Restoring the A-10D Mitchell Wing
SN# 275
By
Episode IV
“The Engine and Fuel System Follies”
Serial #275 came equipped with an electric start, Rotax 277, single cylinder engine turning a belted propeller reduction drive by Hegar. And while the v-belts were slightly worn, everything appeared to be in pretty good shape except for a patina of mild aluminum corrosion on the engine. No big deal. The previous owner indicated that he had put only 36 hours on the engine after the owner before him had had it completely rebuilt. So, theoretically, everything inside should be in decent shape as well. After all, it did start and run as expected before I bought it. Still, I was wary, based on the discovery of all the other things wrong with items I thought were good. So, after a quick search on the Internet for Rotax repair sites, I decided to have it disassembled and inspected by a pro. I chose Olenik Aviation to do the job after talking to Tom Olenik a number of times on the phone. Tom is a perfectionist when it comes to engines. I liked that. His website provided a great deal of advice on making a crate and packing the engine inside. All of it was extremely valuable.
The first step was to remove the belt drive and the electric starter to reduce the shipping weight and the labor costs at the other end. In the process I demonstrated consummate stupidity by ruining the PTO pulley with a rented gear puller. After carefully labeling all the assorted drive and starter parts, I packed the engine in it’s new wooden crate and shipped it off to Ohio by FEDEX Ground. While it was in transit I searched the paperwork and manuals that came with the A-10 to see if any of it applied to the reduction drive. Fortune smiled and I found a stained, two-page instruction sheet along with a phone number for the company. A call to Hegar brought a very patient male voice on the phone that explained they had stopped making the reduction unit a very long time ago, and that they no longer had any spare parts. Then there was a pause. “You know what?” it said. “There’s a box of old stuff in my closet. Let me just drag it out and check.” The sounds of a door opening and of metallic objects being jostled in a cardboard container followed. Then came a small note of surprise followed by: “Hey, I think I’ve got one for a 277, but it’s a bit smaller in diameter than the one you had. Shouldn’t be a problem though, just slightly higher reduction ratio.” The gods had smiled. I was back in business.
The fuel system was next, and the primary item to find was a replacement tank for the Rubbermaid special that was now lying dormant on the hanger floor. The original A-10s came with a tiny 2.5-gallon plastic fuel tank that nestled between the frame tubes ahead of the control stick. Even with the economical Rotax 277, however, this provided limited flight time, but worked well for a motor glider. My A-10 was unique. Sometime in the mid 1980s the company redesigned the control system to use Teleflex cables instead of the torque tubes and push rods of the earlier models. This left the back of the seat and the podsterior nearly vacant. It was an ideal place to install a larger fuel tank. I needed to find an affordable 5-gallon tank that would fit into this space along with an electric fuel pump. Being a “belt and suspenders” kind of guy when it comes to fuel systems I had decided to back up the Mikuni pulse operated fuel pump as a safety measure. There’s nothing worse than hearing the engine sputter after take-off and you haven’t cleared the tree line at the end of the runway. So, the search began.
The first effort resulted in a custom fiberglass tank of 4.5 gallons from Air-Tech in Louisiana. It was a damn nice tank; unfortunately the custom fuel filler I’d requested, and the tank’s geometry didn’t work with the podsterior. After much soul searching I made the decision to leave the podsterior on the ground and go with the Aero-Tech standard tank of the same size with built-in fuel filler and cap. The order was made and the custom tank ended up back in its box (Who knows, it might be an interesting addition to the riding lawn mower.). And, as it has happened so often, within a few days I found a better solution. While cruising the Internet for information on another subject, I discovered a company in California called JAZ Products that makes fuel cells for racing cars and dragsters. Their on-line catalog was a revelation on the art of containing fuel. My first thought was to use one of their lightweight 5-gallon dragster fuel cells because it had a very narrow profile that might fit inside the podsterior. I needed to see one, however, before committing another $100.00 bill. Surprisingly, there was a racecar supply shop in RI on their dealer list. Driving directions in hand I saddled up the old Subaru and found them hidden in an industrial park west of Providence. The fuel cell model I was interested in turned out to be a special order, but it made no difference. While in the shop, a stack of multi-colored 5-gallon JAZ fuel jugs caught my eye. Normally used to carry extra fuel, they were rugged and designed with a wide mouth for rapid refueling operations. Their profile was exactly what I was looking for. And at $25.00 each, the price fit my wallet nicely.
