HAT and DA
 

Hi All

Can anyone give a run down on the difference between these two?

More info in the Introduction of Jeppesen charts if you have them handy.

But in a nutshell:

HAT = Height Above Threshold

DA = Decision Altitude

DA is associated with precisions approaches (electronic glideslope).

DA is the altitude above mean sea level at which the pilot must have certain visual cues (e.g. lights) in sight in order to continue lower towards touchdown.

DH (= Decision Height) is the difference between DA (in MSL) and the elevation of the particular runway threshold.

MDA = Minimum Descent Altitude and is associated with non-precision approaches (no electronic glideslope).

HAT is the difference between MDA and the elevation of the particular runway threshold when landing "straight in" (more or less).

If circling then HAA = Height Above Airport and is the difference between MDA and airport elevation because you could conceivably circle to land any runway (unless stipulated as circling prohibited).

FYI = For Your Information.
Professional pilots continually confuse the terms DA, DH and MDA.

Your attention to detail will separate you from the rest.

:}

They do? I sure hope not.

GF

Surely you jest!? :(

If that were true then "continually confuse the terms DA, DH and MDA" certainly negates this "Professional pilots"

I'm as serious as a heart attack.

And don't call me Shirley.

:8

Not entirely correct anymore, nowadays a DA instead of a MDA is normal for a non precision approach as well.

DA DH MDA
 

Don`t forget the important bit - the most important bit, like:

what you may do at the MDA if nothing seen compared to what you must do at the DH if nothing seen - thought it worth a mention . . .

True, under non-EU-OPS rules.

I just intended to provide a "nutshell" (as I said) summary.

I realize there are many, many little details we could pick at, but for someone who just asked about the different between HAT and DA, I think he has enough to chew on for the moment.

:8