Examine and lubricate all slings once a month in accordance with NAVAIR 17-1-114. When transporting slings, they will be carried at all times. Dragging slings over floors, runways, decks, and obstructions can cut or severely abrade the material. This malpractice results in an unserviceable sling. Whenever possible, slings should be stored indoors in a clean, dry, well-ventilated area so as to be protected from moisture, salt atmosphere, and acids of all types. In addition, slings constructed with nylon or other fabric materials will be stored in such a way as to prevent contact with sharp objects, high temperatures, and sunlight. Fabric materials deteriorate rapidly from prolonged exposure to sunlight or excessive heatseverely reducing strength and service life. Where practicable, slings will be securely fastened to overhead storage racks to prevent accidental damage. Avoid laying slings on ash or concrete floors. 

Hoisting Restrictions 

There are many restrictions to hoisting for each type of aircraft. Most hoisting restrictions are the same as for jacking aircraft. If you violate any of these restrictions, there is a good chance that you will have an accident, damage the aircraft, or injure someone. The restrictions generally concern aircraft gross weight and configuration. Some of the considerations are access (stress) panels on or off, external stores on or off, and wings, folded or spread. There are many factors that can affect the safety of the aircraft and personnel during hoisting operation. For details on restrictions and for the proper installation of any sling, consult the applicable MIM. Dont forget that many squadrons have their own local standing instructions for hoisting aircraft that contain additional safety precautions and restrictions. You must know them also. Prior to carrier operation, aircraft hoist points are inspected for serviceability and easy excess in an emergency. For details on how to accomplish this inspection on your aircraft, consult the applicable MIM.

AIRCRAFT JACKING 

Learning Objective: Recognize the procedures for the safe raising and lowering of aircraft by the proper use of aircraft jacks. Identify the various types of jacks presently found in the naval inventory. 

The following text will familiarize you with the various types of jacks, their use, and general safety procedures. You will become familiar with jack identification, preoperational inspections, and jacking procedures.

All aircraft hydraulic jacks are either axle or airframe (tripod) jacks. These jacks use standard, authorized aircraft hydraulic fluid. They have a safety bypass valve that prevents damage when a load in excess of 10 percent over the rated capacity is applied. For example, the safety valve on a 10-ton jack will bypass fluid at 11 tons of pressure.

Axle Jacks 

Use axle jacks for raising one main landing gear or nose gear of an aircraft for maintenance of tires,


Figure 3-27.Types of axle jacks.

wheels, and struts. There are four different types of axle jacks and many different sizes (lifting capacity in tons). Figure 3-27 shows the four types of Navy axle jacks. The smaller hydraulic axle jacks are normally squadron or unit permanent custody equipment. That means your outfit is responsible for making sure the jacks are load tested at the support equipment (SE) division of the aircraft intermediate maintenance department (AIMD) before being put into service, and annuall y thereafter. Special inspections include 13 week inspections at AIMD S/E, but a load test is not required every 13 weeks. A record of maintenance, inspections, technical directives, and load testing is kept on OPNAV form 4790/51

All model designations for axle jacks begin with the letter A, for axle, such as A 10-1HC. The number following the A shows the jack capacit y 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 that show the type of jack (HC = hand carried, HS = horseshoe, TB = T-bar, and OR = outrigger).

HAND CARRIED. These axle jacks are portable, self-contained units, with single or double manually operated pumps. They have carrying handles, pump handles, reservoir vent valves, release valves, and safety valves. The different model sizes vary from 4 3/4 inches to 9 inches high (closed). Their weights vary from 26 to 120 pounds.

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 cylinder.