Originally Posted by
DaveReidUK
OK, I think I see what you mean, although I'm still struggling to understand what a "gross error check" would prove, other than the existence of the FR24 QNH issue that I previously referred to.
Yes, that's more easily ascertained from the FR24 data as it's not QNH-dependent. At the quoted lift off time of 23:10:29 (per the report) the ADS-B data shows the 777 roughly abeam twy N4.
Gross error check as in if the two times aren't similar, then I would say the FR24 liftoff time is almost certainly wrong.
But from reading more posts, from people such as yourself, who obviously know much more than me about FR24 data. It seems that the FR24 data is always wrong in high QNH conditions.
Therefor as you say the gross error check is redundant, if we already know its not reliable