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Paul A. Franz, P.E.
Joined: 02 Dec 2008
Posts: 280
Location: Bellevue WA
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 Posted: Sun Mar 15, 2009 8:33 am Post subject: Optimizing speed for range, endurance and practicalities... |
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On Sun, March 15, 2009 12:47 am, JC Propeller Design wrote:
| Quote: |
"JC Propeller Design - Jan Carlsson" <propellerdesign(at)tele2.se>
In general, all airplane, speed for minimum fuel flow isn't the same as the
speed for best range, and non of those speeds is speed stable, you need as
you say be 5 mph or so higher.
There is a speed called Carson (not Carlson) speed, that is best
distance/fuel/time speed, about 1,3 times higher then the best range speed.
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As near as I can tell, "Carson Speed" is something invented by one of the authors of
an excellent article in the September 1993 Sport Aviation.
A month later this article came out.
<http://www.eaa1000.av.org/technicl/perfspds/perfspds.htm>
"Fortunately, the author cited the AIAA paper where Carson developed this concept
(AIAA-80-1847)"
It will tell you how to determine Optimum Cruising Speed (Carson's Speed).
| Quote: | on a drag curve this is the speed where a line drawn from origo touch the
curve.
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Shown here in Fig 1
<http://www.eaa1000.av.org/technicl/perfspds/perfspds.htm#Figure_1>
Here's a good read - two page article from Flying Magazine that makes reference to
Carson and the Carson Score.
<http://www.flyingmag.com/technicalities/755/the-very-best-speed-to-fly.html>
--
Paul A. Franz
Registration/Aircraft - N14UW/Merlin GT
Engine/Prop - Rotax 914/NSI CAP
Bellevue WA
425.241.1618 Cell
No matter what Al Gore may say,
| Quote: | From this there's no running away ...
If things don't get better
|
You'll need a warm sweater;
For now, have a nice sunny day!
Oh shit, that Al Gore's got some clout.
That nasty old man had to shout
We're all gonna die
And the reason why?
Our own precious sun's going out!
Don't care if it worries Al Gore,
I ain't gonna worry no more,
'Cause the Dems have agreed
To cater our need
And let us go drilling offshore.
"Politics are not the high class, marvelous thing that lots of you
picture. Our whole government workings are crammed with 'baloney.'"
-- humorist Will Rogers (1879-1935)
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_________________
Paul A. Franz, P.E.
Registration/Aircraft - N14UW/Merlin GT
Engine/Prop - Rotax 914/NSI CAP
Bellevue WA
425.241.1618 Cell
425.440.9505 Office |
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Float Flyr
Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland
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| Posted: Mon Mar 16, 2009 6:03 am Post subject: Optimizing speed for range, endurance and practicalities... |
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The way I was told to find the best range was a practical one: First set up
as straight and level cruise. Then reduce the rpm by 100 ( direct drive )
and note the corresponding drop in indicated airspeed. Continue with this
until the drop in indicated airspeed takes a bit of a jump then increase
your rpm by 100.
Greatest endurance was also easy just keep reducing the throttle until you
cannot maintain altitude then increase again 100 rpm.
Slowest possible speed was found by attaining the greatest endurance then
lifting the nose and applying power to maintain altitude. Continuing doing
this until you either feel a stall coming on or are at full throttle. This
manoeuvre should only be attempted at altitude. It is sometimes fun to see
the ground going the wrong way if you are pointed into a nice stiff wind.
Noel Loveys
AME Intern, RPP
Kitfox III-A, 912 almost ready to go.
Ivo IFA, Aerocet 1100 floats
--
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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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propellerdesign(at)tele2.
Guest
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| Posted: Mon Mar 16, 2009 6:49 am Post subject: Optimizing speed for range, endurance and practicalities... |
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For those that want to test,
you can fly, say at your normal cruising alt. testing as stated below, every
100 rpm, or 2 or 300 on a geared engine, flying in all 4 directions reading
the GPS and IAS, fuel flow (for those with that feature) and RPM.
put this info in a table and why not in excel, make diagram over fuelflow /
TAS and you get the miles per gallon ...
Jan
Ps you also get a calibration of air speed indicator if you have OAT meter
to get your density alt.
---
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