Section I. GENERAL INFORMATION
1-2. Equipment Records.
This technical manual comprises instructions
required by operator's, organizational, and direct
support maintenance personnel responsible for the
The Army Maintenance Management System in TM 38-
operation and maintenance of the hydraulic jack, part
750 applies to this equipment.
number 50J25178 (type B6), (see figure 1-1),
The applicable forms as required by TM 38-750 shall be
manufactured by the Department of the Air Force.
Chapters 1 through 3 of this technical manual contain
instructions required for operation, preventative
1-3. Reporting of Improvements.
maintenance as prescribed by the maintenance
Report of errors, omissions and recommendations for
improving this publication is encouraged. Use DA Form
Appendix A, References, contains a standard list of all
2028 (Recommended Changes to DA Publications) and
publications applicable to this manual and available to
forward directly to the Commanding General, U. S.
operators and maintenance personnel.
Army Aviation Systems Command, ATTN: AMSAV-R-
Appendix B contains the maintenance allocation chart.
M, P. O.
This chart assigns maintenance functions and repair
Box 209, St. Louis, Missouri 63166.
operations to be performed by the applicable
Section II. DESCRIPTION AND LEADING PARTICULARS
assembly and supplies hydraulic fluid under pressure
(2235 psi) through a hose assembly into the cylinder and
The hydraulic jack, part no. 50J25178 (type B6),
The hydraulic pump is manually operated by a pump
is a hand-operated, hydraulic, folding tripod jack, used
handle which moves a pump piston inside a pump
as an aircraft jack. The purpose of the hydraulic jack is
When the pump piston is pulled down,
to provide up to 10 tons of lifting effort through a range
hydraulic fluid from the reservoir is drawn into the pump
of 36 inches fully collapsed, to approximately 152 inches
cylinder by unseating the intake valve ball. When the
fully extended. Descriptions of the major components of
pump piston is pushed up, the intake valve ball seats,
the hydraulic jack are provided in paragraphs 1-5
and the discharge valve ball unseats. Fluid under
pressure is then supplied to the cylinder and ram
assembly which, in turn, moves upward providing the
1-5. Clamp Assembly.
required lifting force.
Additional parts of the hydraulic pump assembly and
The clamp assembly is used in mounting the hydraulic
their functions are defined in the following paragraphs.
pump assembly to a leg or leg extension of the hydraulic
jack. A clamp cam handle is provided which locks into
the upper end of the pump assembly. The lower end of
a. Vent Assembly. The vent is located near the
the pump assembly mounts on one of the foot
top edge of the reservoir. The vent assembly prevents
a vacuum inside the reservoir during raising operations
and allows air to escape during lowering operations.
1-6. Pump Assembly.
b. Safety Relief Valve (No. 1). The safety relief
valve is self-contained and is located in the submerged
The pump assembly consists of a hydraulic reservoir
end of the pump. It is provided to bypass hydraulic fluid
and a hydraulic pump. The reservoir provides a storage
into the reservoir when the 20,000-pound capacity limit
place for hydraulic fluid required during jack operation
is exceeded during raising operations.
and also provides mounting points for the pump
assembly. The pump forms the lower end of the pump