Today's Message Index:
----------------------
1. 06:40 AM - Cat fight (Nathan Ulrich)
2. 07:04 AM - Re: Cat fight (Hinde, Frank George (Corvallis))
3. 10:41 AM - Re: Alternator Field Breaker/Switch (Jerry2DT@aol.com)
4. 11:02 AM - Re: Schematics: turbo cad and Z-11 (LarryMcFarland)
5. 01:16 PM - Re: Alternator Field Breaker/Switch (Brian Lloyd)
6. 06:47 PM - Re: Re: AeroElectric-List Digest: 7 Msgs - 05/22/06 (Kevin Horton)
7. 10:50 PM - Re: Aircraft performance (was Antennas) (Speedy11@aol.com)
Message 1
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--> AeroElectric-List message posted by: "Nathan Ulrich" <nulrich@technq.com>
Math is beautiful, but more so when it's accurate ;).
If you were calculating the speed increase for a car, you'd be pretty close
assuming that speed increases with the cube root of power, but it's not
quite true for an airplane.
The power required to overcome parasitic drag (that of the non-lifting
surfaces) increases proportionally to the cube of the velocity, but the
induced drag (that of the wing) actually decreases with increasing speed.
The lift required to maintain altitude remains the same, but the required
wing angle of attack decreases as the speed increases (lift is proportional
to the square of the speed) so the drag of the wing decreases.
Also, as you go faster, the advance ratio of your propellor increases, which
typically makes the propellor more efficient.
Of course, the overall result is that power required still increases
exponentially with speed, but it's not nearly as bad as the cube. How much
will depend a lot on where on the L/D curve you are, but for typical cruise
speeds in my Bonanza, adding 10% power results in about a 5% speed increase.
At just above best glide (max L/D) speed, where the drag curve is very flat,
adding 10% power results in a 9% increase in speed.
Nathan
Time: 08:27:05 AM PST US
From: Hopperdhh@aol.com
Subject: Re: AeroElectric-List: Re: AeroElectric-List Digest: 7 Msgs -
05/22/06
--> AeroElectric-List message posted by: Hopperdhh@aol.com
Ah! I agree, I'm not a cat either, but a simple engineer. Let's see, drag
goes up as the square of speed so power required goes up as the cube of
speed.
(Power=force x velocity) Force in this case is the thrust required to
overcome the drag. Now, the cube root of .75 is 0.90856. So we should
expect
speed at 75 percent power to be 91 percent of the speed at 100 percent
power.
Isn't math beautiful?
Dan Hopper
RV-7A Flying 164 hours now. What a wonderful airplane!
In a message dated 5/23/2006 10:43:33 A.M. Eastern Daylight Time,
frank.hinde@hp.com writes:
Not to jump into the middle of so delicious a cat fight, but you guys might
be interested in this data. I have an insurance company database with
manufacturers specified horsepower, max speed, and 75% cruise speed numbers
for 440 (mostly American) light aircraft. The average horsepower is 220.5,
average top speed is 164.4 knots, and the average manufacturers claimed 75%
power cruise speed is 153.5 knots. That works out to 93.4% of the average
top speed.
Regards,
Lee...
Message 2
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--> AeroElectric-List message posted by: "Hinde, Frank George (Corvallis)" <frank.hinde@hp.com>
For some years I have wondered how this worked...I mean if induced drag
increased with speed then lift AND altitude would increase with
speed....So induced drag decreases with speed...Thankyou!
Frank...Simple mechanical engineer..:)
Do not archive
The lift required to maintain altitude remains the same, but the
required wing angle of attack decreases as the speed increases (lift is
proportional to the square of the speed) so the drag of the wing
decreases.
Message 3
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| Subject: | Re: Alternator Field Breaker/Switch |
--> AeroElectric-List message posted by: Jerry2DT@aol.com
Brilliant! I have passed this on to my Electron-challenged associates...
Thanks Brian.
Jerry Cochran
In a message dated 5/24/2006 12:05:43 A.M. Pacific Daylight Time,
aeroelectric-list@matronics.com writes:
From: Brian Lloyd <brian-yak@lloyd.com>
Subject: Re: AeroElectric-List: Alternator Field Breaker/Switch
--> AeroElectric-List message posted by: Brian Lloyd <brian-yak@lloyd.com>
On May 22, 2006, at 7:19 PM, Mark Chamberlain wrote:
> information on how to wire it, but as to the questions "why?", or what
> does the "field" wire do ; I can find nothing. I'm guessing it is a
> very
> simple answer and it is just my inexperience showing through.
