Circling radius and obstacle clearnce.

Discussion in 'Cleared for the Approach' started by John777, Nov 29, 2016.

  1. John777

    John777 Pre-takeoff checklist

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    For large aircraft like category D/E has 2.3 /4.5nm circling radius, whereas Category B aircraft is only 1.5nm from the end of the runways. Now my question is, if I go more than 1.5nm and stay within 2.3 or 4.5nm, provided their circling minimums are the same, am I technically still assured of obstacle clearance?
     
  2. MAKG1

    MAKG1 Touchdown! Greaser!

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    Not at Cat A minimums.
     
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  3. John777

    John777 Pre-takeoff checklist

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    Category A minimums if the minimums are not the same right?
    Can you give me a good reference on this?
     
  4. MAKG1

    MAKG1 Touchdown! Greaser!

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    Aeronautical Information Manual.
     
  5. John777

    John777 Pre-takeoff checklist

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    I guess you are referring to the Chapter 5 of the AIM, can you specify the subsection if you do not mind?
    Thanks.
     
  6. Greg Bockelman

    Greg Bockelman Administrator Management Council Member

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    Not sure but the TERPS manual might be a better reference.
     
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  7. RussR

    RussR Line Up and Wait

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    IF the minimums are the same for the higher Cats, then yes, you are assured of obstacle clearance.

    Random example - Blythe, CA KBLH, RNAV (GPS) RWY 26:

    https://skyvector.com/files/tpp/1612/pdf/00053R26.PDF

    If you are Cat A (or B as in your question) and you descend to 2060 for the Circling MDA, but swing out wide into the C or D area (where the MDA is also 2060), then yes, you still have at least the same obstacle clearance you did in the Cat A or B area. How would it be less?

    However, if you swing out wide, then you also should make sure you have enough visibility to keep the airport environment in sight.

    Now, if the Circling MDAs increase as the Category increases, the story is obviously different. Take Prescott, AZ, KPRC, VOR RWY 12 as another random example:

    https://skyvector.com/files/tpp/1612/pdf/00546V12.PDF

    If you're Cat B with 5580 for the MDA, and you go out into the Cat D area with 5940 MDA (but stay at 5580), chances are good that not only won't you have enough obstacle clearance but will actually be below the obstacles (mountains, antennas) at that altitude. Not good!

    Stay within the established radius. There should be no reason not to, especially with the new, increased circling radii for the higher Categories. And if you can't due to some unusual reason, maybe the best move is to go missed approach and try again.
     
    Last edited: Nov 30, 2016
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  8. John777

    John777 Pre-takeoff checklist

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    Yeah, I am going to look up FAA order 8260.3B for that.
     
  9. aterpster

    aterpster Pattern Altitude

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    It 8260.3C now. The new circling criteria radii increase with the elevation of the airport. There is a nice table in pilot-speak in the FAA legend for approach charts.
     
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  10. John777

    John777 Pre-takeoff checklist

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    Interesting fact I found out from the Order was, We can still go missed at MDA before hitting MAP but no turns...
    Is there any other reference other than the FAA Order?
     
  11. Greg Bockelman

    Greg Bockelman Administrator Management Council Member

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    You could always do that, couldn't you?

    How many references do you need?
     
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  12. John777

    John777 Pre-takeoff checklist

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    But when I was doing my training, I was taught to hold MDA until MAP and go missed. I mean, there still can be a chance to break out of thr clouds and see the runway and land, but you do not want to get close to runway when you are still 500-700ft above.
     
  13. Greg Bockelman

    Greg Bockelman Administrator Management Council Member

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    Yeah, that is kind of old school. The better way of doing that is to compute a visual descent point from which a normal descent and landing can be made. Once you pass that point, you know a landing really isn't possible so start the climb at that point knowing you have to continue to the MAP before making a turn.
     
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  14. Greg Bockelman

    Greg Bockelman Administrator Management Council Member

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    In other words, yeah, you might see the runway when you get closer, but if you are not in a position to make a normal descent and landing, a missed approach is required.
     
