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Question About Last Thursday's Plane Splash

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  • Question About Last Thursday's Plane Splash

    With both engines out, where does the power come from to control the aircraft? Are these "fly by wire," or do they still have control cables? Is it possible to fly the plane without any any power assist?

  • #2
    my guess is that they were still humming but tore up.I was a mile away when that happened.I flew out today and left before the geese woke!

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    • #3
      Can't answer that but I have seen a lot of negative comments on the Airbus being fly by wire but the results of this splash were of a controlled descent.

      Anyone know whose's engines were involved Rolls or GE ?

      .
      .

      Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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      • #4
        There is an APU, usually in the tail, it's just a small turbine that drives a generator. For hydraulic power in a last ditch effort, some airplanes have what is called a RAT, ram air turbine, it comes down from the belly like a windmill and drives a hydraulic motor.
        Just about all airliners flying today are triple redundant for most systems, usually.

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        • #5
          The aircraft is probably fly-by-wire. It would be insane to not have batteries to power the controls.

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          • #6
            still need hydrolic power.

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            • #7
              Originally posted by tony ennis
              The aircraft is probably fly-by-wire. It would be insane to not have batteries to power the controls.
              Powering the controls isn't the issue -- powering the hydraulics is. But Bill's explanation (backup turbine driving a secondary hydraulic motor) sounds right.
              "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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              • #8
                It's fly by wire. It has an Air Power Unit as Bill explained. The APU generates electricity. Batteries aren't enough to power the FBW system. Not all the control systems are hydraulic. In many aircraft the horizontal stabilizer is actuated by an electric jackscrew operated by a high power servo motor. Other controls may be as well. It is possible to eliminate the hydraulic systems with the motors now available. Think CNC aircraft controls. Same thing.

                One factor in the successful ditching of that aircraft is that it has a "Big Red Button" that is the ditching button. When pressed it slams shut all air intakes for the cabin pressure system and prevents the aircraft from sinking.
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                • #9
                  Originally posted by Evan
                  One factor in the successful ditching of that aircraft is that it has a "Big Red Button" that is the ditching button. When pressed it slams shut all air intakes for the cabin pressure system and prevents the aircraft from sinking.
                  I read in today's news the crew of this plane didn't have time to hit that button. Also, a cabin crewperson prevented the opening of a rear cabin door which would have substantially changed the numbers. Quick thinking amongst a horde of quick thinking.

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                  • #10
                    On a plane that size and up, you pretty much need either electrical or hydraulic assist to move the control surfaces. It's not like there's a great "manual" fallback mode. UA232 and JAL123 are the classic examples of what happens when you have total hydraulic failure.

                    The controversy when fly-by-wire came out was that the computer underneath could override the pilot's inputs if it thought they weren't a good idea, and the fear that the computer (I believe there's 3 of them actually) could go haywire and do something stupid. These days the FMS can fly the plane to a level of precision as high and often higher than a person. What it can't do is make complex decisions in an emergency like this.

                    Besides the APU, the windmilling of the turbines can still generate some power as well. However, it will be interesting to see how bad the bird damage was and how much the fans were still turning.

                    Either way it's clear the crew still had decent control authority in order to be able to put the plane down as well as they did. As a private pilot, total power loss on takeoff over an urban area is pretty high up on my nightmare list. Takeoff accidents are bad, bad news.

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                    • #11
                      As long as the engines were rotating, they would be turning the various pumps and generators. I'm not sure whether the RAT would have deployed automatically or if they had any time to extend it. Bottom line is the guy made the best of a bad situation. My hat's off to him.

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                      • #12
                        Out of curiosity, I just looked it up on Airbus' web page, and the A320/A330 are hydraulically operated, and have three separate hydraulic systems.

                        The main hydraulic backbone is the "green" system. Like Bill stated, the RAT provides power to the green system in an emergency failure:

                        From the A320 FCOM:

                        "A pump driven by a ram air turbine (RAT) pressurizes the green system in an emergency."
                        "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                        • #13
                          If you watch the video, it's about a minute from when the plane hits the water to when people make their way out onto the wings, and the ferryboats are there within a few minutes. Amazing. The FAs deserve credit for their part. This was a case that started with everything going wrong followed by everything going right.

                          If they'd been a few miles offshore in LI Sound or if it happened at night with a low ceiling, the successful ditching (first ever for a plane this size?) might not have happened or a lot of people could have been lost to the water.

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                          • #14
                            Originally posted by John Stevenson
                            Anyone know whose's engines were involved Rolls or GE ?
                            'The 320 uses two suppliers for its engines: The CFM International CFM56 and International Aero Engines V2500."

                            The former is GE, the latter is a consortium including Pratt-Whitney and Rolls Royce.
                            "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                            • #15
                              On a plane that size and up, you pretty much need either electrical or hydraulic assist to move the control surfaces. It's not like there's a great "manual" fallback mode. UA232 and JAL123 are the classic examples of what happens when you have total hydraulic failure.
                              They can be manually flown without assist. They have a basic cable operated control system. It's one of the reasons they have two pilots as they can work together against the control forces.

                              Just a couple of months ago my wife was on an Airbus 320 on a flight out of Calgary, Alberta. About 1/2 hour into the flight over the Rockies the cabin lights and entertainment systems went off. A short while later the Captain came on to say that he had a total computer failure so was flying the plane manually and would be returning to Calgary. My wife was seated next to a helicopter pilot and he opined that they were flying entirely manually without fly by wire assist. They landed without flaps at much higher than normal speed but made it just fine.
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