The Leap NEOs definitely have more thrust margin available at cruise than the CFM56 CEOs. In my company there seems to be an informal SOP not to cruise at anything higher than Rec Max -1000ft. This is to prevent getting below GD where the CEOs might not have the puff to power out of the increased induced drag. This behaviour has lead to pilots not being accustomed to flying at altitudes where the aerodynamic margins are slightly narrowed. (Realistically, we are always flying waaaaay above stall speed and a lot closer to MMO).
Unfortunately this informal SOP has carried over to the LEAP equipped aircraft which certainly do have the power to cope with deviations below GD. I have seen a 321 NEO at OPT/Rec Max 380 accelerate from Vls -6 (approx GD-9) without any difficulty after encountering a gradual shear. The thrust was slow to come on but when it did it accelerated reasonably smartly (N1 had been sitting at 87.5ish).
Flying the NEO at Opt/Rec Max gives aerodynamic margins similar to other types I have flown whilst retaining superior thrust margins. When Opt/Rec Max coincide and at low cost indices, managed speed is within a knot of GD. This spooks people but having flown the NEO for hundreds of hours in this exact configuration I can reliably say that this is unwarranted - it is a perfectly safe and stable configuration. I am also flabbergasted that people feel more
comfortable in these situations to select Mach and put it half way between GD and MMO. It makes the picture look a little more “normal” but significantly degrades your margin to MMO while increasing your margin from V alpha prot which you are already well away from. It betrays a real lack of understanding of the aircraft’s actual performance.
To my way of thinking, flying the NEO as a CEO is very conservative and a little wasteful not to mention the additional airspace congestion caused by aircraft flying 2000ft below their ATC filed levels.
Last edited by speedrestriction; 24th October 2021 at 16:25.