Prague LKPR has all its (six or so) ILS approaches out of action so they are using the VOR30 or the RNAV30, currently.
Interestingly most of the airliners were asking for the VOR30 
That is quite funny because if they are not equipped to fly a GPS/RNAV approach then they certainly aren't equipped to fly any LKPR STAR which are all PRNAV 
I asked for the RNAV30. A STAR was assigned as usual and I flew the first few waypoints of it and then got vectors.
I had never seen this before - all GPS/RNAV procedures flown previously were flown procedurally i.e. you load the procedure into the flight plan, then set a DTC to the IAF, and fly it. The GPS (KLN94) automatically increases the LNAV sensitivity from 5nm FS to 1nm FS (at 30nm to the airport) to 0.3nm FS (after the FAF).
In this case it was not at all obvious that the GPS would realise what one was doing, when flying a vector in more or less the opposite direction to the inbound track and nowhere near the IAF(s).
It did actually work in that it changed the inbound track to magenta when I was near to intercepting it, but I did change the scale manually to 0.3nm FS prior to the intercept, just in case.
What are the rules for making sure vectors to a (classic T-shaped) GPS approach will work?
If I was flying the VOR30 then I would have set the runway (the VOR actually) as a DCT, set the GPS to OBS mode, 0.3nm FS, course pointer to the inbound track, and intercepted the inbound using NAV mode.
Very much on a related note, yesterday I have flown an RNAV (GPS) approach in an aircraft equipped with... a KLN94. I was given vectors, but, not being used to this unit very much, I did not manage to active vectors-to-final. This cannot be a shortcoming of the KLN94, can it? On the GNS430 I normally have in my aircraft, when loading the approach, it offers the "vectors" option as soon as I am loading the approach and selecting the IAF. I have flown several vectored GPS approaches with the GNS430 in the past without any troubles. Not so with the KLN94. What am I missing?
Other than that, I don't see any problem with vectored GPS approaches. If it is properly loaded, there will be a magenta line extending from the FAF along the extended centreline. GPS will be in TERM mode and ATC will vector you on final. Then, when approaching the FAF, the GPS gradually changes to APR mode. Never had a problem - vectored or not.
What are the rules for making sure vectors to a (classic T-shaped) GPS approach will work?
I am not presently aware of any rules (could look it up though) but every approach capable GPS/FMS I have come across so far is smart enough to "see" when you are being vectored onto the connecting line between two waypoints and will intercept accordingly. On our Honeywell FMS/autopilot/flight director for example you fly your intercept vector in HDG mode and press LNAV when cleared to intercept. "HDG" will then be displayed in green in the PFD and "LNAV" in white (which means "armed") and it will automatically engage upon intercept.
On Garmin units (GNS 430/530) you press "PROC->Activate Vector To Final" when cleared to intercept and it will do the same thing as described above.
I had never seen this before - all GPS/RNAV procedures flown previously were flown procedurally...
Here in Germany I rarely have to fly approaches procedurally. We often fly GPS approaches (sometimes several times per week) into EDTY, EDVE, ETSI and EDAB and I would estimate that 90 percent are flown by vectors to the final course. Only at EDAB we usually fly the procedure but only because we approach from the west where it starts anyway.
Here in the US, there are restrictions on vectors to final for a RNAV approach. Unlike an ILS, the vector must intercept the final approach course at least three miles from the FAF and at an angle not to exceed 30 degrees. This is to permit the GPS to cycle the CDI sensitivity from terminal to approach and to adjust the required integrity settings.
Using the VTF function in the GPS is frowned upon by instrument instructors as ATC is permitted to send the aircraft direct to an IF or step down fix between the IF and FAF. These are not directly selectable thru the approach dialog and the full procedure needs to be loaded and then the pilot needs to scan thru the resulting flightplan to select the IF or step-down fix and then do a direct-to the fix. Controllers here have the nasty habit of telling the pilot they will be vectored to the approach or vectors to final (a bold faced lie that they never intend to do) and then at the last moment, clear the aircraft direct to a fix. This can cause confusion at a critical time, particularly if the pilot has previously selected VTF in anticipation of the vector to final. When VTF is used, it eliminates all the approach fixes other than the FAF and MAP on the final approach segment, so the pilot can't comply with the controller instruction direct to a fix without reprogramming the approach from scratch. Throw in the fact that the IF won't be part of the approach dialog and big time confusion can result. There is at least one fatal accident in a Cirrus that this was a contributing factor.
Controllers don't know the problem they create by indicating that the aircraft will be vectored to final when in fact they intend to vector the aircraft to a position where they will then clear the aircraft direct to a fix to join the approach. Direct to a fix, even if it is on the final approach path is not a vector and it requires programming of the GPS/FMS. I have been pushing this point at meetings with controllers and pilots at the FAA Air Traffic Procedures Advisory Committee.
Peter, your GPS doesn't have a VTF mode? As said above on the Garmins this is straightforward.
It was quite funny yesterday as many airliners turned down an RNAV approach on 07 in Stuttgart (ILS 07 was unserviceable). A Turkish 737 elected to do an opposite ILS with 15kt tailwind as the controller declined a visual approach to 07.
With all AOC operations it seems to be more about the procedures in the ops manual than it is the equipment in the aircraft or the wishes of the crew.
With all AOC operations it seems to be more about the procedures in the ops manual than it is the equipment in the aircraft or the wishes of the crew.
Yes, unfortunately. Or fortunately? You can't get much wrong flying an ILS approach, but quite a lot on a GPS or visual approach (see that triple seven at San Francisco)...
There can be a number of reasons why some carriers refuse to fly the GPS approach into 07 at Stuttgart:
They are simply not equipped for it. Either no GPS sensor at all, or the procedure is not included in their database. Or their set of charts doee not include that one. Most carriers do not have a full Jeppesen or Lido or whatever set of charts, but just a selection of charts prepared specially for them with their destination and alternate aerodromes.
The crew is not current to fly this kind of approach. Like the well known 90-day rule that applies for any pilot regarding landings, (some) commercial operators require so and so many approaches of a certain kind within so and so many days in order to fly them with passengers. Shouldn't be an issue here as ILS 07 has been on maintenance for more than two months already and will continue to be inop until sometime in September (has been NOTAMed for quite some time...). The carriers by now should be able to either train their crews or operate the flights with crews that are current.
The authority of their home country or their own procedures do not allow stand-alone GPS approaches, but only overlays. I know that this has been an issue in the UK for a long time. So much, that our English training organisation at Farnborough, where we do our yearly recurrent training, refuses to let us fly standalone FMS approaches on their simulators. Even if our authority and our operation would allow them...
The KLN94 does have a Vectors to Final option but it didn't display it on LKPR 30.
It does seem to work OK with a bit of hacking but one would not want to be messing with this in a high workload situation.
Yes, unfortunately. Or fortunately? You can't get much wrong flying an ILS approach, but quite a lot on a GPS or visual approach (see that triple seven at San Francisco)...
Visual of course, but why with a GPS approach? Procedurally (for those with vertical guidance) they don't differ very much from flying an ILS. The biggest challenge I have seen is transitioning to leg mode from a direct to waypoint so the approach will arm. Otherwise you fly it exactly like an ILS.
But with the Avidyne I saw plenty of ILS issues as well ie getting stuck in Back Course mode if you arm APR too early on a procedural where the inbound course is behind you.
EDIT: And in all glass cockpit ops I find the biggest opportunity for approach problems is in Auto mode changes/CDI selection/slewing.
