flapping in between the
aerial gymnastics. They really get into the core of the thermal.

Never flown with them but the Bateleur Eagles seem to thermal very well
too.



On 2010/11/15 1:59 PM, Scott Alexander wrote:
So in a recent conversation with a greatly experienced soaring pilot,
I was told that Buzzard's have terrible thermaling skills. I tend to
agree with this as it sure seems Buzzards don't get into the core and
stay there. The lesson learned was don't let Turkey Buzzard show you
where the core is, just let them lead you to the thermal.

I thought it would be interesting to ask you good people if anyone has
any knowledge on these issues. Does anyone know which broad winged
birds have better or worse centering techniques that you can use to
your advantage?

SA

--
Bruce Greeff
T59D #1771 & Std Cirrus #57