Curved approach path

coloradobluesky

coloradobluesky

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coloradobluesky
I was talking to a friend of mine that is a pilot with a major, you know flies the big jets. And I asked him if GPS approaches where helping him. He said yes, especially the curved approach paths. I've never seen a curved approach.

Anyone have any examples of a chart with curved approach path?
 
coloradobluesky said:
I was talking to a friend of mine that is a pilot with a major, you know flies the big jets. And I asked him if GPS approaches where helping him. He said yes, especially the curved approach paths. I've never seen a curved approach.

Anyone have any examples of a chart with curved approach path?
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Take a look at some RNAV (RNP) approaches. PSP has some good examples, like the RNAV (RNP) Y RWY 13R
 
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coloradobluesky said:
I was talking to a friend of mine that is a pilot with a major, you know flies the big jets. And I asked him if GPS approaches where helping him. He said yes, especially the curved approach paths. I've never seen a curved approach.

Anyone have any examples of a chart with curved approach path?
Click to expand...

Try KJAC GPS Zulu....
 
At KPSP RNAV 13R, what does the RNP 0.17 DA mean next to the 277 DH (or is an MDA?). And what does "AUTHORIZATION REQUIRED" mean?
 
Ron Levy said:
That one:
http://155.178.201.160/d-tpp/1404/00504RZ19.PDF
...does not have any arcs in the path, just several short straight segments. John Collins can correct me if I'm wrong, but I believe only RNAV(RNP) approaches can have those curved paths, not RNAV(GPS).
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We consider it an arc...... if it is flown smoothly....

Or you can use the RNAV runway 1 into here...

Ps.. I cannot confirm any on this as all the links I click on today come up with a 404 error..
 
RNAV (GPS) approaches can use the curved path RF leg type, but you won't find any of these in the existing WAAS GPS databases as none of the Garmin panel mount GPS units support the RF leg in their AFMS. They have the software to perform the RF leg type, but until the FAA approves the use these legs with the GPS for part 91 operations, Garmin can't include them in the database. At that point, Garmin would have to update the software to enable the RF leg to be used and issue a new AFMS to go with the ability.

The poster child is the RNAV (GPS) X RWY 24 at KCRQ. You can find the RNAV (GPS) Y RWY 24 in the database, but not the X. At one point, the Y included the RF leg, but this prevented the procedure from being in the database, so the X was added that just has the RF leg feeder route and it was removed from the Y so it could be put back in the database.

Garmin did a white paper on the subject of flying the RF leg and demonstrated that with a minimum of training that it could be flown by pilots with all levels of experience.
 
How would a curved path help sequence airplanes? They still have to get into a straight line as all runways are straight. As I recall, that was a reason for abandoning MLS approaches...
 
Captain said:
How would a curved path help sequence airplanes? They still have to get into a straight line as all runways are straight. As I recall, that was a reason for abandoning MLS approaches...
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It can substantially shorten the route as the RF leg can have a turn radius of 3 NM. In certain situations, this can permit flying routes taking up less airspace and provide for more predictable operation over the ground. When aircraft turn at flyby waypoints, there is a great variation in the path based on turn anticipation and airspeed. TERPS has to protect that extra airspace and if there are obstacles this can force the MIA for the route to be higher.

It is not a be all for RNAV routes. It should just be another option in the tool kit to enable a route that would not otherwise be possible. In the case of the KCRQ RNAV (GPS) X RWY 24 procedure, the feeder route from OCN would not work with the constraints of the current TERPS without using the RF leg.
 
Ron, I too was getting the 404 error on your IAP links.
 
Captain said:
How would a curved path help sequence airplanes? They still have to get into a straight line as all runways are straight. As I recall, that was a reason for abandoning MLS approaches...
Click to expand...


It doesn't. It helps aircraft fly less miles when conflicting traffic doesn't exist.
 
