Fuselage

I drove down to Vans today during lunch break and picked up a couple of new F-715 seat ribs to replace the ones I ruined Friday night. I took one of my drawings with me to ask some questions. I had a nice chat with Joe Blank and one of the other guys... can't remember his name right now. I unrolled my drawing and asked specific questions about how I'm supposed to inspect the nuts and bolts that hold the seat belt brackets in place on the F-705 bulkhead, and how I'm supposed to inspect and/or maintain the bolts and nuts that hold the steps in place under the baggage floor skins, if these skins are riveted in place. "Don't you have to inspect those as part of your annuals?", I asked. "Do we bury nuts and bolts inside the plane anywhere else, where you can't readily get to them?" See, I had come to a point where I thought for sure I needed to make these floors removeable after all. Well... they really reassured me to go ahead and rivet them on. The worst thing that has happened to the steps is that a few of them have broken over time. They suspect overweight persons stepping on them over and over strains the metal until it fatigues and cracks. But even that is a repair that can be done outside the aircraft. The bolts on the inside have never caused any problems or come loose. And as far as the seat belt brackets go, they aren't aware of any ever coming loose. Worst case, you just drill out a few rivets and pull the baggage floor up. I can live with that. They went on to say that this part of the plane is structural and critical to the strength of the center fuselage, since it forms a "box" with top & bottom skins and ribs in between. So they prefer to have these skins riveted on. If they are removeable, they are afraid that someone may fly the plane without them being put back in place, and the plane is in a weakened configuration if you do so. NOT GOOD. So the issue is settled with me. I will be riveting the seat skins and baggage skins on. It's one less decision, and a lot less work.

So, back home, I put in a few hours this evening getting these new seat ribs prepared. After the usual deburring, I fluted and fitted them in place. This time, I ended up trimming less than 1/8" off the ends. Then you draw a centerline down the bottom flange and clamp it in place for drilling.

Once it's clamped in place, I flipped it over and laid it down on my small workbench. This turned out to be a perfect position for drilling. It's easy to see the line on the bottom of the flange through the rivet holes in the skin.

Here's the right side rib, halfway through drilling. A cleco in every hole. When these were all drilled, I drilled the end of the rib to the F-704 bulkhead.

A while later, after removing the rib, deburring and dimpling all the holes, deburring and dimpling the skin, it's clecoed back in place.

The holes turned out perfect, right down the centerline of the flange. It's now ready to flute the upper flange and drill the seat floor skin in place. I don't have a picture, but I finished that tonight, too.

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