Aircraft Hydraulic systems design flaw?

I have been watching again one of my favorite television series, aircrash investigation and been thinking that big airliners have clear design flaw.

What is a common with Japan Airlines 123, (http://youtu.be/dK_UdBU_Mvc),   United Airlines 232(sioux city crash) and one UPS plane that was show down with anti aircraft missile, but survived the crash landing.

All of these planes lost all the hydraulic systems. Usually these planes have three separate hydraulic systems, so they should be very reliable. The problem is that the same system goes through the whole plane. So if you get hit by missile to the wing tip, you loose all the three systems and it also takes out the tail control. So plane has only engine power to steer and to control altitude.

The flight 232 had engine explosion that destroyed all the three hydraulic systems. When I first heard about this, I started to think why they had all of those lines side by side? Maybe it would be a good idea to route one system in totally different path?

Later I watched the UPS flight from Irak, it got hit by anti aircraft handheld missile strike. Both engines survived, but wing tip was hit severely. They bleed out all the hydraulic fluids from all three systems, but were able to land the plane by using engine power to steer and control the plane and luckily all three crew members survived. This crash was 12 years after Sioux city crash. Nothing was done. They had developed Engine control software that could land this kind of plane that had lost hydraulic systems, but FAA concluded that it’s too rare event. So the system is not needed.

And in some point I understand FAA,  as if the UPS plane would have been hit to the engine, it would have not survived(if hydraulics and one engine would have been lost). What I don’t understand why the lost of wing tip looses the tail control? Even cars have brake systems, that if you loose one front brake, you are not going to bleed out the whole system, it’s just going to loose one front and one rear wheel, and other pair is going to stay working. Motorcycles have separate front and rear brakes. Polaris ATV’s have brakes that brake all the wheels from the handle, but you can still use separate rear brake that has separate reservoir for the rear brake.

My point is, that If you loose the wing tip, you cannot loose all the systems as all the systems should not go to the wing. One system should be reserved as tail backup only. And one for the wing backup, if the tail is lost.

Or just install valves to the wing mounting area, that can be shut down when the wing starts to bleed fluid. After all wing damage can occur easily in engine problem or in missile attach. As the missile seeks heat and engines are today mostly positioned to the wings.

Japan Airlines had collapse in the rear fuselage and part of the tail was lost and it took out all the control hydraulics. Again it should have lost only the tail, not the wing controls.

It’s too bad that so many lives were lost in these incidents. And the cause is design. A Triple proof system that cannot fail. But it still fails as they don’t take into account that there could be major damage to the plane and you cannot loose all the controls at the same time.

I have heard that some of the future planes don’t anymore use this kind of hydraulic, they could use electro hydraulic systems, that each flap and control surface has system that contains the pump, fluid and hydraulic piston and it’s controlled by electricity.  In this kind of system the lost of all the controls is almost impossible. It would take total electric blackout, and electrics are usually easier to backup compared to hydraulic systems.

So next time flying, watch the wing and think it holds three different blood systems and the planes is going to bleed to death if those lines are damaged. Three times backup, but side by side and all the fluid is lost in relatively small damage.

-JP-

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