It may be a different thread, but it is remarkable how much less well equipped many airliners are compared to ourselves. I talk to pilots of still very active aircraft, like 737s and the like, and am surprised at the lack of precision of RNAV, for example. RNAV on such aircraft is typically INS with DME/DME support, which is never going to come close to SBAS supported GNSS (though probably somewhat more reliable.)
And some regional turboprops are flying basically the same equipment I was flying in the 80s and 90s.
Timothy wrote:
which is causing a certain amount of disgruntlement in some airlines
Why would airlines be disgruntled that there are IAPs that they can’t fly because they won’t spend the $$$ to get the required equipment? Or are they suddenly jealous that lowly GA pilots now have equipment that they don’t, and that gives us a perceived “advantage”? Sounds like a common airline attitude that they dictate authorities’ plans and priorities.
Or is it the airline pilots that are disgruntled? In which case, I’d be tempted to say “aw shucks, poor airline pilots”.
chflyer wrote:
Why would airlines be disgruntled that there are IAPs that they can’t fly because they won’t spend the $$$ to get the required equipment?
They are not “disgruntled” because…
chflyer wrote:
Or are they suddenly jealous that lowly GA pilots now have equipment that they don’t, and that gives us a perceived “advantage”?
…“they” don’t even know GA exists and couldn’t care less. A little bit like a tiny dog barking up a huge one who isn’t noticing. Why should an airline be “jealous” that I can have a GTN750 with an EHSI and RF legs in my small private prop?
chflyer wrote:
Or is it the airline pilots that are disgruntled?
You’re on to something there. Haven’t heard any other topic being discussed during cruise for a long time. “Hey John, what’s the newest RF gossip out there?” (Sarcasm)
To add something of value to this topic: RF simply means the curved line between two points is predetermined and the airplane will fly it as depicted, unrelated to TAS/GS, right?
Following Snoopy question, for those less informed, I guess a RFs mimic a DME arc as do LPVs overlay an ILS ? Why do you need an EHSI to fly a DME arc?
Then for RNAV do you apply a “curve factor” or you just keep those 1nm/5nm performance standards from straight lines?
Ibra wrote:
Following Snoopy question, for those less informed, I guess a RFs mimic a DME arc as do LPVs overlay an ILS ? Why do you need an EHSI to fly a DME arc?
The difference is that the radius of an RF is much smaller than that of a DME arc. The minimum DME arc radius according to PANS-OPS is 7 NM. An RF usually has a much smaller radius — e.g. the RF arc in the Zürich SID at the beginning of this thread has a 2.1 NM radius. Also, like the Zürich SID, RF legs are typically RNP/RNAV 1.
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.
the RF arc in the Zürich SID at the beginning of this thread has a 2.1 NM radius
That is why I asked whether these RF arcs are put in “just for fun, because they are there” or whether they can serve a meaningful obstacle clearance function. They come at a high cost: a lot of planes can’t fly them, and even in the light GA context you could be looking at 5 figures to get the capability. Some people (with the appropriate flying profile) might pay that to get LPV, but for RF legs??
manually resetting the HSI between each segment.
A DME arc is most likely flown in HDG mode and by turning the heading bug every so often while watching the DME. The DME GS readout (which is zero when you are spot on) is also a dead giveaway… You don’t need an HSI.
Stepping back a bit, what is “interesting” in all this is that while an old box like a KLN94 does perfectly well for flying IFR in the Eurocontrol system, with the main problem being lack of LPV, this kind of thing might actually finish it off completely one day – IF it becomes widespread. Hopefully the stink kicked up by airlines will ensure it doesn’t happen too fast.
Snoopy wrote:
To add something of value to this topic: RF simply means the curved line between two points is predetermined and the airplane will fly it as depicted, unrelated to TAS/GS, right?
Yes although there is a speed limit to ensure it can be done with a normal angle of bank.
Peter wrote:
That is why I asked whether these RF arcs are put in “just for fun, because they are there” or whether they can serve a meaningful obstacle clearance function. They come at a high cost: a lot of planes can’t fly them, and even in the light GA context you could be looking at 5 figures to get the capability. Some people (with the appropriate flying profile) might pay that to get LPV, but for RF legs??
Obviously no one will pay to get RF per se but most modern GPS systems can do it. Along with LPV, there are a variety of capabilities coming that older navigators won’t be able to take advantage of.
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. Somewhere like Sion with an approach using RF would allow lower minima.
Indeed, though
Somewhere like Sion with an approach using RF would allow lower minima.
is probably still going to be (like now) a “special crew authorisation” IAP only. Along with Lugano, the lower MDA one at Bolzano, etc.
And the original Q is: will Avidyne do it?
Peter wrote:
That is why I asked whether these RF arcs are put in “just for fun, because they are there” or whether they can serve a meaningful obstacle clearance function.
In the Zürich case, I’m believe they do. Assuming that you want the aircraft to follow the nominal track of the SID, I’m pretty sure the area that has to be checked for obstacle clearance would be much larger with, say, a flyby waypoint placed “outside” of the turn arc. I don’t know the obstacle situation around Zürich, but it appears the departure is towards higher ground.
There could also be airspace reasons for wanting a more precise flight path.
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.
Not necessarily. It could be a compromise between the AR approaches and the much higher normal ones. This is an evolutionary process.
