Originally Posted by
AirScotia
I'm increasingly baffled by the 'duplicate waypoint name' issue. This suggests - it's surely impossible - that waypoints are known to NATS as strings of characters. Surely each waypoint has a globally unique identifier or key? The flightplan has to mean something to the personnel, so they can select 'INGOR, ANNET, NAKID...' or whatever, but behind the scenes each of those should be a unique id. What am I missing?
I also have no idea why the system was allowed to get into a state where it decided it was utterly untrustworthy and collapsed. Planes have multiple software paths so that a rogue path can be outvoted by the other two. Why didn't the NATS system look at its own performance against all the other flights it was handling, and make at least an interim choice to keep going while it flagged up the anomaly?
Whilst the system may have more knowledge about a waypoint all that comes in the plan is those 5 letters. You need to know the context of surrounding points to know which one of the possible duplicates it is. To do that you need to parse the string of waypoints and it seems to have failed whilst parsing. From the report it appears that it isn't just a case of duplication. The duplicate needed to be in a particular place with regard to the exit point from the UK and also that the actual exit point wasn't in the plan. When it parsed the plan it knew enough about waypoints to know the result it got wasn't geographically correct but not enough to know why.
What it did then was fortunately safe but I, and I suspect most FDP staff, would not expect an issue with a single plan to result in an exception that brought the whole system down. We don't know whether that was a design decision, an oversight in design for an error not foreseen, or a coding error that meant it didn't do what the designer intended. We are going to have to wait a while to get the answer to that. If it was intended then I would hope they expected to resolve that issue much quicker than they did. Again we are going to have to wait a while for answers in that area.