TM 1-1520-238-10
7-9
Section III.
HOVER CEILING
7.13 DESCRIPTION.
The hover ceiling chart (fig 7-5) presents the maximum
gross weight for hover at various conditions of pressure
altitude, free air temperature, and wheel height, using
maximum torque available, 30 minute limit.
7.14 USE OF CHART.
The primary use of the chart is illustrated by the example.
To determine the maximum gross weight for hover, it is
necessary to know the pressure altitude, free air tempera-
ture, and desired wheel height. Enter the chart at the pres-
sure altitude, move right to FAT, move down to the desired
wheel height, and then move left and read maximum
gross weight.
7.15 CONDITIONS.
The hover ceiling chart is based on maximum torque
available, 30 minute limit, 100% rotor rpm, ATF = 1.0,
ENG INLET ANTI-ICE switch OFF and rotor BLADE de-
ice switch off. For ENG INLET ANTI-ICE switch ON, use
dashed lines. Applicable configuration is all external
stores except four external fuel tanks. For the four exter-
nal tank configuration, reduce the maximum gross weight
for hover, as calculated from the hover ceiling chart, by 11
pounds for each 1000 pounds of gross weight. See the ex-
amples below.
HOVER CEILING
EXAMPLE I
WANTED
MAXIMUM GROSS WEIGHT FOR HOVER AT 10-FOOT
WHEEL HEIGHT, ENGINE INLET ANTI-ICE OFF.
KNOWN
PRESSURE ALTITUDE = 10,000 FEET.
FAT = –10 C.
WHEEL HEIGHT = 10 FEET.
METHOD
ENTER PRESSURE ALTITUDE SCALE AT 10,000 FT.
MOVE RIGHT TO –10 C FAT, SOLID LINE.
MOVE DOWN TO 10 FEET WHEEL HEIGHT.
MOVE LEFT TO READ GROSS WEIGHT TO
HOVER = 16,400 POUNDS.
WITH 4 EXTERNAL TANKS INSTALLED
HOVER GW = 16,400–11 (16,400/1000)
= 16,220 POUNDS.
EXAMPLE II
WANTED
MAXIMUM GROSS WEIGHT FOR HOVER AT 10-FOOT
WHEEL HEIGHT, ENGINE INLET ANTI-ICE ON.
KNOWN
PRESSURE ALTITUDE = 10,000 FEET.
FAT = –10 C.
WHEEL HEIGHT = 10 FEET.
METHOD
ENTER PRESSURE ALTITUDE SCALE AT 10,000 FT.
MOVE RIGHT TO –10 C FAT, DASHED LINE.
MOVE DOWN TO 10 FEET WHEEL HEIGHT.
MOVE LEFT TO READ GROSS WEIGHT TO
HOVER = 15,200 POUNDS.
WITH 4 EXTERNAL TANKS INSTALLED
HOVER GW = 15,200–11 (15,200/1000)
= 15,033 POUNDS.
