Premium overhauls

Oct. 1, 1998

Premium Overhauls

"New Limits" is the only way to go

By Greg Napert

October 1998

Today's reciprocating engine overhaul market is very competitive. With a wide variety of small shops offering a large variety of overhaul services, and the engine manufacturers themselves providing overhaul capabilities, it has become harder than ever to continue to provide high quality overhauls at competitive prices.

One facility that has chosen to continue to offer premium overhauls, despite these conditions, is an overhaul facility called Penn Yan Aero, located in Penn Yan, NY.

Daryl Middlebrook, president of Penn Yan Aero stresses the importance of "new limits' overhauls.

A modestly appointed, yet fully-equipped and highly organized shop, nestled in the heart of New York state's Finger Lakes, the company has been overhauling recip engines for over 50 years. Daryl Middlebrook, owner and president of Penn Yan Aero, began the operation in 1964 when he was working for his dad in the FBO operation and saw an opportunity to concentrate on overhauling engines. He invested in the tooling he needed and registered the repair station with the FAA. Since that time, Penn Yan has abandoned the FBO business and has focused solely on the overhaul business — going from overhauling six engines per year in 1964 to five engines per week in 1998. The company's focus on engine overhaul has become so strong, it no longer does installations or removals — even though it operates out of a hangar at the airport. The hangar has been completely converted to an overhaul shop and warehouse and all engines are received via land conveyance.

Penn Yan overhauls both Continental and Lycoming engines as well as repairing prop strikes, sudden stoppages, metal contamination, etc. It also supplies STCs for horsepower upgrades for various engine and aircraft installations.

There are many different types of overhaul shops in the industry. The regulations, which govern overhauls are broad enough that they allow overhaulers to do a wide variety of maintenance on a particular engine and still call it overhauled. Some shops inspect an engine and reassemble it with serviceable parts. And at the other end of the scale are shops that return the engine to "like new" tolerances with new and repaired components.

Middlebrook says that Penn Yan likes to consider itself a "premium" overhaul facility and doesn't offer anything but a "new limits" overhaul. "There are plenty of people out there selling Volkswagens and such but we want to be known as a premium overhauler that sells a quality product," he says.

Although some of the extra steps that Penn Yan takes to ensure a quality product are considered by some to be what some refer to as "blueprinting," Middlebrook says that he doesn't like that term as there is really no definition for it. Instead, he likes to think of Penn Yan as doing whatever it takes to provide the best quality of overhaul possible.

Improving on the basics
Middlebrook explains, "One of the biggest things that you can do to improve the performance of any horizontally opposed, carbureted, or fuel injected engine is to equalize fuel distribution. You will find that certain engines distribute fuel very evenly, and some other engines are poor at doing that. Also, the aircraft that the engine is installed in makes a lot of difference, even with the same engine.

"So, we spend a great deal of time porting and polishing our cylinder heads. We are very careful to dimension our ports to the same size and remove any slag or inconsistencies in the casting." He explains that a large amount of porting and polishing experience that they have gained over the years is out of necessity as they weld cracked heads. Porting and polishing is a critical step that is needed to return the head to its original condition after a welding operation.

"You've got to be careful about how much porting you do, however. There has been some very aggressive porting in the industry to increase horsepower, but you can't do so much that you change the design of the engine or that you remove too much material and cause cracking of the cylinder heads."

Middlebrook says balancing is another important step to a good overhaul. "I feel Lycoming and Continental do a good job of providing matched sets of pistons and such, but we still check every set and make sure they are within our tolerances."

He continues, "Pistons and rods are checked for balance on every engine. The crankshaft is only balanced if they have been reground and they're going out to be re-nitrided (hardened). We have to balance them prior to hardening because the balancing involves removal of material. But even then, I'm not sure how much good it does because the engine is spinning at such a slow speed."

"We've also studied what they call "CC-ing" of engines where they measure the volume of the cylinders with liquid, and we've determined that there are really no effects from this. Again, this is because of the low RPMs. The real critical thing is not necessarily balancing the air flow, but balancing the fuel distribution to the cylinders."

