Variation on holding pattern entries

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Seems like this has the potential to generate a lively discussion. We'll see.

I'll start with this quote about holding pattern entries from Rod Machado's "Instrument Pilot's Survival Manual". My copy was printed June 15, 1998.

"Perhaps the most important thing to understand about entries is that in the real world, it makes little difference how the pattern is entered. In real life IFR flying the most important thing to do is to keep the airplane within the protected holding pattern airspace during the entry. It makes absolutely no difference to the controller whether a pilot uses the AIM prescribe entry or an 'inverted whifferdill' entry with a full twisting dismount and difficulty factor of 4.9."

I've always kept this idea in mind as a backup when flying slow GA aircraft (e.g. 150 KIAS or less) in case I'm given a surprise hold with little warning.

In the old days, when hold entries were first designed, only bearings (and sometimes distances) to fixes were available to the pilot. With currently available equipment, graphic displays of predicted holding track based on aircraft performance and position are available. In thinking about these changes, a modification of the parallel entry has occurred to me. This could be applied to a portion of, or the entire area currently allotted to parallel entries. It would only make sense for aircraft equipped with GPS navigators with graphic displays.

An example is shown in the first Garmin simulator screen shot below. The AIM prescribed parallel entry is depicted by arrows, and the underlying holding pattern track by the dotted line. The distance between outbound and inbound legs is computed in real time by the GPS navigator -- presumably based on ground speed and a standard rate turn.

FAA requirements on protected holding airspace mean the protected airspace will extend more than 3nm on all sides of the holding fix. I believe the actual minimum is closer to 3.5nm, but in any case it is at least 3.0nm. This is based on the link below.

https://aviation.stackexchange.com/...protected-space-provided-by-a-holding-pattern

The aircraft is only 2.3 miles from the fix at this point, so why not turn directly onto the outbound leg here? The result is shown in the second screen shot below. It seems to me there's no danger of leaving protected holding space in doing this. It simplifies the holding entry significantly, thereby reducing pilot workload.

To make this a little more scientific, let's limit the maximum ground speed for this idea to 180 knots. I chose that because the standard rate turning radius is then 1.0nm, and it places the outbound leg 2nm from the inbound leg. By the same logic, the aircraft would need to begin the turn to outbound leg 1.0nm before reaching it, which would be 3.0nm prior to the holding fix. This is still well within the protected airspace.

Going by the Machado quote above, this is idea perfectly acceptable. At first blush, it seems reasonable to me for slow GA aircraft (e.g. ground speed below 180kts), but what other issues and concerns have I failed to consider? I'm also sure there will be a lot of different and likely strong opinions on this topic. I'm curious to see what others think.
 

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Seems like this has the potential to generate a lively discussion. We'll see.

I'll start with this quote about holding pattern entries from Rod Machado's "Instrument Pilot's Survival Manual". My copy was printed June 15, 1998.

"Perhaps the most important thing to understand about entries is that in the real world, it makes little difference how the pattern is entered. In real life IFR flying the most important thing to do is to keep the airplane within the protected holding pattern airspace during the entry. It makes absolutely no difference to the controller whether a pilot uses the AIM prescribe entry or an 'inverted whifferdill' entry with a full twisting dismount and difficulty factor of 4.9."

I've always kept this idea in mind as a backup when flying slow GA aircraft (e.g. 150 KIAS or less) in case I'm given a surprise hold with little warning.

In the old days, when hold entries were first designed, only bearings (and sometimes distances) to fixes were available to the pilot. With currently available equipment, graphic displays of predicted holding track based on aircraft performance and position are available. In thinking about these changes, a modification of the parallel entry has occurred to me. This could be applied to a portion of, or the entire area currently allotted to parallel entries. It would only make sense for aircraft equipped with GPS navigators with graphic displays.

An example is shown in the first Garmin simulator screen shot below. The AIM prescribed parallel entry is depicted by arrows, and the underlying holding pattern track by the dotted line. The distance between outbound and inbound legs is computed in real time by the GPS navigator -- presumably based on ground speed and a standard rate turn.

