Cessna T188C - Page 261

MODEL
188 & T188
SERIES SERVICE
MANUAL
On
aircraft beginning with 18801825,
the yellow right 12-54.
AUXILIARY FUEL PUMP RATE
ADJUST-
half of the switch is labeled "START," and its upper MENT.
"ON"
position is used for normal
starting, minor
vapor purging and continued engine operation in the WARNING
event of an engine-driven pump failure. With the
right half
of the switch
in the "ON" position,
the
Large
amounts of raw
fuel are drained
from
pump operates at one
of two flow rates that are de-
the engine compartment
during engine stopped
pendent upon the setting of
the throttle. With the
test. Therefore, a suitable
drip pan should
throttle open to a cruise
setting, the pump operates
be placed under engine
compartment and all
at a high
enough capacity
to supply sufficient
fuel
safety
precautions
observed to prevent
igni-
flow
to maintain
flight with
an inoperative
engine-
tion
of fumes.
driven
fuel pump.
When the throttle
is moved
toward
the closed position
(as during
letdown,
landing and
NOTE
taxiing), the fuel pump flow rate is automatically re-
duced,
preventing
an excessively
rich
mixture
during
On
12V Aircraft,
adjust
AMOR 20-1.
5 resis-
these periods
of reduced engine speed.
tor to
1.0 ± .25 OHMS, and AMOR
20-5 to
2.0 .25 OHMS prior to installation. On
NOTE 24V Aircraft, adjust AMOR 20-10 resistor
to 3. 5 . 5 OHMS prior to installation.
If the engine-driven fuel pump is functioning
and
the auxiliary
fuel pump switch
is placed
a.
Make the following
adjustments
with engine
in the "ON" position,
a fuel/air ratio con-
stopped, and
using external power:
siderably
richer than
best power is produced
1. Apply
13.75 VDC
± .25V on 12V
aircraft,
unless the
mixture is leaned. Therefore,
and 28. 8 VDC
* .25V on 24V aircraft, to
the bus.
this
switch should
be turned
off during
take-
2.
Set Mixture:
FULL RICH.
off.
3. Set Throttle: FULL
OPEN.
4. Turn boost pump rocker switch (yellow) ON.
· CAUTION
5. Adjust
number one resistor until
a fuel flow
of 14.7 - 16.0 gallons/hr. is indicated.
If the
auxiliary fuel pump switch is
acciden- 6. Retard
throttle to IDLE. Pump
should change
tally placed in
the "ON" position
with the
to
slower speed
as the throttle
passes the marked
master switch on and the engine stopped, position.
the intake
manifolds will be flooded.
7. Adjust
number two resistor until an
approx-
imate 4 gallons/hr flow is indicated. This reading
The red left half
of the switch
is labeled "EMERG,"
will
be on the low
end red line or
approximately
one
and its upper "HI" position
is used in the event of
an red line - width - above
the low end red line.
engine-driven fuel pump failure during take-off or
high
power operation. The
"HI" position may also be
NOTE
used for extreme
vapor purging.
Maximum
fuel flow
is
produced when
the left half of
the switch is
held in
On 24V aircraft,
low setting
is made by ad-
the spring-loaded
"HI" position.
In this position,
an
justing number
two resistor
to minimum
interlock within the switch
automatically trips the
resistance position.
Gage reading will be
right half
of the switch
to the "ON"
position. When
just
above the
lower red line
(3. 5 psi).
the spring-loaded
left
half of the switch
is released,
This is maximum
available
low position.
the right half will remain in the "ON" position until
manually returned
to the "OFF"
position.
12-55. EMERGENCY
BOOST
CHECK. With
ex-
ternal power
applied, and
bus voltage on
12V air-
12-53. RIGGING
THROTTLE MICROSWITCH.
craft at 13.75
VDC ± . 25V, and on 24V aircraft
at
a.
With engine
running, advance
the throttle
to 28.
8 VDC .25V,
make the following
check.
obtain a
manifold pressure of over:
20" Hg on
I. Engine: Stopped.
normally aspirated
and fuel injected engines,
and 2.
Set Mixture: FULL RICH.
25" Hg on turbocharged
engines.
3. Set
Throttle: FULL OPEN.
b. Slowly retard
the throttle, and mark the throttle
4. EMERGENCY
fuel switch (RED): HELD ON.
position
at: 20" Hg on
normally aspirated
and fuel
5.
The fuel flow gage
must indicate
a noticeable
injected
engines.
and 25"
Hg on turbocharged
models.
increase
in fuel flow.
c. Stop the engine, and adjust the switch located at
the bottom of the throttle quadrant to actuate on the WARNING
previously
marked
positions.
Large
amounts of raw
fuel are
drained from
NOTE
the
engine compartment
during
engine
stopped
test.
Therefore, a
suitable drip
pan should
Switch
bracket
may
have to be
modified
on
be placed
under engine
compartment
and all
the aft end to allow proper
adjustment.
safety precautions
observed to prevent igni-
tion of fumes.
12-26