As far as painting engines a particular color, Middlebrook says that they don't advocate any particular color of paint on its engines. "Everyone seems to be happy with Lycoming gray or Continental gold, but every once in a while, we have someone request white or black, and as far as I'm concerned, we'll paint it pink if the customer wants. I really don't see any particular advantage to particular color except for aesthetics."

Despite the controversy in recent years over the welding of heads, Penn Yan has developed a process for welding that it continues to stand behind. Middlebrook says that cylinder head welding can be very reliable as long as you know what you're doing. "We have discovered some tricks over the years for successful welding of cylinder heads. One is to pre-heat the heads to 650ûF prior to welding, and the other is to allow the cylinder to slowly cool by placing it in an oven and reducing temperature over an extended period.

Another secret is to do thorough peening of the welded area to remove any stresses. The procedure for welding involves dye checking, grinding to the bottom of the crack, dye checking again, and once they are sure the crack is gone, they pre-heat it, weld it, peen it, and then rework it to the original shape. Our procedures result in very little warranty rework," he explains.

"That's one reason why Penn Yan warrants its engines and cylinders to two years/500 hours. That's twice the OEM cylinder warranty."


Premium Overhauls

"New Limits" is the only way to go

By Greg Napert

October 1998

Penn Yan's welding repair process begins with heating the cylinder to 650F prior to welding.

Commit to standard replacement parts
Middlebrook says another important step in a commitment to quality is to develop a standard replacement parts list for your overhauls. "We determine the complete list of parts needed for that engine and always replace those parts, despite their condition — particularly items such as the camshafts, pistons and exhaust valves that you know are high wear items that will cause problems.

"The most expensive parts that we have in the engine are valves, pistons, camshafts, and rings. So, you've got to bite the bullet and put them in every time and price your overhaul accordingly. Otherwise, you are doing yourself and your customer a disservice."

Middlebrook says the price that some overhaulers quote for an overhaul can be disturbingly low. He explains, "In addition to being an overhaul shop, we are also a parts distributor — so we get our parts at the lowest cost available to anyone except the manufacturer. All other overhaulers get their parts at the same cost as us or from us at a slightly marked up price. Yet, you see overhaulers all over the country that are charging prices that I just can't understand. Explain to me how these overhaul shops can sell overhauled engines for less money than I do when they are paying more for parts? They are either not putting in the parts that I am in the engine, or they are not putting the labor into it. In either case, the quality of the overhaul suffers and the customer gets an unsafe product.

"Outside of AD notes," says Middlebrook, "there is nothing that mandates replacement of any part or parts in the engine (with the exception of a 135 operator who is required to comply with manufacturer's service bulletins). You can technically overhaul the engine with used rings, valves, guides, gaskets, — everything, unless there is an AD note that dictates that you use a new part. Not that used parts are necessarily bad. A used part that meets new limits is fine, but, my point is there is a wide range of quality in the overhauls that you can get. The key is not whether the part is new or used, but does it meet new limits and will it last for 2,000+ hours.

Another critical step in successful cylinder welding involves peening the welded surfaces to eliminate any stresses that results from the welding process.

Besides the standard hardware and gasket items, we never send out an engine without new pistons, rings, or a new or reground camshaft (with the exception of the H2AD engine which is hard on cams and we only use new). "There is nothing in the manual that tells you that you have to do that, but, we've learned from experience that if you don't replace these items, you won't get 2,000 hours out of the engine."

You also have to have a commitment to using good quality parts in your overhaul. "Determining what constitutes a good part versus a bad part can take some experience," says Middlebrook. An example of that is piston pins. He explains, "All the good piston pins, for instance, are made by Burgess-Norton. They supply a lot of the PMAers, the OEMs, etc. And over the years, I've watched suppliers go away from using this vendor and inevitably we begin to have problems with piston pins. They seem to be the only vendor that can supply a reliable pin. So, I will not buy piston pins and put them in an engine unless my supplier can certify that they are Burgess-Norton pins. I have suppliers that won't do that, and so I won't use those suppliers. It's really not worth it to sacrifice your reputation and your future by shopping around to save a few bucks."