Over the next few days I designed and fabricated a back-of-the-seat mount for the jug that would also accommodate the new electric fuel pump. Digging through my stack of new components I pulled out the capacitance fuel gauge probe and installed it with the aid of my RotoZip tool. Instead of using a leaky rubber fuel grommet I installed two, aluminum, LEAF fuel access ports with o-ring seals normally used in custom aluminum tanks. One would be the drain, the other the fuel outlet. Searching my pile of new parts again, I located a fuel shutoff valve with dual outlet ports and a spring loaded drain valve. It looked very good and fit the space as planned.
Before mounting the tank, however, I had to deal with the new seat cover that appeared from the local upholstery shop. With the podsterior gone, the rounded top of the padded seat cover had nothing to snap to. After some study of the situation I decided to make a false seat back that would extend above the normal seat. The new seat top could be snapped to the false headrest. It was cut from some aluminum plate originally destined to be the instrument panel. Making the “headrest” proved to be considerably more challenging than expected. After a marathon cutting, bending and swearing session, it finally took the form needed and the new snaps were installed. The false seat back was then pop riveted to the original seat back taking care to make sure the height was correct to prevent stress on the new vinyl seat bottom. Once in place, the fuel tank was secured to the seat back with a nylon strap that once kept a suitcase closed.
The Facett electric fuel pump came next. It nestled neatly below the fuel tank, mounted on two vibration-isolating mounts. Blue, alcohol resistant fuel line made its appearance and was installed along with two, glass, fuel filters with replaceable elements. One of the filters went into the line leading to the Mikuni diaphragm fuel pump. The other went into the line feeding the electric pump and the hand-operated primer pump. Mounting the primer along with the choke lever, the starter and other switches was the next problem.
There was very little space available on the planned instrument panel, so mounting them there was out of the question. This was confirmed when I sat in the seat for an ergonomics check and discovered that reaching the panel while strapped in would be difficult. I needed more real estate within easy reach. The answer turned up while surfing through the Titan Aircraft website in the form of “side panels”. A few minutes search through the scrap aluminum pile produced the suitable materials and some rubber cushioned clamps. A few days later I had created two usable side panels. The larger one held the starter switch, the primer pump and the choke lever. It was placed on the right side of the cockpit attached to the diagonal tube. The arrangement was worked out by sitting in the pilot’s seat and going through the motions involved in starting the engine. Placing the tall primer pump handle in the center prevented a careless elbow from unwanted activation of the other two controls. The remaining three switches for ignition, electrical system main and the fuel pump were put on a small piece of angle aluminum that clamped to the left down tube. This one, hopefully, would end up inside the pod.
The engine is a story in itself. Shortly after it’s arrival in his shop, Tom Olenik had it torn down to the component level and analyzed the interior. His best guess was that it hadn’t been touched in something over 500 hours and had some serious piston issues. The crankshaft and its bearings, however, were still in good shape. When it returned two weeks later there was a new piston assembly in place along with a number of other small parts necessary for proper function. And I was in the hole another $600.00. The hole got deeper when I noted that J-Bird in Wisconsin had a brand new, still in the box, Rotax 277 for sale, and I bought it. Both engines were now sitting in my garage waiting to see which would get the call.
The engine mounting plate, however, went to the bench first for installation of the new Lord anti-vibration mounts. The old 3/16” pop-rivets were drilled out and new mounts put in place with stainless steel rivets. To support this effort I had bought a “heavy-duty”, long handled rivet tool from my old standby for cheap tools, Harbor Freight. The jaws broke after four rivets and I resorted to struggling with a smaller hand tool while its long-handled, heavy duty cousin went parcel post back to California.
The engine plate went back on the frame with fair ease along with new saddles and large AN-4 washers. Then, after rounding up some mounting bolts, I pulled the shiny new Rotax from its box and lifted it into place. The plan was to temporarily mount the engine to allow me to design and build new mounting systems for the exhaust and the new intake silencer. But fate, as always in this effort, had another plan.
