Cessna 402B 1973 - Page 43

MOMENTARY OVERBOOST
OF
MANIFOI.D PRESSURE
Under some circumstances
(such-as
rapid
throttle
movement,
espe-
cially
with
cold oil) it
is
possible
that
the
engine can
be
overboosted
above
the
ma:<imum
allowable
madfold
pressure
of
34. 5
inches Hg.
This would
most likely
be
experienced during
the
takeoff
roll
or during a change
to
full
throttle
operation
in
flight. Therefore, it is
still necessary that
the
pilot
observe
and be
prepared
to control
the
manifold
pressure.
Slight
overboosting
is not
considered
detrimental
to the
engine
so long
as
it is
momenta.ry. Momentary overboost
of
2
to
3 inches
Hg.
can
usual-
ly
be
controlled
by
slower throttle
movement and no
correetive
action is
required
when
momentary overboost
corrects itself
and is followed
by
normal
engine operation.
However, if overboosting
of
this
nature
per-
sists, or
if
the amourt
of
overboost
goes
as high
as 4
inches
Hg.
or
more,
the controller
system should
be
checked
for
necessary
replace'ment
or
ad-
justment
of components.
ALTITUDE
OPERATION
Because
your
turbocharged
aircraft
will
climb
faster and
higher than
a
normally
aspirated
aircraJt,
fuel
vaporizaton
may
be encountered
and
the following
items
should
be
remembered:
(1)
Turn the auxiliary
fuel
boost
pumps
ON
when
climbing
to
alti-
fudes
above
12,000 feet. By
turning the fuel
boost
pumps
ON
when climbing
through
12,000
feet,
the
vaporization
problem
is eliminated.
The fuel
boost
pumps
should be left ON several
minutes
after
cruise
in
level
fiight
has
been established.
(2)
Lean the
mixture
during the climb to the
proper
fuel
flow for the
power
being used.
HIGH ALTITUDE
ENGlNE
ACCELERATION
Your
engine
will
accelerate normally
from
idle
to
futl
throttle with fuII
rich
mixture
at any
altitude below 16,000
feet.
At higher
altitudes,
it
is
usually necessnry to lean the mixture
to
get
smooth
engine acceleration
from
idle
to
ma:<imum
power.
At
altitudes
above 25,000
feet, and with
temperatures above
standard,
it takes one
to two
minutes
for the
turbine
to accelerate from idle to
maximum
RPM,
although adequate
power
is
available
in
20
to
30 seconds.
2-38