What's magic about hold entry angles?

Discussion in 'Pilot Training' started by Andrew, Nov 28, 2022.

  1. Andrew

    Andrew Filing Flight Plan

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    They even make special calculators for it... plastic inserts you can flip over.... if you don't have an app that does it.

    You know what's easy? 90 degress. That's easy.

    I'm struggling to understand the magic behind the 70/110 degree angles thrown into the hold pattern entry equation. Just for fun I tried entering a few holds on my sim based on 90 degree standards, and it's 1) easy to instantly figure out, and 2) just... easy to fly.

    I'm sure*( there's some non-arbitrary reason it exists, but I can't find anything that explains its origins or reasoning.

    *Partially sure
     
  2. RussR

    RussR En-Route

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    There's nothing magic about it. Real life, enter whatever way you want as long as you stay (mostly) on the holding side of the inbound course.

    If you're preparing for a checkride, though, it's safest to do it the book way in case the DPE doesn't agree with me.
     
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  3. Bob Noel

    Bob Noel Touchdown! Greaser! PoA Supporter

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    angle is more important for fast moving aircraft and making sure the aircraft stays in protected airspace
     
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  4. eman1200

    eman1200 Touchdown! Greaser! PoA Supporter

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    Bro do you even lift
    because you're not always heading to the fix at a 90* angle?
     
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  5. Andrew

    Andrew Filing Flight Plan

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    Nope, I'm not. I'm also not at 70˚ or 110˚.

    But I can ALWAYS get easy 90˚ references on a DG or HSI or whatever.
     
  6. Andrew

    Andrew Filing Flight Plan

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    I thought of that but it doesn't make sense - if high speed approaches were the reason, why wouldn't it be 45˚, and different for high and low speed aircraft?
     
  7. eman1200

    eman1200 Touchdown! Greaser! PoA Supporter

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    the suggested entries don't say "if you're at 70 or 110", they say if you're within that range.
     
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  8. sarangan

    sarangan Pattern Altitude PoA Supporter

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    You can determine the type of entry just by eyeballing your current track compared to the inbound track of the hold. It doesn't have to be a calculation.
     
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  9. eman1200

    eman1200 Touchdown! Greaser! PoA Supporter

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    I'm well aware of that, thanks! I don't have any issues with hold entries, it's the OP that is questioning it.
     
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  10. MauleSkinner

    MauleSkinner Touchdown! Greaser!

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    The size of the protected airspace is predicated on the fastest airplane that the hold is built for using the “official” entry procedure…70 degrees is the design, so 70 degrees is the cutoff for preferred entry procedures.

    Personally, I use a teardrop entry unless it’s obviously direct, and never do parallel.

    Of course, “never” is a long time…if my FMS is flying the procedure, I’ll let it do whichever entry it’s programmed for, which will be the preferred entry.

    As @RussR indicated, examiners may have other opinions. I can’t put my finger on the guidance right now, but the FAA does state that the preferred entry is not required on a checkride as long as you stay in protected airspace. I’ve only had that argument with one examiner, and
    a. He avoided the issue by giving me a teardrop or direct entry hold on the checkride, and
    b. He never asked how I would determine that I was actually in protected airspace doing something other than the preferred entry.
     
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  11. drummer4468

    drummer4468 Pre-takeoff checklist

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    The "magic numbers/sectors" are basically there to establish a rote reference for how to efficiently enter holds depending on which range your intercept angle falls under. That said, many students, myself included, tend to overthink the crap out of it at first. They let all the numbers swirl around their head instead of simply visualizing a top-down view of their flight path vs the inbound leg. It finally "clicks" when they stop stressing about the numbers, angles, etc and just do what makes sense to get/stay established with standard-rate turns and no visual reference. Previously-VFR students tend to forget they can't just whip the plane around 160degrees in IMC like they're on a highway on-ramp, and need to get acquainted with planning further ahead.

    Tangentially, I used to be confused as to why there were even published entry methods at all. "Why do I have to cross the fix first and do all this parallel nonsense, can't I just enter on the outbound leg like entering downwind?" Finally it dawned on me, "Hey idiot, all you have is a VOR needle, there are no road signs in the sky. You need to establish a solid spatial reference point first before you start squiggling all over FlightAware figuring out why the needle won't re-center." I digress.

    In reality, as others said, it does not matter how you enter the hold. Controllers aren't gonna care (or probably even realize) if you enter parallel when textbook says teardrop unless they give you specific instructions. The only important factors are 1) knowing when you cross the holding fix, 2) staying on the protected side of the hold, and 3)timing the outbound/inbound legs accordingly.

