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Comment by focusedone | Hacker News Reader

There's a lot I don't understand with this, but why pull back airplanes which had already left the gate?

There are large checklists that need to be completed prior to take-off, not sure how much of this is automated now but if that is no longer possible you're just not going to take off.

Checklists are surely not pulled from an external system while the plane moves. That would be a recipe for disaster!

I've written fuel estimation software for 747 cargo planes for one particular airline. Pilot would relay all of the info about plane identity, route, load and destination, fuel estimate would be computed externally and then be sent back through text message or voice call, pilot would then do his own check. This is really not something you want to get wrong, having multiple go-arounds or a late abort to an alternate for whatever reason should never result in a low fuel condition.

Obviously planes already leaving the gates are fueled up so that's most likely not the case here but that's one example of how those systems can be still integrated. Now, today - with far more computing power - it is very well possible that that whole system runs on the plane side, but the amount of external data and various exceptions and almanac information that was pulled in for those computations was pretty impressive. Most likely that sort of thing is now done on an iPad or something similar.

You're right -- that's what I was trying to say. There are all sorts of external systems tied into flight planning and operations, but once the plane has left the gate the plane should contain everything important already.

Thus, the only reason to recall a plane that's pushed back already would be to avoid problems that would occur only after it has landed. I would be surprised if the external systems were needed for the flight itself.

These aren't a concern to the business processes.

The 777 has automated presentation of some relevant electronic checklists but these definitely are NOT automated because the whole point is human-attended verification.

> The system manages flight information like crew scheduling, weight-and-balance calculations, and aircraft movement logs

You wouldn't want to fly an airplane whose weight and balance has been miscalculated (or maybe properly calculated but can't vet if it has)

https://en.wikipedia.org/wiki/Cubana_de_Aviación_Flight_0972

https://en.wikipedia.org/wiki/Air_Midwest_Flight_5481

By the time they have pushed out the weights are already accounted for. It's part of the checklists that come before taxiing.

Even if the weight balance and loading are OK, it might be because other flights at the destination are being delayed at their gates and there won't be any gate for the aircraft when it arrives.

As long as the planes don't leave, the airline will know exactly where staff and equipment are: right where they were when the system broke. Once things get moving it becomes really complicated to figure out where everything is again.

During previous similar outages it has taken days to track down staff and equipment once the systems are up again. During this time delays and cancellations continue. It's possible the system is much faster to bootstrap given correct locations of things from the start.

There are several regulatory, financial, and other business processes that must occur for commercial jets to fly. They can't just put fuel, pax, luggage, and crew on-board and send them on their way without recording data in various systems.

I'm guessing the system handled sensitive/critical flight information:

>The system manages flight information like crew scheduling, weight-and-balance calculations, and aircraft movement logs.

The relevant critical information would probably be copied to pilots already. I suspect it has more to do with what happens after landing.

You seem to know more about this than me, so what about the "aircraft movement logs" part? I would think it'd be hard to copy that to the pilots ahead of time, given you haven't logged it yet. (Or am I misunderstanding the type of "movement logs" here?)

But your other comment seems more likely: keep the people/equipment where they are to reduce the recovery time down the road.

I would guess that refers to entering records when the plane takes off and lands, to keep track of where it is. I.e. not information that would be used in flight -- at least not critical information!

Obviously air traffic control wants to know the exact location of the plane but they have radar and the airplane has a transponder for that purpose. I don't know if the airline cares so much, other than the estimated arrival time to account for delays.

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