SECTION VII. CRUISE
The cruise charts, figures 7-7-1 through 7-7-84, present
torque requirements and fuel flow for cruise flight as a
function of airspeed and gross weight for various com-
binations of pressure altitude and free air temperature.
Dot pattern (shaded) area indicates time limited opera-
7-7-2. Use of Charts.
The primary use of charts is illustrated by the example
cruise chart (fig. 7-7-1). To use the charts it is usually
necessary to know the planned PA, estimated FAT,
planned cruise TAS, and the GW. First select the proper
chart based on PA and free air temperature. Enter the
chart at the cruise TAS, move right and read IAS, move
left to the GW, move down and read torque required, then
move up and read associated fuel flow. Maximum perfor-
mance conditions are determined by entering the chart
where the maximum range line or maximum endurance
and rate of climb (R/C) line intersect the gross weight
line: then read airspeed, fuel flow, and torque required.
Normally, sufficient accuracy can be obtained by select-
ing the chart nearest to the planned cruising altitude and
FAT, or move conservatively, by selecting the chart with
the next higher altitude and FAT (example cruise chart,
method one). If greater accuracy is required, interpola-
tion between altitudes and/or temperatures is permissi-
ble (example cruise chart, method two). To be conserva-
tive, use the GW at the beginning of the cruise flight. For
improved accuracy or long flights, it is preferable to deter-
mine cruise information for several flight segments to
allow for decreasing GW.
a. Airspeed. True and indicated airspeeds are
presented at opposite sides of each chart. On any chart,
IAS can be directly converted to TAS (or vice versa) by
reading directly across the chart without regard to other
chart information. Estimated airspeed limits with an
operating CGI appear as dashed lines on each chart.
Airspeed limits with the CGI inoperative are presented
in the airspeed limits section of Chapter 5.
Airspeed limitations with an operative cruise
guide indicator are per the indicator display.
Estimated values shown on these cruise
charts are for information only, as an aid to
b. Torque. Since PA and temperature are defined for
each chart, torque required varies only with GW and
airspeed. The torque required per engine as presented
on the charts is for dual engine operation. The torque
required for single engine operation is double the dual
engine torque value for any given condition. See cruise
chart example 2 for example on torque required. With
EAPS installed there is no significant change in torque
required. The torque available limits shown are either
transmission or engine torque limits (whichever is least).
c. Fuel Flow. The fuel flow scales presented on each
chart opposite the torque scales are for dual engine
operation. Torque may be converted directly to fuel flow
on any chart without regard to other chart information. A
single engine fuel flow chart is presented in Section X.
Torque required for any given condition as obtained from
the preceding cruise charts should be doubled before
being used to obtain single engine fuel flow from this
d. Maximum Range. Maximum range lines indicate
optimum GW/cruise speed conditions with respect to
distance covered per pound of fuel consumed for zero
e. Maximum Endurance and Rate of Climb. Maxi-
mum endurance and rate of climb lines indicate opti-
mum GW / cruise speed conditions for maximum
endurance and maximum rate of climb. These condi-
tions require minimum fuel flow (maximum endurance)
and provide maximum torque change for climb (maxi-
mum rate of climb). This airspeed also represents the
best single engine airspeed.
The cruise charts are based on 100% RRPM for ambient
temperatures of 10_C and above, and 98% and 100%
RRPM for ambient temperatures of 20_C and below.
7-7-4. Performance Penalties with EAPS.
The engine performance loss with EAPS installed is
shown in table 7-7-1. The corrections shown in the table
are to be applied to the applicable to the applicable per-
formance data shown on Chapter 7.