TM 1-1520-238-10
7A-13
Section IV.
HOVER LIMITS
7A.16. DESCRIPTION.
The hover chart (fig 7A-6) shows the torque required to
hover at various conditions of pressure altitude, free air
temperature, gross weight, wheel height, and with exter-
nal tanks or without external tanks.
7A.17. USE OF CHART.
The primary use of the chart is illustrated by the example.
To determine the torque required to hover, it is necessary
to know the pressure altitude, free air temperature, gross
weight, and desired wheel height. Enter the upper right
grid at the known pressure altitude, move right to the tem-
perature, move down to the gross weight, move left to the
desired wheel height, and then move up and read the
torque required to hover.
In addition to its primary use, the hover chart may be used
to predict the maximum hover height. To determine maxi-
mum hover height, it is necessary to know pressure alti-
tude, free air temperature, gross weight, and maximum
torque available. Enter the known pressure altitude, move
right to the temperature, move down to the gross weight,
then move left to intersection with maximum torque avail-
able and read wheel height. This wheel height is the maxi-
mum hover height.
The hover chart may also be used to determine the maxi-
mum gross weight for hover at a given wheel height, pres-
sure altitude, and temperature condition. Enter at the
known pressure altitude, move right to the temperature,
then draw a line down to the bottom of the lower grid. Now
enter upper left grid at maximum torque available, move
down to wheel height, and then move right to intersect the
previously drawn line and read gross weight. This is maxi-
mum gross weight at which the helicopter will hover.
7A.18. CONDITIONS.
The hover chart is based on calm wind, level surface,
100% rotor rpm and rotor BLADE de-ice switch off. With
rotor BLADE de-ice switch ON, torque required will in-
crease 1.4%.
