Aircraft Maintenance Technology

MAY 2017

The aircraft maintenance professional's source for technological advancements, maintenance alerts, news, articles, events, and careers

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www.AviationPros.com 17 system. The aim is to keep sand, salt, gravel airborne effluent, and the like from migrating to the engine's core where they can wreak havoc with parts and erode fuel economy. Here's how the debris rejection sys- tem works. During takeoff, an inherently high-thrust affair — especially at hot and high airports — variable bleed valves are opened. The idea is to direct debris around the engine, rather than through it. During lower-thrust flight regimen the doors are closed. This begets better fuel economy. The result, says CFM, "is an infinitely more durable engine." Time-on-wing and fuel economy are two of LEAP's largest selling points. CFM says current production CFM56s have a 20,000-cycle life-limit on the core, and a 25,000-cycle limit on the low-pressure system. The CFM56 and LEAP share the same core life cycle limit, but the newer powerplant possesses a 30,000-cycle life- limit on the low-pressure system. In written response to Aircraft Maintenance Technology, CFM says, "The commitment to customers was that LEAP maintenance costs would be comparable to that of the CFM56 … At the end of the day, we expect total engine life-cycle costs to be comparable to what customers have experienced with the CFM56 fam- ily" — this despite the introduction of some cutting-edge materials and blade aerodynamics. Longevity and durability are hard-won when it comes to gas turbine engines. "Historically, [they] always used rich quench lean combustion," says Dwyer. "It's easier to do. It's lighter weight." It's also the source of hot streaks. He says the durability-robbing spots are concentrated on the static parts of the turbine. "That's' where parts wear out." It's also where LEAP's new TAPS II twin-annular, pre- mixing swirler comes into play. Think of it as a nozzle on a dual mission: to lower maintenance costs and cut greenhouse gas emissions at the same time. Fuel and air are premixed before they enter the combustion chamber for ignition. CFM says TAPS II produces "a more benign temperature profile." "Lean burn combustion lowers the difference between the average and the peak [tem- peratures]," says Dwyer. "It's a huge part of our design formula." If TAPS II is revolutionary, so is the way the nozzle is fabricated. It's formed by additive manufacturing. CFM contends the fast-growing technique enables the engine- maker to produce parts "not possible with A V I A T I O N F A B R I C A T O R S Density. Comfort. Now there is a high density seating solution that maximizes executive comfort – with lasting durability for executive and commuter King Air aircraft configurations. The AvFab GT High Density Executive Transport Seat is lightweight and affordable, with elements that make it conducive to maximum high density applications. This seat was specially designed to enhance the ease of occupant ingress and egress by increasing leg, knee, foot room and passenger comfort. Experience the robust, lightweight high density seating on your King Air today. (660) 885-8317 / www.AvFab.com HIGH Comfort. Function. AviationPros.com/company/10133921

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