03/12/2012

The limits of a single runway?

20120311_circling.jpgYesterday, 11 March, between 5h30 pm and 6pm, six incoming aircraft had to circle over the Jura, near Morez. Perhaps the signs of a saturation on the single runway?


The first aircraft to make a circle was BA734, from London Heathrow, at 5h30 pm. Three easyJet UK, a Swiss and a Belgian aircraft had to do likewise in the next 30 minutes. Having seen this very rarely before, I looked for a reason, but found none: no emergencies, no gap in movements on the runway, nothing unusual. Between 5 pm and 6 pm there were 40 movements; between 6pm and 7pm 39 movements: nothing exceptional.

On a second look, I noticed that between 5h25 pm and 6h05 pm the runway usage was always a takeoff, then a landing, then a takeoff etc. This alternation is actually quite unusual, and might provide a clue. I suspect that there can perhaps be less interval between successive departures if there are several in sequence, since an aircraft can get onto the runway ready to go before the previous one has taken off. This is just a supposition, though: I might be completely wrong.

This suggests that the capacity of the runway is indeed around 40 movements per hour: perhaps it can be raised slightly with easy exits for incoming aircraft, but probably not enormously. Thus, the daytime capacity, from 6am to 10pm, could be up to 640 (16x40) movements. However, since not many aircraft arrive between 6am and 7am, and there are some hours which are quieter than others, a more reasonable upper bound for daytime movements is less than 640: I have seen up to about 580 on a few VERY busy days of the year. At quiet periods of the year there are often less than 500 movements per day.

Scheduled and charter aircraft average out at just under 100 passengers per flight: in 2011 there were around 13 million passengers on 135,000 flights. There were also about 48,000 taxi and business jets with, on average, less than 4 passengers per flight. Thus, overall, there were just over 70 passengers per flight.

Now do some simple maths. The airport expects soon to grow to 15 million passengers per year, maybe even to 20 million in a few years. This would mean growing to 210,000 flights, then 280,000 flights per year. However, the current maximum of 580 movements per day equates to 211,700 movements per year. Thus, even if 15 million passengers can be handled without an enormous increase in the number of night flights (10 pm to midnight: there were over 8,200 of these last year), a growth from 15 million to 20 million passengers would imply about 70,000 extra flights per year, which is 190 extra flights per day, which is over 4 hours of fully occupied runway time. Barring miracles (and I don't see any), this could only be realised by a combination of using much larger aircraft, reducing drastically the number of taxi and business jets, raising substantially the runway capacity and having lots more night flights.

Bigger aircraft: unlikely, since the recent experience shows that people prefer more flights per day in smaller aircraft. Less taxi and private jets: these are used by people with lots of money and power, who will resist strongly. Runway capacity: hard to see it getting much more than about 45 movements per hour.

That leaves lots more night flights as the most likely scenario.

Sleep well!

19:22 Posted in Potpourri | Permalink | Comments (0) | |  del.icio.us | | Digg! Digg |  Facebook

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