approach clearance phraseology

Discussion in 'Change to my Frequency...' started by GeorgeC, Sep 11, 2017.

  1. GeorgeC

    GeorgeC Pattern Altitude PoA Supporter

    Joined:
    Dec 5, 2010
    Messages:
    1,929
    Display Name:

    Display name:
    GeorgeC
    Why do controllers say "cross (initial) at or above (altitude), cleared (rnav xyz) approach" when that altitude is already on the plate?
     
  2. Ravioli

    Ravioli En-Route PoA Supporter

    Joined:
    Dec 1, 2014
    Messages:
    3,206
    Location:
    Fort Worth
    Display Name:

    Display name:
    Pasta Man
    @roncachamp will be along soon to assist.

    If I were to guess I'd say they are being nice to remind us. But he'll tell you what their book says.
     
  3. mscard88

    mscard88 Touchdown! Greaser!

    Joined:
    Oct 1, 2015
    Messages:
    11,979
    Location:
    Alabama
    Display Name:

    Display name:
    Mark
    Required to give you an altitude to maintain until you're established on the approach. Brought about because of an airline descended early on approach into Dulles I think it was and flew into terrain. During the 50s or 60s it occurred. As a result you receive an altitude to maintain.

    Also you must maintain the altitude assigned until you have course guidance for the final approach course. The reason is most often a TERPS/MVA issue. For example, the MVA around the airport is 5000, but the GS intercept for its ILS is 4700. If you went to 4700 before being near the final approach course, ATC would get an MSAW (minimum safe altitude warning) alert.
     
    Last edited: Sep 11, 2017
    GeorgeC likes this.
  4. luvflyin

    luvflyin En-Route PoA Supporter

    Joined:
    May 8, 2015
    Messages:
    3,115
    Location:
    Vancouver WA
    Display Name:

    Display name:
    Luvflyin
    That was TWA514, it was 1974. That incident led to FAR 91.175 (h) (2) (i).
     
    GeorgeC likes this.
  5. RussR

    RussR Line Up and Wait

    Joined:
    Jan 12, 2011
    Messages:
    841
    Location:
    Oklahoma City, OK
    Display Name:

    Display name:
    Russ
    Because unless there's a TAA on the plate, that information isn't already on the plate. And even if there is a TAA, the controller may have some other reason they need you to stay higher until established on the approach - traffic, MVA, etc.

    Example picked completely at random - FYG RNAV (GPS) RWY 15 - https://skyvector.com/files/tpp/1709/pdf/06478R15.PDF

    You're arriving from the southeast and are direct to IYBEP. Maybe you're 20 nm from IYBEP at 6000. If the controller just clears you for the approach without including an altitude, do you descend? When? To what altitude?

    But if the controller says "cross IYBEP at or above 4000, cleared approach", now you know what you're supposed to do.
     
    GeorgeC likes this.
  6. iamtheari

    iamtheari Line Up and Wait

    Joined:
    Mar 15, 2016
    Messages:
    686
    Display Name:

    Display name:
    Ari
    My guess:

    The crossing restriction tells you that you can descend at your discretion and you can do your own descent planning. Without the crossing restriction, you would have to rely on ATC doing your descent planning for you so you get low enough to fly the approach starting from the initial approach fix without having to descend at an abnormally high rate.

    This is a great example. In that situation, you can't descend until you are established on a published segment of the approach, so you would have to descend from 6000 to 2700 within 5 nm between IYBEP and EQAXO. That's 660 feet per nautical mile or 1320 feet per minute if your ground speed is 120 knots during the descent. Pretty steep, especially compared with the average 200 feet per nautical mile you have to get down the rest of the way to the airport elevation by the end of the approach procedure.

    It's easier for everyone if ATC can see that the terrain and traffic won't be a problem and tells you to descend at your discretion to the minimum altitude for the initial approach fix at your discretion.
     
  7. Larry in TN

    Larry in TN Line Up and Wait

    Joined:
    Nov 16, 2013
    Messages:
    576
    Location:
    Nashville, TN
    Display Name:

    Display name:
    Larry in TN
  8. Velocity173

    Velocity173 Final Approach PoA Supporter

    Joined:
    Jul 3, 2012
    Messages:
    7,889
    Display Name:

    Display name:
    Velocity173
    2. Assigned an altitude to maintain until the aircraft is established on a segment of a published route or instrument approach procedure. (See FIG 4-8-2.)

    EXAMPLE
    Aircraft 1 is cleared direct LEFTT. The MVA in the area is 3,000 feet, and the aircraft is at 4,000 feet. “Cross LEFTT at or above three thousand five hundred, cleared RNAV Runway One Eight Approach.”
     
