Pressure Altitude - [What it is, How to calculate Pressure Altitude and why is it important??]

How to calculate the Pressure Altitude, what is it and why is it important??
The Pressure Altitude (PA) is the height of aircraft above the Standard Pressure 1013.25Hpa or 29.92Hg, and it is important to understand what it is because the Aircraft Performances are based on the PA.
In a standard Atmosphere the pressure at the mean sea level, also called QNH, is equal 1013.25Hpa.
So, in Standard Atmosphere, an aircraft that is on the threshold of a runway with 0 feet of elevation has a Pressure Altitude of 0 feet, and an aircraft on a runway that is at 1000feet of elevation has a PA of 1000feet.
It is important to understand two factors:
1. The pressure at the mean sea level (QNH) is not always 1013.25 Hpa, it can change rapidly due to the pressure system of the Atmosphere.
2. The Aircraft doesn't care about the physical elevation of the runway, it cares about the pressure that is around it.
So, if we take the example that I made before but this time we change the QNH to 1000hpa what will happen is the following:
The real Aircraft Altitude stays constant however, the Aircraft, will feel that is at a higher Altitude because the pressure is lower than 1013hpa.
With the lower pressure, the Air is less dense so the aircraft performance will be impaired.
If we compare the two examples we will see the Aircraft in the second case (QNH 1000hpa) will need a longer Take Off Run for the take-off.
In order to calculate the Pressure Altitude, we need to know that in a standard atmosphere for every hpa there is a difference in altitude of 27feet.
The difference between 1013hpa and 1000hpa is 13hpa, if we multiply the 13 by 27 we will come up with the Pressure Altitude of the Aircraft, which is 351feet.
When you are preparing for takeoff you need to know your QNH and correct your Allowed Takeoff Weight.
If you want to know more about Altimeter Settings watch the following KZbin video:
WHAT IS QNH, QNE, QFE: • QNH, QFE and QNE - [A...
ALTITUDE vs HEIGHT vs FLIGHT LEVEL: • QNH and QNE Altimeter ...
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Disclaimer:
THIS VIDEO IS FOR ENTERTAINMENT PURPOSES ONLY.
NOT FOR REAL-LIFE OPERATIONS.
PLEASE REFER TO THE OFFICIAL MANUAL AND DOCUMENTATION.
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[@PILOTCLIMB]

Let me know if you have any question regarding the Pressure Altitude !! Happy Landings....

[@FreSch_Dude]

Starting off with my PPL training, and I was taught how to calculate PA a little differently, but it seems like I come to the same (in this case similar) result. I take the QNH, subtract it from the 1013, then multiply with 27feet, then add the aerodrome elevation after-the-fact. So for this example: 1013-1000 = 13hPa. 13hPa * 27ft = 351ft 351ft + 1000ft = PA of 1351ft. (off by 1 foot from your example, but I believe the 27ft is also just an estimate either way) Still, nice to see another way of calculating it, and it helped me understand the concept a little more.

[@PILOTCLIMB]

I'm glad to read this! Thanks for watching!

[@ahmedsmart1120]

Hello Captain. Thank you very much for this video and the useful formulas. For better understanding i would like to ask a few questions. For example: Marrakech Airport GMMX Has one runway 10/28. For Rwy 10 the charts tells: 1506ft Rwy Elevation 54 hpa Runway Elevation Metar: QNH 1017, Temp 28, Dew 1. 1506 ft/27 ft = 55,78 hpa pressure difference from mean sea level to the aircraft 1017 hpa - 55,78 hpa = 961,22 hpa (pressure around the aircraft) Pressure Altitude: 1013,25 hpa - 961,22 hpa = 52.03 hpa (difference between standard atmosphere pressure and pressure around the aircraft) 52.03 hp x 27ft = 1404.81ft (pressure altitude) So real elevation of RWY10 is 1506ft. But with higher local pressure of 1017hpa, the aircraft would behave like it would be at 1404.81 ft, which means better performance. Is that correct? But still i dont know what the meaning of 54hpa is which is written on the approach chart for Runway 10.