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  15. John777

    John777 Pre-takeoff checklist

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    My another question is, when ATC gives the heading to fly after takeoff, I usually start turning at 400ft because the obstacle clearance starts at 2nm beyond the end of the runway, is there any regulation regarding this?
     
  16. Ryanb

    Ryanb En-Route PoA Supporter

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    Where's your CFII for all of these questions? I'm honestly getting curious. If you're just a sim pilot just say it, there's no harm and we won't look down on you.
     
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  17. kayoh190

    kayoh190 Pattern Altitude PoA Supporter

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    I've previously been of the opinion that we've been duped into doing some kid's homework, or he's a troll having fun, or a sim guy, etc etc. Even if the answers to the questions are interesting at times, it's hard to for me to put forth the effort for someone that's not also interested in putting something back into the PoA community. This guy is a one way valve.

    But you just got me thinking...John777 mentioned his academy and SOPs. Now I don't have experience at a pilot mill like that, but perhaps the students don't get the kind of direct relationship with their instructor that we take for granted at a more traditional flight school. Combine that with a bunch of instructors that are presumably there to get their 1500 and get out, then maybe John777 is in a situation where he genuinely wants to learn this stuff, but is stuck in a learning environment where he's told to focus only on what he needs for the ride and nothing more.

    I just wish he'd tell us.
     
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  18. Ryanb

    Ryanb En-Route PoA Supporter

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    My thoughts exactly. I've been thinking this for quite some time. There is rarely ever a response when you try to ask him a question other than what his thread pertains to. It's hard for me to imagine that he has an instructor who is so absentminded to not give him adequate knowledge. POA doesn't serve as a CFI(I) replacement it's just a supplement. I'd love to hear more about his situation.
     
  19. tsts4

    tsts4 Line Up and Wait

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    I'm not convinced he's even a Private Pilot based upon his non-IFR related questions.
     
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  20. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    I don't know what the school's reason is for not wanting you to start a climb before the MAP, but while you're at that school it's probably easiest to do things the way they want them done (as long as it's legal and not putting you in danger). However it's important to realize that once you get to a point where it's no longer possible to land "at a normal rate of descent using normal maneuvers," then 14 CFR 91.175(c)(1) prohibits you from descending below DA/DH or MDA. (And by the way, even if you do start the climb early, for a missed approach that requires a turn, don't start the turn early.)
     
  21. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    Yes. Even though the MDAs are the same on that chart, the visibility minimums are higher for the higher categories.
     
  22. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    A reference that applies to pilots is 14 CFR 91.175(a), which says, among other things, that "Unless otherwise authorized by the FAA, when it is necessary to use an instrument approach to a civil airport, each person operating an aircraft must use a standard instrument approach procedure prescribed in part 97 of this chapter for that airport."

    The approach procedure is depicted on the chart, and it specifies the courses and altitudes to fly. As long as the altitude is depicted as a minimum altitude, then you are allowed to fly higher than that (because that's what "minimum" means). However if you deviate from the depicted course, then you're no longer using the approach procedure, which puts you in violation of the regulation above (unless you are doing so in response to an ATC instruction).
     
  23. MAKG1

    MAKG1 Touchdown! Greaser!

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    While it's not common to have maximum altitudes on instrument approaches, they do exist. All of the northwest approaches into Oakland top out at 1800 at the FAFs, for instance. The reason is San Francisco's approaches to the 19s, which are just above that.

    An early climb on those approaches might be problematic, at least above 1800. Note that some of those approaches have maximum altitudes charted on the missed (at 1600, not 1800), but the VOR 10R doesn't. So, what do you do if you decide to go missed just past the FAF?
     
  24. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    That's why I was careful to write "As long as the altitude is depicted as a minimum altitude..." When either a mandatory altitude or a maximum altitude is depicted, then you have to comply with those.
     
  25. MAKG1

    MAKG1 Touchdown! Greaser!

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    There is still a question, particularly for the VOR 10R approach, as to what the maximum is between the FAF and MAP. As charted, it suggests 1800 at the FAF and FL600 afterward. Given the SFO 19R/19L approaches overhead have minimums of 2800, that seems wrong, and any climb above 1800 past the FAF would be problematic, resulting in TCAS RAs. For the other approaches, like the ILS 12, a DESCENT to 1600 is called for if one decides to go missed right after the FAF.
     
