andymcallister
Veteran
Location: Palm Beach, Florida
| Im not sure if this is right but it is a condition called vortex ring in real helicopters. I have had it happen in my Raptor 30 several times. Here is an in depth but hopefully helpful insight into vortex ring state taht was tken from my website so It may not be completely accurate for your case, but my bet is that what you described was Vortex Ring:
Vortex Ring or "Settling with power" is a dangerous condition that is always present in helicopters. Lets say we have our R/C helicopter hovering at 30ft in front of us, with no wind. Basically a helicopter sucks air down through the disc and blows it out the bottom, this creates very disturbed air underneath the helicopter which the blades do not cut well through and become less efficient. If we take a little power off our helicopter hovering at 30ft to try and bring it into a 2ft hover to land and we descend at more than about 2-3ft per second, chances are we will get into vortex ring state. Because the helicopter is descending straight down it will descend right into its own downwash, the blades become less effective and the helicopter will descend faster. If we add power to slow the rate of descent it will probably make the condition worse because all we are doing is making more downwash below the helicopter, which it will move down into, and so on. Now since our models are so grosly overpowered for their size it is sometime possible to climb out of vortex ring by applying full power, but in the real helicopters this is not possible. The correct action should you get into a vortex ring state should be to lower the collective slightly, and push the nose forward, this will move the helicopter out of the downwash and into nice fresh air again. To get into vortex ring a helicopter needs 3 states to be apparent;
- Power applied (eg not in an auto)
- Airspeed less than about 10mph (in strong headwinds the helicopter will act as if it is moving forward through the air, so vortex ring cannot occur as the downwash is behind the helicopter.)
- And a rate of descentgreater than around 1.5-3ft per second (this can vary drastically by the model used)
If one of these 3 states is not present vortex ring cannot occur. So if we are in an auto its will not happen as the air flow through the disc is reversed and going from below the helicopter to above it, If we are flying forward it cannot happen because we are leaving the downwash behind us, and if we descend slow enough the downwash will always follow us down and we won't fall into it. So the correct way to get from the 30ft hover we are in to a 2ft hover from landing would not be to just lower the collective and begin a straight down descent, as this would produce all 3 states.
You explained you began to move forward but if you weren't moving forward fast enough/had a tail wind then it wouldn't have mattered. |
