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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
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
Techie Stuff 259
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.
Otherwise, you might find a power
and speed combination that will
maintain height until you find a
suitable landing area, then you've got
as much time as your fuel lasts to
solve the problem. Don't forget that
the cyclic can be useful for changing
direction and enabling you to fly
sideways to create drag from the tail
boom and vertical stabiliser, for
example. It's the sort of situation
where it pays to be creative
sometimes. After all, the aim is to
walk away, not necessarily to
preserve the machine. Two other
things you can try if you finally make
the hover—stirring the cyclic so as
to dump lift, and pumping the
collective to produce a similar effect.
Both will serve to confuse the
machine enough so it forgets which
way to turn! With a jammed power
pedal (left, in a 206), what also works
is to crab in the way the machine
wants to, come to a high hover
sideways and let the machine settle
by itself. You will find very little
input is required by you.
If you want to run-on for landing,
get the wind and/or nose off to the
retreating blade side, so the fuselage
is crabbing, and control your
(shallow) descent with a
combination of throttle and
collective, applying more of the
latter as the throttle is closed just
before touchdown so you run on
straight. Note that some helicopters
(such as twins, or the AStar) won’t
let you use the throttle as precisely as
that. Not only that, you may well be
so busy that worrying about minor
details like the wind’s exact quarter
will be the last thing on your mind.
For a running landing, on most
machines, about 30% torque at 30
kts will put you in a good position
for landing at 30 ft, and a little
power at the last minute will put
your nose nicely straight. For the
non-power pedal, keeping straight
involves either more speed or less
power, and you have to accept more
of a run-on.
In an AStar (or TwinStar), the
recommendation in the book is to
come in with some left sideslip (i.e.
crabbing right). Slow down until the
nose starts to move to the left, and
you have your landing speed.
Loss of Tail Rotor Effectiveness
This is sometimes known as tail rotor
breakaway, or a stall, which is not
strictly correct, as thrust is still being
produced – it’s just not enough for
the task in hand. It shows up as a
sudden, uncommanded right yaw
(with North American rotation), and
has amongst its causes high density
altitudes, high power settings, low
airspeeds (below about 30 kts) and
　
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