GPS Holding Entries

[AngelFuree]

Wow, I can't believe I hadn't thought about this before. Anyway, someone posed this question to me and it brought some uncertainty as to what I think is the answer. I almost feel dumb for asking this question, lol. I should probably know this by now.

Many GPS holding patterns call for 4 or 5nm legs rather than the standard 1 min. Normally, for a parallel or teardrop entry, you are to fly 1 minute outbound before commencing your turn inbound for the hold.

The question was......for a parallel entry into a 5nm leg GPS holding pattern, are you to fly outbound for 5nm before commencing your turn inbound or would you fly one minute outbound? ...how about for a teardrop entry into a GPS hold? Would you fly 5nm outbound while on the teardrop before commencing your turn inbound?

I have always thought you DO fly the published distance and NOT the 1 minute for the entries. However, someone mentioned to me that it's more of a gray area since it isn't really talked about in the AIM. He thinks it's one minute.

I don't have the AIM handy w/ me, but I would appreciate your input. What do you think?

[Chris_Ford]

I have used 1 minute (as long as it does not exceed the 5 mile distance) on teardrop entries. Parallel, I'd probably go with 5 miles.

[aloft]

Originally Posted by AngelFuree

The question was......for a parallel entry into a 5nm leg GPS holding pattern, are you to fly outbound for 5nm before commencing your turn inbound or would you fly one minute outbound? ...how about for a teardrop entry into a GPS hold? Would you fly 5nm outbound while on the teardrop before commencing your turn inbound?

Let's think about that for a second. Suppose you're gonna do a teardrop entry, and after crossing the holding waypoint, you turn the usual 30 degrees off of the reciprocal of the inbound leg. If you flew 5 miles on that heading, do you think you'd still be in protected airspace?

The entry is the entry, the legs are the legs. They are not one and the same, so fly the entry the same way you would at a navaid, DME fix or any other holding point--that is, one-minute outbound after crossing the waypoint. Once established in the hold, fly legs of the specified length.

[surreal1221]

Yeah. . .glad aloft said it.

The entry is the entry. . .the legs are the legs.

1 minute entry (teardrop or parallel), 4nm (or whatever is called for) leg distance.

[Chris_Ford]

Originally Posted by aloft

Let's think about that for a second. Suppose you're gonna do a teardrop entry, and after crossing the holding waypoint, you turn the usual 30 degrees off of the reciprocal of the inbound leg. If you flew 5 miles on that heading, do you think you'd still be in protected airspace?

You'd be 2.5 miles off the track of the inbound leg. I'm fairly certain that's still within protected airspace. And you could be holding at 15,000 feet anyway.

[tgrayson]

Originally Posted by Chris_Ford

You'd be 2.5 miles off the track of the inbound leg. I'm fairly certain that's still within protected airspace.

You are. You have at least another mile of primary protected airspace, and then two miles of secondary (at least for a TERPed hold.)

The AIM gives no indication you should be using timing for entries into a DME/GPS hold, so I don't teach that. However, timing does work better; if you go out 2.5 miles, then your turn inbound will leave you well away from the inbound course, unless you roll out early with an intercept.

[MidlifeFlyer]

Originally Posted by aloft

The entry is the entry, the legs are the legs.

Yep. Even in the non-GPS entries this is the case. The measurement, whether time or distance, is ultimately based on =inbound= distance. The entry is just a way to get you established inbound for the first time.

If you look at the AIM (5-3-7.j.3.), the recommendations for 1 minute outbound for the teardrop and parallel entries are independent of whether the hold itself is a timed or distance one, or whether it's based on a VOR, NDB or GPS..

[tgrayson]

Originally Posted by MidlifeFlyer

the recommendations for 1 minute outbound for the teardrop and parallel entries are independent of whether the hold itself is a timed or distance one, or whether it's based on a VOR, NDB or GPS..

Not the way I read it:


5. Distance Measuring Equipment (DME)/ GPS Along-Track Distance (ATD). DME/GPS holding is subject to the same entry and holding procedures except that distances (nautical miles) are used in lieu of time values.

[surreal1221]

Hmm, not gray at all.

Same entry (time) - and holding procedures, except that distances (4nm) are used in lieu of time values (1 min legs).

Why must this be confusing?

[BobDDuck]

Even at 265 knots (and let's assume no wind) the "1 minute" outbound will only net you just over 4.5 miles.

I was thinking about the published hold at BUNTS going into PHL. It's a listed for 4NM legs due to an victor airway that is just to the west of the fix. It's a direct entry off the arrival, but if for some reason you were coming in the other way (from the east) and teardropped the entry and were going 265 (figure holding high into PHL is a safe bet) AND there was a pretty good tailwind, you would certainly pass beyond the 4NM bottom end of the hold.

