more confusion on cessna performance chart

[terry]

A little while ago I started a thread about why a Cessna landing
peformance chart showed a climb wt limit that was pressure altitude
rather than density altitude dependant. Well now I am similarly
confused by a different performance table ( not a chart this time)
which shows the take off distance required for a C172N. This table
shows the distance required as a function of pressure altitude form 0
to 8000 ft ( in steps of 1000 ft) and temperature of 0 to 40 deg C in
steps of 10 deg C. This table comes from the flight manual of the
aircraft.

Now I thought it would be a useful addition to my Excel flight fomulas
to convert all this data into a graph of distance required vs density
altitude and fit an equation to it, so then I could just enter density
altitude and the program would calculate distance required ( with
corrections for wind etc)
Well the problem is that where the density altitude ranges overlap for
the different temperatures the distance required differs with the
lower the temp, the higher the distance required for the same density
altitude.

At around 8000 ft density altitude the difference was like 300 ft
between 0 and 40 deg C which is quite significant. I am pretty sure I
know how to calculate density altitude, but just in case here is how I
do it,

Take the pressure altitude and correct for temperature as follows.
eg for 3000 ft pressure altitude and 30 deg C. ISA temp would be
(15-3x2)=+9 C, so we are 21 C over ISA temp. 21*120 =2520 +3000
=5520 ft density altitude

So why would the takeoff distance required vary with temperature at
the same density altitude?, it goes against everything I understood
about peformance being a function of the air density.

Any help appreciated.
Terry
PPL downunder

[TakeFlight]

Rolling resistance of tires?

Hard to say what Cessna's assumptions are, especially when they didn't
include their formula, just a data set.

[Dallas]

On Mon, 14 Jan 2008 12:56:46 -0800 (PST), terry wrote:

> So why would the takeoff distance required vary with temperature at
> the same density altitude?

I confess that I'm lazy today and didn't read what you said for
comprehension, but I will address the above statement.

DA mantra:
Density altitude is pressure altitude corrected for non-standard
temperature.

Ok, so if DA has been corrected for temperature, then we're done.

The "vary with temperature" part of your statement doesn't make any sense
if you are using DA, the temperature factor has been applied already. You
wouldn't apply temperature again to come up with an answer.

The statement above would make sense if you said: The takeoff distance
required will vary with temperature at the same "pressure altitude".


--
Dallas

[quietguy]

Your PA-to-DA calculations clearly differ from Cessna's, probably
because they used a different standard atmosphere. There are plenty
to choose from: International SA, U.S. SA, ICAO SA (all revised over
the years) and some others, some of which are no longer used. You'd
need to find out which SA was used by Cessna when the 172N was built.
Good luck with that project. I would just plot some points from the
POH and draw a smooth curve connecting them; I'd be conservative in my
choices of data points and call that good enough.

[terry]

On Jan 15, 9:49*am, Dallas > wrote:
> On Mon, 14 Jan 2008 12:56:46 -0800 (PST), terry wrote:
> > So why would the takeoff distance required vary with temperature at
> > the same density altitude?
>
> I confess that I'm lazy today and didn't read what you said for
> comprehension, but I will address the above statement.
>
> DA mantra:
> Density altitude is pressure altitude corrected for non-standard
> temperature.

I agree
> Ok, so if DA has been corrected for temperature, then we're done. *

> The "vary with temperature" part of your statement doesn't make any sense
> if you are using DA, the temperature factor has been applied already. *You
> wouldn't apply temperature again to come up with an answer.

No I havent corrected twice, the point of the post was that after
correcting pressure altitude for temperature to get density altitude,
different combinations of pressure altitude and temperature which
result in the same calculated density altitude give different
performance figures.
>
> The statement above would make sense if you said: *The takeoff distance
> required will vary with temperature at the same "pressure altitude".

yes it would make sense but then I would have had no need post the
problem, which is that the same density altitude calculated using
different combinations of pressure altitude and temperature do not
give the same performance. For example, Dallas if the presssure
altitude as 5000 ft and temp was 10 dec C, that would be a density
altitude of 5520 ft.
Now I could get the same density altitude of 5520 ft if I had a
pressure altitude of 3000 feet and a temperature of 30 C . Do we
agree on that? I I would then expect that the takeoff distance
required for either of these 2 scenarios would be the same. The point
of the post being that this not the case with the data set in the
table.

I could have explained it a lot better with graphs but I dont think
you can do that on usenet.

Terry

[terry]

On Jan 15, 10:24*am, quietguy > wrote:
> Your PA-to-DA calculations clearly differ from Cessna's, probably
> because they used a different standard atmosphere. *There are plenty
> to choose from: International SA, U.S. SA, ICAO SA (all revised over
> the years) and some others, some of which are no longer used. *You'd
> need to find out which SA was used by Cessna when the 172N was built.
> Good luck with that project. *I would just plot some points from the
> POH and draw a smooth curve connecting them; I'd be conservative in my
> choices of data points and call that good enough.

Good point , perhaps that is the issue,the data I have do not specifiy
what standard atmosphere.

Thanks
Terry

[Dallas]

On Mon, 14 Jan 2008 16:20:34 -0800 (PST), terry wrote:

> I could have explained it a lot better with graphs but I dont think
> you can do that on usenet.

I've been known to use graphics to ask questions here.. like this:

http://img.photobucket.com/albums/v101/Dallas52/Dallas/RangeProfileChart.jpg

--------------
Oh, and this might interest you... as mentioned in an other post, the
algorithms to determine DA are not "fixed" they are a black art of sorts.
Here's a good example, two of the same model but different editions of an
electronic E6B with the same values entered yield two different answers for
DA & PA.

http://img.photobucket.com/albums/v101/Dallas52/Dallas/BothSportysE6B.jpg

Go figure.
--
Dallas

[[email protected]]

> So why would the takeoff distance required vary with temperature at
> the same density altitude?, it goes against everything I understood
> about peformance being a function of the air density.
>
> Any help appreciated.
> Terry
> PPL downunder

I wonder if Cessna used formulas at all. I would think rather not.
They probably measured all of those values during the certification
process. I don't see how any aircraft could get its performance info
certificated based solely on mathematical calculations. You have to
test the plane for realiable data.

If I'm right and all those data points come from actual flight data
(and an average of that, too), then it's not a big surprise that
simple calculations regarding density altitude don't seem to make
sense.

Also density altitude calculations that consider only temperature are
at best approximations -- good enough ones for most conditions,
probably. But density altitude is also dependent on moisture content
of the air, which is perhaps even less known in a given air parcel
than temperature.

Has anyone on the list ever worked with or for Cessna who might know
how they generate their performance charts? Experimental measurement
-- or calculated "guess"?

[terry]

On Jan 15, 11:20*am, terry > wrote:

*For example, Dallas if the presssure
> altitude as 5000 ft and temp was 10 dec C, that would be a density
> altitude of *5520 ft.

DOH not a good example that should have been 5000 ft and 9.3 deg C to
give 5520 ft

> Now I could get the same density altitude of 5520 ft if I had a
> pressure altitude of * 3000 *feet and a temperature of 30 C . Do we
> agree on that? *I I would then expect that the takeoff distance
> required for either of these 2 scenarios would be the same. *The point
> of the post being that this not the case with the data set in the
> table.
>
> I could have explained it a lot better with graphs but I dont think
> you can do that on usenet.
>
> Terry

[[email protected]]

> Has anyone on the list ever worked with or for Cessna who might know
> how they generate their performance charts? Experimental measurement
> -- or calculated "guess"?

To answer my own question: in the USA FAR part 23 describes in
excruciating detail how these data charts have to be created and I
excerpt for GA (a bit wily nily):

Sec. 23.45

General.

(a) Unless otherwise prescribed, the performance requirements of this
part must be met for--
(1) Still air and standard atmosphere; ...

(b) Performance data must be determined over not less than the
following ranges of conditions--
(1) Airport altitudes from sea level to 10,000 feet; and
(2) For reciprocating engine-powered airplanes of 6,000 pounds, or
less, maximum weight, temperature from standard to 30° C above
standard; ...

(f) Unless otherwise prescribed, in determining the takeoff and
landing distances, changes in the airplane's configuration, speed, and
power must be made in accordance with procedures established by the
applicant for operation in service. These procedures must be able to
be executed consistently by pilots of average skill in atmospheric
conditions reasonably expected to be encountered in service.

(g) The following, as applicable, must be determined on a smooth, dry,
hard-surfaced runway--
(1) Takeoff distance of Sec. 23.53(b);
(2) Accelerate-stop distance of Sec. 23.55;
(3) Takeoff distance and takeoff run of Sec. 23.59; and
(4) Landing distance of Sec. 23.75.
NOTE: The effect on these distances of operation on other types of
surfaces (for example, grass, gravel) when dry, may be determined or
derived and these surfaces listed in the Airplane Flight Manual in
accordance with Sec. 23.1583(p).

Note the word "determined", not "calculated" or "derived" for all
except the bit about types of surfaces, where "derivation" is allowed.

There are a LOT of variables in those rules that don't lend themselves
to mathematical expressions. My conclusion is that there is no simple
formula available to apply in an Excel spreadsheet that will reliably
predict the numbers from the chart, thus your calculations seem to
have contradictory results (eg, different performance for same density
altitude).

