interesting RNAV(GPS) approach

olasek

olasek

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olasek
I find this approach fascinating. This approach has a curved built in but it isn't a DME arc nor it is an RNP (where such curves are very common). So this one could be for us lowly GA pilots with a certified GPS equipment to fly. I wonder if there are more examples like that anywhere else.

http://155.178.201.160/d-tpp/1411/05310RX24.PDF
 
olasek said:
I find this approach fascinating. This approach has a curved built in but it isn't a DME arc nor it is an RNP (where such curves are very common). So this one could be for us lowly GA pilots with a certified GPS equipment to fly. I wonder if there are more examples like that anywhere else.

http://155.178.201.160/d-tpp/1411/05310RX24.PDF
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I think this one's been discussed here (or on the red board) already. In short, you can't fly the curved portion. Might have something to do with the "RF Required" note.
 
RF (radius to fix) is required - see the notes box. RF is in the specifications for RNAV systems, but AFAIK none of the common GPS receivers are equipped to fly it. Unfortunately, this means that for now, this approach is unflyable by most GA, unless you receive vectors to final. Would be interesting to see if the approach is even in the databases.
 
I stole this post from John Collins on another forum. Hopefully he'll be along soon...:)

The approaches to Medford that use the RF legs RNAV (RNP) RWY 32 and RNAV (RNP) Z RWY 14 are not standard GPS approaches and require special pilot authorization. They are not allowed to be flown by FAA Part 91 users and they are not included in the popular GPS unit databases. The RF (Radius to Fix) leg is a curved path between two waypoints, where the center point of the radius is off to the inside of the turn and equidistant from all points on the path. The RF leg type is considered an advanced capability and can be used in RNAV (RNP) or RNAV (GPS) approaches. The current GPS manufacturers do not support this type of advanced feature and do not permit any approach which uses them to be included in the database. The first RNAV (GPS) approach that includes a RF leg will be published this month at KCRQ RNAV Y eff 26 JUL, but it won’t be able to be flown.
Click to expand...
 
RussR said:
RF (radius to fix) is required - see the notes box. RF is in the specifications for RNAV systems, but AFAIK none of the common GPS receivers are equipped to fly it. Unfortunately, this means that for now, this approach is unflyable by most GA, unless you receive vectors to final. Would be interesting to see if the approach is even in the databases.
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Definitely not in the database. The only system that is approved for RF legs is the G1000 STC retrofit for the King Air.
 
You can fly the "Y" version of the approach, which basically has the same minimums, but starts farther and higher to the east.
 
Brad Z said:
This is the RMN ILS 33 approach. Its been around for more than 10 years, and has a similar dead rec curved segment for a course reversal. I've always treated it like an arc when done without GPS.

http://155.178.201.160/d-tpp/1411/09743IL33.PDF
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That's simply a teardrop-style course reversal or "penetration turn", not related at all to the RF turn in the OP, flown differently, and uses much different obstacle evaluation areas.

An RF turn is not a dead reckoning turn at all. An approved GPS (of which there are currently none) would show you positive course guidance all the way through the curved path.
 
Brad Z said:
This is the RMN ILS 33 approach. Its been around for more than 10 years, and has a similar dead rec curved segment for a course reversal. I've always treated it like an arc when done without GPS.

http://155.178.201.160/d-tpp/1411/09743IL33.PDF
Click to expand...

That's a tear-drop procedure turn, not an RF leg. Tear-drop procedure turns, although uncommon on civil IAPs, have been in Chapter 2 of TERPS for eons.
 
John Collins said:
Definitely not in the database. The only system that is approved for RF legs is the G1000 STC retrofit for the King Air.
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Approved, perhaps, but to my knowledge, not authorized. The RNAV X should not be in that database.
 
RussR said:
RF (radius to fix) is required - see the notes box. RF is in the specifications for RNAV systems, but AFAIK none of the common GPS receivers are equipped to fly it. Unfortunately, this means that for now, this approach is unflyable by most GA, unless you receive vectors to final. Would be interesting to see if the approach is even in the databases.
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That raises an interesting question: Why don't common GPS receivers have this? It's not like it's a super-complicated thing to figure out.
 
JeffDG said:
That raises an interesting question: Why don't common GPS receivers have this? It's not like it's a super-complicated thing to figure out.
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Because the FAA department responsible for this cannot make up their collective mind as to what equipment will be required (map display, auto-pilot, etc.)

Garmin did an exhaustive test a couple of years ago that included pilots of varying experience, including an FAA FSDO inspector. No one had any problem flying them.

For regular RNAV procedures the radius of the RF leg cannot be less than 3 miles because of the geometry of the criteria.
 
RussR said:
That's simply a teardrop-style course reversal or "penetration turn", not related at all to the RF turn in the OP, flown differently, and uses much different obstacle evaluation areas.

An RF turn is not a dead reckoning turn at all. An approved GPS (of which there are currently none) would show you positive course guidance all the way through the curved path.
Click to expand...

aterpster said:
That's a tear-drop procedure turn, not an RF leg. Tear-drop procedure turns, although uncommon on civil IAPs, have been in Chapter 2 of TERPS for eons.
Click to expand...

My apologies for leaving the word "albeit" between 'similar' and 'dead' in my original post. While the ILS in my example uses dead reckoning as part of a course reversal, and the OP's example uses radius-to-fix, their purpose of the designs are similar: to allow operators to transition from a near airway fix (in the OP's case, VISTA, in my example BRV VOR) onto the approach centerline. While not an RNAV approach with RF turns, it's still an interesting approach, IMHO, and one that we have the capability to actually fly. Bonus challenge points if you fly it as a Localizer approach with ADF instead of DME.
 
Brad Z said:
My apologies for leaving the word "albeit" between 'similar' and 'dead' in my original post. While the ILS in my example uses dead reckoning as part of a course reversal, and the OP's example uses radius-to-fix, their purpose of the designs are similar: to allow operators to transition from a near airway fix (in the OP's case, VISTA, in my example BRV VOR) onto the approach centerline. While not an RNAV approach with RF turns, it's still an interesting approach, IMHO, and one that we have the capability to actually fly. Bonus challenge points if you fly it as a Localizer approach with ADF instead of DME.
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The reason for the RF leg at KCRQ, RNAV X Rwy 24 was to get a transition from OCN yet remaining clear of R-2503. There isn't enough room to do this with conventional (TF) legs using today's more restrictive criteria. Thus, the TF leg from OCN to VISTA, followed by an RF leg. Unfortunately, the FAA designer didn't stop to consider that at present only aircraft approved for RNP AR operations are permitted by the FAA to fly RF legs.

AFS-400 then got involved and directed that the RNAV procedure be split into the Y and X versions. The decision was made to keep the RF leg in the X version because there are a fair number of biz jets based at KCRQ that are authorized RNP AR.
 
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