Cessna 172N - Page 67

CESSNA
MODEL
172N
SECTION
5
PER,FORMANCE
CR
UISE
The cruising
altitude
should
be
selected based on a
consideration
of
trip
length,
winds
aloft,
and the airplane's
performanee.
A typical
cruising
altitude
and
the
expected
wind
enroute
have been
given
for
this
sample
problem.
However, the
power
setting
selection
for
cruise
must
be
determined
based on
several considerations.
These
include
the
cruise
performance
characteristics presented
in
figure
5-7, the range
profile
chart
presented
in
figure 5-8,
and the
endurance
profile
chart
presented
in figure
5-9.
The relationship
between
power
and range
is illustrated
by
the
range
profile
chart.
Considerable fuel
savings
and longer
range
result
when
lower
power
settings
are
used.
The range profile
chart
indicates
that use
of. 65Vo
power
at
5500 feet
yields
a
predicted
range
of
523
nautical
miles
with no
wind.
The
endu-
ranee profile
chart,
figure
5-9,
shows a corresponding
4.2
hours.
The range
figure
of 523
nautical
miles
is
corrected to account
for
the
expected 10
knot headwind
at 5500 feet.
This
indicates
that the trip
can be made
without
a
fuel
stop
using
ap-
proximately
65Vo
power.
The cruise performance
chart,
figure 5-7,
is
entered
at G000 feet
altitude
and 20oC
above
standard temperature.
These values
most
nearly
correspond
to the
pianned
aititude
and
expected
temperature
conditions.
The
engine
speed chosen is
2500 RPM,
which
results
in
the
following:
Range,
zero
wind
Decrease
in range
due to wind
(4.7
hours
"
10 knot
headwind)
Corrected range
Power
True airspeed
Cruise
fuel
flow
523
47
476
Nautical
Miles
647o
114 Knots
7.1
GPH
The
power
computer
may be
used
to
determine
power
and
fuel
con-
sumption
more
accurately
during
the
fllght.
FUEL
REOUIRED
The total
fuel
requirement
for
the flight
may be estimated
using
the
5-5