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Moscow Passenger Plane Catches Fire, Crash-Lands in Cornfield.

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  • #46
    Originally posted by ATLcrew View Post
    Ours doesn't indicate that, it indicates gear EXTENSION gravity only "to preserve system integrity", retraction is not mentioned at all. I don't know if it's necessarily because of the PTU or just because to minimize load on the system in general.
    There are priority valves that shut off the heavy users (flaps, slats, gear) when the pressure is low, to preserve flight control. But that doesn't explain the B + Y thing. This was listed in the QRH I have for GA after the B + Y failure. OBVs not the same version you have.

    As for load, the best I could find was this badly designed chart in an engineering article presenting a case for Variable Displacement Hydraulic Motors. The text indicates that this chart is based on an existing 'typical load profile for a civil transport aircraft'. The light yellow is 'available flow' based on the engine power setting. The dark blue are the 'required flow' levels for the items listed to the right. You can see that the gear retraction requirement exceeds the available flow at approach power settings, so I would expect this to also be true after a bird strike-induced power reduction.

    Click image for larger version

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    Glossary for 3WE:

    B- Blue
    Y- Yellow
    GA - Go Around
    OBVs - Obviously
    3WE - Undefined

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    • #47
      You guys are funny!

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      • #48
        Originally posted by Evan View Post
        There are priority valves that shut off the heavy users (flaps, slats, gear) when the pressure is low, to preserve flight control. But that doesn't explain the B + Y thing. This was listed in the QRH I have for GA after the B + Y failure. OBVs not the same version you have.
        There were some serial numbers that had landing gear on the yellow system, I believe the Smurfs have a few, that might explain why your QRH says what it does. It bears mentioning that a B +Y failure would take some doing outside of fluid loss (and then to lose fluid in both of them would be quite a task). Even to just lose Y outside of the above-mentioned overheat from the G side scenario would be no easy task without a leak. It would take three separate failures for that to happen (EDP2, Y ELEC pump and the PTU). At least G and Y are connected somewhat at the PTU, B and Y are not connected anywhere.

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        • #49
          Originally posted by ATLcrew View Post
          There were some serial numbers that had landing gear on the yellow system, I believe the Smurfs have a few, that might explain why your QRH says what it does.
          Qatar, rev 40. But it also indicates 'no gear retraction' for G + B, so I don't think it is matter of which system powers the gear.

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