why high to low, look out below?

Peter Duniho wrote:

And forget all the stuff others have posted about temperature. That
does nothing but confuse the issue.

The issue is already confused. People like you who want to pretend it's not
only serve to confuse it even more.

"People like you" who have no lives outside of making annoying posts
that say nothing are the scourge of Usenet. To the permanent bit bucket
you go...

Forget "all the stuff others have posted about temperature" at your own
peril. It's every bit as important an altimeter error as that caused by
changes in pressure.

The original question was about "high to low, look out below".
Temperature effects are completely unnecessary in forming an explanation
for that adage. What credentials do you have to back up your
blathering? On second thought, I think you'd be doing us all a favor if
instead you just went away.

Jim Rosinski

Peter Duniho wrote:
"jim rosinski" wrote in message
oups.com...

And forget all the stuff others have posted about temperature. That
does nothing but confuse the issue.


The issue is already confused. People like you who want to pretend it's not
only serve to confuse it even more.

Forget "all the stuff others have posted about temperature" at your own
peril. It's every bit as important an altimeter error as that caused by
changes in pressure.



While temperature may play a role in altimeter "errors" I believe
it's extraneous to the discussion at hand. The phrase in question says
nothing about why the pressure is changing, only that it does. The
effect of this pressure change on altimeter readings can - and has
been - adequately explained without discussion of temperature.

We can always discuss temperature effects once the pressure effects
are understood. Trying to get someone to grasp two separate concepts at
the same time when it's not necessary does only serve to confuse the
student.

Increase in density does not mean an increase in pressure. This is
where your error is.

"Rich Lemert" wrote in message
ink.net...
While temperature may play a role in altimeter "errors" I believe
it's extraneous to the discussion at hand.

Why would you believe that? People can and do use that very same mnemonic
to remember the effect of temperature on the altimeter indication.

To pretend otherwise is silly. It happens, and so given that it happens, it
makes perfect sense to explain the error and why the phrase fits (albeit
imperfectly, AS I ALREADY POINTED OUT, before the post that claimed
temperature was irrelevant).

The phrase in question says nothing about why the pressure is changing,

The phrase in question says nothing about pressure at all. The word
pressure is not even used.

only that it does.

The only thing the phrase say that anything "does", is that the altimeter
reads too high in certain circumstances.

The
effect of this pressure change on altimeter readings can - and has
been - adequately explained without discussion of temperature.

The effect of this temperature change on altimeter readings can - and has
been -adequately explained without discussion of temperature.

We can always discuss temperature effects once the pressure effects
are understood. Trying to get someone to grasp two separate concepts at
the same time when it's not necessary does only serve to confuse the
student.

As long as the exact same phrase gets used for two different concepts, you
are stuck teaching two different concepts at the same time.

Now, maybe that really means people ought to stop using the mnemonic. But
you and I have no control over it. Pretending that temperature is
irrelevant is dumb, and is likely to get someone killed.

Pete

"Peter Duniho" wrote in message
...
The effect of this temperature change on altimeter readings can - and has
been -adequately explained without discussion of temperature.

See what copy and paste will get you?

Obviously, that last word should be "pressure".

Andrew Sarangan wrote:

Increase in density does not mean an increase in pressure. This is
where your error is.

Actually it does if the air, or layer of air, you're talking about is
isothermal (constant temperature) or anything close to it. The ideal
gas law, to which the real atmosphere very nearly adheres, states:

pressure = density times temperature times a constant.

Imagine you're in freefall. Pressure goes up and density goes up. And
the above equation tells you by how much, assuming for the moment that
you have a barometer, an isothermal atmosphere, and a calculator during
the plunge!

All this is completely useless for understanding the "high to low, look
out below" rule.

Jim Rosinski

IFR in mountainous areas requires 2,000 above obstacles with
5 miles of the intended route. Considering that an
altimeter setting may be from a location nearly 100 miles
away and the temperature may be very much below standard,
that 2,000 foot terrain clearance may be reduced to 0 by
temperature, pressure and venturi effects in the mountains.
Try the calculations on your flight computer for true
altitude. VFR and you should see the granite, but IFR or at
night, you depend on the altimeter.
Of course, now that you can get a GPS altitude that has non
of the errors, you can see the altitude errors on the
pressure altimeter.

