Werner747

How to properly do a holding pattern in the 747-400

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Hi everyone,

Okay - so...   I have recently started to dip into the abnormal procedures and getting some practice done on that (which is a lot of fun btw).   Here is the scenario first.

I do a medium fuel and normal payload takeoff with a properly loaded route and VNAV/LNAV profile loaded into the FMC as if I am flying a route.   The aircraft is then setup to lose an engine at V1.   So that part is easy enough, follow the engine out procedure, but now because of the medium fuel load, I am overweight and need to dump some fuel to get within landing parameters.

So I had to the assigned fuel dumping area which is off the path of the magenta line obviously, so I engage heading select to fly off and alt hold mode and head off to the dump site.   Now the idea is to setup a PPOS holding point in the FMC to hold and dump fuel until I can return.   The setup all goes well, the aircraft will enter the hold without issues (by default a right hand turn obvioulsy).   I do this by switching on LNAV and it enters the pattern just fine, does the downwind leg and the moment it needs to turn right again to return to the waypoint and complete the track, it turns left and out of the pattern.   and from there does all sort of weird maneuvers but never properly enters the pattern again.  

What am I doing wrong here?   Can anybody assist?

TIA

 

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37 minutes ago, downscc said:

Most likely this is related to how you are entering the pattern.  There are three different entry methods depending on your entry heading in relationship to the inbound holding course.  See https://en.wikipedia.org/wiki/Holding_(aeronautics)

He entered into the hold in LNAV.  Computer logic should determine the appropriate hold entry.  But it also sounds like the second turn so the entry is over.  It should just follow the magenta line.

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1 hour ago, thibodba57 said:

He entered into the hold in LNAV.  Computer logic should determine the appropriate hold entry.  But it also sounds like the second turn so the entry is over.  It should just follow the magenta line.

I thought it was possible he entered a parallel entry in which case the turn inbound is the opposite direction of the turn inbound once established.  He didn't provide the inbound holding course nor his heading approaching the hold.

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2 hours ago, Werner747 said:

it turns left and out of the pattern

Do you mind taking some pictures and explain what you think it might be wrong please.

As to landing overweight, it is no problem doing so in interest of safety (but rwy lengths should be taken in account, you need to stop on that concrete, FAA or ICAO requirements don't apply if is an emergency or for safety req. One engine out is should not be a concern unless is a fire, severe damage etc....) At the end it will require an overweight landing inspection performed by the MX.

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1 hour ago, downscc said:

I thought it was possible he entered a parallel entry in which case the turn inbound is the opposite direction of the turn inbound once established.  He didn't provide the inbound holding course nor his heading approaching the hold.

He said he did a PPos hold.  Granted he didn't elaborate if he programmed a different Inbound Course, my assumption is no as he mentioned the right turn.  A PPos hold will do a direct entry and the inbound course will automatically be slaved to the current CRS being flown.  So it should make an immediate right turn and right turns forever after.

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5 hours ago, Werner747 said:

What am I doing wrong here?   Can anybody assist?

The main problem is you are trusting the magic.  If you see the aircraft is turning the wrong direction, go into HDG SEL and make the aircraft turn the direction that you need it to turn.  Entering Holding is not as complicated as a lot of folks want to make it seem.  Just make sure that when entering holding to make all turns on the holding pattern side.  For example if a course reversal is necessary to enter holding just make the turn toward the holding pattern and track bad to the holding fix.  ATC really doesn't care how the pilot gets established in holding as long as the aircraft remains within the holding pattern as cleared.  

Always remember never trust the magic. 🙂

Grace and Peace,  

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6 hours ago, thibodba57 said:

He said he did a PPos hold.  Granted he didn't elaborate if he programmed a different Inbound Course, my assumption is no as he mentioned the right turn.  A PPos hold will do a direct entry and the inbound course will automatically be slaved to the current CRS being flown.  So it should make an immediate right turn and right turns forever after.

This was going to be my comment as well. It’s a PPos hold and he stated that he used a standard right hand turn. This is as easy as it gets, no maneuvering required for entry. It should just start making right hand turns assuming that he is activating it correctly. 

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When you do get it sorted stick in something like 10Nm or 20nm legs rather than the standard 1 minute leg or you’ll end up with a face full of your own jet fuel.

