Yes. This is one the learning points in my PBN seminars. It can be very disconcerting for someone used to flying an SBAS box when they don’t see and APP annunciation until nearly at the FAF. I have seen people hovering over a go-around.
Aviathor wrote:
the non-WAAS units I believe switch from TERM to APPR mode 2 NM outside the FAF.
At least the GNS430 does.
Nobbi did give the correct answer a few posts earlier:
When within 45° of the final approach course and the FAF is the TO waypoint, the 500W-series unit switches from terminal mode to approach mode CDI scaling is tightened
I do not have the documentation at hand, but the non-WAAS units I believe switch from TERM to APPR mode 2 NM outside the FAF.
I don’t know the technical/specification/software answer, but it does make sense to me that a 2D final approach would not be activated inside the FAF.
Most people find it hard enough to be at exactly the right altitude at the FAF, to descend at the exact right RoD for the GS and check the altitudes at every mile without the added pressure of working out the correct descent point based on range from MAP. I can see that on a 3D approach it might be OK, provided your intercept is above TAA, so you can start a descent with the slope, staying above TAA until you have half scale deflection, and I guess that that would be OK even with LNAV+V, so I can see why the restriction might have been removed in SBAS boxes.
However, a little bit of pedantry. I don’t think it is helpful to use the expression “Activate the approach” which means a DCT to the IAF (Transition) in this context. I think that you should say “Activate the leg from FAF to MAP” or even “Activate the final approach leg” instead.
It is hard enough to beat into students’ head the idea of what “Activate the approach” means without the term being used loosely. Not getting at you personally, @boscomantico, lots of people add to this confusion.
Yes, but it was suggested by Timothy and NCYankee that even if you intercept the final inside the FAF, you could “save” things by activating the final approach leg, meaning that the approach would NOT suspend and that the sensitivity would indeed go to APR….
You will normally get a circle to land if they’re on 29, due to the interference with Kastrup as you mention. If you ask nicely, you can be allowed to fly the last bit of the 29 approach
@mmgreve, I realised that when the controller mentioned it while I was being vectored to final for rwy 29. But he accepted my request for the RNAV29 before giving me a direct to the FAF at give or take a 90° angle, which was not going to do it.
I suppose this is what you are referring to boscomantico?
During the vectoring, I did what was suggested here, i.e. highlight RWY27 waypoint, and then hit DCT DCT ENT. While this activated the leg from EPOMA to RWY27 alright, it did NOT activate the approach.
For the mode to change to APR you need to intercept the FAC outside the FAF.
Sorry if I repeat something that was mentioned before – but with my 530W I have to go via the FAF otherwise it won’t change to approach mode.
See this excerpt from FAQs in the Pilot’s Guide:
The unit begins a smooth CDI scale transition from the
2.0 NM (en route mode) to the 1.0 NM (terminal mode)
scale within 31 NM from the destination airport. When
within 45° of the final approach course and the FAF is
the TO waypoint, the 500W-series unit switches from ter-
minal mode to approach mode CDI scaling is tightened
from 1.0 NM full scale deflection to either 0.3 NM or 2°
full scale deflection whichever is less at the FAF. The scaling
change occurs gradually over a 2 NM distance and is
completed before crossing the FAF.
Coming back to my own question:
Or is there any way one CAN fly GPS approaches (i.e. get them activated) with an intercept INSIDE the FAF? Maybe with something more sophisticated than an almost 20 year old GNS430?
Today, I flew this RNAV approach again and asked ATC to vector me on an 8-mile final (a couple of miles inside the FAF, which is EPOMA). During the vectoring, I did what was suggested here, i.e. highlight RWY27 waypoint, and then hit DCT DCT ENT. While this activated the leg from EPOMA to RWY27 alright, it did NOT activate the approach. I immediately got the message that the approach was not active and sure enough, the mode didn’t change from TERM to APCH.
I had a little doubt if maybe it doesn’t work when one does this leg activation too soon, so I did it again when I was much closer to the intercept of the final approach course. I loaded the approach again and then activated the leg from EPOMA to RWY27. Same result. It doesn’t work.
