julesmusician
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Strange Holding Patterns - Is It Usual?

Fri Nov 25, 2005 5:06 am

Pilots,

The little diagram I have tried to draw today is of an unusual holding pattern that occured outside Heathrow.



There were at least four planes stuck in the usual hold (blue) and then two 747's came off the stack at what looked like the same height. The yellow one followed the red on in parallel until the yellow one then came back into the stack again.

Is it usual that if it becomes very busy air traffic will give strange requests and direct you to do something out of the ordinary?

J
African Civil Aviation Commission president "You don't want to fly out as a passenger and come back as cargo."
 
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Jetlagged
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RE: Strange Holding Patterns - Is It Usual?

Fri Nov 25, 2005 5:28 am

Was the yellow 747 holding in the opposite direction, or did it manage a 180 deg turn on a sixpence? I think a re-draw might be in order. Where's Rolf Harris when you need him  Smile

It might not actually have been in the hold when you saw it "leaving". It might still have been entering the pattern.
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AAR90
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RE: Strange Holding Patterns - Is It Usual?

Fri Nov 25, 2005 7:29 am

Nothing unusual. The red plane was cleared out of holding and proceeded to LHR. The yellow plane was cleared out of holding after the red plane and proceeded toward LHR, but that clearance was cancelled and it was directed back to the holding stack. Relatively common during high density operations in changing weather conditions.
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julesmusician
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RE: Strange Holding Patterns - Is It Usual?

Fri Nov 25, 2005 8:00 am

Changing weather conditions? How would that effect what order the planes go in?
African Civil Aviation Commission president "You don't want to fly out as a passenger and come back as cargo."
 
AAR90
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RE: Strange Holding Patterns - Is It Usual?

Fri Nov 25, 2005 8:49 am

Quoting Julesmusician (Reply 3):
Changing weather conditions? How would that effect what order the planes go in?

Marginal weather means planes are metered in as the weather dictates. Above minimums, start sending planes. While enroute, weather goes below minimums means stop sending the planes. If you've got no holding spots closer to the airport then you have to send planes back to where they were previously being held. If, by that time, ATC has filled the "hole" created by sending planes toward the field, you have to send the returning plane to a different altitude... and potentially a different inbound order of arrival. All-in-all, a very fluid situation.
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julesmusician
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RE: Strange Holding Patterns - Is It Usual?

Fri Nov 25, 2005 9:43 pm

But what happens if say you have a nasty storm right over the holding point? There are not many facilities I assume to ask pilots to hold somewhere that are not on approach plates or details as that would be "out of the norm" - what would you do in that situation?
African Civil Aviation Commission president "You don't want to fly out as a passenger and come back as cargo."
 
mandala499
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RE: Strange Holding Patterns - Is It Usual?

Sat Nov 26, 2005 4:05 am

Over here, when weather goes below minima, it's not unusual that it's a CB cloud near or over the field... most of the time it's very very bumpy cumulus with very very dense rain... and then, the holding pattern is over a VOR close to the airfield... What happens then?

ATC tells aircraft: "Hold at Radial XXX inbound at Y DME left/right pattern, Altitude."

Mandala499
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
julesmusician
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RE: Strange Holding Patterns - Is It Usual?

Sat Nov 26, 2005 8:00 am

Wouldn't it be far easier for them to give you GPS co-ordinates and holding around that, setting up that radial and DME pattern sounds like a lot of hard work!
African Civil Aviation Commission president "You don't want to fly out as a passenger and come back as cargo."
 
Woodreau
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RE: Strange Holding Patterns - Is It Usual?

Sun Nov 27, 2005 8:53 pm

Quoting Julesmusician (Reply 7):
Wouldn't it be far easier for them to give you GPS co-ordinates and holding around that

It's definitely much easier to do a hold off a navaid/radial/DME than it is off lat/long. Even with a FMS, the FMS is already set up to accept waypoint/radial/dme/direction of turns to set up a hold. To hold off a lat/long requires you to setup a user waypoint first before you enter the parameters in the hold page, that's at least 10 to 20 more button pushes before you can set up the hold.

Plus if you were ever on a receiving end of a lat/long / GPS coordinate over the radio, you'd probably want to kill the sender.

[Edited 2005-11-27 12:55:32]
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mandala499
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RE: Strange Holding Patterns - Is It Usual?

Sun Nov 27, 2005 10:03 pm

Wouldn't it be far easier for them to give you GPS co-ordinates and holding around that

Say you want to go into Jakarta, but bad weather prevails and you have to be put into a hold....

Now, a GPS coordinate and hold around that?
"Speedbird 999, maintain heading climb 7000, after reaching 7000, proceed to hold over S05 28.8 E106 54.3" (imagine hearing "South zero five, two-eight decimal eight, east one zero six five four decimal three")...

It's a mouthful... Then, put it into the FMS, U put in S0528.8E10654.3 which is 15 keys!

Now, how about using the radial and distance:
"Speedbird 999, maintain heading climb 7000, after reaching, proceed to hold over DKI radial 344 at 30 DME."

Now that takes about 1/2 the time to give the instruction. On the FMS, U just type in: DKI344/30 which is 9 keys, and probably 1 more key press as the FMC would ask you which "DKI" would you like to hold over... the nearest, or the furthest? or elsewhere?

Or even better... the Fix actually is a standard waypoint and has a name...
"Speedbird 999, maintain heading climb 7000, after reaching 700, proceed direct and hold over NOKTA"

You'd only have to put in 5 keys to enter the name, and 1 more if there's multiple selection.

So, giving the GPS coordinates for a holding ISN'T ideal! And in crowded airspace and bad weather, that's the last thing you want.

Furthermore, if that fix isn't ideal, ie, weather has moved into the fix, they can just say "how about 'FIX NAME'" or "How about DKI radial 090 at 20dme?" It's also quicker for everyone who hears the transmission to make a mental picture on where it is... and also quicker to find that spot on the map and in real life... and also in the FMC...

Now, a hold requires:
1. A Holding Point
2. Heading inbound to holding fix,
3. Left or right hand racetrack pattern (if not a 1 minute standard, then time has to be put in as part of the instruction)
4. Altitude

if we use the GPS coordinates, how do we know #2 ?
If we use the radial/dme method, it's only 2 guesses... 344 inbound to the fix, or 164 inbound to the fix, and most likely to be 164 inbound.

I hope this explains why...

Mandala499
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
AAR90
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RE: Strange Holding Patterns - Is It Usual?

Sun Nov 27, 2005 11:57 pm

Quoting Julesmusician (Reply 7):
Wouldn't it be far easier for them to give you GPS co-ordinates and holding around that, setting up that radial and DME pattern sounds like a lot of hard work!

Not all airplanes have GPS or FMS.
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