Farnborough Air Show

P&W prepares to deliver rivals’ parts in early ’07

 - November 15, 2006, 10:04 AM

After announcing the launch of its Global Material Solutions (GMS) division in February, engine manufacturer Pratt & Whitney has been busy making and testing parts for the CFM56-3 engine of its rivals General Electric and Snecma. Pratt & Whitney’s service division already overhauls and repairs CFM56 engines for airline customers and the company created GMS so that it could also offer lower-cost new parts to CFM56 operators.

United Airlines has signed on as launch customer for GMS’s CFM56 parts. “We’re proceeding on schedule and making a lot of great progress,” GMS program director Jim Pennito told Aviation International News.

GMS is seeking parts manufacturer approval (PMA) from the U.S. Federal Aviation Administration for the CFM56 parts that it is preparing to manufacture. And in a departure from what has been until now standard PMA industry practice, GMS is also applying to the FAA for PMA approval of critical life-limited parts, including shafts, fan hubs and discs. No other PMA company has obtained FAA approval for life-limited parts, and if Pratt & Whitney reaches its goal of PMA approval for life-limited parts, this will be an industry first.

Thus far GMS has begun manufacturing parts for the testing that must be done to obtain PMA. GMS is here at Farnborough International (Hall 4 Stand F13) showing some of the new CFM56 life-limited parts and instruments used to test them.

GMS will first seek approval of turbine airfoils and is expecting FAA clearance and initial sales of its Block 1 gas-path hardware in the first quarter of 2007, according to Pennito. The first batch of Block 2 life-limited parts–titanium, nickel and steel forgings–should be approved and on the market a year later, he added. While life-limited parts are new to the PMA business, PMA companies Belac (CFM56-3) and Northstar Turbine (PT6) have successfully replicated turbine blades.

By the middle of the third quarter of this year, GMS should be well into the validation phase, testing parts in an actual CFM56-3 engine.

P&W Changes Its Tune on PMA

Original equipment manufacturers (OEMs) such as Pratt & Whitney have complained in the past that PMA manufacturers don’t understand fully the environment inside the engines for which they are making parts. While PMA companies must prove to the FAA that they can precisely duplicate the materials and design of a part in order to obtain PMA, engine OEMs believe their knowledge of their own engines is far superior to that of a PMA company that designs parts but not entire engines.

Pratt & Whitney faces the same problem because it did not design the CFM56. “We don’t know the OEM specifications,” Pennito admitted. But Pratt & Whitney does know how to design and manufacture turbine engines and has spent years developing its own design system to produce parts to Pratt & Whitney specifications. “We have a calibrated design system,” he explained, “that enables us to look at limits and acceptable variations in hardware. We don’t look at matching [GE’s] tolerances, we look at what design system is acceptable.”

Lifing System

Pratt & Whitney’s design system is an important component of eventual FAA approval of life-limited parts. For the CFM56 parts, Pratt & Whitney is using the same process it uses to design and manufacturer its own life-limited parts, what it calls the “lifing system.”

The lifing system, Pennito said, “will establish the foundation for life-limited parts. The FAA is very familiar with our lifing system. What we need to show is how we’re going to apply that lifing system to these particular parts.”

This is an analytical tool that employs detailed models of the engine environment, not only internally, but operationally. The model considers variables such as amount of time at takeoff power, climb and cruise as well as details like the grain of the nickel used in specific areas on particular parts plus boundary conditions or how one part interacts with another. “It requires a great deal of data,” Pennito explained.

The benefit of the lifing system, which Pratt & Whitney developed in the 1970s, is that a new engine can enter service with lengthy life limits, instead of having to wait for field experience to validate and then later extend the limits. “It’s an extremely successful tool to establish life,” he said. “It’s our method of compliance with the FAA for life-limited parts. We did not want to develop a different method of complying with the FAA standards than the one we’ve developed and we are used to working with the FAA on any engine program, so we decided early in the program to go down this path.”

Testing of parts will take place in a CFM56-3 engine running in a Pratt & Whitney test cell. The company has developed telemetry technology that delivers information from many sensors deep inside the engine. “This telemetry technology is unique in the industry,” Pennito said. “It allows us to collect data on a full-scale engine that’s running.”

Instructions Tailored for Each Part

Pennito sees another difference between Pratt & Whitney as a PMA manufacturer compared to traditional independent PMA companies: production of instructions for continued airworthiness (ICA) for each PMA part. Many PMA companies replicate the OEM part and then instruct customers to use the OEM’s maintenance manuals to maintain the PMA part, which is permitted by the FAA.

“We are providing our ICA for this engine,” Pennito said. “Our path is to develop instructions that the customers can integrate within their maintenance procedures with as little disruption as possible.” This includes making sure that the Pratt & Whitney product support personnel are trained on the new parts, just as they are on ordinary P&W parts. Pratt & Whitney will also offer materials management programs that incorporate the CFM56 parts, including repairs. The company has already developed 2,000 CFM56 repair processes.

While a key goal is to make sure none of the Pratt & Whitney CFM56 parts alter the operation or performance of the engine in any way, GMS could improve some of the parts it is replicating. “We have some opportunities in the turbine gas path to make some improvements,” Pennito said. “It’s driven by customer feedback. If the customer would like to see some improvements, we’re contemplating putting them in.”