HEADQUARTERS OH-58A, Technical Manual

Page: 208 / 292

TM 55-1520-228-10
SECTION XI. HOVER
7-41. DESCRIPTION.
The hover charts (figure 7-13, sheets 1 and 2) show the
hover ceiling and the torque required to hover
respectively at various pressure altitudes, ambient
temperatures, gross weights, and skid heights.
Maximum skid height for hover can also be obtained by
using the torque available from figure 7-11.
7-42. USE OF CHART.
a. The primary use of the charts is illustrated by the
charts examples. In general, to determine to hover
ceiling or the torque required to hover, it is necessary to
know the pressure altitude, temperature, gross weight
and the desired skid height.
CAUTION
Low altitude maneuvering flights at
airspeeds below 35 knots are not
recommended under conditions
where power required to hover out of
ground effect exceeds maximum
continuous power.
b. in addition to its primary use, the hover chart
(sheet 2) can also be used to determine the predicted
maximum hover height, which is needed for use of the
takeoff chart (figure 7-14) ; and the maximum right
crosswind corresponding to a 10% directional control
margin. To determine maximum right crosswind and
hover height proceed as follows:
(1) Enter chart at appropriate pressure
altitude.
(2) Move right to FAT.
(3) Move down to gross weight, read the
maximum right crosswind corresponding to a 10%
directional control margin.
(4) Move left to intersection with maximum
power available (obtained from figure 7-11).
(5) Read the predicted maximum skid height.
This height is the maximum hover height.
7-43. CONDITIONS.
The hover charts are based upon calm wind conditions,
a level ground surface, and the use of 100% N2 rpm.
Controllability during downwind hovering, crosswinds,
sideward flight and rearward flight may be inadequate;
however, for stabilized hover in steady winds from the
right (i.e., right crosswind) the wind velocities on the
chart correspond to the maximum one can have and yet
maintain a 10% directional control margin. See Chapter
5 for hovering and low altitude/low airspeed flight
limitations.
WARNING
Figure 7-13 (sheet 3 of 3) shows 10%
directional control margins only for
the stabilized conditions set forth. It
does not and is not meant to infer
that for corresponding dynamic flight
maneuvering conditions such
margins exist
7-56 Change 10