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when oil flow is cut off, these bearings can be damaged. In addition, any stagnant oil remaining around the extremely hot turbine shaft will overheat and ‘coke’ or burn.But why is the turbo still spinning at a high rate of speed after landing? Well, it all goes back to proper planning and power management, which includes a normal descent at reduced power settings to stabilize and maintain engine temperatures.As the aircraft enters the landing phase, engine power is reduced even further and then taxiing is done at low power settings. By the time you’ve reached the ramp, all engine temperatures should be stabilized and the turbocharger should now be turning at its slowest speed.But, and I can’t stress this enough, even then, depending on the type of system installed, additional cooling time may be required prior to engine shut down.(HET has produced an informative, short video on the critical importance of proper turbo cool down. Check it out at: www.hartzell.aero/eo2yU)And, while improper pre-shutdown cooling is one of the most common mistakes pilots routinely make, turbocharged, intercooled, high-performance enginesrequire constant monitoring of the systems throughout all phases of flight.And all that starts with proper fuel mixture, CHT and EGT management, including proper flight planning to avoid over-temping or thermal shock. As is often the case, good piloting technique is critical to optimum system reliability and performance.Out With The Old...Okay, so even with proper operations, sooner or later your turbocharger is going to start showing signs of distress. What are your options?Turbocharger systems rely on very sophisticated components with tight tolerances and little room for error. Because of that, if your turbocharger needs maintenance the question becomes whether to have it overhauled or exchange it for a new or rebuilt unit?The cost of a factory-new turbocharger is only slightly higher than a rebuilt unit and there is no core return required. So, you get all new parts and it’s hassle free. HET also offers factory-rebuilt units on an exchange basis for most of our models.Pilots and mechanics often ask what the difference is between a new and a “factory rebuilt” turbocharger. Other than the fact that one is all-new and the other is ‘rebuilt’ there is really no functional difference.In fact, the regulatory definition of a rebuilt turbocharger is, in essence, that it has to meet the standards of a brand new unit. When we do a rebuild here, we use some of the original parts, but many of the parts get replaced with new – especially critical parts such as the highly-stressed turbine wheel.So, if rebuilt and brand new turbochargers are basically the same, what about a “field overhauled unit”? Overhauled units are not required to meet ‘new’ standards, so they can be less expensive. In most cases, the typical field overhaul shop will reuse more of the original parts than HET typically does. There’s nothing wrong with that, as long as they follow the latest manuals,LEKTRO, Inc. Quarter Page 4/C Ad18 • TWIN & TURBINENOVEMBER 2016