What do I have to do to replace the flap outboard up-stop bolts (flap stop bolts, flap adjustment bolts, outboard flap bolts)? What do I do if the bolt just spins in its mount, when I try to remove it?
Technical Editor:
Sure sounds familiar. Do NOT reinstall another Riv-Nut, unless you enjoy that kind of torture. In order to work properly, and then only under light loadings, Riv-Nut installation has several requirements. They have to be genuine BF Goodrich Riv-Nuts, not the cheaper clones (Nut-serts, etc.). They must have the tiny key under the head, which (barely) helps keep the Riv-Nut from spinning in its hole. They must have a keyway cut in the side of the hole for the key. A special cutter is required for this, though a tiny needle file can suffice. The surface of the metal base under the head of the Riv-Nut must be undamaged; flat and square. Otherwise the key won’t engage the keyway. The Riv-Nut must be properly set with the correct tool; too loose and it won’t fully set the key into the keyway; too tight and the threads will pull out. The part being retained must be pulled down snugly against the Riv-Nut’s head when the fastener is tightened; any gap will cause the Riv-Nut to loosen. And with a Riv-Nut there must not be any drag on the threads when the fastener is moved, or it risks spinning the Riv-Nut.
For example, when you are trying to adjust or remove the old flap stop bolts, the threads extending beyond the Riv-Nut must be lubricated. If they have rusted, you can try cleaning with a Dremel, but you probably won’t succeed due to the tight space. When you try to remove them, you can loosen the check nut just a tiny bit, to ‘unlock it’; but you must keep it set snugly against the head of the Riv-Nut, while you try to back out the bolt. If you simply loosen the nut and start backing out the bolt, the Riv-Nut is almost guaranteed to spin in its hole. Once that begins, it is tough to stop it; but you can try snugging the check nut back down. The check nut should be kept snug enough that it is a bit difficult to turn the bolt out through it.
Install an anchor nut instead; using the smallest size Knipex pliers to set the two small rivets (they will fit inside the bracket to squeeze the rivets). If the bracket gets too mangled during the removal effort, a repair is required. You can make an aluminum strap in a U-shape, to wrap around the bracket; this is a very lightly loaded part. Rivet an anchor nut to the center of the U, with the nut’s body nesting in the old Riv-Nut hole; rivet the sides of the U to the sides of the original bracket. Before installing the anchor nut, relieve its self-locking feature by running a 10-32 tap into it. It does not require self-locking capability, as the stop bolt has a check nut to lock its adjustment setting; removing the self locking removes side loads on the bracket during adjustments, which halts the bending of the bracket.
The original stop bolts are simply a cheap, low-strength, all-thread AN bolt; they appear to be a home-made version of a proper adjustment bolt. For some unknowable reason, they are NOT the correct crowned-head adjustment bolt that is normally used for such an application. The proper bolt, which is a mid-strength, all-thread bolt having a radiused transition beneath the head and a crown on top, is a NAS428 bolt; standard hardware (but very hard to find). The crowned head, which has recessed markings rather than raised markings, won’t chew up the edge of the flap bracket, as so often happens with the cheaper original Beech part. I have these listed in the BAC Classifieds for $7 per pair, complete with a new check nut. The ones I sell are also shorter, as the Beech bolt is much too long; which in turn results in too much difficulty getting out the bolt the next time.
When you ‘set up’ the flaps, the bearings must be shimmed side to side in the brackets to provide proper end clearance at the aileron and fuselage, and to center the stop bolt on the face of the outboard flap bracket. If the bracket holding the stop bolt has been bent, it may require some repositioning to achieve proper bolt alignment