Jacking Restrictions
Side loads normally result when the jacks are not
raised at the same rate. This causes the aircraft to tilt or
There are many restrictions to jacking for each type
pitch. When that happens, the distance between the
aircraft. If you violate any of these restrictions, there is
jacking points becomes closer in the ground
a good chance that you will have an accident, damage
plane--like the ends of a ruler will cover less distance
the aircraft, or injure someone. The restrictions
across a desk top as you raise one end. With the weight
generally concern aircraft gross weight and
of the aircraft holding the jacks in one place, that
configuration. Some of the considerations are fuel
"shrink" in distance between the jack points creates a
dispersion in fuselage and wing tanks, engines in or out,
tremendous side load on the jacks, and eventually they
and tail hook up or down.
will break or slip. The same thing happens if all the
jacks aren't lowered at the same rate to keep the aircraft
Details on restrictions and procedures are in the
level or at the same attitude it was in when jacking
MIMs, and you must know them and follow them
started.
exactly. If you don't, you will be in trouble. Don't forget
that many squadrons will have their own local standing
Lowering the jack can be very hazardous. The rate
instructions for jacking aircraft, which contain
of descent of a jack depends on how far the release
additional safety precautions and restrictions. You must
valve is opened. Control can be very tricky when you're
know these precautions and restrictions also.
trying to coordinate three jacks at once. Usually, it takes
only a small amount of rotation on the valve to get a fast
JACKING PROCEDURES
rate of descent. If you tightened the valve hard before
jacking, it will take force to open it. That extra force can
The jacking procedures vary for each aircraft type
cause you to open the valve more than you want, so be
and configuration. The procedures that follow are
very careful. The valves may vary in different jacks, so
examples of what you could encounter. Fairly exacting
get an idea of how your release valve reacts during the
steps are given to provide clarity. Remember, these
preop check. But remember it comes down a lot quicker
steps are from representative type aircraft, and are not
with a 30-ton load than with a 5-ton load.
necessarily accurate for all. When actually jacking
There is a safeguard to prevent you from lowering
aircraft, you must follow the exact procedures
the jack too fast--the safety locknut. The safety
described in the MIMs.
locknuts on jacks are a very important safeguard in
The location of the aircraft will determine what you
preventing the aircraft from falling off the jacks in the
need for equipment. Jacking procedures on a ship
event of jack failure. However, using them during
require tie-down procedures to prevent aircraft from
raising, and particularly during lowering operations, is
shifting on jacks. When tie-down chains are to be used,
hazardous to your hands and fingers. To be effective,
position them in accordance with the MIM, so as not to
the locknut must be kept about one-half thread above
interfere with the landing gear during the drop check of
the top surface of the jack (top of ram cylinder or
the gear. Jacking procedures on land do not require
second ram, depending upon the model jack). It is
tie-downs, except in high-wind conditions.
important to carefully keep your fingers and hands clear
of the area between the locknut and cylinder head so
Aboard ship, squadron maintenance controls will
they won't be pinched or crushed. This will be easier for
request, through the carrier air group (CAG),
you to do while you are raising the jack and rotating the
permission to place an aircraft on jacks. Check your
locknut down. Variable height jack rams have spiral
MIM for jacking restrictions, warnings, and cautions.
grooves, which allow the locknut to rotate down the
Obtain the support equipment required by the MIM,
ram by its own weight. However, this means that when
ensuring all preoperational inspections have been
you're lowering the jack, the locknut must be held up as
completed. Make sure that all protective covers and
you rotate it up the ram. This makes it more dangerous.
ground safety devices are installed, as required by the
Depending upon the height of the jack, it normally
MIM. The surrounding area around the aircraft must
takes two people to operate the jack and the safety nut.
be roped off during the entire aircraft jacking operation,
Do NOT try to do it by yourself.
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