Takeoff minimums, are you sure?

Discussion in 'Cleared for the Approach' started by Dave S., Jan 3, 2020.

  1. Dave S.

    Dave S. Pre-takeoff checklist

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    This the point of the intial post.....

    Take two examples.

    1. A standard cg of 200 fpnm to 400 feet, and
    2. A non-standard cg of 512 to 1300 feet

    AIM..."...
    climbing to 400 feet above the departure end of runway elevation before making the initial turn. ..."

    The AIM clearly explains the 400 as a the minimum altitude (as far as standard minimums are concerned) before a turn on course should be started; in this case a diverse departure. If 400 means that in a standard minimum then logic follows that 1300 means the same thing in this non-standard minimum. Yes, it all serves as a minimum requirement for IFR departure as I stated in the original post. In other words, before I can start the takeoff roll I must have 1 mile viz (Im in a Baron) and my Baron must be capable of 200fpnm up to an altitude of 400 feet. Or, if I use the non-standard minimum here, my baron must have the performance capability to climb at 512fpnm all the way up to 1300 feet before I can start my roll. My Baron might be able to do that but my 172 may not in which case I would have to consider the other alternatives. This is a minimum requirement for departure BUT it is also a control requirement which states 'now that you have departed you must actually fly your airplane at the numbers used in the minimum, 512 and 1300'.

    Clearly the 1300 is a turn altitude or an altitude, once reached, which allows for a turn. AND, unless otherwise indicated, that turn can be a diverse turn in any direction.

    Now let's add the DP which says to fly heading 165 to 1400 BEFORE TURNING RIGHT. Let's to to the AIM once again...

    "...A greater climb gradient may be specified in the DP to clear obstacles [the 1400 in our example] or to achieve an ATC crossing restriction. If an initial turn higher than 400 feet above the departure end of runway elevation is specified in the DP [and it is...1400], the turn should be commenced at the higher altitude. ..."

    This explains the need to use 1400 instead of 1300 for our altitude to commence a turn. The rub is that it applies only to right turns!!! Putting it all together how do we interpret the entire departure process? Can we turn at 1300 unless it's a right turn then we must go to 1400?

    Here's a better question. If 1300 represents the altitude to which we must be able to climb at 512fpnm and thereafter 200fpnm (as you assume)...then at what rate of cg do we climb after 1300 up to 1400? 512? 200? And if 200 what of the obstacle? Has it been cleared sufficiently that climbing at only 200 will suffice as we go from 1300 to 1400. Remember, Im still runway heading at 1300 and have presumably cleared the obstacle. If I cant turn (if Im going right) until 1400 then I continue runway heading until 1400. But wait!!! I cleared SOME controlling obstacle at 1300 and would be able to reduce to 200 fpnm if I continued straight out. So how fast I go from 1300 to 1400 should be irrelevant.

    I believe the answer lies in the purpose of the takeoff minimum and the DP. The takeoff minimum gives us a brake release minimum AND includes a couple of control instructions. Those being 1) how fast to climb your airplane and 2) when you may turn your airplane (control instructions are not normally thought of as a "minimum"). The DP gives us nothing but control instructions and uses the cg rates specified in the TO minimum to do so. When TO and DP exist together the DP supersedes the TO minimum to the degree it intends. For example, you could turn on course in any direction at 1300 were it not for the DP which requires that if you intend to turn right then wait until 1400. Since all of that couldn't be wrapped up in a tidy TO minimum description then a DP must be used to clarify.

    I'm picking on 50F only because it's a simple example. The reason this needs to be clearly understood is that there are hundreds of other examples where differences between non-standard minimums and DP requirements are equally or more confusing and with greater differences. So let's not get hung up on Bourland for the sake of Bourland.

    And let me remind you again, a FSDO 135 POI and the gentlemen that builds these very minimums didn't agree and the interpretation. Although I gave more credence to the person in operations group his answers were sometimes iffy and didn't address any of the other issues I have brought up. It was like I stumped him on some of them.

