The same basic safety precautions apply to all jacks. Conduct a good preoperational inspection before you use it. NAVAIR 19-600-135-6-1 is the general preop maintenance requirements card (MRC) for all jacks. Make sure that the jack has been load tested within the last 13 weeks. Next, if the jack is dirty, take the time to wipe it down. You can t see cracks or broken welds under dirt. If the jack is covered with hydraulic fluid, you can suspect it may be leaking. Inspect it more closely.

Check the reservoir; it should be full with the jack ram fully collapsed. If the reservoir is low, you can suspect a leak somewhere. Fill the reservoir with clean, fresh, hydraulic fluid. Check the filler plug vent valve to make sure it is not clogged. If the plug is blocked, you may get an air lock, and the jack may not operate correctly. You could also get a pressure buildup in the reservoir and a possible rupture. Check the pump handle for bends and the pump rocker arm and link for elongated or out-of-round holes. These are signs that the jack may have been overloaded, and that the safety bypass valve is malfunctioning.

With the filler plug air vent valve open and the release valve closed, pump up the ram and check for leaks and full extension. When the ram reaches full extension, you will feel the pumping pressure increase. Dont continue to pump or you may damage the internal ram stops because there is no load on the jack. Lower the ram and screw out the extension screw, but dont forcibly overextend it past the internal stops. Check to see that it is clean and oiled. If it is dirty, wipe it clean and coat it with a light film of MIL-L-7870 oil. On jacks equipped with wheels, check the wheels and springs suspension assemblies to make sure theyre in good condition. Towing or dragging these jacks around with broken wheels will damage the frame or reservoir.

Since many leaks in jacks will only appear when the jack is under a load, be sure to watch for leaks when you are jacking the aircraft. If you find a leak, or other defects, during the preoperational inspection, do not continue to use the jack Down or red line it, tag it as bad, report it, and turn it into the SE division (AIMD) for repairs. Dont leave a defective jack where someone else may use it.

Handling airframe jacks can be hazardous. The jacks are heavyanywhere from 110 to 900 pounds-and the wheels are free-swiveling and small. Directional stability is poor, and pushing one into position around an aircraft is no simple chore. Trying to move or position a tripod jack by yourself is hazardous. If the jack is dirty and covered with grease or fluid, its even more hazardous. The jack footplates and wheels at the base of the tripod stick out, and are notorious "foot-crunchers" and "shin-knockers." Its not hard to damage an aircraft tire, wheel brake assembly, hydraulic lines, landing gear door, or any other pact of an aircraft if youre not careful and ram it with a jack.

Movement of jacks aboard ship when there is any pitch or roll of the deck is extremely hazardous. Even with a calm sea, a smart turn into the wind by the ship while youre moving an airframe jack can be disastrous. Movement of jacks from hangar to hangar, through hangar bays, and across hangar tracks and ramp seams can easily damage a jack and put it out of commissionjust when you need it!

Transportation of jacks over longer distances ashore, such as from the SE pool to a hangar on the other side of the field, can be a real problem. If your SE division (AIMD) has locally fabricated a special "jack transporter" trailer, youre in luck. If any other type trailer, truck, or flatbed is used, you must have sufficient manpower available to safely get the jacks on and off the vehicle. Jacks are heavy and cumbersome to handle. Loading and unloading is hazardous even when you have enough people. Usually, a locally fabricated sling and some sort of hoist is necessary. Forklifts should never be used to handle or lift jacks. The tripod cross braces are not strong enough, and you will damage the jack. The chances of dropping it are also high. Dont use forklifts to handle jacks.

The wheels on a tripod jack are not made for towing the jack. They are small, allow only a couple of inches of clearance, and are spring loaded. Bouncing over uneven surfaces will usually cause the jack footplates to hit the ground, and that can spin the jack around, tip it over, or damage the tripod structure. Airframe jacks dont have towbars, the wheels cant be locked in position so they track, and there are no brakes. Dont try to tow airframe jacks.

Free swiveling casters and no brakes also mean that jacks can move by themselves if not properly secured. A loose, 900-pound tripod jack on a pitching hangar deck could be disastrous. Jacks can also be moved by jet or prop blast. Therefore, any jack that isnt tied down can be a hazard. Since there are no tiedown rings on the jacks, you must take care as to how you attach the tiedown chains or ropes to prevent damage to the jack. This is particularly true aboard ship where the jacks are likely to be "working" against the tiedowns in rough seas.

The extension screws on jacks have a maximum extension range. This range is stenciled on the jack. An internal stop prevents overextending the screw. If you forcibly overextend the screwwhich isnt hard to do-you not only damage the internal stop mechanism, but also make the jack unsafe and hazardous to use. An overextended screw is very likely to bend or break off from any side motion.

The extension screw on a jack is equipped with a jack pad socket. The aircraft jack pad fits into this socket and into a fitting or socket in the aircraft. The sockets and pads are designed to take vertical loads but not much horizontal pressure. The pads can shear or slip from either the jack or aircraft socket if enough side load is applied.

Side loads normally result when the jacks are not raised at the same rate. This causes the aircraft to tilt or pitch. When that happens, the distance between the jacking points becomes closer in the ground planelike the ends of a ruler will cover less distance across a desk top as you raise one end. With the weight of the aircraft holding the jacks in one place, that "shrink" in distance between the jack points creates a tremendous side load on the jacks and eventually they will break or slip. The same thing happens if all the jacks arent lowered at the same rate to keep the aircraft level or at the same attitude it was in when jacking started.

Lowering the jack can be very hazardous. The rate of descent of a jack depends on how far the release valve is opened. Control can be very tricky when youre trying to coordinate three jacks at once. Usually, it takes only a small amount of rotation on the valve to get a fast rate of descent. If you tightened the valve hard before jacking, it will take force to open it. That extra force can cause you to open the valve more than you want, so be very careful. The valves may vary in different jacks, so get an idea of how your release valve reacts during the preop check. But remember, it comes down a lot quicker with a 30-ton load than with a 5-ton load. 

There is a safeguard to prevent you from lowering the jack too fast-the safety locknut. The safety locknuts on jacks are a very important safeguard in preventing the aircraft from falling off the jacks in the event of jack failure. However, using them during raising, and particularly during lowering operations, is hazardous to your hands and fingers. To be effective, the locknut must be kept about one-half thread above the top surface of the jack (top of ram cylinder or second ram, depending upon the model jack). It is important to carefully keep your fingers and hands clear of the area between the locknut and cylinder head so they won t be pinched or crushed. This will be easier for you to do while you are raising the jack and rotating the locknut down. Variable height jack rams have spiral grooves, which allow the locknut to rotate down the ram by its own weight. However, this means that when youre lowering the jack, the locknut must be held up as you rotate it up the ram. This makes it more dangerous. Depending upon the height of the jack, it normally takes two people to operate the jack and the safety nut. Dont try to do it by yourself.