Originally Posted by
itsnotthatbloodyhard
The flight plan GS is the average for a leg which might be over an hour long. Plenty of times I’ve seen the GS change by 40 or 50 kts in a couple of minutes, due to wind changes - which means GS is ok as a rough confirmation, but remains a fairly blunt instrument. Which is probably why the A330 procedure is AoA-based, and doesn’t refer to GS at all.
That is true on very long oceanic flights but we are talking generally here, and in any event, AF 447 went from safe light to chaos in a matter of a couple of minutes where is they had maintained steady state and GS that would not have happened.
And in the majority of cases you do know your wind speed very accurately. A lot of UAS incidents occur at low level and wind is known exactly. And it is at low level, AF 447 apart, that the problems usually need quick resolution. And GS does it for you every time.
Y