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Plane Answers: Why can't airlines wait at the gate vs. in a queue on the taxiway?
There are times when I find myself on a plane that is waiting in the queue to depart and I wonder if this makes sense. After all, having 10 airplanes push from gates only to idle their engines for 20-30 minutes waiting to take off does not seem to be a good idea for an industry where fuel is the largest single cost.
Can you explain who decides when an aircraft pushes back and queues up to take off? Is there a reason that airplanes get in line to depart as opposed to just being assigned a number and waiting at the gate until it's their turn (other than if the gate is needed for an arriving plane)?
It doesn't really make sense, Mike. But some airports have adopted a gate hold program that does just what you're talking about; hold airplanes at the gate until the line begins to clear out. London and Paris both use this technique. However, even after holding at the gate for 15 minutes to an hour, we still often find ourselves waiting in line for departure as we approach the runway. It's simply a matter of the required spacing for departures combined with the number of flights scheduled to leave at the peak times that causes this.
There is also a concern by ATC that there may be no aircraft ready at the end of the runway for departure if they're held at the gate at the last minute, which would result in even more inefficiency.
Other airports (especially in the U.S.) will advise flights of a 'wheels up' time, allowing the pilots to push back at their discretion as long as they can be ready by the time given by ATC. This works to some extent, but flight crews are paid only after they push back from the gate, so the incentive to begin taxiing early is something that admittedly factors into their decision.
To prevent this, our company has a system in place to start the pay clock for pilots and flight attendants once an ATC delay is given which, in theory, would eliminate this incentive. In practice, many pilots don't trust the system to log the time or have been denied the extra pay in the past and would rather take the delay off the gate - possibly to an area where ATC will allow them to shut down the engines.
Richard Branson at Virgin made an attempt to think outside the box and looked into a tug system that could tow the airplanes to the end of the runway. Such a system could have saved hundreds of pounds of fuel per flight. Unfortunately, it was discovered that the extra wear and tear on the nose wheel would cost more than the savings generated by the reduced fuel burn.
Do you have a question about something related to the pointy end of an airplane? Ask Kent and maybe he'll use it for next Monday's Plane Answers. Check out his other blog, Cockpit Chronicles and travel along with him at work.
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