FAP on RNP approaches
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Yes, note back in post #5.
Still wondering about peekay showing gp intcpt on JABGO in that procedure profile... the Jepp plate provided by terpster shows FAP
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Yeah. Definition in AIM:
From the Instrument Procedures Handbook:
However, TERPS was completely revised last year (for the first time since the 1970s?) The new direction is to use "Precise FAF" (PFAF) for all approach types -- NPA, APV and PA. FAFs are now designated PFAFs if meeting the "precise" criteria. FAP is no longer used for approaches without a (P)FAF.
FINAL APPROACH POINT− The point, applicable
only to a nonprecision approach with no depicted
FAF (such as an on airport VOR), where the aircraft
is established inbound on the final approach course
from the procedure turn and where the final approach
descent may be commenced. The FAP serves as the
FAF and identifies the beginning of the final
approach segment.
only to a nonprecision approach with no depicted
FAF (such as an on airport VOR), where the aircraft
is established inbound on the final approach course
from the procedure turn and where the final approach
descent may be commenced. The FAP serves as the
FAF and identifies the beginning of the final
approach segment.
For a non-precision approach,
the final approach segment begins either at a designated
FAF, [...]. When a FAF is not designated, such
as on an approach that incorporates an on-airport VOR
or NDB, this point is typically where the procedure turn
intersects the final approach course inbound. This point
is referred to as the final approach point (FAP).
the final approach segment begins either at a designated
FAF, [...]. When a FAF is not designated, such
as on an approach that incorporates an on-airport VOR
or NDB, this point is typically where the procedure turn
intersects the final approach course inbound. This point
is referred to as the final approach point (FAP).
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A rose by any other name is still a rose....Bill Shakespeare.
Well, here we go...while the FAA has a FAF, FAP, and a PFAF, a "precise FAF,", do you see PFAF on a chart? Hell, at one time there was an FEP! GP intrcpt, given baro VNAV, which GP are you intercepting at a fix?
When there is no FAF, it is a FAP??! When in doubt "look to the box, look to the box..."
I can call it MFAF, ZFAF, LCHANCE, UR5NMFRMT, Uneed2BonFinalGP, whatever I want on the chart...... guess, what, bottom line, ARINC 424 code in the box understands FAF on a waypoint.
I really dont care what you call it, ICAO, FAA, precision, nonprecision, whatever....
ARINC 424: Fix Function in Coding: F = FAF, M = Missed Approach Fix
F=FAF.... this designates the beginning of the final approach segment.
go ahead, fight it, call it whatever you want...do you really want me to go into all of the other coding and sequencing in the aircraft FMS that is related to a FAF designation? (ie, what is the ROC required at FAP?)
Well, here we go...while the FAA has a FAF, FAP, and a PFAF, a "precise FAF,", do you see PFAF on a chart? Hell, at one time there was an FEP! GP intrcpt, given baro VNAV, which GP are you intercepting at a fix?
When there is no FAF, it is a FAP??! When in doubt "look to the box, look to the box..."
I can call it MFAF, ZFAF, LCHANCE, UR5NMFRMT, Uneed2BonFinalGP, whatever I want on the chart...... guess, what, bottom line, ARINC 424 code in the box understands FAF on a waypoint.
I really dont care what you call it, ICAO, FAA, precision, nonprecision, whatever....
ARINC 424: Fix Function in Coding: F = FAF, M = Missed Approach Fix
F=FAF.... this designates the beginning of the final approach segment.
go ahead, fight it, call it whatever you want...do you really want me to go into all of the other coding and sequencing in the aircraft FMS that is related to a FAF designation? (ie, what is the ROC required at FAP?)
Last edited by underfire; 15th Feb 2017 at 01:23.
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do you really want me to go into all of the other coding and sequencing in the aircraft FMS that is related to a FAF designation?
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An aircraft doesn't really understand what a "FAF" is. It can't: there isn't a single definition of FAF that's consistent across all approach types past, present and future.
ARINC 424 only describes a database format based on standards first formulated over 40 years ago! Consequently, codings such as FAF have been reused and redefined many times over the years.
And many procedures don't even have a FAF. Yet ARINC 424 requires a FAF entry thus we have to define some rules on what to stuff into this field, even though the published procedure doesn't have one. The onboard avionics might not actually do anything with this FAF entry other than to display it on the map, while for other procedures, the FAF is used to actually initiate descent.
So a FAF entry for a VOR approach may be treated differently than one for an ILS approach or (back to the topic of this thread) an RNP AR approach -- because technically they mean different things, even though they've all been shoehorned into the same ARINC 424 FAF coding.
Hence for every approach technology (from NDB to GBAS) we have to define translation rules on what to shove into the various ARINC 424 fields, and the corresponding changes to the aircraft avionics to interpret what those fields mean in the context of that specific technology.
ARINC 424 only describes a database format based on standards first formulated over 40 years ago! Consequently, codings such as FAF have been reused and redefined many times over the years.
And many procedures don't even have a FAF. Yet ARINC 424 requires a FAF entry thus we have to define some rules on what to stuff into this field, even though the published procedure doesn't have one. The onboard avionics might not actually do anything with this FAF entry other than to display it on the map, while for other procedures, the FAF is used to actually initiate descent.
