Sign in to follow this  
Guest Twister

What is the rule for updating the barometric pressure..

Recommended Posts

...calibration on the altimeter? Are you supposed to do so only when you are getting a new pressure reading from the ATC centre to which you are currently reporting?Just curious again :-) .

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

It depends. In the real world, you should update the altimeter at least every 100 nm. However, if you are in contact with ATC and they tell you the altimeter for your area, then you should update it. If they tell another aircraft in your vacinity, you can also change then. However, be carefule that they really are in your area. Also, you should update it before initiating an approach to land.In FS, ATC will almost always tell everyone the altimeter setting for YOUR position so you should just update it when they announce.

Share this post


Link to post
Share on other sites

ok,every airport has a so called "transition altitude"(e.g. in the U.S. this is 18000 feet for every airport,in Europe,most countries (and even airports) have a different transition altitude.Whenever you speak about an altitude below the transition altitude,you're talking about an altitude (e.g. when you have a transition altitude of 4500 feet,you talk about "3000 feet"),when you refer to an altitude above the transition level,you'll talk about a flight level(e.g. FL 60 when you have a transition altitude of 4500 feet).Whenever you're under the transition altitude,you msut set your altimeter to the correct QNH.so when you again have e.g. a transition altitude of 4500 feet,when you depart,you must adapt your altimeter untill you pass 4500feet:then you set you're altimeter to 29.29 (1013MB).when you descend through your destination airport's transition azltitude,you set you're altimeter again to the local barometric pressure.now,as FS2002 is quite american,it recognises 18000 feet for the transition altitude for the whole world.so whenever you're under FL180,you adapt you're altimeter,above 29.29edit:after rereading your post,I realised I told you something you probably already knew,sorry :)

Share this post


Link to post
Share on other sites

In the United States...Above 18000 = 29.92Below 18000 = Local Pressure (Altimeter setting)If the Local pressure is below 29.92, then 19000 becomes the transition altitude.Ryan-Flightpro08 :-coolVATSIM Pilot/ControllerZLA ARTCC Controller 1 (C-1)SAN TRACON Lead [link:www.taxiwaysigns.com]Taxiwaysigns.com Scenery Designer-----------------------------My "Home Made" System Specs:Intel Pentium 4 2.2GHz ProcessorTurbo Gamer ATX Mid-Tower with 420W Power SupplyEPoX 4G4A Motherboard with Intel 845G ChipsetVisiontek XTASY GeForce4 128MB Ti4600 (Det 29.42 WHQL Drivers)512MB PC2100 DDR RAM40GB Matrox 7200RPM Hard DriveWindows XP Home Edition SP1*No CPU or GPU Overclocking*3dMark2001SE Score: 11298

Share this post


Link to post
Share on other sites

Hmmm...If QFE means the altimeter reads 0 when you are on the runway, then no, not in my experience. At least, not commonly. The test pilots may have a different answer. --BeachComer Stephen "Beach" Comer Real World Pile-it Commercial ASMEL, Instrument Airplane 4500 TT, 2500 BE20 & BE10

Share this post


Link to post
Share on other sites

QFE means you're reading your altitude AGL and is IMO never used around the world.

Share this post


Link to post
Share on other sites

Actually it is in Europe, or at least when I flew in France. Even the LFPG (Charles de Gaulle) airport broadcast the QFE and the QNH to the ATIS for each runway. This is where a dual Altimeter comes handy. However, I suspected it was not the case in the US reading the above messages, and I wanted to be sure. Thank you for the replies!

Share this post


Link to post
Share on other sites

Hi Jean Luc,Having dual altimeters can come quite handy if you want to display both your QNH and QFE.The QNH will show your altitude above Mean Sea Level (or sea level pressure obtained from the local pressure and a standard gradient [1 mb of difference for each 30 foot of altitude between the reporting station and the actual sea level].For example: the airport in Courchevel (French Alps) cannot measure the actual sea pressure, the controller would have to run 800 kilometers to do so...! Instead, the controller checks the QFE [i.e. pressure in Courchevel] and calculates the Mean Sea Pressure [QNH] according to the standard gradient [1 mb of difference for every 30 feet of difference in altitude between the reporting station and sea level].As you understand, the REAL sea pressure might be quite different, but it doesn't matter as long as ALL the aircraft in the Courchevel region have set their altimeter with the same values (which also mean they won't run into each other because of differences in altimeter readings).As you have guessed, the QFE is the ACTUAL barometric pressure at the reporting station which means that an altimeter set to QFE will show O feet after landing at the station. it can be practical to know your exact altitude above ground (AGL).Hope this answers your questionTwister

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this