AdamFrisch wrote:
Here in the US it happens quite a bit over busy airspace. Went to Napa over xmas and they always keep you very high above San Francisco for all the airline traffic going into SFO and Oakland. Sure enough, I was at 10000ft and a steep intercept heading as they flew me over the city and gave me a slam dunk into Napa. Thankfully it was VMC, so as I became visual with airport, I could be a bit more aggressive.
Adam,
What US ATC can do vectoring an aircraft in visual conditions (at least 3 mile visibility and ceiling 500 feet higher than MVA/MIA) is different than what they can do when conditions are lower, where they are required to intercept the FAC effectively 3 NM outside the FAF. ATC is not permitted to intercept the GS from above nor below the charted GS intercept altitude on an ILS. Non precision approaches including RNAV (GPS) with an LPV minimum, ATC does not need to consider the GS and only is instructed to vector the aircraft “at an altitude which will allow descent in accordance with the published procedure.”
Pilot’s may request vectors to the FAF on an ILS, but controllers can’t initiate this regardless of conditions. The conditions are not relevant to RNAV approaches, as ATC is required to intercept the FAC two NM outside the gate or 3 NM from the FAF.
I have on a few occasions insisted on a redo, once when on an RNAV (GPS) approach which had a 20 degree turn at the FAF, the controller had me 1000 feet above the crossing height for the FAF, and cleared me for the approach on a vector for final, but to the extended final approach course and not to the charted intermediate leg. I never accepted the clearance and declared a missed approach.
How do the higher-end operators (e.g. Collins Proline and above) handle the “vector to the FAC” scenario? If they didn’t, ATC would soon find out that they should not do it. There are a few people here familiar with these systems. How do they do it?
I have usually found these presentations near-useless because there is such a variation in equipment buttonology out there, and anyway GPS approaches are normally flown via an IAF. Also most pilots flying with e.g. a GNS box don’t understand these subtle points. I don’t understand the subtle points of my KLN94 which is why I adopt the standard procedure every time.
The other way to do all this, in cases where the ARP is in the centre of the runway, is to set a DCT to the airport and fly the approach in the OBS mode 
Crude, but you can fly it with a vector to anywhere…
I asked a bizjet pilot and got this
With the Proline, I’d be in heading mode, arm the approach and if we’re pointing at the final approach track, it will intercept it.
The Proline will intercept at whatever angle you point yourself at it. Treats it just like a localiser.
The Universal FMS does a similar thing. You need to have the aircraft in FMS mode and you set the intercept heading on the FMS
So why can’t the GA boxes work like that?
To add:
If you get vectored inside the FAF, it will still capture like a localiser – but you’ll be too high. It won’t descend on its own unless it captures a VGP (Virtual Glide Path). You would need to descend to capture it.
Before I can try that the next days, maybe you have personal experience with the GNS430W. Bosco already said that most pilots don’t differentiate correctly between the Autopilot and the Navigator. But since the Flight Director is a feature of the Autopilot (in my case the DFC90, which also intercepts from above) and since all that stuff is so much integrated, it’s hard to understand it all.
I do understand that the 430/W will not switch correctly to Approach sensitivity. But the approach is still loaded and the sequencing works, right? The last time MY system did not intercept he approach correctly because I accepted a DCT to the FAP I switched off the A/P and intercepted the Final Track and GS with the FD. Why does it not work “coupled” but does work okay with the “FD”?
Alexis,
If you don’t understand DCT DCT ENT I suggest downloading the 430W sim. It’s free and easy.
You are misinformed about the sensitivity when the FAT is activated on the 430W, but I have already said how it works so many times on this thread that there seems no point in typing it out again.
A little patience, ok?
I would have tried it on the simulator, but there is no 430 or 430W simulator for the Mac.
boscomantico wrote:
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?
This is easy to do on a GNS430 or GNS430W. Just tap the FPL button, move the cursor to the runway waypoint (RWY27) tap direct-to direct-to enter. This will activate the leg EPOMA to RWY27 and for a W will give you a GS and for the lateral it will indicate LNAV+V.
I use this technique all the time when flying a visual approach as most end up being initiated inside the FAF.
Peter wrote:
I have usually found these presentations near-useless because there is such a variation in equipment buttonology out there
I suspect that was exactly the point of this slide; to show that this stuff is not obvious and you need to know exactly how it works in your aircraft.
Peter wrote:
and anyway GPS approaches are normally flown via an IAF.
The fact that its rare is IMO a reason to train/deliberately practice it more often. We all know how to fly the common cases, it’s the unusual ones which we (and I include myself there!) screw up.
Personally, I think it’s important to understand all the quirks in these devices. I really hate that “what’s it doing now” feeling. I also have SOPs for the common cases.
I might add: You do not have to use the IAF … you can accept a DCT to any of the WPs BEFORE the FAF and everything should work fine.
This is easy to do on a GNS430 or GNS430W. Just tap the FPL button, move the cursor to the runway waypoint (RWY27) tap direct-to direct-to enter. This will activate the leg EPOMA to RWY27 and for a W will give you a GS and for the lateral it will indicate LNAV+V.
Thanks NCY; Timothy explained this as well. Still, I don’t know whether this will change the CDI sensivity momentarily, or gradually.
In any case, I have to say sorry for blaming the radar controller in post 08. It transpires that his question made some sense and wasn’t entitely “wrong”.
