TM 1-1520-240-10
7A-5-1
SECTION V. HOVER
7A-5-1. Description.
The hover chart, figure 7A-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.
7A-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.
In addition to the primary use, the hover ceiling
charts (fig. 7A-5-2) may be used to predict maximum
hover height. This information is necessary for use of the
takeoff chart found in figure 7A-6-1. To determine maxi-
mum hover height, it is necessary to know PA, FAT, GW,
and maximum torque available. Enter at the known pres-
sure 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.
7A-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.
