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E. Make a visual inspection of all slings. Look for worn or damaged areas. Install the slings carefully. Use pads or wood blocks for protection.
F. Make sure the lines that prevent movement are always tight. Be careful. Release the lines if it is necessary, while you lift the airplane.
G. Examine the scheduled procedure with all crane persons. Make sure all persons know the possible safety problems.
H. When the strength of the ground surface is not sufficient for movable cranes, prepare the area. You can prepare the area with better material (gravel fill), steel plates or wood. You can use one or all of these alternatives (see SUBJECT 2-10-4).
WARNING: SEE THE SPECIFICATIONS OF THE MANUFACTURER FOR THE CRANE BOOM LIMITS (DESIGN OR OPERATION). THESE LIMITS HELP YOU FIND THE CAPACITY OF A CRANE THAT IS NECESSARY.
I. Use cranes with a sufficient capacity. Do not operate the cranes at more than the specified loads. Know the relation between the specified loads and the boom angle. Use caution marks (warning indicators) if they are available. See Figure 3-56 thru Figure 3-58 for the values of a usual movable crane (75, 140 or 250 ton or 68, 127 or 227 metric ton capacity). The values are for the relation between specified loads and boom angles.
CAUTION: THE AIRPLANE SHOULD NEVER BE LIFTED ENTIRELY WITH ONLY TWO CRANES ATTACHED TO THE FUSELAGE.
J. Figure 3-51 shows an example of using a crane to lift the forward fuselage section of an airplane in which the nose landing gear has sustained damage and cannot support the weight of the airplane. A crane is used at the aft portion of the airplane to prevent damage to the fuselage in case of sudden aft C.G. movement.
3. Sling Installation, Forward Fuselage
A. Use a sling that has a width of 12 to 18 inches (31 to 46 cm). It must also have a maximum safe capacity of 15,000 pounds (6804 kg).
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WHEN YOU LIFT THE AIRPLANE WITH MOVABLE CRANES Page 3-97 Jul 01/2005
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B. Figure 3-59 shows a Fuselage Sling Assembly (Boeing PN F70244-17), which you can use on all 757 airplanes. The assembly has a polyester sling with a width of 12 inches (31 cm) and a spreader bar. You can use the sling without the spreader bar if you use two cranes.
C. You can assemble a sling that is the equivalent of the F70244 if the materials are available. Make sure that you use a safety allowance (safety factor of 5 to 1, ultimate load to maximum usual load) when you calculate the sling loads.
D. Put the sling at the body station 395. The maximum allowable load is 15,000 pounds (6804 KG) per frame if the lifting sling web center line is located within 2 inches (5 cm) of the frame center line.
E. You must use thick pads between the sling and the airplane skin. The pads give a more symmetrical load and decrease the possible damage from friction.
F. If you use only one crane, you must use a spreader bar (see Figure 3-60). Without the spreader bar, you will break (crush) the fuselage.
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