    Do those three things and you'll pretty much be doing it by the book without even thinking about it, much less stressing about the "magic numbers".
     
  12. TCABM

    TCABM En-Route

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    I’m confused. Do you believe the 70/110 borders are the only angles one can enter a hold on?
     
  13. Andrew

    Andrew Filing Flight Plan

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    Of course not - they're the prescribed angles in the sector illustration.
     
  14. midwestpa24

    midwestpa24 En-Route

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    I do think this is one of those things that can be easily overthought. My solution, do which ever is easiest, which requires the least amount of turning. You should never have to turn more than 90 degrees to make an entry. And as been stated already, just make sure you are staying on the protected side of the hold. Granted, even the space on the opposite side is likely empty anyway, ATC won't put two aircraft in opposing holds at the same altitude, ever.
     
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  15. drummer4468

    drummer4468 Pre-takeoff checklist

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    Reminder that the protected side of the hold isn't only there because of traffic; it could very well be terrain, airspace, or other considerations. Yes, there are large margins built-in, but screwing it up, losing SA and flying the wrong heading can quickly turn catastrophic.
     
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  16. RussR

    RussR En-Route

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    This is a term that needs to go away. I have literally had pilots afraid to go even the tiniest bit onto the opposite side of the inbound course because they thought it was "not protected". It is most definitely protected. There is NO non-protected side of the hold. There is a side with a little less protected airspace than the other, but either side of the inbound course there are literally miles of horizontal protection (and 1000 feet of vertical clearance from obstacles).

    And, a textbook parallel entry goes onto this side as well. There is no problem or violation or risk of hitting something.

    A more correct term is "holding" and "non-holding" side.
     
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  17. RussR

    RussR En-Route

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    As an example, here is a fairly standard missed approach hold from an ILS into Ames, IA. Holding at 4000, so 200 kias max holding speed. There are a lot of lines on this map, but most importantly for this discussion is the inner red line of the "oval". This is the primary airspace that is evaluated for obstacles for the holding pattern. Notice that the width at the holding fix HANSD is about 5 or so nm on the holding side and about 4 on the non-holding side.

    I have added (in blue) a Cessna 172-size holding pattern, roughly to scale at an airspeed of 90 ktas, so 1 minute legs = 1.5 nm. You can see there is a TON of room. From a "not hitting anything" standpoint you could turn whatever direction you want and hold on whatever heading you want and be safe (in a 172). Obviously I'm not endorsing that!

    Obviously as you go faster you get closer to the edges and have less "wiggle room", but even at the maximum 200 kias you still have a lot of room (picture the blue line holding pattern at about 2.5x its size and you'll see what I mean). This is to account for wind, receiver error, pilot error, heading inaccuracies, etc., all added up to basically the worst case.

    upload_2022-11-28_10-20-5.png
     
    Last edited: Nov 28, 2022
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  18. drummer4468

    drummer4468 Pre-takeoff checklist

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    I understand your point but respectfully disagree. As I stated in my post above this one, the unprotected/non-holding sides do have generous margins built in. But loss of SA can cause massive problems if someone borks the entry, gets saturated, and flies the wrong heading for a minute(or longer) or 4nm or whatever the hold specifies. Possibly with a stout wind now on their tail, which flying in high wind to begin with only exacerbates the workload. Especially in areas without radar and/or radio coverage. This potentially unpredictable behavior can cause huge problems.

    Pilots SHOULD be strict about not straying away from the protected side, that's a positive quality that reflects proper discipline. Just the same as maintaining altitude and heading to standards. You're most likely not gonna hit anything being 150ft high or low either but "eh, close enough" doesn't cut it. Complacency breeds contempt.
     
    Last edited: Nov 28, 2022
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  19. RussR

    RussR En-Route

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    It's not about complacency, it's about terminology and proper procedure. Yes, of course you should fly proper procedures and hold yourself to a high standard. But that standard does not include "never go onto the (non-holding) side". Let me pose this extremely common scenario - you fly a parallel entry. As part of the textbook parallel entry you do not fly a course outbound from the fix, you fly a heading. That heading will, even in a no-wind situation, take you onto the non-holding side just based on turn radius alone. Add some crosswind and you go even further onto the non-holding side. This is 100% proper procedure, permitted, legal, safe, and accounted for in holding pattern design. There is no problem.

    Here's the figure from the Instrument Flying Handbook using the "holding/non-holding" terminology.

    upload_2022-11-28_10-38-39.png
     
    Last edited: Nov 28, 2022
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  20. RyanB

    RyanB Super Administrator Management Council Member PoA Supporter

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    Not only that, but it helps reduce the amount of maneuvering required to establish yourself in the hold.
     
