Thursday, December 02, 2010

Fake It 'til You Make It

Two of us are at breakfast, with one guy late, but it's his birthday so we cut him a break when he wanders down sleepy just as we're ready to go. Once at the hangar I open all the under-wing panels on the right wing, collecting all the screws in a can, then go back to ask for another task. The AME who doesn't know me tells me to inspect the cabling visible through the ports. I reject that task, "I think you should do the inspection. I don't have any experience inspecting the insides of my airplane." That probably sounds stupidly squeamish. It's a cable. A four-year-old child could probably look at it and determine whether it was frayed, corroded, chafing, jammed or sabotaged, versus intact and functional, but surely they have some grunt work for me.

He shrugs and tells me to replace the pneumatic air filter, telling me it's installed under that panel there on top of the nacelle. The replacement part is on the bench and the only tricky part is that I should note which way the airflow arrow points on the installed one, and put the new one in the same way around. People dumber than me and with far less personal concern about the safety of the aircraft work as apprentices under the supervision of an AME every day. Many of them on my airplane. How much more complicated is this going to be than LEGO? I find the right kind of screwdriver and remove the panel, revealing a part with an arrow marked on it, differing from the replacement part only in colour. This one is kind of silverish, while the replacement is gold-toned. It has a bulge in the middle, about the size of an elongated softball, and then tapers down at each end to a ten-centimetre connecting tube. I can't see how the connector attaches to the line in the airplane, because the connection is covered at each end by a thick but flexible cuff, extending beyond my view through the panel in both directions. It's also held in place with screw clamps and numerous zip-ties. They look like the regular zip-ties that you can get at the hardware store, but I'm told they are special airplane-grade zip-ties.

This may or may not be true. You can never believe anything an AME tells you. It's part of their training, perhaps, that they keep up an incessant stream of bullshit just to see how much they can get a pilot to believe. At first I thought they did this entirely for their own amusement, because how hilarious would it be when one AME fixes a problem then tells a pilot her fuel cap was stuck because the cap had become desynchronized from the propeller governor, and then a month later she walks into another shop and asks for the synchronizing spray, because her fuel cap is stuck? But now I think they do it as protection from pilots who have a little bit of knowledge and try to tell the maintainers what is wrong. Pilots are very good at sounding authoritative and knowledgeable about things we have the faintest clue about, because that's our job: to navigate a complex machine through extremely complex and only partially forecast environmental conditions while assuring everyone involved that we know exactly what we're doing. So the maintainers stack the deck against us, and then they can tell our knowledge from our bluffs. Which is why I report snags by stating exactly what I observed. Not "the bulb is burned out" but "the light is not illuminated when the switch is selected on."

I draw an arrow on the nacelle, under where the panel will cover it, to indicate the direction of the air filter arrow, then I cut all the zipties and try to figure out how to get this part out. Typically the jobs you give unskilled labour are the ones that require very little knowledge, but are uncomfortable, tedious or annoying. So I am expecting this connector to work on the principle of pain and annoyance. I wiggle the whole thing in the direction of the more enveloping flexible cuff, in the hopes that the smaller one will slip back and reveal whatever it is at the end that I have to undo. The edges of the sheet metal around the opening in the nacelle appear to be the most likely source of pain. "So," I ask, "Do they sharpen the edges of the aluminum at the factory, or is that something you have to do yourself?" That gets a laugh and an expression of solidarity. I think I have identified the primary danger here. I keep wiggling the air filter and eventually the rubber cuff just slips off one end and that end is loose. There is no connecting snap. It doesn't screw in. The flexible sleeves themselves form the connection between the filter and the line it is inserted in. It's not high pressure, and it's just air, so that makes sense. I wiggle the other end out and ready the replacement, taking the rubber caps off the end and entering today's date in the space provided on the part. It's not too hard to wiggle it back into the same space, and I get the various clamps and zip-ties into place without too much damage to my forearms. I leave the panel open for inspection and move to the other side.

This one has a different screw-clamp to zip-tie ratio, but is basically the same. The arrow is pointing the same way if you think of it as "to the right" but the opposite way if you think of that as "toward the wingtip." I wasn't expecting that. I mark the arrow direction on the airplane again and then notice that the date marked on the installed air filter is only three months in the past. I ask if I should leave it, and he says yes.

My next task is removal and replacement of the brake pads on the left main. I've done this one before. It's easy to loosen the bolts to release the metal plates with the pads on them, then I have to pry the old brake pads off and get the new ones to jam in properly. I reassemble the brake, but there is now a hydraulic leak evident. They suspect that the o-ring has been cut? I don't get a clear answer from them as to whether this is on account of some error on my part, which means I suspect it is. If something goes wrong completely unrelated to what the pilot is doing, the AMEs typically pretend to give her hell for it. But I suspect they aren't chewing me out for this because it really is something I did, but I did it under their supervision so it's their fault. I know about that. If the FO makes an error, it is the captain who takes the blame.

