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1. Mass Balancing. The elevator and rudder are aluminum-alloy, fabric-covered structures. The static balance of each about its hinge line is adjusted in manufacture by the addition of lead weights near the leading edge. The weights added in each case are the minimum that will give satisfactory flutter control. It is important, therefore, in effecting repairs aft of the hinge line, to compensate for any addition of weight. This may be easily accomplished as follows: Set the surface on its hinge bearings. Attach a sufficient length of cord to the trailing edge of the surface so that it may extend along the top part of the surface, and over the leading edge. Attach weights to the free end of the cord until the top surface assumes a horizontal position. Remove the cord and make the necessary repairs. When the repairs are complete replace the cord and weight in the same position as the original prebalanced attachment. Add sufficient lead sheet to the leading edge to return the surface to its horizontal prebalanced position. Attach the lead sheet and cover with fabric as described in section VI, paragraph 9.a. (See figure 98.) 2. Elevator. a. General. - The elevator contains one counter weight which is installed inside of the paddle at the outboard end, forward of the center line of the hinge. This counterweight is a 2-inch OD x .058-inch x 5-1/8 inch tube filled with 3.607 pounds of lead. It is welded to webs which are riveted to the ribs. (See figure 113.) This weight is not accessible. b. Negligible Damage. - One inch holes at the center of the rib webs which are at least 1/2 inch from any other holes or the flanges may be neglected if there are no cracks. c Main Beam. (1) Flanges. - Repair flange damage, when injury does not extend more than 1 inch into the web, by Patching with 5/8-inch x 1-inch x .032-inch 24ST aluminum-alloy angle long enough to take two AN442AD-4 rivets in the beam web plus two of the skin rivets at each end of the damage as shown in figure 108, or use a repair similar to that shown in figure 100 with the .032-inch angle long enough to take four AN442AD-4 rivets through the beam flange plus at least two 1/8 inch Cherry blind rivets through the beam web near the flange at each end of the damage. (2) Webs. - Damage that is confined to the web of the beam should be patched with .032-inch 24ST aluminum-alloy sheet attached with one row of 5/32 inch Cherry blind rivets at 3/4- inch spacing around the damage. If accessible use AN442AD-4 rivets at 3/4-inch spacing. |
(3) Webs and Flanges. - For complete cross section damage, patch the member with an equivalent section as shown in figure 109. Use the next heavier gage if lightening holes or beads are damaged. If the section is inaccessible for riveting the web of the beam use four AN442AD-4 rivets in each flange on each side of the cut plus four 1/8-inch Cherry blind rivets, two near each flange in the web, on each side of the cut similar to repair illustrated in figure 100. d. Nose Skin. - Repair is the same as for the aileron, use an external patch extending to the nearest ribs and to the edges of the nose skin. (See figure 99.) e. Trailing Edge. - Repair as illustrated in figure 102. Torgue Tube. - Replace the entire damaged section of the tube. g. Ribs. (1) Webs. - Rib web damage may be repaired by patching with 24ST stock of the same gage as the original material. Attach the stock with one row of AN442AD -4 rivets at 3/4-inch spacing around the damage. (2) Flanges. - Flange damage repairs should be effected by replacing the area and using three AN442AD-4 rivets in the web near the flange at each end of the damage to attach the patch piece in place as illustrated in figure 108. (3) Extrusions. - Any damage to the extrusion, (figure 114) by which the fabric is attached, should be repaired by inserting a new section long enough to take at least two 1/8-inch rivets at a 1-inch minimum spacing. Splice with a .032-inch x 1/2-inch 24ST plate long enough to take two 1/8-inch rivets on each side of each cut. (4) Special Rib Flanges. - Rib flanges that attach the ribs to the beam web if damaged should be replaced by a 5/ B-Inch x 5/ 8-inch angle of the same gage material. The angle should be attached to the rib by the same number of rivets as used to attach the rib to the beam web. (See figure 1l3.) 3. Rudder. a. General. - The rudder contains two counterweights inside of the leading edge. One, made of steel bar, is welded to plates which are in turn bolted to the first and second ribs above the intermediate center |
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