Interesting approach #2: ILS or LOC RWY 17 at KCVO

Discussion in 'Cleared for the Approach' started by coma24, Nov 12, 2019.

  1. coma24

    coma24 Line Up and Wait

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    Not quite as interesting as the RNAV Y 16R at EUG (covered in other thread), but this one caught me out briefly....

    FAF is LWG NDB, at or above 2500. PFAF is 1.2nm outside of that, a full 300ft higher. The altitude of the glideslope isn't actually published for the FAF.

    It's subtle, but I haven't come across many approaches where the PFAF and the FAF were 1.2nm apart. Sure, there are plenty of cases where the lowest GS intercept point is JUST outside the FAF...but I haven't seen one this far out.

    Any other approaches out there which are similar in nature?
     
  2. Arnold

    Arnold Pre-takeoff checklist

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    Okay, maybe I'm just old but the term PFAF is new to me. The FAF is not at LWG, it is glideslope intercept at at the the published glideslope intercept altitude, in this case 2500 which is coincident with LWG. If this were a LOC only approach then LWG would be the FAF. 2800' is the minimum altitude at ZIDKO this may or may not coincide with the glideslope at that location. But really, it's just an intermediate step down fix for the LOC approach. Nice to see there is still an operating NDB out there.
     
  3. luvflyin

    luvflyin Final Approach

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    Yes, there are others. 1.2 miles is a bigger spread than most. I think I remember one discussed here that had a big spread like this but I don’t remember which one. It happens when the FAF is defined by a geographic point on the ground where they can put an antenna, usually an NDB, sometimes a Marker Beacon, or both at the same location. Glideslope intercept, the lightning bolt, doesn’t always coincidently happen at that point.
     
    Last edited: Nov 13, 2019
  4. luvflyin

    luvflyin Final Approach

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    The FAF is at LWG. PFAF hasn’t been around forever. It was ‘invented’ so to speak, to deal with some of the discrepancies in defining when does the ‘Final Approach ‘Segment’ begin.’ When doing a Precision Approach, it begins at the now defined PFAF, not the FAF.
     
    Last edited: Nov 13, 2019
  5. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    I guess you are just old :D
     
  6. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    @aterpster might have an answer to "why?" I'm guessing there is some altitudevir distance requirement for ILS GS capture which may or may not be the same as the requirements for a nonprecision FAF, especially since a ground-based one might have other Nav functions.
     
  7. Arnold

    Arnold Pre-takeoff checklist

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    I knew it. 2 years until 70 for you young man.
     
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  8. Clip4

    Clip4 Final Approach

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    Nothing special about this approach either.
     
  9. aterpster

    aterpster Pattern Altitude

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    No reason that I can see. I was able to retrieve the coordination materials. The only significant obstacle is the one that drives the procedure turn altitude. Inbound from there both the LOC and ILS final segments have no significant obstacles. The ILS final could have been the same length as the LOC final.
     
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  10. coma24

    coma24 Line Up and Wait

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    I'd consider the 1.2nm spread between the non-precision FAF and the glideslope intercept point to be interesting as it can lead to an issue if you overlook it and instead assume a 2500ft GS intercept.
     
    Last edited: Nov 13, 2019
  11. aterpster

    aterpster Pattern Altitude

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    That wouldn't be proper procedure, but it would work.
     
  12. luvflyin

    luvflyin Final Approach

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    That wouldn’t cause a terrain and obstruction clearance issue. The Approach has non precision minimums and is built to accommodate ‘dive and driving.’ It might make it a little harder to fly given that you have a shorter time on the Glideslope needle but I doubt that would be significant. The significant thing that PFAF accomplishes is that once past it and established on the Glideslope, the FAF, and it’s altitude are not required to be complied with. It still is pertinent if you don’t have DME and want to ‘time’ the Missed Approach Point. That starts at the FAF. Another thing that can happen if you try to comply with the FAF altitude at the FAF is you may have to intercept the Glideslope from above. This can happen when it is hot.
     
    Last edited: Nov 13, 2019
  13. aterpster

    aterpster Pattern Altitude

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    The PFAF is significant to Part 121/135 ops, but otherwise not in this IAP.
     
  14. Clip4

    Clip4 Final Approach

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    What aircraft are you flying that is not equipped with a WAAS RNAV? If the GS transmitter were OTS, the RNAV 17 LPV is you second best option. Notwithstanding a practical test, there no reason for the LOC 17.

    yes, it you improperly brief any approach it can lead to an issue.
     
  15. coma24

    coma24 Line Up and Wait

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    Clip4, I flew my Lancair 360 from 2007 until June 2019 with a non-WAAS GPS (Garmin 420). The only reason I have WAAS now is because I moved to a 420W for ADS-B out compliance.

    I didn't mean to imply that the approach was earth shattering, critical to the NAS or completely bizarre....I just thought it was interesting as you don't often see/expect the FAF and PFAF to be spread out quite that much.
     
  16. luvflyin

    luvflyin Final Approach

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    How so?
     
  17. aterpster

    aterpster Pattern Altitude

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    121.651(c)