Rummaging through my boxes of parts I managed to locate the new intake and exhaust manifolds along with some gaskets and bolts. Moving to the right side of the airframe I held the exhaust manifold up to the port and was shocked to find that it didn’t fit. I re-checked the LEAF catalog and California Power Systems Catalog assuming I’d somehow gotten the wrong part. Nope, it was the correct manifold. Disconcerted, I picked up the intake manifold and held up to the port on the left side. It didn’t fit either. What the @^#%@$?
It was then that the revelation hit me. The exhaust and intake ports were reversed! It appeared that the factory had assembled the engine with the cylinder on backward! Just when I had come to believe that a Rotax was a Rotax, my world view had been drastically altered. But how could this be? To find out I made some panic phone calls to several Rotax repair facilities only to get disbelieving silence at the other end. Maybe I wasn’t alone after all. The question now was what to do about it. Some additional research revealed that Rotax only made one cylinder for the 277 engine. Apparently the bolt pattern was symmetrical and assembling the engine with cylinder “backward” was indeed possible. Why they did it on this one remains a mystery. My best guess is that it was done purposely to accommodate a specific application.
An e-mail to Olenik Aviation brought a response that revealed surprise and no little skepticism at the situation. After some coaxing, however, Tom agreed to disassemble the engine and return it to its “stock” configuration. I also commissioned him to do a thorough inspection of the interior to make sure that there were no other little abnormalities that might ruin my day. And so, the original, now rebuilt, 277 came out the crate and in went the new one. Then off again, by FEDEX Ground, it went to Ohio.
While that was underway I mounted the old, rebuilt engine and set to work on the exhaust system. The original mounting system was a simple affair. It relied mostly on the exhaust springs and a homemade steel bracket that secured the end of the canister pipe to the diagonal engine support tube. This was cushioned, sort of, through a short piece of folded radiator hose. I wasn’t enthusiastic about this system. Although functional, it caused the entire exhaust system to vibrate badly and coupled this vibration directly to the pilot’s cage. After some brainstorming, I came up with a bracket design that secured the muffler canister to the engine mounting plate. Employing some additional vibration isolation it allowed the exhaust system to move with the engine, preventing the wear that was already starting to become apparent on the exhaust elbow. I called California Power Systems and put in an order for the parts they used for their own exhaust mounts. Their catalog was a real boon in that it listed all the part numbers for their 447/503 exhaust mounting kit. While this was in process I bought some 1 ½” steel angle at the local hardware and fashioned the brackets. I also mounted the prop reduction drive on the engine along with the old, two-blade Ultra-Prop. Then I stood back with a bit of awe. This thing was starting to look like an airplane! Damn. If only I hadn’t mounted the prop on the hub facing in the wrong direction… Oh well, it was only a preliminary fitting. Whose gonna know?
When the parts arrived I assembled and temporarily installed the mount to see to try and detect any other glitches that would plague me later. Strangely, everything fit. The only problem was that the exhaust canister outlet was now positioned to release exhaust gases straight up onto the bottom of the wing. It should be noted here that the canister outlet was a custom unit installed by a previous owner to deflect the exhaust away from the prop, eliminating the black, oily smudge on the blades. At this point I pulled out the Rotax after-muffler kit I’d purchased some weeks earlier and checked the fit. If there was welding to be done, I figured to have it all done at once. Bad news, the 180-degree outlet bend in the kit ended up far enough aft to interfere with the prop. The kit went back to LEAF the following day for a refund. I also stumbled across a small black business card I’d stuffed in my desk for a local machine shop / welding service. Taken off the wall at the local pizza parlor it had been put aside for later investigation. Later was now.
