Gatwick spacing

[30W]

Zonoma,

Thanks for the time spent in such a comprehensive response and addition to the discussion!

I'm just off to bed prior some 'earlies' but will respond better at the end of the week

If all we're doing here is sharing thoughts, provoking discussion in the flight deck and in the canteen, then that's a good thing hopefully!

30W

[Dan Dare]

We've not ended up in the 'multiple' scenario you suggest, let's hope from both sides of the mic that we never do.

From my side of the mic I've had far too many 'multiple' scenarios, the worst of which have been from un-forecast and therefore un-flowed fog across the whole of the south east. You would not believe how quickly we run out of runways! It doesn't happen every month, but when it does they are memorable! When you've got 3 PANs and a Mayday all requiring a sterile runway and more delay for everybody else it concentrates the mind a bit. I can't imagine it's a barrel of laughs from up there either.

[Del Prado]

7. Several times last Summer was slowed to minimum speed at FIR entry by en-route due 15-20 minute delay expected at KK. On transfer to TC told no delay (yes, appreciate officially that means not greater than 20'). On query told no idea where 'next door' got that from and indeed on arrival not more than once round the hold, on several occasions 'straight off' without even a 'spin'.....

Doesn't that mean its working? ;-)

Ok, this response is slightly tongue in cheek but if delay is 15-20 and you slow down wouldn't you expect your delay to reduce? Maybe not 20 down to 0 but if you're still getting once round the hold or a spin then the early speed reduction was advisable and even when you came 'straight off' I bet there was enough traffic ahead to warrant 220kts or min clean so the speed control did its job to a large degree.

(With apologies for the overtly contrarian post)

[The Many Tentacles]

Originally Posted by 30W

Minimum fuel - The term used to describe a situation in which an aircraft’s fuel supply has reached a state where the flight is committed to land at a specific aerodrome and no additional delay can be accepted. (PANS-ATM, DOC 4444)

I was close.................ish

Thanks for the correction

[30W]

Hi DP,

Appreciate the devils advocate approach

Yes, you're right, it does make a difference and indeed aid the system overall if applied properly and sensibly. The few minutes longer however and finally receiving straight MAY for 26 prior HOLLY implies that the AMAN data of 15-20 prediction was totally flawed/ incorrect perhaps? In this case a delay occurs through been slowed up when in fact perhaps no delay would ever have occurred anyway... The issue is that of inaccurate AMAN data for KK, leading to loss of confidence and perhaps unnecessary decisions being taken, albeit for exactly the right reason given the data displayed....

I've run some data at work today to demonstrate the positive effect the speed reduction CAN have under the right circumstances. If anyone can educate me how to embed an iPad saved photo into my response text I can share it with you all.....

[tubby linton]

From another thread and posted by PPrune Towers -If you explore USER CP in the yellow bar at the top of the page you'll find you all have an album for uploading shots. Once in they have a url to include in posts.

[30W]

Just exploring speed reduction at the boundary effect:

Image 1 shows actual FMC predictions based on an average decent profile - M0.78/270kt/250kt at SLP/220kt HOLLY. Elapsed time REVTU-HOLLY 19mins

Image 2 shows predictions based on a typically ATC reduced profile with delays - M0.75/220kt all the way to HOLLY. Elapsed time REVTU-HOLLY 23mins.

So, 4 mins, 1 holds worth saved with ATC intervention at the boundary. Definitely shows it's worth it, however, it relies on AMAN data for KK being correct and that's the point being made, at times it most definitely isn't

[Del Prado]

Thanks for that 30W, very interesting. I do agree with what you say although there is a part of me that thinks if AMAN was developed to be a perfect tool that eliminated all holding, pilots would still turn up at the hold moaning there was no delay when they'd had to slow down! ;-)

A further contrarian view from me, large pinch of salt, etc.

If you're slowed at the boundary and get a spin or join a sequence at standard speeds then in many ways the AMAN speed reduction has done its job.
The runway has been utilised efficiently with a consistent and stable stream of inbounds. Efficient runway utilisation means profitable airport operator and lower charges.

Even if there were gaps in the inbounds, more often than not, these gaps will be used to clear a backlog of departures and when you turnaround there will be fewer outbound delays.

Slowing at the boundary would surely only be a 'failure' for the system if it led to a gap on the approach which couldn't be filled by a departure?

The bigger issue to you as a pilot, of course, is whether you're losing your place in the queue and if you lose faith in the system it will encourage the 'hurry up and wait' mentality of trying to get to the hold first but if everyone is slowed and AMAN order is respected that shouldn't happen.

As I say, just a contrarian view based purely on observation but maybe a different way to think about it as Gatwick gets busier.

[zonoma]

Another point to consider is that even if the AMAN data isn't completely correct, some controllers will be aware of the 'average' delay. If at check-in the average delay is 15-20 minutes, issuing a speed restriction is probable and it is very possible for the delays to reduce completely within the 23 minutes it then takes to reach WILLO (sticking with the scenario 30W posted a couple ago). This would produce the situation being discussed.

[EastofKoksy]

Any worthwhile AMAN should be able to inform controllers what the delay is expected to be for a particular flight. It is no good telling pilots what the delay is right now when they won't arrive at the approach fix for another 25-30 minutes. This goes back to the point in my original post on this topic that a failure of comms in ATC is leading to controllers being given rubbish information about delays that in turn can mislead pilots.

[ZOOKER]

This is a very interesting discussion.
Tubby's post No.43 is surprising. I didn't realise EGKK still did SRAs. During the early 1990s, they were withdrawn at EGCC, (I think), due to the NODE(M) display equipment being unsuitable, according to unit management. And also, having the MCT VOR sited next to the runway, gave us other approach options. The unit remains unable to provide them.
Presumably EGKK/TC are still using the 'BARCO' displays? How many of the TC airfields still do them, and what is the minimum number required to retain currency?