SECTION 5
CESSNA
PERFORMANCE
MODEL 172RG
CRUISE CONDITIONS
Total distance
425 Nautical Miles
Pressure altitude
7500 Feet
Temperature
16°C (16°C above standard)
Expected wind enroute
10 Knot Headwind
LANDING CONDITIONS
Field pressure altitude
2000 Feet
Temperature
25° C
Field length
3000 Feet
TAKEOFF
The takeoff distance chart, figure 5-4, should be consulted, keeping in
mind that the distances shown are based on the short field technique.
Conservative distances can be established by reading the chart at the next
higher value of weight, altitude and temperature. For example, in this
particular sample problem, the takeoff distance information presented for
a weight of 2650 pounds, pressure altitude of 2000 feet and a temperature of
30°C should be used and results in the following:
Ground roll
1410 Feet
Total distance to clear a 50-foot obstacle
2380 Feet
These distances are well within the available takeoff field length.
However, a correction for the effect of wind may be made based on Note 3 of
the takeoff chart. The correction for a 12 knot headwind is:
This results in the following distances, corrected for wind:
CESSNA
SECTION 5
MODEL 172RG
PERFORMANCE
CRUISE
The cruising altitude should be selected based on a consideration of
trip length, winds aloft, and the airplane's performance. A 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
approximately 65% will be used.
The cruise performance chart for 8000 feet pressure altitude is entered
using 20°C above standard temperature. These values most nearly corres-
pond to the planned altitude and expected temperature conditions. The
power setting chosen is 2300 RPM and 22 inches of manifold pressure,
which results in the following:
Power
65%
True airspeed
132 Knots
Cruise fuel flow
8.8 GPH
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 5-6 and 5-7. For this sample problem,
figure 5-6 shows that a normal climb from 2000 feet to 8000 feet requires 2.4
gallons of fuel. The corresponding distance during the climb is 20 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 10% for each 10°C above standard temperature, due to
the lower rate of climb. In this case, assuming a temperature 16°C above
standard, the correction would be:
5-4
1 July 1979
1 July 1979
5-5