  21. GMascelli

    GMascelli En-Route

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  22. Bob Noel

    Bob Noel Touchdown! Greaser! PoA Supporter

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    It's been a long long time since I've looked at TERPS documents. What does terms are used in TERPS docs?
     
  23. RussR

    RussR En-Route

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    Neither in this sense. The entire area is referred to as the "protected airspace". For the holding vs. non-holding-side construction measurements, those terms are not used, just measurements and dimensions. (Ref: FAAO 8260.3E, Chapter 16)
     
  24. drummer4468

    drummer4468 Pre-takeoff checklist

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    Yes, completely understood and correct. It obviously will happen, no question about that. My point is that it's still a standard that we should strive to uphold to the best of our ability. No, there won't be a 25,000ft mountain 1000ft outside the hold. But maintaining the discipline to fly precisely is still important in the instrument world.

    If I see my altimeter off by 75', I'm immediately gonna correct it even though I'm reasonably certain I'm not gonna hit anything.
    If my heading is off 5 degrees, I'm immediately gonna correct it though I'm pretty sure I'm not gonna be lost over the Pacific.
    If my CDI is half a dot off on the unprotected side, I'm immediately gonna correct it just the same.

    Deviations happen constantly and are usually fixed inconsequentially, but I think it's a universal sentiment that it's even better if I can manage to not have those deviations in the first place. Not that I'm implying we need to fly white-knuckled trying to ride on rails lest we instantly crater it, but there is still a reason it's called the "protected side" and renaming it to "non-holding side" doesn't really do much except subliminally make it "not as important". Having the SA and discipline to notice "hey I have a crosswind here, I'm gonna do everything I can to mitigate this and stay inside the lines" is still prudent, and reinforces the foundation of precise flying and keeping sharp on your navigation.
     
  25. luvflyin

    luvflyin Touchdown! Greaser!

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    Here's some stuff that gives some back ground on origins and reasoning.

    AIM 5-3-8 j.
    3. Entry Procedures. Holding protected airspace is designed based in part on pilot compliance with the three recommended holding pattern entry procedures discussed below. Deviations from these recommendations, coupled with excessive airspeed crossing the holding fix, may in some cases result in the aircraft exceeding holding protected airspace. (See FIG 5−3−4.)

    AIM 5-3-8 j. (d)
    While other entry procedures may enable the aircraft to enter the holding pattern and remain within protected airspace, the parallel, teardrop and direct entries are the procedures for entry and holding recommended by the FAA, and were derived as part of the development of the size and shape of the obstacle protection areas for holding.
     
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  26. MauleSkinner

    MauleSkinner Touchdown! Greaser!

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    So if you fly a parallel entry, you’re not going to fly it as it’s designed because you consider it a deviation?

    And/or, how immediate is immediately? Say you misjudge the wind on a teardrop entry, and you cross the inbound course as your 30-degree-banked turn takes your heading through 45 degrees to the inbound course? What constitutes “immediate” correction?
     
    Last edited: Nov 28, 2022
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  27. RussR

    RussR En-Route

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    But it's NOT called the "protected/non-protected side", that's my point. And I'm not making up a new name of "holding side" just to rename it. "Holding/non-holding side" is what it's actually called. The AIM calls it the holding side, the Instrument Flying Handbook calls it that, and so do numerous other official sources. The "protected/unprotected" term may have somehow made it into common usage, but it's not correct.

    And flying on the non-holding side doesn't just "happen", rather, it's intended. And necessary. And normal. Every teardrop entry starts on the non-holding side by necessity. Every parallel entry goes into the non-holding side AND stays there for one minute by design. See the AIM about holding entries (bolding mine):

    "Parallel Procedure. When approaching the holding fix from anywhere in sector (a), the parallel entry procedure would be to turn to a heading to parallel the holding course outbound on the nonholding side for one minute..."

    Calling it the "protected/unprotected" side is inaccurate and brings up more questions. I know, I've heard them from people who were taught this incorrect terminology. I've had people "cutting the corner" on a parallel entry before the VOR so that they don't go on the dreaded "unprotected side". Once in the pattern, I've had people creep up to the inbound course to avoid going even a little bit onto the "unprotected side". Neither or these is proper holding pattern technique. Calling it the "unprotected side" implies that it's dangerous over there and you risk death, when that's completely not the case.

    How will this correction be different than if you're a half-dot off on the holding side? Of course you're going to correct either way. But are you saying you're going to correct more aggressively on one side than the other?
     
