hi all
octa multi-rotor type , I or V
MC= A2
If one motor fails in flight, what will happen?

If your copter is not overloaded  in terms of weight the copter should stay in the air and you should be able to bring it down.
Some loss of maneuverability may be present and the amount of thrust available will be reduced.

either A2 FC or Nava V2 FC are well capable of holding a hex or octo in the air long enough for you to get it down.

it will be a little unstable but still very manageable

a quad, however , with the same FCs, will behave like a manhole cover if a rotor fails.