Why is the altitude call-out different to the altimeter...

[Guest cliffie1931]

Sometimes, when coming in to land, the copilot calls out altitudes that are somewhat different to the altimeter reading.I assume he's calling out radio altitudes while the altimeter registers height aove sea level.Am I correct?Cliff

[lefteris 70]

Cliff-think about it for a second:You're 5 miles out from SLLP (LaPaz, Bolivia), coming in to land. Elevation there is 13,313ft. When do you think the altitude call-out for "fifty" should be called? :-)Yes, it's radio altitude, indeed!Best,

[Guest Buck Bolduc]

>Cliff->>think about it for a second:>>You're 5 miles out from SLLP (LaPaz, Bolivia), coming in to>land. Elevation there is 13,313ft. When do you think the>altitude call-out for "fifty" should be called? :-)>>Yes, it's radio altitude, indeed!>>Best,>I can hear it now:One three thousand three hundred sixtyOne three thousand three hundred fiftyOne three thousand three hundred fortyOne three thousand three hundred thirtyOne three thousand three hundred twenty:)

[aerdt 0]

Altimeters callouts are the distance between your current height and the runway elevation.What good would be an altimeter read-out announcing your actual height?Cheers,Pat

[michal 44]

>Altimeters callouts are the distance between your current>height and the runway elevation.Actually it is between the airplane and the ground directly below it, in a hilly terrain there could be a huge difference (approach to Aspen).Michael J.http://www.precisionmanuals.com/images/forum/pmdg_744F.jpghttp://www.hifisim.com/images/asv_beta_member.jpg

[Guest v1cut]

>Actually it is between the airplane and the ground directly>below it, in a hilly terrain there could be a huge difference>(approach to Aspen).Actually, you're wrong. It's the height above the airport (or the runway threshold). GPWS will let you know if you're in danger of rising terrain. The crew is only concerned with their altitude relative to the airport.TonyATP/CFII/MEI

[teropa 4]

I must disagree.The callouts come from the radio altimeter, which indicates aircraft height directly above the ground where the aircraft is flying. It is not referenced to any point in the ground other than what's directly below, much less to any preset airport terrain height.Tero

[Guest]

Correct. Of course at most airports runways are placed so there's ample level ground in the approach and climbout paths, but not everywhere.

[Guest cliffie1931]

Thanks Lefteris and you other guys!Now I know.............Following your note I tried taking off from La Paz but couldn't make it. I'll try again with less fuel but what degree of flaps were you using. Or did you only land?Cliff

[michal 44]

>Actually, you're wrong. It's the height above the airport (or>the runway threshold). GPWS will let you know if you're in>danger of rising terrain. The crew is only concerned with>their altitude relative to the airport.>>Tony>ATP/CFII/MEIAn ATP/CFII/MEI who does not know how radar altimeter works? Or is it an ATP *:-*Michael J.http://www.precisionmanuals.com/images/forum/pmdg_744F.jpghttp://www.hifisim.com/images/asv_beta_member.jpg

[Guest]

>Actually, you're wrong. It's the height above the airport (or>the runway threshold). GPWS will let you know if you're in>danger of rising terrain. The crew is only concerned with>their altitude relative to the airport.>So you're not concerned with the height of that 1000ft hill 3 miles from the treshold?Remind me to request a rescheduling if I ever catch you as my pilot.

[opherben 0]

Runways are built with strict specifications defining allowable sloping/ obstructions along centerline extensions, to avoid:>So you're not concerned with the height of that 1000ft hill 3>miles from the treshold?Exceptions exist but are well published (Kai TAK having been most extraordinary).The ATP guy was wrong as you stated about callouts.

[Guest]

Try Curacao. Not a thousand feet but your AGL drops to a few hundred feet momentarilly while you're a good while out and perfectly on slope.Rather confuzzles the callouts in the PMDG, you get 400ft and then nothing as it drops back to over a thousand a second later :)

[michal 44]

>The ATP guy was wrong as you stated about callouts.He confused GPWS with RA.Personally I doubt he is an ATP.Michael J.http://www.precisionmanuals.com/images/forum/pmdg_744F.jpghttp://www.hifisim.com/images/asv_beta_member.jpg

[Guest v1cut]

>>The ATP guy was wrong as you stated about callouts.>>He confused GPWS with RA.>>Personally I doubt he is an ATP.>>Michael J.>http://www.precisionmanuals.com/images/forum/pmdg_744F.jpg>http://www.hifisim.com/images/asv_beta_member.jpgI can assure everyone here I hold an ATP. I also know how a radar altimeter and GPWS works. I would be quite concerned with a mountain in my flight path, and you're more than welcome to reschedule your flight if I'm flying it. Now on back to the topic. If you go back to the original question and actually read it, it asks what altitude the CO-PILOT was calling out. It didn't ask anything about Radar Altimeter or GPWS. The NFP at every airline I've worked for or jumpseated on calls out the height above the airport on visual approaches and the height above the DH/MDA during instrument approaches. It's possible that in other parts of the world and at other airlines, things are done differently, I can only speak from the perspective of what I've actually flown or done.