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Old 17th Oct 2012, 07:10
  #53 (permalink)  
Nautilus Blue
Join Date: Aug 2007
Location: Running up that hill
Posts: 308
Any F100 drivers (Skywest/Alliance/Network) out there care to explain how you go about losing time enroute into Perth?

From what I can see, the F100 flies a very slow cruise (220KIAS or less) then into 250kts or more on descent, I.e. increasing speed from ToPD and a subsequently steeper descent profile.

On the 737, if possible we try and spread the delay across the cruise and descent (220/230 kts for both if down low enough and copping a really big delay). if following an F100 into Julim, we tend to catch you guys around about our planned descent point, then cop a vector off track in order to get a descent clearance through your level until you start going down. No drama really, just curious.

Also, do you ATC guys notice it too and are there plans for more standardisation across different types - aircraft performance permitting.
Last question first, about 12 times a shift, and no.

F100s seem slow down a lot more on cruise than 737's, but not below descent speed. Typically in terms of ground speed (which is what I'm most concerned with as an ATC) they seem to be constant cruise and descent, whereas 737s (particularly Qantas) will lose most of the time in the descent. At TOD a 737 will often look to be anything up to 4-5 minutes early based on groundspeed, which is why we nag about making your time. Sometimes this means you have actually overtaken the aircraft you are supposed to be following. The 737 can't have descent until it's 5 miles behind, it won't get 5 miles behind until it slows down, and it can't slow down until it descends.

It's also not just different types but different companies. A Qantas 737 behind a Virgin 737 will result in exactly the same problem. As we can see this coming 150+ miles out, I used to suggest the whichever aircraft was second to lose as much time as possible during cruise, but gave up.

In summary, two aircraft on the same STAR with FF 2 minutes apart will as often as not require vectoring or step deent even if both are exactly on time.

As an aside, when we used to vector and use speed to in-trail the inbounds, 250 KIAS was considered the minimum we could reduce an aircraft to. If you really stuffed up the vectoring you could ask for 240, 230 if you were desperate. Also, it was always taught that making an aircraft speed up again after slowing down was a cardinal sin. When we went to pilot adjusted fix times, with 250 from the fix, it never occurred to most of us that you would slow down to below 250, and than speed up again at the fix.

Edited to ask : Capn Bloggs is that near MRW, and why distance GEL? I didn't think the airline I thought you flew for went there?

Last edited by Nautilus Blue; 17th Oct 2012 at 07:18.
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