[@PILOTCLIMB]

Hey, many thanks for watching the Pressure Altitude video. I'm very glad to see you understood the concept correctly. The calculations and conclusions you made in the example are all correct!! Congratulations!! You didn't do a single mistake!! WELL DONE. The 54hpa next to the Runway Touchdown elevation is the difference in pressure between the Touchdown Zone of Runway 10 and the Mean Sea Level. If you multiply the 54hpa by 27 you will get the elevation of the touchdown for runway 10. This can be used to calculate the QFE if only the QNH is given. For more information about the QFE watch the video below: kzbin.info/www/bejne/baPNfWV5iM52rLM The QFE is rarely used during operations. Let me know if you have more questions!! I wish you a great day! Gabriele

[@frysimulation]

Just discovered your channel, and as one who is learning about navigation I find your topics of great value

[@PILOTCLIMB]

Many thanks for your kind comment!! Don't hesitate to ask me any questions when watching the rest of the videos! Have a great day

[@ThePlymouthRoadSurfer]

Fantastic explanation. Thank you!

[@PILOTCLIMB]

You are very welcome

[@mulakatserkan9982]

First time, I have completely undstood what pressure altitude

[@PILOTCLIMB]

That's great!! Many thanks for watching!! 👌

[@issyb7394]

Great video! I was just curious why pilots need to know pressure altitude whys it’s important ? Thanks

[@PILOTCLIMB]

Thanks for watching

[@sumitcreations3072]

Sir make a video on low pressure area and high pressure area 👍 please

[@PILOTCLIMB]

Hey, I hope you are doing great! I'll take your suggestion into consideration for a future video👍

[@tothzoltan89]

Hi Gabriel, First of all, thank you for your efforts, extremely helpful. I have a frozen ATPL but time to time it is essential to refresh my memory and watching your videos is a great way. Just a question though to make it clear. So the performance doesn't only depend on the pressure altitude but the density altitude. To calculate density altitude you have to calculate pressure altitude first. Am I right?

[@PILOTCLIMB]

Yes, you can apply the density Altitude correction after the PA correction

[@Danyghaddar]

again best videos ever , would like to know about DGI errors ( direction gyro idicator errors calculations thanks

[@PILOTCLIMB]

Many thanks for your kind comment! I will take you your request into consideration for a future video!

[@Vlad-fo1ic]

I like your videos and simple explanations 👍 Thnk you Captain))

[@PILOTCLIMB]

You are welcome!! Thanks for watching! Have a great day!

[@MrCed0802]

Finally making sense :) thank you !

[@PILOTCLIMB]

Let me know in the future if you still have any doubts about the topic!! I wish you a great day! Gabriele Pilotclimb

[@michaelschwartz9485]

Great explanation!

[@PILOTCLIMB]

Thanks for your support

[@orhananildemir4022]

Thank you for your effort

[@PILOTCLIMB]

You are very welcome!!

[@grigoriosdelaportas4380]

why so many calculations when we can easily subtract 1000hpa from 1013, That gives us 13 hpa difference which when multiplied by 27 we get 351. Add 351 to the 1000 feet and we get the 1351 pressure altitude. I thought I should share. Thanks for the presentations

[@PILOTCLIMB]

Many thanks for sharing your point !!

[@ExtremeMotivation07]

Can u define difference btw altimeter vs pressure altitude table what will the consequences or outcome of it? Because I'm trying to interpolating it so, I must know the things perfectly where they stand first.

[@PILOTCLIMB]

Altimeter and pressure altitude are different, the altimeter indicates to the pilot the vertical difference , expressed in feet, between the pressure reference and the aircraft. The pressure Altitude is the Altitude that the aircraft feels, which could be different from the actual Altitude..

[@lonelysail906]

👍

[@PILOTCLIMB]

Many thanks for watching

[@ExtremeMotivation07]

Means basically at lower flight level corresponding to higher pressure altitude the aircraft's turbofan engine efficiency will be low or airfoils are not generating enough lift?.. or prolly something else,,,, waiting for ur answer sir.....,,,,,,,

[@PILOTCLIMB]

The lower the flight level the lower will be the pressure altitude and, the higher the pressure, so the Aircraft performance are better at lower pressure ALTITUDE.

