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Does anybody know what that loud growling-scraping-groaning plane noise is?

Discussion in 'Non-Vegas Chat' started by dmr, Oct 15, 2014.

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  1. dmr

    dmr Registered Abuser

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    I've noticed this off and on with US Air and more recently with Spirit.

    Right before they pull back to take off, there is this loud sound, kind of a "GRRRRrrrrrroooowwwwwwww-wow-wow" type of sound that occurs. It almost sounds like something is straining to do something and is not getting it done.

    Anyone else notice this? Anybody know what it is?

    TIA. :)
     
  2. Ty

    Ty ?

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    Not long ago on a Delta flight leaving Vegas the FA gave an announcement telling us it would happen. Cannot remember the reason though.
     
    Christmas Trip. Sam's Town & MSS
  3. hillwood24

    hillwood24 High-Roller

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    I only know this because I read a lot of aircraft forums, but the sound you hear is the hydraulic transfer mechanism that is running before the second engine is started. Most airlines these days only use one engine to taxi the aircraft to save fuel, so you'll hear this sound whenever only one engine is powering the aircraft.

    Basically the mechanism transfers the hydraulic power to the other side of the aircraft so that the pilots can operate the controls on that side. With only one engine running, they would only have hydraulic power on one side of the aircraft. This mechanism allows both sides of the aircraft controls to receive power from just the one engine.

    The sound will go away before you get to the runway because the second engine will have been started sometime between pushback from the gate and arrival at the takeoff runway. With the second engine producing its own power for that side of the aircraft, the transfer mechanism is no longer needed.

    Most likely you were on an Airbus A320 or one of the aircraft in that family. They have done this forever, and it's actually a "good" sound to hear in the sense that the hydraulic systems are working as designed.

    I hope this answers your question.
     
  4. gilly from philly

    gilly from philly Low-Roller

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  5. dmr

    dmr Registered Abuser

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    Thanks, gang. :)
     
  6. Royal Flusher

    Royal Flusher Savvy Gambler

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    I just thought it was the sound of the engines struggling...
     
  7. smartone

    smartone VIP Whale

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    Ha! Me Too! Great answer Hillwood!
     
  8. Sonya

    Sonya Queen of VMB

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    Wow. VMBers really do know everything. :nworthy:
     
  9. dfalk

    dfalk VIP Whale

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    It's the flux capacitor charging up.
     
  10. Aces and Eights

    Aces and Eights VIP Whale

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    NO, NO, NO, You don't know what you're talking about! It's the dilithium crystals getting the engines ready for warp drive.
     
  11. dewey089

    dewey089 Guru of Value

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  12. Joe Strummer

    Joe Strummer VIP Whale

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    I always thought it was the wheels retracting ?
     
  13. Breeze147

    Breeze147 Button Man

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    Aye, Captain, I'm givin' ya all she's got!
     
  14. sindustry

    sindustry VIP Whale

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    It's that invisible monster thing from the TV Series "Lost". Be careful, your plane may divert off the west coast and end up on a deserted island.
     
  15. Electroguy563

    Electroguy563 Over-Fried Gambler

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    I thought this also. Always sounds and seems like something's gonna break.
     
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  16. wigwam_salesman

    wigwam_salesman VIP Whale

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    I just asked a buddy who has the misfortune to fly for Ryanair in Europe and he said if the PTU is going at rotate (when they pull back) you should't be taking off! It should never have a loss of pressure when both engines are spooled up.

    He also said it could be one of a load of things depending on the type of aircraft as they all make certain distinct ones. Do you know what type of aircraft it is?
     
  17. Snidely

    Snidely VIP Whale

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