Of course, someone with more experience in aircraft certification /
performance data generation will probably post something right away
showing I don't know a damned thing and my conclusions are completely
wrong. ;)

[terry]

On Jan 15, 11:58*am, wrote:
> > So why would the takeoff distance required vary with temperature at
> > the same density altitude?, it goes against everything I understood
> > about peformance being a function of the air density.
>
> > Any help appreciated.
> > Terry
> > PPL downunder
>
> I wonder if Cessna used formulas at all. I would think rather not.
> They probably measured all of those values during the certification
> process. I don't see how any aircraft could get its performance info
> certificated based solely on mathematical calculations. You have to
> test the plane for realiable data.
>
> If I'm right and all those data points come from actual flight data
> (and an average of that, too), then it's not a big surprise that
> simple calculations regarding density altitude don't seem to make
> sense.
>
> Also density altitude calculations that consider only temperature are
> at best approximations -- good enough ones for most conditions,
> probably. But density altitude is also dependent on moisture content
> of the air, which is perhaps even less known in a given air parcel
> than temperature.
>
> Has anyone on the list ever worked with or for Cessna who might know
> how they generate their performance charts? Experimental measurement
> -- or calculated "guess"?

good points, but the data looks too smooth to me to be entirely
based on experiment, although obviously some of it must be..
I dont think moisture is the issue. the effect of moisture on air
density really only becomes significant at higher temperatures and if
this were the factor in play
then you would expect the higher temperature data to have the worse
performance ( moisture lowers the density and even at 100% relative
humidity there is very little water in air at 0 dec C)
The data actually show the opposite effect. if you plot take off
distance vs density ht. you can see 4 distinct curves wtih from top to
bottom, density altitude calculated at 1, 10,20,30 and 40 deg C
respectively. They are all smooth curves which fit a binomial
equation quite nicely. No I think the use of a different method to
convert pressure altitude to density altitude seems like the best
explanation.

terry

[terry]

On Jan 15, 9:02*am, TakeFlight > wrote:
> Rolling resistance of tires?
>
> Hard to say what Cessna's assumptions are, especially when they didn't
> include their formula, just a data set.

I would think rolling resistance would be less at lower temperatures.
rubber softens at higher temps and gets a better grip. the data shows
the reverse , at lower temps for the same density altitude the
distance required is higher.

[RST Engineering]

There is a very excellent text with derived equations for almost anything
having to do with flight. "The Axioms Of Flight" by James Embree, ISBN
0-9601062-7-8. I have most of the equations plugged into either Excel or
Basic and mostly they agree with "manufacturer's data" within an rch.

Jim

[terry]

On Jan 16, 4:18*am, "RST Engineering" > wrote:
> There is a very excellent text with derived equations for almost anything
> having to do with flight. *"The Axioms Of Flight" by James Embree, ISBN
> 0-9601062-7-8. *I have most of the equations plugged into either Excel or
> Basic and mostly they agree with "manufacturer's data" within an rch.
>
> Jim

Thanks for the reference. BTW what is an rch?
Terry

[RST Engineering]

It is a steeped-in-tradition engineering convention used to describe
something that is very, very close to the correct answer. It derives from
the very fine hair found on the lower-midsection of the adult female, of
which the red has been experimentally found to be the smallest in diameter.

It took centuries of trial and measurement to prove this experiment correct
{;-)


Jim
--
"If you think you can, or think you can't, you're right."
--Henry Ford




Thanks for the reference. BTW what is an rch?
Terry

[Jim Macklin]

roflol, what kinds of experiments are/were needed to prove
the axiom?



"RST Engineering" > wrote in message
...
| It is a steeped-in-tradition engineering convention used
to describe
| something that is very, very close to the correct answer.
It derives from
| the very fine hair found on the lower-midsection of the
adult female, of
| which the red has been experimentally found to be the
smallest in diameter.
|
| It took centuries of trial and measurement to prove this
experiment correct
| {;-)
|
|
| Jim
| --
| "If you think you can, or think you can't, you're right."
| --Henry Ford
|
|
|
|
| Thanks for the reference. BTW what is an rch?
| Terry
|
|

[RST Engineering]

"Jim Macklin" > wrote in message
...
> roflol, what kinds of experiments are/were needed to prove
> the axiom?

Don't get me started. You know how I am...



Two guys walking down the sidewalk and pass a good looking brunette.

"Ever sleep with a brunette?" "Yeah, I've slept with a few brunettes."

They pass a beautiful blonde.

"Ever sleep with a blonde?" "Yeah, I've slept with a few blondes."

They pass a KNOCKOUT redhead.

"Ever sleep with a redhead?" "Not a wink."




Jim


>
>
>
> "RST Engineering" > wrote in message
> ...
> | It is a steeped-in-tradition engineering convention used
> to describe
> | something that is very, very close to the correct answer.
> It derives from
> | the very fine hair found on the lower-midsection of the
> adult female, of
> | which the red has been experimentally found to be the
> smallest in diameter.
> |
> | It took centuries of trial and measurement to prove this
> experiment correct
> | {;-)
> |
> |
> | Jim
> | --
> | "If you think you can, or think you can't, you're right."
> | --Henry Ford
> |
> |
> |
> |
> | Thanks for the reference. BTW what is an rch?
> | Terry
> |
> |
>
>

[Ken S. Tucker]

On Jan 14, 8:57 pm, terry > wrote:
> On Jan 15, 11:58 am, wrote:
>
>
>
> > > So why would the takeoff distance required vary with temperature at
> > > the same density altitude?, it goes against everything I understood
> > > about peformance being a function of the air density.
>
> > > Any help appreciated.
> > > Terry
> > > PPL downunder
>
> > I wonder if Cessna used formulas at all. I would think rather not.
> > They probably measured all of those values during the certification
> > process. I don't see how any aircraft could get its performance info
> > certificated based solely on mathematical calculations. You have to
> > test the plane for realiable data.
>
> > If I'm right and all those data points come from actual flight data
> > (and an average of that, too), then it's not a big surprise that
> > simple calculations regarding density altitude don't seem to make
> > sense.
>
> > Also density altitude calculations that consider only temperature are
> > at best approximations -- good enough ones for most conditions,
> > probably. But density altitude is also dependent on moisture content
> > of the air, which is perhaps even less known in a given air parcel
> > than temperature.
>
> > Has anyone on the list ever worked with or for Cessna who might know
> > how they generate their performance charts? Experimental measurement
> > -- or calculated "guess"?
>
> good points, but the data looks too smooth to me to be entirely
> based on experiment, although obviously some of it must be..
> I dont think moisture is the issue. the effect of moisture on air
> density really only becomes significant at higher temperatures and if
> this were the factor in play
> then you would expect the higher temperature data to have the worse
> performance ( moisture lowers the density and even at 100% relative
> humidity there is very little water in air at 0 dec C)
> The data actually show the opposite effect. if you plot take off
> distance vs density ht. you can see 4 distinct curves wtih from top to
> bottom, density altitude calculated at 1, 10,20,30 and 40 deg C
> respectively. They are all smooth curves which fit a binomial
> equation quite nicely. No I think the use of a different method to
> convert pressure altitude to density altitude seems like the best
> explanation.
> terry

http://en.wikipedia.org/wiki/Density_altitude
http://en.wikipedia.org/wiki/Pressure_altitude

Humidity feeds into "density altitude" because water
vapour molecule H2O has density ~ 10 compared to
Nitrogen N2 ~ 14 *at equal pressures*.

I'm guessing: but I get the impression that the onset
of turbulence over wings was also dependant on temp-
erature, even when the density altitude is the same.
In Quantum Theory that makes sense.
To start, warm air is more chaotic than cold air at the
molecular level, and the chaos *seeds* the turbulence.
You know, hot fluids are less viscous than cold and so
less sticky. That's likely a secondary correction.
Regards
Ken

[RST Engineering]

O ??????

Jim

--
"If you think you can, or think you can't, you're right."
--Henry Ford


>> It took centuries of trial and measurement to prove this experiment
>> correct {;-)
>
> ORCH

[Matt Whiting]

terry wrote:
> On Jan 15, 9:02 am, TakeFlight > wrote:
>> Rolling resistance of tires?
>>
>> Hard to say what Cessna's assumptions are, especially when they didn't
>> include their formula, just a data set.
>
> I would think rolling resistance would be less at lower temperatures.
> rubber softens at higher temps and gets a better grip. the data shows
> the reverse , at lower temps for the same density altitude the
> distance required is higher.

Stiff tire sidewalls are harder to flex and thus absorb more energy in
the process. This is why radial tires, even though they flex more, have
lower rolling resistance than bias ply tires. It isn't intuitive, but
it is reality.

Matt

[terry]

On Jan 16, 4:44*am, "RST Engineering" > wrote:
> It is a steeped-in-tradition engineering convention used to describe
> something that is very, very close to the correct answer. *It derives from
> the very fine hair found on the lower-midsection of the adult female, of
> which the red has been experimentally found to be the smallest in diameter..
>
> It took centuries of trial and measurement to prove this experiment correct
> {;-)
>
>Well thanks for that Jim. Downunder we have a similar but slightly less technical saying for something that is very close. It is called "within a bees dick"

Terry

[terry]

On Jan 16, 7:05*am, "Ken S. Tucker" > wrote:
> Humidity feeds into "density altitude" because water
> vapour molecule H2O has density ~ 10 compared to
> Nitrogen N2 ~ 14 *at equal pressures*

Not quite. The density is proportional to molecular weight, which
would be in the ratio of 18 for water to 28 for nitrogen ( g /mol )
But of course we are really interested in the density ratio between
water and air which would be 18 to 28.9

Ths simply comes from rearranging the Gas Equation we all learn in
high school
PV =nRT
substiute n =m/M where m is mass and M molecular weight , you
rearrange to get
m/V = PM / RT
m/V of course = density
( assuming ideal behaviour exists which is a pretty good assumption at
the pressures and temperatures involved in flying light aircraft ).

> I'm guessing: but I get the impression that the onset
> of turbulence over wings was also dependant on temp-
> erature, even when the density altitude is the same.
> * In Quantum Theory that makes sense.
> To start, warm air is more chaotic than cold air at the
> molecular level, and the chaos *seeds* the turbulence.
> You know, hot fluids are less viscous than cold and so
> less sticky. That's likely a secondary correction.
> Regards
> Ken- Hide quoted text -
>
So if warm air is more turbulent ( I think I can accept that ) wouldnt
that mean that at higher temperatures for the same density altitude
you would get less lift and require longer take off distance?
As previously stated the results are the other way around.