[tgrayson]

Originally Posted by surreal1221

Hmm, not gray at all.

Same entry (time) - and holding procedures, except that distances (4nm) are used in lieu of time values (1 min legs).
Why must this be confusing?

Why are you arbitrarily deciding that the "except that distances (nautical miles) are used in lieu of time values." only applies to the "holding procedures" and not the "entry procedures." That's not a reasonable reading of the sentence. You can't just stick in words that you think should be there, but aren't.

Why must this be confusing?

It isn't. That sentence could not be clearer. You're reading what you want it to read.

[surreal1221]

I'm not adding words anywhere.

The sentence is clear as day. The exception is after holding procedures, not entry. So, the exceptions are directed towards the holding procedures. . .but hey, you're much wiser and stuck in your ways and have much more experience than I do so I won't bother trying to convince you of it.

If you're so certain that the exception "distance instead of time" refers also to the entry procedures, would you care to show me in either the IFH or AIM, or other FAA supported document that EVER mentions using distance during the entry into a hold?

In my experience, while limited, I have NEVER read or even HEARD of using DISTANCE to control your entry into a hold. Always time.

[phoenix 23684]

Originally Posted by BobDDuck

Even at 265 knots (and let's assume no wind) the "1 minute" outbound will only net you just over 4.5 miles.

I was thinking about the published hold at BUNTS going into PHL. It's a listed for 4NM legs due to an victor airway that is just to the west of the fix. It's a direct entry off the arrival, but if for some reason you were coming in the other way (from the east) and teardropped the entry and were going 265 (figure holding high into PHL is a safe bet) AND there was a pretty good tailwind, you would certainly pass beyond the 4NM bottom end of the hold.

Yes, but don't you have recommended holding speeds at your airline? No need to blast at 265 kias in a hold, turn too often, I know it's legal at 14+. I do ours at 160 kts, Saab 340, and if I can, I request 10nm legs, but that's in TX, we have a little bit more empty space.

I used to teach my students just to do the 1 minute thing on the GPS to keep things consistent, oviously if you are going to go past the protected area or into an airway, then those are the times when common sense should come in the picture. Specially when you have your GPS and FMS giving you a pretty little picture of the hold

[tgrayson]

Originally Posted by surreal1221

The exception is after holding procedures, not entry. So, the exceptions are directed towards the holding procedures

That could have been their intent, but the most reasonable reading of it is that the exception is attached to the compound direct object "entry and holding procedures", just like the word "same" clearly applies to both (which you don't seem to have trouble with.)

Had their intent been to still use time for the entry, this would have been the place to make it clear, with something like "but you should use timing for entries into all types of holding patterns."

would you care to show me in either the IFH or AIM, or other FAA supported document that EVER mentions using distance during the entry into a hold?

Yes. Right here.

but hey, you're much wiser

Exactly, so quit whining.

[BobDDuck]

Originally Posted by tgrayson

Why are you arbitrarily deciding that the "except that distances (nautical miles) are used in lieu of time values." only applies to the "holding procedures" and not the "entry procedures." That's not a reasonable reading of the sentence. You can't just stick in words that you think should be there, but aren't.

It really doesn't say anything about the entry in that section. If you read other sections of the AIM they tend to apply navigation logic section by section, so I would expect to see the NM instead of time substitution to be included in the Holding Entry section if it applied there.

I'm trying to remember how the FMS does it. I haven't done anything but a straight in entry for ever. Anybody do an oddball hold recently and have the FMS fly it? Does it do 1 minute outbound or does it just stay inside the pretty circle on the map?

Originally Posted by phoenix 23684

Yes, but don't you have recommended holding speeds at your airline?

Flaps 0 REF+30. Normally works out to about 210 knots or so.

[surreal1221]

tgrayson,

It's simple to me. I have NEVER seen anything (a 1nm / 2nm / 3nm) that specifies entry legs in distance. . .it has always been time (1 minute).

If you can provide me actual digits to use during a GPS/DME hold for entry leg lengths (in NM format) then I'll shut my trap.

But, it also appears that I'm not the only one that is disagreeing with you.

So, take that for what you wish.

[tgrayson]

Originally Posted by surreal1221

It's simple to me. I have NEVER seen anything (a 1nm / 2nm / 3nm) that specifies entry legs in distance. . .it has always been time (1 minute).

I don't know what you mean here.

If you can provide me actual digits to use during a GPS/DME hold for entry leg lengths (in NM format) then I'll shut my trap.

And why would I want you to shut your trap? And I don't know what you mean by "actual digits".

