Originally Posted by
togsdragracing
An old tecchie writes: is there not some sort of validity check carried out on submitted plans? Be it syntax, format, whatever.
There is, and it is extensive.
It would have been better to have called it the
trigger FPL rather than the
erroneous FPL. It was “bad” in that it caused the crash, but not necessarily incorrectly formatted. I don’t recall the precise details of the event.
The 28-day AIRAC cycle introduces new airspace, reporting points, airfields, etc.. Thus the set of valid FPL routes also changes every 28 days. This means the NAS software has to be modified (“adapted”) to accept and process the new reporting points and routes.
So the FPL probably got through the NMOC IFPS (or whatever the equivalent was back then) as a valid route, and the error was in the updated UK route conversion process adaptation.