Cheers
Terry

[Bertie the Bunyip[_19_]]

"RST Engineering" > wrote in
:

>
> "Jim Macklin" > wrote in message
> ...
>> roflol, what kinds of experiments are/were needed to prove
>> the axiom?
>
> Don't get me started. You know how I am...
>
>
>
> Two guys walking down the sidewalk and pass a good looking brunette.
>
> "Ever sleep with a brunette?" "Yeah, I've slept with a few brunettes."
>
> They pass a beautiful blonde.
>
> "Ever sleep with a blonde?" "Yeah, I've slept with a few blondes."
>
> They pass a KNOCKOUT redhead.
>
> "Ever sleep with a redhead?" "Not a wink."



>
"Redheads buck like goats"

~Jimmy Joyce


Bertie

[Jim Logajan]

"Ken S. Tucker" > wrote:
> I'm guessing: but I get the impression that the onset
> of turbulence over wings was also dependant on temp-
> erature, even when the density altitude is the same.
> In Quantum Theory that makes sense.

Your sudden invocation of quantum theory doesn't make any sense to me. At
no point does one need to utilize the Schrodinger, Dirac, or Klein-Gordon
equations or any of their related equations in order to model or understand
the onset of turbulence.

[Bertie the Bunyip[_19_]]

Jim Logajan > wrote in
:

> "Ken S. Tucker" > wrote:
>> I'm guessing: but I get the impression that the onset
>> of turbulence over wings was also dependant on temp-
>> erature, even when the density altitude is the same.
>> In Quantum Theory that makes sense.
>
> Your sudden invocation of quantum theory doesn't make any sense to me.
> At no point does one need to utilize the Schrodinger, Dirac, or
> Klein-Gordon equations or any of their related equations in order to
> model or understand the onset of turbulence.
>


When the molecules in your coke can start sonoluminescing from the
turbulence, prolly.

Bertie

[Jim Logajan]

Bertie the Bunyip > wrote:
> Jim Logajan > wrote in
> :
>
>> "Ken S. Tucker" > wrote:
>>> I'm guessing: but I get the impression that the onset
>>> of turbulence over wings was also dependant on temp-
>>> erature, even when the density altitude is the same.
>>> In Quantum Theory that makes sense.
>>
>> Your sudden invocation of quantum theory doesn't make any sense to me.
>> At no point does one need to utilize the Schrodinger, Dirac, or
>> Klein-Gordon equations or any of their related equations in order to
>> model or understand the onset of turbulence.
>>
>
>
> When the molecules in your coke can start sonoluminescing from the
> turbulence, prolly.

Ah - I see - I think. How stupid of me. So would that result in cold fusion
or coke fusion?

[Bertie the Bunyip[_19_]]

Jim Logajan > wrote in
:

> Bertie the Bunyip > wrote:
>> Jim Logajan > wrote in
>> :
>>
>>> "Ken S. Tucker" > wrote:
>>>> I'm guessing: but I get the impression that the onset
>>>> of turbulence over wings was also dependant on temp-
>>>> erature, even when the density altitude is the same.
>>>> In Quantum Theory that makes sense.
>>>
>>> Your sudden invocation of quantum theory doesn't make any sense to
>>> me. At no point does one need to utilize the Schrodinger, Dirac, or
>>> Klein-Gordon equations or any of their related equations in order to
>>> model or understand the onset of turbulence.
>>>
>>
>>
>> When the molecules in your coke can start sonoluminescing from the
>> turbulence, prolly.
>
> Ah - I see - I think. How stupid of me. So would that result in cold
> fusion or coke fusion?
>

I think the latter may explain Ken...


Bertie

[Ken S. Tucker]

On Jan 15, 5:59 pm, terry > wrote:
> On Jan 16, 7:05 am, "Ken S. Tucker" > wrote:
>
> > Humidity feeds into "density altitude" because water
> > vapour molecule H2O has density ~ 10 compared to
> > Nitrogen N2 ~ 14 *at equal pressures*
>
> Not quite. The density is proportional to molecular weight, which
> would be in the ratio of 18 for water to 28 for nitrogen ( g /mol )
> But of course we are really interested in the density ratio between
> water and air which would be 18 to 28.9
>
> Ths simply comes from rearranging the Gas Equation we all learn in
> high school
> PV =nRT
> substiute n =m/M where m is mass and M molecular weight , you
> rearrange to get
> m/V = PM / RT
> m/V of course = density
> ( assuming ideal behaviour exists which is a pretty good assumption at
> the pressures and temperatures involved in flying light aircraft ).
>
> > I'm guessing: but I get the impression that the onset
> > of turbulence over wings was also dependant on temp-
> > erature, even when the density altitude is the same.
> > In Quantum Theory that makes sense.
> > To start, warm air is more chaotic than cold air at the
> > molecular level, and the chaos *seeds* the turbulence.
> > You know, hot fluids are less viscous than cold and so
> > less sticky. That's likely a secondary correction.
> > Regards
> > Ken- Hide quoted text -
>
> So if warm air is more turbulent ( I think I can accept that ) wouldnt
> that mean that at higher temperatures for the same density altitude
> you would get less lift and require longer take off distance?

" As previously stated the results are the other way around."
> Cheers
> Terry

I checked what you "previously stated", and the words
"correction" and "difference" didn't have the usual "+/-"
in them.
Is the Cessna handbook online, that will save time,
I'm interested.
Regards
Ken

[Ken S. Tucker]

On Jan 15, 10:05 pm, Jim Logajan > wrote:
> "Ken S. Tucker" > wrote:
>
> > I'm guessing: but I get the impression that the onset
> > of turbulence over wings was also dependant on temp-
> > erature, even when the density altitude is the same.
> > In Quantum Theory that makes sense.
>
> Your sudden invocation of quantum theory doesn't make any sense to me. At
> no point does one need to utilize the Schrodinger, Dirac, or Klein-Gordon
> equations or any of their related equations in order to model or understand
> the onset of turbulence.

Warmer atmospheric gas has a greater photon
exchange rate and that creates repulsion, that of course
is why a heated closed volume increases in pressure.
We may term that as "anti-viscosity", where viscosity
is similiar to "stickiness".

In brief, *warm things repel warm things* better than
*cold things repel colds things*, all other things being
equal.
Regards
Ken

[Ken S. Tucker]

On Jan 15, 10:27 pm, Jim Logajan > wrote:
> Bertie the Bunyip > wrote:
>
>
>
> > Jim Logajan > wrote in
> :
>
> >> "Ken S. Tucker" > wrote:
> >>> I'm guessing: but I get the impression that the onset
> >>> of turbulence over wings was also dependant on temp-
> >>> erature, even when the density altitude is the same.
> >>> In Quantum Theory that makes sense.
>
> >> Your sudden invocation of quantum theory doesn't make any sense to me.
> >> At no point does one need to utilize the Schrodinger, Dirac, or
> >> Klein-Gordon equations or any of their related equations in order to
> >> model or understand the onset of turbulence.
>
> > When the molecules in your coke can start sonoluminescing from the
> > turbulence, prolly.
>
> Ah - I see - I think. How stupid of me. So would that result in cold fusion
> or coke fusion?

Hey, be quiet, I've nearly got the wife, aka "money bags"
talked into taking flying lessons. Once that happens I
might be able to squeak some funds for our own A/C.
I needs encouragement!
Ken

[Bertie the Bunyip[_19_]]

"Ken S. Tucker" > wrote in
:

> On Jan 15, 10:27 pm, Jim Logajan > wrote:
>> Bertie the Bunyip > wrote:
>>
>>
>>
>> > Jim Logajan > wrote in
>> :
>>
>> >> "Ken S. Tucker" > wrote:
>> >>> I'm guessing: but I get the impression that the onset
>> >>> of turbulence over wings was also dependant on temp-
>> >>> erature, even when the density altitude is the same.
>> >>> In Quantum Theory that makes sense.
>>
>> >> Your sudden invocation of quantum theory doesn't make any sense to
>> >> me. At no point does one need to utilize the Schrodinger, Dirac,
>> >> or Klein-Gordon equations or any of their related equations in
>> >> order to model or understand the onset of turbulence.
>>
>> > When the molecules in your coke can start sonoluminescing from the
>> > turbulence, prolly.
>>
>> Ah - I see - I think. How stupid of me. So would that result in cold
>> fusion or coke fusion?
>
> Hey, be quiet, I've nearly got the wife, aka "money bags"
> talked into taking flying lessons. Once that happens I
> might be able to squeak some funds for our own A/C.
> I needs encouragement!

Uh, no you don't.


You need a different hobby.

How about slot car racing?


Bertie

[Jim Logajan]

"Ken S. Tucker" > wrote:
> On Jan 15, 10:05 pm, Jim Logajan > wrote:
>> "Ken S. Tucker" > wrote:
>>
>> > I'm guessing: but I get the impression that the onset
>> > of turbulence over wings was also dependant on temp-
>> > erature, even when the density altitude is the same.
>> > In Quantum Theory that makes sense.
>>
>> Your sudden invocation of quantum theory doesn't make any sense to
>> me. At no point does one need to utilize the Schrodinger, Dirac, or
>> Klein-Gordon equations or any of their related equations in order to
>> model or understand the onset of turbulence.
>
> Warmer atmospheric gas has a greater photon
> exchange rate and that creates repulsion, that of course
> is why a heated closed volume increases in pressure.

NO. The kinetic energy (and the momentum) of the gas particles increase
with temperature, which in turns leads to the increase in pressure in the
case you mention. There is no reason to involve photons to derive the
equation of state.

Besides, your followup paragraph is a non sequitur to anything that
preceded it.

> We may term that as "anti-viscosity", where viscosity
> is similiar to "stickiness".

