to a Hover This maneuver is used to transition the helicopter from a
parked position on the ground, into a normal hover.
Description With the RPM within the normal operating range, the pilot
performs the maneuver by increasing power. As power is increased, more
anti-torque pedal will be required in most single rotor helicopters. The
increase in tail rotor thrust will typically require a cyclic input to
counter tail rotor roll tendency. The problem with these required
adjustments is that since the fuselage is sitting on the ground, there is
no visual feedback to the pilot that he is making the proper inputs.
As the power is increased enough to get the helicopter light on the
skids, the pilot will begin to receive feedback about whether his control
positions are correct. For instance, sliding around on the ground, or
pitching and rolling motions may all be signs that the cyclic is not
centered. Yawing on the ground is an indication that the pedals are
You will have to continue to manipulate the controls
in order to hold position on the ground during the liftoff. Failure to do
so can result in a dynamic rollover situation, which can destroy the
aircraft. Continue to raise collective until the helicopter transitions
into the air. Continue to slowly and smoothly increase collective until
the desired hover height is achieved.
As the helicopter leaves the
ground, don't be in the habit of pausing at 1/2 inch skid height to get
the controls centered before climbing to a normal hover height. Wallowing
around at a low skid height is asking to catch a skid on something. Just
continue smoothly up to your normal hover height. On the other hand,
don't be in the habit of "popping" the helicopter up to a normal
hover height. This is a common technique with inexperienced pilots who
are trying to get away from the ground. If you are getting your controls
centered, there should be no reason to rapidly climb to your hover height,
and there are several good reasons not to. The climb to a hover should be
slow, and at a steady rate. By going slowly, you have time to identify
and correct problems as they occur.
How to center the controls
properly This seems to be a constant problem for many pilots. Many pilots
I fly with have never been taught how to properly do this (and thus many
of them revert to the "pop it off" technique).
pedals are pretty easy to learn how to do. First of all, go find a smooth
paved area which can allow you to yaw the aircraft on the ground without
risk of rollover. Be careful. From flat pitch, being increasing power
until you are starting to get a little light. Play with your pedals. If
you push enough on the right pedal, the helicopter will try to yaw right
on the ground. If you push enough on the left pedal, the helicopter will
try to yaw left on the ground. Halfway in between is where the pedals are
neutralizing engine torque.
Now increase power a bit, and repeat the
exercise. The amount you will have to push the pedals before the
helicopter wants to yaw is reduced. The lighter you get, the less you
have to push the pedals to yaw, and the narrower the range is where the
pedals must be to keep the helicopter straight. If you keep doing this
until the helicopter is lifting off, you will be able to judge exactly
where the pedals have to be to prevent any yaw during liftoff. Of course,
since you are adding more and more engine torque, the centered position
will be moving more and more toward the left as you perform the exercise.
With practice, you will be able to neutralize pedals without any large yaw
forces being placed on the helicopter.
Keep in mind that this is an
exercise. As a normal procedure, you don't want to be yawing the aircraft
while it is on the ground. This can result in an accident. The trick is
to learn how to move the pedals just a little bit, watch for small
indications of yaw on the aircraft, and therefore learn exactly where to
put the pedals so no yaw takes place. If you have access to a pontoon
equipped helicopter, practicing pickups on the water will really teach you
to use the anti-torque pedals.
Cyclic, Pitch Axis This exercise is
similar to what we did with the pedals. Instead of yawing, we will be
practicing pitching the helicopter forward and backward. Be extremely
careful with backward, since skids are not designed to slide that way, and
you could hit the tail rotor if you allow the helicopter to rock back.
Get the helicopter light on the skids. Push some forward cyclic, and
then some rearward cyclic. Feel the helicopter attempt to rock (or slide)
forward and backward. Halfway in between is where the cyclic is centered.
As you get lighter and lighter, the amount you have to move the cyclic is
reduced. As the helicopter is ready to lift off, any movement of the
cyclic will cause the helicopter to rock or slide. You have found the
center position if you can prevent it from rocking and sliding as the
helicopter is ready to pick up.
