Many thanks all replies above !!
but my question just derives from the EASA regulation:
"The operator shall only conduct CAT II operations if the DH is determined by means of a radio altimeter"
Same words are in CAT 3 (as below), so the words can't solve my question.
CAT 3 regulations in EASA
According to the LOWW ILS 29 chart, there are 3 numbers depicted in CAT 2:
1. RA 97'
2. DA 700'
3. DH 100'
We know how the RA 97' comes from ( just as mentioned above), and DA 700' is advisory only which is applicable in some exceptional cases,
but, how about the DH100' ?
Why can't we setup 100' in FMS radio altitude field then rely on radio altimeter callout ?
If I do that, do I violate any regulation, expectation or something? fail in checkride ? <-- This is my real question.
Initially I thought it is about provider's legend, because there's no mention about RA 97' in LOWW's officially chart.
https://eaip.austrocontrol.at/lo/200..._24-6-4_en.pdf
LOWW 29 profile and minimums
( It also shows another question about the OCH for Category C in CAT 2 is 91' some guy mentions above. )
So I check the JEPPESEN's legend, but only get the words "Radio Altimeter height, associated with CAT 2 precision approaches". That's all, no mention about what I'm looking for like "RA numbers are prior to DH numbers" or "DH numbers in the chart is nothing if RA numbers are published" at all.
Jeppesen's label about DA(H) and RA
Then I google it, and find the story why RA numbers depicted in CAT 2 approach chart.
FAA recommendation document 1/2
FAA recommendation document 2/2
====
I summarize my finding and question:
In old time, CAT 2 approach uses radio altimeter and the associated DH depicted in the chart, but since the format is easy to confuse pilot to use DA, men in FAA suggest to change CAT 2 minima depiction to what we see now, a RA XX' been added.
Here is my question: The DH is still depicted in the chart, not been erased, so if no regulation mentions which has priority, or DH is advisory only, or something like that, how can we say RA is prior to DH to been used ? EASA regulation says only DH, never RA.
PS.
My company's manuals quote the words "DH is determined by radio altimeter" only, no mention about RA. But some peaky checkman could ask me this question someday.