Quote from
dixi188:
"The 1-11 518 srs. for Court Line had a fixed droop to the leading edge which was developed to allow max weight ops from Luton. Most others after this had the same. Not sure if earlier A/C were modified though."
Yes, from my experience - limited to BCAL - we eventually obtained two Dash-528FL a/c from Hapag Lloyd to supplement our 500 fleet in 1981/2. They had the new leading-edges you describe, and a choice of three flap-settings for T/O instead of the usual two (8 deg and 18 deg). I think the lowest setting may have been 6 degrees, which would presumably improve the WAT situation (for the second segment climb), provided the runway was long enough to take advantage of it. I don't remember any penalty for cruise performance with the new leading edge.
(Re WAT limitations, the technique in common use today of trading any excess runway to achieve a higher VR and V2, and therefore an improved second-segment climb angle, was never adopted on 1-11 operations -
AFAIK. Don't know why we did not try to introduce it in BCAL, because we had already been using it to improve the payload capability of our B707-320Cs out of hot-high-long Nairobi since 1975/6.)
Quote from
oldchina:
"It's just that slats add lift but also the drag that comes along with it. The latter was unacceptable with so little thrust on board."
Am no aerodynamicist, and I hesitate to stumble into a debate on what no doubt involves complex compromises for aircraft designers. I appreciate that thrust has to exceed drag on take-off, and it was in rather short supply! But my simplistic understanding is that slats enable an a/c to fly at a lower speed by enabling a higher AoA while maintaining a safe margin from the stall. We are not asking for more lift; merely the same lift at a lower IAS (okay, EAS).
I guess that the higher AoA may involve a slightly inferior L/D ratio (= more drag). The alternative is to use some or more flap, which probably causes an even bigger deterioration in the L/D ratio?
The best WAT performance for take-off on an A310 involves a flapless T/O with slats at the T/O setting. Taking your argument to its logical conclusion, one might expect it to use T/O flap with the slats retracted?