August 1, 1998
MARC E. COOK
When I saw him again on that May afternoon, Mike Pavao was walking unsteadily across the farmer's field with blood on his shirt, swearing.
A few minutes before, it had become obvious that the improbable, the unthinkable, had happened. Our fastidiously restored Timeless Tri-Pacer, having sailed through its first flight with only the most picayune of squawks, had come to rest not on Clarksburg, California's turf strip but in a plowed field adjacent to the approach end of the runway.
"It just quit," said Pavao about the engine, trudging through the field. "No warning, nothing." When it lost power, the Tri-Pacer was just beyond gliding range of the end of the runway. Complicating matters is the fact that landing short at Clarksburg is not an option thanks to swampy land along the western perimeter. Realizing the short-wing Piper wasn't going to make the runway, Pavao turned it into the southerly wind and did his best with a rough, recently plowed field. It came to rest, upside down, balanced between the crumpled cowling and windshield header. Five months of work rendered moot, just like that. Spirits in the close-knit Clarksburg Air Repair shop sank.
As we gathered our wits and let the shock subside, the Tri-Pacer's tremendous strength became obvious. Most important, Mike was unhurt save for cuts on his nose. As for the airplane, the engine mount and nosewheel structure were no longer as one, and the firewall-forward sheet metal was junk, but the rest appeared almost undamaged. In fact, aside from the tip of the rudder, which contacted the ground and bent the upper tube, the entire fuselage was unscathed.
Early the next morning, six of us wrested the airplane from the field, removed the wings, and loaded the PA-22 onto a flatbed trailer for the short ride back to the airport. Our most pressing tasks were to determine the extent of the damage and to uncover the reason for the engine stoppage.
We were genuinely amazed to find the first issue concluded within the hour. All of the cowling pieces would require replacement, as would the engine mount and nosewheel structure. Both wings would have to be uncovered, inspected, and given minor repairs. Both struts supporting the right wing failed in compression and would have to be replaced. That's all. In the immediate aftermath, when it had become clear that our course of action would be to rebuild, not replace N198TP, we all agreed that the Tri-Pacer's bulldog stature had made the difference — had this been a conventional sheet-metal airplane, we'd have been facing replacement.
Determining why the engine quit was not so simple. Quickly, we ruled out an engine catastrophe. All cylinders had excellent compression, all the valves worked. Both new Slick magnetos worked flawlessly on the test bench, and there was no evidence of airbox or air-filter blockage. Pavao, who owns a Cessna 140 — one of the most carb-ice-prone airplanes around — is religious about using carb heat, so carb icing was ruled out.
Focus then turned to the Tri-Pacer's fuel system. Pavao flew on the right tank after I had made most of the 45-minute first flight on the left; his flight was less than 15 minutes long. Circuitous plumbing of the right tank — the line from the aft port comes down behind the front door, runs along the floor, and then travels back up to the instrument panel where it tees with the line from the front port — necessitates a placard warning pilots to use the right tank in level flight only when it's less than one-third full. Our calculations indicated there should have been about eight gallons — more than a third — in that tank. Still, we kept in mind that the right tank could have failed to feed the engine.
Next, our attention turned to the carburetor. Precision Airmotive provided us with a new MA4 carburetor for the project. When it was installed all of the fuel lines were flow-checked and both tanks drained to remove any debris. None was found. After the accident, we found fuel in all of the lines, from both the left and right tanks, as well as in the line from the gascolator to the carburetor. The carb float bowl was empty, which is not surprising since the airplane sat inverted overnight. The local FAA investigator had the carb sent back to Precision for testing, where it received a clean bill of health.
For good measure, Clarksburg Air Repair's Steve Wilkie disassembled and carefully inspected it as well, finding nothing amiss. A possibility — supported by a goodly number of service difficulty reports on the subject — is that the float stuck with the fuel-inlet valve open, raising the level of fuel in the float and flooding the engine. This theory is consistent with Pavao's report of the engine coughing while the throttle was pumped during the last part of the fateful descent. But there is no material evidence to prove this theory.
In fact, we don't at press time know exactly why the engine quit. But, as you read this, a comprehensive flight-test profile will have been flown to help determine if the flow from the right tank can become critical at fuel levels greater than one-third during certain maneuvers, or if there are some other flow anomalies. We are also evaluating changing the standard fuel system. Frank Sperandeo was granted a field approval for changes to the right-tank plumbing that resulted in substantial increases in fuel flow. His modification changes the routing of the aft pickup lines to eliminate some bends and the need for the fuel to climb as far before reaching the fuel selector (Form 337 drawings are available from the Short Wing Piper Club; contact the club on the Web at www.shortwing.com).