If you go back to an elementary science class, someone once told you
that if you wave a magnet around a wire, that wire will produce an
electric current. They also probably told you that if you pass a
current through a wire it will produce a magnetic field around the
wire. This was the amazing discovery of Michael Faraday and upon
which all electrical and radio theory is based.
Message 4
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| Subject: | Re: Schematics: turbo cad and Z-11 |
--> AeroElectric-List message posted by: LarryMcFarland <larry@macsmachine.com>
Tom,
The link below is a schematic which was derived of the Z-11 and modified
to my engine and ignition setup.
I also have it in TurboCAD if you'd like the file to modify it to your
own purpose. It's less an electrical
drawing than a schematic that works for me. Just click on the link and
when it's up, click again to see it close
or print it to a standard sheet. I'll send you the TurboCAD file if you
want it.
http://www.macsmachine.com/images/electrical/full/primary-wiring.gif
Larry McFarland - 601HDS at www.macsmachine.com
do not archive
sarg314 wrote:
>--> AeroElectric-List message posted by: sarg314 <sarg314@comcast.net>
>
>I was looking over the cad software that is supplied on the Aeroelectric
>CDROM. Turbo cad looks quite usable. Does Bob, or any one have the
>standard Z-11 schematic already rendered in a turbo cad file? It would
>save a lot of work compared to starting from scratch.
>--
>Tom Sargent
>RV-6A
>
>
>
>
Message 5
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| Subject: | Re: Alternator Field Breaker/Switch |
--> AeroElectric-List message posted by: Brian Lloyd <brian-yak@lloyd.com>
Jerry2DT@aol.com wrote:
> --> AeroElectric-List message posted by: Jerry2DT@aol.com
>
>
> Brilliant! I have passed this on to my Electron-challenged associates...
> Thanks Brian.
You are welcome. Sometimes we get so involved in a detailed discussion
of the trees we forget how interesting the forest is.
Brian
Message 6
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| Subject: | Re: AeroElectric-List Digest: 7 Msgs - 05/22/06 |
--> AeroElectric-List message posted by: Kevin Horton <khorton01@rogers.com>
On 23-May-06, at 11:22 AM, Hopperdhh@aol.com wrote:
> --> AeroElectric-List message posted by: Hopperdhh@aol.com
>
>
> Ah! I agree, I'm not a cat either, but a simple engineer. Let's
> see, drag
> goes up as the square of speed so power required goes up as the
> cube of speed.
> (Power=force x velocity) Force in this case is the thrust
> required to
> overcome the drag. Now, the cube root of .75 is 0.90856. So we
> should expect
> speed at 75 percent power to be 91 percent of the speed at 100
> percent power.
>
> Isn't math beautiful?
Math is beautiful, but it can mislead you too.
For an aircraft with a normally aspirated engine, it can only produce
100% power at sea level. So, that means that the max speed with 100%
power is at sea level. The speed with 75% power at sea level should
be about 91% of the speed with 100% power, as you calculated.
However, if we keep the power level the same (i.e. 75%), and we
increase the altitude, the true airspeed will increase, as the air
density is lower, and thus the drag is lower. So, the speed at 75%
power will be highest at the highest altitude at which the engine can
produce 75% power. This will probably be somewhere around 8,000 ft,
and the speed at 75% power at this altitude will be more than 91% of
the speed with 100% power at sea level.
Kevin Horton
RV-8 (Finishing Kit)
Ottawa, Canada
http://www.kilohotel.com/rv8
Message 7
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| Subject: | Re: Aircraft performance (was Antennas) |
--> AeroElectric-List message posted by: Speedy11@aol.com
In a message dated 05/23/06 3:02:39 AM Eastern Daylight Time,
aeroelectric-list@matronics.com writes:
Hope I didn't ruffle too many feathers.
Gilles,
I doubt you ruffled any feathers. Personally, I find your comments
entertaining, so keep them coming.
I also admire anyone who builds an airplane in Europe. The rules and
restrcitions are much more severe than in the US - and the cost of fuel is almost
prohibitive. Not to mention the cost of avionics, paint, interior, etc. All is
more expensive in Europe and more difficult to obtain.
My hat's off to you.
Stan Sutterfield
Do not archive
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