Peter wrote:
Same argument with MLS. It was a very ideologically pure concept.
MLS was killed by GPS and, by extension, by LPV. If neither had happened we would have got MLS, for sure.
Peter wrote:
The Lydd ILS is on the KLN94 but the DME arc is not shown. Only the localiser bearing line.
The same is true throughout the range. There is no overlay procedure. That’s my point.
Peter wrote:
Because there is no practical difference by the time a plane is flying that route, and it saved spending loads of money on avionics.
The RF Leg is part of the RNAV spec. You can’t just wish it away.
The RF Leg is part of the RNAV spec
That’s a circular argument.
Ever since GPS caused the bottom to fall out of the navigation business, millions of people have been looking for new paradigms to draw up standards for 
This is the world’s third oldest profession. The second oldest is flying VFR in IMC
Airborne_Again wrote:
They can’t be the reason for the RF leg in this case.
As mentioned, I strongly suspect this is to remain within Switzerland after takeoff northbound due to German airspace restrictions during certain times.
The RF Leg is part of the RNAV spec
That’s a circular argument.
I really don’t follow where you are coming from. Should there be no LPV approaches because some legacy boxes cannot fly them? Of course RF legs will be used, because they are an available Path Terminator in the toolbox. There is an argument that there should be alternative procedures for those with legacy equipment (which is why there are LNAV minima on LPV approaches) and that is the argument that some airlines are making, but the time will probably come when there will be a presumption of compliant equipment and airspace will be designed on that basis, with the benefits I mentioned above.
To argue that it is a job creation scheme in place to harass KLN owners is a bit far fetched.
To argue that it is a job creation scheme in place to harass KLN owners is a bit far fetched.
Who posted that?
Timothy wrote:
Isn’t that pug-ugly, wasteful and just annoying compared to a beautiful, smooth silky RF leg?
Totally agree but what RF leg are you suggesting? Presumably the route out to LCE13 at F100 is due some airspace restriction. If your RF leg is ELMIV to LCE13 then yes cosmetically better but no other benefit. If the RF leg is ELMIV to RAVSA taking in LCE13 then there will be more track miles and if the RF leg is ELMIV to RAVSA with a smaller radius it will require airspace changes which mean a direct from ELMIV to RAVSA will suffice.
I don’t think that the examples that you have given are very helpful in convincing people of the merits of RF legs. I am sure there are others which would be and I am not criticising the concept.
I am not advocating anything, just laying out how things are:
There are RF legs; procedure designers will use them; procedures with them will not be available to aircraft which don’t support them; there will probably be alternatives available for some time, but probably not for ever.
Airborne_Again wrote:
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.
The SID is RNAV 1. The minimum radius is the total primary (2 X RNAV RNP) and secondary obstacle protection (1 X RNAV RNP), which means the minimum radius for an RNAV 1 RF leg is 3 X 1 NM, or 3 NM. There is also a maximum bank angle allowed of 25 degrees, but 18 degrees is the normal. Any required bank angle above 18 degrees needs to be annotated on the chart. If required, the maximum speed the RF leg may be flown can also be limited to achieve a lower bank angle.
I am only aware of two approaches in the US that incorporate RF legs and they are separate charts to the same approach that uses different IAF that do not require the RF leg. If RF is required in an RNAV SID or STAR, RNP 1 is required rather than RNAV 1. I have RF approval on my GTN750 because it is connected to my G500TXi that has auto slew.
Timothy wrote:
There are RF legs; procedure designers will use them; procedures with them will not be available to aircraft which don’t support them; there will probably be alternatives available for some time, but probably not for ever.
This is what the FAA currently says in the Terps manual for RNAV:
Radius-to-Fix (RF) Turn. Incorporation of an RF segment may limit the number of aircraft served by the procedure.
RF legs are used to control the ground track of a turn where obstructions prevent the design of a FB or FO turn, or to accommodate other operational requirements.
