US Patent 10906656 Hybrid tiltrotor drive system

An exemplary tiltrotor aircraft with a hybrid drive system includes a first propulsion system having a first engine and a first supplemental driver operably coupled to a first proprotor that is operable between a helicopter mode and an airplane mode and a second propulsion system having a second engine and a second supplemental driver operably coupled to a second proprotor that is operable between a helicopter mode and an airplane mode.