The Airbus $318$ with two Pw$3600$ engines has the following performance characteristics:

Engine:

$-$ Dual$-$spool high$0$bypass turbofan jet.

$-$ Fan diameter $=1\mathrm{.}44$ m

$-$ T$=40$ kN$/$engine

$-$ Assume, Mass flow of fuel$=$ negligible.

a$)$ Calculate Vjet. $[7]$

b$)$ Calculate propulsive efficiency. $[7]$

c$)$ Explain how dual$-$spool works in engine, $[2]$

d$)$ Explain by pass principle of the engine operation and how it helps to achieve higher

propulsive efficiency compared with classical turbojet engine configuration.