Abstract
The plane Couette flow undergoes a globally sub-critical transition to turbulence. Turbulent spots generated by localized finite-amplitude perturbations evolve differently depending on the Reynolds number R. Below Ru ≃ 312 they decay rapidly; above Rc ≃ 323 a fraction of spots turns to sustained turbulent patches and an average turbulent fraction can be defined, that slowly increases with R. Lifetime histograms of patches quenched in the range R∊[Ru,Rc] display a well-defined exponentially decreasing tail. This behavior is reminiscent of the discontinuous transition to spatiotemporal chaos via spatiotemporal intermittency observed in certain two-dimensional lattices of coupled map.