Holding Pattern DME/Timing

Banjo33

Banjo33

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Banjo33
I'm working on a project at work and have hit a decision point regarding holding patterns. I understand the restrictions and nature of holding...my question is: WHY are holding patterns identified via distance or timing? I can understand why you'd want to limit their size due to the protected nature of the airspace, but I don't think I've ever been taught that using less space/time than identified is acceptable (i.e. hold in a circle at the fix [is higher workload the issue?] or 30 second legs vice assigned 1 minute, etc.). Would holding in a circle at the fix be acceptable to ATC...regardless of workload? What if automation managed it for you?
 
I’m just a VFR pilot who is studying for the written, but it’s my impression that the straight inbound leg of a holding pattern is where you get re-aligned with the fix in order to assuredly cross that fix after flying toward it. After crossing, you fly the fix-end turn, the outbound leg, and the holding end turn without positive navaid assistance, but with the goal of getting assuredly re-aligned, yet again, to fly inbound and intercept the fix. Rinse, lather, repeat.

It may be odd, but I think of the inbound leg as comparable to the rebel X-Wings flying inbound on the trench run just below the surface of the Death Star. Booyah! The rest of the holding pattern is flying around to get lined up and then take another run down the trench.

If you were flying a circle, my sense is that it would be very difficult to assuredly re-intercept the fix each time around.

As to 30 seconds versus 1 minute, I'll leave it to others to comment, but I'd imagine that somebody decided that a full minute is necessary to ALWAYS get aligned on the inbound leg.

Probably makes it easier to deal with wind correction (circles could result in a spirograph-like path), and to do the mental math needed to exit the hold at a particular time in some instances.
 
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I'm thinking from an automation stand point. The software that I'm using is processing so fast that it can account for large variations in wind faster than a human to ensure it hits the "fix" everytime. And I'm not worried about pilot disorientation due to aggressive maneuvering of the aircraft to compensate. I'm just trying to find "if" and if so, "why" the holding pattern is so restricted to size.
 
It standardizes the procedure so you remain predictable to ATC, making it possible for them sequence a stack of traffic efficiently. If everybody was doing their own thing, it would cost the guy at the top a lot of time and gas.

A holding pattern isn't really limited by size at all. If I'm holding at 250 and you're holding at 150, then my pattern is going to be much larger than yours. Hence the holding airspeed restrictions for various altitudes. However, we will repeatedly pass the fix every three minutes or so.

Behind a ship in a marshal stack, there are no holding patterns. You are told to be at your holding fix at a certain time... usually a one minute interval behind the guy ahead of you. As long as you make it there, they don't care what you do...but don't be late. It usually resolves itself into a timed racetrack pattern.
 
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Banjo33 said:
I'm working on a project at work and have hit a decision point regarding holding patterns. I understand the restrictions and nature of holding...my question is: WHY are holding patterns identified via distance or timing? I can understand why you'd want to limit their size due to the protected nature of the airspace, but I don't think I've ever been taught that using less space/time than identified is acceptable (i.e. hold in a circle at the fix [is higher workload the issue?] or 30 second legs vice assigned 1 minute, etc.). Would holding in a circle at the fix be acceptable to ATC...regardless of workload? What if automation managed it for you?
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Acceptable to ATC? I don't know why not, assuming that circle took up no more space than the standard pattern. Your question is rather odd; I've had many pilots request nonstandard holding, but always for longer legs. They want fewer turns while you want a continuous turn.
 
wlawr005 said:
A holding pattern isn't really limited by size at all. If I'm holding at 250 and you're holding at 150, then my pattern is going to be much larger than yours. Hence the holding airspeed restrictions for various altitudes. However, we will repeatedly pass the fix every three minutes or so.
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Sure they are. The most distant points of a No. 1 pattern are about twelve miles apart, about 82 miles for a No. 31 pattern. Holding pattern speed limits help ensure the aircraft will remain within protected airspace.
 
