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Old 01-22-2012, 11:05 PM
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broncoboy36081
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Default RE: beginner heli pilot needs help

Very well put!!!!!!!!!!!!!!!!!!!!!
ORIGINAL: ArtW

There are three very separate issues that you are confusing. The first is the thrust from the rotor necessary to hovering is greater than that for forward flight. In forward flight there is transitional lift from air coming into the rotor plane from I front of the heli. When one stops to hover additional lift is necessary from that level for forward flight. You must either increase rotor speed in a fixed pitch heli which takes time secondary to the inertia of the rotor head or increase pitch in a collective pitch heli. The second issue is ground effect. When you are within one rotor diameter of the ground there is increased lift from the back pressure of the rotor wash hitting the ground. So less lift is necessary as you hover within one rotor diameter of the ground than at higher altitudes. The third issue is the ring vortex state. If you descend vertically through your roter wash at more than 500 feet per minute in a full sized heli or some speed in an RC you can force air to recirculate and decrease lift. This also happens when you try to hover or land in an enclosed space like a walled court yard. The heli that crashed in Abattabod likely had ring vortex state loss of lift trying to descend rapidly into a walled compound. They had practiced with walls that were permeable (cyclone fence) and then had ring vortex when the walls were solid. So you must separate these effects when thinking of how to decelerate to hover prior to landing. In full size helis there are weight loadings and altitude/temperature situations where they can't hover prior to landing and must land with forward velocity to take advantage of the transitional lift. What you need to practice is slowing to a hover prior to decent to allow the fixed pitch rotor time to speed up so you can hover in ground effect. Then slow the rotor speed to land.