So a FAF entry for a VOR approach may be treated differently than one for an ILS approach or (back to the topic of this thread) an RNP AR approach -- because technically they mean different things, even though they've all been shoehorned into the same ARINC 424 FAF coding.
Hence for every approach technology (from NDB to GBAS) we have to define translation rules on what to shove into the various ARINC 424 fields, and the corresponding changes to the aircraft avionics to interpret what those fields mean in the context of that specific technology.
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Gentlemen, I believe this thread was about charting, not ARINC coding. Pilots don't care about coding. The use of final approach point for on-airport, no FAF, VOR and NDBs has been around since the original issuance of TERPs in 1967. But, it was never charted until RNAV came along, then we got the sensor FAF. FAA charts still use the Maltese Cross for all procedures that have non-precision minimums.
Picking at nits, I believe P-FAF is the precision final approach fix.
EDIT: I stand corrected on P-FAF in 8260.3C. It is precise FAF, whatever that means. But, in the Pilot Controller Glossary it is still the Precision Final Approach Point. The FAA is overloading the pin's head with angels, so to speak.
Picking at nits, I believe P-FAF is the precision final approach fix.
EDIT: I stand corrected on P-FAF in 8260.3C. It is precise FAF, whatever that means. But, in the Pilot Controller Glossary it is still the Precision Final Approach Point. The FAA is overloading the pin's head with angels, so to speak.
Last edited by aterpster; 15th Feb 2017 at 13:54. Reason: add comment
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Yes PFAF was redefined last year with 8260.3C so now it is used for all approach types as mentioned earlier. You wont find plain old FAF or FAP anywhere in TERPS anymore.
I believe PFAF will continue to be charted as FAF on FAA plates. A PFAF is a FAF meeting certain accuracy constraints. With this redefinition, I'm curious to see if Jepp will follow FAA nomenclature for US plates going forward.
I believe PFAF will continue to be charted as FAF on FAA plates. A PFAF is a FAF meeting certain accuracy constraints. With this redefinition, I'm curious to see if Jepp will follow FAA nomenclature for US plates going forward.
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If you google Jepp's Briefing The chart Clinic Twenty First in a Series you will get the genesis of the term PFAF and FAP. Basically it had to do with the legality of the approach. On a LOC approach the Maltese cross designates the FAF. Once the aircraft passes the FAF you are allowed to continue to minima even if weather goes below minima. So they needed to define it also for precision approach. This precision FAF is the intersection the glide slope intercept altitude and the glideslope.
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Yup Vilas that was the original intent. However, the specific rule mentioned in the Jepp briefing has been amended since then, so a published FAF (or PFAF) is no longer required.
Then last year PFAF was redefined entirely (as above). It is no longer the glideslope intercept point.
Then last year PFAF was redefined entirely (as above). It is no longer the glideslope intercept point.
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Again, it was redefined. Summary:
Until 2016: "Precision Final Approach Fix". Old meaning: glideslope intercept point on a Precision Approach (hence the name). It is not defined on NPA procedures. Operationally, the location would vary with actual altitude flown.
2016 redefinition: "Precise Final Approach Fix". New meaning: the calculated position (fixed) where the vertical path or glideslope intersects the intermediate segment altitude. It may be defined for all approach types (PA, APV, NPA). A "Precise" FAF must be locatable within +/- 1 NM using intended navaids (e.g., VORs) or up to +/- 2 NM in certain other circumstances.
Until 2016: "Precision Final Approach Fix". Old meaning: glideslope intercept point on a Precision Approach (hence the name). It is not defined on NPA procedures. Operationally, the location would vary with actual altitude flown.
2016 redefinition: "Precise Final Approach Fix". New meaning: the calculated position (fixed) where the vertical path or glideslope intersects the intermediate segment altitude. It may be defined for all approach types (PA, APV, NPA). A "Precise" FAF must be locatable within +/- 1 NM using intended navaids (e.g., VORs) or up to +/- 2 NM in certain other circumstances.
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A historical perspective:
The original addition of TERPs became effective in November, 1967. I don't recall how many revisions it had.
The second edition came out sometime in 1977 and we know it had many revision, up until last year.
Also, now we not only have the third edition, we have adjunct criteria in the RNAV Order 8260.58A. For a few years we had the RNP AR standalone Order 8260.52, which was subsequently rolled into 8260.58.
Garmin is pushing for RF legs to LPV, which presently exists in Switzerland. (LSMD)
The original addition of TERPs became effective in November, 1967. I don't recall how many revisions it had.
The second edition came out sometime in 1977 and we know it had many revision, up until last year.
Also, now we not only have the third edition, we have adjunct criteria in the RNAV Order 8260.58A. For a few years we had the RNP AR standalone Order 8260.52, which was subsequently rolled into 8260.58.
Garmin is pushing for RF legs to LPV, which presently exists in Switzerland. (LSMD)
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ahhh...history!
Looking back, I seem to remember that many of the procedures were virtual ILS overlays (due to public outcry on any new procedure)
ATC was complaining that the FAF was at different locations than the FAF on the ILS procedures, and that ATC does not vector to a PFAF (or gs intcp).
