After finishing the firewall forward part in Part 5, I took a break last weekend to fly (video here). That is one reason why I do this in segments, so if the weather improves, I can take advantage of it without the airplane spread all over the hangar. The risk, on the other hand, is that the weather gets good for a prolonged time and I have yet to finish. For Saturday 4/6/24, that was not an issue. It was a typical PNW spring day, perfect for indoor maintenance activities.
It is often easier to work on the airplane with the tail jacked up and in a closer to level attitude, so I put the tail jack back in. For safety, I put a stand under the tail, with some 2x4's to get the right height, but I leave the jack in place and have the weight shared between the two devices. I figure that provides some added safety.
The first thing I did was to open up all of the fuselage and tail panels. In some instances, it is quicker to do it all at once, rather than to do one small area at a time and put it back together as soon as you are done.
The first thing I wanted to do was to inspect the outboard horizontal stab elevator attach brackets for cracks per SB 00036 Rev 3. I did this for the first time last year, so the enlarged hole is already drilled, all I have to do is take my tape off and stick the borescope in the hole and take a look see. I was very pleased not to find any cracks last year, and even more pleased that after 23 years and almost 2,400 hours, there are still no cracks.
There is a terminating action to install a doubler on the aft face of the rear spar, but it involves drilling out no small number of rivets, which creates the opportunity to mess something up. Not only that, but it will undoubtedly chip some paint where the rivets are drilled out. I know that having no cracks now doesn't guarantee that I won't have cracks later, but a lot of the airplanes with cracks got them at far fewer hours than I have. So, for now, I continue to inspect.
I ended up taking a lot of pictures on both sides, mostly to make sure I had plenty to look at if I had any questions later. I am very fortunate with this airplane that the inside of the HS is very clean and the rivets are easy to see. There are some rivets with smilies on them (I didn't build the airplane) and they are aging very gracefully.
The spar is clean and well primed in a color that should make for easy identification of a crack if one were there and there is nary a sign of one, even on the rivets where the rivet set contacted the spar material. I'm very pleased.
While I was inspecting all of the fixed and moveable surfaces for damage, I also inspected the elevator spar rod end attachments for cracks per SB 14-02-05 and again found no cracks, though I didn't expect any.
This is one where Van's doesn't recommend adding the doublers unless there are cracks present due to the very real likelihood of doing more damage installing them than would be done by leaving them alone. I always wondered why there was a jam nut on this rod end used as a hinge since there is no way that the rod end can turn once assembled. Turns out, the jam nut is not there to keep the rod end from turning, but to transmit the load from the hinge to a larger portion of the spar face. Most, if not all, of the cracks were found on airplanes where those nuts were not tight.
As designed, that rod end threads into a large nut plate held to the spar with two rivets. The nut is added to sandwich the spar between the nut plate and nut adding a larger surface area to transfer the load (compared to just the 2 rivets).
This SB came out before I bought the airplane, so I didn't do the first inspection. The person who did made sure the nuts were tight (they were). I check every year mostly to be sure and every couple of years I put a wrench on the nut just to make sure it hasn't loosened. It hasn't. I think the ones with loose nuts that had cracks were probably on airplanes where the nuts were never tightened in the first place. It is an easy thing to miss.
After all of the inspections were done, I lubricated all of the hinges with LPS 2. I have found that a small syringe with a small needle on it makes it very easy to put lube exactly where you want it without having to spray a large area and have a lot of excess to wipe off.
With that, the tail is essentially done. All that is left is to clean and lube the tail wheel, then it is on the to forward fuselage.