(d)
Descent
The descent data will be determined prior to the cruise data to provide the descent distance for
establishing the total cruise distance.
Utilizing the cruise pressure altitude and OAT we determine the basic time, distance and
fuel for descent (Figure 5-25). These figures must be adjusted for the field pressure altitude and
temperature at the destination airport. To find the necessary adjustment values, use the existing
pressure altitude and temperature conditions at the destination airport as variables to find the
time, distance and fuel values from the graph (Figure 5-25). Now, subtract the values obtained
from the field conditions from the values obtained from the cruise conditions to find the true
time, distance and fuel values needed for the flight plan.
The values obtained by proper utilization of the graphs for the descent segment of our
example are shown below.
(1)
Time to Descend (6.5 min. minus 3.5 min.)
3.0 min.*
(2)
Distance to Descend (14 miles minus 7.5 miles)
6.5 miles*
(3)
Fuel to Descend (1.0 gal. minus.5 gal.)
.5 gal.*
(e)
Cruise
Using the total distance to be traveled during the flight, subtract the previously calculated
distance to climb and distance to descend to establish the total cruise distance. Refer to the
appropriate Avco Lycoming Operator’s Manual when selecting the cruise power setting. The
established pressure altitude and temperature values and the selected cruise power should now be
utilized to determine the true airspeed from the Cruise Performance graph (Figures 5-15 through
5-18).
Calculate the cruise fuel consumption for the cruise power setting from the information
provided by the Avco Lycoming Operator’s Manual.
The cruise time is found by dividing the cruise distance by the cruise speed and the cruise
fuel is found by multiplying the cruise fuel consumption by the cruise time.
The cruise calculations established for the cruise segment of our flight planning example are
as follows:
(1)
Total Distance
300 miles
(2)
Cruise Distance
(e)(1)minus (c)(4) minus (d)(2), (300 minus
10 miles minus 6.5 miles)
283.5 miles
(3)
Cruise Power, Best Economy Mixture
75% rated power (2645 RPM)
(4)
Cruise Speed
118 KTS TAS**
(5)
Cruise Fuel Consumption
8.5 GPH
(6)
Cruise Time
(e)(2) divided by (c)(4), (283.5 miles divided by 118 KTS)
2.40 hrs.
(7)
Cruise Fuel
(e)(5) multiplied by (e)(6), (8.5 GPH multiplied by 2.40 hrs.)
20.4 gal.
* reference Figure 5-25
** reference Figure 5-17
ISSUED: DECEMBER 16, 1976
REPORT: VB-880
REVISED: MAY 30, 1980
5-5
PIPER AIRCRAFT CORPORATION
SECTION 5
PA-28-161, CHEROKEE WARRIOR II
PERFORMANCE
Summary of Contents for CHEROKEE WARRIOR II
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