TM 1-1520-238-10
7-14
in torque from torque required for the primary mission
configuration. Enter the cruise chart at resulting torque re-
quired, move up, and read fuel flow. If the resulting torque
required exceeds the governing torque limit, the torque re-
quired must be reduced to the limit. The resulting reduc-
tion in airspeed may be found by subtracting the change in
torque from the limit torque; then enter the cruise chart at
the reduced torque, and move up to the gross weight.
Move left or right to read TAS or IAS. To determine the air-
speed for maximum range for alternative wing stores con-
figuration, reduce the value from the cruise chart by 2
knots for each 5 square feet increase in drag area, DF, or
increase maximum range airspeed 2 knots for each 5
square feet reduction in drag area. For example, for 16
Hellfire configuration DF = 9.6 square feet, from figure
7-18. Therefore, maximum range airspeed would be re-
duced by 2/5 x 9.6 = 3.84 knots, or approximately 4 knots.
7.20.7 Additional Uses. The low-speed end of the
cruise chart (below 40 knots) is primarily to familiarize you
with the low-speed power requirements of the helicopter.
It shows the power margin available for climb or accelera-
tion during maneuvers, such as NOE flight. At zero air-
speed, the torque represents the torque required to hover
out of ground effect. In general, mission planning for low-
speed flight should be based on hover out of ground ef-
fect.
7.21 CONDITIONS.
The cruise charts are based on 100% rotor rpm, ATF or
ETF = 1.0, ENG INLET ANTI-ICE switch OFF, JP-4 fuel,
and dual-engine operation. Engine inlet anti-ice and rotor
blade de-ice effect are as follows:
a. With ENG INLET ANTI-ICE switch ON, fuel flow
will increase approximately 60 pounds per hour, maxi-
mum torque available could be reduced by as much as
16%, and maximum continuous torque available could be
reduced by as much as 17%.
b. With rotor BLADE de-ice switch ON, fuel flow will
increase approximately 30 pounds per hour, and torque
required will increase 1.4%.
For example, with ENG INLET ANTI-ICE and rotor
BLADE de-ice off, torque required, from cruise chart is
50%, and maximum continuous torque is 92%. With ENG
INLET ANTI-ICE and rotor BLADE de-ice ON, torque re-
quired will be 50 + 1.4 = 51.4%, and maximum continuous
torque will be approximately 92 – 17 = 75%.
