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c1qfxugcgy0 · 2 days ago

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I will never complain about a toolbox being too far from the jobsite again.

(previous post in this series)

Large Aircraft Manufacturer (LAM) has announced, to the surprise of nobody with a brain, that certification of our latest aircraft, Advanced Widebody Carbon Wing (AWCW), has been delayed to March 2026.

This firmly sets management on the horns of a dilemma. They have something like five thousand expensively trained employees on the AWCW production line who will not have much to do for the next year. You can continue production and clutter up the hardstand with precertification aircraft. But the process of certifying the aircraft against severe weather, bird strikes, lightning strikes, etc etc, will inevitably require serious changes to the beta aircraft. LAM must then modify every one of their backlog aircraft, ripping out the interior, replacing bond wires and ground straps, then reinstalling all those parts. Doing structural work inside a complete aircraft naturally takes much more time than doing it from scratch in the production jigs designed to accommodate such work.

(And if you don't believe me, just watch This Old House.)

Naturally, LAM tracks every minute of worker time on each aircraft. Enough rework can wipe out LAM's entire profit margin on a bird, especially given the large discounts it offers to early buyers of new model aircraft.

This is not idle supposition. LAM was hauled through an identical hall of thorns when Advanced Midbody Carbon Aircraft (AMCA) was delayed in certification a decade ago. Fifty aircraft required expensive rework, putting the entire program in the red for years afterward. The scars are fresh, and LAM is not eager to repeat the experience. Thus, AWCW production rate has been cut to zero point zero.

But what to do with the workers?

Airplane factories are always attached to an airport. [citation needed]

Everything outside the factory is the flightline. Flightline is where all the problems with an aircraft catch up with it, and occasion screaming matches between facility managers (who are desperate to clear their patch of concrete and get the plane in the sky) and production managers (who will have the rare pleasure of seeing their face on the nightly news when that plane kills three hundred people).

Airplanes require a really incredible amount of maintenance. If production delays mean the plane doesn't get delivered to the customer on time, scheduled maintenance can happen while the airplane is being made. These are not problems that happen when you build cars, I can tell you. This is the shop I, along with 20 of my coworkers, have been loaned out to.

There are lots and lots and lots and lots and lots of moving parts on an airliner. Every LAM aircraft has a design life of 30 years. They cost hundreds of millions of dollars each. Because they are so damn expensive, our customers want to fly them as close to 24 hours a day as possible, in rain, snow, sleet, from Kabul to Kathmandu, from sea level to eight miles above ground. Sealed bearings, so beloved by the automotive industry, are simply not an option across aerospace's range of temperature, pressure, salt spray, and total joint lifespan requirements.

As a result, every single metal on metal joint on the airplane has a grease fitting, and a prescribed grease type for each fitting. In just the photo above there are seven fittings visible. The document that lists every fitting on the plane is eight hundred pages long.

But greasing the points is, honestly, not that hard. You've got eight hours to finish any given IP, and in a storage IP the greasing will take, at most, 30 minutes. Greasing is not the problem. The problem is the fucking skin panels.

The exterior surface of a wing is, uh, important. It carries the weight of the aircraft, it has to be aerodynamically smooth to a frankly annoying degree, each carbon fiber wing skin panel has to be as light as absolutely possible, the insulative carbon fiber composite must be coated with an outer antistatic conductive layer to bleed off static charge, but at the same time the inner layer needs a more conductive aluminum foil layer to conduct the powerfully destructive lightning strike energies each plane will experience, oh, about thirty times over its rated lifespan.

On that list of priorities, "making it easy for ground personnel to take a panel off" is low on the list of the priorities. Very low. Real damn low. Put on your SCUBA gear and investigate the pelagic depths kinda low.

You take off the panels. Maybe ten percent of the screws will strip when you apply force, which means you get to carefully, slowly drill out the titanium fasteners while standing at the top of a scissor lift in the rain.

