One of the most perspective directions of aircraft engine development is related to implementing adaptive automatic electronic control systems (ACS). The significant elements of these systems are algorithms of matching of mathematical models to actual performances of the engine. These adaptive models are used directly in control algorithms and are a combination of static and dynamic sub-models. This work considers the dynamic sub-models formation using the Least Square method (LSM) on a base of the engine parameters that are measured in-flight. While implementing this function in the (ACS), the problem of checking the sufficiency of the used information for ensuring the required precision of the model arises. We must do this checking a priori (to determine a set of operation modes, the shape of the engine test impact and volume of recorded information) and a posteriori. Equations of the engine models are considered. Relations are derived that determine the precision of parameters of these models’ estimation depending on the precision of measurement, the composition of the engine power ratings, and durability of observations, at a stepwise change of fuel flow. We present these relations in non-dimensional coordinates that make them universal and ready for application to any turboshaft engine.
Numerical model for selected turboshaft engine is highly required by helicopter and aircraft designers. Presented paper includes key features for turboshaft numeric model builders. The study of the real performance and estimated results showed that presented method is exact for higher throttle levels. Presented method will be useful for preliminary design when is no need to acquire real test data. Numerical model was build for steady state operations, because maintenance manual for selected engine includes tests records only at its state. In that case helicopter turboshaft manuals are very similar, steady state was used widely for testing in TB3 and T700 family engines. Steady state reduced effect of rotor head positions which was influencing total engine performance. TB3-117 helicopter turboshaft engine, engine cutaway sections, first step - expansion ratios, second step - on the ground calculations for different throttle position, engine inlet mass flow ratio as a function of maximum allowable EGT, and throttle position, third step - on the ground calculations for different throttle position, second step - on the ground calculations for different throttle position, performance charts for RR-250 BJ turboshaft, and for TB3-117 M/MT - Mi-14/17, TB3-117 III-series Mi-24 are presented in the paper.
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