Aircraft X has a stall speed of 50Kt and an approach speed of 65Kt with landing flap. With a level grass runway, including the safety factors, the landing distance required is 600m
Flight Manual recomended technique is a steady approach at 3deg glideslope to cross the threshold at 50ft and 65Kt. At this point the throttle is closed.
Now let's say that the wind is 10G20.
Approach speed 70Kt (Vth + gust/2)
Ground speed at the threshold is;
60Kt with no gust and 50Kt with the full gust.
Now if the aircraft can land in 600m when the groundspeed at the threshold of 65Kt can someone please tell me why it will run off the end when the groundspeed is less.
The only reason why adding half the mean wind is not recomended is the problem with trying to get rid of all that airspeed.
As a pilot you are expected to cross the threshold at a speed of Vth +15/-0Kt. If you can't do that the CAA will not give you a licence.
15 knots fast in 0 wind will eat into your 1.43 safety factor. However, using the half gust factor maximum 10Kt, you would never be that fast if you fly accurately.
The big jet on the big runway can be even more limited in terms of performance. In other words, it needs every metre of that big runway.
Regards,
DFC