But, it also appears that I'm not the only one that is disagreeing with you.

Ah, truth by democracy.

As I said earlier, I think time works better for all entries, so I view the AIM sentence as recommending a poor procedure.

Since I have an all-consuming desire for truth and justice, I sent off an email to Air Traffic Publications requesting that they clarify the paragraph in the AIM. I did not specifically ask that they email me their interpretation of what it means, but that could happen. If so, I will post it.

[Dugie8]

Ill throw in here. Your entry should match your hold, 5 mile legs, 5 mile teardrop or parallel. Keeps things easy, IMO. That being said, it really shouldn't matter unless you have one of those "canyon on both sides" holding patterns.

[MidlifeFlyer]

Originally Posted by tgrayson

Why are you arbitrarily deciding that the [font=Arial][color=black]"except that distances (nautical miles) are used in lieu of time values." only applies to the "holding procedures" and not the "entry procedures."

Perhaps because the part of the AIM that applies specifically to entry procedures says stuff like

==============================
(b) Teardrop Procedure. When approaching the holding fix from anywhere in sector (b), the teardrop entry procedure would be to fly to the fix, turn outbound to a heading for a 30 degree teardrop entry within the pattern (on the holding side) for a period of one minute, then turn in the direction of the holding pattern to intercept the inbound holding course.
==============================

instead of stuff like

==============================
(b) Teardrop Procedure. When approaching the holding fix from anywhere in sector (b), the teardrop entry procedure would be to fly to the fix, turn outbound to a heading for a 30 degree teardrop entry within the pattern (on the holding side) for a period of one minute (except where distances are used in lieu of time values), then turn in the direction of the holding pattern to intercept the inbound holding course.
==============================

One could equally ask why your are arbitrarily deciding that a provision that deals primarily with leg length applies to the entry process?

I think the AIM is probably susceptible to both interpretations. I'll stick with mine and add the proviso that since the forms of entry are recommendations with the sole purpose of allowing one to become established inbound while remaining within protected airspace, it really doesn't matter much.

[TXaviator]

Originally Posted by aloft

Let's think about that for a second. Suppose you're gonna do a teardrop entry, and after crossing the holding waypoint, you turn the usual 30 degrees off of the reciprocal of the inbound leg. If you flew 5 miles on that heading, do you think you'd still be in protected airspace?

The entry is the entry, the legs are the legs. They are not one and the same, so fly the entry the same way you would at a navaid, DME fix or any other holding point--that is, one-minute outbound after crossing the waypoint. Once established in the hold, fly legs of the specified length.

this is also the explanation that seems to make sense to me. ive also heard that "as long as it works".... im personally a fan of the 90/270 procedure turn. :-D

er... as long as it works, is legal, and is within the protected area depicted. :-D

[AngelFuree]

Thank you all for the replies!
Upon reading that section of the AIM, it seems pretty clear to me that they are stating a substitution of distance for time with regards to holding and entries, so I'll go ahead and agree w/ tgrayson with his interpretation. However, I do agree with the others in saying that flying 4nm during a teardrop procedure might take you too far away making it unnecessary to fly out so far. I completely agree with that.

The description given by the AIM may very well be poorly written, but I do understand from it that the substitution of distances applies to both entries and holding.

To take this a step further, we can use simple trigonometry to see how far each procedure would take us.

So let's say you decide to...

...fly a teardrop entry with a 1 minute outbound at 100 kts. The distance covered in 1 minute is 1.6NM. If we use simple trigonometry, we can find out how far this actually takes us away from the inbound course. Given the 30 degree teardrop entry, our 1.6NM is the hypotenuse and all we need to find is our opposite side. sin(30)*1.6 = 0.8NM. That is, the one minute outbound teardrop entry will have taken us 0.8NM.

....fly a teardrop entry with a 4NM outbound leg, we can find how far, again. sin(30)*4=2NM. That is, the 4NM outbound teardrop entry will have taken us 2NM away. Not a HUGE difference, but something to consider.

The difference comes in with an increase in speed. Say, if we hold at 200kts, by flying a one minute entry, we will have traveled 1.6NM away from the inbound course. The difference would be minimal.

Just something to think about, I guess.

[casey]

short answer:

holding patterns at the altitude you are are most likely to be at are built to be flown at the TAS equivalent of 210 KIAS with lots of margins for wind, error, nav course width, etc. The protected area of the hold is quite large, you arent going to fly out it.

long answer:

FAA order 7130.3a will tell you how to plot the protected area of a hold based on altitude, speed and distance from the navaid (for conventional nav).

http://www.faa.gov/about/office%5For...ia/7130-3A.pdf