Now comes the difficult part. All
helicopters will want to pitch nose up or down into whatever attitude they
want to hover in. This is usually a different attitude from the skids
level attitude. If you try to prevent this from occurring, the helicopter
will slide forwards or backwards depending on the attitude it wants to
hover in. Many things will influence the hover attitude, including the CG
of the helicopter. The trick is to figure out which attitude it wants to
hover in, given that you are sitting on the ground. Of course, experience
will tell you to some degree how a helicopter wants to hover given it's
CG, but you should be able to walk up to a strange helicopter and still
perform a good liftoff.
The key is to realize that the helicopter will
side forward or backward unless it is in the correct pitch attitude. As
power is increased, position the cyclic so that the helicopter won't
slide. Add more power and notice whether the nose or tail wants to rise.
Let the aircraft pitch up or down, but as it does counter the motion with
cyclic, just as you do on a slope landing. The idea is not to stop the
pitching motion, but to prevent the rotating swash plate (and therefore
the main rotor) from pitching with the fuselage. If you have input the
correct amount of cyclic, the aircraft has pitched, but still does not
want to slide on the ground. Continue adding power, and countering
fuselage pitch until the helicopter lifts off. If you do a really good
job, you will first feel the front or rear of the aircraft lift off, then
one of the remaining skids, and then finally the heel or toe of the
remaining skid, all without any sliding around on the ground. This takes
a lot of practice, but will allow you to make very accurate, smooth
Cyclic, Roll Axis This part of the exercise is similar to
what we just discussed in the pitch axis, however you need to use even
more caution. If you allow the helicopter to skid laterally, you risk
dynamic rollover. If you allow the helicopter to come up on one skid
(which it normally wants to do) and then slide toward that skid, you are
really asking for dynamic rollover. You might want to have an
instructor along while you practice this...
Again, the problem is
similar to that of the pitch axis. The helicopter in a hover will
normally hover one skid lower than the other because of various factors
including CG. Your job is to transition from skids on the ground
(presumably level) to skids at the hover attitude. You don't know what
the hover attitude is yet. So you increase power a bit, and play
carefully with lateral cyclic to try and determine where it is centered.
You continue to increase power to get light on the skids, and adjust the
cyclic to prevent sliding. At some point the helicopter is going to want
to roll, and you have to let it, but you do want to counter with opposite
cyclic so that the rotating swash plate doesn't roll with the helicopter.
If you do this correctly, the helicopter will roll but not slide, until
it is left with one skid in the air, and one skid on the ground, ready to
lift off. Continued up collective will cause the final skid to leave the
ground with no rolling motion at all, simply a straight up motion. If the
helicopter wobbles as it leaves the ground, you didn't have the cyclic
centered and you need more practice!
Helicopters with oleo
(shocks/struts) equipped landing gear Pilots who fly helicopters with
oleos (such as Enstroms, MDHC/Hughes) have an advantage in that they can
"fly" the fuselage while the skids are still on the ground.
Since you can rock the aircraft on the oleos, it is much more obvious when
the cyclic is centered.
Helicopters that dance when light on the skids
Some fully articulated aircraft perform a little (or huge!) dance when
light on the skids. This is like ground resonance, only it hasn't
diverged yet. It is caused by an interaction of the dampers and struts,
and can get so bad in some aircraft that you can't read the gauges.
Sometimes this is an indication that you've got a bad damper, or that the
dampers aren't all adjusted to the same force. You can check the dampers
with a fish scale; seeing that it takes the same force to move each blade.
Our Enstrom does this, and my advice is that it isn't good (or
comfortable!) to sit with the skids banging away on the ground. Either
find some soft ground that damps the motion, or simply avoid it by
minimizing the amount of time that you sit light on the skids.
together now You can normally practice all these simultaneously. Get the
helicopter light, and play with the pedals. Play with the cyclic in the
Play with the cyclic in the roll axis. Increase the
power slightly and repeat.
Keep in mind during all this that I'm not
advocating sliding around on the ground. That is a very dangerous thing
to do. What I am suggesting is that you look for the cues that tell you
when the aircraft controls are centered versus displaced.
learning those cues, you can center the controls and perform a perfect
takeoff to a hover every time.