## 1 Introduction  
Generally, engine operating regimes are described through the variation diagrams between certain engine performances and some main engine parameters [1, 2]. In terms of the free level of accessibility of aviation documentation, if reference is made to a wide range of engines, in general, the actual values of engine parameters or performances at different engine regimes are not presented. Most of the information about the values of certain engine main parameters are specified in the engine manual, a document that is acquired from the manufacturer, or in the engine data sheet (a document more accessible than an engine manual), and usually are shown data only for operating regimes as takeoff (d), maximum continuous (c), cruise (b), and idle (a). Even in the engine manual the actual values of variation of the idle regime (a) to the maximum regime (d) for a wide range of parameters are not presented. In some cases, particular charts are presented, and if the charts are clear or easy to read, then some approximate values can be extracted and used to calculate or determine other parameters.  
For example, similar to the current study, Figure 1 presents a chart with the maximum values of some engine parameters at main engine working regimes [3] for the TV2-117A (AG) turboshaft, according to the engine manual at sea level conditions, defined by variation of the effective power (\(P\)), effective fuel consumption (\(F_{c}\)) and inlet turbine gases temperature (\(T_{3t}\)), reported to the gas generator speed (\(N_{GG}\)).  
Also, some specific research [4, 5, 6] studies the performance of turboshaft engines by operating at different shaft speeds and present several curve variations diagrams of obtained engine parameters.  
The aim of the paper was to study various working regimes for a specific experimental testing procedure by simulating diverse loads on a free power turbine [7] by setting different torques from a hydraulic dynamometer. This particular testing procedure is different than the run tests described in the manufacturer's manual and the tests for maintaining when in service or in operation. The engine was supplementarily instrumented because it was equipped with a standard instrumentation and instrumentation for engine regimes studies, which require additional parameters in order to determine other main engine parameters and performance measures which are evaluated and analyzed through the working engine regimes. These parameters were measured or determined using instrumentation methods that were applied and implemented for other experimental TV2-117A run tests [8].  
These run tests were executed for a technical study of a TV2-117A turboshaft implemented into a cogeneration power plant project [9]. The acquisition of parameters was based on Digital Acquisition Control System (DACS) from Safran and has the capabilities to acquire more than 256 parameters for different types, such as, pressure, temperature, vibration, speed, flow meter, digital input, digital output, analogue output at an approximately 100 Hz acquiring rate for engines operations, service and maintenance and at an approximately 10 kHz for research projects where high measuring precision is required and some limitations can be applied [10]. The instrumentation lines were calibrated and checked by the Metrological Laboratory of National Research and Development Institute for Gas Turbines COMOTI [11].