FAA requirements on protected holding airspace mean the protected airspace will extend more than 3nm on all sides of the holding fix. I believe the actual minimum is closer to 3.5nm, but in any case it is at least 3.0nm. This is based on the link below.

https://aviation.stackexchange.com/...protected-space-provided-by-a-holding-pattern

The aircraft is only 2.3 miles from the fix at this point, so why not turn directly onto the outbound leg here? The result is shown in the second screen shot below. It seems to me there's no danger of leaving protected holding space in doing this. It simplifies the holding entry significantly, thereby reducing pilot workload.

To make this a little more scientific, let's limit the maximum ground speed for this idea to 180 knots. I chose that because the standard rate turning radius is then 1.0nm, and it places the outbound leg 2nm from the inbound leg. By the same logic, the aircraft would need to begin the turn to outbound leg 1.0nm before reaching it, which would be 3.0nm prior to the holding fix. This is still well within the protected airspace.

Going by the Machado quote above, this is idea perfectly acceptable. At first blush, it seems reasonable to me for slow GA aircraft (e.g. ground speed below 180kts), but what other issues and concerns have I failed to consider? I'm also sure there will be a lot of different and likely strong opinions on this topic. I'm curious to see what others think.

I agree with your logic. If you are in Radar Contact you could freak out a Controller doing that though if he’s running things kind of close and is expecting you to go to the fix before starting turns.
 
Seems like this has the potential to generate a lively discussion. We'll see.

I'll start with this quote about holding pattern entries from Rod Machado's "Instrument Pilot's Survival Manual". My copy was printed June 15, 1998.

"Perhaps the most important thing to understand about entries is that in the real world, it makes little difference how the pattern is entered. In real life IFR flying the most important thing to do is to keep the airplane within the protected holding pattern airspace during the entry. It makes absolutely no difference to the controller whether a pilot uses the AIM prescribe entry or an 'inverted whifferdill' entry with a full twisting dismount and difficulty factor of 4.9."

I've always kept this idea in mind as a backup when flying slow GA aircraft (e.g. 150 KIAS or less) in case I'm given a surprise hold with little warning.

In the old days, when hold entries were first designed, only bearings (and sometimes distances) to fixes were available to the pilot. With currently available equipment, graphic displays of predicted holding track based on aircraft performance and position are available. In thinking about these changes, a modification of the parallel entry has occurred to me. This could be applied to a portion of, or the entire area currently allotted to parallel entries. It would only make sense for aircraft equipped with GPS navigators with graphic displays.

An example is shown in the first Garmin simulator screen shot below. The AIM prescribed parallel entry is depicted by arrows, and the underlying holding pattern track by the dotted line. The distance between outbound and inbound legs is computed in real time by the GPS navigator -- presumably based on ground speed and a standard rate turn.

FAA requirements on protected holding airspace mean the protected airspace will extend more than 3nm on all sides of the holding fix. I believe the actual minimum is closer to 3.5nm, but in any case it is at least 3.0nm. This is based on the link below.

https://aviation.stackexchange.com/...protected-space-provided-by-a-holding-pattern

The aircraft is only 2.3 miles from the fix at this point, so why not turn directly onto the outbound leg here? The result is shown in the second screen shot below. It seems to me there's no danger of leaving protected holding space in doing this. It simplifies the holding entry significantly, thereby reducing pilot workload.

To make this a little more scientific, let's limit the maximum ground speed for this idea to 180 knots. I chose that because the standard rate turning radius is then 1.0nm, and it places the outbound leg 2nm from the inbound leg. By the same logic, the aircraft would need to begin the turn to outbound leg 1.0nm before reaching it, which would be 3.0nm prior to the holding fix. This is still well within the protected airspace.

Going by the Machado quote above, this is idea perfectly acceptable. At first blush, it seems reasonable to me for slow GA aircraft (e.g. ground speed below 180kts), but what other issues and concerns have I failed to consider? I'm also sure there will be a lot of different and likely strong opinions on this topic. I'm curious to see what others think.