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  26. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    I don't think it's wrong in the sense of violating any rule. If starting a missed approach climb after the FAF caused a conflict, ATC would have to manage the situation, but in the interest of safety, staying at or below 1800 until reaching the MAP might be the wisest action. :dunno:

    Yeah, it does look that way, all right.
     
  27. Harold Rutila

    Harold Rutila Pre-takeoff checklist

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    CAT B mins are 1.7 for approach procedures surveyed under the late-2012 circling radii revisions. The radii for CAT B and other categories actually increase depending on the MSL altitude of the MDA. This is all highlighted in AIM Figure 5-4-27 and 5-4-28.
     
  28. Harold Rutila

    Harold Rutila Pre-takeoff checklist

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    This is a small technicality, but the radii increase with the MSL altitude of the circling minima. This distinction is important at airports like Santa Monica (SMO) which have circling mins at over 1,000' AGL.
     
  29. aterpster

    aterpster Pattern Altitude

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    The obstacle evaluation uses the true airspeed 1,000 feet above the airport elevation. That doesn't mean the circling MDA will be 1,000 feet above the airport elevation. It's an TAS approximation. TAS varies with temperature in the real world. These criteria are a whole lot better than what we had previously. The maneuvering area the specialist evaluates will be predicated on that true airspeed. On one extreme if no significant obstacles are found, 300 feet will be added to whatever is found, and the standard circle to land MDAs will be used. (8260.3C, Table 3-2-1) On the other extreme, the circle to land MDA could be much greater than 1,000 feet Height Above Airport.
     
  30. Harold Rutila

    Harold Rutila Pre-takeoff checklist

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    Very interesting. Thanks for the explanation.
     
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  31. John777

    John777 Pre-takeoff checklist

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    Thanks.
    by the way, which section of the AIM states that Category A minimums does not count for obstacle clearance for other categories?
     
  32. Palmpilot

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    It may not have occurred to the authors of the AIM that anyone would think that Category A minimums would apply to anything other than Category A aircraft. You might be tempted to say that they should count if the higher category aircraft stays within the category A circling distance, but that probably would require excessive bank angles, because a faster aircraft is going to have a wider turning radius for a given bank angle.
     
    Last edited: Dec 7, 2016
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  33. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    By the way, I could be wrong, but my understanding is that even if you're flying an aircraft that would normally be flown faster, if you fly the circling maneuver within the category A speed limitation and remain within the category A circling radius (and are able to do so safely), then you can use category A minimums.
     
  34. MAKG1

    MAKG1 Touchdown! Greaser!

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    Abnormally slow approach or circling speeds is a rather unsafe way to perform an already dangerous maneuver.
     
  35. mscard88

    mscard88 Touchdown! Greaser!

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    Dangerous! :eek: Gheesh you're sounding like that Iceman character!

    Not if you know what you're doing and are competent. Done it with turbo props and jets, as well as GA planes. YMMV
     
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  36. aterpster

    aterpster Pattern Altitude

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    Statistics have shown the "classic" CTL can be quite hazardous, particularly at night and/or in rain or snow. The FAA decided many years ago to prohibit Part 121 CTL unless specific training was provided. It was a lot easier in a DC-6B than in a 707. American Airlines demonstrated that at KCVG.

    When TWA operated out of KMKC, CTL was legal and required to land on Runway 36. I rode the jump seat of a 707-300 that did it. Not very comfortable.
     
  37. aterpster

    aterpster Pattern Altitude

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    No, you cannot select a lower category, only a higher category.
     
  38. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    It's a question of degree. A 182 can be flown safely in either category A or category B speed ranges, for example. There's no way a 747 could. That's why I included the condition "and are able to do so safely."
     
  39. MAKG1

    MAKG1 Touchdown! Greaser!

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    But category A is a "normal" speed for a 182. The category is based on 1.3*Vs0 (or Vref if available) at max gross, which is less than 90 knots for a 182 in all configurations.
     
  40. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    I thought the category was determined by the speed being flown during the circling maneuver. If not, what speed is used to make the determination?
     
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