In the meantime, repairs on the airplane have progressed with eye-opening speed. Clarksburg's crew put on a full-court press to ready the airplane for Oshkosh, pushing aside other business, weekends off, and evenings home with the kids. By far the biggest portion of the job has been to rework the wings, because the covering had to be removed entirely and every component carefully inspected. It has been on the minds of Wilkie, Renner Brewer, Mark Keema, Scott Monroe, and the rest of the Clarksburg staff that the airplane has to be in as good a shape as before the incident.
As previously planned, the Tri-Pacer's next stop is in Santa Maria, California, for installation of the avionics and instruments. There it will be joined by the interior furnishings and final prep for Oshkosh. With a bit of luck and good flight-test weather, we'll have the Timeless Tri-Pacer there for you to see — in the flesh and, true to its plucky nature, none the worse for wear.
E-mail the author at firstname.lastname@example.org.
Carburetor and starter Precision Airmotive 3220 100th Street, Southwest, #E Everette, Washington 98204 Telephone 425/355-6400 www.precisionaviation.com
Millennium cylinder assemblies Superior Air Parts 14280 Gillis Road Dallas, Texas 75244 Telephone 610/366-8937 www.superair.com
Slick magnetos and harness, SlickStart spark booster system Unison Industries 530 Blackhawk Park Avenue Rockford, Illinois 61104 Telephone 815/965-4700 www.unisonindustries.com
Of the myriad roads to follow at overhaul time, a few are well trodden. While sales of factory-new engines — every piece is literally brand-new — are comparatively slow in the aftermarket, both Continental and Lycoming have pushed hard to fill the overhaul market as original-equipment contracts have become slim pickings.
Lycoming offers both factory remanufactured and overhauled engines. Remanufactured engines have essentially all-new parts but may use some major overhauled components such as cases, crankshaft, and accessory gears. Lycoming builds remans with new cylinders, pistons, camshafts, and ancillaries like the oil pump. With the Lycoming overhaul, you may end up with more used, overhauled parts — reflected in the lower cost of the overhaul — but you may not. Depending upon availability of cores, you might get lucky and find your engine to have many new components; it's just the luck of the draw.
Lycoming currently offers both remanufactured and overhauled O-320-B2Bs, as found in our Timeless Tri-Pacer. In the past sweepstakes airplanes, we have used factory remans with good success. Such a route produces no unseemly surprises — like the overhauler's call to say your crank is bad and your camshaft is shot, so expect to spend a few thousand more than you had planned. By returning the core in toto, you have the opportunity to make cracked jugs, ground-down cam lobes, and obsolete oil pumps somebody else's problem. Another advantage of the factory route is time: You can arrange to have your refurbished engine arrive soon after the old one has come off the firewall.
We, however, had time. Because we knew the Tri-Pacer's airframe restoration would take several months, the time was available to do the engine locally. Quite locally, in fact; Loren "Smitty" Schmidt assembles all of Clarksburg Air Repair's engines — he's been an engine man for more than 30 years. In addition to Schmidt's hard-won expertise, the Clarksburg facility has gained much of the high-tech tooling and testing equipment that was part of the Sacramento Sky Ranch overhaul shop, run by the hyper-knowledgeable John Schwaner.
Moreover, we felt that a field overhaul would give us much the same experience as many Tri-Pacer owners endure at TBO. Let's face it: You don't often plop down $13,000 for a factory-remanufactured engine when many Tri-Pacers aren't worth twice that — including the airframe. A basic overhaul from Clarksburg, reusing your cylinders, runs about $8,000 on something like an O-320, figuring on about $4,500 in basic labor and the rest for parts.
Deciding to go with a smaller shop for overhaul should include some homework. Ask for a list of recent overhaul customers and randomly pick two or three to contact — be wary of cherry-picked candidates supplied by the overhauler. Look around the shop. It should be reasonably clean and tidy, but remember also that we're not talking about open-heart surgery — an engine builder with grease under his fingernails is not a bad thing. Compare warranty coverage. Clarksburg, for example, covers parts and labor for nine months or 200 hours (prorated at 30 hours a month) and parts only to 600 hours on nongeared engines. Many of the factory warranties are better, but you have one advantage in dealing with a good, small shop: Face-to-face contact with the people who can make decisions about warranty claims.
