Saturday, November 07, 2009

Time to Spare? Go by Air! (And accept unskilled help)

After our magazine reading and tower-visiting we check the engine nacelle. I put my hand inside the front of the cowling. "Hey, it's warm!" This is going to work. We discuss how we'll do it. Untent the right engine now and see if it starts. If it does, leave it running and then untent the left and throw the tent in the cabin. If it doesn't, tent it up again and go and see if hangar guy is back from lunch. We coordinate our movements as to who will do what, but then totally disregard the plan.

The right engine doesn't start right off, but it is sounding much better than it did, and we think we can get it started, but don't want to run the battery down. So we decide to start the left one first again. We put all the cords and tents away in the lockers, start the left to get an alternator running and then the right starts after a couple more tries. Hurrah! We run up the airplane and depart, first to the north to get out from under the local layer, and then to the east, over the mountains. The only traffic we see is once again a far-above jet visible only because of its contrails. And he got me again with his cry of "traffic!" befoe I saw that it was just a distant jet.

The scattered layer thins out just past the mountains and we descend above the flat terrain around Fort Nelson. We have a hangar waiting for us, and arrive in time for the people working there to not have gone home. It's now time for the next scheduled inspection, which is why our AME has been hanging around with us pilot types. He goes straight to work. "Can we bring you anything?" I ask.

"Hawaiian pizza with mushrooms."

I get a large and we bring it back, then ask what we can do. Generally at this point we're delegated to cleaning the junk out of the nose locker so the people who do the real work can get to the battery, or just asked to stay out of the way. It's often less work to do something yourself than to get unskilled labour on it. But this guy puts us right to work. My first job is to remove a couple of manifold heat muffs for inspection. The inside looks like a medieval weapon, with all spikes on it, presumably to help with heat dissipation. He inspects them and I put the muffs back on.

Then he asks, "Have you ever used lockwire pliers?" I haven't, just seen them in use, and seen the results many times. Airplanes have a lot of vibration and vibration has a tendency to cause threaded fasteners to work loose over time. It's fairly important that parts not fall off an airplane in flight, so we use lockwire to back up the fastener. It's fairly thin wire wrapped between a removable part and some other part of the airplane, and wrapped in the direction such that the wire is pulling it in the tightening direction. In order to loosen, the part would have to pull the wire. The wire is always two strands, twisted together incredibly neatly. My admiration for the neatness of this process went down a little when I discovered that there is a special sort of twirly pliers that twists the wire together, but it's still an art. He showed me how to do it on the first part that needed lockwiring, and then send me to replace the hydraulic filter.

That required first cutting the old lockwire holding the filter in place. Sounds easy, but it was a little tricky because it was a tight space and the wire is twisted tightly, so you have to cut it very close to the end, or untwist it in order to get it off. I did a bit of both. Removing the old filter was also tricky, because I didn't know exactly which part was coming off, so I was turning it the wrong way at first. Now it's off, and he has provided me in advance with a rag to catch the fluid that drips out as I remove the case from around the filter.

The filter is a corrugated tube inside the case, and it stayed on the airplane as I removed the case, something he remarks on as being unusual, but desirable, as it's a little tricky to get out of the case otherwise. I'm now left with a tube about the diameter and half the length of my mini-maglite flashlight. It's filled with red hydraulic fluid. "Can I dump this in here?" I ask, indicating the big bucket under the nacelle, into which the last of ten quarts of dirty engine oil are dripping. He says yes, and I upend the little cylinder. The hydraulic fluid pours out but there's a little extra splash and a shift of weight that suggest, "Uh, there was something in there that I shouldn't have dumped in the bucket, wasn't there?"

There was. A little spring. He offers me a magnet on a stick, but the spring doesn't seem to be magnetic, so he finds me some gloves so I can root around in the bucket and find the missing part. Oh man. I'm the absolute definition of why it is less work to do something yourself than to have unskilled help. I find the spring, clean it, the gloves and the magnet on a stick, then reassemble it all with a new hydraulic filter. Now I have to lockwire it in place. I can't get the lockwire pliers to do the little twisty thing, though. Turns out I'm squeezing the release as I squeeze the pliers. That sorted out, I make another stab at it. First try, is completely awful. I cut the wire off and try again. The second try is salvageable. I have to untwist some of the wire and then retwist it better around the part. When I "finished" I still wasn't sure it was tight enough, but he was busy at that moment showing my coworker how to remove brake pads.

I learn how to remove and replace brake pads, too, and then I look after the right brake while the other pilot does the left. The AME checks up on how we're doing, tightens up my lockwiring job and calls us "my young apprentices." He seems pleased with us and pretends we're better than some of the apprentices he has to work with.

"Your apprentices must love you!" I muse.

"Why?" he asks, genuinely confused as to how taking the time to give clear instructions, trusting people to try things and patiently tolerating screwups is anything worthy of appreciation. I guess he's just a natural instructor.

Once everything is done, we clean up and put away the tools, and we get to leave the airplane in the hangar overnight. Ahh, luxury. The cost per night to keep the airplane in the hangar is almost as much as my hotel room, but it's worth it.


Marc Cote said...

When I was in the Marine Corps working on A-4 Skyhawks in the 80's, a newbie had to prove they could properly twist and install safety wire by hand before they would ever be allowed to use safety wire pliers to install it. Been a long, long time since I saw a pair of those.

Sarah said...

Your AME sounds like a great guy, though with awful ( or no-accounting for ) taste in pizza. I loved the image of him helping you find the part in the oil pan.. I bet he didn't even roll his eyes.

Was this safety wire twister like the tool? I've never seen one, though I've not been lucky enough to be momentarily apprenticed to a mechanic ... or an aviation medical examiner, which is what AME means down here in the US.

PS - you should tell your fellow pilot the story about the boy who cried wolf. "Traffic! Haha, sure, you won't get me again..."

Samwise said...

Hum. The way I've been taught, you're not supposed to re-twist safety wire (something about the metal getting brittle if wound and unwound repeatedly), and instead just cut the wire and try again if it doesn't work. I'll need to verify that from a manual someday.

Otherwise, your tale about encountering the intricacies of safety wire in confined spaces sounds extremely familiar to someone doing pilot/owner maintenance on the flying club's planes... The art of tricking a cold engine to start, too, the winters here in Finland do tend to get rather chilly at times.

@Sarah, the "Manual return" version of the tool in your link is more or less exactly the same as the one I've suffered with. :)

jk said...

If you got a safety done in a tight spot on the second try, as a beginner, I'd say that's pretty impressive. I've saftied many of the easier things during maintenance (preventative on my own or under supervision) and it might take me 3 times to get it right on something like the bolts that hold the brake calipers on. I can pretty much get my oil filter safetied correctly on the first try now but that took several times.

Fortunately wire and unskilled labor time are cheap :)

Ed said...

... or an aviation medical examiner, which is what AME means down here in the US.

...and in the UK.

Chris said...

"...taking the time to give clear instructions, trusting people to try things and patiently tolerating screwups is ... worthy of appreciation."

I think you have defined the essence of what skills a good teacher of practical skills requires.

In Oz, a aviation doctor is a DAME, seeing as how the comments have drifted in that direction.

Aviatrix said...

Our aviation medical examiner is a CAME (C is for Civil), but most people just say "the doctor who does my medicals."