Sign in to follow this  
Guest RoSPA_David

Radio Altimeter / BARO ?

Recommended Posts

Please can some one explain these settings and what they should be, and what their functions are. If i use the example of the airport alt being 100 ft asl Many thanksDavid

Share this post


Link to post
Help AVSIM continue to serve you!
Please donate today!

Baro setting is the setting on the altimeter to correct for temperature and pressure. Around airports the ATC will give your the current setting as either Hpa or in inches Mc depending on where in the world you fly. Above a certain altitude which also changes depending on your location and is noted in the AIP's for that country you will change to the standard ICAO setting which is 1013 in Hpa or 29.92 inchec mc. Once you decent down again ATC will again give you the altimeter setting for your location and you will make the change on the altimeter to see the correct reading for that day and time.

Share this post


Link to post

sounds a little confusing there as im sure i dont get all that info from either atc or atis. I just usually set the alt to something in inchec mc as instructed, but are you saying i get more info? what about the radio alt then ? Can you give me an example please Regards David

Share this post


Link to post

Simply put....Radio altimeter gives you your height above the terrain (below you) and the baro altitude gives you your height (altitude) above mean(average) sea level. Radio altimeters use radio waves. Baro uses atmospheric air pressure.Radio altitude is considered more accurate for landing, but has a range limit of about 2600'. For the rest of flight, you need baro altitude (greater range and not so erratic over bumpy terrain). Hope this helps.Cheers.Q>(Edit) In your example, if the aircraft was sitting on the tarmac, the Radio Altimeter would read _about_ 0' and your baro altimeter would read about 100' (if you have set the inches/mb correctly).

Share this post


Link to post

Sorry yes, i was referring to the mins knob, which is why the first post confused meI have posted a plate for EGNV which i reguarly use. From what you have just said, am i to set the baro to 120 min and the RA to 116 Cheers David

Share this post


Link to post

Basically for this chart, you set the Bold number on the BARO and the number in (parentheses) on the Radio altimeter. For example, for the CAT1A, BARO 258, (RADIO 142).Keep in mind that for high elevation airfields like Johannesburg in South Africa, your BARO will be much higher than the radio. For the ILS 21 the runway threshold is at 5494 feel. You would use 5700 (200). This is because you will pass 5700 feet in altitude about 250 feel above the ground. Hope this makes sense.Also, where did you get that chart? It's a nice chart.Ryan GamurotLucky to live Hawai'ihttp://www.virtualpilots.org/signatures/vpa296.png

Share this post


Link to post

Dave,I'm not being funny mate but be careful about posting this type of chart on the forum because there must be some kind of copyright protection on it. As you are aware in order to access these charts you must set up a user account with UK AIS...they may not take too kindly to their products appearing on the web from unsolicited sources.I would hate to think that this vital source of RW documentation could be removed from the public domain.For all - if you want to access this site follow the link & set up an account...it's free & provides THE definitive in UK AIP charts:http://www.ais.org.ukPlease do not take offence to my comments...I am in no way trying to criticise your actions per se...Its great that there are so many of us here willing to share our knowledge for the greater good.Perhaps a forum moderator could remove the file & keep UK AIS 'sweet'?Kind Regards

Share this post


Link to post

good point dude, ill try and remove it myself. David

Share this post


Link to post

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