Personal preference: If the aeroplane is well below 44 tonnes, then i find F40 better for speed stability and you fly the app with a more sensible N1.
I'd rather have the response/spool up from 55ish% at F40 than flying along at 45ish% N1 with F30 at a Vref of 115-120 (esp. in light -500) and the whole thing handling like a rice-pudding....
Flap travel between 40 and 30 is pretty fast anyhow...
Performance-wise (for a G/A) i'd be suprised if there was any significant difference (If there is I'd expect it to be promulgated somewhere..)
As far as gusty conditions go.....well....if you're really light you've got 40ish+kts margin before flap-load relief is required to do its thing...
Notso: point taken about what might be in the Boeing manual...will raise the issue with our TSC....get them to clarify if any doubt.
Last edited by Bumblebee; 1st December 2004 at 09:30.