We go for lunch, and when we return it's still leaking, so they add o-rings to the parts order. I take the other one apart more carefully. The brake pads are held against the plate by friction around tiny posts, and one of the AMEs shows me how to mushroom the posts when the pads fit too loosely. If it wiggles when it's in place, it's too loose. I have to hammer the post with a spike to spread it out a bit. He laughs at me for my tentative hammering. The pad wiggles, still wiggles, I keep hammering on it, and then I manage to spread it too much. I'm honestly not trying to get them to send me away. Now we need another brake rivet. The guys are looking around the hangar for this small, common part and then we all laugh as we remember that this is a helicopter repair hangar. Helicopters don't have brakes. (Cue everyone telling me the exceptions, in the comments). The helicopters that normally inhabit this hangar on don't have retractable landing gear, either, so we're also missing a hydraulic cart. The professional manages to fix the brake plate and we get that reassembled.

My next task--you'd really think they'd find something disgusting and foolproof for me now--is to replace the left side alternate air cable. The cable runs from a push-pull knob on the cockpit control panel out to the door in the engine that I can open up to admit combustion air, should the primary air intake become blocked. I have never had to use this for the safety of the flight, only ever tested it, or opened it when it was on an emergency checklist, but blocked air intake has never given me grief. Nevertheless it has to function for the airplane to be flyable. It works, but there is wear in the cable. Following vague instructions, I go into the cockpit and under the dashboard with a flashlight. I identify the cable that comes out from behind the left alternate air knob and start to follow it. It goes under a panel, so I remove that panel, which requires me to remove the scuff-plate for the pilot's feet, which involves crawling under the dashboard and removing the carpet in the cockpit, which is filthy. I pull out the seats, and get to work. After a geologic era or so or so of cramped awkward frustration with small spaces, cut hands, and stripped screws, I ask, "Don't you guys start to hate airplanes?" They're enjoying my misery, not so much just to see me suffer, but because they're seeing that I'm appreciating the difficulty of the work they do.

This is actually a little bit fun for me because there is pride in accomplishment and the sparkly feeling of new brain connections being formed as I solve a problem I haven't been exposed to before, and learn new things. I realize now that AMEs aren't robots programmed with the instructions on how to fix airplanes. They have the meta-knowledge of how to work out how to fix them. That's why my instructions aren't "open panel X and remove cable Y" but "look around and figure out where cable Y goes, and how to remove it." The experienced guys of course have a better idea than I do of where the cable is going to go and how it will be attached, but they can be just as surprised. I've exposed all of its treacherous path through the airframe and we'll pull it through tomorrow.

We leave the hangar at 7 p.m. and go back to the hotel to shower and have supper, then do a Wal-Mart run for shop towels. I also get a dirt cheap sweatshirt (made in Cambodia!) to get grubby in and an equally disposable t-shirt with a sassy slogan. It's marked as my size so I didn't try it on, but it turns out to be too small, which may be suited to my mission tomorrow morning to persuade someone to lend us a hydraulic cart. Clothing has no influence on aircraft cabling, but is there anything a woman in a tight t-shirt can't borrow from a hangar full of men?

Breakfast will be at seven tomorrow.


Frank Van Haste said...

Dear Trix:

The most dangerous thing in aviation is a pilot with a screwdriver. :-)



dpierce said...

Cue everyone telling me the exceptions ...

Does a rotor brake count? :-P

is there anything a woman in a tight t-shirt can't borrow from a hangar full of men ...

That's cheating. Guys have to bring other guys a case of beer.

GPS_Direct said...

is there anything a woman in a tight t-shirt can't borrow from a hangar full of men ...

That also works with finagling rides/demo flights in cool airplanes too... Something that the case of beer trick doesn't seem to cover for me. No fair!

Ward said...

Pics or it didn't happen!

A Squared said...

but is there anything a woman in a tight t-shirt can't borrow from a hangar full of men?

A coat with which to cover up?

Echojuliet said...

I replaced a filter just like that today. The filter was described to me as "a metal can with a boy sticking out of each end." I rolled my eyes when I saw the red caps on the ends. Gotta love working in a hangar with all guys.

What we do to solve the brake pad problem is a little spray adhesive. By the time the pads need replaced again, the heat generated by friction will have long ago melted the glue off.

I always find cinnamon rolls to be quite persuasive, since I work around married men.

A Squared said...

He shrugs and tells me to replace the pneumatic air filter

As opposed to hydraulic air filters, or pneumatic fuel filters?

Doesn't replacing the filter with the arrow going the same way as the previous one pre-suppose that the previous one was installed correctly?

Not sure that is a valid assumption

Anonymous said...

from Aviatrix in Hong Kong on the way home: as opposed to the instrument cooling air filter, the cabin air filter, and the engine intake air filter. Different kinds of air as oppsed to different kinds of pneumatic. And another AME later told me it didn't matter which way the arrow went, as this particular kind was symmetrical and only had the arrow for backwards compatibility. But recall previous comment about never being able to believe anything an AME says, as they BS pilots constantly.

Anoynmous said...

The arrow is pointing the same way if you think of it as "to the right" but the opposite way if you think of that as "toward the wingtip." I wasn't expecting that.

Unless the engines are counterrotating, the inboard/outboard asymmetry seems perfectly reasonable to me.

TgardnerH said...

@dpierce: Don't worry, Aviatrix pays her beer-debts. It's a good story

Anonymous said...

Did you get the hydraulic cart? The is a boob trend this blog has taken..... I'm not complaining, just sayin'!