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PART
III
UTILITY SYSTEMS
3.1
DESCRIPTION
This
section covers
the maintenance, trouble
shooting
and repair of
special
systems installed for
the
comfort
and
safety of
the
occupants, or systems
to
be
employed
only under special
conditions.
Covered
herein
are
the heating and defrosting
system,
ven-
tilating
system,
the assist step mechanism
and
nose
wheel
steering system.
3.2
HEATING AND VENTILATING SYSTEM
3.2.1
Description -
Air
for
the heating
and
ventilating system
of
the B-50 is taken in through an
opening
in
the fuse-
lage
nose.
An iris valve, immediately back of
th
e in-
take
opening,
is
operated
from the cabin to regulate
the
volume of incoming
air. For ground
operation,
an electrically-driven
blower is mounted in
the
in-
take
duct,
to the right
of
the
nose wheel
well.
From
the blower,
air
is ducted through a 50,000
BTU
heat-
er.
Cold
air for
the front cabin
outlet
is bled
from
the
blower adapter
case.
Just ahead
of the
heater,
cold
air
is
bled off and ducted to three rear seat
outlets,
two in the left and
one
in the right cabin
walls.
The heater
is
mounted beneath the floor panel
of
the
nose baggage
compartment,
to the
right
of
the nose
wheel well. Hot air from the heater enters a
plenum
on the
aft wall
of
the baggage compartment,
then
is
ducted to the windshield
defroster
outlets
and
an out-
let
for
each
seat. The
outlet for the
rear
seat
is
to
the right
of
center
of
the front
seat
base, the
fr ont
seat outlet is on the
bulkhead
between
the cabin and
nose baggage compartment,
opening directly
into
the
plenum.
3.2.1.1
Heater
and Fuel System
-
The heater,
located in
the
lower right
nose
baggage compartment,
is essentially
a cylindrical
combustion chamber
within
a
hollow radiator
and
surrounded by a jacket.
Incoming
ventilation air
passes between the combustion
chamber and the
ra-
diator,
and
between
the radiator
and
the jacket,
in a
straight line for
the full length
of
the heater. Fuel
is
sprayed
from a
nozzle
a
t one
end
of the
combus-
tion chamber and
ignited by
a
spark
plug which
op-
erates continuously
whenever
the heater is in use.
Combustion air,
bled
from the blower adapter is for-
ced into
the
chamber
at
a
tangent
and
mixed with the
fuel spray, producing a
swirling
flame. The flame
travels the full length of
the
combus
tion
chamber and
the hot gases are
ducted
to
the radiator where they
again travel the
full length
of the heater before being
exhausted
overboard.
Fuel is supplied
to
the
hea
ter
from the right
main wing tank,
by
an electric
fuel
pump mounted in
the right wheel
well.
Fuel
fl ow
is
shut
off
by two
solenoid
valves,
one
in
the right
wheel well and
the
other
in
the
nose wheel
well. The
heater
spark
plug receives
high voltage
current
from
an ignition
unit mounted
on the left
side
of the nose
wheel well.
The ignition unit consists of
a
high-ten-
1
sion
coll,
similar
to an automobile
ignition coil, a
condenser and a vibrator with two
sets of contacts.
A
push-pull
switch on
the unit, normally
safety-wired
to the
"IN"
position may be pulled
out,
while
on the
ground, to place the
alternate
contacts ln
service if
the
normal
contacts
fall. The switch
s hould
be
safety
wired
so
that the
normal
contacts are in service.
3.2.1.2
Thermostats
and
Controls -
Cabin temperature is controlled by
a
ther-
mostat
mounted
on
the aft bulkhead above the
seat.
This
thermostat
ls adjusted within a range
of
2 de-
gree C (35 degrees
F}
and
30 degrees C
(85
degrees
F}
by
a rheostat mounted
on
the right
subpanel.
Signals
from
the
cabin thermostat
operate
a relay
mounted
on
the
generator control box,
tbtPPVb
which
the
heater igniter,
heater
fuel pump and the norm-
ally-closed
heater fuel
valves are energized. A
second
thermostat is
connected in
ser~
es with the cabin
thermos tat;
installed
in
the heater
plenum, this thermo-
stat
prevents
excessively-hot
air
from
entering the
ducts
by
s
hutting
off
the heater whenever
the plenum
temperature reaches 66 degrees C
(150 degrees F).
An other
thermostat in the intake duct,
also in series
with the cabin
therm
ostat, was removed
by
Service
Bulletin
No.
9,
which also added
a switch
to
the cabin
thermostat
control
rheostat.
This
switch perm its
turning
the heater
on
or
off
as
desired, although the
control circuit
itself
is energized whenever the bat-
tery
and
heater
and
blower circuit breaker
switches
are
on.
The action
of the
150 degree
thermostat
results in the
intermittent operation, or
cycling,
of the
heater
as a
normal
function;
the duration and
frequency
of
the
cycles
will vary with the
outside
air
temperature.
A
second
thermostat in the plenum
is connected through
a resistor
to
the heater system fuse on the
generator
control box.
If,
through a malfunction, the
temperature
in the plenum should rise to 149 degrees C
(300 degrees
F) this thermostat will close and
ground
the
fuse, which
opens all
heater
circuits.
Both the heater
and
the static air
blower
are
controlled by a toggle switch
circuit
breaker
on
the right
subpanel.
In normal operation, this
switch
is left
"ON"
at all times. The blower,
intended for
ground operation
only, is controlled by a switch act-
uated by the same lever
as
the landing gear
control
switch;
thus, when the gear is raised
on
take-
off,
the
blower is switched off simultaneously. In
flight, ram
air
a
lone is
sufficient
for heating
and
ventilation.
An
additional switch, on
the ventilation
a
ir valve
control
turns
off
both the blower
and
the heater when
the con-
trol is pulled
out
more than halfway.
Cold air for the rear
seat is regulated
by
rotating the
covers
on the three individual duct op-
enings.
A
push-pull control on the right
subpanel
operates an iris valve
in
the duct behind the
instru-
ment panel to regulate the cold
air supply to
the
fr ont
seat.
No individual controls
are
provided
for
the cabin heat.
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