Mountainous terrain avoidance and noise abatement are two reasons I have heard of for justifying curved approaches.
 
coloradobluesky said:
I was talking to a friend of mine that is a pilot with a major, you know flies the big jets. And I asked him if GPS approaches where helping him. He said yes, especially the curved approach paths. I've never seen a curved approach.

Anyone have any examples of a chart with curved approach path?
Click to expand...
How about the VOR/DME or TACAN Z RWY 15 at Martin State (KMTN)?

http://155.178.201.160/d-tpp/1405/05222VDTZ15.PDF

You don't even need one of them new fangled GPS things to fly it!
 
Brad, When no conflicting traffic exists, sure, the teardrop turn is a great time and fuel saver. Add conflicting traffic inbound from the east and the teardrop approach is unworkable. It creates a safety issue in that pilots are confused as to what to expect half the time. A buddy of mine had a SWA who was told to expect the RNAV Y from STEER, but the pilot executed the teardrop turn from MIING. Luckily he stayed at 4,000 or it could have gotten very ugly.

Loren, that's a good write up. Thanks for that.
 
MarkZ said:
Brad, When no conflicting traffic exists, sure, the teardrop turn is a great time and fuel saver. Add conflicting traffic inbound from the east and the teardrop approach is unworkable. It creates a safety issue in that pilots are confused as to what to expect half the time. A buddy of mine had a SWA who was told to expect the RNAV Y from STEER, but the pilot executed the teardrop turn from MIING. Luckily he stayed at 4,000 or it could have gotten very ugly.

Loren, that's a good write up. Thanks for that.
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Yes, I can imagine. I know SWA was working like crazy for a while working to get procedures built that could shave off time enroute whenever possible. Since fuel burn rates increase down low for turbine aircraft, every mile of vectoring and maneuvering down low represents $$ and time. Of course you guys in ATC are left trying to figure out how to integrate these procedures into your plan.
 
Jmcmanna said:
http://155.178.201.160/d-tpp/1405/00081RRY22L.PDF

MDW has 4 if these RNAV(RNP) approaches that right now, only SWA uses. Some of them have almost a continuous diving turn to the runway from the IF.
Click to expand...

I learned about RNP the hard way, so to speak.

About 3 years ago when I owned a Grumman Tiger, my wife and I slipped up from Little Rock to Chicago one evening, with a 50 knot push, landing Midway. When handed to Chicago Approach, I was told to expect to RNP Yankee to Runway 13C. I wrote it down and pulled up the plate in Foreflight:
http://155.178.201.160/d-tpp/1405/00081RRY13C.PDF

What? Curved paths, descending turns, right by O'hare, in IMC, during a busy time? I never knew until that moment curved approach paths were possible. So I reach over to my trusty Garmin 430W to dial up RNP Y to 13C and it's not in there. I see GPS Z but not RNP Y. Hmmm.

I called back to Approach and told him I didn't have the equipment to perform RNP Y. He responds, "Are you sure you can't do it? We're going to have to change a good bit up if you can't." I respond that I'll check again and would call back in minute or two. I then read the plate again on Foreflight, dutifully ask my wife if she sees an approach in the 430 that I'm overlooking since Approach is certain I should be able to do it.

I call back and say, "I'm sorry -- there is no RNP Y in my GPS." He then says, with an annoyed tone, he'll vector me to the final approach for GPS Z, "but keep looking for the RNP."

I kept looking until we were close and it was getting time to do the approach (about 1000 OVC). I land, feel like an idiot that I couldn't do what they wanted. Riding to the hotel, I call a CFII buddy and ask, "Have you ever heard of an RNP approach?" He says "no" and I feel a little better. We get to the hotel and I get on the Internet and realize I'm missing at least a few hundred thousand in equipment in my little Tiger to be able to pull one off.... and feel much better not being able to keep with the program.

Needless to say, I've known what a RNP approach is ever since.
 