I made the call and discovered that the shop was only about half a mile from my house. It was a one-man operation run by a former tool and die maker who’d gone out on his own after the aerospace company he worked for in Massachusetts moved its manufacturing operations to Mexico. That evening, I met “Roger”, the owner, at his house and showed him what I wanted done to the exhaust canister. “Weird looking motorcycle you’ve got”, he said, turning the canister in his hands. I explained it was from my Ultralight, which piqued his curiosity considerably. “No shit? You actually fly one of those things?” A short time later we walked to a massive steel building hidden in the woods behind his house and I got the Cook’s Tour of his remarkably well-equipped machine shop. I asked how long it would take to cut off the old outlet, fabricate a new one and weld it in place. “Oh, a night or two, I guess.” Seems Roger’s prime working hours were from 10PM to 5AM. He was well into being his own boss. “Gonna cost at least $20.00, though.” Smiling, I left my number.
I went back to the garage that night to tackle the design of the mounting brackets for the intake silencer. The silencer is a large, oddly shaped plastic chamber that slips over the carburetor, taking the place of the original air filter. It does the bulk of the work in quieting a two-cycle engine by trapping the pressure waves that are reflected back out through the intake manifold. The result is a hefty reduction in the grating metallic roar unique to the two-cycle combustion process. Combined with a shallow pitch three-blade prop, #275 would be able to tip-toe through the local skies with no more than a whisper. Definitely an asset when reconnoitering the local nude beach, it was also more in tune with my sensibilities as a glider pilot. Then, too, I’d received a healthy injection of respect for noise abatement from Flight Star’s Tom Pegheny while taking Ultralight flight instruction from him at Ellington, CT. Tom was constantly diverting us over frontier areas to avoid disturbing the local population. He made it clear that all of us are “good-will ambassadors” for the Ultralight Community and thus have the responsibility to fly as though our Part 103 freedoms depend on it. And, in reality, they do. As he pointed out, while the average ground-dweller can’t tell Cessna from Piper, the uniqueness of our aircraft make it easy to register complaints about “that god-damn flying chainsaw!” Thus were the origins of my commitment to silence here in the up-tight, Yuppie Northeast.
Now that the prop was installed (more or less), and the old, broken carburetor had been temporarily put back in place, it was easy to determine that the intake silencer, if oriented improperly, would end up within the prop-disk. Not a good thing. So, after some twisting and turning, I finally settled on placing the chamber above the carburetor, inclined about 45 degrees, with the air filter facing forward. Of course, the mounting holes in the chamber lined up with nothing, but at least the damn thing fit. Although it seemed secure, I managed to resist the temptation to do the installation without any mounting brackets. I’d already been warned that having one of these things peel off and go through the prop was less than a pleasant experience. I just had to figure out how to do it and what to use.
At first, I toyed with aluminum flat stock but abandoned the idea after noting the weird bends that would be required and fearing wind induced vibration from the tiny, exposed “flying surfaces”. I finally settled on some lengths of ¼” OD, thick-walled aluminum tubing that I’d bought at a local hardware store. After cutting some experimental lengths I began bending them with my trusty, Harbor Freight tubing bender until they bridged the gap between the engine mounting plate and the mounting holes in the plastic chamber. Pop-riveting short pieces of flat stock and angle to the notched ends of the tubes completed the design. The silencer was now held rigidly in place with the addition of three AN-4 bolts. Nevertheless, I decided to have the end pieces professionally welded to the tubing. But who would consider doing such a small and delicate job? The next evening found me back at Roger’s Machine Shop explaining what I wanted done to the bizarrely shaped pieces of metal. Three days later I had them back along with the altered exhaust canister, all for the princely sum of $35.00. The fit was beautiful.
My next move was to cut and temporarily install the throttle and choke cables using tie wraps. After this came the remainder of the fuel system plumbing. The problem here was where and how to mount the Mikuni fuel pump. And, now that I had two fuel pumps, there was an adjustable pressure regulator to deal with. It took a bit of thought and a lot of trial fittings but I was able to secure the Mikuni to the upper left engine mounting strut with a padded aluminum clamp and an AN-4 bolt. A quick measurement of the length of pulse line required to attach it to the engine revealed that it was considerably less than the maximum length of 18 inches. The pressure regulator ended up on a pad of pipe insulation, secured to the left diagonal with nylon tie-wraps. It was placed, or rather hidden, behind the intake silencer to keep inquisitive hands from readjusting it while at fly-in’s.
