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areas of any city, town or settlement.
Dispensations will be required to fly
near nuclear installations and
prisons, just in case they think you're
part of an escape plan.
Flights should also be confined to
within 300 feet of the lines
concerned (but no closer than 1 ½
rotor diameters to the lines when
level, or 1 diameter plus 30 feet
when above). Flying above and to
the right is most preferable. In
addition, lines should be crossed
vertically at least 100 feet above
them (common sense dictates that
you should do this over a pylon
rather than the lines themselves).
You will not be allowed closer than
100 feet to any people or vehicles
directly concerned with line
operations and 200 feet to any other
structures than those to do with the
lines themselves. You shouldn't, but
if you have to go under a wire, get
your skids on the ground as near to a
pylon as possible.
As well as the proper permissions,
other problems include insurance.
Ensure that whatever you get also
covers you for frightened animals
bolting and causing havoc—this
usually happens with sharply
changing noise levels caused by rapid
manoeuvres. If you can't help flying
over animals, at least try not to chase
them through the fence!
60 The Helicopter Pilot’s Handbook
Line patrol should not normally
happen if the visibility is less than
about 1 mile, and 2 if raining (1 mile
is approximately 6 towers or poles
ahead). These limits are higher than
usual because moisture will stick to
the windscreen at slower speeds, and
things are further complicated if you
have no windscreen wipers, as
precipitation won't blow away either.
Under those conditions, speeding up
to get rid of water is not what you
want to be doing, especially when
those grey towers merge into the
weather! Give serious consideration
to aborting if there is a lot of rain,
although really heavy stuff will tend
to run off better than the light
variety. Also, line patrol should not
normally be attempted if the wind is
above 25 knots, and the cloudbase
below 400 feet.
Lines are patrolled at whatever speed
is comfortable, generally between 20
or 50 knots, a little above pole height
and to one side, depending on what
is being looked for. This could be
just trees encroaching on the wires,
but also could be lightning damage.
Observers will normally be on the
opposite side to you so the lines will
be closest to them. They make
commentaries on tape which are
later transcribed into useful
information.
Always try to follow the line as near
into wind as possible, or, if not, in
trim at least, which will help if you
lose tail rotor authority. If it's around
10 knots or so, being downwind
generally will only ensure the transit
time along the wire is too fast, with
the consequent danger of you trying
to slow down and having no
airspeed—if more it may be rough as
well, especially in the mountains.
Monitor the instruments and be
particularly aware of overtorquing or
overtemping. Don't forget tail rotor
and wire strikes, and other lines
(especially tower lines) crossing—the
observers will be too busy to assist
your lookout. If a closer inspection
is called for, DO NOT try to come
to the hover and backtrack, but gain
height and speed, positively identify
the area and make a conventional
circuit and approach to come to the
hover alongside the line into wind.
A constant lookout must be
maintained at all times, especially for
fast, low flying military aircraft, so
High Intensity Strobe Lights (HISLs),
nav lights, landing lights and anticollision
beacons must be on at all
times. HISLs should be at least 2000
candela in power (so don’t drop one
or you’ll have to pick them all up). If
they become unserviceable, patrol
above 500 feet. Don't plan on doing
more than two to three hours per
day due to the high workload.
Wires
70% of wirestrikes happen with
highly experienced pilots, and
around 50% happen in clear sky
conditions. Very often, a wire that is
seen on the way into a landing spot
is either missed or forgotten about
on the way out – it is therefore a
good practice to circle a spot on the
way in, to give yourself the best
chance of catching any wires that
may be present.
If you cannot see wires themselves,
there are often clues to their
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The Helicopter Pilot’s Handbook(40)
