Here is an excerpt from a previous posting here, author unknown but
knowledgeable. While he/she doesn't specificly address the "hover" alone
an explanation can be derived from it;

? O.K. Here we go!



As soon as we get off the ground we notice a tendency for the
helicopter to drift to the right due to the tail-rotor's thrust, so a
little left cyclic *pressure* is necessary to stay over one spot. I say
pressure because that's all it takes. Much more than that and the
helicopter will go too far to the left and slip off the "cushion" of
high-pressure air it is producing under the rotor and will settle to the
ground if power is not added. Not only that, but a series of
pilot-induced oscillations on all axes may develop. Let's say that we
move the cyclic to the left to correct for tail-rotor drift, and have to
suddenly move it back to the right to correct for the over-correction.
Now we find ourselves swinging back and forth to an increasing and
alarming extent. This is due to the helicopter's mass acting as a
pendulum under the spinning rotor, which tends to stay put much like a
spinning top. This is appropriately called "pendular effect". Not to
over-complicate things, but pendular effect is not the worst thing to
deal with when in a hover. Let's say that we experience tail-rotor drift
and correct for it using left cyclic pressure. Although the rotor is
still producing the same amount of thrust, we have just converted some
of that lifting thrust (called "lift component") to lateral thrust
("thrust component") by tilting the rotor disc slightly. To avoid
settling to the ground, we must add some lift component by adding
collective and simultaneously adding enough throttle to maintain rotor
RPM. While doing that we notice that the nose of the helicopter wants
to go to the right due to the increase in torque, so we add some left
pedal pressure, which stops the nose from moving, but since the tail
rotor needed more power to do that, and it doesn't have its own engine,
we had to steal some power from the main rotor. (Ya faller me?) Now
that the rotor has less power, the helicopter wants to settle to the
ground again, so we need to add more collective and more throttle and
more pedal... now you're too high! Uh oh! Less collective! Less
power! Right pedal! Now you're drifting to the left due to less thrust
from the tail rotor! Watch that rotor RPM! Better get outa this hover
and away

from the ground where its safe!



Now here's the fun part. Gently feed forward cyclic pressure and
simultaneous collective/throttle (and don't forget left pedal) until we
begin to gain forward speed. Now we just lost two good things:

Ground effect, which is that cushion I mentioned, and lift component
since we tilted the rotor forward. Just add some collective/throttle to
keep from digging a hole, and the appropriate amount of pedal to

hold heading. We quickly gain forward speed until we gain a good thing
to replace the two good things we just lost: translational lift.
Translational lift is what people are referring to when they say that a
helicopter's rotor system acts like a wing in forward flight. Kinda
sorta, but not exactly. It *flies* much the same but not because of
wing-like properties. It is simply because the helicopter now has a
constant supply of "still" air to climb upon, rather than sitting in its
own accelerated column of air. We can either

choose to nose over a bit more or reduce power and stay near the ground
to accelerate some more, or let the helicopter climb with its newfound
extra rotor efficiency--its your choice. (O.K., we skimmed the ground
'cause its fun.) Now we need to get over those trees...c'mon, that's
enough! Now, ease back on the cyclic enough to maintain good climb
speed and up we go like that Ferris wheel you used to hate so much.



The easiest part of all needs little explanation. Just do all the
same stuff you do in an airplane plus watch your rotor RPM. When you
want to turn, give it a little pedal to coordinate. Hold speed by
holding *attitude* with the cyclic, hold altitude with the collective.
Easy, huh? There's a little more to it, but you might not notice it
while in flight. Some things change with speed, and some mostly
sub-conscious corrections need to be made, but there are limits to
sub-conscious flight techniques. The following

paragraph is optional reading for those who only want a very basic
explanation of helicopter flight. (this involves math) :-)



Due to the rotor spinning rapidly, and the helicopter as a whole
moving forward, we have to deal with "dissymmetry of lift". Dissymmetry
of lift comes from one side of the rotating rotor disc moving into the
direction of travel of the helicopter, and the other side moving away
from it. The net effect is to add the speed of the helicopter to the
rotor's rotational speed on the dvancing side, and conversely to
subtract the forward speed of the helicopter from the retreating side of
the rotor. If the rotor has a rotational speed of 400 MPH at the tips,
and the helicopter is traveling at 100 MPH through the air, the net
speed of the advancing side of the rotor is 500 MPH. Under the same
conditions, the net speed of the retreating side is 300 MPH. If an
airplane tried to run its right wing through the air at 500 MPH and run
its left wing

through the air at 300 MPH, it would be doing snap-rolls until it
crashed. Dissymmetry of lift is the primary obstacle the helicopter
faces in significantly improving on current top speed records. Above the
approved top speed of a helicopter, the rotor blades are alternately
experiencing the extremes of Mach buffet, and of reverse flow...450
times a minute. The resulting rapid oscillation of center of pressure
on each blade can lead to catastrophic rotor system failure. The
vibration is a warning. The control effect as speed increases is that
the helicopter rolls towards the retreating side, and is corrected by
adjusting cyclic pressure against the roll. This is done without much
thinking except to re-trim the cyclic when speed changes significantly.
Another change that isn't really noticed is that the tail-rotor doesn't
need to work as hard at higher speeds due to the weather vane effect of
the tail boom. Airfoils are often placed on the boom to unload the
tail-rotor

at high speed/high power settings and free up power for lift/thrust.



This is boring as hell, so now we're going to land
somewhere...anywhere. See any place you want to stop and have a picnic?
How 'bout that little pond with the ducks and the waterfall tucked into
that gorge? Let's land on that sand bar. This is one place where those
fixed-wingers won't bother us.



Losing speed and altitude is basically the reverse process of
gaining them. To hold altitude and lose speed you ease back on the
cyclic to flare and reduce speed while lowering collective/throttle just
enough to hold altitude and maintain rotor RPM. To lose altitude
without losing speed, lower

collective/throttle until the desired rate of decent is reached. A
combination of both is usually used for approach to landing. At the
point of loss of translational lift, the rotor system will vibrate a
bit, but you're used to it by now (you'll be a bit numb by the end of
the flight). Besides, you'll be somewhat distracted by the sinking
feeling, followed by the confusion of having the nose suddenly jerk to
the right when you yank up on the collective

to stop sinking. (forgot that left pedal again, eh?) Anyway, when
you've established a hover (hopefully in ground effect and over a clean,
level spot) you can decrease collective until touching the ground. That
was an over-simplification, but you get the idea. Now we can eat.
Don't freak out too badly when you notice those wires--damn close, but
you're alive!




"Wannafly" wrote in message
oups.com...
Hello, what are the control inputs required in a hover in an ideal
situation, what I am trying to figure out is what are you doing in a
no-wind situation to hover.