Altimeters have other errors besides temperature and as a
purely mechanical device they can fail with no indication at
all. The electric altimeters in the high dollars airplanes
(King Airs and jets) use an air data computer that processes
the raw pressure data and sends the result to a display.
These will flag when there is an error, but the cheap
altimeter used in most general aviation piston airplanes has
no such warning. Thirty years ago one manufacturer decide
to save a few bucks in construction and used Teflon tape for
bearings in the housing. When this tape broke loose and
jammed the gears, the altimeter would just freeze. I once
had a student out in central Illinois doing hood work on a
MVFR day. He seemed to be doing a good job as we flew
around under a 1500-2000 foot overcast. When he took the
hood off, his first remark was "How did we get so low?"
Since I'd been watching in and outside, the slow loss of
altitude did not reach the alarm stage, we were below the
clouds and above the ground. But when he went under the
hood he had a picture of what it looked like and when the
hood came off it was very different and quickly.


--
James H. Macklin
ATP,CFI,A&P

--
The people think the Constitution protects their rights;
But government sees it as an obstacle to be overcome.
some support
http://www.usdoj.gov/olc/secondamendment2.htm



"Peter Duniho" wrote in
message ...
| "Rich Lemert" wrote in message
|
ink.net...
| While temperature may play a role in altimeter
"errors" I believe
| it's extraneous to the discussion at hand.
|
| Why would you believe that? People can and do use that
very same mnemonic
| to remember the effect of temperature on the altimeter
indication.
|
| To pretend otherwise is silly. It happens, and so given
that it happens, it
| makes perfect sense to explain the error and why the
phrase fits (albeit
| imperfectly, AS I ALREADY POINTED OUT, before the post
that claimed
| temperature was irrelevant).
|
| The phrase in question says nothing about why the
pressure is changing,
|
| The phrase in question says nothing about pressure at all.
The word
| pressure is not even used.
|
| only that it does.
|
| The only thing the phrase say that anything "does", is
that the altimeter
| reads too high in certain circumstances.
|
| The
| effect of this pressure change on altimeter readings
can - and has
| been - adequately explained without discussion of
temperature.
|
| The effect of this temperature change on altimeter
readings can - and has
| been -adequately explained without discussion of
temperature.
|
| We can always discuss temperature effects once the
pressure effects
| are understood. Trying to get someone to grasp two
separate concepts at
| the same time when it's not necessary does only serve to
confuse the
| student.
|
| As long as the exact same phrase gets used for two
different concepts, you
| are stuck teaching two different concepts at the same
time.
|
| Now, maybe that really means people ought to stop using
the mnemonic. But
| you and I have no control over it. Pretending that
temperature is
| irrelevant is dumb, and is likely to get someone killed.
|
| Pete
|
|

Peter Duniho wrote:

The phrase in question says nothing about pressure at all. The word
pressure is not even used.

My apologies to the group for so immediately violating my own stated
rule to ignore this person's posts forever more. But I just can't sit
back and let him spew utter nonsense without challenge. Good GOD man,
when you see the phrase "high to low, look out below" in an aviation
book they mean high to low PRESSURE. They assume the reader has the
intellectual wherewithall to take it from context when they see the big
high and low pressure icons on the same page!

BTW, the moral of the whole "high to low (pressure), look out below"
thing is to make sure on a cross-country or IFR flight to get altimeter
setting updates regularly.

Jim Rosinski

jim rosinski wrote:

Peter Duniho wrote:

The phrase in question says nothing about pressure at all. The word
pressure is not even used.


My apologies to the group for so immediately violating my own stated
rule to ignore this person's posts forever more. But I just can't sit
back and let him spew utter nonsense without challenge. Good GOD man,
when you see the phrase "high to low, look out below" in an aviation
book they mean high to low PRESSURE. They assume the reader has the
intellectual wherewithall to take it from context when they see the big
high and low pressure icons on the same page!

http://math.isu.edu/~wolperj/cold.html

Do you want to admit now that you are wrong or keep arguing? :-)

Matt

It is clear that they meant both pressure and temperature.


"jim rosinski" wrote in message
news:uRwdf.2687$Mr4.335@trnddc08...
| Peter Duniho wrote:
|
| The phrase in question says nothing about pressure at
all. The word
| pressure is not even used.
|
| My apologies to the group for so immediately violating my
own stated
| rule to ignore this person's posts forever more. But I
just can't sit
| back and let him spew utter nonsense without challenge.
Good GOD man,
| when you see the phrase "high to low, look out below" in
an aviation
| book they mean high to low PRESSURE. They assume the
reader has the
| intellectual wherewithall to take it from context when
they see the big
| high and low pressure icons on the same page!
|
| BTW, the moral of the whole "high to low (pressure), look
out below"
| thing is to make sure on a cross-country or IFR flight to
get altimeter
| setting updates regularly.
|
| Jim Rosinski