    And we used Bourland as the example.

    tex

    "
     
    Last edited: Jan 3, 2020
  2. PPC1052

    PPC1052 En-Route

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    No, it doesn't. You are conflating the minimum altitude for when to turn with the minimum altitude for maintaining the increased climb gradient. Apples and oranges.
     
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  3. dtuuri

    dtuuri En-Route

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    TL;DR (sorry), but I did read enough to think you keep using "diverse turn" in a way I'm not comfy with. "Diverse" means with respect to the procedure design, not a reference to the pilot's actions. When they layout their gradients, "diverse" means in any direction from some indicated location, say 400' AGL on the runway centerline. It doesn't mean a turn in any direction from some other location the pilot may be located, say 1300' MSL. Does that help?
     
    Last edited: Jan 3, 2020
  4. PPC1052

    PPC1052 En-Route

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    No. Assuming you are 121/135, etc., if the weather is only 1 mile visibility, you have to be able to make 512 ft/nm until 1300.

    If you can only make 200ft/nm, then you need weather to be at least 300-2.
     
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  5. PPC1052

    PPC1052 En-Route

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    No. See my post above. That's the altitude at which you can reduce the climb gradient.
     
  6. PPC1052

    PPC1052 En-Route

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    No, the ODP in this case says nothing about a climb gradient. It only says to maintain runway heading until 1400 before turning right. The climb gradient is only in the the alternate take off minimums.
     
  7. PPC1052

    PPC1052 En-Route

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    (Not assume. That what the take off minimums say, but ok.) 200ft/nm after you get to 1300 works. Then at 1400, you could turn right.
     
  8. Clip4

    Clip4 Final Approach

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    This whole exercise is rather silly, even at 100 kts, the rate of clime is <900 fpm. Who’s flying a commercial aircraft with performance below that value.
     
  9. PPC1052

    PPC1052 En-Route

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    Yes. You can also turn to the left as low as 400 agl, which is 1273 msl, not too much lower than you can make your left turn if you wanted to.
     
  10. Dave S.

    Dave S. Pre-takeoff checklist

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    Actually, that is precisely what I am NOT doing.

    Every cg solution includes two things...1) a climb gradient and 2) an "to xxxx" altitude.

    We have been shown in the AIM that in the case of 400 (notice that it gives no other examples, which is part of my original problem) you may begin your turn. Since with a standard departure 200fpnm is used to 400 and 200 fpnm is the minimum used as a standard cg and at 400 we may begin our turn. Yet you insist that with the non-standard cg solution with its two parts 1) 512 and 2) to 1300 the altitude DOES NOT represent a turn altitude but only reflects the point at which the 512 can go to 200. You are getting confused because of the associated DP. Let's use a simpler example.

    MOUNT VERNON, TX
    FRANKLIN COUNTY (F53)
    TAKEOFF MINIMUMS AND (OBSTACLE) DEPARTURE PROCEDURES AMDT 1 11013 (FAA)
    TAKEOFF MINIMUMS: Rwy 13, 400-2½ or std. w/ min. climb of 238' per NM to 900.
    TAKEOFF OBSTACLE NOTES: Rwy 13.........

    Here there is no DP. I will ask the original question of you. If you use the std. w/ min. climb of 238' per NM to 900....what happens at 900? What cg may you now use? Can I go to 200 fpnm? Can I turn on course now? How much on course? Is this a diverse departure (any direction)? If, as you say, 900 only refers to the point where you can reduce to the standard 200 fpnm then when can I turn?

    Try to put this in a way that a new student IFR pilot can understand. Because I have 42 years of CFII and 37 years of ATC and I can't find a clear rule about some of this that I can understand. Alot of this is stuff we deduce or assume and even the ASW operation group designer and FSDO don't agree on some of it.
     
  11. MauleSkinner

    MauleSkinner Final Approach

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    under Part 135, jets need to make a net flight path that clears obstacles by 35 feet...that net flight path is OEI, and 512 ft/mile is often going to be a struggle. They’ll either need to reduce weight or ave an alternate procedure in the event of an engine failure.

