747-400 Hydraulics Failure

[Guest scousemik]

I've just tried flying with all the hydraulics turned off. I was trying to land using only the throttles (like the DHL Airbus did after being hit by a SAM in Iraq). However, I can still control the aeroplane using the stick by "pumping" it. Why is this so? I also notice that the brakes remain functioning, even though I have a "brake source" caution.Still a superb product though! :)Mike.

[Qavion 19]

"I also notice that the brakes remain functioning, even though I have a "brake source" caution."There is an emergency reservoir/accumulator (for holding pressure accumulated when the pumps have been running). You will get a number of uses out of it, but it's best to push the brake pedals and keep pushing during an emergency landing. The reservoir is also used for the Park Brake which can be used even when there is no power on the aircraft.If your Engine-driven pump switches are still set and/or fire handles not pulled, the windmilling engines will keep up a decent pressure (if your airspeed is not too low).Not sure what you mean by pumping the stick. If you push the stick forward (in the air), you will go faster. The engines will windmill faster and the engine-driven pumps will build up pressure.The Brake Source light only looks at active pressure sources. The Accumulator is not considered to be active source (hence the light).Hope this helps.Cheers.Q>

[Guest scousemik]

Hello,Thanks for the advice. I forgot to mention that I had already tried depleting the accumulator....maybe its bigger than I thought!When I say "pumping" the stick, I mean that I apply pulses. If i want to roll, I apply a chunk of roll stick for a split second, then release and repeat. The engine driven pumps are off. I have also confirmed that there is no pressure in any of the systems. The lateral axis does go a bit relaxed....like poor damping.Cheers,Mike.

[Qavion 19]

Sorry, no idea about the mysterious hydraulic power source... )The accumulator is only for brake pressure, not for flight controls, so you will only deplete that by applying brakes.Cheers.Q>