  9. mscard88

    mscard88 Touchdown! Greaser!

    Joined:
    Oct 1, 2015
    Messages:
    11,979
    Location:
    Alabama
    Display Name:

    Display name:
    Mark
    Explained in post 3, sigh, and other posts, but it's POA, time to beat the horsey. :(
     
  10. N659HB

    N659HB Cleared for Takeoff

    Joined:
    Jul 20, 2013
    Messages:
    1,298
    Location:
    SC sandhills
    Display Name:

    Display name:
    No. 1 son
    Neigh....
     
    mscard88 likes this.
  11. roncachamp

    roncachamp Final Approach

    Joined:
    Jun 6, 2008
    Messages:
    7,045
    Location:
    De Pere, WI
    Display Name:

    Display name:
    Steven P McNicoll
    It's required by the ATC order when the aircraft is not on a published route.
     
  12. roncachamp

    roncachamp Final Approach

    Joined:
    Jun 6, 2008
    Messages:
    7,045
    Location:
    De Pere, WI
    Display Name:

    Display name:
    Steven P McNicoll
    TWA 514, December 1974.
     
    mscard88 likes this.
  13. roncachamp

    roncachamp Final Approach

    Joined:
    Jun 6, 2008
    Messages:
    7,045
    Location:
    De Pere, WI
    Display Name:

    Display name:
    Steven P McNicoll
    Which should make the altitude restriction "cross (initial) at or above (altitude), cleared (rnav xyz) approach" issued with the approach clearance unnecessary.
     
  14. roncachamp

    roncachamp Final Approach

    Joined:
    Jun 6, 2008
    Messages:
    7,045
    Location:
    De Pere, WI
    Display Name:

    Display name:
    Steven P McNicoll
    Some folks may prefer to read an entire discussion before responding. Some folks prefer to read and respond in sequence.
     
  15. mscard88

    mscard88 Touchdown! Greaser!

    Joined:
    Oct 1, 2015
    Messages:
    11,979
    Location:
    Alabama
    Display Name:

    Display name:
    Mark
    Point taken. Didn't think of it that way.
     
    Last edited: Sep 13, 2017
  16. luvflyin

    luvflyin En-Route PoA Supporter

    Joined:
    May 8, 2015
    Messages:
    3,115
    Location:
    Vancouver WA
    Display Name:

    Display name:
    Luvflyin
    Yup. I think it's important though to cover it from both ends. Requiring ATC to comply with the intent of 91.175 (h) (2) (i) by requiring them to issue an altitude to maintain until established is a pretty good idea. And requiring pilots to maintain last altitude until established if ATC f**ks up and forgets is a pretty good idea.
     
  17. iamtheari

    iamtheari Line Up and Wait

    Joined:
    Mar 15, 2016
    Messages:
    686
    Display Name:

    Display name:
    Ari
    I think it's 91.175(i) as in the lowercase letter after (h) rather than (i) as in the first lowercase Roman numeral as a subdivision of (h)(2). It's badly formatted in every source I can find online, but the sequence of (j) being next shows where the (i) belongs. The good news is that we are supposed to trust the same people who created that problem to reorganize and simplify the tax code.

    Anyhow, under 91.175(i), the pilot is responsible for maintaining assigned altitude until established on a published route. That's the rule because of TWA 514, which involved confusion between the pilots and ATC. (See post #4 by @luvflyin.) That does not necessarily mean that the crossing restriction as the OP asked about must always be given. It just means that the pilot should not make assumptions about descending without specific ATC clearance or a published route that says it's okay.

    But then to further reduce the chance of such a fatal assumption being made by a pilot, the crossing restriction is apparently required by ATC order when you're not on a published route. (See post #11 by @roncachamp.) What does the ATC order actually say? Does it allow for "descend and maintain X" to get us close enough to the first altitude on the IAP or does it always require "cross FIX at or above X"?

    This second part of the story, the ATC procedures, is something that most of us probably didn't learn while getting our instrument ratings but which would be useful to know so we have a better idea of the range of things we can expect while out there flying in the system.
     
  18. roncachamp

    roncachamp Final Approach

    Joined:
    Jun 6, 2008
    Messages:
    7,045
    Location:
    De Pere, WI
    Display Name:

    Display name:
    Steven P McNicoll
    The ATC order says:

    For aircraft operating on unpublished routes, issue the approach clearance only after the aircraft is:

    1. Established on a segment of a published route or instrument approach procedure, or

    2. Assigned an altitude to maintain until the aircraft is established on a segment of a published route or instrument approach procedure.


    No mention of altitude is needed in the first condition. In the second condition, if X is the appropriate altitude, and the aircraft is still above X, then "cross PHYXE at or above X, cleared RNAV runway 36 approach" is good phraseology. If the aircraft is already level at X, then "maintain X until PHYXE, cleared RNAV runway 36 approach".
     
    iamtheari likes this.
  19. Ravioli

    Ravioli En-Route PoA Supporter

    Joined:
    Dec 1, 2014
    Messages:
    3,206
    Location:
    Fort Worth
    Display Name:

    Display name:
    Pasta Man
    I knew he'd splain it for us!
     
    iamtheari likes this.
  20. luvflyin

    luvflyin En-Route PoA Supporter

    Joined:
    May 8, 2015
    Messages:
    3,115
    Location:
    Vancouver WA
    Display Name:

    Display name:
    Luvflyin
    Thats it. Something I might add is it is very common for a controller to include "an altitude to maintain...." when it's not necessary to because the aircraft is established. This altitude until established is serious stuff and controllers get it hammered in early in training. Don't confuse a controller giving it when it seems not necessary as some change in some rule or some random interpretation. ALWAYS giving it guards against making boo-boo's
     
  21. mscard88

    mscard88 Touchdown! Greaser!

    Joined:
    Oct 1, 2015
    Messages:
    11,979
    Location:
    Alabama
    Display Name:

    Display name:
    Mark
  22. roncachamp

    roncachamp Final Approach

    Joined:
    Jun 6, 2008
    Messages:
    7,045
    Location:
    De Pere, WI
    Display Name:

    Display name:
    Steven P McNicoll
    Outside of a crossing restriction, how would you issue an altitude to maintain until established on a segment of a published route or IAP to an aircraft that is established on a segment of a published route or IAP?
     
  23. luvflyin

    luvflyin En-Route PoA Supporter

    Joined:
    May 8, 2015
    Messages:
    3,115
    Location:
    Vancouver WA
    Display Name:

    Display name:
    Luvflyin
    Don't think I've ever heard that, it certainly would sound funny. I shouldn't have used the "established" example. My bad. I was getting back to the OP's original question "Why do controllers say "cross (initial) at or above (altitude), cleared (rnav xyz) approach" when that altitude is already on the plate?" That would sound like say "cross [fix] at or at or above" and then duplicate the altitude on the chart. Maintain [same altitude as the chart] until [fix]. This when already established so not necessary.
     
  24. TRocket

    TRocket Line Up and Wait

    Joined:
    Nov 10, 2014
    Messages:
    532
    Location:
    Charlotte, NC
    Display Name:

    Display name:
    Tony
    Because they are assigning you an altitude for you to maintain (which they are responsible for and you are likely already at) until you are established on the approach (i.e on the localizer or in this case the initial fix for the rnav appraoch) before you can descend below the assigned altitude.
     
  25. midlifeflyer

    midlifeflyer Final Approach

    Joined:
    May 25, 2006
    Messages:
    6,861
    Location:
    Chapel Hill NC
    Display Name:

    Display name:
    Mark
    I dont know the history but, based on the way most instructions of this type come about, a couple of guesses: accidents and incidents when people started descending early for varying reasons from misreading the plate to confusion - it’s a reminder; with vectoring and traffic, the altitude given may be higher or lower that the one on the plate; there’s a value to always doing it the same way each time, giving the basic numbers - less likely to make a mistake.
     
  26. luvflyin

    luvflyin En-Route PoA Supporter

    Joined:
    May 8, 2015
    Messages:
    3,115
    Location:
    Vancouver WA
    Display Name:

    Display name:
    Luvflyin
    Yeah. When being vectored to or direct to, both of which have you not on published segements, giving the altitude is absolutely mandatory, even if it is the same altitude that is published for that segement. For an aircraft that is already established on a published segement it would be redundant unless the controller needed the aircraft at a different altitude for traffic. Routinely Including the altitude with all clearances, even when unnecessary, would guard against the controller forgetting to when necessary and the pilot misreading the chart.
     
    Last edited: Sep 22, 2017 at 10:29 AM
    midlifeflyer likes this.
  27. Radar Contact

    Radar Contact Line Up and Wait

    Joined:
    Dec 10, 2016
    Messages:
    540
    Location:
    Illinois
    Display Name:

    Display name:
    Kevin
    As already mentioned:
    -It's in the book as a requirement
    -Is needed when not on a published segment of the approach
    -clears up any possible confusion

    Didn't see mentioned:
    -I issue at or above so the pilot doesn't have to worry about being precisely at the altitude by reaching the fix. One less thing to concentrate on especially when you have not far distance wise to lose quite a bit of altitude. A minor pet peeve of mine is when a controller tells an aircraft already at the altitude "at or above". Like the pilot is just going to arbitrarily climb up to start the approach. :dunno: