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B Helicopter in spin

  1. Sep 30, 2016 #1
    I understand a helicopter in spin would mean a stabilizer is gone and the helicopter cannot maintain its stable altitude. However, I've noticed that helicopters have a tendency not to dip in free fall. I mention that bc I am curious as to what force is at play when objects and people (sorry for morbid picture) fall out. My understanding is that the helicopter falling disturbs the wind making it pick up in speed. I believe it is Newton's third law at play bc I've noticed that objects will fall out in the opposite direction relative to the motion of the helicopter. I'm sorry if it truly is simple as gravity causes people fall out but I'm unsure. I will also state that the objects could appear to fall in the opposite direction bc they are no longer moving with the plane.
     
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  3. Sep 30, 2016 #2

    Drakkith

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    I'd bet this is the primary factor. Most objects falling out of a helicopter don't have the mass to alter the flight of the helicopter enough to notice any force pairs (action-reaction forces). In other words, they won't push on the helicopter enough to noticeably move it. The only exception might be with helicopters transporting heavy cargo (Chinooks transporting tanks for example).
     
  4. Sep 30, 2016 #3
    Thank you! That clears up a bit of it but what is the force causing the object to get pulled out of the helicopter?
     
  5. Sep 30, 2016 #4

    CWatters

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    Can you clarify the question as it's very confusing...

    What do you mean by dip? Do you mean they don't pitch nose down like a fixed wing aircraft would if it lost its tail? Fixed wing aircraft pitch nose down for two reasons 1) the center of gravity is normally located in front of the center of lift. 2) a typical cambered wing section produces a nose down pitching moment. The tail plane is setup to produce a nose up pitching moment to counter these effects. So loose the tailplane and it pitches nose down.

    On a helicopter the centre of lift is closer to or on the centre of gravity so a horizontal tailplane may not be needed. The tail rotor is primarily to counter engine torque.


    Again it's not clear what you mean by opposite direction?

    If the helicopter rotor is still producing some lift it won't fall vertically at the same rate of acceleration as someone who jumps out. The person may fall faster than the helicopter.

    If the helicopter is moving forward when a person jumps out then the person will slow down (in the horizontal direction) due to air resistance and may appear to be "left behind" as they fall. They don't actually start moving in the opposite direction but it can appear so if the camera continues to follow the helicopter.
     
  6. Sep 30, 2016 #5

    A.T.

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    No need to feel sorry, unless you pushed them.
     
  7. Sep 30, 2016 #6
    Ok, the rotor takes a hit or possibly some stabilizer. Then, the helicopter starts to lose altitude bc there is a malfunctioning rotor. The helicopter starts to spin, right? What makes it appear as though objects get sucked out? It's not decompression like on a plane but could be I guess? I don't think it's gravity either. I'm saying a critical failure has occurred and the helicopter starts to fall out of the sky. The objects not strapped down get sucked out. I'm asking what force or physical principle is the cause of this.
     
  8. Sep 30, 2016 #7
    Centrifugal force (aka the inertial force experienced by objects in the non-inertial reference frame of the spinning helicopter).
     
  9. Sep 30, 2016 #8

    Drakkith

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    I wasn't aware this even happened. I suppose centrifugal force could have some effect, but I have no idea how much. Are you sure this is an actual phenomenon and not a myth?
     
  10. Oct 1, 2016 #9

    CWatters

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    What ulianjay said. If the tail rotor fails the engine torque can cause the whole helicopter to spin and centrifugal force can cause things or people to fly out of any open doors.
     
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