What was likely said next? Dialog: * What are the main characteristics of the RF-1? * Rhein-Flugzeugbau RF-1 The Rhein-Flugzeugbau RF-1 "Rhein Flight RF-1" was a prototype channel wing aircraft. The RF-1 is a modification of the channel wing concept, that uses a single channel and propeller to eliminate the asymmetrical lift issues with a twin channel wing design. * What is the channel wing concept? * The "channel" is an airfoil-shaped section along the lower arc of the rearward propeller that produces additional lift from the propwash. * What other interesting characteristics are there about the RF-1? * The RF-1's propeller was completely shrouded, creating a hybrid ducted propeller. * Why is the propeller completely shrouded? * Twin engine redundancy is maintained with multiple engines driving a central propeller with freewheeling clutches to allow for an engine failure. * What other things are unique about the RF-1? * 
The aircraft had the unique shape to facilitate a channel wing design.