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the blade rotation (it's the left one
with North American rotation, that is,
anticlockwise as viewed from the
top). It is therefore totally normal
for one skid to be lower than the
other, unless you've left the
refuelling hose in (actually, this
characteristic is quite useful when
Principles of Flight 33
landing on sloping ground, as long
as the slope goes with the skids).
To combat this, you could raise the
tail rotor on a boom or lower the
rotor head, as is done with the
Brantly, but the C of G position
could screw that up anyway.
Tail Rotor Failure
When the tail rotor fails, it will be in
varying degrees of positive, neutral
or negative pitch, depending on what
you were doing at the time, so if you
can remember what it was, you will
have an idea of the state of the
pedals. Unless it’s a drive failure, or
you lose some of the components,
the chances are that you won’t
discover the problem until you
change your power setting, as it’s
very unlikely you’ll be flying along in
the cruise, for instance, and find a
pedal forcing itself completely over
to one side, as simulated by
instructors on test flights, unless you
have a motoring servo or similar, in
which case your problem is
hydraulics and not the tail rotor,
although the effect might be the
same. More typically, you will be in a
descent, climb, cruise or hover, with
the pedals where they should be and
won’t move when you want to do
something else. When descending,
for example, in the AS350, you will
have more left pedal (more right in
the Bell 206), both of which will aid
the natural movement of the
fuselage against the main rotors. The
pedals would be in a neutral position
if you were flying at medium to high
speeds, and the power pedal would
be forward in high-power situations,
like hovering. In any case, the spread
between the pedals is not likely to be
more than a couple of inches either
way, certainly in a 206 – try an
autorotation properly trimmed out
to see what I mean. You will notice
the same in the hover. My point is
that the situation may not be as bad
as frequently painted.
In fact, landing with a power pedal
jammed forward is relatively easy,
since the tail rotor is already in a
position to accept high power
settings (try also using a little left
forward cyclic in a 206, and pivoting
round the left forward skid), so you
may be able to come in very slowly
and even hover. If the pedals jam the
other way (right in a 206), look for
more speed because there will not be
enough antitorque thrust available.
A drive failure, on the other hand, or
loss of a component, will cause an
uncontrollable yaw, and maybe an
engine overspeed, so the immediate
reaction should be to enter
autorotation, keeping up forward
speed to maintain some directional
control (which is difficult in the
hover, so try to get one skid on the
ground at least), if you have time. If
you lose a component, the C of G
may shift as well, although an aft one
in general has been found to help
with this situation. Pilots who have
been there report that there is a
significant increase in noise with a
drive shaft failure, and that the
centrifugal force in the spin is quite
severe. Anyhow, an autorotation is
certainly part of the game plan, and
as speed is reduced towards
touchdown, you will yaw
progressively with less control
available in proportion, so it may be
worth trying to strike the ground
with the tailwheel or skid first (if
you’ve got one), which will help you
to keep straight—according to the
34 JAR Private Pilot Studies
JetRanger flight manual, you should
touchdown with the throttle fully
closed, as you would if the failure
occurs in the hover, to stop further
yaw when pitch is pulled to cushion
the landing.
However, in some circumstances,
such as the cruise, sudden
movements like this may not be the
best solution. If you can reduce the
throttle and increase the collective,
this would reduce the effect of the
tail rotor at the same time as keeping
the lift from the main rotors, as does
beeping down to the bottom of the
governor range (difficult in most
AS350s or Gazelles, where the
throttle is not on the collective). The
tail rotor is there to counteract
torque, so if you give it less work to
do, you will be more successful.
　
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