NO. The origin of viscosity at the atomic scale is generally covered in
undergraduate statistical and thermal physics courses and I can assure
you that there is no reason to invent new terms like "anti-viscosity".
For example, the undergraduate text "Fundamentals of Statistical and
Thermal Physics" by F. Reif covers viscosity in section 12.3.

I take it you haven't studied physics in college at any advanced level
and probably don't have a degree in physics?

> In brief, *warm things repel warm things* better than
> *cold things repel colds things*, all other things being
> equal.

That is meaningless to me. Oh, and earlier you incorrectly wrote:

> To start, warm air is more chaotic than cold air at the
> molecular level, and the chaos *seeds* the turbulence.
> You know, hot fluids are less viscous than cold and so
> less sticky. That's likely a secondary correction.

Your conclusion is wrong because your premise is wrong. In general the
viscosity of a gas _increases_ as the temperature rises while in general
the viscosity of liquids _decrease_ rapidly at the temperature rises.

[terry]

On Jan 17, 4:16*am, "Ken S. Tucker" > wrote:
> On Jan 15, 5:59 pm, terry > wrote:
>
>
>
>
>
> > On Jan 16, 7:05 am, "Ken S. Tucker" > wrote:
>
> > > Humidity feeds into "density altitude" because water
> > > vapour molecule H2O has density ~ 10 compared to
> > > Nitrogen N2 ~ 14 *at equal pressures*
>
> > Not quite. *The density is *proportional to molecular weight, which
> > would be in the ratio of *18 for water to 28 for nitrogen ( g /mol )
> > But of course we are really interested in the density ratio between
> > water and air which would be 18 to 28.9
>
> > Ths simply comes from rearranging the Gas Equation we all learn in
> > high school
> > PV =nRT
> > substiute n =m/M * where m is mass and M *molecular weight , you
> > rearrange to get
> > m/V = PM / RT
> > m/V of course = density
> > ( assuming ideal behaviour exists which is a pretty good assumption at
> > the pressures and temperatures involved in flying light aircraft ).
>
> > > I'm guessing: but I get the impression that the onset
> > > of turbulence over wings was also dependant on temp-
> > > erature, even when the density altitude is the same.
> > > * In Quantum Theory that makes sense.
> > > To start, warm air is more chaotic than cold air at the
> > > molecular level, and the chaos *seeds* the turbulence.
> > > You know, hot fluids are less viscous than cold and so
> > > less sticky. That's likely a secondary correction.
> > > Regards
> > > Ken- Hide quoted text -
>
> > So if warm air is more turbulent ( I think I can accept that ) wouldnt
> > that mean that at higher temperatures for the same density altitude
> > you would get less lift and require longer take off distance?
>
> " As previously stated the results are the other way around."
>
> > Cheers
> > Terry
>
> I checked what you "previously stated", and the words
> "correction" and "difference" didn't have the usual "+/-"
> in them.
> Is the Cessna handbook online, that will save time,
> I'm interested.

I coulnt find it on line, but I would be happy to scan and email the
page, or even email you the Excel spreadsheet with the data and my
calculations. Then you can do all the quantum mechanics, vector
analysis, euclid geometry and reverse differentiation your heart
desires, and report back to us. Just let me know if you want to
recieve this info by email.
terry

[Ken S. Tucker]

On Jan 16, 11:41 am, Jim Logajan > wrote:
> "Ken S. Tucker" > wrote:
>
>
>
> > On Jan 15, 10:05 pm, Jim Logajan > wrote:
> >> "Ken S. Tucker" > wrote:
>
> >> > I'm guessing: but I get the impression that the onset
> >> > of turbulence over wings was also dependant on temp-
> >> > erature, even when the density altitude is the same.
> >> > In Quantum Theory that makes sense.
>
> >> Your sudden invocation of quantum theory doesn't make any sense to
> >> me. At no point does one need to utilize the Schrodinger, Dirac, or
> >> Klein-Gordon equations or any of their related equations in order to
> >> model or understand the onset of turbulence.
>
> > Warmer atmospheric gas has a greater photon
> > exchange rate and that creates repulsion, that of course
> > is why a heated closed volume increases in pressure.
>
> NO. The kinetic energy (and the momentum) of the gas particles increase
> with temperature, which in turns leads to the increase in pressure in the
> case you mention. There is no reason to involve photons to derive the
> equation of state.

Mr. Potato Head, the OP, is using a constant
"density pressure". Read the ****in spec's, before
blabbing.

> Besides, your followup paragraph is a non sequitur to anything that
> preceded it.
>
> > We may term that as "anti-viscosity", where viscosity
> > is similiar to "stickiness".
>
> NO. The origin of viscosity at the atomic scale is generally covered in
> undergraduate statistical and thermal physics courses and I can assure
> you that there is no reason to invent new terms like "anti-viscosity".
> For example, the undergraduate text "Fundamentals of Statistical and
> Thermal Physics" by F. Reif covers viscosity in section 12.3.
> I take it you haven't studied physics in college at any advanced level
> and probably don't have a degree in physics?

Mr. Potato head, see Ackowlegements here...
http://arxiv.org/ftp/gr-qc/papers/0511/0511050.pdf

Whatever simplistic notions occupy your cranium
are relatively delusional. What I do is to place physics
in a common sense fashion, in explanation to this
group. and then ref to the hard science.

I do acknowledge that the explanation of heating
and the term "anti-viscsoity" is excellent.

> > In brief, *warm things repel warm things* better than
> > *cold things repel colds things*, all other things being
> > equal.
>
> That is meaningless to me. Oh, and earlier you incorrectly wrote:
>
> > To start, warm air is more chaotic than cold air at the
> > molecular level, and the chaos *seeds* the turbulence.
> > You know, hot fluids are less viscous than cold and so
> > less sticky. That's likely a secondary correction.
>
> Your conclusion is wrong because your premise is wrong. In general the
> viscosity of a gas _increases_ as the temperature rises while in general
> the viscosity of liquids _decrease_ rapidly at the temperature rises.

Well, then provide a scientific example.
With all due respect.
Ken S. Tucker

[Ken S. Tucker]

On Jan 16, 12:22 pm, terry > wrote:
> On Jan 17, 4:16 am, "Ken S. Tucker" > wrote:
>
>
>
> > On Jan 15, 5:59 pm, terry > wrote:
>
> > > On Jan 16, 7:05 am, "Ken S. Tucker" > wrote:
>
> > > > Humidity feeds into "density altitude" because water
> > > > vapour molecule H2O has density ~ 10 compared to
> > > > Nitrogen N2 ~ 14 *at equal pressures*
>
> > > Not quite. The density is proportional to molecular weight, which
> > > would be in the ratio of 18 for water to 28 for nitrogen ( g /mol )
> > > But of course we are really interested in the density ratio between
> > > water and air which would be 18 to 28.9
>
> > > Ths simply comes from rearranging the Gas Equation we all learn in
> > > high school
> > > PV =nRT
> > > substiute n =m/M where m is mass and M molecular weight , you
> > > rearrange to get
> > > m/V = PM / RT
> > > m/V of course = density
> > > ( assuming ideal behaviour exists which is a pretty good assumption at
> > > the pressures and temperatures involved in flying light aircraft ).
>
> > > > I'm guessing: but I get the impression that the onset
> > > > of turbulence over wings was also dependant on temp-
> > > > erature, even when the density altitude is the same.
> > > > In Quantum Theory that makes sense.
> > > > To start, warm air is more chaotic than cold air at the
> > > > molecular level, and the chaos *seeds* the turbulence.
> > > > You know, hot fluids are less viscous than cold and so
> > > > less sticky. That's likely a secondary correction.
> > > > Regards
> > > > Ken- Hide quoted text -
>
> > > So if warm air is more turbulent ( I think I can accept that ) wouldnt
> > > that mean that at higher temperatures for the same density altitude
> > > you would get less lift and require longer take off distance?
>
> > " As previously stated the results are the other way around."
>
> > > Cheers
> > > Terry
>
> > I checked what you "previously stated", and the words
> > "correction" and "difference" didn't have the usual "+/-"
> > in them.
> > Is the Cessna handbook online, that will save time,
> > I'm interested.
>
> I coulnt find it on line, but I would be happy to scan and email the
> page, or even email you the Excel spreadsheet with the data and my
> calculations. Then you can do all the quantum mechanics, vector
> analysis, euclid geometry and reverse differentiation your heart
> desires, and report back to us. Just let me know if you want to
> recieve this info by email.
> terry

Let's see the posted info for all to see and then we all
may examine the data equally, otherwise, shut the ****
up. Don't waste our time.
Regards
Ken

[Jim Logajan]

"Ken S. Tucker" > wrote:
> On Jan 16, 11:41 am, Jim Logajan > wrote:
>> "Ken S. Tucker" > wrote:
>>
>>
>>
>> > On Jan 15, 10:05 pm, Jim Logajan > wrote:
>> >> "Ken S. Tucker" > wrote:
>>
>> >> > I'm guessing: but I get the impression that the onset
>> >> > of turbulence over wings was also dependant on temp-
>> >> > erature, even when the density altitude is the same.
>> >> > In Quantum Theory that makes sense.
>>
>> >> Your sudden invocation of quantum theory doesn't make any sense to
>> >> me. At no point does one need to utilize the Schrodinger, Dirac,
>> >> or Klein-Gordon equations or any of their related equations in
>> >> order to model or understand the onset of turbulence.
>>
>> > Warmer atmospheric gas has a greater photon
>> > exchange rate and that creates repulsion, that of course
>> > is why a heated closed volume increases in pressure.
>>
>> NO. The kinetic energy (and the momentum) of the gas particles
>> increase with temperature, which in turns leads to the increase in
>> pressure in the case you mention. There is no reason to involve
>> photons to derive the equation of state.
>
> Mr. Potato Head, the OP, is using a constant
> "density pressure". Read the ****in spec's, before
> blabbing.

