Airborne_Again wrote:
Interesting. This is 1% steeper than the normal maximum gradient according to PANS-OPS. When that happens PANS-OPS states that minima should be no lower than circling minima which is also the case for CAT A and B, but not CAT C or D. I’m surprised that Austrian authorities don’t require a special authorisation to fly this approach.
I don’t think special authorization is required just because the PANS-OPS max gradient is exceeded. Both St Gallen LSZR and Bern LSZB have 4° gradients with minima below circling minima (360’ below circling minima for St Gallen). Neither require special authorization. Both do have 500’ DH/MDH though…. not sure if that comes into play with allowable gradient.
chflyer wrote:
Both do have 500’ DH/MDH though…. not sure if that comes into play with allowable gradient.
My understanding all Switzerland runways except two are non-instrument runways according to their physical data (e.g. width vs length), they can still have instrument procedures like ILS, LOC, VOR, RNP…but these have to get floored with flat 500ft OCH when it’s a straigh-in and it’s not an INST RWY (NIR): it’s unlikely you will ever find an approach plates with OCH less than 500ft in Switzerland, unless it’s on special authorization for aeroplanes or helicopters
Only Geneva & Zurich have runways that comply with instrument runway as per ICAO Annex 14
@Airborne_Again wrote:
Interesting. This is 1% steeper than the normal maximum gradient according to PANS-OPS. When that happens PANS-OPS states that minima should be no lower than circling minima which is also the case for CAT A and B, but not CAT C or D. I’m surprised that Austrian authorities don’t require a special authorisation to fly this approach.Anyway, back to topic. You do get +V for this approach as well on a Garmin GTN650Xi.
Added note: my surprise above should not be taken to mean that I feel that the approach should require special authorisation. At least not for CAT A.
Authority reply
„As a matter of fact, the circling minimum must never be lower than the straight-in instrument minimum. This ensures that the pilot can get from the IFR approach to circling without there being a “gap”.
The higher circling minimum also often results from the fact that the protective space for the obstacle calculation is different and the vertical clearance from obstacles is also calculated differently.
Even so, the circling minimum may be arithmetically lower than the straight-in minimum, but even then we would not be allowed to publish a value for it that is lower than the straight-in minimum.“
Interesting, but IMHO pretty obvious 
On the topic, sort of, is there any difference between Garmin GTN and Avidyne IFD, in this area?
Snoopy wrote:
„As a matter of fact, the circling minimum must never be lower than the straight-in instrument minimum. This ensures that the pilot can get from the IFR approach to circling without there being a “gap”.The higher circling minimum also often results from the fact that the protective space for the obstacle calculation is different and the vertical clearance from obstacles is also calculated differently.
Even so, the circling minimum may be arithmetically lower than the straight-in minimum, but even then we would not be allowed to publish a value for it that is lower than the straight-in minimum.“
Well, yes. But this only refers to the minima calculation for “normal” approaches. It doesn’t explain why the C/D straight in minima are not the same as the circling minima, like PANS-OPS says they should be for “oversteep” approaches.
As a matter of fact, the circling minimum must never be lower than the straight-in instrument minimum. This ensures that the pilot can get from the IFR approach to circling without there being “gap”
It’s obvious on NPA and CTL but I doubt there is a rule about this in PANS-OPS? it’s like saying LNAV can’t have minima lower than LPV, it may seem obvious but surely not true
I guess they mean you can’t have gap between NPA and CTL? that is probably true at least in TERPS, it explicitly states you need a published NPA minima to build CTL minima on top of it but apparently this is not the case for PANS-OPS, see here:NPA-CTL
It’s a very interesting question if this is guarantee, then you can safely descend to straight-in minima then climb to circling minima before MAPT and circle on opposite runway: saves you from going missed with high ceiling and low visibility where you usually have ground in-sight but not the runway in sight, something UK ANO used to explicitly allow while US FAR explicitly ban !
On 3D APV and CTL, you can still have “-4ft gap”, say between 3D L/VNAV and 2D CTL for EISG this seems to happen with funky geometries where obstacles penetrate 3D glide path near it’s kink on short final and blows up MOC for 3D APV while obstacles don’t penetrate 2D surface (2D NPA and 2D CTL), this usually means 2D straight-in non-precession and 2D circling could have lower minima than straight-in 3D !
https://www.ifr-magazine.com/technique/obstacle-clearance/
@ibra many of your links to forum posts are dead; you have to right-click here
and get the link to the actual post. Any link with a page# will be dud because everybody has a different page length set up in their profile.
Please also, rather than posting the URLs, make them clickable links with a short name.
It’s all in the Posting Tips, and in the IT/Website section.
@arj1 many thanks. I think enroute VNAV is not a big thing, in a piston aircraft – because they are so underpowered anyway
Any link with a page# will be dud
Done, sorted 