    In the case of a light twin, it’s almost never going to make that kind of gradient single engine, but my experience is that most pilots count on the fact that engine failures only happen to somebody else.
     
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  12. MauleSkinner

    MauleSkinner Final Approach

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    Yes, at 400 ft you can turn...if no routing is specified for the DP, it’s a diverse departure area with turns allowed at 400 feet. The altitude becomes simply the top of the climb gradient requirement, and you can reduce to 200 ft per mile unless you’re already at the minimum IFR altitude. The AIM only gives the 400 ft example because anything else would be nonstandard and published in an ODP.
     
  13. Clip4

    Clip4 Final Approach

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    Except the minimum was 512 or 300-2, which does assure any performance.
     
  14. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    I agree it is not any more complicated than that. I'm confused by the confusion.

    There is a standard departure profile. It is a 200 FPMN climb beginning at 400' AGL in any direction. There are airports where the standard will not keep you clear of obstacles. It may need a change to the climb gradient. It may need restrictions on the direction you turn. It may need both. They only change what they talk about. For example, "min. climb of 238' per NM to 900" means exactly that and nothing more. It changes the 200 FPMN standard to 238 for the initial climb to 900. If it meant to change anything else, it would say so.
     
  15. MauleSkinner

    MauleSkinner Final Approach

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    300-2 only assures obstacle clearance by visual avoidance. It won’t clear procedurally. Only the 512 ft/mile clears procedurally.
     
  16. RussR

    RussR Pattern Altitude

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    Correct. You are allowed in this case to takeoff and visually avoid the obstacles.
     
  17. RussR

    RussR Pattern Altitude

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    I'm really not sure what the confusion is. In this example, you either have 400-2 1/2 in which case you can take off and climb at 200 ft per nm and visually avoid obstacles, OR if the weather is worse than that, you have to be able to climb at 238 ft per nm through 900. Passing 900, you may resume a normal climb of 200 ft per nm. Since there is no route specified, in either case you may turn and go on your way at 400 ft above the airport elevation. As long as you climb as specified, you won't hit anything.

    The reference is the previously stated AIM paragraph. If you tell us which part of that paragraph is confusing, I can try to help better.
     
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  18. Dave S.

    Dave S. Pre-takeoff checklist

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    Let’s see if we can reduce this down. Take Mt Vernon, F53. It has Ry 13/31.

    Assuming a ceiling of 100 and 1 mile viz the non standard TO minimum is 238 to 900.

    Please answer the following questions without any explaining. We’ll discuss it later.

    1. After departure off 13 as I am climbing at 238 per nautical mile can I turn on course, whatever that is, at 300 feet? Yes no
    2. After departure off 13 as I am climbing at 238 per nautical mile can I turn on course, whatever that is, at 400 ft? Yes no
    3. After departure off 13 as I am climbing at 238 per nautical mile can I turn on course, whatever that is, at 600 ft? Yes no

    And finally

    4. After departure off 13 as I am climbing at 238 per nautical mile can I turn on course, whatever that is, at 900 ft? Yes no.

    Now two more...

    5. Can I reduce my climb to 200 fpnm at 400 feet? Yes no. And
    6. Can I reduce my climb to 200 at 900 feet? Yes no

    I say
    No
    No
    No
    Yes
    No
    Yes

    Please just do that for the moment.

    Tex
     
  19. MauleSkinner

    MauleSkinner Final Approach

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    N
    Y
    N
    N
    N
    Y
    Well, technically #4 is a yes, because if you can turn at 400’, you can also turn at 900’. ;)
     
  20. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    Better yet, let's make one change and you can answer it again.
    The answers are no different changing 200 to 238 until reaching 900 ft because that is the one and only thing which has changed.
     
  21. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    Well, technically #3 and #4 are both yes for the same reason ;)
     
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  22. PPC1052

    PPC1052 En-Route

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    Wouldn't #3 also be yes, for the same reason?
     
  23. PPC1052

    PPC1052 En-Route

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    Drat. Mark beat me to it.
     
