#1 Many people say the Turboliner as specified might be too big. I envision the Aircraft as a direct 737 / A320 replacement on shorter stretches <800nm4), not for long stretches. The A320 /737 are optimized for routes up to 3000nm.
Obviously offering a shrunk version of the Turboliner, would be an option. Europrop says the TP400 has growth potential so a future stretch would be possible also.
I sketched a shrink of about 150 inch / 5 seatrow / 30 seats.
#2 the TP400's first flights in getting closer finally. The Herc that has been modified is doing test runs (photo flightglobal). Note the additional struts that have been added to transfer loads/moments, damp vibrations, add structural stiffness or a combination..
A part throttle setting at lower speeds / take-off seems neccessary.
