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b.
Severe
overheating
will result
in general
weakening
of
the
metal
that
results
in soft and
spongy
spots.
These
are usually
found
directly
Never
blow air
through the
line
toward
the
opposite
the
cross-over
passages.
They can be
instrument
panel;
to do
so will
seriously
detected
by
tapping
lightly
with
a
ball peen
hammer·
damage
the
instruments.
When
blowing
This will
give a slightly
soft
or
spongy
response
in
back
through
the
line
from
the
instrument
contrast
to
a solid
feel when
tapping
on live metal.
panel,
make
sure
that
no air is blown
These
soft spots
will usually
have
a
dull gray
into
the
instruments.
appearance
indicating
considerable
surface
oxidation.
The presence
of
soft
spots
is reason
for rejecting
NOTE
the
combustion
chamber
and
radiator
assembly.
Wax or polish
applied
to the
static
air
buttons
can
cause
wrong
instrument
!CAUTIONÀ
readings.
The static
air buttons
should
be
cleaned
periodically
with a cleansing
If
any
soft
spots are located
in
the
combustion
solution
to
insure
that
no
film
exists
on
chamber and
radiator
assembly,
there
is a
the static air
buttons.
malfunction
in
the
heater
system
and a new
heater
should
not be installed
until
the
Drain
the
static
air
line by opening
the
access
door
trouble
has been corrected•
in
the
rear
baggage
compartment
and removing
the
section
of
rubber
hose.
Disconnect
the
line at
the
HEATER
OVERHAUL
airspeed
indicator
and
blow
this
line
clear.
On
aircraft
serials
TD-638
and after,
the
system
is
The heater
should
be pressure
tested
every
500
drained
at
the
emergency
static
air source
located
hours
of
heater
operation
or
1000
hours
of
aircraft
on
the
left wall of
the
cockpit,
below
the
instrument
operation and
overhauled
every
1500 hours
of
panel.
The system
is
drained
by
turning
the
knob
to
heater
operation
or 3000 hours of aircraft
operation.
the
emergency
static air
position.
Return the
knob
to the
normal
position
after
the
line is competely
drained.
Frequent
draining
of
the
static
air line is
recommended
when
the
humidity
is high or when
HEATER
PRESSURE
TEST
heavy
moisture
(dew,
rain
or wash
down) is en-
countered.
The following
information
is intended
to
serve
as
a
guide
for
testing
Janitrol
heaters
without
removal
from
the
aircraft.
This
test
will determine
whether
TESTING
THE PITOT
SYSTEM
FOR
LEAKS
leakage
through the
combustion
chamber
is within
the
allowable
limits
or if
the
heater
should
be
A functional
test
of
the
pitot
system
can
be
made by
overhauled.
using an
observer
in
the
cabin
to
watch
the
airspeed
indicator
while air
pressure
is built up artificially
To conduct
this test,
seal
the
fuel
inlet,
the
com-
by
using
a section
of soft rubber
tubing
as
follows;
bustion
air
inlet and
the
exhaust opening. Connect
an
air line
to the
heater
drain connection.
This
a. Clamp
the
rubber
tubing
over
the
pitot head
air
line should
have
two
shutoff valves
in series
to
inlet,
making
certain
that the
connection
is airtight.
assure
positive
air
shutoff
and
a
20 inch
mercury
manometer
(or an accurate
pressure
gage)
located
b.
Crimp
the
end
of
the tubing
and slowly
roll it
between
the
shutoff
valves
and
the
heater.
Slowly
up until
the
airspeed
indicator
registers
approxi-
apply air pressure
till the
gage
has a reading
of 7
mately
100 miles
per
hour.
psi
or 14.25
inches
of
mercury,
then
lock in
the
air
pressure
by closing
both
shutoff
valves.
The
(CAUTION)
maximum
allowable pressure
drop
of 2. 5
psi
or
5.
l inches
of
mercury
represents
normal
leakage
To avoid rupturing
the
diaphragm
of
the
air-
at fittings and gaskets.
If
the
pressure
drop is in
speed
indicator,
roll
up
the
rubber
tubing
excess,
the
heater
should
be
overhauled.
slowly and do
not build up
excessive
pressure
in
the
line.
c.
Secure
the
rolled
up
tubing
so
that
it will hold
CLEANING
THE
STATIC
AIR SYSTEM
the
airspeed
indicator
reading.
Blow
low
pressure
air
through
the
lines
from
the
d.
If
there
is no decline
in
the
reading
after
several
disconnected
line
at
the
air-speed
indicator
to the
minutes,
there
is
no
leak in
the
pitot system.
static
ports.
Cover each
static
port
separately
when
blowing
to
insure
that
each
line is
clear.
Instrument
e. If a decline
in
the
reading
of
the
airspeed
indi-
error
or
possible
damage could result
if even
one
cator
is
observed,
check
the
pitot system
plumbing
port is clogged
with
dirt or foreign
matter,
for leaky hoses
and
loose connections.
3-27
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Table of Contents
Troubleshooting
