Originally Posted by
172_driver
I believe I speak for the majority when I say flap 30 is the norm on the 737, flap 40 only for performance. My friends on the 320 seem to prefer flap full over flap 3 (..is that how you say it? or config 3?) as standard. I have always wondered why it's become like that....
Different landscape, really. Immediate return OEI:
(*)
- ISA SL -> up to 88 tonnes the standard flap is full.
- 4000 ft @ 40° -> 77 max for standard flap full (77 = MTOW).
F3 is awkward. But you have a point, perhaps one day everyone will switch over, most likely for noise. As witnessed by the valuable insight here, there is no practical benefit
(**) although for a narrowly minded KPIs a case can be made and had been repeatedly.
IIRC on IAE engines the angle for flaps full was increased to a greater deflection, to allow higher N1 in order to assure TOGA engine spool-up characteristics. Heard it here, FCOM confirms the geometry.
(*) Airbus cheating again, QRH: MAX WEIGHT FOR LANDING IN CONF FULL again has data for CS-25 gradient 2,1% (non LVO), whereas in the real-life 2,5% is needed to match PANS-OPS.
(**) if approaching stable approach gate 1000 and too fast, a dirty trick is to change for F3 and move the goalposts. Let's talk what's wrong with some FDM / FOQA concepts ..., rather not.