huv almost has it.
The issue arose when aircraft started flying with vertical guidance which didn’t technically meet the performance requirements of Cat I. So the Approach with Vertical Guidance (APV) terminology for procedures was invented to deal with this.
There remain 3 classes of instrument approach procedures.
(a) non-precision approach (NPA) procedure, which means an IAP designed for 2D instrument approach
operations with an MDH of 250 ft or above (i.e. Type A);
(b) approach procedure with vertical guidance (APV) means a performance-based navigation (PBN) IAP
designed for 3D instrument approach operations with a DH of 250 ft or above (i.e. Type A);
(c) precision approach (PA) procedure means an IAP based on navigation systems designed for 3D
instrument approach operations with a DH below 250 ft (i.e. Type B);
Type A and Type B, like 2D and 3D, are (in the ICAO schema) relevant to the approach operation, not the procedure. Unfortunately, the European Commission confused this in the PBN implementing rule which refers to (a) as a ‘2D approach’ and (b) and (c) as a ‘3D approach’.
To my experience, not even the EASA-OPS rule makers and the approach procedure creators agree on this, or are not certain.
I am quite sure that the correct definition used to be something “with vertical guidance”, and all other approaches were “non-precision”. I am also quite sure that when LPV approaches arrived on scene, they were put into a third category called APV – APproaches with Vertical guidance NOT qualified for the “precision” stamp, but also not “non-precision”.
Then came the 2D – 3D notation, which are not really approach categories, but operation types. However, those are what matter to pilots. Even those have been confused, with some authorities at some time claiming that a non-precision approach (LNAV e.g.) can never be a 3D operation, but I think they have been silenced now, with everybody agreeing that 3D is any approach with some kind of vertical guidance presented to the pilot on approved equipment.
CAT I, II and III are terms that depend on runway approvals, in addition to the approach technology. Can be ILS, MLS, GCA, GLS or LPV type B (Cat I only).
Yes, there is another classification, type A og type B approach, with the latter being those having OCH below 250 ft. That distinction is important to pilots needing to determine their own LPV minima; if an LPV approach is available on an approach having an OCH of below 250ft, e.g. 190 ft, then system minima applies, and they are 250 ft DH for type A LPV’s and 200 ft for type B. How do you check? Easy 
– just look up the vertical alert limit (VAL) value in the AIP: if it is 50 metres, then 250 ft applies; it needs to be only 30 metres to allow 200 ft… fortunately the pilot trusting Jeppesen or similar approved charts can trust these, at least regarding DA values.
I think the notations of precision or non-precision should be quietly forgotten; they serve to keep these discussions alive and not much else.
gallois wrote:
So the answer I was informed during these discussions to what makes a precision approach a precision approach comes down to the one line defintion “Any approach where the DH is 200ft or below”.
Of course, does it really matter? No.
In answer to @chflyer yes I was trying to generate a discussion because I wondered how many on this forum had heard of the definition changes which have been taking place over the last weeks or months. I understand that it is because of the type of discussions that have taken place on forums like this regarding whether or not an LPV or 3D makes a precision approach and in the future who is to know that the little circle (known as the bird) which you just point at the threshold and can be found on most synthetic vision systems might be just as precise as an ILS at allowing pilots to put the aircraft where they want it on the runway.
So the answer I was informed during these discussions to what makes a precision approach a precision approach comes down to the one line defintion “Any approach where the DH is 200ft or below”.
Not sure about some of the distinctions, if I take an ILS on neddle and its LPV GPS overlay where both have the same minima/design/specs, why one is precision and the other not precision?
I would have assumed any ILS with valid GS to be always called precision approach (not just a LOC apprach +DME or advisory slop), if yes, then its LPV GPS overlay should be as well, no?
AIP links go dead within a month. Unfortunately there is a large number of PDFs on that one and I don’t have time to localise them. I have the Jepp data but can’t post it here.
ILS 27
RNP 27
SkyWagon wrote:
unable to reach the charts of LFPB
Does this link work for you ?
Accessed from https://www.sia.aviation-civile.gouv.fr/documents/htmlshow?f=dvd/eAIP_02_JAN_2020/FRANCE/home.html
You are right, it is all about the design crietaria. By the way, unable to reach the charts of LFPB, may you please post it here? Or what is the minima :DA and RVR for RWY27?
SkyWagon wrote:
So ; Even though LPV approaches have vertical guidance, they’re not considered precision approaches. Instead, they’re an approach with vertical guidance (APV).
LPV can either be :
See ICAO annex 10 for more technical details.
When a LPV is a precision approach, the jeppesen minima box reads “LPV CAT I” (see LFPB RNP RWY 27 approach for example)
I think doc 4444 is not yet updated to reflect this change.
It only matters from a procedure design perspective.
