Correct ILS Question

[Guest]

I am wanting to learn more about the DH 200 that apprears in the lower right corner of my flight display. When I get closer to the runway the altitude, I think, will show and beging to decrease. Usually the altitude here and what is on the altimiter are always off.What does the DH do and will this adjust the altitude? I tried changing from 200 up to 300 and down to 100 but did not notice any change.Thanks for the help. I land down the middle but just want to know more.Denny ONashville, TN

[Guest]

The DH is your Decision Height above the runway.Of course it will differ from your altitmeter because it is a radar altimeter, it measures the distance from the aircraft to the surface unlike your altimeter which measures above sea level.You can adjust it to alert you to the decision height that is appropriate to the approach you are making.For a full ILS it would be 200 but a localizer approach may be 300 or 400 ft. and you set the Radar Altimeter to that height above the ground.

[Guest]

DH is actually your Decision Height--in this case 200 feet. Basically, at 200 feet, you must decide if you are going to land, or if you are going to go around. It will not affect your altitude on your altimeter in any way. :-waveJay

[Guest]

Makes sense to me. Thanks for your quick response.Denny ONashville, TN

[Guest]

Yes Denny as mentioned DH stands for decision hight the "standard"D.H. on an ILS is usually 200 and one half I.E. 200 ft agl and 2400 ft visibility but that varies of course so one of the things one does before decent is to get the approach in use from say ATIS thenget out the Jepp plate for that runway and set the D.H. as a reminderthat you are at the D.H and if the runway enviorment is not in sightone would then execute the published missed approach for that approach. Hope this is of some help Dan