Concorde Vzrc
I wonder if you guys can elighten me. I've been reading a few books on Concorde recently and the concept of Vzrc is introduced.
In Chris Orlebar's book he goes further to show a table of Vzrc for an aircraft carrying maximum weight with gear up/down and for 2/3 engines. This is used to illustrate the deep trouble the Air France plane was in once engine 1 went offline for the second and final time. That's where I get confused.
My question is: why does Vzrc vary with the number of engines? Surely the minimum thrust required to keep the aircraft in level flight is a fixed number, and if you can keep X knots on the clock why does it matter how many engines are used to achieve this?
Sorry for being at home to Mr. Thicky!
Thanks,
Duncan