OK, I’ll see how that one goes down on our side of the Pond. I anticipate a certain discomfort but no rational opposing argument. :)
Regarding terminology/categorisation:
2D vs 3D (I know NCYankee is not a fan!)
CDFA
DH vs MDH
I put together the following. Any comments please?
We also have LP and LP+V. I have no issue with terminology of 2D verses 3D, but do have an issue with name changes of approach names for no useful reason other than new players in the game.
We don’t have any LP in Europe yet so I didn’t include those, but for the purposes of the table they’d be the same as LNAV and LNAV+V.
Oops. LPV200 a precision approach? I guess some would ask for a source for that … is Cat I always PA as per definition?
Very useful table. Regarding 3D and 2D, I understand this as “how the approach is actually guided vertically” rather than an entity of the approach procedure itself. In other words, to determine whether it is 2D or 3D you have to be in the cockpit and see which instruments the pilot (or a/p) is looking at in order to navigate vertically. If it is a “needle”, i.e. someting indicating a deviation from the nominal glidepath, then it is a 3D operation.
CDFA is minus zero on the MDA, 2nm and 5nm step down fixes and DA, but with out these step down fixes which would govern a dive-and-drive (typically levelling off 50 feet above), the CDFA standard is +/- 100 feet and at 50 feet to go you are treating the MDA as a DA. This would occur around 0.9 nm from the runway threshhold, and with a minima of 750m the ALSF-II system should be visible at this Decision point (1100m plus 750m is more than 0.9 nm).
I don’t know why the LPV has a higher DA, but the increased RVR requirement also means that on the DA for the LPV you would also be acquiring the approach lighting system.
huv wrote:
Oops. LPV200 a precision approach? I guess some would ask for a source for that … is Cat I always PA as per definition?
I originally put ??? in that box and then decided to be provocative. 
I sat next to an Airbus test pilot yesterday who insisted that it is a precision approach, and I have no reason to doubt him.
The other controversial issue is the use of OCH as DH (without increment) on a CDFA
bookworm wrote:
The other controversial issue is the use of OCH as DH (without increment) on a CDFA
I’ve never heard anyone suggest that you could do that. Technically, you still deal with an MDA, even though you will determine a DDA (derived decision altitude) for your type of airplane and operation that will permit you not to bust that MDA if you look out at your DDA, see nothing and initiate a go-around.
I have been taught to use 50 ft as add-on to the MDA during my IFR training, but have also been taught that this was in my discretion. 0 ft would never be enough though.
@bookworm I don’t understand your use of DH for the non-precision approaches flown as CDFA. My understanding (which may very well be wrong), is that it is always an MDH/MDA for a non-precision approach, not a DH/DA, ie. minus zero tolerance.
Now, you may very well use a DH/DA based technique to fly the approach, but the official minima is always a MDH/MDA, no??
I did say it was controversial! The current Part-NCC and Part-NCO implementing rules allow you to do this, even though the GM discourages it. A strong case is put by airlines to allow it. I tend to agree.
ortac wrote:
always an MDH/MDA for a non-precision approach, not a DH/DA
That is what I learned too, but then I realized that DA’s kept creeping in on Jeppesen plates on non-precision approaches more and more (escorted by CDFA mods to the approaches). In my experience, the widespread uncertainty is whether a non-precision DA can be treated as such, i.e. as a DECISION altitude, not a zero tolerance altitude, originally called a minimum descent altitude – or if you can go below DA on the missed approach, just like everybody agrees you may on an ILS. If not, then what is the point of naming it DECISION height?
I believe the test standards for IR skill tests still require applicants to descent on NPA’s to MDA(H) +100/÷0 ft during missed approach, ignoring the fact that most NPA’s these days have DA’s attached. If so, are we still left in the dark?
Edit: I seem to have missed that Part-NCO is clear on this (sort of).