The argument for "Zero-time" tolerances
Middlebrook says that the company has a commitment to "zero-time" tolerances in its overhauls for a couple of reasons. First, it's the only way to offer an overhaul that will last to TBO, and second there are liability issues involved. "We want every overhaul to be as good as it can be so that we don't have to worry about liability," he says.

He continues, "If we take apart a competitor's 500- or 1,000-hour engine and the main bearings have been rattling around in the crankcase, the pistons are worn out, the piston pins are shot, and it needs a lot of work, that wasn't an engine that was overhauled to new limit tolerances. Many inexpensive overhauls are driven by salesmen who want to sell aircraft with overhauled engines and don't want to spend any money on overhauls. They will find someone to overhaul the engines as cheap as possible and will sell the aircraft with "fresh overhauls" to an unsuspecting customer. That customer will get 500 to 600 hours down the road and will start to have problems. We get to look at some of these engines and we find parts such as camshafts that are put back into the engine that must of been just barely serviceable when they were put back in the engine."

Another disadvantage of an overhaul that is not done to new specs and is that the engine will not comply with Part 135 requirements. This may not be a problem if you're operating under Part 91, but if you want to eventually sell the aircraft to a 135 operator, the engine would need to be re-overhauled and all manufacturer's service bulletins would have to be complied with." All of Penn Yan's engines can be used in either a 91 or a 135 operation.

Middlebrook says, "There are a couple of instances that we do stray from the service bulletins, such as for performing certain repairs. For instance, we weld cylinder heads and crankcases, but we do those under process specifications that have been approved by the FAA. This approval by the FAA supersedes the service bulletin that discourages welding. Most ADs and service bulletins allow you to develop alternate methods for compliance, under the condition that those methods be approved by either the manufacturer or the FAA. For example, Lycoming has a test procedure for testing engines in the back of their manual that we didn't like. So, we went to the FAA and told them we wanted to do it differently and got our procedure approved for our facility."

Camshaft questions There has been a great deal of discussion in the industry related to camshaft grinding. An incident a couple of years ago where a new camshaft "re-grinder" company provided a number of camshafts that subsequently failed, caused a bit of skepticism in the industry regarding the practice. As a result, the engine manufacturers began to discourage the practice under the presumption that the nitriding process for hardening the camshaft lobes could be compromised during the grinding process.

Middlebrook says that the industry learned from the incident with the incompetent regrinder and that camshaft grinding is still an acceptable practice in the industry.

He says, "In fact, Lycoming was grinding cams for years. We use to be able to send them to the factory to have them reground. I don't believe that that is still an option, but, there are several regrinders in the industry that have been doing it for years. I basically find that once you've found someone that can do a good job for you, it's best to stick with them. I don't feel that reground cams are a problem in the industry as the failure rate is probably about the same for reground versus new."

"Nonetheless, we see many new camshafts that fail as well. We have seen many problems with camshafts in all models of Lycoming engines because of an inherent design problem. Frankly, it was designed many years ago and it needs to be re-engineered some day. That cam sits on top of the engine and it gets no lubrication until the engine is started and even then, it gets just a splash. Then the oil drains out and if it sits for an extended period of time, it begins to corrode. This is especially a problem for engines that have high calendar time and low operating time — in other words — engines that sit for long periods of time. The only solution today is to install an electric-driven oil pump which would pump oil to the cam prior to starting the engine. If all aircraft had this, we wouldn't see any more camshaft failures.

"As an aside," he says, "cam failures don't worry me as much as some other failures. When the cam fails, it does it in a gradual manner as the cam lobes begin to wear down. You will notice this gradually as the engine loses power, and runs rough. But, it typically isn't one of those items that causes the engine to fail immediately or causes the aircraft to fall out of the sky. So, while it's a big problem out of your pocketbook, it is generally something that won't cause a catastrophe."

Crankshaft blues
Middlebrook says that it likes to guarantee the price of its overhaul for its exchange program (where the customer sends in his engine and receives an identical model, freshly overhauled, back), despite the condition of the core. However, he explains that the exchange engine must be a normal run-out engine with a repairable crankshaft and case. "If the case can be repaired by welding, we don't charge anything, but if a crack is so large that it can't be welded or the case can't be salvaged for some other reason, we will charge the customer for a crankcase. Rarely does that happen. Typically, if there is serious enough damage that the crank or crankcase needs to be scrapped, the customer will know it."

Crankshafts, on the other hand have become a much larger problem. The need to scrap crankshafts has grown recently due to the introduction of a couple of controversial Airworthiness Directives. Middlebrook says, "Usually there were not any problems with crankshafts in the past because they just don't wear."

Certain Lycoming crankshafts (per AD 98-02-08) require the large diameter bore be honed, inspected, and coated, prior to being placed back into service .

But a recent AD 97-26-17 on Continental engines requires replacement of a large number of crankshafts to be removed based on their manufacturing process, and AD 98-02-08 requires replacement of 505B crankshafts on certain 160 hp and 180 hp Lycoming engines due to pitting in the large center bore of the shaft.

Middlebrook says the controversy is based on the fact that many overhaulers have shown that the crankshaft failure rate of airmelt crankshafts (the supposed defective shaft), is significantly lower than the VAR shaft which is the replacement crankshaft. "We will admit that the number of failures of airmelt shafts is indeed greater, but this is because the number of airmelts in service are much larger. As a percentage, however, airmelt failures are actually lower." Middlebrook emphasizes that "It is certainly no higher."

"We feel that this was one example of the general aviation industry suffering unnecessarily as a result of extreme pressure from the manufacturer to replace a part based on pure marketing. This contention was supported by the fact that if the engine owner had Continental overhaul the engine, they would pay no penalty for changing over the crankshaft to the approved part number. If they had someone else do the overhaul, they had to pay a $2,600 premium to have the crankshaft changed. I've personally seen two VAR crankshafts that have failed — one of them in a low time factory remanufactured engine, and the other was in a low time field overhauled engine. Right now, we're replacing crankshafts on virtually all of the old 520s, and some of the 360 Series."

Middlebrook continues, "The Lycoming crankshafts, frankly, are all pitted — and they always were. My understanding is that there were three or four failures in England, and so they issued an AD and put a lot of pressure on the FAA to issue an AD note, and so we have an AD note that requires us to pull out a large number of crankshafts that don't really need replacement."

The AD essentially requires you to hone the bore if any pitting is visible, and if the pits are gone once you've honed to a certain diameter, you can treat the metal, and put the crankshaft back into service. If pits still show after the honing process, the crank is scrap.

"We are actually having to scrap out about 50 percent of these crankshafts. There is a feeling in the industry that the failures that occurred weren't from the pitting, but from the manufacturer drilling the center bore off-center. Lycoming has since begun machining the center bore much more accurately and is producing a much smoother finish, and is coating the ID of the crankshaft to reduce pitting." he says.

Middlebrook says the original proposed AD was scheduled to affect many more engine models, but the industry fought it, through a couple of trade associations, and the result is that it only affects the 160 and 180 hp Lycoming engines.

Premium Overhauls

"New Limits" is the only way to go

By Greg Napert

October 1998

Accessories need attention
Middlebrook says that its really critical to address overhauling the accessories at the time of the overhaul. "You can build the best engine out there on the market, and then throw a bad set of magnetos or a bad carburetor, and the engine still isn't any good.

"Owners need to understand, up front, that there is a great deal of expense involved in accessories that go on the engine. Basically, all Lycoming engines today run with Precision Airmotive supplied fuel systems; i.e. Bendix servos or Marvel-Schrebler carburetors, or we have a Continental fuel injection system. The fuel injection system or carburetor can be very expensive to overhaul in both parts and labor. There are also fuel pumps that need to be overhauled on some engines. You also have the flow divider, lines, magnetos, housings, starter, alternators, turbochargers, wastegates, etc. You add all of those up and you've spent a lot of money overhauling accessories.

Because of this, we always supply the fuel system and ignition system with all of our overhauled engines. If someone wants us to simply build up an engine and doesn't want any accessories, we can't call it overhauled. If the customer wants, he can supply us with overhauled accessories and we will install them on an engine. But we can't "overhaul" an engine without accessories. We need those accessories to perform a the necessary testing that's required for an overhaul. Which brings us to another problem:

If you haven't tested it — it's not an overhaul
Middlebrook says, "Every engine we overhaul is tested. We will disassemble, inspect, and reassemble, or possibly put in a camshaft, and in this case we may not test the engine. But, on an overhaul, we are required to test. We provide all of our overhauled engines complete with accessories and fuel injection systems as these items are required for testing per the regulations.

Middlebrook says that according to 43.2, a "overhaul" requires that the engine be tested in accordance with manufacturers specifications. He deduces, "If there are no accessories on these engines, the engine never been tested, and thus, are not legally an overhaul."

This is a huge problem in the industry, he explains.

FAR 43.2 defines the word overhaul. It says:
(a) No person may describe in any required maintenance entry or form an aircraft, airframe, aircraft engine, propeller, appliance, or component part as being overhauled unless -
(1) Using methods, techniques, and practices acceptable to the Administrator, it has been disassembled, cleaned, inspected, repaired as necessary, and reassembled; and
(2) It has been tested in accordance with approved standards and technical data, or in accordance with current standards and technical data acceptable to the Administrator, which have been developed and documented by the holder of the type certificate, supplemental type certificate, or a material, part, process, or appliance approval under 21.305 of this chapter.

Lycoming and Continental does give you the option of testing the engine in the aircraft. Middlebrook explains, "I can overhaul that engine, put it in the airframe with calibrated instrumentation, a test club, and a cooling shroud, and test it in the airplane. But I can't sign it off as overhauled until after I tested it because the law won't allow you to do that.

"Yet there are A&Ps disassembling, inspecting, and reassembling engines out there and sending them back without accessories on it saying the engines are overhauled that have never even been tested. And the FAA is allowing this to go on."

Other challenges
Middlebrook says there is one more area of concern for overhaulers today. Many of the manufacturers, he says, supersede their parts and don't make the changes to the parts manual or provide any kind of supersedure list. What typically happens is that someone will order a part, and the manufacturer sends the most current version of that part. The person receiving the part then ends up with a part that has no documentation which supports installing it in the engine. Further, that part may require that an attaching part also needs to be updated, yet, there is no way to know. This can be frustrating and dangerous. Middlebrook says that keeping the invoice from the manufacturer along with a letter explaining the supersedure along with any affects it may have on other parts should be requested from the manufacturer. "It's rare the manufacturers respond in a timely manner and you have to make a decision if you want to be responsible for installing that part without documentation," he says.

Finally, Middlebrook says another frustrating problem in the industry related to overhaul shops is a level playing field. For instance, he points to the practice of upgrading the horsepower of certain engines by changing certain parts. Middlebrook says that these conversions require re-stamping the data plate and are essentially a type-certificate change. "This is going on all over the country," he says. "However, FAA Eastern region has said that this is illegal, and they made me go out and get a process specification in order to modify engines from one model to another. As a repair station, I have approval to do that, but I as an A&P cannot go out and do that in the Eastern Region.

"Other regions allow A&Ps and repair stations to do this without a process specification. If the party involved has experience doing this, it may not be a problem. But there are benefits to having to go through the ropes to obtain a process spec. For instance, many people think that the 150hp and the 160hp engines are the same except the 160 has high compression pistons. So, they believe they can upgrade any 150 to a 160 by installing high compression pistons. But the reality is that there are some 150hp engines that are convertible and some that aren't. Some 150hp engines don't have the main bearing structure to support the increased horsepower, and you have to know which ones are convertible.individuals involved in building up the engine.

"I would like to see the playing field leveled in this regard, and other shops required to get a process spec as well. It's not only an issue of fairness, but also of safety."

Middlebrook says that of all of the factors that contribute to a quality overhaul, none is more important than individuals involved in building up the engine. "Our engine build-up area is the most critical part of our operation. Our experience here between three individuals is over 70 years. This experience alone makes a huge difference in the quality of the overhaul."