## 6 Discussion  
Following the calculation of main engine percentage values, it can be seen that the parameters have different variation values, do not vary in the same way and start from different values of variation. One way to prove that the acquisition and operation of engine were correctly executed, the experimental data values with the data manual values must be compared at the same engine regime. So, because the experimental data are not provided at standard atmospheric temperature and pressure, in this case it is required to correct the data with the standard sea level conditions (\(T_{0}=15\) \({}^{\circ}\)C, \(p_{0}=1.01325\) bar a).  
Table 8 presents certain main engine parameters and performances that are determined based on the data from engine manual [6], at different operating regimes.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Regime** & **NGG [\%]** & **NTP [\%]** & **P [kW]** & **F\({}_{\text{C}}\) [kg/h]** & **T\({}_{\text{3t.max}}\) [K]** & **S\({}_{\text{FC}}\) [kg/kW/h]** & **\(\eta_{\text{te}}\) [\%]** \\ \hline Idle (a) & 63 +2\(/-\)1 & 47.2 \(\pm\) 10 & 74 & 100 & 823 & 1.359 & 6.18 \\ Cruise (b) & 94.5 & 99.7 \(\pm\) 2 & 736 & 310 & 1083 & 0.421 & 19.92 \\ Max. Cont. (c) & 96 & 99.7 \(\pm\) 2 & 883 & 354 & 1133 & 0.401 & 20.94 \\ Takeoff (d) & 98.5 & 97.6 \(\pm\) 1 & 1104 & 412.5 & 1148 & 0.374 & 22.46 \\ \hline \end{tabular}
\end{table}
Table 8: TV2-117A operating regimes.  
Figure 14: Engine power and the thermal efficiency percentage variation.  
Table 9 presents the corrected values of experimental data of the same main engine parameters and performances, at approximately the same operating regimes, similar to engine manual.  
Therefore, to compare the experimental data with data manual, the percentage differences were determined by the following mathematical relations:  
\[\Delta N_{\text{GG}} =N_{\text{CG,$\alpha$0}}-N_{\text{GG,$\alpha$na}} \tag{15}\] \[\Delta N_{\text{TP}} =N_{\text{TP,$\alpha$0}}-N_{\text{TP,$\alpha$na}}\] (16) \[\Delta P =\frac{P_{\text{$\alpha$0}}-P_{\text{$\alpha$na}}}{P_{\text{$\alpha$ na}}}\] (17) \[\Delta F_{\text{C}} =\frac{F_{\text{C,$\alpha$0}}-F_{\text{C,$\alpha$na}}}{F_{\text{C,$ \alpha$na}}}\] (18) \[\Delta T_{\text{3$t}} =\frac{T_{\text{3,$\alpha$0}}-T_{\text{3,$\alpha$na}}}{T_{\text{3,$\alpha$na}}}\] (19) \[\Delta S_{\text{FC}} =\frac{S_{\text{FC,$\alpha$0}}-S_{\text{FC,$\alpha$na}}}{S_{\text{ FC,$\alpha$na}}}\] (20) \[\Delta\eta_{\text{$\iota$e$}} =\frac{\eta_{\text{$\iota$e$},\alpha$}-\eta_{\text{$\iota$e$}, \alpha$na}}{\eta_{\text{$\iota$e$},\alpha$na}} \tag{21}\]  
Table 10 presents the values of percentage differences between some main engine parameters and performances from the experimental and manual data.  
In the case of the idle (a) regime, the differences are a maximum of 25% because the data from the manual are for the maximum values of each parameter and the engine starts under different torque values. In the case of other regimes, the differences are a maximum of 6%, because there are some small differences in gas generator speed, and these differences at higher regimes affect the values of the parameters. Because the engine regimes depend on the demanded torque from the dynamometer, engine adjustments are required to test the engine under the same gas generator and speed values as is specified in the engine manual, so in this way the values will decrease to under 5%.