Even though we decided against having an all-new engine, we did opt for all-new parts where they made sense and had the overhaul performed to new-limits specifications. (These are the clearances and dimensions that are used in new engines. Service limits — to which many overhauls are performed — are much more generous and, ultimately, make a low-buck overhaul false economy.) In fact, about all that's left of the original O-320-B in our Tri-Pacer is the crankshaft and cases.
Lycoming chipped in with a raft of new parts, including camshaft, tappets, accessory gears, bearings, and seals. Inside our sub-1,000-hour engine we found a cam lobe about half eaten (with a correspondingly chewed-up tappet) and a now-obsolete oil pump. (Lycoming has tried varying combinations of materials in the pump gears since our engine was built in the 1970s.) Otherwise, though, the engine was clean and in good shape; the crankshaft, once inspected, was put back into the engine with a minor polish job.
Sometimes you discover that the march of progress at the engine manufacturer has left you behind. We ordered a new cam for the O-320, as anyone overhauling a Lycoming ought to do, but discovered when the parts arrived that the new cam is built with the drive gear integral to the shaft; the old had a bolt-up gear. Not a big deal, but we then needed to order a similarly late-spec accessory case, tach drive, and various other seals to make everything fit. Again, not a deal-killer — particularly since the new cam-drive setup is probably less prone to failure — but unexpected. Beyond that, our little four-banger went together quickly. The O-320 is a familiar engine, well-understood by overhaulers, and easy to get parts for.
Lycoming has been aggressively pushing new cylinders for overhauled engines on the theory that many of the jugs are simply worn out from too many thermal cycles, too many overhauls and weld-repairs, and just old age. Superior Air Parts has also capitalized on the recent demand for new cylinders by producing the Millennium series. Though we have experience with these investment-cast cylinders on our corporate Beech A36's IO-550 Continental, we haven't much with the versions for the parallel-valve Lycoming.
Superior supplied us with a set for the O-320, in the original narrow-deck configuration — Lycomings come with either thin mount flanges with reinforcing plates (narrow deck) or thick flanges (wide deck). Upon first seeing the new cylinders, it's easy to be amazed at the smoothness and consistency of the castings. On its maiden flight, the Tri-Pacer showed far more vigor than before, easily climbing out at light weights to the tune of 1,000 fpm. The engine was also noticeably smoother than before, partly the result of new engine mounts.
In addition to the engine essentials, we replaced both magnetos with new Slicks and fitted the Unison SlickStart system; this is basically like the old "shower of sparks" system that uses battery voltage to help boost spark strength during starting. We managed only a handful of starts in mild weather before the mishap, so we'll report later on how well this system works in colder and hotter weather.
Other accessories were either overhauled or replaced with new. As mentioned, the carburetor is a new Precision Airmotive unit, and we also used Precision's new Lamar lightweight starter. The alternator was a recent addition to the Tri-Pacer before we bought it, so it received little more than a new belt and some tidying of the wiring.
As we gain more experience with this package of accessories, we'll let you know how it all works. For now, the signs are promising that our conservative overhaul and replacement policy will provide a durable powerplant, building on the sterling reputation of the O-320 itself.
After an airplane gets bent — as with our Timeless Tri-Pacer — one of the first questions to arise is: Do we have to call the feds? The answer most often is, surprisingly, no.
In cases of aircraft accidents, the FAA is not the controlling agency, the National Transportation Safety Board is. And, according to NTSB Part 830, you are required to report aircraft accidents and some incidents expeditiously. Accidents can take place only between the time persons board an aircraft with the intention to fly (making the rule stick in case the aircraft never actually flew) and the time they disembark, and must involve death or serious injury or result in substantial damage to the aircraft. A full listing of the Part 830 requirements is available on the AOPA Web site.
Serious injury, by the NTSB definition, involves broken bones (aside from simple fractures of the toes, fingers, or nose); hospitalization for more than 48 hours within seven days of the accident; or second- or third-degree burns over more than five percent of the body.
Substantial damage adversely affects the structural strength, performance, or flight characteristics of the aircraft, and would normally require major repair or replacement of components. Substantial damage is not failure or damage of one engine; bent fairings or cowlings; dented skin; ground damage to the propeller; or damage to the landing gear, wheels, brakes, tires, flaps, engine accessories, or wing tips. Generally, then, a gear-up landing is not considered substantial damage.
If your mishap does not involve substantial damage or serious bodily injury, you don't have to report anything to the FAA or NTSB. But you should, as soon as possible, get on the phone to your insurance company to get the ball rolling on repairs. — MEC
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