CTOT versus Off Blocks

[issi noho]

This evening i watched a BA Shuttle have to taxi back onto stand to refuel after its CTOT was altered several times after push back. I'm not exactly sure but I'd guess a minimum of half a ton of fuel wasted, probably more or i doubt he would have needed more. This is fairly unusual but more likely is the case that we are refused push because of delays at the hold which mean we would not get away within the slot. These delays we have no control over nor are able to see when we're facing the pier.

Would it not be better if, instead of CTOT's we were given Off Blocks Time's.

It would be much easier and straight forward for the crew to manage. Easier for ATC to enforce (no ambiguity), wouldn't be affected by problems with holding point delays at peak periods.

There are bound to be problems with infrastructure since CFMU has grown into a huge business since the 'good' old days where we used to phone the regulator and speak to a Controller with half a dozen clip boards in front of them but is it possible and does anybody agree it would be better.

[merlinxx]

IssiA valid question, but and a big but is the intigration of all CFMU CTOT functions with that of the individual airfields Ground/Air ATC units. Add to this the ground handling staffing (lack of/communications with etc), you have a bloody great big conundrum. I know this is a subject close to IATA's, AEA's and all other industry organisations (including the BIZAV sector) associations and Eurocontrol.

Answers before 2027 before I depart for the last time plse/

[Gonzo]

Easier for ATC to enforce, yes, but far less accurate of course.

At the moment there are loads of variables for regulated flights: Airborne within a 15 minute window, and then a flight of up to two or three hours during which winds, route, airspeed might all change.

Add to that list taxi time (at Heathrow this might be as little as 5 minutes, to as much as an hour), and the effectiveness of putting a regulation on is almost zero.

[issi noho]

What has accuracy got to do with it, it isn't really encompassed with the present system when you consider the -5 +10 dimension. There would still be the same number of aircraft and they would fit into the flow in a random manner.

If i can tell you about my flight yesterday. I had a slot delay of 55 mins, for destination airport restrictions. I was a/b on the CTOT, my sid should have been about 75 miles of meandering thru the TMA but i didn't actually fly more than 3 miles of it as i was cleared direct to FIR bdy (about mid point of the journey). I took a substantially lower level than planned to make use of 130 kt tail wind. total time savings were about 27mins, and this is out of 55 mins where technically my destination didn't want me there.

From FIR Bdy i was cleared direct to centre fix , speed restrictions removed during decent and i was only taken off that route to be vectored number one to a 5 mile final, if i hadn't of bounced it, it would have been a great day.

The CTOT system came about from the original regulation system, like i said earlier but that system began because of some pretty awful European situations, with closed airspace, strikes, poor equipment etc. I don't think that exists today. I think it doesn't matter where you apply the restriction the fact remains that the number of aircraft in the system will be a constant and whether it takes 5 mins or an hour to get away just adds to the randomness of the distribution for the area controllers to deal with. In my experience, and i do have some, controllers work harder and enjoy the peak rushes far more than a constant, never ending stream across their tube. The problems only occur when the constant stream is a peak flow. This we shouldn't allow and hence the need for regulation.

In addition to that we've lost the benefit of the 'NO DELAY' option.

Lets say I'm at a busy airport in peak. My company request a CTOTwhich is EOBT +25 (knowing there is no way i'm going to get a/b in less than 20 mins)
I call for push on schedule and ground fit me in to the system. Now heaven forbid i do that in off peak time because the controller would look at the traffic and say i was too early (ie; a delay) or to put in a ready message. All of this takes time and my opportunity for schedule is gone. Now it may only be a couple of minutes but those are the minutes by which the CAA and the various transport users associations measure our performance.

The long and short of it is that if you were allocated a CTOT as you requested and a ready message again gets you what you want then it should have been NO DELAY all along. I could even accept No Delay until xxxx time.

[Gonzo]

What has accuracy got to do with it

Accuracy has everything to do with it.

The CFMU looks at the flight plans (demand), and the ATC capacity, and if the demand is too high over a certain period, then CTOTs will be issued.....all this I'm sure you know.

The CTOTs are issued as CFMU can assume that an a/c will be airborne between CTOT-5 to CTOT+10 (i.e. an airborne window of 15 minutes), and can then forecast what time that flight will hit the regulated sector.

If COBTs were used instead, CFMU would have to work on an airborne time of COBT+5 to COBT+60 (i.e. an airborne window of 55 minutes), certainly where I work. How would that be better?

I readily admit that the current CFMU system is a very, very blunt tool. I fail to see how going to OBTs would improve the situation.