life on earth and corrosion

One of the outside (not owned by my company) planes that we maintain is an old DeHavilland Beaver.  Produced in the 50s, they were built to be a bush plane.  There are a few around here that are well maintained, making them a dream machine to work on and see flying.  The one we get to work on was operated in Hawaii for many years, flying in and out of salt water.  Corossive environments such as that are detrimental to aircraft structures, and extreme measures are required to keep them safe. 

That got me thinking about life as a Christian.  Growing up, I often dreamed about a point of maturity where the Christian walk will be easier.  As if there is a point where I will be so tight with God, that I don't even entertain distractions.  But as I have grown up, I am realizing the case will never be.  I think even in Heaven we will be growing and building our relationships with God.  Sure the sin nature will be gone, so it probably will be easier.  But that's not the point I am going for here. 

As I was pondering why it is so hard to maintain a relationship with God, I thought about the world in which I live.  I realized that the problem isn't just me being bad at relationships, its the environment, kind of like float planes in salt water.  So what do I do with this information?  Do I just let my plane sit in the harbor and rot?  Or do I drag it onto shore, spending hours washing it off with fresh water, inspecting to make sure the paint is keeping the metal from being exposed, and coat all hardware with a rust-inhibiting chemical? 

Do I accept the environmental hazards, and let my relationship with Christ fall victim to harsh conditions, or do I see the challenge, and take extra precaution to protect myself from the world? 

If you know me at all, you probably know which option I strive to achieve.  It's just comforting to me to be able to identify why it is difficult :)

a day in the hangar

I have been working in the hangar for 9 months now, and have not introduced you to the characters I work with. I have given them all nicknames based on events that have taken place since I have been here, and that is a good way to introduce them. These nicknames aren't what I call them on a regular basis, but I will use them here to keep things sorta straight.

Dom- He's the Director of Maintenance. He got his mechanic's license through an internship here, and has been wrenching for 10+ years. Now he mostly works on paperwork. I usually spend lunch break (when the weather is bad) in the same room as him, since we both live far enough away that its not entirely worth it to go home over lunch. He plays his video games, and I entertain myself on the computer.

Sprocket- He ordered a sprocket for a bike or 4 wheeler, and it turned out to be the wrong one. It was really shiny and pretty, so I suggested he make a clock out of it. I don't know if he ever did, but the sprocket sat on his tool box for a majority of the spring.

Radio- Claim's he isn't very good at anything electronic, so he hops on any project of that variety to improve his skills. I try not to borrow tools from him, as he really doesn't like people using his tools.

Redneck- had a 6 wheeler that he decided to tear one axle off of, dubbing it the "fix wheeler." Most likely to jury rig anything that's not an airplane together, but pretty smart when it comes to making something work and be airworthy as well. Now lives in Soldotna working on projects there.

Parts Girl- She comes in twice a week to order parts, organize parts, and otherwise make our lives as mechanics easier. I don't know what we would do without her!

the tall one-actually that's the name his wife calls him. He's 6'4" or something like that. Grew up out here as well.

"everything that doesn't fly" guy- (OK, so I need to come up with a better name for this one) He is probably smarter than anyone else in the hangar, but he doesn't have any desire to work on airplanes. So he is usually beyond his eyeballs in grease working on vehicles, toyo stoves, machinery, and wiring. He is building a new house for his family, and they are hoping to move in by the end of July last I heard.


There are a couple others that haven't been around long enough for me to come up with good names. I will tell you about them when I get a good name for them. There are also a few that I am not in quite as direct contact with (ground crew, dispatch, and guy in charge of flight ops and personnel and just about anything else) so its not likely that I will be telling stories about them.

navajo flap part 2

8. Drill pilot holes. I kept the removed pieces for this step. I started with the new leading edge in place, and put the old trailing edge over it to show me where the holes in the spar go. I drilled about 2 holes per bay, then took everything apart. Next, you SHOULD do the same with the new trailing edge and old leading edge. I didn't which gave me a bit of a challenge. Once the old piece is cut, you lose all reference for straight and not twisted when you go to drill more holes. Keeping everything straight was the biggest challenge for me.

9. Drill the rest of the holes. Once you have pilot holes drilled, cut the old piece into two down the middle, and attach it to the new skin by the pilot holes. You use the old skin as a guide to drill all the new holes.

10. When all else fails, ask the resident welder to build you a jig. He saw me struggling to keep things lined up, and recommended it. He took about 15 minutes to make the jig, and it was well worth it. It kept the spar straight, and just required something under the trailing edge to keep the ribs aligned.

11. Check alignment and trim pieces. After all the new pieces are drilled, put it all together with clecos to check alignment. I discovered that I had to remake a piece at this step, because the holes wouldn't line up. As you remove pieces, mark them for trimming down to the final size. Another way to mark pieces for trimming is to go back to the old skins, and use them as a reference for where the edges need to be. Since the pieces are already folded, you can't just shove them in the shears and stomp. I used a combination of the pneumatic shears and a die grinder to make as straight of lines as possible, then cleaned all the edges up with a scotch brite wheel.

12. Rivet everything together! As I observed during removal, half of the leading edge was riveted on, while everything else was cherried. So depending on who the availablity of someone to buck rivets for you, you can either start with the trailing edge, or the riveted side of the leading edge. I have heard rumors of guys who do the whole thing with only a couple cherries, but I am not that good. We annealed (heat with a heat gun, then quench) the rivets before shooting to make shooting easier. On the cherry rivets, shop practice is to dip them in JB weld to help hold everything together. Also, a pneumatic puller makes life awesome in this project.