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That's a bit embarrassing from an ATC standpoint...when the RNAV-Y 13C approach came on-line, we were specifically briefed that only SWA aircraft could do that procedure (and even then, some of their older aircraft couldn't do it). The backup is the ILS 13C because the RNAV-Z is too close to O'Hare to use except in the middle of the night. I think the workforce is much more educated now, so I don't think anyone would try to assign that approach again to a GA aircraft.
 
coloradobluesky said:
At KPSP RNAV 13R, what does the RNP 0.17 DA mean next to the 277 DH (or is an MDA?). And what does "AUTHORIZATION REQUIRED" mean?
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The RNP 0.17 is the Actual Navigation Performance required of the aircraft avionics system to descent to a DA of 728 feet. It means that the navigation system's estimated position uncertainty must not exceed 0.17 nautical mile. Only aircraft with approved RNP FMS and flight guidance systems can fly the AR RNP approaches.

Actual Navigation Performance (ANP). [FONT=Times New Roman,Times New Roman][FONT=Times New Roman,Times New Roman]Sometimes called Estimated Position Error (EPE) is an onboard computation of the estimated 95% Navigation System Error using knowledge of the real world navigation environment, i.e., number of satellites tracked, number/ geometry of ground facilities, and statistical error models of the various navigation sources. ANP is continuously compared to RNP, and the crew is alerted if ANP exceeds RNP. [/FONT]
[/FONT]
 
John Collins said:
The poster child is the RNAV (GPS) X RWY 24 at KCRQ. You can find the RNAV (GPS) Y RWY 24 in the database, but not the X. At one point, the Y included the RF leg, but this prevented the procedure from being in the database, so the X was added that just has the RF leg feeder route and it was removed from the Y so it could be put back in the database.
Click to expand...

I received a report recently that the KCRQ RNAV (GPS) X RWY 24 approach is indeed in the Garmin G1000 database. However, the OCN transition (the one with the RF leg) is not available, only the VECTORS transition.

This creates a potential point of confusion. Some pilots have been using the presence of an approach in the database to determine whether their GPS can fly it. Now, you need to look for both the approach and the anticipated transition. Beware RF legs!

For more information on why we are not yet seeing RF-leg support in GA avionics, check out the requirements in AC 90-105, Appendix 5. The entire navigation and flight control system (including autopilot/flight-director) needs to be certified together and appropriate procedures published in the AFMS. That might be achievable with an integrated panel like the G1000, but it becomes a lot more tricky for retrofit panels.

To date, the only GA avionics I know that has been certified for RF legs on RNAV (GPS) approaches is the Avidyne R9 integrated flight deck.
 
I don't understand why a GA pilot would actually want to fly an RNP. Its a turbine aircraft procedure if there there ever was one. If getting slam dunked in is a priority there is the ILS or visual, if that fails there is the RNAV (non RNP, and yeah, if they've built an RNP an RNAV most likely exists) I've had single pilot aircraft types confused over RNAV STARS, never had one ask to go so far as to go whole hog and fly the approach.

RNP is all about a turbine going flight idle ASAP. Reading previous posts, asking a Tiger to do one? Seriously?
 
Approach_controller said:
I don't understand why a GA pilot would actually want to fly an RNP. Its a turbine aircraft procedure if there there ever was one. If getting slam dunked in is a priority there is the ILS or visual, if that fails there is the RNAV (non RNP, and yeah, if they've built an RNP an RNAV most likely exists) I've had single pilot aircraft types confused over RNAV STARS, never had one ask to go so far as to go whole hog and fly the approach.

RNP is all about a turbine going flight idle ASAP. Reading previous posts, asking a Tiger to do one? Seriously?
Click to expand...

Isn't it mainly about curved approach paths as well?
 
Ron Levy said:
In fact, a GPS alone is not sufficient to fly that approach -- you need a real DME, since the final segment uses DME for lateral guidance.
Click to expand...

