Takeoff to a Hover from a Slope
This maneuver is used to transition the helicopter from a parked position
on a slope, into a normal hover.
With the RPM within the normal operating range, the pilot displaces the
cyclic toward the slope. Depending on the circumstances, he might put
just the amount he thinks is required, or on a steeper slope he may elect
to put all available cyclic into the hill to start with. The intent is
not to tip the rotor toward the hill, but to have the main rotor disk
level with the horizon, or tipped just slightly into the hill.
As power is increased, the downhill skid will eventually lift up. During
this phase of the maneuver, collective is controlling the height of the
skid, and cyclic is simply trying to maintain the rotor system level with
the horizon. As the fuselage rolls uphill, the swashplate and therefore
the rotor system tip with it, and the pilot has to take out some of his
uphill cyclic in order to maintain the rotor level with the horizon.
The collective should be slowly raised until the downhill skid is level
with the uphill skid. Cyclic should continue to be manipulated to maintain
a level rotor system. It is critical that the downhill skid does not get
raised above the uphill skid. Doing so starts biasing the equation toward
dynamic rollover a lot. This is because not only may some main
rotor thrust be trying to roll us uphill, but the CG is shifting toward
the uphill skid, and thus any restoring force preventing dynamic rollover
is being reduced.
Once the skids are level, remove any remaining uphill rotor thrust by
moving the cyclic away from the hill. It is normally very apparent when
there is no main rotor thrust into the hill, because the helicopter will
suddenly become much less stable on the hillside. Continue to center the
cyclic, and increase power to cause the helicopter to lift straight up.
Continue up to your desired hover height.
Not using enough uphill cyclic
If you don't have enough uphill cyclic, such that the rotor is tipped
downhill, the uphill skid may be the first to lift off, or the helicopter
may try to slide downhill, or it may simply dynamically roll downhill.
Needless to say, none of these are fun, and it's probably safer to carry
too much uphill cyclic at the start of the maneuver rather than not enough
Using too much uphill cyclic
This usually happens because people put in a certain amount of uphill
cyclic, and then as the helicopter rolls to a level attitude they either
don't take out any of the uphill cyclic, or they just don't take out
enough. This leaves you with a lot of thrust toward the uphill side,
which can easilly turn into a dynamic rollover uphill. Practice will
show you just the right amount of uphill cyclic you should be holding
when skids level.
Rolling uphill too fast
Hamfisted manipulation of the collective can induce a very fast uphill
roll which may be difficult to arrest. In extreme circumstances, there may
be enough uphill roll momentum to cause an uphill dynamic rollover. The
downhill skid should be brought up very slowly. I usually teach bringing
it up a few inches and pausing, then a few more inches and pausing, and
so forth until the skids are level. This insures no roll momentum gets built
Overcontrolling the cyclic
People who are nervous on a slope will tend to overcontrol. Moving the
cyclic forward and backward will tend to unlock the uphill skid, making
the helicopter unstable on the slope. This happens when only one part of
the skid is left in contact with the ground. This could be either a heel
or a toe, and creates a pivot point which requires lots of pedal work to
handle. A properly locked in uphill skid has both toe and heel planted,
and provides a very stable platform with almost no pedal work required.
Overcontrolling the cyclic in roll almost always means the person is
confused about what control commands the height of the downhill skid.
The cyclic can wobble the downhill skid up and down a bit, and this may
lead people to think they are on the right track, especially since this
is the proper control input in normal flight. It is important to realize
that as long as one skid is planted, the height of the other skid is
controlled by rotor thrust, i.e. the collective.
Not centering the cyclic before vertical liftoff to a hover
If the cyclic is still displaced into the hillside when a vertical
liftoff is attempted, the helicopter will perform a distinct wobble
as it leaves the ground. While not particularly dangerous in small
amounts, it leaves some doubts as to the ability of the pilot to
properly operate on a slope.
Allowing the tail rotor to swing toward the slope
Once in a hover, the pilot has to remain concious of the tail rotor and
avoid swinging it toward the hillside.
paul at copters.com
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