The advisory glideslope can be flown only down to the decision height, no lower.
When you reach the DH you must go around.
But what you have done is exchanged the better chance of achieving a “visual” (and thus a landing) for an easier and more stabilised flight path.
One could argue that if you flew that glideslope 1000ft above every SDF, it would be even safer 
Which is of course true, but you will have an even smaller chance of getting visual.
Obviously I know why a CDFA is preferred by many, but that isn’t how the nonprecision procedure was designed. It was designed to achieve the TERPS/PAN-OPS obstacle clearance when flown down to each SDF, with the (usual) level flight at the end, and then going around at the MAP.
What many don’t know is that if flying a CDFA you are not flying an ILS or LPV (which was designed to take you obstacle-clear all the way to the tarmac). You are flying a line which sits above some SDFs and you are still required to check off each SDF on the way down.
Peter wrote:
One could argue that if you flew that glideslope 1000ft above every SDF, it would be even safer
No, it wouldn’t because you would have to do a dive bomb approach at the end to make the runway.
What many don’t know is that if flying a CDFA you are not flying an ILS or LPVI am sure everyone who is flying a CDFA is very much aware of that. For one thing, there is no glideslope indication!
The problem is rather that many don’t have the slightest idea what a CDFA is. It is not in the IR – or even ATPL – TK (or at least was not two years ago) and many IR instructions have no clue.
I am sure everyone who is flying a CDFA is very much aware of that. For one thing, there is no glideslope indication!
There is with a “W” GPS, for approaches which have the advisory glideslope enabled in the Jepp database. You can couple an autopilot to it too.
They are mostly enabled in the database, with some exceptions (discussed here a lot in the past) where a “higher grade” baro-VNAV approach was drafted and that suppressed the advisory glideslope one, which was bad for light GA none of which can get baro-VNAV. I am not sure whether this situation still persists. I read that Garmin were going to fix it.
So, you can fly a SDF approach like this
just like an ILS, with an autopilot. The difference is that you must go around at 800ft altitude, otherwise you might hit something, and at some (very few) airports you will. Whereas with an ILS or LPV, you “could” fly the GS all the way to the runway.
You have to figure the (M)DA/H yourself. And then this “useless” information is pretty handy.
The ICAO-minimum minima figures for different approach types are mostly academic and are not related to the OCA to MDA conversion process. The conversion involves stuff like the grade of runway lighting.
Peter wrote:
The ICAO-minimum minima figures for different approach types are mostly academic and are not related to the OCA to MDA conversion process. The conversion involves stuff like the grade of runway lighting.
No, it doesn’t, but the visibility requirements do.
Depending on existing national regulations, IFR approaches to unmanned airports (no open ATC or AFIS) can be illegal. I know it is legal in the UK and France, but what about other European countries? Also, AFAIK, every European country except the UK require you to use officially approved IFR procedures.
This situation appears to change with part-NCO. In particular this paragraph:
NCO.OP.115 Departure and approach procedures – aeroplanes and helicopters
(a) The pilot-in-command shall use the departure and approach procedures established by the State of the aerodrome, if such procedures have been published for the runway or FATO to be used
strongly suggests that you can use a DIY approach if none is published for the airport.
Also, the complete absence in part-NCO of any mention of requirements to use ATS as there are in part-CAT, e.g.:
CAT.OP.MPA.107 Adequate aerodrome
The operator shall consider an aerodrome as adequate if, at the expected time of use, the aerodrome is available and equipped with necessary ancillary services such as air traffic services (ATS), sufficient lighting, communications, weather reporting, navigation aids and emergency services
strongly suggests that ATS is not required for any phase of any flight according to NCO, VFR or IFR – except when mandated by other regulations, such as SERA, of course.
This can potentially mean a huge difference in the availability of smaller airports to private IFR.
Have you folks any idea what the view of your national CAA is on this?
I (and some other people) have talked to the Swedish CAA about it and while they don’t say that they agree, they do say that they can’t argue against this line of reasoning. (They also say that they will not publish any interpretations or guidelines before part-NCO comes into force.)
It’s informative to compare the equivalent wording in CAT, NCC and NCO:
CAT.OP.MPA.125 Instrument departure and approach procedures
(a) The operator shall ensure that instrument departure and approach procedures established by the State of the aerodrome are used.
(b) Notwithstanding (a), the commander may accept an ATC clearance to deviate from a published departure or arrival route, provided obstacle clearance criteria are observed and full account is taken of the operating conditions. In any case, the final approach shall be flown visually or in accordance with the established instrument approach procedures.
(c) Notwithstanding (a), the operator may use procedures other than those referred to in (a) provided they have been approved by the State in which the aerodrome is located and are specified in the operations manual.
NCC.OP.115 Departure and approach procedures
(a) The pilot-in-command shall use the departure and approach procedures established by the State of the aerodrome, if such procedures have been published for the runway or FATO to be used.
(b) Notwithstanding (a), the pilot-in-command shall only accept an ATC clearance to deviate from a published procedure:
(1) provided that obstacle clearance criteria are observed and full account is taken of the operating conditions; or
(2) when being radar-vectored by an ATC unit.
(c) In any case, the final approach segment shall be flown visually or in accordance with the published approach procedures.
NCO.OP.115 Departure and approach procedures — aeroplanes and helicopters
(a) The pilot-in-command shall use the departure and approach procedures established by the State of the aerodrome, if such procedures have been published for the runway or FATO to be used.
(b) The pilot-in-command may deviate from a published departure route, arrival route or approach procedure:
(1) provided obstacle clearance criteria can be observed, full account is taken of the operating conditions and any ATC clearance is adhered to; or
(2) when being radar-vectored by an ATC unit
I should probably fess up to having drafted NCO.OP.115, having seen what the implications of the original proposal (based on CAT.OP.MPA.125) would be. I have no idea what was going through EASA’s minds when they published the opinion, nor the EASA Committee’s when they approved it, but my thinking was to avoid an overly constraining rule that forces scud running when the economies of scale to justify an official IAP are not there.
bookworm wrote:
I should probably fess up to having drafted NCO.OP.115, having seen what the implications of the original proposal (based on CAT.OP.MPA.125) would be.Aha! So if the author of the rule (you) thought along the same lines as I did, that should be a strong case for that interpretation.
Time to start drafting an approach for my club airfield.
I have no idea what was going through EASA’s minds when they published the opinion, nor the EASA Committee’s when they approved it, but my thinking was to avoid an overly constraining rule that forces scud running when the economies of scale to justify an official IAP are not there.
Tread gently with the Swedish CAA though.
Regardless of the legalities, it is a significant safety advantage to have a trajectory that:
bookworm wrote:
Regardless of the legalities, it is a significant safety advantage to have a trajectory that: [snip]
I’m very much aware of that. The obstacle situation around our airfield is good and we’re are not going to do anything complicated or with minima lower than VFR minima. (And I have copies of PANS-OPS on my computer. )
I drew a GPS approach to the small field in CZ next to my company, and I programmed all the points for it into my 430W and flew it on autopilot in VMC. Using the “300 ft per 1 NM” method I set up the descent, checked the altitude every mile. I did it five times in VMC and it always worked perfectly. No obstacles except a chimney half a mile sout which i could see on the MFD’s active VFR approach chart.
I still wouldn’t do it in IMC … But i know more than one pilot who does stuff like that. I guess it would be completely safe down to, let’s say, 500 ft AGL (and I have the EGPWS too that would announce “500”.)
How different could the QNH of 30 miles away LKPR airport be in theory, anybody know? 1 hpa?