I'm addressing your posts, not his, because not only do your posts do
nothing to answer the OP's question, you continue to bring in aspects
that are either irrelevant or incorrect or both. References to
turbulence, quantum mechanics, and "photon exchange rates" seem about as
relevant as cosmology, string theory, or general relativity.

>
>> Besides, your followup paragraph is a non sequitur to anything that
>> preceded it.
>>
>> > We may term that as "anti-viscosity", where viscosity
>> > is similiar to "stickiness".
>>
>> NO. The origin of viscosity at the atomic scale is generally covered
>> in undergraduate statistical and thermal physics courses and I can
>> assure you that there is no reason to invent new terms like
>> "anti-viscosity". For example, the undergraduate text "Fundamentals
>> of Statistical and Thermal Physics" by F. Reif covers viscosity in
>> section 12.3. I take it you haven't studied physics in college at any
>> advanced level and probably don't have a degree in physics?
>
> Mr. Potato head, see Ackowlegements here...
> http://arxiv.org/ftp/gr-qc/papers/0511/0511050.pdf

One acknowledgement by an author who is not degreed in physics and who
doesn't appear to have any papers in peer-reviewed journals hardly
excuses your attempt to invent and spread your own brand of physics.
Anyway, I've got more acknowledgements than you - check the ack sections
of the following:

http://www.nanomedicine.com/NMI/PrefaceAcknowledgments.htm
http://jetpress.org/volume11/vasculoid.html
http://jetpress.org/volume13/Nanofactory.htm
http://www.kurzweilai.net/meme/frame.html?main=/articles/art0142.html

One unintended contribution here:
http://www.nanomedicine.com/NMI/7.4.6.5.htm

> Whatever simplistic notions occupy your cranium
> are relatively delusional. What I do is to place physics
> in a common sense fashion, in explanation to this
> group. and then ref to the hard science.

It looks to me like you leaped on past the standard "billiard ball"
model of gas physics so you could drop in mention of quantum physics to
demonstrate how well read you are. So if it makes you feel better to
throw insults at me, well, who am I to stand in your way?

> I do acknowledge that the explanation of heating
> and the term "anti-viscsoity" is excellent.

If you say so.

>> > In brief, *warm things repel warm things* better than
>> > *cold things repel colds things*, all other things being
>> > equal.
>>
>> That is meaningless to me. Oh, and earlier you incorrectly wrote:
>>
>> > To start, warm air is more chaotic than cold air at the
>> > molecular level, and the chaos *seeds* the turbulence.
>> > You know, hot fluids are less viscous than cold and so
>> > less sticky. That's likely a secondary correction.
>>
>> Your conclusion is wrong because your premise is wrong. In general
>> the viscosity of a gas _increases_ as the temperature rises while in
>> general the viscosity of liquids _decrease_ rapidly at the
>> temperature rises.
>
> Well, then provide a scientific example.
> With all due respect.

Sure. Air and water. Here's a table that shows dynamic viscosity of
water as both a gas and a liquid as a function of temperature and
pressure:

http://www.engineeringtoolbox.com/steam-viscosity-d_770.html

Note how the viscosity of liquid water decreases with increasing
temperature and viscosity of gaseous water increases with increasing
termperature.

Here's a table showing dynamic and kinematic viscosity of liquid water:

http://www.engineeringtoolbox.com/water-dynamic-kinematic-viscosity-d_596.html

Here's a table showing dynamic and kinematic viscosity of air:

http://www.engineeringtoolbox.com/air-absolute-kinematic-viscosity-d_601.html

Unfortunately my brief search didn't turn up viscosity of liquid O2 or
N2, but the above examples are sufficient for my purpose.

Lastly, there is the reference to the section of Reif's book which I
already mentioned that shows the theory behind the experimental
observations referenced above. You could also take a look at:

http://en.wikipedia.org/wiki/Viscosity

Which ironically you also quoted elsewhere but it seems didn't read.

[FledgeIII]

On Jan 16, 4:18 pm, "Ken S. Tucker" > wrote:
> On Jan 16, 12:22 pm, terry > wrote:
>
>
>
> > On Jan 17, 4:16 am, "Ken S. Tucker" > wrote:
>
> > > On Jan 15, 5:59 pm, terry > wrote:
>
> > > > On Jan 16, 7:05 am, "Ken S. Tucker" > wrote:
>
> > > > > Humidity feeds into "density altitude" because water
> > > > > vapour molecule H2O has density ~ 10 compared to
> > > > > Nitrogen N2 ~ 14 *at equal pressures*
>
> > > > Not quite. The density is proportional to molecular weight, which
> > > > would be in the ratio of 18 for water to 28 for nitrogen ( g /mol )
> > > > But of course we are really interested in the density ratio between
> > > > water and air which would be 18 to 28.9
>
> > > > Ths simply comes from rearranging the Gas Equation we all learn in
> > > > high school
> > > > PV =nRT
> > > > substiute n =m/M where m is mass and M molecular weight , you
> > > > rearrange to get
> > > > m/V = PM / RT
> > > > m/V of course = density
> > > > ( assuming ideal behaviour exists which is a pretty good assumption at
> > > > the pressures and temperatures involved in flying light aircraft ).
>
> > > > > I'm guessing: but I get the impression that the onset
> > > > > of turbulence over wings was also dependant on temp-
> > > > > erature, even when the density altitude is the same.
> > > > > In Quantum Theory that makes sense.
> > > > > To start, warm air is more chaotic than cold air at the
> > > > > molecular level, and the chaos *seeds* the turbulence.
> > > > > You know, hot fluids are less viscous than cold and so
> > > > > less sticky. That's likely a secondary correction.
> > > > > Regards
> > > > > Ken- Hide quoted text -
>
> > > > So if warm air is more turbulent ( I think I can accept that ) wouldnt
> > > > that mean that at higher temperatures for the same density altitude
> > > > you would get less lift and require longer take off distance?
>
> > > " As previously stated the results are the other way around."
>
> > > > Cheers
> > > > Terry
>
> > > I checked what you "previously stated", and the words
> > > "correction" and "difference" didn't have the usual "+/-"
> > > in them.
> > > Is the Cessna handbook online, that will save time,
> > > I'm interested.
>
> > I coulnt find it on line, but I would be happy to scan and email the
> > page, or even email you the Excel spreadsheet with the data and my
> > calculations. Then you can do all the quantum mechanics, vector
> > analysis, euclid geometry and reverse differentiation your heart
> > desires, and report back to us. Just let me know if you want to
> > recieve this info by email.
> > terry
>
> Let's see the posted info for all to see and then we all
> may examine the data equally, otherwise, shut the ****
> up. Don't waste our time.
> Regards
> Ken
You talk like that in front of your "moneybags"?

That's the *only* form of "our" around here that could remotely apply.

Otherwise, people seem to be doing a pretty nice - and polite - job of
illustrating that your knowledge of physics is every bit as deficient
as your knowledge of flying.

Ask "moneybags" for a loan. Go buy a clue.

[terry]

On Jan 17, 8:18*am, "Ken S. Tucker" > wrote:
> On Jan 16, 12:22 pm, terry > wrote:
>
>
>
>
>
> > On Jan 17, 4:16 am, "Ken S. Tucker" > wrote:
>
> > > On Jan 15, 5:59 pm, terry > wrote:
>
> > > > On Jan 16, 7:05 am, "Ken S. Tucker" > wrote:
>
> > > > > Humidity feeds into "density altitude" because water
> > > > > vapour molecule H2O has density ~ 10 compared to
> > > > > Nitrogen N2 ~ 14 *at equal pressures*
>
> > > > Not quite. *The density is *proportional to molecular weight, which
> > > > would be in the ratio of *18 for water to 28 for nitrogen ( g /mol )
> > > > But of course we are really interested in the density ratio between
> > > > water and air which would be 18 to 28.9
>
> > > > Ths simply comes from rearranging the Gas Equation we all learn in
> > > > high school
> > > > PV =nRT
> > > > substiute n =m/M * where m is mass and M *molecular weight , you
> > > > rearrange to get
> > > > m/V = PM / RT
> > > > m/V of course = density
> > > > ( assuming ideal behaviour exists which is a pretty good assumption at
> > > > the pressures and temperatures involved in flying light aircraft ).
>
> > > > > I'm guessing: but I get the impression that the onset
> > > > > of turbulence over wings was also dependant on temp-
> > > > > erature, even when the density altitude is the same.
> > > > > * In Quantum Theory that makes sense.
> > > > > To start, warm air is more chaotic than cold air at the
> > > > > molecular level, and the chaos *seeds* the turbulence.
> > > > > You know, hot fluids are less viscous than cold and so
> > > > > less sticky. That's likely a secondary correction.
> > > > > Regards
> > > > > Ken- Hide quoted text -
>
> > > > So if warm air is more turbulent ( I think I can accept that ) wouldnt
> > > > that mean that at higher temperatures for the same density altitude
> > > > you would get less lift and require longer take off distance?
>
> > > " As previously stated the results are the other way around."
>
> > > > Cheers
> > > > Terry
>
> > > I checked what you "previously stated", and the words
> > > "correction" and "difference" didn't have the usual "+/-"
> > > in them.
> > > Is the Cessna handbook online, that will save time,
> > > I'm interested.
>
> > I coulnt find it on line, but I would be happy to scan and email the
> > page, or even email you the Excel spreadsheet with the data and my
> > calculations. *Then you can do all the quantum mechanics, vector
> > analysis, euclid geometry and *reverse differentiation your heart
> > desires, and report back to us. *Just let me know if you want to
> > recieve this info by email.
> > terry
>
> Let's see the posted info for all to see and then we all
> may examine the data equally, otherwise, shut the ****
> up. Don't waste our time.
> Regards

