Engine Testing Shows Power Increase And SFC; Temperature Decrease

Following recently completed engine testing to confirm the performance characteristics of its fully-machined RR250 compressor wheels, compared to standard-cast wheels produced by Rolls-Royce, EXTEX Ltd., of Mesa AZ, has now added these parts to its catalog. Under identical test conditions, EXTEX wheels produced 4.2% additional horsepower at the same Turbine Outlet Temperature (TOT). They produced the same horsepower at a 22°F lower TOT, and Specific Fuel Consumption (SFC) was 1.5% lower at cruise power.

The CNC-machined stage-1 through -b compressor wheels were introduced at last year's Heli-Expo and were significant because of their improved mechanical properties. At that time, Jerry Reno, EXTEX product manager, highlighted several direct benefits in the new forged compressor wheels.

"There is a six per cent strength increase over our original castings, and an impressive 20 per cent increase over the OEM's castings." he said. "The more precise CNC machining of the airfoils ensures consistent blade root radii and blade thickness for improved endurance. Our CNC machining process provides a precise blade angle, leading and trailing edge radii and generally more precise airfoil dimensions."

"We knew these wheels were mechanically superior and we expected a performance benefit, but frankly we were surprised by the magnitude of the improvement" said Dave Daniels, EXTEX vice-president, sales and marketing. "Besides providing a more durable, more maintainable product we are now able to lower operating temperatures and reduce fuel burn, which help to reduce operating costs even further." Daniels added.

The improved EXTEX compressor wheels are now available for immediate delivery, still at a lower price than the OEM alternative. Daniels added, "Our goal at EXTEX is to make superior products and we are not content with copying old designs. The marketplace wants improved parts, and we are providing our customers with new technology at a lower cost.

EXTEX, the world's largest PMA source of Rolls Royce helicopter engine parts, produces over 350 parts for the RR250, including nozzles, compressor wheels, splined adapters, combustion liners and gears. EXTEX parts are designed for enhanced durability, are produced from modern alloys, and incorporate the latest manufacturing technology.

The company also manufactures parts for auxiliary power units (APU) for airline and business jet aircraft, supplying critical, high use parts such as turbine blades, shrouds and nozzles, and compressor blades. Engine parts are available for Honeywell GTCP 331, GTCP 36, GTCP 85 and TSCP 700 series APUs. Airline clients include American, United, Northwest and Air Canada.

FMI www.extex.com