(There is an art to drilling out a Phillips head titanium screw. Ordinarily, you want to use carbide tooling, which is sharp, but brittle. But even after stripping the hell out of a screw there will still be some remnants of the head, which the cutting edge of the carbide drill will catch on and break. So when your crew is assigned to a new plane, the first thing you do right away is rush to the tool room to get drill bits before your oafish coworkers clean them out, and get both HSS and carbide bits-- tough and ductile steel to knock down the remnants of the screw head and then carbide to do the bulk of the drilling. And once you're into the bulk of the screw, you do peck drilling-- three or four seconds of drilling, then pull the bit out and apply lube. This isn't for the benefit of the drill-- it can handle high temps just fine. What you absolutely, must not do, is let the screw get too hot. Because when titanium gets hot and then cools down, it hardens, and you just turned a ten minute job into a four hour one. Because after you finish drilling the hole you follow it with a steel screw extractor, and there's no extractor on Earth that's going to bite into hardened titanium.)

You apply Aeroshell 33 to the bushings on the slats torque tube and carefully brush on Cor-Ban 27L to the specified exposed metal surfaces. You call QA out, who bitches and moans the entire time for being rousted out of their crew shelter to get rained on to witness that you greased the things that needed to be greased.

Now it's time to put the panel back on. First, you throw away all the used fasteners and order new ones from Logistics. Any screw that touches a flight component is used once, and only once. Try not to think about the dollar value of the two pounds or so of aerospace titanium screws you just shitcanned. Be careful when reordering, though-- across the five or six panels you're pulling off you'll have two different types of screws of differing surface finishes, (structural screws vs. antistatic electrical bonding screws) different diameters and different screw lengths. Why? Because fuck you, you stupid mechanic. You deserve to suffer. Your life should be only pain.

(If you screw up on this step and can't button up a panel before end of shift you need to "short stamp" the IP saying what you did and did not do, check the panel into the WIP cage (remember to label it with the part number, IP number, and your employee number!) and then "maintain closure" by covering the empty spot with a sheet of plastic taped down along its entire perimeter with 3M 8979 duct tape. It is, of course, still raining while you're doing all this, because some fucking idiot decided to build an aircraft factory in the Pacific Northwet. Does duct tape stick particularly well to sodden wing panels? No, it does not.)

The one advantage of going to work at 5 am is that you never miss a sunrise

Assume you have all the screws you need and you haven't dropped any of the panels and damaged them while bumbling around. Apply Braycote 248 to the threads and start banging them home with a torque-limited screwgun.

Once installed, there are those two important electrical bonds mentioned above. LAM does not take your word that you've correctly installed the panel, of course, they want you to measure it. Getting the antistatic value is easy enough-- one probe on the head of the fastener, the other to the surface of the panel, value in the hundreds of kiloohms. Impossible to screw up.

What's harder is the lightning conduction path bond. That's measured in single digit milliohms, and it's from the foil lining of the panel to the structure of the wing. The foil is hard to access, since it's on the other side of the goddamn panel you just expensively installed.

Well, in some cases, you can just reach from an adjacent open panel. (The IP notes which panel does not require a lightning bond reading, and you are supposed to infer that this is the last panel to install.) But LAM defines "adjacent" somewhat loosely. By the time you are on the final panel, you are measuring bonds by duct taping one probe of the M1 meter to the end of a broomstick, crawling up the asshole of the plane, and jamming it against the back of a panel six feet away. This is as stupid as it sounds, and it takes several tries and quite a lot of fumbling around to get a good reading. If you don't get a good reading, then you will have the experience of taking the panel off, cleaning it real good, and then trying again, while your team lead breathes down your neck.

But if the readings are good, you unthread yourself from the guts of the wing, pound in the last panel, plug in your scissor lift, dump your cleaning materials contaminated with various exotic aerospace greases and weirdo solvents into the hazmat bin, return your tools to the tool room, and clock the fuck out. You've got a different airplane to grease tomorrow!

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