Now no need to be rude Ken, its your choice how you spend your time,
its not me that is wasting it. I posted a question which I thought
would be of interest to pilots of real aircraft for whom understanding
(or lack thereof) of takeoff performance data can literally be the
difference between living and dying. I didnt post the data set
because it is large and it was not my intention to have others spend
hours analysing it. ( although anyone is welcome to it , and my full
analysis of it, but offf line) I found something that didnt gel with
my understanding, and sort reasons for the potential discrepancy. As
for some of your suggestions Ken, all I can say mate is that you need
to come out of the clouds a little, most things in life are not as
complicated as you seem to think. I am sure you could come up with a
thousand brilliant ideas, that even your Mensa friends would be
impressed by, as to the possible reasons why a car might go put put
splutter , splutter and then stop.. but just checking the gas first
makes a lot more sense. I like physics and maths too and whilst I do
have a PhD in science ( physical chemistry) I am certainly no genius.
I have spent many many hours mathematically analysing a lot what is
involved in flying, from navigation problems, density altitudes with
corrections for humidty, wt and balance, radius of a turn with
correction for crosswind ( thanks Cain Liddle) , I even wrote a
program for an air traffic controller who wanted to be able to predict
the wind speed and direction from radar tracks and flight plan
information for multiple aircraft..... But you know what, none of
this stuff has ever required anything I didnt learn in high school,
like a good grasp of trigonometry, solve a quadratic here and there,
Newtons Laws, the gas equations etc. For christ sake leave the
quantum mechanics and anti viscosity discussions to your Mensa
meetings.
Terry

[Ken S. Tucker]

On Jan 16, 3:10 pm, Jim Logajan > wrote:
> "Ken S. Tucker" > wrote:
>
>
>
> > On Jan 16, 11:41 am, Jim Logajan > wrote:
> >> "Ken S. Tucker" > wrote:
>
> >> > On Jan 15, 10:05 pm, Jim Logajan > wrote:
> >> >> "Ken S. Tucker" > wrote:
>
> >> >> > I'm guessing: but I get the impression that the onset
> >> >> > of turbulence over wings was also dependant on temp-
> >> >> > erature, even when the density altitude is the same.
> >> >> > In Quantum Theory that makes sense.
>
> >> >> Your sudden invocation of quantum theory doesn't make any sense to
> >> >> me. At no point does one need to utilize the Schrodinger, Dirac,
> >> >> or Klein-Gordon equations or any of their related equations in
> >> >> order to model or understand the onset of turbulence.
>
> >> > Warmer atmospheric gas has a greater photon
> >> > exchange rate and that creates repulsion, that of course
> >> > is why a heated closed volume increases in pressure.
>
> >> NO. The kinetic energy (and the momentum) of the gas particles
> >> increase with temperature, which in turns leads to the increase in
> >> pressure in the case you mention. There is no reason to involve
> >> photons to derive the equation of state.
>
> > Mr. Potato Head, the OP, is using a constant
> > "density pressure". Read the ****in spec's, before
> > blabbing.
>
> I'm addressing your posts, not his, because not only do your posts do
> nothing to answer the OP's question, you continue to bring in aspects
> that are either irrelevant or incorrect or both. References to
> turbulence, quantum mechanics, and "photon exchange rates" seem about as
> relevant as cosmology, string theory, or general relativity.
>
>
>
>
>
> >> Besides, your followup paragraph is a non sequitur to anything that
> >> preceded it.
>
> >> > We may term that as "anti-viscosity", where viscosity
> >> > is similiar to "stickiness".
>
> >> NO. The origin of viscosity at the atomic scale is generally covered
> >> in undergraduate statistical and thermal physics courses and I can
> >> assure you that there is no reason to invent new terms like
> >> "anti-viscosity". For example, the undergraduate text "Fundamentals
> >> of Statistical and Thermal Physics" by F. Reif covers viscosity in
> >> section 12.3. I take it you haven't studied physics in college at any
> >> advanced level and probably don't have a degree in physics?
>
> > Mr. Potato head, see Ackowlegements here...
> >http://arxiv.org/ftp/gr-qc/papers/0511/0511050.pdf
>
> One acknowledgement by an author who is not degreed in physics and who
> doesn't appear to have any papers in peer-reviewed journals hardly
> excuses your attempt to invent and spread your own brand of physics.
> Anyway, I've got more acknowledgements than you - check the ack sections
> of the following:
>
> http://www.nanomedicine.com/NMI/PrefaceAcknowledgments.htmhttp://jetpress.org/volume11/vasculoid.htmlhttp://jetpress.org/volume13/Nanofactory.htmhttp://www.kurzweilai.net/meme/frame.html?main=/articles/art0142.html
>
> One unintended contribution here:http://www.nanomedicine.com/NMI/7.4.6.5.htm
>
> > Whatever simplistic notions occupy your cranium
> > are relatively delusional. What I do is to place physics
> > in a common sense fashion, in explanation to this
> > group. and then ref to the hard science.
>
> It looks to me like you leaped on past the standard "billiard ball"
> model of gas physics so you could drop in mention of quantum physics to
> demonstrate how well read you are. So if it makes you feel better to
> throw insults at me, well, who am I to stand in your way?
>
> > I do acknowledge that the explanation of heating
> > and the term "anti-viscsoity" is excellent.
>
> If you say so.
>
>
>
> >> > In brief, *warm things repel warm things* better than
> >> > *cold things repel colds things*, all other things being
> >> > equal.
>
> >> That is meaningless to me. Oh, and earlier you incorrectly wrote:
>
> >> > To start, warm air is more chaotic than cold air at the
> >> > molecular level, and the chaos *seeds* the turbulence.
> >> > You know, hot fluids are less viscous than cold and so
> >> > less sticky. That's likely a secondary correction.
>
> >> Your conclusion is wrong because your premise is wrong. In general
> >> the viscosity of a gas _increases_ as the temperature rises while in
> >> general the viscosity of liquids _decrease_ rapidly at the
> >> temperature rises.
>
> > Well, then provide a scientific example.
> > With all due respect.
>
> Sure. Air and water. Here's a table that shows dynamic viscosity of
> water as both a gas and a liquid as a function of temperature and
> pressure:
>
> http://www.engineeringtoolbox.com/steam-viscosity-d_770.html
>
> Note how the viscosity of liquid water decreases with increasing
> temperature and viscosity of gaseous water increases with increasing
> termperature.
>
> Here's a table showing dynamic and kinematic viscosity of liquid water:
>
> http://www.engineeringtoolbox.com/water-dynamic-kinematic-viscosity-d...
>
> Here's a table showing dynamic and kinematic viscosity of air:
>
> http://www.engineeringtoolbox.com/air-absolute-kinematic-viscosity-d_...

Ok, I bookmarked that.

> Unfortunately my brief search didn't turn up viscosity of liquid O2 or
> N2, but the above examples are sufficient for my purpose.
> Lastly, there is the reference to the section of Reif's book which I
> already mentioned that shows the theory behind the experimental
> observations referenced above. You could also take a look at:
>
> http://en.wikipedia.org/wiki/Viscosity
>
> Which ironically you also quoted elsewhere but it seems didn't read.

Given a constant "density atlitude", how is Take-off distance
a function of temperature. We have Lift, Skin friction, Boundary
layer and Viscosity as gas characteristics that depend upon
temperature.
Regards
Ken

[FledgeIII]

