TM 1-1520-238-10
7A-10
Section III.
HOVER CEILING
7A.13. DESCRIPTION.
The hover ceiling charts (fig 7A-5 sheets 1 and 2) pres-
ents the maximum gross weight for hovering at various
conditions of pressure altitude, free air temperature, and
wheel height, using maximum torque available, 30 minute
limit or maximum torque available, 10 minute limit.
7A.14. USE OF CHARTS.
The primary use of the hover ceiling charts is illustrated by
the examples. To determine the maximum gross weight
for hover, it is necessary to know the pressure altitude,
free air temperature, and desired wheel height. Enter the
appropriate power available chart at the pressure altitude,
move right to FAT, move down to the desired wheel height
and then move left and read maximum gross weight.
7A.15. CONDITIONS.
The hover ceiling charts are based on maximum torque
available, 30 minute limit and 10 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 external tank configuration, reduce the maximum
gross weight for hover, as calculated from the hover ceil-
ing charts, by 11 pounds for each 1000 pounds of gross
weight. See the examples below.
HOVER CEILING
EXAMPLE I
(SHEET 1)
WANTED
MAXIMUM GROSS WEIGHT FOR HOVER AT 10-FOOT
WHEEL HEIGHT, 30-MINUTE LIMIT TORQUE
AVAILABLE, FOR ENGINE INLET ANTI-ICE OFF AND
ON
KNOWN
PRESSURE ALTITUDE = 10,000 FEET
FAT = –10C
WHEEL HEIGHT = 10 FEET
METHOD
ENTER PRESSURE ALTITUDE SCALE AT 10,000 FT
MOVE RIGHT TO –10C FAT, SOLID LINE FOR
ANTI-ICE OFF, DASHED LINE FOR ANTI-ICE ON
MOVE DOWN TO 10 FEET WHEEL HEIGHT
MOVE LEFT TO READ GROSS WEIGHT FOR HOVER:
ANTI-ICE OFF, HOVER GW = 17,520 LB
ANTI-ICE ON, HOVER GW = 15,850 LB
WITH 4 EXT TANKS INSTALLED
ANTI-ICE OFF
HOVER GW = 17,520–11 (17,520/1000)
= 17,327 LB
EXAMPLE II
(SHEET 2)
WANTED
MAXIMUM GROSS WEIGHT FOR HOVER AT 10-FOOT
WHEEL HEIGHT, 10-MINUTE LIMIT TORQUE
AVAILABLE, FOR ENGINE INLET ANTI-ICE OFF AND
ON
KNOWN
PRESSURE ALTITUDE = 10,000 FEET
FAT = –10C
WHEEL HEIGHT = 10 FEET
METHOD
ENTER PRESSURE ALTITUDE SCALE AT 10,000 FT
MOVE RIGHT TO –10C FAT, SOLID LINE FOR
ANTI-ICE OFF, DASHED LINE FOR ANTI-ICE ON
MOVE DOWN TO 10 FEET WHEEL HEIGHT
MOVE LEFT TO READ GROSS WEIGHT FOR HOVER:
ANTI-ICE OFF, HOVER GW = 18,000 LB
ANTI-ICE ON, HOVER GW = 16,400 LB
WITH 4 EXTERNAL TANKS INSTALLED
ANTI-ICE OFF
HOVER GW = 18,000–11 (18,000/1000)
= 17,802 LB
