Helicopter Sinks Fast.

Discussion in 'Aerodynamics, Physics and Engineering' started by HungryHungryHippos, Jun 4, 2014.

By HungryHungryHippos on Jun 4, 2014 at 11:45 PM
  1. HungryHungryHippos

    HungryHungryHippos Well-Known Member

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    This isn't a problem, its more of a curiosity / observation.

    Lately, at night time after work (its winter where I am with a 5:20 pm sunset) I have been doing hovering / light circuits / figure 8's at a soccer park with decent lighting at night, but only when no one is around. (I dont want to do anything more than this at a public park for safety reasons).

    The helicopter is a Hirobo Lepton, Jeti Hacker Speedie, Scorpion engine, No electronic governor setup in the Vbar software.

    At this time the air is rather still, no wind, and cold.

    Sometimes, when hovering and leaving the collective alone, the helicopter slowly creeps up to a higher level, over 8 to 10 meters, then starts to sink rapidly.

    Is this because I could be hitting a small local inversion layer (going into warm air)? or is the speedy starting to get warm?
     
    1. Ant

      Ant Guest

      You don't say how low the model is when you are hovering, but it seems you are in ground effect. The blades are generating lift and the descending air is hitting the ground which creates a cushion of air. This now becomes more dense that the air around it and therefore the model rises until it gets to an altitude where ground effect disappears.
       
    2. HungryHungryHippos

      HungryHungryHippos Well-Known Member

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      I was hovering at around 2 to 4 meters when it started slowly rising to 8 or so meters, then starts sinking.

      This particular soccer field is sunken into the ground, and the rest of the land area outside of the soccer field area is 8 or 10 meters above the soccer field, I am wondering if the soccer field traps cold dense air.

      Could it be the ground effect cushion of air is much higher than normal under these conditions?
       
    3. Ant

      Ant Guest

      It's possible. Cold air is pretty dense and will settle on the ground.
       

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