Backseater's question on flow on the 33's.

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rookiepilot
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Backseater's question on flow on the 33's.

#1 Post by rookiepilot » Sun Apr 02, 2017 3:10 pm

So on a US bound flight (3 weeks back -- day after that big storm) with a nasty NW wind, departing 33R. Light SN and takeoff vis maybe a mile, clear after TO. Way after rush hour.

Departure rate really slow, so huge backlog developed. When we turned must have been a dozen plus behind us in the line, never seen that, more backed up on other taxiways. Took position and held, a long time after preceding departure. Just curious why, never seen that before although first time I remember departing on 33 R. That affect things?
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cossack
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Re: Backseater's question on flow on the 33's.

#2 Post by cossack » Sun Apr 02, 2017 3:35 pm

The 33s in the snow is a nasty configuration. Take a look at an airport diagram.
Very inefficient when de-icing as all departures going to de-ice will cross 33R at either S or R. Some arrivals will go down F after landing on 33L but the majority will cross 33R at N and H. As you can maybe imagine, the departure rate takes a huge hit. We'll depart a bunch and then stop while we cross a bunch. If you were first waiting for this bunch of crossings, you may have been waiting 5 minutes, but the arrivals and departures waiting to go de-ice will have been waiting too. We're just spreading out the pain equally.
Basically its shitty. If the arrival flow rate is too optimistic, we can be very close to gridlock.
When its like this, its always rush hour. Arrival capacity is reduced from 60/hr to 32 and sometimes that is too much. In heavy snow, 20 would be a manageable arrival rate with a departure rate to match.
HTH
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