"I think I understand why.  Here's my theory: Winds near the ground (generally below 20 feet) are naturally turbulent.  In essence, this means that the aerodynamic forces change quickly and randomly.  The single-rotor/tail-rotor…"

"woooaaaauuuuu!"

"Yes, but there are also other elements at play.  One thing is that helicopters also have better aerodynamics that quads.  They are simply less affected by the wind.  Also, i think the rotor disk offers better control reactions for…"

"@Paul G.: In order to be efficient, you need a large rotor disk area.  Full-size helicopters would be extremely hazardous on the ground if the rotor was not at least 7 feet high (for obvious reasons).  This does make them less stable, but…"

"See this thread for more information in 2012. "

"Yes."

"Hi Taylor, I'm having some serious glitches on my quad, but my bullet connectors don't turn when i try to, would you still solder them?"

"Looks great, What price range do you think a finished frame will be in?"