gallois wrote:
Dive and drive needs an add on of 20’ or 50’ whereas CDFA needs no add on.
There is no need for any add-on to the MDA/H for a d’n’d approach – 2D approaches are designed with d’n’d in mind. (But the visibility minima are increased compared to CDFA.)
On the other hand, some people advocate an add-on to the MDA/H when you fly a CDFA. Part-NCO is contradictory on that point. The rationale is that if you don’t level out at the MDA/H you are inevitably going to descend slightly below it when initiating a missed approach and you’re not supposed to do that. OTOH, it is not difficult to show that the safety risks are minuscule, if there are any at all. The proposed revision to all-weather operation rules in part-NCO is explicit that no add-on is needed for a CDFA.
RobertL18C wrote:
Didn’t part.NCO do way with/discourage dive-and-drive non precision approaches and we all fly CDFA now? Note there is an intermediate step down MDA on the approach from 6.9D to 3.1D.
Actually not. Part-NCO recommends CDFA. Part-CAT makes them mandatory. (Except when you can’t use them, e.g. when the visual part of the final approach hits obstacles. There is a famous airport in the US -– can’t remember the name now.)
a climb gradient of 4.5% or 450ft per nm
4.5% = groundspeed * 4.5
At 100 knots that’s 450fpm or 450 feet in 1,67nm, right?
@ RobertL18C yes the glide slope of a CDFA is given in percentages on most SIA charts whereas Jeppesen usually give it in degrees. It’s something I am used to as I use both charts, I don’t really think of the difference between them. But I thought in this case we were talking about the percentages given under the API.
So sorry cross purposes.
@gallois the 5.2% is on the profile picture
@RobertL18C I am not sure what you are getting at. Usual missed approach would be 2.5% but here you need to be able to achieve a climb gradient of 4.5% or 450ft per nm in order to use the CDFA minima of 1820ft if not the 2.5% or 250 ft per nm minima comes into play ie 2080 ft.
Dive and drive minima are given on the profile view. Dive and drive needs an add on of 20’ or 50’ whereas CDFA needs no add on.
I think the percentages relate to the missed approach climb
@gallois that is stated in the minima, and it is always stated as a % gradient. The SIN of 3 degrees is 0.5233, hence 5.2% on the CDFA slope.
Didn’t part.NCO do way with/discourage dive-and-drive non precision approaches and we all fly CDFA now? Note there is an intermediate step down MDA on the approach from 6.9D to 3.1D.
The Jepp one
I think the percentages relate to the missed approach climb not to the CDFA. API normally relates to approach procedure interrupted. According to the local media, witnesses say they thought they saw a parachute before the crash.
Why not use the SIA approach charts, they are easy to use and best of all free?
@Airborne_Again I must get out more, I hadn’t realised people used any charts other than Jeppesen :)
