Owner Assisted Annual Inspection

October brought the deadline for my airplane’s annual inspection and, having no in-depth knowledge of the process and liking to get my hands greasy, I decided to get involved as much as possible. That meant finding a shop that was willing to work with me. In the end, Jeremy at St. Charles Flying Service came through.

Every airplane registered in the United States is required to have a thorough inspection at least annually. (Airplanes which are used for commercial purposes get one after every 100 hours of operation.) I knew that, in general, the “annual” consists of “checking everything.” I also knew that most shops flat-rate the annual at 22 hours of labor for a plane like mine, a Piper Arrow. Beyond that, I had few preconceived notions.

I scheduled the plane for five days in the shop and cleared three days on my calendar. That turned out to be just about right. So, to misquote the prototypical student, this is how I spent my fall vacation:

Wednesday

I showed up at the hangar in grungy clothes, carrying a toolbox full of tools. I found out Jeff would be doing my annual, which suited me since he has done work on the plane in the past and I have always been pleased with the results.

As I expected, Jeff assigned the grunt work to me with an off-handed, “Why don’t you remove the interior and open up the inspection panels?”

“Sure,” I shot back. No problem, I thought; except that I had never removed anything from the interior of the plane nor did I even know where all of the inspection panels were. But I had done lots of work on cars and figured that this couldn’t be too much different and, worse come to worst, I could always ask for help.

The front seats were pretty easy. I found a couple of brackets at the front end of the seat tracks. Once removed, the seats slid forward, tilted up, and could be lifted out of the plane.

The back seat proved to be more challenging impossible to figure out. Nothing tilted, slid, or moved enough to allow me to even see any screws or bolts which might allow me to pull the bench seat. After a confidence building 30 minutes or so, worse had come to worst and I asked Jeff for help. Jeff stuck his flashlight into the baggage compartment and immediately pointed out an aluminum grate which I should have removed. Behind that grate, I found four bolts holding the base of the seat to the seat back, all ridiculously placed and under nutty amounts of sheer pressure. Two of them had nuts on the ends but clearly none of the four were going anywhere easily. I pulled the bolts, unbolted the portions of the seatbelts from the cables which anchored them, and the base of the seat easily lifted out. The back stayed in the plane, hanging from a pair of bolts at the top, since it was not in the way.

Next came the inspection panels. I found six, two under each wing and one in each main wheel well. I also pulled the top of the “stinger” which exposed a bunch of the workings for the stabilator and trim system. Interesting stuff. The next morning, Jeremy pointed out that I had missed two plastic covers which protect the wing attach bolts and nuts, so those actually came off on Thursday morning. Now that I “know” what I am doing, opening up the plane for an annual inspection ought to take well under an hour. Next time.

Jeff had removed the cowling, drained the oil, and pulled the spark plugs while I was doing my stuff. I surfaced in time to “help” with the rest of the oil change. That mostly involved me dumping a good-sized pool of oil on the hangar floor (sorry about that, Jeff) and taking a lot of time to improve my safety wiring skills under Jeff’s tutelage (thanks, Jeff). I definitely made up for any time saved in opening up the plane by meddling with the oil change process.

With new oil in the plane, I unscrewed about six zillion screws and removed the spinner so that the eddy-current inspection guy could inspect the prop hub in accordance with a new AD. (No cracks found.)

Jeff had noted a few squawks, including cracked and broken baffling in the engine compartment, but nothing major. We were done for the day since Jeremy would not be available to perform the actual inspection until Thursday morning.

Thursday

I arrived bright and early so that I could see what comprised the actual inspection. Following Jeremy as he crawled under the plane with mirror and flashlight reminded me of the old mechanic’s joke about repairing a problem by tightening one nut. The cost was $300.25: 25 cents to tighten the nut and $300 for knowing which nut to tighten. In well under half an hour, Jeremy had poked into everywhere that needed poking into and made a list of things which needed fixing. The grossest was a mouse nest inside the wing. He also noted a few popped rivets, a spot of corrosion inside the right, main wheel well, and a need to replace the oil cooler hoses (which were not cracked but which had reached the maximum number of flight hours allowed by another AD).

I spent the rest of the morning fishing the mouse nest out of the wing with my custom crafted mouse nest removal tool (a/k/a an old coat hanger). Fortunately, the mice had not chewed any airplane parts into nesting materials. Even more fortunately, I did not find the mice.

There is a foam rubber pad in the middle of each main wheel well. When the gear retracts, this keeps aluminum from rubbing against aluminum if the wheel rises too high into the wing. Sometimes these pads hold water and start some corrosion and that had happened in the right well, though not on the left side. Jeff handed me some fine sand paper and I continued with the crud jobs on my back as he neatly worked on cleaning spark plugs and fashioning patches for the cracked air baffles for the engine compartment. Being the least skilled laboror on the project means that one gets to learn one’s place.

It took quite a bit of sanding to get through the paint and corrosion but I did it and then applied some green primer and covered all with a nice layer of white paint. Suffice it to say that the corrosion is gone, the metal is protected again, and it is a very good thing that my painting was done inside a wheel well where a) no one can see it, and b) it will prompty be covered with dirt.

