A Level 1 AOA clarification

On Fri, 31 Dec 2004 at 21:23:58 in message
, Peter Duniho
wrote:
I understand my error regarding chord versus relative wind. Still, I'm
boggled by the lack of induced drag in a wind tunnel. If the wing's not
creating lift (0 AOA), I can see how there wouldn't be induced drag. But
this would happen in the real world too. If the wing is creating lift,
shouldn't there be a measurable force parallel to the relative wind? Even
in a wind tunnel?

You can measure lift in a wind tunnel. Why not induced drag?

Peter,

After posting another long article with a correction I am a bit
reluctant to step in again here. However the explanation is fairly
simple.

Induced drag and wing tip vortices are almost one and the same thing.
Very roughly induced drag is proportional to

(Lift coefficient)^2/(aspect ratio)

The higher the aspect ratio then the smaller is the induced drag until
when the Aspect Ratio is infinite it is zero. Airfoil sections always
used to be tested in wing tunnels by taking them right across the tunnel
so that there are no tip effects. A correction has to be made for the
tunnel wall but the effect is to test a two dimensional section. Of
course there is still the parasitic drag component to be measured and
that is the Cd that is quoted for the particular wing section.

You can try to measure induced drag but you need a large tunnel and a 3d
model of the aircraft sufficiently far from the walls so that the flow
is not too distorted.
--
David CL Francis

David CL Francis

David, I think you mentioned that you were retired aeronautical
engineer of some sort. Can you relate something about your
background? I'm just curious

On Wed, 5 Jan 2005 at 01:56:52 in message
, Greg Esres
wrote:
David CL Francis

David, I think you mentioned that you were retired aeronautical
engineer of some sort. Can you relate something about your
background? I'm just curious

You remember correctly Greg! Who is this guy eh?

I took a degree in Aeronautically engineering many years ago and got
involved mainly in missile design at Filton (It was Bristol Aeroplane
Company then). I did a lot of structural work and then moved into
Engineering management. As the years passed I moved into more and more
other management type jobs but I was delighted that for the last two
years of my career I was able to move back into engineering management.

I have now been retired some years and a lot of my earlier detail
knowledge has drifted away from me. At my age that is not surprising!

I did start learning to fly, went solo but then I gave it up, partly I
was not sure I had the abilities that I thought I should have and also
because I felt I would never be any good at radio work! That tells you
something about how long ago it was because the aircraft I flew had no
radios despite sharing the airfield with a modest number of commercial
flights! One of the highlights of my instruction was a brief spell of
spin recovery training in a Tiger Moth (which does it for you unless you
are quick).

I did a lot of model work later with radio controlled models but
eventually dropped that and found flight simulators.

My first ever flight was with my father in WW2, would you believe, when
he
smuggled me up in a DH Dragonfly! It was being used as a communication
aircraft. My father was a full timer in the RAF and flew in Hendon Air
Displays in 1928-30. My Uncle was also a full time RAF pilot who ended
his flying career as an Instructor in Canada in WW2.

More recent highlights were a successfully take off, circuit and landing
at Hong Kong in the REAL Concorde Simulator at Filton (with just a
little help from the 'instructor') and a ride in the jump seat of a
747-400 flying into Kennedy on the 6th Sept 2001. I'll never get the
chance to do that again! We drove away from New York to Philadelphia on
the 10th Sept 2001 and found all about it in there in company with my
friend who is a regular and respected contributor to this newsgroup. My
wife and I stood on top of the South Tower on Sept 8th 2001.
--
David CL Francis

Who is this guy eh?

Very interesting, thank you! Surprising that you could spend your
life in this field, yet never get the pilot certificate. I'm not sure
I would be interested in the subject if I were not able to fly.

On Fri, 7 Jan 2005 at 05:02:30 in message
, Greg Esres
wrote:
Who is this guy eh?

Very interesting, thank you! Surprising that you could spend your
life in this field, yet never get the pilot certificate. I'm not sure
I would be interested in the subject if I were not able to fly.

Just me I guess Greg. We are all different.

My son was working in South Africa some years ago and he won his Private
Licence out there. In 1989 my wife and I were out there and he took us
for a flight over Johannesburg. Later back here he hired a Warrior and
after a check ride from Filton we made a tour of the district.

Before he left South Africa he checked out on a Cherokee 6 300 and with
three friends (none of them were pilots) went on a touring cruise. They
flew from Johannesburg to the mouth of the Orange River then north
across the Namibian desert to Swakopmund. Then to the airport of
Windhoek to Maun and then across Botswana to Francistown before heading
back to Rand Airport In Johannesburg. Two desert crossings (Namibian and
the Kalahari) 22.4 hours flying and 1012 litres of fuel. He no longer
flies - it is very expensive in the UK and he has his own business to
run. Anyway where in the UK can you fly for 3 hours without being able
to even contact anyone on the radio?

So my son, I am glad to say, has done many things that his father has
not!

If you wish to go to email my reply address should work OK.
--
David CL Francis