Service and Repair Manual

thus loosening the rivets and making them ineffective. All bolt and rivet patterns should be arranged to make use of the original holes. Do not drill additional hole or change the pattern unless the change is justified by a similar change in board of the section in question.

     (3) Cap Strip Patches. - Due to the fact that reinforcements bolted to a cap strip cannot be made as efficient as the original continuous material any partially damaged section will take its ultimate allowable load before the reinforcements or patches are loaded up. This action will inevitably cause complete failure of the cap strip at the damaged section during service. To avoid a failure of this nature, all cap strip patches and their attachments at each end of the damage, must, therefore,be made equal in strength to the strength of the original undamaged section. The repairs given in figures 70 to 73 are designed to include the strength of the web material that acts with the cap strips.

     d. Damage Reparable by Insertion. - Extensive damage or damage which due to its location cannot be repaired by patching should be repaired by the use of an insert. Details for the splicing in of cap strip inserts are given in figures 70 to 73.

     e. Damage Requiring Replacement. - All damaged cap strip reinforcements should be replaced.

     8.Flap.

     a. General. - The skeleton aluminum-alloy framework of the split trailing edge flaps ts covered with .025-inch aluminum-alloy MST sheet. (See figure 93.)

     b. Skin.- Any damage to the skin should be repaired with a flush insert of .025-inch gage 24ST stock attached by a patch or frame of .032-inch gage MST stock. Use a single row of AN426AD-4 press counter inch s c for the attachment sunk rivets at - pa ing . Patches and frames may be discontinuous at the ribs or beam.

     c. Rib -Random holes in the web of any rib which when cleaned up can be circumscribed by a circle of diameter less than one-half of the depth of the rib at the damaged section may be considered negligible providing:

     (1) The center of the hole is not above the center of the rib web.

     (2) The lower edge of the hole does run into the lower bend radius.

     (3) The edge of the hole is not closer than 1 inch in a chord wise direction, to the nearest structural hole.

     For damage in excess of the above see figure 94.

d. Stringer. - Any damage to the stringers should be reinforced by adding a .040-inch gage 24ST "Z" section as shown in figure 95. This same reinforcement may be used as a splice when replacing sections of a damaged stringer.

     e. Channel Beam. - The channel forming the main beam of the flap is heavily loaded and has low margins at the sections where the operating links are attached as well as at the ribs. All repairs are to be made with .051-inch gage MST stock fitted to the channel as shown in figure 96 and the specified arrangement of ANMZAD-4 rivets. For minor damages to the beam use portions of the reinforcement illustrated ln figure 96 as follows:

     (1) Damage to the Flange Only. - Attach an angle with three rivets ln the flange and three an the leg of the channel at each end of the damage.

     (2) Damage to the Leg Only. - Attach a "Z" section with three rivets in the flange of the channel, six rivets ln the leg and three rivets in the back of the channel at each end of the damage.

     (3) Damage to the Back of the Channel Only. - Attach a channel with seven rivets through the back and three through each of the legs of the channel at each end of the damage.

     For extensive damage or damage occurring in the sections which cover hearing blocks for the operative links insert new sections of channel making the splices (figure 96) between ribs in the sections where there are no bearing blocks. Replace all damaged fittings, etc.

     f Hinge. - Minor local damage to the flap hinge between the ribs may be cleaned up and neglected, Damage with in 2 inches of any rib should be repaired by cutting away the damaged portion of the hinge and replacing it with a new section of standard hinge. Arrange the new insert so that its ends are at least 2 inches from the nearest flap rib.

     9.Ailerons.

     a. General. - The ailerons are light alloy, fabric covered structures. (See figure 97.) To prevent their flutter at high speeds the static balance of each about its hinge axis is adjusted in manufacture by attaching a lead filled tube with in the leading edge near the outboard end. Any repair which decreases the static balance; that is, makes the trailing edge fall by more than 0.3 inch-pounds measured at the hinge axis should be compensated for by adding lead sheet to the leading edge directly in front of the repair. Use 1/8-inch or thinner, lead sheet extending to within 1 inch of the upper and lower row of rivets in the nose beam flanges and attach with 1/8-inch counter sunk blind rivets at 1-inch spacing and 1/2-inch edge distance along the top and bottom edges. (See figure 114.) Cover the lead with well doped fabric extending at least 3 inches beyond its edges.