Banjo33 said:
WHY are holding patterns identified via distance or timing?
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If you can come up with a different way of doing it. By all means share it with the class. Using the times/max holding speeds for your aircraft and DME distances will keep you within the protected airspace. If you just want to do 360s at the holding fix, you can certainly do that. But think if you were doing 360s with a stiff crosswind. How would you navigate along the inbound course? You would only be on it for a second or two. Flying a racetrack with an inbound course allows you to correct back to course during each circuit.
 
wlawr005 said:
It standardizes the procedure so you remain predictable to ATC, making it possible for them sequence a stack of traffic efficiently.
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Yup -- that's the theory behind the practice. If you want something different, you ask, and then the controller can build it into his/her plan. Otherwise, fly it as published or as cleared, as applicable.
 
roncachamp said:
Acceptable to ATC? I don't know why not, assuming that circle took up no more space than the standard pattern. Your question is rather odd; I've had many pilots request nonstandard holding, but always for longer legs. They want fewer turns while you want a continuous turn.
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I'm glad you chimed in, since I'm mostly concerned with ATCs take on it. Normally, if I'm given holding instructions, they contain a leg limit (DME), the holding procedure depicts a limit, or standard timing is assumed (1min/1.5 min based on altitude). I teach these numbers, I expect the student to fly these numbers (and I assume ATC expects me to fly these, as assigned/expected). But, is it an issue/problem to ATC if I fly a 30 second inbound leg vice 1 minute or a 1 mile leg vice an assigned 5 DME leg or hold in an orbit at the fix? Are they really trying to game the timing of my holding pattern?
 
Gucci Pilot said:
But think if you were doing 360s with a stiff crosswind. How would you navigate along the inbound course? You would only be on it for a second or two. Flying a racetrack with an inbound course allows you to correct back to course during each circuit.
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Not an issue, see post #3.
 
Banjo33 said:
I'm thinking from an automation stand point. The software that I'm using is processing so fast that it can account for large variations in wind faster than a human to ensure it hits the "fix" everytime. And I'm not worried about pilot disorientation due to aggressive maneuvering of the aircraft to compensate. I'm just trying to find "if" and if so, "why" the holding pattern is so restricted to size.
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Turns on instruments are normally made at standard rate, if you make a continuous 360 degree turn around a geo-referenced point you have to vary your angle of bank/rate of turn. So, to keep the turns at standard rate you have to have a short straight outbound leg to compensate for the wind.
I'm sure ATC doesn't really care how you do it as long as you stay in the protected airspace.
 
Banjo33 said:
I'm glad you chimed in, since I'm mostly concerned with ATCs take on it. Normally, if I'm given holding instructions, they contain a leg limit (DME), the holding procedure depicts a limit, or standard timing is assumed (1min/1.5 min based on altitude). I teach these numbers, I expect the student to fly these numbers (and I assume ATC expects me to fly these, as assigned/expected). But, is it an issue/problem to ATC if I fly a 30 second inbound leg vice 1 minute or a 1 mile leg vice an assigned 5 DME leg or hold in an orbit at the fix?
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Flying a smaller than expected pattern should not be an issue.

Are they really trying to game the timing of my holding pattern?
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I think that unlikely.
 
Banjo33 said:
I'm working on a project at work and have hit a decision point regarding holding patterns. I understand the restrictions and nature of holding...my question is: WHY are holding patterns identified via distance or timing? I can understand why you'd want to limit their size due to the protected nature of the airspace, but I don't think I've ever been taught that using less space/time than identified is acceptable (i.e. hold in a circle at the fix [is higher workload the issue?] or 30 second legs vice assigned 1 minute, etc.). Would holding in a circle at the fix be acceptable to ATC...regardless of workload? What if automation managed it for you?
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For charted holding patterns on approach charts, distance is only used on RNAV IAPs. The distance or timing use the same template for a given altitude.
 
Clark1961 said:
you don't have to remember that things fail? wow please present ample warning on anything you produce
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It's not germane to the discussion therefore I'm not participating in your attempt at dragging the thread off topic. Go lash out somewhere else. :dunno:
 
Banjo33 said:
It's not germane to the discussion therefore I'm not participating in your attempt at dragging the thread off topic. Go lash out somewhere else. :dunno:
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planning for failure is always germane to any design decisions - denial isn't just a river in Egypt...
 
aterpster said:
Give me a break. That is not what folks on this forum fly. Note also that procedure was designed by the USAF, not the FAA.

