|
tertal along every cross section of the rib by more than 10 percent and which are not within half an inch of any web hole flange, structural bead, or fltttng attachment may in general be considered negllglble. Small, isolated dents which are at least half an Inch from the nearest web hole flange or structural bead may be neglected. Sharp cornered holes should be rounded out and all dents should be`bumped out and examined for cracks. All cracks should be stopped by drilling 1/8-inch holes at their ends. Do not neglect any cracks, nicks, or holes tn the landing gear attachment ribs or in the leading and tralllng edge portions of the center line rib. b. Damage Regrable by Patching. (1) Minor Damgge. - Minor damage not considered negligible may in general be cleaned up and patched with 2431* stockof the same gage. (Refer toflgures 80 to 64.) In all areas except those directly above or below a lightening hole, use the same rivets or bolts and the same spacing as in the nearest attachment of the rfb to the spar web, and run this pattern either completely around the damage or to the edges of the undamaged portion of the rib. In patching damaged areas above or below a lightening hole use the same gage patch with twice as many rows of the same rlvets or bolts and the same spacing as_tn the nearest web attachment. (2) Llghtentng Hole Flange. - If the damage after clean-up fs fn the flange of a llghtenlng hole or within half an inch of this flange, form a flange on the patch equal tothe lightening hole flangeand add anaddlttonal rivet at each end of the patch flange near the undamaged rfb hole flange. (See figure 65.) (3) Structural Beads. - If the damage is within half an tnchof a structural bead or extends across the bead, form an equal bead in the patch and add two additional rlvets each slde of the damage, one each side of the bead. (4) Landing Gear Ribs. - The landing gear ribs should not be patched unless the rivets or bolts used for the patch, see nearest attachment of rib to spar web, can be placed around the damage without their being closer than 1 lnch to the nearest fitting attachments. If a landing gear rib or any of its fittings are ln any way damaged, inspect the whole landing gear attachment structure for damage to the attachments, cracks ln the fittings, and misalignment of parts. 5. Dagage Regable by Insertion. - Damage to areas supporting fittings, to areas around which sufficient attachment cannot be obtained for patches, and to areas extensively damaged should be repaired by the use of inserts of the same gage 24ST stock. The design requirements for splice plates and their at-tachments or for overlap spllces are the same as for patch plates, as given ln this section, paragraphs 4.b.,(1) to 4.b.(4). Equal legged angles of the same gage 24ST stock 5/8 inch x 5/8 inch may be attached to an insert along the line of an original bead in lieu of forming a bead. The same angle should be used as a vertical stiffener across a space where it is undesirable |
to reform a flanged lightening hole. (See figures 81 and 66.) Attach the angle with the same rivets and pattern used for the splices. d. Damage Necessitating Replacement. - Damaged rib reinforcements and fittings and extensively damaged rib sections should be replaced. Use care in drilling out the existing rivets. (Refer to section I, paragraph 8.) 5. Spars. a. Negligible Damage. - Small holes in the spar webs which can be circumscribed by a 3/4-inch diameter circumscribed not be patched provided the perifery of the circle is not less than 1 inch from the nearest lightening hole or cap strip. The hole should be drilled or reamed to make the edges smooth. b. Damage Reparable by Patching. (1) Minor Damage. - Minor damage not considered negligible should be cleaned up and patched provided there ls sufficient room to use the required rivet pattern as given to tables A and D of figure 67 around the damage. Patches should be made from the same gage 2482! stock as the damaged spar web. The spar web gages are as follows:
(2) Web Lightening Hole. - When damage is near a web lightening hole, as in figures 57 and 59, extend the patch beyond the edge of the hole,run the required rivet pattern around the damage of the edge of the hole, and add an extra rivet at each end of the pattern near the edge of the hole. If the web hole is flanged, add an equal flange to the patch and add two extra rivets at the ends of the rivet pattern near the flanges. The flange on the patch may be formed straight and should be opposite to the web hole flange. Damaged lightening hole reinforcement rings must be replaced. Large reinforcement plates may be patched with 24STstock of the same gage as the original member, using the same method as employed for web repair. Where both web and reinforcement are damaged, place the required patches on opposite sides and rivet through the four sheets with the required rivets and pattern. Use a filler between the patches and replace all rivets which were originally ln the damaged area. (See figures 60 and 61.) A single patch equal in gage to the web plus its reinforcement as in figure B8 may be used, providing the next larger size of rivets is used |
