Sorry Hesham, I don't understand your question about this Pa.120
I have in my archives a discussion dating from December 2007 on the French forum Aérostories. French aviation writer Philippe Ricco replies to Christian Bonnet (I think he was a restorer of old planes):Does anyone know how these engines were supposed to work?
-Bonnet : It is possible that no development followed, due to poor performance due to low compression ratio. In order to counter this inconvenience, Melot made a device with a free piston engine (hey, it reminds me of Pescara), compressed air was needed at start-up. Ernest Morize seems to have studied a similar system.
-Ricco : No, it was not because of a performance problem, but rather the autonomy of the device. I had discussed it in particular with Philippe Poisson-Quinton, who had been responsible for studying this device, before participating, after the war, in the creation of ONERA. He had been very pleasantly surprised by the results obtained.
The trouble is that this trump thruster system is a flow accelerator, just like a ramjet. Alas, it needs a complement to initiate the phenomenon and obtain the thrust. We also find the same principle described in certain studies by Henri Coanda.