Next on the list of entertain-Art jobs was replacing two air filters behind the instrument panel. The small one is bolted to the top of the firewall roughly behind CDI #1. This filter was darned difficult to replace only because it was darned near impossible to reach. Jeff loosened a bolt on the engine side of the firewall, which allowed the filter to move enough that I could barely reach it. I pulled off the filter element, a soft foam cylinder sort of like a small, two inch long sock with the toe cut off, without too much trouble. Getting the new one on proved more difficult since I really needed two hands on the job but could just barely manage two fingers (no thumb, thank you) from the same hand. I did eventually manage to get the darned thing in place and un-bunched-up enough that I am confident that the whatever air it filters will be properly filtered.

I would have felt good about a job well done had I not been upside down under the panel and in minor contortionary pain and facing the other filter-which-needed-changing. Suffice it to say that whoever designed that filter mount was a friggin’ sadist. No adult human without double jointed elbows can possibly reach that filter without sustaining permanent injury. Only by offering burnt offerings to the gods of Vero Beach was I able to extract the old filter, wrangle the new one into position, and wrestle the retaining bolt back through the firewall. Jeff helpfully turned the nut on the engine side of the firewall and offered helpful advice like, “You think that one’s bad? You should see the filter in the C210.” I have no idea how but I did change that filter and managed to get back out from under the panel.

The rest of the day was easy. I got to stand upright.

Jeff had pulled the fuel injectors and had them soaking in a magic solvent. I fished each out in turn, blew it dry with compressed air, reinstalled it in a cylinder, and tightened to the proper torque.

After that came the spark plugs, all eight of them. They were rotated front to back and top to bottom, sort of like rotating tires.

The last job for the day was reinstalling the spinner. Most of the bolts which held it on had been installed without nylon washers. Jeff found me some new ones so that there is less chance of cracking the spinner and I put everything back together.

Friday

I thought that Friday would be a short day, maybe even done by lunch time. How much more could there be to do? Airplanes really are like cars: when estimating a job, remember that everything takes longer and costs more.

FedEx had delivered the new tires and tubes to my house on Thursday so I hauled them out to the airport on Friday morning. The first order of business was to help jack the plane up again. Unlike a car, jacking up an Arrow is a two person operation. You put one jack under each wing and then two people jack in unison, carefully keeping the wings level, until the tail is high enough off the ground to allow the tail stand to be rolled into position.

The tail stand is a small barrel full of a few hundred pounds of concrete with a steel bracket on top. With Jeff and I each manning one jack, a third guy was good enough to wrestle this beast into place under the tail skid. Once there, he put a hefty bolt through the tail skid and the bracket and turned a nut onto the end so that it could not pop out. Jeff and I continued jacking. With the tail weighted down, the nosewheel then came up off the ground and I was able to pull all three wheels off the plane. Yes, you read this right. Jacking up a plane involves lifting under the wings while pulling down on the tail. For a pilot, this makes sense because we are conscious of the weight and balance of the pane when flying; it must be nose heavy. But from a car mechanic’s perspective, it is odd to have to pull down on the back of the vehicle while jacking the front part up.

The wheels are pretty easy to remove. One cotter pin secures one large nut which holds the nose wheel on. There are no brakes on the front so removal is trivial. The mains are only slightly more difficult. There are four safety wired bolts which hold the disk brake caliper. Pulling these allows the caliper to be pulled away from the brake disk. The brake pads drop out when this is done, two small ones about the size of my thumb and one larger one which opposes them. It truly is a remarkably small amount of brake pad for the work that it has to do. With the brakes out of the way, I pulled the large cotter pin which secured the nut which held the wheel onto the axle.

Jeff showed me how to disassemble and reassemble the wheels and then went off to clean and repack the wheel bearings. Disassembling the wheels is straightforward: pull the valve stems to let the air out of the tubes, use the bead breaker to break the tire’s bead away from the wheel, and then remove the three nuts which hold the two wheel halves together.

Putting it all back together is more “interesting.” I dumped some talcum powder inside a tire, shook it around to liberally coat everything, and then mushed the tube into the tire. The tire has a red dot which is the lightest side of the tire and the valve stem of the tube has to be aligned to this point. With the tube in place, I reassembled the two halves of the wheel, being careful not to pinch the tube between the metal halves. This all sounds easy but was surprisingly like dressing a two-year old boy in all the clothes he needs to go sledding, while he is jumping around with excitement because it is snowing. I did succeed in reassembling all three tubes inside all three tires onto all three wheels and nothing leaks, even after the plane has been on its new footwear for a month.

Jeff noted that the brake pads were all well worn so he replaced them. I was surprised to see that, unlike a car, replacing brake pads for a plane means replacing just the pads. Jeff drilled out the rivets that held the old pads to the metal backings and riveted new pads in place.

With the wheels reassembled and the brake pads replaced, I put everything back on the plane and, once again, humbled myself with my ineptitude with the safety wire pliers. Jeff showed me how to do it right and, while I am confident that the brakes on “my” side won’t fall off, Jeff’s side sure looks better.

The rest of the afternoon was consumed with changing the air filter (quick and pretty much like a car) and replacing the seats (just as much of a pain as it was to remove them). At 4:30pm on Friday afternoon, I was the only one still working in the hangar but I was determined to finish the darned thing up, and I did.

The only incomplete task was to change the oil cooler hoses. They had not arrived and Jeff would take care of that on Monday.

When all was said and done, I spent about 2 1/2 days of vacation on the job, had a bunch of fun, and learned a lot. Best of all, they didn’t charge me too much extra for the privilege.