Ask The Pilot

[jb747]

We hear a lot about advanced flight planning and routing. Can you please explain how these two very separate tracks, that I imagine were planned by airline experts, can result in almost the same departure and arrival times?

I doubt that there was any human input in the planning at all. It's basically a case of starting at the destination, and working backwards through the various possible routes and flight levels, overlaid on the projected wind/temperature. Slow when done manually, but computer systems can run through huge numbers of variations in no time.

For these two routes to take more or less the same time (ignoring the fact that the different aircraft probably fly at different speeds/altitudes), it would require that the number of "air" miles, not actual distance, is roughly the same. An air mile is what you end up with after correcting for wind. So, you could fly a greater actual distance, if you have more of a tail wind component...adjusting your air miles. Basically, there's more than one way to skin the proverbial cat (why pick on cats?).

As for hearing about "advanced flight planning and routing"...that's more in the line of the standard QF enhancements, i.e. it's simply a way of legally giving the pilots less fuel, not a way of actually burning less. Flight plans are in many ways like war plans; they never survive contact with the enemy. They make no allowance for other aircraft beating you to an altitude you're planned for, weather deviations, ATC requirements, etc. They simply look at the averages of the past. I really don't care if the last 9 guys arriving at Dubai had only 15 minutes of holding, if I happen to get there on the day that you need an hour.

 

[jpp42]

I doubt that there was any human input in the planning at all. It's basically a case of starting at the destination, and working backwards through the various possible routes and flight levels, overlaid on the projected wind/temperature. Slow when done manually, but computer systems can run through huge numbers of variations in no time.

One thing I did note is that the QF flight was an A380, not subject to ETOPS restriction, and the UA flight was a 787-9 which might be certified to ETOPS 330 (though it might be less). Does this actually affect transpacific planning or not? I would think that all reasonable flight paths would be within the ETOPS 330 circles anyway, but wondering if that could be part of the picture here?