When I had to dump fuel in the real jet we were just allowed to self manoeuvre up and down the coast line while we dropped 65T of gas. That was a similar scenario to the one you’re using, lost an engine , number 3,between V1 and VR curtesy of a flock of seagulls (not the 80’s pop group)

Cheers

Jon Bunting

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Lots of good information for folks in this thread! 

One thing I haven't seen mentioned is to consult the charts for hold parameters.  Such information doesn't exist for all Hold Patterns, but it does exist on the charts for many of them.

Best wishes to everyone!

 

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On 11/28/2018 at 9:02 PM, Werner747 said:

Now the idea is to setup a PPOS holding point in the FMC to hold and dump fuel until I can return. 

Who knows, maybe the PMDG 744 is clever enough not to allow you to do this? 

Seriously, the first thing you are doing wrong is planning to jettison fuel in a standard holding pattern because you should never dump fuel whilst holding (areas of lightning discharge, static and heavy precipitation should also be avoided). The second point is if you need to hold you should ideally do so over a known FIX rather than a PPOS, because the FMC will then limit the size of the displayed holding pattern to a maximum size that is less than either the FAA or ICAO holding pattern criteria for the appropriate protected airspace. 

However, I think your airspeed is probably too high for the hold and this might go some way to explain the strange holding pattern behaviour you are seeing,  You said the aircraft is overweight and I am assuming here that the aircraft is clean, so your airspeed is likely to be be significantly higher than the normal FMC constraint speed, even allowing for the fact that it will still attempt to fly the displayed holding path using a bank limit of up to 30 degrees.  In this case it is perhaps worth noting that no message is given by the FMC if the displayed hold cannot be flown by the aircraft because it is unable to follow the computed path.  It will simply give up the ghost as far as the hold is concerned and that is why you should always monitor the lateral trend vector and be prepared to take over control (e.g. HDG Mode) at any time the aircraft fails to follow the computed path.         

 

Edited by berts

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13 hours ago, berts said:

Who knows, maybe the PMDG 744 is clever enough not to allow you to do this? 

Seriously, the first thing you are doing wrong is planning to jettison fuel in a standard holding pattern because you should never dump fuel whilst holding (areas of lightning discharge, static and heavy precipitation should also be avoided). The second point is if you need to hold you should ideally do so over a known FIX rather than a PPOS, because the FMC will then limit the size of the displayed holding pattern to a maximum size that is less than either the FAA or ICAO holding pattern criteria for the appropriate protected airspace. 

However, I think your airspeed is probably too high for the hold and this might go some way to explain the strange holding pattern behaviour you are seeing,  You said the aircraft is overweight and I am assuming here that the aircraft is clean, so your airspeed is likely to be be significantly higher than the normal FMC constraint speed, even allowing for the fact that it will still attempt to fly the displayed holding path using a bank limit of up to 30 degrees.  In this case it is perhaps worth noting that no message is given by the FMC if the displayed hold cannot be flown by the aircraft because it is unable to follow the computed path.  It will simply give up the ghost as far as the hold is concerned and that is why you should always monitor the lateral trend vector and be prepared to take over control (e.g. HDG Mode) at any time the aircraft fails to follow the computed path.         

 

thanks for the reply, I do slow the aircraft down to 230 knots with about 5 degrees of flap so it should easily be able to hold the pattern.   What it does is not try to fly an erratic pattern with right hand turns trying to stay inside the hold at high speed.   It turns left, away from the racetrack pattern.   That is not normal.  

 

On 11/29/2018 at 5:03 AM, Bluestar said:

The main problem is you are trusting the magic.  If you see the aircraft is turning the wrong direction, go into HDG SEL and make the aircraft turn the direction that you need it to turn.  Entering Holding is not as complicated as a lot of folks want to make it seem.  Just make sure that when entering holding to make all turns on the holding pattern side.  For example if a course reversal is necessary to enter holding just make the turn toward the holding pattern and track bad to the holding fix.  ATC really doesn't care how the pilot gets established in holding as long as the aircraft remains within the holding pattern as cleared.  

Always remember never trust the magic. 🙂

Grace and Peace,  

thanks for the reply, thing is I am not just sitting back and trusting the magic to happen, I just want to know why others are getting the patterns flown and my aircraft doesn't want to :-).   So in essence, this being a learning curve, I want to know WHY it is not doing it so that I can get it right in future. I haven't had the time to return to the problem just yet, but will play with it a bit over the weekend.

Thanks for all the replies, I am giving it another go this weekend so will keep everyone updated on how it goes :-)

 

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