He flew on SQ
Don't worry, I was assuming he was flying in the other direction, and that does have performance implications.
More seriously, how does FRA-SIN compare to CPH-SIN, I'd take it the former is shorter.
I've looked at your numbers, and although they generally seem ok on inspection, the fuel numbers are perhaps a bit too optimistic - even remembering that CPH-SIN is slightly shorter than SIN-CPH because of winds (airmiles vs statute miles).
I flew LH SIN-FRA, and the numbers were as follows - I've got the flight plan, and had a jumpseat ride.
CRZ: FL310 (till 60ton FOB), FL350 (till 30ton FOB), FL390. M0.82-0.83 crz spd.
CI (Cost Index) 160
BRW: 268,800kg/592,596lb - 2,200kg below MTOW.
So, here we were with an A340-313X (271ton MTOW) with a full pax load, and we were very close to MTOW, and yes, we used up a lot of runway. Almost 30°C and Vspeeds in the region of 160kias.
If we turn it around and turn it into a CPH-SIN, we can subtract about 10ton (perhaps even less) from the FOB at TO, so we'd have a BRW of 258,000 - some 20ton heavier than your calculations. However, Preben as you say, there really shouldn't be any TO/CLB problems (CPH at that time of the year is not too tough), and I'd say that FLX (derate) thrust was used now, having reviewed the situation.
Charles, one more point. The 1500fpm, I refer to is achieved once initial climb speed (V2+10) is achieved - very shortly after rotation, you may be not even be at 1000fpm yet. Now that I've reviewed your scenario, the climb performance may be a little better.
Just remember one thing - if you lost an engine Charles, you'd rather be on an A340 than a B777
It's not entirely true that a twinjet with one engine out has the same power as a quad jet with one engine out. Why? Twinjets don't need to make the same climb gradients as Quadjets.