Stoney
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Joined: Fri Jan 14, 2005 2:37 am

Different Cruising Speeds On Airways

Thu Oct 20, 2005 6:35 am

Aloha

In our theory classes for the PPL we just talked about radio navigation, radarstuff and ATC. Now the instructor mentioned something which got my attention.

Apparently there isn't any ATC-surveillance over open ocean (At least no civil radar coverage). The planes are just assigned slots, meaning that they have to be at a certain point in space at a certain time and that they are assigned a certain speed which they have to use until they are in a ATC-controlled airspace again. This guarantees a certain spacing between the different planes.

As everybody gets told 1000 times on A.net, Boeings generally have a higher optimal cruisespeed than the Buses. So do planes from B have a different Airway than planes from A where all the planes on there fly faster, or does one of them just have to fly with a suboptimal speed? Or does everyone just fly as fast as they want and look out after themselves?

Greetz and thanks for the answers

Stoney
BAZL - Bundesamt gegen Zivilluftfahrt - royally screwing around with swiss aviation
 
SlamClick
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Joined: Sun Nov 23, 2003 7:09 am

RE: Different Cruising Speeds On Airways

Thu Oct 20, 2005 7:25 am

Quoting Stoney (Thread starter):
Or does everyone just fly as fast as they want and look out after themselves?

Different situation in so-called "random nav" routes over the more remote oceans but the answer is an emphatic NO for the North Atlantic Tracks between Europe and North America. Also NO for the routes from, say, the New York area down to the eastern Caribbean. Speed will be assigned.

You will file for a given mach number over a given track. Most of the time you will get what you ask for but safe to say that everyone on Track Y at FL380 tonight is maintaining .80M for example. It is safe to space by mach number because it is driven by temperature. Thus if you fly into colder air and your speed decreases, so will the speed of the plane following you when he gets into that air mass.

I presume that they (Gander and Shanwick) have tracks or altitudes for faster or slower planes and they might change your track or flight level if you are going to be asking for a significantly higher or lower speed.

The other thing at work here is position reports. If we are doing them at, say, every ten degrees of longitude, then any bunching-up is going to be apparent pretty quickly. Especially true with automated satellite-link position reports. I would imagine that information can be processed quicker.

Lots of guys on this forum with more bluewater experience than I have. Perhaps one of them will jump in.
Happiness is not seeing another trite Ste. Maarten photo all week long.
 
PhilSquares
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RE: Different Cruising Speeds On Airways

Thu Oct 20, 2005 1:09 pm

Quoting Stoney (Thread starter):
Apparently there isn't any ATC-surveillance over open ocean (At least no civil radar coverage).

Many years ago that used to be the case, however, it's not quite like that any more.

Your "oceanic" clearance in the N. Atlantic includes a MN. ATC will try to sequence similar speed aircraft on the same track or at least the same altitude. But, that's not always possible. In that case, you might be asked, if you're in an Airbus to maintain a relative fast MN and if you're flying a Boeing, you might be asked to maintain a slow MN.

In the NOPAC, there is radar coverage westboune out past Shemya, so normal radar spacing is applicable. But again, a MN could be part of your clearance and in that case you'd have to comply. In the NOPAC, there isn't quite as much of a problem since most traffic is either the 744 or 777 and they are quite compatible.

In the NAT, depending on where the tracks are located, you might have radar coverage. In addition, with the introduction of CPDLC/ADS, you have essentially radar coverage with those aircraft that have FANS.
Fly fast, live slow
 
Stoney
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Joined: Fri Jan 14, 2005 2:37 am

RE: Different Cruising Speeds On Airways

Thu Oct 20, 2005 8:21 pm

Thanks for the answers! Lots of interesting information clearing up my questions.

Greetz

Stoney
BAZL - Bundesamt gegen Zivilluftfahrt - royally screwing around with swiss aviation

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