 Let us also look at how do you get the SFC values in cruise and loiter. Again we have to take recourse to historical data. The SFC values this is again the chart from Reimers textbook where the equivalent jet SFC values are plotted against the Mach number for various types of aircraft and with this chart you can get rough idea but this is just an indication. So this chart actually helps you decide which kind of engine is to be used depending on the Mach, depending on the cruise Mach number or the maximum Mach number that you want the aircraft to achieve you should select the type. For example, this is a nice intersection where low bypass turbofan and turbojets they roughly have a crossover. So, at Mach numbers beyond around 1.8 it will be better to go for turbojets because they are going to have a lower value of the SFC. Similarly, when you go to around 3.7, 3.8 Mach number you start seeing that the turbojets are going to have a increasing trend in SFC whereas then the ramjets are going to become more economical. So, depending on which kind of Mach number you are going to follow for low speed aircraft you can see up to Mach number of around 0.4 piston prop turbo prop are okay. After Mach number 0.4 you start seeing turbo props becoming better below that the piston props have a much lower. So, the lowest SFC is for the piston props this is the line for them, but you know. So, this start actually helps you decide what power plant to use. Typical values of SFC in SI system which is in milligrams per Newton second. This particular unit milligrams per Newton second is used because the numbers which come out are easy to mention and talk about rather than saying 0.000255 or some such very small number. When you work in milligram per Newton second you get number like 25, 30, 14, 15 which are easy to talk about. So, if you do not have any idea about typically what you will be getting you can assume these values these are realistic numbers and if you have a piston prop or turbo prop aircraft in mind. In these aircraft the typical values of the SFC based on power or called as power SFC in milligram per watt second tend to be as listed here. So, this particular chart is quite useful to start off and this has come from the Reimers textbook. Professor Scott Eberhardt has plotted the historical TSFC trends for turbofan engines and you notice that consistently the TSFC is going to is reducing. So, this indicates that as the year progresses SFCs are coming down. But if you look at the data for cruise SFC for jet engine aircraft we see that we are now slowly reaching some kind of a flattening if you have a bypass ratio beyond 8. So, up to 8 bypass ratio they are slowly come down after the bypass ratio of 8 to 10 they start to becoming flat. Thanks for your attention we will now move to the next section.