Today we space going to take a rapid look in ~ what happens when you paris your plane from one area of high push to an area of short pressure and also when flying from warm air to cold air.

You are watching: High to low look out below

The altimeter error is what we room going to pay unique attention to and also why it is important to be mindful of the changes as us fly across country.

Change in Pressure

If us take a look at the snapshot below we deserve to see as soon as going indigenous an area the high pressure to one area of low push our aircraft will be lower than what it shows if we carry out not change the sub-scale setting on ours altimeter. This happens because as the area push decreases you shot and keep the aircraft reading the required altitude (in this situation 5000 ft) and also therefore willingly descend. Therefore to save you aircraft at the correct altitude over the ground girlfriend would have actually to adjust the sub-scale to the reduced setting, in this situation from 1018 to 1016.



High to low Look out Below

Change in Temperature

Similar to the above scenario, when we paris from a warm area to a cold area our aircraft will be lower than what it indicates if we perform not readjust the sub-scale setting on ours altimeter. A good way to think about this is if you were in a elevator “floating” over a shaft of wait which deserve to only expand/contract vertically, once that wait cools down the column shrinks and also therefore the elevator sinks. If you had an altimeter in the elevator it will certainly still be analysis the same, offering you the impression that you room at the exact same altitude wherein in truth you are lower.

HOT come COLD DON’T it is in BOLD


Hot come Cold don’t be Bold

I hope this simple explanation has actually helped. You re welcome leave any comments listed below if girlfriend don’t know or have any type of points to add for others benefit.
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Jessicaon January 29, 2018 in ~ 11:47 pm

Thanks because that this article! I understand how an altering the altimeter setup fixes the high pressure to low push scenario. And also I recognize that hot air expands/cold air retracts. But does to update the altimeter setup fix the warm air come cold wait scenario, keeping you at the correct altitude MSL? and also how?

Jim Garneron July 27, 2018 at 11:33 pm

“If you had actually an altimeter in the elevator it will certainly still be reading the same”

This is whereby I dropped off the elevator!

In every seriousness, I recognize the expanding and shrinking… however why would the elevator float in ~ a various level however the Altimeter remain the same? If over there is shrinking/contraction and expansion, wouldn’t that carry out the very same to the meter as is happening to the elevator?

Elliot bellon October 4, 2018 at 4:29 pm

Hi ns am having actually some confusion through reading various things online about temperature and also pressure. It seem to be contradictory and also i was hoping you might help?

A resource from Quora usually says, once molecules increase , thickness decreases. Check out Below.

“When pressure increases molecules come closer come each other which means increase in density and also when press drops molecules of gases become complimentary to expand and get away from each various other which way density decrease. Because in situation of gases pressure and also temperature room proportional come each other for a offered volume therefore in this method temperature additionally causes come the readjust in the density.”

And top top this website girlfriend explain:

“when the temperature of a mass of waiting is raised it will expand, result in rise of pressure”


Anonymouson November 25, 2018 at 4:21 pm

This is the finest thing I’ve found on this and also I’ve been analysis everything. I’m a student pilot struggling v the various variations top top the FAA concerns for this. Most of the various other explanations room too complicated and technical. Meanwhile, it’s an easy physics. Great writers room rare!

Amin Nasiri, one Air traffic controller in Tehranon December 18, 2018 at 6:28 pm

hi dear admin.I desire to insure the in cold air press will rises but because of retracting that the wait mass the related push at the ground level will certainly decreases so as soon as we are saying “flying native high to low” we mean that the air pressure at the soil level to reduce or temperature decreases.other point that I desire to for sure is that just how much is the maximum range of ground pressure changes in a allude with considering the temperature changes (max range of alters in height).thank you.

Liam Baldwinon November 15, 2019 at 4:05 pm

Good afternoon.

I’m likewise slightly confused. I’ve review in several publications that;

As the planet warms the mass of waiting directly over it through condensation, the warmer, less thick air will begin to rise. Bring about a low surface ar pressure?

Likewise, with a cold denser air cooling and also sinking, raising the surface pressure?

So why and how does the over statements come right into “from high (cold sinking) to low (warm rising) look the end below”?

This no make feeling to me. I’ve review travelling from heat air come cold air will result in her altimeter over analysis (meaning you’re reduced than indicated). This is therefore earlier to native in regards come the surface pressure statements I’ve stated above.