[@ExtremeMotivation07]

Thanks a lot sir

[@PILOTCLIMB]

@@ExtremeMotivation07 you are welcome!! Let me know if you have more questions 👍

[@ExtremeMotivation07]

Sir, How this pressure altitude affects the aircraft's performance?

[@PILOTCLIMB]

Hey, thanks for watching, the higher the pressure altitude the worsen the aircraft performance.

[@vantranthi398]

@@PILOTCLIMB as I know pressure altitude is the vertical disance btw airplane and constant pressure surface of 1013hPa. When the airplane is on RWY so PA is elevation. Could you explain me again why "the higher the pressure altitude the worsen the aircraft performance.". Tks in advance.

[@PILOTCLIMB]

@@vantranthi398 Hey, try to watch the video again, it will help for sure. When you are on the runway you are, physically, at Airport Elevation, however, the aircraft doesn't think that way, the Aircraft only cares about the pressure and temperature around. Watch the video regarding density altitude as well, Video link: kzbin.info/www/bejne/oYnNlHefoMRroKs

[@fedorovich201067]

Thanks a lot for this brilliant explanation! Got it finally:)

[@PILOTCLIMB]

Hey, I hope you are doing great!! I'm very glad the Video helped you out!! Many thanks for watching!! Don't hesitate to ask me any question you may have!! I wish you a great day!! Gabriele

[@fedorovich201067]

PILOTCLIMB Gabriele, if you’ll have a time and opportunity, wanted explanation about fuel tankering from you! I’m student pilot and your videos very helpful:)

[@PILOTCLIMB]

@@fedorovich201067 Hey, I hope you are doing great!! I'm very glad to see that my videos are helping you!! I will do the video about the Tankering Operation very soon! Make sure you subscribe to the PILOTCLIMB channel, if you haven't already, so you won't miss it when is out!! don't hesitate to comment with your thoughts and questions!! I wish you a great day! Gabriele

[@PILOTCLIMB]

@@fedorovich201067 I made the video regarding Fuel Tankering, it will be available soon, stay tuned 👍 have a great day Gabriele Pilotclimb

[@zululimaecoindia9773]

What about just use the difference between the standard pressure and actual pressure, which is 13.3 and multiply by 27 then add 1000 feet? The result seems to be more or less the same.

[@PILOTCLIMB]

Hey, thanks for watching!! You could do that if you know the pressure around your aircraft..

[@ExtremeMotivation07]

Plz sir give the reply of ques. asap cuz' I'm working on project regarding it.......

[@PILOTCLIMB]

Hey, check the answers and let me know if you still have any questions..

[@ExtremeMotivation07]

Thank u so much sir for ur effort!!,,,,,,,

[@suhailummer2697]

❤❤❤

[@PILOTCLIMB]

Thanks for watching

[@AccordionandViolinlife]

isn't it 30 Ft that it decreases by one hectopascal?

[@PILOTCLIMB]

Hey, thanks for watching.. Yes you can use 30feet aswell. Normally 30 feet it is used for high altitudes and 27 feet for low altitudes calculations...This is so because at low altitudes the pressure is higher thus the isobars are squeezed. Let me know if you still have any questions. Have a great day

[@lebnetfelcousina4039]

The question is : your flight level is fl 85 and the temperature is ISA-20 what is your pressure altitude.¿

[@cansu8564]

[@PILOTCLIMB]

Thanks for watching all these videos

[@ExtremeMotivation07]

Sir, How this pressure altitude affects the aircraft's performance?

[@PILOTCLIMB]

Hey, thanks for watching, the higher the pressure altitude the worsen the aircraft performance.

[@ExtremeMotivation07]

Means basically at lower flight level corresponding to higher pressure altitude the aircraft's turbofan engine efficiency will be low or airfoils are not generating enough lift?.. or prolly something else,,,, waiting for ur answer sir.....,,,,,,,