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  24. PPC1052

    PPC1052 En-Route

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    I am glad I am not the only one. When discussing with someone of his level of credentials, it makes really question what I am missing.
     
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  25. MauleSkinner

    MauleSkinner Final Approach

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    Unfortunately none of the credentials of anyone the OP mentioned is enough to determine expertise in performance. Most of the FAA Ops people I’ve asked have said they don’t know, and to buy commercially available airport analysis.
     
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  26. PPC1052

    PPC1052 En-Route

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    Maybe, but I'd expect a CFII to know more than me on this subject. Of course, we can't all know everything about everything. So not knowing one thing doesn't necessarily mean a person isn't very knowledgeable in general.
     
  27. MauleSkinner

    MauleSkinner Final Approach

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    I don’t expect anymore.
     
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  28. PPC1052

    PPC1052 En-Route

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    Maybe. But I am comparing to my level of knowledge, not to yours.
     
  29. MauleSkinner

    MauleSkinner Final Approach

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    The best you’ll ever do is figure out who’s full of **** and who’s not. Finding source documents (in this case, the AIM and Instrument Procedures Handbook suffice for me.)
     
    Last edited: Jan 3, 2020
  30. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    Sometimes a high level of knowledge can lead to overthinking. Or at least can't prevent it. No one is really immune from it.
     
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  31. Dave S.

    Dave S. Pre-takeoff checklist

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    So we have some answers that say that even with a non standard TO minimum which requires a 238 climb to 900 that a pilot can turn on course at 400.

    And one that says even once we get to 900 we can’t turn on course.

    Who believes that with a minimum of 238 to 900 that you can turn on course to any heading at 400? Please give your authority for that.

    And what is the authority for not being able to turn at 900.
     
  32. MauleSkinner

    MauleSkinner Final Approach

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    You’re even misreading the yes or no answers to your own yes-or-no questions...NOBODY is saying you can’t turn at 900’.
     
  33. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    The English language. Going to a "red shirt only" party does not tell me anything about the color pants to wear. Telling me I need a 238 FPNM climb rate to 900 does not tell me anything about when to make turns. "Climb on course 130 to 900 ft at 238 FPNM" does, but it doesn't say that.

    Don't be so committed to "it's confusing" that you can't see."
     
    Last edited: Jan 3, 2020
  34. dmspilot

    dmspilot En-Route

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    Why do you believe that a nonstandard minimum climb gradient automatically requires a higher altitude before turning? Please give your authority on which you base your belief.
     
  35. Dave S.

    Dave S. Pre-takeoff checklist

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    As I said before every non stand climb gradient has a “to xxxx” with it. Simple question....what is that altitude for? What does it represent? What does it mean to the departing pilot?


    Second question... does it have anything to do with when I may turn on course and be sure that I have cleared the controlling obstacle?

    What is the rule of thumb that tells me a when I may turn on course after departing with a non standard TO minimum?

    In other words tell me what 238 to 900 means to me as a departing pilot. What must I do or not do with my plane regarding cg and turns with 238 and 900?
     
    Last edited: Jan 3, 2020
  36. dtuuri

    dtuuri En-Route

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  37. MauleSkinner

    MauleSkinner Final Approach

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    It represents the altitude above which the nonstandard gradient no longer applies.


    not if a heading or track is not specified.
    There is no rule of thumb. You may turn at the standard 400 feet unless something higher is specified for turns.

    you must not turn below the standard 400 AGL.

    You asked for references for what everybody else says...they’ve been provided. @dmspilot asked you for references regarding your interpretation. Please provide more than “as I said before”, which has no documentation.
     
    Last edited: Jan 3, 2020
  38. Clip4

    Clip4 Final Approach

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    How does that work for a Cessna Caravan in a 135 op. You lose an engine that gradient is worthless and impossible during OEI.
     
  39. MauleSkinner

    MauleSkinner Final Approach

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    300-2 doesn’t procedurally clear without an engine, either.
     
  40. aterpster

    aterpster En-Route

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    Many thanks!