I only do FAA.
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You spoke in an absolute and I questioned you on it...I wasn't even sure of what you were saying.

I'm not even sure why you got so spooled up? I guess I was right and you felt like I called you out? Um, ok.
 
Banjo33 said:
I'm glad you chimed in, since I'm mostly concerned with ATCs take on it. Normally, if I'm given holding instructions, they contain a leg limit (DME), the holding procedure depicts a limit, or standard timing is assumed (1min/1.5 min based on altitude). I teach these numbers, I expect the student to fly these numbers (and I assume ATC expects me to fly these, as assigned/expected). But, is it an issue/problem to ATC if I fly a 30 second inbound leg vice 1 minute or a 1 mile leg vice an assigned 5 DME leg or hold in an orbit at the fix? Are they really trying to game the timing of my holding pattern?
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When the hold is charted with a distance or time, unless ATC clears you to fly hold using a specific leg length or time, the charted values are maximums and the pilot is permitted to fly the holding procedure using a shorter distance or time as appropriate for the specific hold. In these cases, the controller will typically clear you to hold as published. If the hold is part of a HILPT on an approach chart, the clearance is usually just a clearance to for the approach, maybe with a report established inbound.

If the hold is not published, the controller will assign a distance or time as part of the clearance. This is binding on the pilot as it is included in the clearance. If the controller has an operational need for a charted hold to be flown at the maximum distance or time, they can include it as part of the clearance, in which case it would be binding on the pilot.

The guidance in the AIM used to read as follows 5−4−9 Procedure Turn and Hold−in−lieu of Procedure Turn (a)-5.:

The holding pattern distance or time specified in the profile view must be observed.
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In 2010, it was clarified with the additional text to read as:

The holding pattern distance or time specified in the profile view must be observed. For a hold−in−lieu−of−PT, the holding pattern direction must be flown as depicted and the specified leg length/timing must not be exceeded.
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So back to the question asked, as a passenger I would say that being in a plane doing a circular hold even if the autopilot could do it perfectly would be less desirable than doing a racetrack preferably with longer legs. Before I got my certificate I recall always hating being a passenger on a jet flying into Heathrow where you always do several circuits in a hold there before landing. The constant turning would make me feel sick. It would have been far worse to have been on a tight circle with even more turning. Now it doesn't bother me but back then...
 
roncachamp said:
Never. I'd truly like to review some examples of your work.
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Did I say I design IFPs? No, I said I "do FAA." Which means I review and assess new and revised IFPs that are in coordination for an aviation organization.

But, for your amusement, here is link to a PDF file I did of five holding patterns at LAX VOR a few years ago.

1. P4 200 KIAS at minimum holding altitude. (P4 is minimum pattern size used for IFPs.)

2. P9 230 KIAS at 10,000 feet.

3. P15 265 KIAS at 16,000 feet.

4. P25 265 KIAS at 36,000 feet.

5. P30 310 KIAS at 41,000 feet.

http://www.terps.com/lax/laxholds.pdf
 
aterpster said:
Did I say I design IFPs? No, I said I "do FAA." Which means I review and assess new and revised IFPs that are in coordination for an aviation organization.
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So you're an art critic, not an artist. What aviation organization?

But, for your amusement, here is link to a PDF file I did of five holding patterns at LAX VOR a few years ago.

1. P4 200 KIAS at minimum holding altitude. (P4 is minimum pattern size used for IFPs.)

2. P9 230 KIAS at 10,000 feet.

3. P15 265 KIAS at 16,000 feet.

4. P25 265 KIAS at 36,000 feet.

5. P30 310 KIAS at 41,000 feet.

http://www.terps.com/lax/laxholds.pdf
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What is it that you actually did here? Did you create software that drew these patterns and thus made obsolete the templates that were used to draw them for decades?
 
roncachamp said:
What is it that you actually did here? Did you create software that drew these patterns and thus made obsolete the templates that were used to draw them for decades?
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Those templates haven't been used by approach designers since their first automation program went into effect many years ago.
 