The electrical system was next item to be attacked, starting with the ignition transformer. The transformer that came with the A-10 had been installed in a Radio Shack aluminum project box that was bolted to the top of the engine mounting plate. I had tacitly assumed that a former owner had done this to quiet RF noise that was interfering with his handheld VHF radio. But, as always, I was wrong. My original intention was to reinstall the transformer on the three studs molded into the engine housing just for that purpose. If the noise proved bothersome I could revert back to the aluminum box idea at a later date. Fate, of course, had a different notion.
Rummaging through the old engine parts I located the original ignition box and opened it to remove the transformer. The box itself was badly corroded and was not exactly a work of art where the openings had been cut, or rather hacked, into the bottom. I marveled that the rough edges had not frayed or cut any of the wires connecting back to the engine. Inside, the transformer had been cleverly secured to the box using nylon tie-wraps through holes in the side of the box. The transformer rested on a piece of old rubber fuel hose held in place by even smaller tie-wraps. I removed the transformer with a few snips of the diagonal cutters and marched straight to the engine to see how it would fit.
It didn’t. After attempting to line up the transformer with the mounting holes it was obvious that the airframe diagonal tube blocked the installation. I was amazed and once again frustrated. And, as always in these circumstances, I retired to the VCR, wine glass in hand, to watch relevant sections of the A-10 assembly video. Damn! There were differences in the 277 mounting scheme between #275 and the plane in the video. Okay, now I understand the reason for the box. Where’s the nearest Radio Shack?
The new box was an exact duplicate of the old one. Unfortunately, it no longer fit into the space it formerly occupied because the intake silencer mounting brackets were now in one corner. Okay, the puzzle begins again. A few trials later, the box, or at least most of it, had found a home on top of the engine mounting plate with the sparkplug wire and magneto wires dropping down through one of the plate’s lightening holes. Now to remount the ignition transformer in the box. For this I reused the short piece of rubber fuel line as a cushion and a pair of #10 steel bolts through two of the transformer’s mounting holes. The bolts went through two standoffs made from thick-walled aluminum tubing with a 3/16” ID to position the transformer. The locknuts and washers that hold everything in place are on the bottom of the box on the end that hangs in free space.
The question now was whether to replace the sparkplug wire and cap. The original was shielded and appeared to be serviceable but the cap was of an older design. I opted to replace everything. After nearly twenty years of being jolted by tens of thousands of volts, insulation tends to breakdown and new components weren’t that expensive. The next day an order went out to California Power Systems for new wire, a metal-shielded resistance cap and a length of woven copper shielding.
While waiting for CPS box to arrive in the mail, the electrical system installation continued with a visit to the local NAPA Auto Parts store. Here, I scored a length of flexible plastic conduit and some crimp-on wire terminals. I also raided their wire stocks, coming away with multiple rolls of colored wire in various sizes. Back in the garage I counted the number of wires required between the engine and the cockpit, selected some clashing color schemes and then cut generous lengths which I proceeded to stuff into the conduit. Next came the EGT and CHT sensor lines and Viola! I now had a cable. This was then installed in one long length along the left diagonal and held in place temporarily with the now ubiquitous nylon tie-wraps. I left the bulk of the unused cable coiled in the pilot’s seat, ensuring that I had enough to reach the planned instrument panel and the small side panel. Quick-disconnect barrel terminals, male and female, were then installed to connect the magneto lighting coils, ground and kill wires into the cable. Just behind the seat the wires from the fuel gauge and the electric fuel pump were pushed into the conduit through the slit in its sidewall their nether ends in the cockpit. Damn. This thing was starting to look professional.
Tom Olenik was able to turn the new Rotax 277 around (literally) in less than a week. He confirmed the “new” status of the engine and upgraded the piston wrist bearing retention scheme. The only kinks were some minor damage to one of the cooling fins on the cylinder head and the loss of the ignition transformer, both damaged in transit to Ohio. I made a mental note to develop a scheme to pack the engine in FEDEX-Proof concrete for the next trip. Olenik was not amused.
Now for something completely different. We’ll pick up the restoration again in Episode VI. In the meantime, the next installment will deal with Mitchell Wing transitional flight training in Kansas.
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