RA or DH?( a320 FMGS approah page)

[flyjet]

Hi, I fly A321 as a F/o.. .my company start to apply CAT II approach on a321.. .I checked fcom4 for CATII approach.. .They only say 100 above DH.-100 above minimum. .at DH-minimum.. .but on the CAT II approach chart,there are 2 minimums,RA & DH.. .what should I insert in FMGS DH field?

[Flex33]

Check S.O.P's FCOM 3. Hopefully your company have issued you a section on LVO.

However, in the mean time use MDA for Non precision & Cat I, DH for Cat II & III(A&B).

Hope that helps.

[Pegasus77]

I read your question not as to where to enter your value... You only fill out the DH-field during a lovis-approach, as already stated, and use the MDA-field for everything up-to-and-including-CAT1.

But if given 2 different values, a DH and a RA, I would fill in the RA-number in the FMGC, because the a/c will generate an autocallout at minimum, based on your radio-altimeter, not your baro-altimeter.

Hope it helps!

[ 20 February 2002: Message edited by: Pegasus77 ]</p>

[fantom]

pagasus..not true. it is a customer pin-programme which determines callouts.. .for cat1 and non prec you must use the baro therefore insert in 'mda'. it is really a 'da' we are using but we won't quibble.. .for cat 2 and 3 the decision is based upon rad alt therefore the dh (for it is a height) is inserted in 'dh',not 'mda'. <img src="tongue.gif" border="0">

[ 20 February 2002: Message edited by: fantom ]

[ 20 February 2002: Message edited by: fantom ]</p>

[Pegasus77]

If what you say is true, then Flyjet should read his own AOM, to find out which input signal his company uses. My company anyway bases the callout on RA, therefore I type in the RA-minimum from the chart in the FMGC.

Seems weird to me, if the minimum is based on RA as it is in lovis-approaches, to make the minimums-callout on baro-altitude??

[fantom]

well spotted peg.. .the minimum is based on either, but for low vis the rad alt is close enough to the runway (or flat surface) to be useable. at points further out (like cat 1) you can not use the rad alt because of the terrain.you therefore use a DA for cat 1 (by which point the decision has been made) and,if you go around, you fly so as not to violate the associated MDA.of course, our mcdu does not have a field for 'DA' so we use the 'MDA' one. it is,in fact a DA we are inserting.it follows that any DA is higher than its associated MDA because of the sink which occurs on the go around. <img src="tongue.gif" border="0">

[flyjet]

thanks for reply.. .all of your comment are very helpful for me!!!!

[Iceman49]

I think it depends on what your company ops allow. We use MDA for non-prec and Cat I. The DH block is used for CatII and CatIII. We us NO DH for the Cat III, and an alert height of 100"RA, on CatII it depends if RA is authorized or not. If it is authorized we put that figure in the DH and call mins off of the RA or Inner Marker, whichever occurs first. If the RA is not authorized we use the MDA block, and call mins off of Barometric or Inner Marker whichever occurs first.