Shitty shitty shimmy

What wasn’t visible from two thousand feet above was just how rough the washboard forest road really was. Not the clean, flat, smooth ribbon of dirt it appeared to be when the engine failed; instead it was petrified ocean surf. Long chains of small ridges and shallow valleys, all closely placed, laid out lengthwise like dismembered and abandoned treads of a gigantic broken-down bulldozer. Still, the first few seconds after I touched down were smooth and relief flooded my soul. Everything was going to be OK. Then… Bam! The plane lurched once, then all hell broke loose. She was gripped by a grand mal seizure. Powerful, racking vibrations shook her stem to stern and wingtip to wingtip. The securely locked doors flung open, a blast of cold air flooding the cockpit. A geyser of fuel ejected from the header tank. Doused the windshield. I frantically pushed the yoke in, pulled it out, rocked it side to side. Stomped on the brake. No dice. In my mind’s eye I could see rivets popping from the skin and flying through the air in all directions. My flightpad holder separated from the dash and crashed to the floor. Then the seismic vibrations cleanly decapitated the bobble-headed dog figurine that lives on the glare shield.

Well, OK. We don’t really have a bobble-headed dog figurine on our glare shield. But if we had had one, it would have lost its head. The vibrations were that bad.

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Image: Amazon.com

Oh. And I wasn’t really making an emergency landing on a forest road, either. It just felt  like it. I was actually making a garden-variety landing on Runway 17 at Albuquerque’s Double Eagle II Airport, a perfectly respectable stretch of concreate. The washboard wasn’t on the ground.

It was in my plane.

It’s called “shimmy,” and this bout of shimmy was so bad it actually stalled the engine before subsiding in a quivering rollout, leaving me high and dry and motionless in the middle of the runway at a busy urban airport. Tower… we have a problem.

Clearly, I couldn’t put off dealing with this any longer. No more deferments. In aviation circles, putting off a repair is often called “owner-deferred maintenance.” It happens all the time, because no owner can afford to fix all the things that are wrong with any airplane at any given moment. Of course, you’re required by law to fix any safety-related items, but beyond those, there’s always a long list of optional repairs to little squawks that vary from barely noticeable, to mildly annoying, to seriously aggravating. These squawks tend to get worse over time, like an evolving species.

And my nose wheel shimmy had evolved from barely noticeable, to mildly annoying, to seriously aggravating. In fact, it occurred to me—as I sat smack dab in the middle of the runway trying to restart my engine with the tower ordering the planes behind me to go around—that my nose wheel shimmy problem had now risen to the level of a safety issue.

Why had I put off dealing with it for so long? Partly money. But mostly because there’s no easy fix, as there’s no clear cause. In ‘Coupes, shimmy originates either in the nose gear or in the control mast, or both. It’s largely caused by worn bearings and bushings that result in a system of components designed to fit tightly together not fitting so tightly together, allowing oscillating vibrations to build up. Sometimes it can be one part, but usually it’s a little bit of wear on a bunch of components. Tracking down the smoking gun(s) is a looooooong exercise in trial and error. Oh, and some of these parts require serious disassembly of the airplane to reach. Luckily, in our case, the bulk of the evidence suggested that our problems originated in the easier to reach nose strut, rather than in the cockpit control mast, which requires actually removing the center fuel tank to reach.

So what’s the big deal? Why not just replace the strut instead of messing with it, you say? I wanted to, believe you me, but there’s a problem. While we Ercoupe custodians (you can’t really “own” a plane that’s older than you and which will outlive you) are thrice blessed that Univair still holds the type certificate, and not only has an extensive inventory of new old stock, but can actually make many of the parts we need, they don’t carry or produce every part that makes up the planes, and the nose strut is a good example of this. Univair doesn’t have any complete assemblies, nor do they even have all of the components that might be needed to fix one.

This leaves the Ercoupe custodian in need of a nose gear repair in the role of Dr. Frankenstein. And like Dr. F, the custodian often needs the services of a good grave robber. Dead airplane parts are brought back to life using a combination of new parts, serviceable used parts removed from airplane corpses, and in some cases modified or re-manufactured parts.

So I think you can see why, ostrich-like, I just buried my head in the sand, even though I knew trouble was brewing. And in my defense, I was preoccupied with bigger troubles. But now that the rest of the plane seems to be largely working again (knock on aluminum) it’s clear to me that I missed a golden opportunity to deal with the shimmy, as you’ll soon see.

I’ll save you the Odyssey and the Iliad and just go straight to the cliff notes: In the process of trying to figure out our options, I learned late in the process that the outfit that rebuilt my wing tanks also rebuilds nose struts. I’m 70% thrilled. Why only 70%? Because that nose strut lay on the floor of my mechanic’s hangar for four months during the engine mount and forward skin replacement repairs. Had I known earlier, we could have had it done while the component was already off the plane, saving both money and flight time. Here, having just gotten the plane back after many months of not flying, it’s once again laid up for repairs and I’m at serious risk of becoming an alcoholic.

Still, I’m happy that someone with a good rep, who really understands these systems, is on the case. But meanwhile, having already missed out on the Georgia race—maybe a lucky thing or I might be broken down far from home—I’ll now miss the Spaceport’s open house and no doubt at least the next race, possibly the next two, costing me yet another season, depending on how long this takes.

Tess is back in Santa Fe once again, where I accused my mechanic of having an affair with my airplane, nose strutless and the strut is en route to the rebuilder. How long this repair will take depends on what they find when they tear it down.

Only then will we know how many graves they’ll have to rob to get my girl back in the air again, and landing as smoothly as she flies.

 

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