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1. General. The wing is of all metal construction consisting of a network of spars, ribs, and stringers which are covered with a thin highly stressed aluminum-alloy skin. (See figures 54, 55, and 56.) The wing has a multispar arrangement and consists of two sections which are jointed at the center line of the airplane. The wing tips are detachable. The skin gages vary from .020 inch to .084 inch, as shown on figures 54 and 55. The split trailing edge type flaps are of all metal construction, whereas the ailerons have a metal frame which is fabric covered. a. Types of Riveting. ~ Three types of riveting are used in the fabrication of the wing. These are: (1) Machine countersunk type where the upper sheet is machine countersunk. For repairs do not machine countersink below .051-inch sheet. (2) Press machine countersunk type which consists of machine countersinking the lower sheet or stringer and dimpling the upper sheet by squeezing or vibrating separately. (3) Press countersinking where both the upper and lower sheets or the stringer are dimpled separately. (4) In all cases, the parts are together when drilled for the rivets, and all rivets are driven by vibration. b. Types of Rivets. - All rivets exposed to the airstream are of the 78-degree countersunk, A17ST type (Curtiss Standard 673-D-AD) or of the 100-degree countersunk (Army Navy Standard AN426-AD). Internal rivets are of the modified brazier head A17ST type (Curtiss Standard 671-D-AD) or of the flathead type (AN442-AD). 2. Classification of Damage. When classifying any damage on the wing, carefully examine the extent and nature of the damage before placing it in one of the following: a. Negligible damage. b. Damage reparable by patching. c. Damage reparable by insertion. d. Damage necessitating replacement. |
3. Wing Skin. a. General. - The wing skin is supported by five spars, ribs between the spare, and closely spaced stringers which lie between the spars and are attached to the ribs. All areas of the skin are designed to take heavy tension and compression loads. It is essential, therefore, to adequately reinforce any area of the skin which becomes damaged. (1) Splice Plates. - Table I, figure 57, specifies the required numbers of rivets or bolts to be used at the in board and outboard edges of any patch or splice plate used to reinforce a damaged area. Columns 1, 2, and 3 specify the areas to which the data applies. Stations' are measured in inches outboard from the center line of the airplane as shown by the encircled numbers on figures 54 and 55. Column 4 gives the rivet dIameter, number of rows and the spacing between the rivets to be used at each end of a given patch; along the edges which are parallel to the ribs, The same data applies to the attachment on each side of a chordwise splice. The attachment for the edges of a patch which are parallel to the spars and for spanwise splices should be the same as in the nearest attachment of the damaged skin to a spar cap strip. When, as illustrated in figure 58, splices are made with frames which are discontinuous at the stringers or spars, the required number of rivets in board and out; board of the chordwise cuts should be determined from column 5 of table I on the basis of the over-all chord~ wise length of the skin cut. Arrange the rivets at the spacing given in column 4 adding an extra row on each side of the cut to take the extra rivets. Count only those rivets which attach the frame within the chordwise length of the cut. (2) Structural Doors. - Flush type structural or semistructural doors may be formed in the skin to facilitate skin repair* and permit future inspection of internal repairs. A structural door may be formed by substituting bolts for the rivets used ln attaching a skin insert to a frame or splice plates, (See figure 58.) Flush steel bolts No. 1101-D which fit countersunk holes are used. These screw into self-locking nut plates No. 659-D each of which is riveted to the underside of the frame with two AN-l26AD-4 flush type rivets. The bolt patterns to be used for the chordwise |
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