Unless I intentionally turned off center tank pumps until inners decrease to 3000kg, I would never have the chance to find out in normal flights. So this is what happens normally: when about 500kg are used from the inners, auto mode turns on the center tank pumps again, so they top up again from the fuel return and center tank pumps come off. Have you noticed anything different? Have you actually seen even half full center tank with 3000kg in the inners in a normal operating fuel system?
And....yes it is really very simple, except: If there is no significance (I really can't find any either) in the 3000kg figure, why mention it in the first place? Would not a simple action -CTR TK PUMP 1+2 (CASE 2 paragraph) in the paperchecklist, regardless of inner tank quantity, be enough to remind the crew?
Suppose after your 30 minutes investigation you have 4.8 tons in either inner (30 minutes aprox. 1200kg burn if they were full when procedure started) and 2 tons in your center. Would you wait another 90 minutes to get to 3 tons in the inners before selecting center tank pumps on and use at least some amount from the center tank? That's what the procedure tells you. Is it really so simple?
Last edited by aristoclis; 7th Jul 2009 at 18:38.