Cessna 172P - Fuel Required

CESSNA
MODEL
172P
SECTION 5
PER,FORMANCE
CRUISE
The
cruising
altitude
should be selected based on a consideration
of
trip
length, winds
aloft, and
the airplane's
performanoe.
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
deter-
mined
based on several
considerations.
These include the cruise
perfor-
rna,noe
characteristics
presented
in figure õ-7, the ra,nge
profile
chart
presented
in figure
õ-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 ra,nge result when
lower
power
settings
are used. For this sample
problem,
a cruise
power
of
approximately
66Vo
will be used.
The cruise
performance
chert,
figuro õ-7, is entered at
6000 feet altitude
and
20oC above
standard
temperature. These values most nea,rly corres-
pond
to the
planned
altitude
end expected temperature
conditions.
The
engine
speed
chosen is
2500 RPM, which results in the following:
Power
667o
True
airspeed
112 Knots
Cruise fuel
flow 7.4
GPH
The
power
computer
may be used
to doterrnine
poÌver
and fuel conaump-
tion
more accurately
during
the flight.
'ruel
REoUtRED
The
total
fuel requirement
for the flight
may be
estimated
using the
performance
information
in figures
5-6 and
5-7. For this sampte
problem,
figure 5-6
shows that
a climb
from 2000
feet to 6000
feet requiros
1.6
gallons
of
fuel. The
corresponding
distance
during the climb is 10 nautical miles.
These
va,Iues
are
for a
standard
temperature
and
are sufficiently
a,ccurate
for
most
flight
planning
purposes.
However, a further
correction
for
the
effect of
temperature
may
be made
as noted
on
the
climb
chart. The
approximate
effect
of a
non-standard
temperature
is to increase the time,
fuel,
and
distance
by lOVo
for each
10oC
above standard
temperature,
due to
the lower
rate
of
climb.
In this
case, a,ssuming
a temperature 16oC above
standard,
the
correction
would
be:
13€'
Lovo
=
r6vo Increase
30
May
1980
5-5