TB 9-2350-292-10
TOWING OPERATIONS ON GRADES
Towing a disabled vehicle is never easy, but towing up or
down a grade can be even more difficult and dangerous. While
towing a disabled vehicle, do not attempt to negotiate a grade
(either up or down) greater than 25 percent unless you have
the express permission of your commander.
NOTE: Under no conditions will you ever negotiate a
slope greater than 30 percent while towing a vehicle.
In order to know which grades to avoid, you have to know
how to classify them. Grades are defined in terms of percent, or
the amount of a grade's vertical height (rise) over its horizontal
length (run). If a road gains 25 feet of height over 100 feet of
length, it is classified as a 25 percent grade.
The best way to classify a grade is with a surveyor's level,
which will be BII on the Improved Recovery Vehicle, M88A2. The
operator stands at the top (or bottom) of the hill, and chooses a
point as close to the bottom (or top) of the hill, as possible where
he will be traveling. The operator then looks through the sight of the
level at the point he has chosen and turns the level knob until he
sees the level bubble centered between the witness marks. He
then just reads the percent grade off the indicator.
An expedient method uses a small level, a 10 inch piece of
flat wood and a ruler. Lay the piece of wood on the steepest part
of the grade, with the length of the wood running up and down
hill. Put the level on the piece of wood and start to raise the
downhill side of the wood up, until the bubble in the level is
between the witness marks.
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