View Full Version : Airlines in the FIR

Evil J
2nd Feb 2003, 14:39
As an ATCO that frequently works traffic coming back to the UK through the open FIR can I make a plea...please please do not keep asking me to lift the speed restriction below FL100. ATC IN CLASS G AIRSPACE DO NOT HAVE THE AUTHORITY TO LIFT THIS SPEED RESTRICTION.

Thank you and sorry to those of you that knew that but so many crews don't seem to be aware.

2nd Feb 2003, 16:50
E J may I just add a rider to what you say for those who may read this. not all in the FIR have a radar service and higher speeds may present unseen dangers to many airspace users. Why do the pilots need more speed? A simple question no doubt and some may care to enlighten us who frequent the FIR in slower a/c

2nd Feb 2003, 17:28
I htought that most had company policy (bird penetration speed?) of not greater than 250kts below FL100 even if in CAS.

Or maybe that applies to only certain type, such as the 146 (?).

2nd Feb 2003, 18:45
The fleet I’m on has a restriction of 313kts below FL80 for bird strike protection.

250 KTS is normaly an ATC restriction and one that we’re all keen to avoid if possible.

We want to reduce the fuel burn with a continuous descent using FMC ECON descent profiles that are in the order of .80/301KTS. Ideally we want to fly so that we stand the thrust levers up at 1000/500’ in the “slot” without any level flight or speed reduction consistent with ATC requirements.

This profile also reduces the noise footprint in the local area around the airfield.

Max Angle
2nd Feb 2003, 19:54
In fact you will find that slower descent speeds use LESS fuel than high ones, you spend less time in the cruise and more time with the levers at idle the slower you descend. The cost index that generates the speeds takes into account total operating cost and may use a faster descent speed to decrease the time spent in the air.

2nd Feb 2003, 20:45
Max Angle I’m sure you’re correct. Several glasses of red have got me a bit too relaxed. :=

We tried slow descent speeds for a few years and found this often resulted in a requirement for thrust during descent to maintain target speed. This resulted in extra fuel being burned. You are absolutely right about the FMC index, I forgot to mention it in my rather poor explanation…thanks for the reminder. :O

Evil J
3rd Feb 2003, 09:01
Working Hard-thats the whole point of the speed restriction, to enable the "see and avoid" principle to work. Even where there is radar coverage, radar does not, by any means see everything. This is really the whole point of this post, to alert the crews to the fact that if the want to come through the FIR fine, but they need to accept that they will not be as protected as if they come airways.

As Max_cont demonstrates is his post above, thay are all looking to avoid the speed restricrtion in the FIR. The only way this can be done is by staying above FL100, or applying to the CAA for a dispensation! Asking ATC is not a way of getting it lifted as, like I said at the start we do not have the authority to lift it. Even if we say "no speed" or "stay high Speed" that still doesn't alleviate the pilot from complying with this rule. All we can inform the pilot is that there is "no ATC speed control" ie tactical speed reduction (for sequencing purposes)

4th Feb 2003, 07:53
And indeed, ATC also can't lift the 250kts/FL100 in Classes E&F as well.
AIC Yellow 35/1998 (291) (http://www.ais.org.uk/aes/pubs/aip/pdf/aic/4Y291.PDF), 2.4.1 & 2.4.2
Some of the airspace around BFS, and parts of the Scottish TMA are Class E - so there is also a potential 'gotcha' if you're approaching EDI/GLA/BFS at 320kts!

Evil J
4th Feb 2003, 08:00
Thanks Zulu. I guess thats for the same reason. If you don't know what's out there the see and avoid principle is the last back stop preventing a nasty, therefore high speed degrades the opportunity for see and avoid to work.

4th Feb 2003, 08:27
Exactly - as you know, Classes G, F & E aren't known traffic environments, so see and avoid is really your separation, even if radar is available.
In our company we have a mandatory limit of 250kts below FL100, regardless of type of airspace.
A bit of an old chesnut, but still quite true:
“It is better to arrive a few minutes late in this world, than to arrive several years early in the next.”