On Jan 17, 1:08 pm, Bertie the Bunyip > wrote:
> "Ken S. Tucker" > wrote :
>
>
>
> > On Jan 16, 3:10 pm, Jim Logajan > wrote:
> >> "Ken S. Tucker" > wrote:
>
> >> > On Jan 16, 11:41 am, Jim Logajan > wrote:
> >> >> "Ken S. Tucker" > wrote:
>
> >> >> > On Jan 15, 10:05 pm, Jim Logajan > wrote:
> >> >> >> "Ken S. Tucker" > wrote:
>
> >> >> >> > I'm guessing: but I get the impression that the onset
> >> >> >> > of turbulence over wings was also dependant on temp-
> >> >> >> > erature, even when the density altitude is the same.
> >> >> >> > In Quantum Theory that makes sense.
>
> >> >> >> Your sudden invocation of quantum theory doesn't make any sense
> >> >> >> to me. At no point does one need to utilize the Schrodinger,
> >> >> >> Dirac, or Klein-Gordon equations or any of their related
> >> >> >> equations in order to model or understand the onset of
> >> >> >> turbulence.
>
> >> >> > Warmer atmospheric gas has a greater photon
> >> >> > exchange rate and that creates repulsion, that of course
> >> >> > is why a heated closed volume increases in pressure.
>
> >> >> NO. The kinetic energy (and the momentum) of the gas particles
> >> >> increase with temperature, which in turns leads to the increase in
> >> >> pressure in the case you mention. There is no reason to involve
> >> >> photons to derive the equation of state.
>
> >> > Mr. Potato Head, the OP, is using a constant
> >> > "density pressure". Read the ****in spec's, before
> >> > blabbing.
>
> >> I'm addressing your posts, not his, because not only do your posts do
> >> nothing to answer the OP's question, you continue to bring in aspects
> >> that are either irrelevant or incorrect or both. References to
> >> turbulence, quantum mechanics, and "photon exchange rates" seem about
> >> as relevant as cosmology, string theory, or general relativity.
>
> >> >> Besides, your followup paragraph is a non sequitur to anything
> >> >> that preceded it.
>
> >> >> > We may term that as "anti-viscosity", where viscosity
> >> >> > is similiar to "stickiness".
>
> >> >> NO. The origin of viscosity at the atomic scale is generally
> >> >> covered in undergraduate statistical and thermal physics courses
> >> >> and I can assure you that there is no reason to invent new terms
> >> >> like "anti-viscosity". For example, the undergraduate text
> >> >> "Fundamentals of Statistical and Thermal Physics" by F. Reif
> >> >> covers viscosity in section 12.3. I take it you haven't studied
> >> >> physics in college at any advanced level and probably don't have a
> >> >> degree in physics?
>
> >> > Mr. Potato head, see Ackowlegements here...
> >> >http://arxiv.org/ftp/gr-qc/papers/0511/0511050.pdf
>
> >> One acknowledgement by an author who is not degreed in physics and
> >> who doesn't appear to have any papers in peer-reviewed journals
> >> hardly excuses your attempt to invent and spread your own brand of
> >> physics. Anyway, I've got more acknowledgements than you - check the
> >> ack sections of the following:
>
> http://www.nanomedicine.com/NMI/PrefaceAcknowledgments.htmhttp://jetpr
>
> ess.org/volume11/vasculoid.htmlhttp://jetpress.org/volume13/Nanofactor>> y.htmhttp://www.kurzweilai.net/meme/frame.html?
>
> main=/articles/art0142.
>
>
>
> >> html
>
> >> One unintended contribution
> >> here:http://www.nanomedicine.com/NMI/7.4.6.5.htm
>
> >> > Whatever simplistic notions occupy your cranium
> >> > are relatively delusional. What I do is to place physics
> >> > in a common sense fashion, in explanation to this
> >> > group. and then ref to the hard science.
>
> >> It looks to me like you leaped on past the standard "billiard ball"
> >> model of gas physics so you could drop in mention of quantum physics
> >> to demonstrate how well read you are. So if it makes you feel better
> >> to throw insults at me, well, who am I to stand in your way?
>
> >> > I do acknowledge that the explanation of heating
> >> > and the term "anti-viscsoity" is excellent.
>
> >> If you say so.
>
> >> >> > In brief, *warm things repel warm things* better than
> >> >> > *cold things repel colds things*, all other things being
> >> >> > equal.
>
> >> >> That is meaningless to me. Oh, and earlier you incorrectly wrote:
>
> >> >> > To start, warm air is more chaotic than cold air at the
> >> >> > molecular level, and the chaos *seeds* the turbulence.
> >> >> > You know, hot fluids are less viscous than cold and so
> >> >> > less sticky. That's likely a secondary correction.
>
> >> >> Your conclusion is wrong because your premise is wrong. In general
> >> >> the viscosity of a gas _increases_ as the temperature rises while
> >> >> in general the viscosity of liquids _decrease_ rapidly at the
> >> >> temperature rises.
>
> >> > Well, then provide a scientific example.
> >> > With all due respect.
>
> >> Sure. Air and water. Here's a table that shows dynamic viscosity of
> >> water as both a gas and a liquid as a function of temperature and
> >> pressure:
>
> >>http://www.engineeringtoolbox.com/steam-viscosity-d_770.html
>
> >> Note how the viscosity of liquid water decreases with increasing
> >> temperature and viscosity of gaseous water increases with increasing
> >> termperature.
>
> >> Here's a table showing dynamic and kinematic viscosity of liquid
> >> water:
>
> >>http://www.engineeringtoolbox.com/water-dynamic-kinematic-viscosity-
> d.
> >> ..
>
> >> Here's a table showing dynamic and kinematic viscosity of air:
>
> >>http://www.engineeringtoolbox.com/air-absolute-kinematic-viscosity-
> d_.
> >> ..
>
> > Ok, I bookmarked that.
>
> >> Unfortunately my brief search didn't turn up viscosity of liquid O2
> >> or N2, but the above examples are sufficient for my purpose.
> >> Lastly, there is the reference to the section of Reif's book which I
> >> already mentioned that shows the theory behind the experimental
> >> observations referenced above. You could also take a look at:
>
> >>http://en.wikipedia.org/wiki/Viscosity
>
> >> Which ironically you also quoted elsewhere but it seems didn't read.
>
> > Given a constant "density atlitude", how is Take-off distance
> > a function of temperature. We have Lift, Skin friction, Boundary
> > layer and Viscosity as gas characteristics that depend upon
> > temperature.
>
> Wow Ken,
>
> Waht's all that mean, now?
>
> Bertie

Beyond evidence he's tugging on the schnapps again, it means nothing.

[Ken S. Tucker]

On Jan 16, 9:55 pm, terry > wrote:
> On Jan 17, 8:18 am, "Ken S. Tucker" > wrote:
>
>
>
> > On Jan 16, 12:22 pm, terry > wrote:
>
> > > On Jan 17, 4:16 am, "Ken S. Tucker" > wrote:
>
> > > > On Jan 15, 5:59 pm, terry > wrote:
>
> > > > > On Jan 16, 7:05 am, "Ken S. Tucker" > wrote:
>
> > > > > > Humidity feeds into "density altitude" because water
> > > > > > vapour molecule H2O has density ~ 10 compared to
> > > > > > Nitrogen N2 ~ 14 *at equal pressures*
>
> > > > > Not quite. The density is proportional to molecular weight, which
> > > > > would be in the ratio of 18 for water to 28 for nitrogen ( g /mol )
> > > > > But of course we are really interested in the density ratio between
> > > > > water and air which would be 18 to 28.9
>
> > > > > Ths simply comes from rearranging the Gas Equation we all learn in
> > > > > high school
> > > > > PV =nRT
> > > > > substiute n =m/M where m is mass and M molecular weight , you
> > > > > rearrange to get
> > > > > m/V = PM / RT
> > > > > m/V of course = density
> > > > > ( assuming ideal behaviour exists which is a pretty good assumption at
> > > > > the pressures and temperatures involved in flying light aircraft ).
>
> > > > > > I'm guessing: but I get the impression that the onset
> > > > > > of turbulence over wings was also dependant on temp-
> > > > > > erature, even when the density altitude is the same.
> > > > > > In Quantum Theory that makes sense.
> > > > > > To start, warm air is more chaotic than cold air at the
> > > > > > molecular level, and the chaos *seeds* the turbulence.
> > > > > > You know, hot fluids are less viscous than cold and so
> > > > > > less sticky. That's likely a secondary correction.
> > > > > > Regards
> > > > > > Ken- Hide quoted text -
>
> > > > > So if warm air is more turbulent ( I think I can accept that ) wouldnt
> > > > > that mean that at higher temperatures for the same density altitude
> > > > > you would get less lift and require longer take off distance?
>
> > > > " As previously stated the results are the other way around."
>
> > > > > Cheers
> > > > > Terry
>
> > > > I checked what you "previously stated", and the words
> > > > "correction" and "difference" didn't have the usual "+/-"
> > > > in them.
> > > > Is the Cessna handbook online, that will save time,
> > > > I'm interested.
>
> > > I coulnt find it on line, but I would be happy to scan and email the
> > > page, or even email you the Excel spreadsheet with the data and my
> > > calculations. Then you can do all the quantum mechanics, vector
> > > analysis, euclid geometry and reverse differentiation your heart
> > > desires, and report back to us. Just let me know if you want to
> > > recieve this info by email.
> > > terry
>
> > Let's see the posted info for all to see and then we all
> > may examine the data equally, otherwise, shut the ****
> > up. Don't waste our time.
> > Regards
>
> Now no need to be rude Ken, its your choice how you spend your time,
> its not me that is wasting it. I posted a question which I thought
> would be of interest to pilots of real aircraft for whom understanding
> (or lack thereof) of takeoff performance data can literally be the
> difference between living and dying. I didnt post the data set
> because it is large and it was not my intention to have others spend
> hours analysing it. ( although anyone is welcome to it , and my full
> analysis of it, but offf line) I found something that didnt gel with
> my understanding, and sort reasons for the potential discrepancy. As
> for some of your suggestions Ken, all I can say mate is that you need
> to come out of the clouds a little, most things in life are not as
> complicated as you seem to think. I am sure you could come up with a
> thousand brilliant ideas, that even your Mensa friends would be
> impressed by, as to the possible reasons why a car might go put put
> splutter , splutter and then stop.. but just checking the gas first
> makes a lot more sense. I like physics and maths too and whilst I do
> have a PhD in science ( physical chemistry) I am certainly no genius.
> I have spent many many hours mathematically analysing a lot what is
> involved in flying, from navigation problems, density altitudes with
> corrections for humidty, wt and balance, radius of a turn with
> correction for crosswind ( thanks Cain Liddle) , I even wrote a
> program for an air traffic controller who wanted to be able to predict
> the wind speed and direction from radar tracks and flight plan
> information for multiple aircraft..... But you know what, none of
> this stuff has ever required anything I didnt learn in high school,
> like a good grasp of trigonometry, solve a quadratic here and there,
> Newtons Laws, the gas equations etc. For christ sake leave the
> quantum mechanics and anti viscosity discussions to your Mensa
> meetings.
> Terry

Well heck, I didn't get a High School Diploma!
What *****es me off* is the take-off roll for the
C-152 is ~ 735', so although your using a C-172,
the variation of 300' between 0C and 40C at constant
density altitude is rather high.
Regards
Ken

[terry]

On Jan 15, 10:24*am, quietguy > wrote:
> Your PA-to-DA calculations clearly differ from Cessna's, probably
> because they used a different standard atmosphere. *There are plenty
> to choose from: International SA, U.S. SA, ICAO SA (all revised over
> the years) and some others, some of which are no longer used. *You'd
> need to find out which SA was used by Cessna when the 172N was built.
> Good luck with that project. *I would just plot some points from the
> POH and draw a smooth curve connecting them; I'd be conservative in my
> choices of data points and call that good enough.

