TM 1-1520-240-10
7-4-1
SECTION IV. CONTINUOUS TORQUE AVAILABLE
7-4-1. Continuous Torque Available.
Continuous torque available may be obtained from figure
7-4-1. Available torque is presented in terms of PA and
FAT.
7-4-2. Use of Chart.
The primary use of the chart is to determine available
engine torque for various combinations of PA and temperature.
To determine torque available, it is necessary
to know PA and FAT. Enter the left side of the chart at
known temperature, move right to known pressure altitude,
then down to read torque available.
7-4-3. Conditions.
This chart is based on a rotor speed of 100%.
7-4-4. EAPS Installed.
Reduce the derived torque available by 1.8% however
not at transmission torque limit.
TM 1-1520-240-10
7-4-2
Figure 7-4-1. Continuous Torque Available
TM 1-1520-240-10
7-5-1
SECTION V. HOVER
7-5-1. Description.
The hover chart, figure 7-5-1, presents torque required
to hover at 100% RRPM at various combinations of PA,
FAT, GW, and wheel height for single and dual engine
operation.
7-5-2. Use of Chart.
a. The primary use of the charts is illustrated by the
example. To determine the torque required to hover, it is
necessary to know PA, FAT, GW, and desired wheel
height. Enter the upper right grid at the known pressure
altitude, move right to the temperature, move down to
gross weight. Move left to desired wheel height, deflect
down and read torque required for dual engine or single
engine operation.
b. n addition to the primary use, the hover ceiling
charts (fig. 7-5-2) may be used to predict maximum hover
height. This information is necessary for use of the
takeoff chart found in figure 7-6-1. To determine
maximum hover height, it is necessary to know PA, FAT,
GW, and maximum torque available. Enter at the known
pressure altitude, move right to FAT, move down to gross
weight, move left to intersection with maximum torque
available and read wheel height. This wheel height is the
maximum hover height.
c. The hover charts may also be used to determine
maximum GW for hover at a given wheel height, PA, and
temperature. Enter at known pressure altitude, move
right to the FAT, then move down to the bottom of the
lower grid, and read density altitude. Now enter lower left
grid at maximum torque available. Move up to wheel
height, then move right to density altitude and read GW.
This is the maximum gross weight at which the helicopter
will hover.
7-5-3. Conditions.
a. The hover chart is based on calm wind, level
surface, and 100% RRPM.
b. Hover in ground effect (HIGE) data is based on
hovering over a level surface. For normal transition from
hover to forward flight, the minimum hover wheel height
should be 10 feet to prevent ground contact. If helicopter
is to hover over a surface known to be steep, covered
with vegetation, or if type of terrain is unknown, the flight
should be planned for hover out of ground effect (HOGE)
capability.
c. EAPS installation has negligible effect on hover
torque figure 7-5-1.
d. Hover ceiling charts, figure 7-5-2, with EAPS
installed, reduce gross weight by 700 pounds.
TM 1-1520-240-10
7-5-2
Figure 7-5-1. Hover Chart
TM 1-1520-240-10
7-5-3/(7-5-4 blank)
Figure 7-5-2. Hover Ceiling
TM 1-1520-240-10
7-6-1
SECTION VI. TAKEOFF
7-6-1. Description.
The takeoff chart, figure 7-6-1, defines distances required
to clear obstacles of 50 feet, 100 feet, 150 feet,
and 200 feet based upon maximum hover height capability
and true airspeed. The procedure for takeoff is the
level flight acceleration technique.
NOTE
The maximum hover heights shown are indicative
of helicopter performance capability and do
not imply that this hover height must be maintained
through takeoff.
7-6-2. Use of Chart.
The primary use of the chart is illustrated by the examples.
a. To determine the distance required to clear an
obstacle, it is necessary to know maximum hover height
(hover capability), obstacle height, and climbout true
airspeed. Calculation of maximum hover height is
described in Section V, Hover. Enter the chart for the
required obstacle height, move right to desired true
climbout airspeed, then down and read distance required
to clear obstacle.
b. A hover check should be made prior to takeoff to
verify hover capability. If winds are present, hover
capability will be greater than predicted since the hover
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