Cessna 17273274 Pilot Operating Handbook page 75

CESSNA
MODEL 172N
CRUISE
The cruising altitude should be selected based on a consideration of
trip length, winds aloft , a nd the airplane's performance. 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
mance 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. For this sample problem, a cruise power of
65%
approximately
The cruise performance chart, figure
°
and 20 C above standard temperature. These values most nearly corres­
pond to the planned altitude and expected temperature conditions. The
engine speed chosen is 2500 RPM, which results in the following:
Power
True airspeed
Cruise fuel flow
The power computer may be used to determine power and fuel consump­
tion more accurately during the flight.
FUEL REQUIRED
The total fuel requirement for the flight may be estimated using the
performance information in figures
figure 5-6 shows that a climb from 2000 feet to 6000 feet requires 1.3 gallons
of fuel. The corresponding distance during the climb is 9 nautical miles.
These values are for a standard temperature and are sufficiently accurate
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
the lower rate of climb. In this case, assuming a temperature 16
standard, the correction would be:
1 July 1979
will be used.
5-7,
5-6
and
°
10%
for each 10 C above standard temperature, due to
°
16 C
10% 16%
c" = Increase
10 0
SECTION 5
PERFORMANCE
6000
is entered at feet altitude
64%
114 Knots
7.1 GPH
5-7.
For this sample problem,
°
C above
5-5