13. Paint. After both flaps are rebuilt, it time to have some fun! At this point, its the usual paint prep: etch and alodine! we have a grate in the middle of the hangar, so if its a piece too big to do in the sink, we pull up a table, sawhorses, or something over the grate to make cleanup easier. Then the pieces get hung in the paint room to dry. When ready to spray, its simply mix paint, put it in the gun, and go for it.

14. Rhino-line the bottom. After the paint is dry, some mask off everything you don't want rhino-liner on. I'm a bit unclear as to how the spraying procedure of this stuff is going to go, so I will let you know when I get it done.

overall, its been a great learning experience for me. I only have one flap done, so I will apply everything I learned from doing the first one into working on the second one when things are slow enough in the shop for me to work on a project!

navajo flap

Well, when things slow down in the maintenance hangar, we start pulling down more involved sheet metal projects from upstairs. One recurring project is rebuilding flaps. After countless landings on gravel strips, there seems to be more dented metal than straight, so we pull flaps off and put on rebuilt ones, leaving the beat up mess to be rebuilt on a slow day.

Several weeks ago, I was looking for something to do, and the hangar was looking pretty clean, so Dom invited me to pull down a flap to start on that project. I've done a bit of sheet metal in my limited A&P experience, but nothing this involved or structural. Or if it was something this involved/structural, I was usually just asked to pull the trigger on the rivet gun, while someone else was doing the majority of the work.

Here's a description of the process, what I am learning, and how I have messed up so far. Someday, I will get a camera and have accompanying pictures to make it more interesting.

1. remove old skins. Flaps are generally put together with a bunch of cherry rivets, so you can either power through the removal process, or take time to practice removing cherries without damaging the surrounding skin. I tried a couple different methods, and found that I definitely favor the die grinder with a cut off wheel, rather than a carbide bit (I saw someone use this method, and thought I would give it a try). I found the carbide was much harder to control, as well as slower. The cut off wheel worked quickly, and is easy to avoid the skin if you are careful. After grinding down the head, I punched the core out with a small punch before drilling off the aluminum.

I also left the stringers on at this point, so I could figure out later which one went where.

2. clean. After as much abuse as these flaps get, they are usually full of grime and grease, amongst other things. I donned gloves, safety glasses, and a rubber boots as I pulled out the etch and scotchbrite to break down the build up. Some of the small places are tough to get into, but its worth it to get it good and clean. You could miss some corrosion if you don't spend time to clean it up properly.

3. inspect. Depending on how bad the corrosion is, sometimes patches are necessary, sometimes entire ribs need replaced. Usually a little bit of a bent down rib can be straightened rather than replaced. Determining the safest, most cost effective method is the challenge here. For me, I just had to straighten a few bent ribs. The corrosion wasn't bad at all.

4. Remove corrosion. Thus far, I have mostly used a scotchbrite wheel on a die grinder to remove pitting. Some areas were very difficult to get to, so I had to sand at those for a while. The worst spot of corrosion wasn't completely through a rib, but all that remained was a thin film of aluminum, so I broke it off and built a patch.

5. Order parts. Determine the number of cherries you will need to rebuild the piece, taking into consideration length as well as whether they will need to be oversized. When you come up with a magic number of how many you think you need for one flap, multiply it by two (cause the other flap is next) then use the 150% rule. I had to order about 450 rivets, because we had a bunch in stock already. Also make sure you have enough sheet metal (check thickness according to the maintenance manual) for the project, as skin pieces are usually pretty long. I didn't need to replace any ribs, but if I had to, I would want to order them as soon as possible.

6. strip paint. Odds are, you don't have to replace ALL the skins. I had half the flap still good, so I left that skin on, removed the paint, and was ready for the next step. Also beware of what stripper you are using, and its effect on steel. The attachment pieces are steel, and corrode quickly with common strippers. Be sure to tape over them with aluminum tape, and check them quickly after you are done stripping to make sure they don't turn orange in an hour. I had to clean them up with more sandpaper, and spray them right away with zinc phosphate to keep them from getting any worse.

7. fabricate skins. WHAT A PAIN!! This was the worst part for me. First off, the leading edges are not an easy piece to make, especially if you have to do a piece that is too wide for your roller. I clamped a steel pipe to a table, and bent the metal around that to get about the same shape as my leading edge. Secondly, the trailing edge has a very sharp radius with a tight bend. The piece of metal is too big for our bending brake, so we have this jury-rigged plywood and screws bender that doesn't impress me. I asked someone for help who had recently build his own set of flaps (that replaced the set I am working on) and he jumped around on it for a bit, and handed me a cracked piece of metal. I finally got one to sort of work, but am planning on visiting another hangar with a wider brake when it comes time to fabricate the skin for the next flap. The most important part of fabricating skins for this project is to leave plenty of room. Don't trim your pieces to size until you are ready to rivet everything together.


to be continued...

signs that you work for a 135

(refer to post on 7/22/2010 for longer definition of a 135)

135 refers to the rules under which my company operates. Its a little different than your typical airline, both in size of aircraft and nature of operations. Here's a quick, basic, generalized definition: 135 refers to on demand operations, while 121 refers to airliner operations with scheduled routes.

So as I embarked on a trip to the lower 48, I realized several little things that I wasn't used to, even though I am on and off "commercial" airplanes a lot.

1. While I had to make certain my suitcase was under 50 pounds, I did not have to weigh myself for the flight.
2. There are some things that I can't take with me as a carry-on.
3. My stuff won't be within arms reach in the event of a stop somewhere.
4. Security? I have to go through security?
5. Its still a thing that you have to take your shoes off, right?
6. What do you mean I can't sit up front with the pilot?
7. I probably won't know anyone on the flight. Nor will I be familiar with their family that regularly flies with that particular air carrier.
8. Right, I don't work for these guys.
9. Oh I guess I actually have to turn off my cell phone...

Eventually, I got over the differences. But it was a good start to my "tropical" getaway!