Throttle Tale—Part 2

Low, un-forecasted, icky clouds have the north side of Dallas/Fort Worth socked in. I’m in Stark’s exceedingly stark little terminal building, which resembles an abandoned construction shack. Dirt and dead bugs form alternate layers on the floor at the base of the walls and on the windowsills. There are water stains on the ceiling tiles—at least the ones that haven’t fallen down—the windows are fifthly, bright orange rust mars the sinks, and let’s not even talk about the toilets.

But at least it’s shelter from the wind, and the air conditioning works. After wiping mystery crumbs and the dried carcasses of dead moths off the table with a scrap of yellowing newspaper, I sit in a faded plastic cafeteria chair and use the mobile hotspot on my cell phone to check the weather on my FlightPad while nibbling on a “meatasaurus” sandwich. When you travel slow, you can’t take the time to drive into town for lunch.

I have a choice: I can wait an hour or two at Stark for the ceilings to rise, or work my way around the south side of the city. It’s a longer ground track, and it’s into the wind. Still, I’d rather waste time in the air than on the ground.

At least on this ground.

I finish my sandwich, gather my things, and head back to Tessie. Up onto her left wing, toss the lunch bag in back, step over the fighter plane-style sidewall into the cozy cockpit, then slide down into the seat. I love the way my Coupe wraps her loving arms around me. I slide the doors up over my head and run through the engine start checklist. If I don’t use the checklist I tend to forget to open the master fuel cut off, and the engine stops about 30 seconds after starting, embarrassing when other pilots are watching. There’s not much risk of that on this blustery, hazy day in Onley, Texas; but still…

Engine up and running I test the throttle. It runs normally. Yeah. Must ‘a been some sort of weird fuel/air thing with the conditions. Clearly everything is fine.

I head out into the haze. Into the headwinds. Leveling off in cruise I’m just shy of the TACH redline for maximum speed. On the highway below me I see a U-Haul truck overtaking me. The driver looks up and me, shakes his head, and pulls away. Next, I’m over taken by a group of aging hippies in a battered VW microbus, two old ladies in a 1974 Yugo, and a kid on his bicycle who’s delivering newspapers.

This is going to be a long flight.

I have a track planned: A long, loping circle around the south side of Dallas. But I know that as the temperature rises, so too will the clouds, and I hope to take a short cut or two. I keep an eye on the ceilings being reported through my ADS-B, and I’m grateful for the advantage of near real-time weather reports from over the horizon that my pilot forefathers didn’t have.

Sure enough, as I fly south, ceilings to the east of me begin to improve, and I tighten my circle. Terrell lies on the east side of Dallas. If it weren’t for that nasty Class Bravo airspace around the huge Dallas/Fort Worth International Airport, it would actually be a straight shot from my home base—but I must go around either north or south.

By the time Terrell finally comes into view, I’ve had enough flying and I’m looking forward to calling it a day. I make my radio call, come into the downwind, and remembering my throttle excitement on my last landing, leave the carb heat untouched. Down over the trees I swoop, base to final, and, darn… A little low again. I throttle up. Nothing happens. My heart jumps in my chest. I shove the throttle forward. Nothing happens. The engine is running, but at idle. Temps good. Oil pressure good.

I pull the carb heat on, pump the throttle and the engine roars back to life. This time, it is only a matter of seconds. Long seconds, but seconds nonetheless.

What the Sam Heck?

I touch down, shaken, not stirred. I taxi off the runway, using drunk driver corrections to the left, and counter-corrections to the right to get Tess to track straight ahead. I feel like a child playing with a toy car simulator.

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Image: Amazon

Is this getting worse, or am I just tired?

The next morning Tess has a bunch of cables taped to her nose. And a strange little box, facing her prop. I’m getting the prop dynamically balanced. Not that I think there’s a problem, but at last year’s annual we had a brand-new RC Allen electric attitude indicator put in. It failed at once. We had to pull it out and sent it back. They replaced some bearing or bushing or something, and back in the plane it went. When we next flew, it failed again. This time, when we sent it back, they couldn’t find anything wrong with it. Naturally, I had to pay for the installation, de-installation, re-installation, de-de-installation, re-re-installation—so I was getting a little hot under the collar about a two thousand-dollar instrument that had never worked, and was getting even more expensive in the effort to get it to work. All of this has taken nearly a year due to the long periods of down time with various other repairs that have been plaguing us.

Anyway, my lead mechanic talked to the folks at Kelly Manufacturing (who make the RC Allen products) and they decided perhaps it was a vibration issue, which is what led me to my adventure at Double Eagle II. I’m not sure if I mentioned it, but after spending most of a morning there, the shop I’d gone to for the prop balancing couldn’t get their gear to work, so it was a wasted trip. One other shop in the state doesn’t do it anymore, and the third had their gear out for repair and didn’t know when it would be back. So I decided to have it done in Texas before the race.

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Long story short: Tess’s prop wasn’t too badly out of balance. The Terrell mechanic and I would jump into the plane, throttle up to high RPM for ten seconds or so and take measurements on a hand-held computer. Then we’d shut down, and he’d review the readings and add some small weights to the back of the spinner. Then we’d fire back up and do it all over again.

One of the times, the engine hesitated for a moment, but quickly recovered.