AIM 5-3-8 j. 7. and 8. has a good read on GPS navigators, how they can be inaccurate regarding holding, and what you should do about it. Few pages long, but worth the read.
 
Are you using distance to the fix and some simple geometry to determine the appropriate time to start the turn outbound (legal) or are you using your moving map to determine the appropriate time (probably not legal—definitely not with the systems I have)?
 
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I agree with your logic. If you are in Radar Contact you could freak out a Controller doing that though if he’s running things kind of close and is expecting you to go to the fix before starting turns.
Would be nice to hear from a controller or two about that if any are reading this.
 
Are you using distance to the fix and some simple geometry to determine the appropriate time to start the turn outbound (legal) or are you using your moving map to determine the appropriate time (probably not legal—definitely not with the systems I have)?

This is all just a new idea, so a work in progress. I think you would need to use the GPS-displayed distance to fix to make sure your'e no farther away than 3nm before turning, but then using the moving map as situational awareness to get onto the outbound leg. Furthermore, would need to keep an eye on distance to fix on outbound leg, I guess.

I just had a GTX 375 installed, and it paints the hold according to A/C ground speed, but older units may not do that. This idea would be limited to those which adjust the depicted hold according to ground speed.
 
AIM 5-3-8 j. 7. and 8. has a good read on GPS navigators, how they can be inaccurate regarding holding, and what you should do about it. Few pages long, but worth the read.

Thanks for the tip. I'll go read it now.
 
This is all just a new idea, so a work in progress. I think you would need to use the GPS-displayed distance to fix to make sure your'e no farther away than 3nm before turning, but then using the moving map as situational awareness to get onto the outbound leg. Furthermore, would need to keep an eye on distance to fix on outbound leg, I guess.

I just had a GTX 375 installed, and it paints the hold according to A/C ground speed, but older units may not do that. This idea would be limited to those which adjust the depicted hold according to ground speed.
Mine adjust the depicted hold according to ground speed, but primary navigation using a moving map is still prohibited.
 
lufvlyin, that was a very good pointer (to the AIM). I'm glad I looked into this before using the new GNX 375 in the air, and I've a new appreciation for how to use it during holds. Luckily, none of this was an issue with my old GPS 155 TSO because it didn't have a graphical display.

My conclusion is that in general, it's not okay to do what I was suggesting. It would probably work just fine if winds aloft are calm, but trying to figure out a threshold would not be easy or wise. This is because the FAA computes the protected airspace based on how the hold is flown and adjusted for wind. Flying the graphical hold depected on the GPS is not compatible with these computations.

Also discovered: the GPS can identify the wrong entry if the winds aloft are strong enough because it uses your ground track, but the choice should be based on the aircraft heading. Didn't know that either.

The takeaway I got from this is that when executing holds, the GPS should only be used for the following tasks:

1) Identifying the hold point.
2) Identifying abeam the fix after turning to outbound leg.
3) Tracking the inbound leg.
4) Terminating the outbound leg when a leg distance is specified. Other than that, the outbound leg s/b timed from the abeam point, and adjusted to achieve the desired leg time inbound.
5) Situational awareness -- i.e. making sure that you're not doing something stupid and keepin track of the general big picture.

Specifically, it seems the GPS should not be used for:

1) Tracking the outbound leg.
2) Terminating the outbound leg when the inbound leg is timed.

When winds aloft are strong, it might be a good idea to double check the entry suggested by the GPS against your actual heading.

There's nothing about any of this in the GNX 375 Pilot's Guide or the AFMS.
 
If you fly over the fix in TD/Parallel entry and just do a split S down to holding altitude while pointing back at fix, problem solved. Boom, new entry method
 
Ha, good point. Except then I'd have to buy a parachute and an airplane that can actually do a split S. :(
 
Several years ago I constructed five templates in my GIS program. P4 (the smallest used in TERPs), P9, P15, P25, and P30. Holding at LAX VOR on the 076 radial, right turns. The file is too large to post here, but it is in my FTP directory:

http://www.wallyroberts.com/holding/laxholds.pdf

For instrument flight procedures, there would be an additional 2 mile secondary area. I show only the primary areas.
 
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