From FAA guidance: "If the LOC FAF is defined by a facility such as a LOM, which cannot be moved, the present facility name will be assigned to the ILS PFAF. The RNAV FAF will be colocated with the ILS PFAF and share the common name. "
If that fails!
An underlying assumption of is that the ILS glidepath angle/TCH will coincide with the RNAV VDA/TCH. If this can't be done, a RNAV procedure, completely independent of the ILS procedure, will be developed."
Looking back, I seem to remember that many of the procedures were virtual ILS overlays (due to public outcry on any new procedure)
ATC was complaining that the FAF was at different locations than the FAF on the ILS procedures, and that ATC does not vector to a PFAF (or gs intcp).
From FAA guidance: "If the LOC FAF is defined by a facility such as a LOM, which cannot be moved, the present facility name will be assigned to the ILS PFAF. The RNAV FAF will be colocated with the ILS PFAF and share the common name. "
If that fails!
An underlying assumption of is that the ILS glidepath angle/TCH will coincide with the RNAV VDA/TCH. If this can't be done, a RNAV procedure, completely independent of the ILS procedure, will be developed."
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That wasn't for overlays, but for RNAV APV approaches on runways served by ILS. There was potential confusion because there could be two FAFs in close proximity to each other: one for the LOC and another for the RNAV.
aterpster might remember better but I believe the FAA never had any virtual ILS overlays. Overlays were on top of NPA procedures only (NDB, VOR, etc.)
aterpster might remember better but I believe the FAA never had any virtual ILS overlays. Overlays were on top of NPA procedures only (NDB, VOR, etc.)
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Peekay4:
Correct. The overlay program was to jump start the use of GPS when it became usable for IFR approach operations in the early 1990s. It was limited to VOR and NDB approaches, both on and off airport, with or without FAF. (thus the inception of the sensor FAF). There were only TSO C129 avionics at the time. Accuracy and sensitivity was inadequate for ILS, LOC, LDA, or SDF. Also, selective availability was still in use at the time the program was initiated.
As I recall over 5,000 IAPs were run through the regulatory mill in just a few months. Now, as a given runway end gets an RNAV IAP the overlay approach to that runway is cancelled.
aterpster might remember better but I believe the FAA never had any virtual ILS overlays. Overlays were on top of NPA procedures only (NDB, VOR, etc.)
As I recall over 5,000 IAPs were run through the regulatory mill in just a few months. Now, as a given runway end gets an RNAV IAP the overlay approach to that runway is cancelled.
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I was talking in context about RNP AR procedures, which were overlays on the existing ILS to avoid environmental review.
ILS overlays were very popular because the obstacle clearance area, and the similar 200' HAT/250'HAT
ILS overlays were very popular because the obstacle clearance area, and the similar 200' HAT/250'HAT
Last edited by underfire; 18th Feb 2017 at 08:54.
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underfire:
My view is the Reno ILS 16R is the way to go. Too few operators can do RNP AR. RF to LPV is also coming along once Garmin, et al, can convince the FAA. As I posted earlier the Swiss are already doing RF to LPV.
My view is the Reno ILS 16R is the way to go. Too few operators can do RNP AR. RF to LPV is also coming along once Garmin, et al, can convince the FAA. As I posted earlier the Swiss are already doing RF to LPV.
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terpster,
Yes, overtime, there has been the transition to simplify, and the whole AR requirement, while perhaps good at the beginning, should have settled down a little more to reality by now....turns are not unheard of close to final!
In the grand scheme of things, the ac holds the track pretty close, and the missed, well, while we kept the same 0.3RNP through the missed, the outcry when it was suggested to ICAO. Somehow, on the missed, the ac navigation falls apart and you need 1 RNP to contain it.
Currently, the RNP to GBAS final works very nicely, and while unofficial of course, the RNP to visual final.
On Reno ILS 16R, why is this a way to go, the minima at 500 is a bit tough...
In reality, the RNAV/RNP visual has the best chance, as it works well with the avionics, this would be similar to the RNP Visual (with turns!) that we had been working on. Hopefully, having turns in a procedure becomes more comfortable, and the AR requirement is reduced accordingly.
Yes, overtime, there has been the transition to simplify, and the whole AR requirement, while perhaps good at the beginning, should have settled down a little more to reality by now....turns are not unheard of close to final!
In the grand scheme of things, the ac holds the track pretty close, and the missed, well, while we kept the same 0.3RNP through the missed, the outcry when it was suggested to ICAO. Somehow, on the missed, the ac navigation falls apart and you need 1 RNP to contain it.
Currently, the RNP to GBAS final works very nicely, and while unofficial of course, the RNP to visual final.
On Reno ILS 16R, why is this a way to go, the minima at 500 is a bit tough...
In reality, the RNAV/RNP visual has the best chance, as it works well with the avionics, this would be similar to the RNP Visual (with turns!) that we had been working on. Hopefully, having turns in a procedure becomes more comfortable, and the AR requirement is reduced accordingly.
Last edited by underfire; 19th Feb 2017 at 23:26.