John Collins said:
When the hold is charted with a distance or time, unless ATC clears you to fly hold using a specific leg length or time, the charted values are maximums and the pilot is permitted to fly the holding procedure using a shorter distance or time as appropriate for the specific hold. In these cases, the controller will typically clear you to hold as published. If the hold is part of a HILPT on an approach chart, the clearance is usually just a clearance to for the approach, maybe with a report established inbound.

If the hold is not published, the controller will assign a distance or time as part of the clearance. This is binding on the pilot as it is included in the clearance. If the controller has an operational need for a charted hold to be flown at the maximum distance or time, they can include it as part of the clearance, in which case it would be binding on the pilot.

The guidance in the AIM used to read as follows 5−4−9 Procedure Turn and Hold−in−lieu of Procedure Turn (a)-5.:



In 2010, it was clarified with the additional text to read as:
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Thank you John, that pretty much sums it up and is in line with some of what has been posted above. The reality of it is, you are required to fly it exactly as directed (whether written or verbal) in every dimension (unless cleared to deviate)..which is what's taught. However, I haven't really seen any indication as to WHY there's a reason for a distance/time other than to keep you in the protected airspace. I was just wondering if there was a legitimate reason other than the regulation itself (a reason other than: "because I told you so"), that would prevent a circling hold at the fix. You mention an "operational need," do you by chance have an example of what that would be?
 
John Collins said:
When the hold is charted with a distance or time, unless ATC clears you to fly hold using a specific leg length or time, the charted values are maximums and the pilot is permitted to fly the holding procedure using a shorter distance or time as appropriate for the specific hold.
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I can't seem to find that in AIM 5-3-8 Holding. Is that written somewhere else? OTOH, I do find the following:

b. If the holding pattern is charted and the controller doesn't issue complete holding instructions, the pilot is expected to hold as depicted on the appropriate chart.
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4. Leg length in miles if DME or RNAV is to be used (leg length will be specified in minutes on pilot request or if the controller considers it necessary).
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4. Timing.
(a) Inbound Leg.
(1) At or below 14,000 feet MSL: 1 minute.
(2) Above 14,000 feet MSL: 11/2 minutes.
NOTE-
The initial outbound leg should be flown for 1 minute or 1 1/2 minutes (appropriate to altitude). Timing for subsequent outbound legs should be adjusted, as necessary, to achieve proper inbound leg time. Pilots may use any navigational means available; i.e., DME, RNAV, etc., to ensure the appropriate inbound leg times.
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I'm just not seeing anything that suggests the pilot is permitted to shorten the pattern.​
In these cases, the controller will typically clear you to hold as published. If the hold is part of a HILPT on an approach chart, the clearance is usually just a clearance to for the approach, maybe with a report established inbound.
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If you're cleared to "hold as published", then the depicted leg length is part of your clearance, and I don't see any option to alter that pattern.

If the hold is not published, the controller will assign a distance or time as part of the clearance. This is binding on the pilot as it is included in the clearance.
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Agreed.

In 2010, it was clarified with the additional text to read as:
If the controller has an operational need for a charted hold to be flown at the maximum distance or time, they can include it as part of the clearance, in which case it would be binding on the pilot.
Click to expand...
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I don't see that as suggesting it may be shortened from the published or standard leg length.
 
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aterpster said:
No I didn't. That is not a requirement unlike RNAV. Doesn't mean you won't find them, but it is not policy on XXX/DME IAPs:

http://aeronav.faa.gov/d-tpp/1413/00344vd15.pdf
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It may not be a requirement to put distances on the holding patterns on those charts with DME in the title, but some do have it, and if it is there, then the AIM guidance I quoted above tells pilots to do it as published, i.e., to go out that published distance and then turn inbound. But on the chart you posted, since it says "1 Min", that means you time the outbound to get a one minute inbound leg, and there's nothing I can find which says it's OK to shorten that inbound leg.
 
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