Some very sensible suggestions quietguy, I know I could just be
conservative and plot a curve through the higher set of data on the
graph, but
the curiosity in me just wants to find the reasons. I think you are
probably right about the standard atmospehere and i have had no luck
yet finding out exactly what Cessna used, but I can tell you after
some manipulation of the data by just changing the correction factor
for pressure to density altitude of 120 feet to 80 feet per 1 degree
off isa standard atmosphere temp, the points revert to the single
smooth line of takeoff distance vs density altitude that I was
expecting.
Does that ring any bells with anyone re some other version of a
standard atmosphere?
Terry

[terry]

On Jan 18, 6:10*am, "Ken S. Tucker" > wrote:
> On Jan 16, 9:55 pm, terry > wrote:
>
>
>
>
>
> > On Jan 17, 8:18 am, "Ken S. Tucker" > wrote:
>
> > > On Jan 16, 12:22 pm, terry > wrote:
>
> > > > On Jan 17, 4:16 am, "Ken S. Tucker" > wrote:
>
> > > > > On Jan 15, 5:59 pm, terry > wrote:
>
> > > > > > On Jan 16, 7:05 am, "Ken S. Tucker" > wrote:
>
> > > > > > > Humidity feeds into "density altitude" because water
> > > > > > > vapour molecule H2O has density ~ 10 compared to
> > > > > > > Nitrogen N2 ~ 14 *at equal pressures*
>
> > > > > > Not quite. *The density is *proportional to molecular weight, which
> > > > > > would be in the ratio of *18 for water to 28 for nitrogen ( g /mol )
> > > > > > But of course we are really interested in the density ratio between
> > > > > > water and air which would be 18 to 28.9
>
> > > > > > Ths simply comes from rearranging the Gas Equation we all learn in
> > > > > > high school
> > > > > > PV =nRT
> > > > > > substiute n =m/M * where m is mass and M *molecular weight , you
> > > > > > rearrange to get
> > > > > > m/V = PM / RT
> > > > > > m/V of course = density
> > > > > > ( assuming ideal behaviour exists which is a pretty good assumption at
> > > > > > the pressures and temperatures involved in flying light aircraft ).
>
> > > > > > > I'm guessing: but I get the impression that the onset
> > > > > > > of turbulence over wings was also dependant on temp-
> > > > > > > erature, even when the density altitude is the same.
> > > > > > > * In Quantum Theory that makes sense.
> > > > > > > To start, warm air is more chaotic than cold air at the
> > > > > > > molecular level, and the chaos *seeds* the turbulence.
> > > > > > > You know, hot fluids are less viscous than cold and so
> > > > > > > less sticky. That's likely a secondary correction.
> > > > > > > Regards
> > > > > > > Ken- Hide quoted text -
>
> > > > > > So if warm air is more turbulent ( I think I can accept that ) wouldnt
> > > > > > that mean that at higher temperatures for the same density altitude
> > > > > > you would get less lift and require longer take off distance?
>
> > > > > " As previously stated the results are the other way around."
>
> > > > > > Cheers
> > > > > > Terry
>
> > > > > I checked what you "previously stated", and the words
> > > > > "correction" and "difference" didn't have the usual "+/-"
> > > > > in them.
> > > > > Is the Cessna handbook online, that will save time,
> > > > > I'm interested.
>
> > > > I coulnt find it on line, but I would be happy to scan and email the
> > > > page, or even email you the Excel spreadsheet with the data and my
> > > > calculations. *Then you can do all the quantum mechanics, vector
> > > > analysis, euclid geometry and *reverse differentiation your heart
> > > > desires, and report back to us. *Just let me know if you want to
> > > > recieve this info by email.
> > > > terry
>
> > > Let's see the posted info for all to see and then we all
> > > may examine the data equally, otherwise, shut the ****
> > > up. Don't waste our time.
> > > Regards
>
> > Now no need to be rude Ken, *its your choice how you spend your time,
> > its not me that is wasting it. *I posted a question which I thought
> > would be of interest to pilots of real aircraft for whom understanding
> > (or lack thereof) *of takeoff *performance data can literally be the
> > difference between living and dying. *I didnt post the data set
> > because it is large and it was not my intention to have others spend
> > hours analysing it. ( although anyone is welcome to it , and my full
> > analysis of it, but offf line) *I *found something that didnt gel with
> > my understanding, and sort reasons for the potential discrepancy. *As
> > for some of your suggestions Ken, all I can say mate is that you need
> > to come out of the clouds a little, most things in life are not as
> > complicated as you seem to think. *I am sure you could come up with a
> > thousand brilliant ideas, that even your Mensa friends would be
> > impressed by, as to the *possible reasons why a car might go put put
> > splutter , splutter and then stop.. but just checking the gas first
> > makes a lot more sense. *I like physics and maths too and whilst I do
> > have a PhD in science ( physical chemistry) I am certainly no genius.
> > I have spent many many hours mathematically analysing a lot what is
> > involved in flying, from navigation problems, density altitudes with
> > corrections for humidty, wt and balance, radius of a turn with
> > correction for crosswind ( thanks Cain Liddle) *, *I even wrote a
> > program for an air traffic controller who wanted to be able to predict
> > the wind speed and direction from radar tracks and flight plan
> > information for multiple aircraft..... But you know what, *none of
> > this stuff has ever required *anything I didnt learn in high school,
> > like a good grasp of trigonometry, solve a quadratic here and there,
> > Newtons Laws, the gas equations etc. * * For christ sake leave the
> > quantum mechanics and anti viscosity discussions to your Mensa
> > meetings.
> > Terry
>
> Well heck, I didn't get a High School Diploma!
> What *****es me off* is the take-off roll for the
> C-152 is ~ 735', so although your using a C-172,
> the variation of 300' between 0C and 40C at constant
> density altitude is rather high.
> Regards
> Ken- Hide quoted text -

You didnt get a high school diploma, now I am impressed! (i am not
being sarcastic either) but I still go with what i said about
searching for the simple answers first. The 300 ft variation between
0 and 40 C was at 8000 ft density altitude where the takeoff distance
was around 2600 ft, so percentage wise it is not huge but enough to be
concerned about.

[Ken S. Tucker]

On Jan 17, 11:40 am, terry > wrote:
> On Jan 15, 10:24 am, quietguy > wrote:
>
> > Your PA-to-DA calculations clearly differ from Cessna's, probably
> > because they used a different standard atmosphere. There are plenty
> > to choose from: International SA, U.S. SA, ICAO SA (all revised over
> > the years) and some others, some of which are no longer used. You'd
> > need to find out which SA was used by Cessna when the 172N was built.
> > Good luck with that project. I would just plot some points from the
> > POH and draw a smooth curve connecting them; I'd be conservative in my
> > choices of data points and call that good enough.
>
> Some very sensible suggestions quietguy, I know I could just be
> conservative and plot a curve through the higher set of data on the
> graph, but
> the curiosity in me just wants to find the reasons. I think you are
> probably right about the standard atmospehere and i have had no luck
> yet finding out exactly what Cessna used, but I can tell you after
> some manipulation of the data by just changing the correction factor
> for pressure to density altitude of 120 feet to 80 feet per 1 degree
> off isa standard atmosphere temp, the points revert to the single
> smooth line of takeoff distance vs density altitude that I was
> expecting.
> Does that ring any bells with anyone re some other version of a
> standard atmosphere?
> Terry

Yeah, the usual is Lift =~= density * (air speed)^2,
(all other things being equal).

However Mr. Logajan provided this chart,
http://www.engineeringtoolbox.com/air-absolute-kinematic-viscosity-d_...

and I was surprised to find a Viscosity diff of 8%
between 0C and 30C.
The reason I went to Quantum Theory is because it' s
sometimes easier to go down to the basement to
figure out why the house is sinking. QT can be easier
terms than high level *classical gas* physics.
((yes the song)).
Regards
Ken

[terry]

On Jan 15, 10:24*am, quietguy > wrote:
> Your PA-to-DA calculations clearly differ from Cessna's, probably
> because they used a different standard atmosphere. *There are plenty
> to choose from: International SA, U.S. SA, ICAO SA (all revised over
> the years) and some others, some of which are no longer used. *You'd
> need to find out which SA was used by Cessna when the 172N was built.
> Good luck with that project. *I would just plot some points from the
> POH and draw a smooth curve connecting them; I'd be conservative in my
> choices of data points and call that good enough.

Just when I thought this was the correct reason. I have now further
analysed the data in the flight manual and looked at the landing
distance required data which was in exactly the same form , ie a table
of distance required as a function of different combinations of
pressure altitude and temperature. With this data table after
converting to density altitude, i get a nice smooth curve of landing
distance required vs density altitude ( as I would have expected with
the take off distance data). This would seem to eliminate the use of
a different standard atmosphere as the cause of the discrepancy.
Whilst I will certainly take your advice and use the conservative
line, my curiosity ( and stubboness) wont rest until I understand the
reason for this.

I am sure someone at Cessna would be able to explain it. Anybody know
who I should contact?

terry

[Bertie the Bunyip[_22_]]

terry > wrote in news:11884665-471a-47c3-881b-
:

> On Jan 15, 10:24*am, quietguy > wrote:
>> Your PA-to-DA calculations clearly differ from Cessna's, probably
>> because they used a different standard atmosphere. *There are plenty
>> to choose from: International SA, U.S. SA, ICAO SA (all revised over
>> the years) and some others, some of which are no longer used. *You'd
>> need to find out which SA was used by Cessna when the 172N was built.
>> Good luck with that project. *I would just plot some points from the
>> POH and draw a smooth curve connecting them; I'd be conservative in
my
>> choices of data points and call that good enough.
>
> Just when I thought this was the correct reason. I have now further
> analysed the data in the flight manual and looked at the landing
> distance required data which was in exactly the same form , ie a table
> of distance required as a function of different combinations of
> pressure altitude and temperature. With this data table after
> converting to density altitude, i get a nice smooth curve of landing
> distance required vs density altitude ( as I would have expected with
> the take off distance data). This would seem to eliminate the use of
> a different standard atmosphere as the cause of the discrepancy.
> Whilst I will certainly take your advice and use the conservative
> line, my curiosity ( and stubboness) wont rest until I understand the
> reason for this.


Yeah, I can appreciate this.
I have seen figures run that come up with different figures at the end
before and what it appears to me to be is performance engineers using
differnet approaches.
>
> I am sure someone at Cessna would be able to explain it. Anybody know
> who I should contact?

Get on the phone and ask! Or e-mail them. They have an interest in
ensuring the flying public have confidence in how well their airplanes
perform. I believe if you ask five engineers to crank those figures you
will come up with five different appraoches and answers, though.

Bertie