Received this from Pat Duncan this morning.Ben
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The story for this picture is: "Saudi Mechanics were taxiing the Saudi B-747-300 when apparently they started only the outboard engines (1 and 4). They soon found out that the hydraulic pumps for the brakes are on inboard engines (2 and 3)."
Been a long time since I went to 747 systems school... but I think the jazz about the #1 and #4 engine hyd. pump scenario is BS. As I recall there are one or two electric hyd. boost pump systems that have to be activated to charge the brake accumulators before taxi or towing. However if the brake accumulators were not charged and the brake system pumps are on #2 and #3 then this could have been the cause. Whatever the reason this thing lunched itself..... there are huge $$$$ involved in this repair.
Note the separation of the rear main cockpit bulkhead... plus the complete destruction of the forward lower 1st class cabin. Hope no one was in there at the time. God only knows what damage occurred to the MLG systems as well as #3 & #4 engines, pylons and lower wing spars when the nose dipped down into the culvert opening and the nacelles hit terra firma.