charlicopter Posted February 7, 2010 Report Share Posted February 7, 2010 Hey all, I'm studying AS350 BA, B2 & B3 systems and I've gotten around to the engine at this point. Anyone know where I could get some rich technical and operational information on these engines? Digital manuals? Etc... Additionally, regarding Delta Ng: I believe that I have a grasp of the function of the gauge but I need some guidance on the finer details: Basically it is an N1 analog that interfaces with a computer. The computer takes readings of pressure and temperature and applies an algorithm to N1, weighting it against the ambient conditions and presenting N1 on the dial adjusted to relevant values. The digital N1 underneath the analog is unadjusted and is used during startup and as a cross reference so that you can verify the Delta Ng values. In a way, I imagine that a manifold pressure gauge in an R-22 could be redesigned to do the same thing: Manifold pressure indirectly tells us how much power the engine is producing by measuring the vacuum pressure in the intake. We can sort of deduce the power of the engine by knowing what maximum power is possible at wide-open-throttle at specific air densities and interpolating. But since air density is variable, then assumed power produced at a specific manifold pressure is variable. Hence the chart to inform us of specific MAP-Power relationships. If we wanted, we could make a Delta-MAP gauge that would take temp and pressure and bias it against MAP to tell us directly how much power the engine is projected to be putting out... So this is where my understanding breaks down... Turbines are different. In a turbine I don't fully comprehend what happens to the speed of the engine as DA changes. At various DA scenarios, Ng will change for a given amount of power. If the engine moves to a higher DA, then it seems to me that it must turn faster to compress and burn additional air in order to maintain power... Since I understand Ng (or N1) to be important for structural reasons (namely centrifugal) then it follows that the Ng limits do need to be considered at different DA's (mainly higher DA). BUT DON'T THE STRUCTURAL LIMITS ON THE COMPRESSOR AND TURBINE STAY THE SAME? Why do we have to adjust the indicator dial to compensate for DA? In other words: Won't we hit the structural Ng limit at the same RPM regardless of DA? Quote Link to comment Share on other sites More sharing options...
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