Chapter 1. INTRODUCTION - TM-55-1730-208-130004

TM 55-1730-208-13

CHAPTER 1

INTRODUCTION

Section I. GENERAL INFORMATION

1-1. Scope.

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.

used.

Chapters 1 through 3 of this technical manual contain

instructions required for operation, preventative

1-3. Reporting of Improvements.

maintenance

services,

troubleshooting,

and

maintenance as prescribed by the maintenance

Report of errors, omissions and recommendations for

allocation chart.

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

maintenance level.

Section II. DESCRIPTION AND LEADING PARTICULARS

assembly and supplies hydraulic fluid under pressure

1-4. Description.

(2235 psi) through a hose assembly into the cylinder and

ram assembly.

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

cylinder.

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

through 1-10.

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

assemblies.

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

1-1