Section V. CRUISE
The cruise charts (figs 7-7 thru 7-17) present the level-
flight torque required and total fuel flow at various condi-
tions of airspeed, pressure altitude, free air temperature,
and gross weight. Cruise charts are provided for pressure
altitudes from sea level to 16,000 feet in 2000-foot incre-
ments. Free air temperatures range from 50
C increments. In addition to basic cruise information,
the charts show speed for maximum range, maximum en-
durance, and maximum rate of climb. Change in torque
with change in frontal area information is presented in the
upper left corner of each chart.
7.20 USE OF CHARTS.
The primary uses of the charts are illustrated by the exam-
ples. To use the charts, it is usually necessary to know the
planned pressure altitude, estimated free air temperature,
planned cruise speed, IAS, and gross weight. First, select
the proper chart on the basis of pressure altitude and FAT.
Enter the chart at the cruise airspeed, IAS, move right and
read TAS, move left to the gross weight, move down and
read torque required, and then move up and read associ-
ated fuel flow. Maximum performance conditions are de-
termined by entering the chart where the maximum range
line or the maximum endurance and rate-of-climb line in-
tersects the gross weight line; then read airspeed, fuel
flow, and torque required. Normally, sufficient accuracy
can be obtained by selecting the chart nearest the
planned cruising altitude and FAT or, more conservatively,
by selecting the chart with the next higher altitude and
FAT. If greater accuracy is required, interpolation between
altitudes and/or temperatures is permissible. To be con-
servative, use the gross weight at the beginning of the
cruise flight. For greater accuracy on long flights, howev-
er, it is preferable to determine cruise information for sev-
eral flight segments to allow for the decreasing gross
True and indicated airspeeds are pre-
sented at opposite sides of each chart. On any chart,
indicated airspeed can be directly converted to true air-
speed (or vice versa) by reading directly across the chart
without regard for the other chart information. The appli-
cable MACH No. or gross weight maximum permissable
airspeed limits (VNE) determined from figure 5-2 appear
on the appropriate charts.
Since pressure altitude and tempera-
ture are fixed for each chart, torque required varies ac-
cording to gross weight and airspeed. The torque required
and the torque limits shown on these charts are for dual
engine operation. The torque available shown on these
charts are maximum continuous torque available and
maximum torque available, 30 minute limit, where less
than the maximum torque-two-engine transmission limit.
These torque lines are the maximum torque available for
ATF = 1 at the TGT specified in Chapter 5. Higher torque
than that represented by these lines may be used if it is
available without exceeding the limitations presented in
Chapter 5. The limit torque line shown on these charts is
for dual engine transmission limit and is defined as 100%
torque. An increase or decrease in torque required be-
cause of drag area change is calculated by adding or sub-
tracting the change in torque from the torque change (DQ)
curve on the chart, and then reading the new total fuel
7.20.3 Fuel Flow.
Fuel flow scales are provided oppo-
site the torque scales. On any chart, torque may be con-
verted directly to fuel flow without regard to other chart in-
formation. Sea level ground fuel flow at flat pitch and
100% NP is approximately 550 pounds per hour.
7.20.4 Maximum Range.
The maximum range lines in-
dicate the combinations of gross weight and airspeed that
will produce the greatest flight range per pound of fuel un-
der zero wind conditions.
7.20.5 Maximum Endurance and Rate of Climb.
maximum endurance and rate of climb lines indicate the
combinations of gross weight and airspeed that will pro-
duce the maximum endurance and the maximum rate of
climb. The torque required for level flight at this condition
is a minimum, providing a minimum fuel flow (maximum
endurance) and a maximum torque change available for
climb (maximum rate of climb).
7.20.6 Change in Frontal Area.
Since the cruise infor-
mation is given for the primary mission configuration, ad-
justments to torque should be made when operating with
alternative wing-stores configurations. To determine the
change in torque, first obtain the appropriate multiplying
factor from the drag chart (fig 7-18), then enter the cruise
chart at the planned cruise speed TAS, move right to the
broken DQ line, and move up and read DQ. Multiply DQ
by the multiplying factor to obtain change in torque, then
add or subtract change