Uploaded January 2024 | Updated September 2026, 1 week ago
Unducted fans (UDFs), also known as propfans or open rotor engines, first popped up in the 1980s. Typically, there's a lot of blades, and they're swept back, and heavily twisted. The rear blades are twisted in the opposite direction to the front ones; sometimes they counter-rotate, others don't rotate at all, acting as variable-pitch stator blades to help with flow recovery.
Unducted fans (UDFs), also known as propfans or open rotor engines, first popped up in the 1980s. Typically, there's a lot of blades, and they're swept back, and heavily twisted. The rear blades are twisted in the opposite direction to the front ones; sometimes they counter-rotate, others don't rotate at all, acting as variable-pitch stator blades to help with flow recovery.
