Contra-Rotating Propellers

Contra-rotating propellers are two propeller assemblies mounted on the same axis and turning in opposite directions. In the source dossier that seeds this page, they are the lift-producing element of the Focke Rochen: the source states that the aircraft's open center "acted as a huge propeller duct for twin contra-rotating propellers, driven by a projected Focke-Wulf designed turbojet engine via an axle and gearbox."

Role in the Rochen

• The two propellers sit inside the annular duct of the Circular-Wing Annular-Duct Configuration.
• Drive is claimed to come from a projected Focke-Wulf turbojet through an axle and gearbox — a mechanical transmission from a jet engine to propellers, not a direct-jet arrangement.
• The propellers feed the Downwash Vectoring Louvers used for the transition to forward flight.

Evidence status

The source gives no propeller diameter, blade count, rotational speed or thrust figure, and the aircraft was never built. The arrangement is recorded as a design proposal.