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, you’re 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. Don’t 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 don’t have towbars, the wheels can’t be locked in position so they track, and there are no brakes. Don’t 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 isn’t 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. General Hazards 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 screw–which isn’t 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 plane–like 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 aren’t 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 you’re 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 you’re 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. Don’t try to do it by yourself. 3-41