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Parallel entry procedure different to how it should be flown!

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It seems the 737NGX executes the parallel entry different to how it should be performed. Is this a known problem?

 

ICAO DOC 8168

 

Sector 1 procedure (parallel entry):

 

(a) at the fix, the aircraft is turned left onto an outbound heading for the appropriate period of time (see 1.4.9, “Time/distance outbound”); then

 

(b) the aircraft is turned left onto the holding side to intercept the inbound track or to return to the fix; and then

 

© on second arrival over the holding fix, the aircraft is turned right to follow the holding pattern.

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It seems the 737NGX executes the parallel entry different to how it should be performed. Is this a known problem?

 

It's a known issue, yes. That said, the only requirement is that the hold is flown on the protected side. There is no such thing as a required hold entry. I can teardrop instead of parallel if I prefer it.

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It's a known issue, yes. That said, the only requirement is that the hold is flown on the protected side. There is no such thing as a required hold entry. I can teardrop instead of parallel if I prefer it.

 

Thanks kyle for clearing that up. Of course depending on what direction you enter on

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Of course depending on what direction you enter on

 

You can enter a hold however you'd like. The officially-accepted ones, of course, are the ones you know. If my approach angle called for a parallel, I could fly a tear if I wanted to. There is regulatory guidance, but there is no regulatory prescription.

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Hmm i thought your heading determines what sector you are in and the sector entry to fly?

 

ICAO DOC 8168

 

1.4.1 The entry into the holding pattern shall be according to heading in relation to the three entry sectors shown in Figure I-6-1-2, recognizing a zone of flexibility of 5° on either side of the sector boundaries.

 

Unless i'm mistaken?

To add, does the NGX always use parallel entry if not coming in the direct sector?

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Unless i'm mistaken?

 

Note the note. Some areas - the US included - do not require specific entries. As far as the controller is concerned, you're the only person allowed to be in that hold at that altitude, so it doesn't need to be one way or the other. If anything, you're afforded more room for maneuvering on the hold (protected) side than the unprotected side (where you'd be flying the parallel). Granted, you have a decent amount of room on the unprotected side as well, but it's all what you prefer. Nobody is going to chase you down for using one versus the other.

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Ok no worrys. Have you done any sector entrys in real life? If so, do you draw the 3 sector entrys on your kneeboard and decide the best method to cross the fix?

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Have you done any sector entrys in real life?

 

More than I'd like to remember. The middle and end of my instrument rating was all holds and approaches. One of the local holding fixes is above a ridge line. If it's windy, you get tossed around quite a lot.

 

 

 

If so, do you draw the 3 sector entrys on your kneeboard and decide the best method to cross the fix?

 

Nope. I just look at the chart and eyeball it with a mindset of "what's the easiest way to do this?"

 

Using the aforementioned approach, I routinely did a direct entry off of the LDN 058 radial (inbound from JASEN - I know it's a NoPT IAF, but we were routinely asked to hold there to show our ability to fly one). It's properly a parallel entry, but to me, it's borderline enough that I just go direct. If I were approaching from the opposite side, I'd just teardrop it. Parallel entries, properly flown, spend a lot of time away from a specific radial that I can effectively judge my course correction for wind with in non-GPS aircraft (rare, but I do fly them on occasion). Brief it so you're both aware of what's going to happen, and then fly it.

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If so, do you draw the 3 sector entrys on your kneeboard and decide the best method to cross the fix?

 

I was taught to use the HSI to gauge entry selection.  I agree with Kyle, best to choose the entry that looks easiest to execute.  I remember watching F-4 fighters hold at Heidelberg for entry to Ramstein on the scope and those guys are lucky to keep that bird in the vicinity of the fix LOL. Saw all kinds of patterns. Regardless, you have a piece of protected airspace and you want to stay in it.

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Thanks guys for helping out. That seems challenging doing that hold kyle at LDN? I hope you never done that in turbulence and high winds? it does help alot drawing the fix and inbound standard right turns, but i know what you mean by eyeballing it, saves a bit of time.

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That seems challenging doing that hold kyle at LDN?

 

The hold is at CLADD, which is defined by LDN's 058 radial and the LOC at KOKV. Coming in from JASEN, you follow R058 until the LOC starts coming in and swing around into the hold (with whatever entry you prefer), and then once you're back inbound on the LOC, LDN R058 swinging indicates your passage of CLADD.

 

 

 


I hope you never done that in turbulence and high winds?

 

I've done it in both. The ridge usually causes the latter due to the former.

 

 

 


it does help alot drawing the fix and inbound standard right turns, but i know what you mean by eyeballing it, saves a bit of time.

 

Yeah, when flying single pilot, you really have to prioritize things, particularly if you're in a plane without an AP.

 

If you're approaching a hold do you:

  • Divert your attention away from flying the plane to draw a diagram, or focus intently on the angles of approach to the hold; or
  • Take a quick look at it and come up with a quick plan of attack?

With an autopilot you do have a little more bandwidth, but it really doesn't gain you much in certain circumstances. Say you're approaching the fix at the 109 degree mark (off of the inbound course) - just inside the area where you should use a parallel entry. Direct or parallel? Did that math really help you there?

 

 

 

I used to get really focused on calculating everything out for my flights when I was in the beginning of training. I would keep the E6B up front in the pocket by my left knee so that I could run calculations just in case. Over time, I realized that so much of aviation is so imprecise that trying to be too precise was an exercise in futility.