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  28. dtuuri

    dtuuri En-Route

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    Y'need to ask the right person ;)
     

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  29. drummer4468

    drummer4468 Pre-takeoff checklist

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    Honestly, you're completely right. Looking back at my own posts, I don't even know why I was arguing, or what point I was trying to make, lol. Chalking it up to: I had just come off of night shift and my zombie brain apparently wanted to fight someone today.

    Cheers :biggrin:
     
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  30. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    It's just another example of something common. Someone comes up with an attempted simplification to supposedly make something easier to understand, and it catches on. But the simplification introduces inaccuracy that in turn leads to less understanding of the underlying principle. In the worst case, we end up using the inaccurate simplification as though it were the principle and extend it (I hear you chuckling - yes, many mnemonics work just like that).

    What's "easier"? A non-holding side that has smaller radii of protected airspace based on a series of templates? Or just calling it "unprotected"? Even if it leads us to give wrong answers.
     
  31. luvflyin

    luvflyin Touchdown! Greaser!

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    Holding Side and Nonholding Side. But you don’t need to go to TERPS and other esoteric documents to find that. See AIM 5-3-8.
     
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  32. iamtheari

    iamtheari Administrator Management Council Member PoA Supporter

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    The magic of the holding pattern entry sectors is that they work for a plane going 210 knots equipped with nothing but an ADF and a few steam gauges. In the real world, your Garmin navigator (or, as I call it, "Teardrop Entry Generator") will give you a magenta line to follow into the hold. Also in the real world, your plane probably isn't fast enough to leave the protected airspace regardless of which entry you use from which angle. It's probably worth knowing what the FAA teaches on these and following their guidance for the maximum safety margin. But you won't fall out of the sky if you come in on the 270 radial and use a teardrop entry for a hold on the 180 radial.
     
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  33. luvflyin

    luvflyin Touchdown! Greaser!

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    That paints a really good picture of what it’s about. It’s since been cancelled and incorporated into TERPS. Reduction Areas are no longer used.
     
  34. luvflyin

    luvflyin Touchdown! Greaser!

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    There can be problems with using RNAV for holding. It can lead you out of protected airspace. AIM 5-3-8 j. 7. tells ya all about it and how sometimes you should not do what the RNAV Navigator tells you to do. It’s about 4 pages long. A good read.
     
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  35. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    I my teach holds a little differently than many. There is no magic. They are sensible. I demonstrate that by describing the three suggested entries, then drawing a holding pattern. I place an airplane heading to it from various points and ask what they would do.

    I've had non-pilots with zero experience choose the AIM entries at least 75% of the time. And the other 25% was well within protected airspace and consistent with what I've seen from flight schools which only teach two entries.
     
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  36. luvflyin

    luvflyin Touchdown! Greaser!

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    What do you do about parallel entries when using RNAV Navigators? Do you let it lead the outbound turn and join the holding course outbound? Or do you fly over the Fix and then ‘parallel’ the outbound course?
     
  37. Pinecone

    Pinecone Pattern Altitude

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    That is what I do.

    And the 70 degree to parallel puts you FURTHER into the non-protected side than the 90 degree. And then with the parallel entry, you STAY on the non-protected side for the entire outbound leg. WHY????

    Using 90 degrees on only teardrop or direct you spend a very short period of time on the non-protected side.
     
  38. Pinecone

    Pinecone Pattern Altitude

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    I would let it lead the turn. The requirement to fly over the fix comes from the days that to identify the actual fix (VOR station or radio range) you HAD to fly over it.
     
  39. luvflyin

    luvflyin Touchdown! Greaser!

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    Why?? Because there is no such thing as the non-protected side. Roughly, about 40% of the protected airspace is on the non-holding side.
     
  40. luvflyin

    luvflyin Touchdown! Greaser!

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    Holding patterns are still designed predicated on flying over the Fix. AIM 5-3-8 j. 7. (a)
    (a) All holding, including holding defined on an RNAV or RNP procedure, is based on the conventional NAVAID holding design criteria, including the holding protected airspace construction. There are differences between the holding entry and flight track assumed in conventional holding pattern design and the entry and track that may be flown when RNAV guidance is used to execute holding. Individually, these differences may not affect the ability of the aircraft to remain within holding pattern protected airspace. However, cumulatively, they can result in deviations sufficient to result in excursions up to limits of the holding pattern protected airspace, and in some circumstances beyond protected airspace. The following difference and considerations apply when an RNAV system furnishes the lateral guidance used to fly a holding pattern: