Use of PMA parts growing within rotorcraft ranks

 - July 30, 2008, 10:17 AM

“PMA parts? Ooh, now there’s a murky area,” said a maintenance supervisor who oversees the upkeep of an offshore oil support helicopter fleet numbering well over 100. His is the kind of large-scale operation where saving 10 percent on routine maintenance results in significant additions to the year-end bottom line. It’s also the kind of operation in which the perceived contraindications of using Parts Manufacturing Approval (PMA) components are carefully weighed against the benefits. The company is one of a growing number of helicopter operations that are availing themselves of the cost-cutting benefits of PMA parts.

What the maintenance manager said is as important as the way he said it: tired and wary of the misunderstandings and misconceptions surrounding the world of PMA parts.

Before proceeding with a discussion of the rising use of PMA components, it’s important to define some terms and remove a bit of the murk from the aftermarket parts landscape.

PMA parts are replacement aircraft parts made by someone other than the original equipment manufacturer (OEM). Officially (that is to say, legally) the PMA business has been around since the late 1940s, when it was conceived chiefly as a way of keeping out-of-production aircraft in service. Feeding this small industry, PMA parts makers occupied an obscure niche in the regulatory framework, with the FAA taking little notice of it until 1988, when the so-called Comsis report was issued, a report that legitimized the PMA concept via a standardized approval process.

Once the PMA regulatory framework was better defined, the number of PMA’d parts exploded, driven mainly by the plethora of new airplane and engine designs. Many manufacturers, anxious to make money on their newer products, were grateful to place some of the aftermarket responsibility for their older models on PMA makers. Later, at least one engine builder would regret that move when depressed front-end sales led it to a greater dependence on its aftermarket support.

By the Book

PMA regulations (FAA Order 8110.42A “Parts Manufacturing Approval Procedure”) mandate the processes under which the FAA authorizes a third-party manufacturer to produce a given critical or noncritical aircraft component, certifying it to be airworthy and as identical as possible to the part it is replacing. (Contrary to popular belief, the OEM does not sign off on this permission; that responsibility is left to the FAA.)

According to various estimates, PMA parts sales represent about 5 percent of the total aviation spare parts business, a percentage gradually growing in these recessionary, and ever more cost-conscious days. In surveys conducted for this article, use of PMA parts to replace the high rotables in an overhaul of two popular Rolls-Royce 250 series engines shaved 18 to 28 percent off the total price of using exclusively OEM parts. (Rolls-Royce 250 engines were selected because they have a large installed base of more than 16,000 powerplants.)


But by far the larger number of PMA parts make up non-engine, non-flight-critical items. Judging by the heat of the controversy surrounding the subject, it might be thought the opposite were true. Even more surprising is the fact that many of the top OEMs, especially in the rotorcraft world, are also the biggest producers of PMA’d parts. There’s a reason for that.

The majority of PMA parts, but by no means all, are manufactured as replacement parts for OEM parts. As a concept, OEM is somewhat ambiguous because most type-certified components are composed of parts manufactured by many different companies. For instance, according to Aviation Data Research (ADR), the top three PMA helicopter parts are made for the three largest helicopter makers–in descending order, Sikorsky, Bell and Eurocopter France.

The lion’s share of these cover work the manufacturers have farmed out to subcontractors. For example, Sikorsky subcontracted the entire S-76 fuselage to Czech airframer Aero Vodochody, an arrangement doubtless involving hundreds of PMAs for specific parts, components and subassemblies.

Frequently these parts will carry dual part numbers, one by the OEM and one by the TC holder.

When seeking a given part on a commercially available PMA parts database (such as ADR’s excellent “PMA Parts Folder,” available for commercial download from www., it is usually better to search by OEM part number rather than OEM name since the part numbers are rarely duplicated. The software tool from ADR is invaluable for anyone entering the PMA parts thicket.

Yes and No

A good example of the identity crisis facing the PMA business can be found in the sprawling shops of Keystone Helicopter, the 50-year-old rotorcraft service center in rural Pennsylvania that’s probably the best-respected enterprise of its kind on the East Coast. A Rolls-Royce-authorized service station, Keystone, like every other Rolls-Royce-authorized station, will use only Rolls-Royce-made parts in the Rolls-Royce engines (Model 250 Type II [C20] and IV C30/C47) it works on. “Well, there are some exceptions,” admitted Keystone engine services division v-p John Loney. “We will install a PMA part if the customer demands it, if the customer supplies the part himself and if the customer understands that its installation voids any Rolls-Royce warranties in effect on that engine. Needless to say, we don’t get very many requests for this. But we’ll do it if the customer wants it.”

At the same time and in a building just a few dozen yards away, another division of Keystone, the company’s KeyTech engineering subsidiary, is proudly developing PMAs by the file-cabinet full for the very same helicopters on which it is barred from installing duplicate Rolls-Royce parts.

And in that seeming contradiction lies a basic fact of PMA life that confuses many: there are really two separate and distinct types of PMA. “When we design a medical interior for a helicopter, it’s approved for sale under an STC and the parts for it are fabricated by vendors to Keystone under PMA,” explained Keystone president and COO Peter Wright. “We provide outside parties with the data they need; it’s a cooperative effort on both sides. There’s a big difference between that sort of PMA approval and for a part that’s produced in direct competition to those produced by OEMs. While there is a huge difference between the two types of PMA approval, most people don’t understand that.”

Friendly and Otherwise

Regulations permit fabrication of PMA parts under any one of three criteria. First, PMA parts makers can submit evidence that they are party to the original type certification from the very beginning of the OEM’s design process. Second, they can submit evidence of a subsequent licensing agreement with the OEM. Known under the collective cognomen of “identicality,” this is the simplest method as the OEM is amicably converting the part’s status from OEM-made to PMA-made.

If they are not allowed to see and use the secrets of the original type certification, PMA makers can submit other proof, such as test reports and computations, showing their part to be as good as or, in certain cases some say, better than the original. According to figures published by the Modification and Replacement Parts Association (MARPA), 10 years ago some 90 percent of all PMA parts were authorized through identicality. Today, the more controversial test and computation technique accounts for between 30 and 40 percent of all new PMAs. The increasing availability of PMA parts carries the added advantage of augmenting OEM stock, thereby helping stave off AOG situations.

The Rolls-Royce/Extex War

Given the economics of the multibillion-dollar parts business, battle lines have been drawn between PMA makers who have invested serious sums in their own product lines and OEMs who have spent large amounts of their funds fighting off what they consider to be a major threat to their aftermarket livelihood.

Probably the bitterest OEM/PMA war is being waged between Mesa, Ariz.-based PMA maker and PMA distributor Extex and engine manufacturer Rolls-Royce. The prize at stake is Rolls’ in-service population of more than 16,000 Model 250 turboshaft engines, a market Rolls would very much like to keep to itself. However, over recent years Extex, led by president Larry Shiembob, has been digging and scratching its way into Rolls’ aftermarket at a steady pace.

The nut of the battle, of course, is money. According to an industry rule-of-thumb, PMA parts cost 25 to 30 percent less than OEM parts. In a head-to-head comparison of the parts needed for a top-to-bottom overhaul of a 250 Series IV engine, Extex parts cost 27.3 percent less (see table on page 94); for an overhaul of a 250 Series II engine, 18 percent less.

Price isn’t the only reason operators make use of PMA parts. Down on the shores of the Gulf of Mexico, Doug Forlund, Air Logistics maintenance director, said, “It isn’t just the price, although obviously that’s a factor. Our use of PMA parts has a lot to do with their availability. We found that the PMA vendors just had the parts we needed and could get them to us more often. Rolls has made some big improvements in recent months, but they’ve still got a ways to go.”

“When Rolls-Royce acquired Allison it really dropped the ball on service,” asserted one Sun Belt operator who requested anonymity. “It’s understandable, I guess. They were used to dealing with major airlines at the big end of the engine business and it took a real change in philosophy to learn to talk to the little mom-and-pop operations. They still are often slow to respond, and that’s when we turn to the PMAs.”

Not surprisingly, Extex’s Shiembob is a PMA proselyter. It’s how he makes his living and he’s not reluctant to claim that some of the parts his company makes and sells are better than those he’s replacing. Of course, that means abandoning identicality as a method of making PMA parts. “We use the test and computations methods to get our PMAs,” he said. “All of our parts are reverse engineered without OEM data, a way for us to avoid any future legal entanglements. Even better, parts made under test and computations rules can be different, allowing opportunities to incorporate improvements.”

One of the areas Shiembob has targeted for such improvements is the 30-year design that is the basic Rolls-Royce 250 engine. In its rework of the seven-stage compressor wheel for the 250, Extex used an alloy not used for this part by Rolls-Royce and machined that part for what Extex claims are tighter tolerances on blade profile, setting angle and root radii. The result is a 4.2-percent power increase along with a 22-degree F turbine outlet temperature decrease and a claimed 1.5-percent improvement in specific fuel consumption.

Any high-school economics student can tell you that the benefits of open-market competition are increased product availability and diversity at lower cost. Therefore it should come as little surprise that Rolls has dropped its prices on some of the more popular items offered by Extex and other PMAs. Such price decreases serve as evidence of the PMAs’ market power. Figures generated by Shiembob hold that price reductions made by Rolls-Royce in reaction to the competition brought to the market by PMAs have resulted in an across-the-board saving of $200 million over eight years, meaning that even non-users of PMA’d products have enjoyed savings on the operation of their Rolls-Royce 250s, thanks to the PMAs’ existence.

When contacted for this article, Rolls-Royce declined to comment on specific claims made by Extex.

You May Not Have Any Choice

If you’re going to go after a portion of a given engine’s market, one primary rule for the PMA parts maker is to pick an engine or airframe with a sufficiently large in-service population to make it worth the attention. It can be assumed that the manufacturer will retain a majority slice in this market pie through simple brand-name loyalty, if nothing else.

“Do I use PMA’d parts?” Air Star president Ron Williams asked rhetorically. (Air Star is an upscale air-tour operator doing business on the south rim of the Grand Canyon.) “No, but I’d love to. My problem is that I use Eurocopter helicopters powered by Turbomeca engines, which so far haven’t attracted any PMA parts makers. I guess there just aren’t enough of them in service to attract the PMA guys’ attention. But when and if that happens, I’ll definitely take a look at them.”