 

Here's an example (KRDU's airspace for a 23L/R config):

Capture.PNG

 

Note the dashed heart-shaped (the anatomical version, not the Valentine's Day thing) sections. Those are holds. Note how they look nothing like what's depicted on the chart. Part of the reason for the bump-out on the outbound side is to account for any wind correction that may be necessary, and another part is for the increased possible error when on the outbound leg (since you don't have a specific course line to follow). The inbound side is the flat side, but that flat side is actually divergent from the inbound course line (allowing more protected airspace farther from the fix to account for any minor overshoots that occur when finishing the turn back inbound). You can see this most clearly at the top right of the image, since you can see two consecutive fixes (Xs) on the ARGAL STAR. Note that the flat edge of the holding area diverges from course line between ARGAL and MEYER (while both ARGAL and MEYER are holding fixes, the ARGAL hold is the one depicted on the scope - ARGAL is the closer X to the field). Additionally, note the margin of error you have on the holding/outbound side versus the inbound side. There's some room for a parallel entry, but your margin of error isn't as forgiving.

 

So, as precise as you want to be, there is going to be error in the end result, since there is error present in every facet of aviation: passengers don't all weigh 185, your mag compass is lying to you, your fuel tanks don't have exactly that much fuel in them, and so on.

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Just make sure you hold on the correct side of the fix. I remember during my instrument check ride the FAA examiner asked me to take us to the PVU VOR and hold southwest of the PVU VOR. I got so hung up trying to figure out what type of entry I would do into the holding pattern that I ended up holding southeast of the VOR where there were mountains. Done in a Cesna 172 he cut me a break, and said holding on the right side was far more important than the entry itself.

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The hold is at CLADD, which is defined by LDN's 058 radial and the LOC at KOKV. Coming in from JASEN, you follow R058 until the LOC starts coming in and swing around into the hold (with whatever entry you prefer), and then once you're back inbound on the LOC, LDN R058 swinging indicates your passage of CLADD.

 

Yeh i see it now, good stuff!

 

With an autopilot you do have a little more bandwidth, but it really doesn't gain you much in certain circumstances. Say you're approaching the fix at the 109 degree mark (off of the inbound course) - just inside the area where you should use a parallel entry. Direct or parallel? Did that math really help you there?

 

You could say that will be a direct entry?

 

Well thanks alot for the last part, i'm trying not to get bogged down but to only undestand the entry patterns and how the system works. It all stemmed from the NGX not doing the correct parallel entry.

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You could say that will be a direct entry?

 

I'd argue for direct, yeah.

 

 

 


It all stemmed from the NGX not doing the correct parallel entry.

 

haha - yeah, I was thinking that when I clicked on this thread just now. It's more than you'd ever need to know, but it could be useful in the future somehow.

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haha - yeah, I was thinking that when I clicked on this thread just now. It's more than you'd ever need to know, but it could be useful in the future somehow.

 

Exactly, but its still nice to know! Something else i've learn't in theory :) if i have anymore questions i'll bring it to this.

Just make sure you hold on the correct side of the fix. I remember during my instrument check ride the FAA examiner asked me to take us to the PVU VOR and hold southwest of the PVU VOR. I got so hung up trying to figure out what type of entry I would do into the holding pattern that I ended up holding southeast of the VOR where there were mountains. Done in a Cesna 172 he cut me a break, and said holding on the right side was far more important than the entry itself.

 

Good stuff ;)

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It says -

 

1.3.4 Start of outbound timing

 

Outbound timing begins over or abeam the fix, whichever occurs later. If the abeam position cannot be determined, start timing when the turn to outbound is completed.

 

Whichever occurs later? Should it not be whatever is earlier? Sorry if i'm missing the obvious but i can't see why later...

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Whichever occurs later? Should it not be whatever is earlier? Sorry if i'm missing the obvious but i can't see why later...

 

It's honestly just poorly written. Leave it to ICAO...

 

Basically, abeam a fix means you're on a parallel course, directly perpendicular to the fix. Over, of course, means over. For the hold entry, you're going to begin timing when you cross over the fix for your outbound timing, but when you're established in the hold, you use the abeam point. Basically, they took a pretty simple concept and made it much more complex than it needed to be.

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It's honestly just poorly written. Leave it to ICAO...

 

Basically, abeam a fix means you're on a parallel course, directly perpendicular to the fix. Over, of course, means over. For the hold entry, you're going to begin timing when you cross over the fix for your outbound timing, but when you're established in the hold, you use the abeam point. Basically, they took a pretty simple concept and made it much more complex than it needed to be.

 

Its from ICAO DOC 8168. Its all enough to put you to sleep. Ok great thats what i thought.

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The wind will wreck havoc with all this theory. It doesnt matter really how much more time within reasonable limits you employ, aircraft airspeed is different also. Main thing is to hold in the proper quadrant and be precise in the standard rate turns. The outbound leg is pretty much the one to be timed, but covered terrain will vary greatly with conditions and type aircraft. Do it economically so as to save fuel as much as possible.

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Check the US AIM this November for  new, expanded guidance on holding.  Much of will address the way RNAV systems fly holding, the design of which is all predicated on original conventional holding criteria promulgated in the early 1960.

 

One thing that was learned, the recommended holding entries are actually more-or-less required for airspace containment since the fix end protected airspace is predicated on using a turn in the shortest direction to the outbound heading.  The use of parallel or teardrop sectors ensure that the turn is made in the shortest direction.

 

Rich Boll

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