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are driven from a common shaft.
The igniter plug is not next to the
fuel nozzle, but is inserted in either
side of the combustion can.
Transmission
Mounted forward of the engine and
coupled to it with a short drive shaft,
with heat detection strips that turn
black when they get too hot. It is a
reduction gearbox that transmits
power from the engine through
spiral bevel and planetary gears to
the main rotors. It has a selfcontained
lubrication system with its
own oil cooler, and the hydraulic
pump and rotor tacho are also
attached, so you still get hydraulics
during autorotation (however, you
still need power, so if the hydraulics
fail, pray the electrics don’t go as
well). It is secured by an isolation
mount to minimise vibration.
The tail rotor drive shaft has eight
sections, with the forward one
connected to the back end of the
freewheel unit. The second section is
actually the oil cooler fan shaft,
connected to the tail boom splice
with the third section.
There are two spiral bevel gears
inside the tail rotor gear box, which
transfers the transmission forces
through 90°.
In the LongRanger, a nodal-beam
setup is coupled with an elastomeric
restraint for a generally vibrationfree
ride. The chip detector on the
free wheeling unit is electrically
connected to the TRANS CHIP
warning light
Rotors
The main rotors are a “droop-snoot”
design, and semi-rigid, using an
underslung-feathering-axis hub,
which has only six grease-lubricated
bearings (the grease, MIL G 81322,
can make a real mess when you do
the 50-hour service. It’s good down
to –65F). They use North American
rotation, that is, anti-clockwise when
viewed from the top, and carry 24
lbs of weight each to help provide
high inertia. In fact, it is possible to
cut the engine on the ground, pull
the machine up into a hover and
(very quickly) spin through 180°, or
more, before putting it on the
ground again. The main rotor hub
has a flap restraint system (the
“bunny ears”) to prevent droop at
low RPM. The maximum deflection
applied to the blade is 24 inches, or
roughly level with the bottom of the
tail rotor cover.
The tail rotor is also two-bladed and
semi-rigid. Because the bottom blade
goes forward, it is a pusher. Large
amounts of it can be missing, and
you will still be able to fly, either
with 50% gone from the end of a
blade, or with a big hole in it.
The Bell 206 145
Controls
Consist of push-pull control tubes
and bell cranks, which are routed
through the “broom cupboard”
behind and in-between the front
seats. They are hydraulically
powered, which means you have
power steering. Bearings and rod
ends don’t need lubrication. Three
servo actuators with irreversible
valves (so you don’t get feedback
forces) are located forward of the
main transmission, in the
“doghouse”, for the cyclic and
collective.
The valves isolate the servo system
from the flight controls.
The hydraulic system operates at 600
psi and contains a pint of (MIL-L-
5606) fluid.
In the LongRanger, the pressure
remains the same, but the pump is a
variable displacement type with e
remote reservoir. The three servos
are different as well, and there are
two filters, with buttons that need to
be checked on a daily inspection.
Electrics
28 volts DC, from a 24-volt nicad or
lead-acid battery and a 28.5-volt
combination starter-generator which
pushes out 150 amps. In theory, you
should be able to get 6 starts out of a
battery with 65% capacity. All
circuits are single-wire with a
common ground return. High
generator loads will be reflected in
the TOT, since the starter/generator
is on the compressor drive train
(N1). Because the torquemeter is on
the N2 train, it will not show
anything. This is the reason the
generator is often turned off during
power checks (in fact, when hot and
high, many pilots turn off the
generator to give themselves a little
leeway on the TOT when lifting). 1
Kw is about 1.34 HP, so drawing
100 watts on a 28 volt system is
pulling down about 3.75 HP, so in
the hover you could lose about 34
lbs of hover capability, at 9 lbs per
HP. The starter can draw 300-400
amps for the first few seconds.
Switches and circuit breakers are on
the overhead console. There is an
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The Helicopter Pilot’s Handbook(96)
