Physics behind the failure.
When the fan disk in engine number 2 split, the titanium shrapnel impaired the fuselage. This resulted in the only three hydraulic systems in the DC-10 to be drained empty. All of the DC-10's controls were operated by those three hydraulic systems. Hydraulic systems are used on aircraft to move landing gear, flaps and brakes. Larger aircraft use these systems also on flight controls, spoilers, thrust reversers, etc... The reason to use hydraulics is because they are able to transmit a very high pressure or force with a small volume of fluid (hydraulic oil).