# Do all the engines/propellers of a VTOL UAV need to be identical?

I would like to know if VTOL UAVs necessarily need $n$ identical propellers and motors. Have any design solutions considered the possibility of using non identical props? For instance 2 motors of type A, 2 motors of type B, and 2 motors of type C. If so, where can I find some studies or some designs that have attempted this kind of solution?

• I was thinking of VTOL UAVs featuring many motors, say 6 or more. In these cases it may be useful to use under given conditions and maneavures to not use all the engines, as it may imply that the working point would not be close to the optimum. The things you are pointing out would certainly be the disadvantages of having such solutions. Yet for high performance UAVs it may still be more important to have better consumptions or efficiency than better costs. @mins – Mirko Aveta Mar 29 '17 at 23:07