FIXED HEIGHT JACK
VARIABLE HEIGHT JACK
Figure 3-28.Airframe (tripod) jacks.
HORSESHOE.Horseshoe axle or crocodile jacks
consist of a lifting arm supported by two hydraulic
cylinders. The cylinders move up over the stationary
pistons when the manual pump operates. The A25-1HS
is a large jack, 5 feet long, 5 feet 8 inches wide, standing
2 feet 1 3/4 inches high, and weighing 900 pounds.
T-BAR.The T-Bar or alligator axle jack is
mounted within a T-shaped frame. A manual pressure
pump and a speed pump mount on opposite sides of the
towbar end of the frame. The jack weighs 235 pounds
and is 4 feet 2 1/2 inches long, 2 feet 3 inches wide, and
10 inches high (closed).
OUTRIGGER.This cantilever axle jack is a very
large and heavy jack. It weighs 2,190 pounds and is
7 feet 3 inches long, 6 feet 8 inches wide, and 2 feet
3 inches high. A double (two-speed) pump mounts on
the left-hand side of the frame to operate the hydraulic
Airframe (Tripod) Jacks
Use airframe (tripod) jacks for lifting the entire
aircraft off the ground or deck. Airframe jacks are
commonly called tripod jacks. You may hear them
called wing, nose, fuselage, or tail jacks. These names
come from the jack placement on the aircraft. The points
for jacking vary with the type of aircraft, and can be
found in the MIM for each type of aircraft.
There are two different types of tripod jacks-fixed
height and variable height, Both are mobile,
self-contained, hydraulically operated units. They
consist of three basic assemblies. These assemblies are
the hydraulic cylinder, the tubular steel wheel tripod leg
structure, and the hydraulic pump. The main difference
between the two types is that the tripod structure on a
variable height jack can be adjusted to different height
by adding leg extensions.
All model designations for tripod jacks begin with
the letter T, for Tripod, such as T10-2FL or T20-1VH5.
The number following the T indicates the jack capacity
in tons, such as 10 for a 10-ton jack. This is followed by
a dash (-) and the specific jack identification number.
Then comes two letters indicating the type of tripod jack
(FH = fixed height, or VH = variable height). The
number that follows the VH for variable height jacks
indicates the number of leg extension kits available for
that jack. Figure 3-28 shows a T20-1VH5 jack with only
two of five extension leg kits installed. Each leg
extension kit increases the effective height of the basic
jack by 18 inches. The airframe tripod jacks weight
varies from 275 pounds to 837 pounds.