In the end, he tweaked the prop balance to near perfection, but he said it was close enough in the first place that it was unlikely I’d notice any difference. So what’s up with the attitude indictor? I guess Tess just doesn’t want me to know her attitude.

I had hoped to run my handicap validation flight for the race after the prop was balanced, but the clouds are too low. It needs to be done at a density altitude of 6,000 feet. Back home, this time of year, that would be about a thousand feet underground. Here in central Texas, it’s about 4,000 feet up, but the clouds are heavy at 2K.

So instead, I ended up doing what aviation people do when they have a few minutes to spare. I hung around the hangar and shot the breeze with the mechanic. In talking about the trip over, the weird throttle thing came up, and the mechanic mentioned that he thought the engine’s hesitation during our testing was unusual, but as I didn’t react, he figured it was a normal thing for Tess. I conceded that I didn’t know what was normal in this plane anymore, but asked if he’d be willing to take a quick look at the throttle before they put Tess to bed for the night. I’d also been having some issues keeping her at a set idle speed since the throttle quad was removed to work on the trim during the last round of repairs, and I thought maybe it was slipping a little or something.

He promised he would.

A couple of hours later, as I was heading down the third-floor hallway of the Holiday Inn Express & Suites to go out to dinner, my phone rang. It was from some town in Texas I’d never heard of so, I assumed it was the latest gambit from those pesky folks at the Resort Rewards Center, or the pesky folks trying to sell me an extended warranty on a car I don’t own anymore, or the pesky folks that can help me with the student loan I don’t have. I almost didn’t answer it. But at the last minute I did. It was the lady who ran the shop.

“Hey, William,” she said casually, as if asking me how the weather was at the hotel, “you don’t happen to travel with a spare throttle cable, do you?’

Next time on Plane Tales: For want of a nail…

 

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.

 

Weighty options

I let go of the yoke. One heart beat… Two heart beats…

The horizon rises in the windshield. Slowly at first, then faster. Up. Up. Up. Faster and faster still. The whisper of the wind turns into a roar. Then a howl. Twin tails rising high into the air, Tess nose-dives toward the earth like a Stuka dive bomber.

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The wind resistance tugs at the prop, red-lining the tachometer.  The vertical speed indictor shows 800 feet per minute down… 900 feet per minute… 1,000 feet… 1,200… The airspeed indictor snaps to the yellow line. I lose my nerve. My hand back on the yoke, I pull back. Gently. Firmly. The horizon, now above my head, slowly slides across the roof of the canopy, down the windshield, below the nose. We are straight and level again.

I turn to Lisa, who’s sitting calmly in the right seat, pencil poised over her knee board. “Well,” I say, “that wasn’t encouraging.” Clearly the new trim is not working right.

So much for a trouble-free return to service.

We return to the field, land, and my mechanics make an adjustment. Back to the designated practice area. Back up to 8,500 feet. Again, the Stuka dive.

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We return to the field a second time, land, and my mechanics make another adjustment. Back to the designated practice area. Back up to 8,500 feet. Again, the Stuka dive.

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On the third try, we’ve run out of trim. It’s deployed 45 degrees into the slipstream, and still the elevator can’t hold the plane in level hands-off flight. Something is seriously amiss. Tessie has become mysteriously nose-heavy. Like our engine mystery of two summers ago, there’s no satisfactory and satisfying answer as to why this is so. But cause aside, we need a solution. And one solution to a nose-heavy airplane is to simply add some weight to the other end. And as the tail is much farther behind the center of gravity—that magic balancing point an aircraft in flight rests on and rotates around—than the nose is forward of the center of gravity, a little weight should go a long way.

Or so we thought.

Funny how many of the things we think  should work simply don’t with this stubborn little airplane.

I won’t bore you with all the details of the testing plan. Or with the details of the flights, one after another, after another, after another, after another. For most of a day. But we started by securing one-pound bags of “Sea Pearls” in Tessie’s tail. The bags are designed for scuba diver belts. They are small, flat, full of tiny lead shot, and surprisingly heavy for their size.

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Based on the weight and balance sheets, it shouldn’t have taken too many bags to get Tessie to fly right. The weights were placed 180 inches behind Tess’s center of gravity. One hundred and eighty inches is a loooooong lever with which to raise the nose. Or so we all thought.

But it was not the case. Seventy-five dollars’ worth of Sea Pearls later, I still had a plane the Luftwaffe would have been proud to deploy. With the maximum amount of added weight that my maintenance team felt was safe, we still couldn’t fly level. Oh, sure. It was better. The dives were slower. Less aggressive with each bag of Sea Pearls. But anything like level flight with neutral trim eluded us.

It was time for Plan B. Which was four washers installed along the bolts that secure Tess’s tail to her fuselage. Yep. We shimmed her tail. Then I went up to test fly.

No more Stuka.

But were the weights still needed? There was only one way to find out. Take some out, test fly, and see how many, if any, were needed with the shimming of the tail feathers. Again, I won’t bore you with the details of the flights. One after another, after another, after…

But in end, there were no Sea Pearls in Tessie’s tail and she flew true.

In fact, she’s never flown better.

Now, if we can just figure out why her brand-new attitude indictor is spinning like a top, and why her compass points the wrong way…