Airborne_Again wrote:
That means that you can’t accurately fly an RF leg using the standard DME arc technique of approximating the arc with a series of straight segments and manually resetting the HSI between each segment. You have to fly it as a continuous turn.
Thanks for the explanation, true it will be hard to approximate a tiny DME arc while flying straight lines, but you can always manage to be able to fly either inside or outside any tiny DME arc using the old way? that can be sufficient if the MDH is derived from all obstacles inside a small RF
Or you are just expected to fly accurately along that +/-1nm RF specific line and if you go to the center you are dead !
I can’t do the same reasoning on a direct line as you are equally left and right but for a small circle you have more chances to be outside 
Peter wrote:
is probably still going to be (like now) a “special crew authorisation” IAP only. Along with Lugano, the lower MDA one at Bolzano, etc.
I fought rather hard to make sure that approaches meeting the RNP APCH nav spec (including those that have RF legs as part of the procedure) do not require an operational approval (unlike RNP AR APCH which always do).
Ibra wrote:
Or you are just expected to fly accurately along that +/-1nm RF specific line and if you go to the center you are dead !
The whole point is that you stay on the line (within the allowed magin of error).
For which we are all grateful. No irony intended, just a honest “thank you for looking out for the GA crowd”.
Thank you for the sarcasm re disgruntled airlines.
No, this does not come from pilots but from airlines. And no, it is not a matter of GA envy.
Unlike (I suspect) those of you making snarky, sarcastic, uninformed comments, I actually sit in meetings where these things are discussed. There is considerable resistance from (mainly) smaller airlines to procedures being introduced for which their aircraft aren’t, and usually can never be, equipped. This is true of RNP in general (because their RNAV is not fault resilient) and RF legs in particular. Every RNP or RF leg procedure comes with a comment from those operating older aircraft saying that there must be conventional or RNAV alternatives which do not add track miles or time penalties.
It is just the same special pleading as we ourselves make. Mode S and 8.33 are examples. But maybe more saliently, when PBN was first proposed it was going to require autopilot (and possibly EHSI). This was successfully fought off by PPL/IR Europe. The airlines representative bodies are doing the same, for the same reasons, on RNP and RF legs.
Indeed, as I said before, you get this resistance whenever technology moves forward.
Other than the VABIK departure are there other RNP (not AR) procedures with RF legs in Europe?
Unlike (I suspect) those of you making snarky, sarcastic, uninformed comments
That is not justified, Timothy.
you get this resistance whenever technology moves forward.
I am delighted to hear that you will pay for my 5 digit avionics upgrade. My point is that this new complexity is pointless unless it delivers tangible benefits.
Whether the curved path does that in that Zurich SID
I can’t readily tell.
This was successfully fought off by PPL/IR Europe
Hmmm not quite, though they like to claim credit. I posted on this exact topic previously.
IJasonC wrote:
Other than the VABIK departure are there other RNP (not AR) procedures with RF legs in Europe?
I thought we found an IAP in SE France with an RF leg, but I can’t for the life of me find it now. I checked Colmar, and found a curve in the MAP but it clearly says “DF”.
In the UK, the EGSS CLN1E and DET4D SIDs require RF.
JasonC wrote:
RF legs allow for far more precise routes in an around terrain and airspace as the path of the arc is predictable. This can allow lower minima, fewer track miles needed etc. We might as well make use of the accuracy we now have with GPS.
Agree 100%. In my case, the standard approach is an ILS/DME with the FAF at 6000’ and over 9nm out. This is due to terrain. There are 2 new RNAV IAPs that use RF legs to bring the FAF in to just over 4nm and 3500’. This allows for a much more gradual curved descent from 6000’ (MVA) down to a closer FAF, avoiding the high terrain. My equipment isn’t yet approved to fly them, but I’m certain my simple Stec30 a/p with GPSS could track them effortlessly, without even the need for an EHSI.
Peter wrote:
And the original Q is: will Avidyne do it?
The Avidyne IFDs have the capability today, just like the Garmin GTNs, but not yet the certification. Apparently this needs flight testing with the FAA, and is not a high priority item for Avidyne because the largest market is Europe and their installed base here doesn’t justify making it a priority. It seems that RF leg implementations in the US are mostly tied to AR and therefore uninteresting to the GA crowd. This isn’t the case in Europe as the example here show. My personal guess is that Avidyne might have certification for RF legs by end-2020. They are currently working on major software release 10.3 and it won’t be included there.
