(3)
The wing rear spars are the only available structures that can hold the jack load and correctly balance the airplane. Use a beam as shown in Figure 3-41 with two jacks below the rear spar of the wing. Do this on each side of the fuselage. This will hold the airplane while you remove the load from the main jack points.
(4)
Use padding between the beam and the wing to prevent local damage to the structure. Make sure that each beam is below the spar and not below a skin area that has no support.
(5)
Install load gages on each jack in the rear spar configurations. Monitor these gages while you apply the jack loads. A serviceable wing structure is flexible and you can apply slow and continuous loads. The inboard wing areas are less flexible than the outboard areas. Thus, a different jack extension is necessary at the outboard jack.
(6)
Do not lift the airplane with the rear spar configuration higher than it is necessary. Stop when you release the load on the primary wing jacks. If it is necessary, adjust the nose jack and the tail jack to keep a level airplane attitude. A level attitude keeps the jack loads to a minimum.
(7)
When the airplane is at a correct height, install more supports (cribbing) in the areas near the wing jack points. Then compress the axle jacks to their minimum height.
(8)
Use support tools (cradles) below the primary bulkheads or cargo doors. Put more support (cribbing) below the fuselage each time you put new supports (cribbing) below the body jacks. Adjust the vertical position of each body jack if it is necessary. Make sure you keep the airplane at a level attitude (see Figure 3-44 for jacking and contour shoring example).
(9)
After you add new supports (cribbing) below the jacks, you can use them to lift the airplane one more increment. Keep all stabilizer jacks at their specified (nominal) loads. Keep the airplane at a level attitude.
(10)
Continue these increments until you have a sufficient height to install the usual tripod jacks at the main jack points.
(11)
Use the main jacks to lift the airplane to the height that is necessary to do the recovery operation. Then extend the folded gear or replace it. Also, make sure that you lock the gear. Possibly, you must put a truck (flat bed) below the airplane to move it. See Section 4-00 for more data on the movement of the airplane.
3-30-5
IMPORTANT DATA ABOUT THE JACKS
Page 3-67 Jul 01/2005 D623N004
NOTE: EXTEND THE GEAR SLOWLY BECAUSE THE GROUND BELOW THE GEAR IS POSSIBLY NOT STABLE, OR THE LANDING GEAR IS DAMAGED. USE JACKS, OR CABLES OR USE A TRUCK (FORKLIFT) TO PREVENT A FAST MOVEMENT OF THE GEAR. LOCK THE EXTENDED GEAR. THEN DECREASE THE AIRPLANE HEIGHT UNTIL THE GEAR STARTS TO HOLD THE AIRPLANE. REMOVE THE MAIN WING JACKS QUICKLY WHEN THE AIRPLANE WEIGHT IS ALL ON THE LANDING GEAR. THIS PREVENTS DAMAGE TO THE AIRPLANE IF THE GEAR MOVES DOWN INTO SOFT GROUND. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：757 Airplane Recovery Document 飞机恢复文件(80)
