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Hydraulic Failures on FBW Aircraft

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Hiya, I have been looking for a schematic but can't find one so I will go from the top of my head...What happens if their is a complete engine failure on a FBW aircraft such as the 777 or A3x0? You loose the engine driven hydraulic pumps and the main buses therefore the electrical driven pumps also. What happens if the RAT fails to extend? You are left without any hydraulics and their is no manual reversion. What do you do??? Aysemtric (SP?) thrust is out of the question (no engines!) so how do you stear the thing? Also do you loose the EFIS displays?Cheers

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Rici,If this actually happened, the best thing you could do is pray :-)This is reason there are so many back up systems. Without any hydraulic power there is no manual reversion any more so they put multiple hydraulic systems wth multiple sources of supply and back up systems such as the RAT in place to keep you going. Look at the fine job the Airtransat A330 did Deadsticking in that bird over Canada. The back up systems are thoroughly checked and very well designed to avoid failure. As far as Nav Displays. Boeing and Airbus do it a little differently. Both have a hydraulic motor generator that runs off the RAT but what displays you get varies by A/C. Needless to say you wont have much, Minimal draw is best when flying a glider.RegardsPaul:-cool

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I could be wrong, but this is what I understand with Airbus A320s.If an aircraft loses it's power, the pilots are left with 2 axis of thier three axises to control the aircrat, and are, rudder, and elevators. Since their joysticks are only the switches, it will not allow the airelos to be operated without having any electronical signals... However, I am not sure how the rudder, and elevators are linked to their sidesticks...A good example of what might happen to a GLASSCOCKPIT aircraft with a complete loss of the power would be an Air Canada flight which landed on Gimley(SP?) back in 1983. It was a B767-200, and experienced a complete black out in the flight deck. Well, basically, they had completely run out of fuel in flight up in 41000ft.

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All the FBW airliners have an emergency backup called a Ram Air Turbine. The RAT frops out of the belly of the plane and has a small prop on it.... as long as the plane is moving it will generate electicity and hydraulic power for the flight controls.Brian

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Thanks. The 767 is not FBW and has manual reversion so it does not really coun't in this situation. FYI the two axis on the airbus are controlled by mechanical linkages but the A340 500/600 has them FBW too now. I did a huge project on FBW for my A Levels so I have a whole shed load of info although its at the exam board now so I don't have access to it. What I am asking is what would happen IF:All engines failed on a 777. You loose the EDP's, ElecDP's and ADP's as ''normal''So now you rely on the RAT to give you hyd press. What if that fails?The hydralic backups are their to prevent the failure of an electrical bus or whatever from stopping the hyd press. If the engines go you loose ALL pumps and backups exept the RAT. So what do you do if the RAT starts playing games??? Cheers

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Rici,Simple answer is Your Screwed! :-zhelpThe RAT is the last line of defense so if you are down to the RAT and it fails your toast. This is true on the 757/767/777 and all Airbus products since the A300 (and maybe even the A300 but I never worked the A/C so I don't have system specifics. Even A/C that are not technically FBW rely on hydraulic power to move the Flight Control Surface Actuators whether a electric servo tells it to move or a cable run tells it to move. Either way, No hydraulics = No Flight Controls.Hope this helpsRegardsPaul:-cool

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