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#11
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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 |
#12
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why high to low, look out below?
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. |
#13
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why high to low, look out below?
Increase in density does not mean an increase in pressure. This is where your error is. |
#14
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why high to low, look out below?
"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 |
#15
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why high to low, look out below?
"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". |
#16
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why high to low, look out below?
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 |
#17
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why high to low, look out below?
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 | | |
#18
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why high to low, look out below?
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 |
#19
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why high to low, look out below?
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 |
#20
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why high to low, look out below?
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 |
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