Ron, could you elaborate on having to have DME vs GPS to fly the Martin State VOR/DME RWY 15 Approach? I'm an instrument student and we flew this approach in the SIM (G1000 C-182 panel, no DME). Granted the lesson was on flying DME arcs and my instructor just happened to use Martin State to show a real world example, but it wasn't really about the approach per se. Anyway, seems to me at the minimum you need a VOR to determine the FAF (I don't recall if CUMBE or GOVES were in the GPS data base as this was back in December), stepdown fixes, and the MAP, as they are defined where radials from the BAL VOR intersect the 14.7 DME arc. But why can't GPS sub for the DME?
 
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tsts4 said:
Ron, could you elaborate on having to have DME vs GPS to fly the Martin State VOR/DME RWY 15 Approach? I'm an instrument student and we flew this approach in the SIM (G1000 C-182 panel, no DME). Granted the lesson was on flying DME arcs and my instructor just happened to use Martin State to show a real world example, but it wasn't really about the approach per se. Anyway, seems to me at the minimum you need a VOR to determine the FAF (I don't recall if CUMBE or GOVES were in the GPS data base as this was back in December), stepdown fixes, and the MAP, as they are defined where radials from the BAL VOR intersect the 14.7 DME arc. But why can't GPS sub for the DME?
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Look at 8.b-c in Advisory Circular 90-108 (bottom of page 5 to top of page 6). Generally, you need the equipment named in the title and other notes of an approach. So, for a VOR/DME 15 approach, your plane needs both a VOR and a DME. Advisory Circular 90-108 is what allows a "suitable RNAV system" (GPS) to substitute for other navigation equipment.

However, it specifically disallows substituting for lateral guidance in the final approach segment. Normally this is not a problem, as the most common substitution is GPS for DME, and in almost all approaches, DME is there for step-down fixes or other progression-type (not lateral) guidance. Similarly, most VOR/DME approaches that do include arcs (where the DME provides lateral guidance), those arcs are not part of the final approach segment (for example, VOR/DME 22 at HUT).

The odd thing about VOR/DME 15 at MTN is that the DME distance is providing your lateral (turn right / turn left) guidance through the final approach segment. For that reason, it can't be substituted by GPS.

The same is true for standard VOR approaches: you must monitor a real-live radio VOR during the final approach segment (assuming the VOR radial serves as lateral guidance for the approach, as is typical). Also, you can never substitute for a localizer.

Oddly enough, with a certified GPS, working DME, but missing or broken VOR radio, you may fly the MTN VOR/DME 15, substituting GPS for the VOR step-down fixes (as they aren't lateral) and using the real-life DME for lateral guidance. Good luck finding a suitable alternate without a VOR though...
 
mcmanigle said:
Look at 8.b-c in Advisory Circular 90-108 (bottom of page 5 to top of page 6). Generally, you need the equipment named in the title and other notes of an approach. So, for a VOR/DME 15 approach, your plane needs both a VOR and a DME. Advisory Circular 90-108 is what allows a "suitable RNAV system" (GPS) to substitute for other navigation equipment.

However, it specifically disallows substituting for lateral guidance in the final approach segment. Normally this is not a problem, as the most common substitution is GPS for DME, and in almost all approaches, DME is there for step-down fixes or other progression-type (not lateral) guidance. Similarly, most VOR/DME approaches that do include arcs (where the DME provides lateral guidance), those arcs are not part of the final approach segment (for example, VOR/DME 22 at HUT).

The odd thing about VOR/DME 15 at MTN is that the DME distance is providing your lateral (turn right / turn left) guidance through the final approach segment. For that reason, it can't be substituted by GPS.

The same is true for standard VOR approaches: you must monitor a real-live radio VOR during the final approach segment (assuming the VOR radial serves as lateral guidance for the approach, as is typical). Also, you can never substitute for a localizer.

Oddly enough, with a certified GPS, working DME, but missing or broken VOR radio, you may fly the MTN VOR/DME 15, substituting GPS for the VOR step-down fixes (as they aren't lateral) and using the real-life DME for lateral guidance. Good luck finding a suitable alternate without a VOR though...
Click to expand...

Hey -- thanks!
 
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