Originally Posted by
tdracer
Oh, you just reminded me - back in the late 1980s, they did a flying test bed of an unducted fan as proposed for the (stillborn) 7J7. GE engine IIRC - fitted to a DC-9 airframe - counter rotating props driven by two free turbines at the back of the engine. Not only supersonic tip speeds, but counter rotating so you have one prop chopping through the vortices of the leading prop.
I never heard it, but people who did said it was indescribably loud and obnoxious. No one cared about the fuel efficiency as it quickly became apparent that the noise made it a non-starter.
Never had the opportunity to hear a B-36, but that would have been interesting
I was at Farnborough when this aspirant mixmaxter was demonstrated. Incredibly, it was sequenced such that it followed some very quiet demo aircraft, including a glider! It was a glorious and still summer's evening - one could hear the birds chirping.- and then the sound demon of the "future to be" appeared. One note, very, very very loud, and most very obnoxious. Memory ( aging) tells me that one set of noise making external devices (blades) were attached to the rotating turbine to go that a away, while the other set of noise makers were attached to the turbine vanes, which - amazingly - were allowed to freely turn in the other direction than that a way. Most unusual to have a part (vane)that is normally static be repurposed as a high speed rotating device- an a critical one as well.. Mind you, GE did amazingly well with the "blucket" aft fan.. Great thread by the way - my music is 1) any engine that continues to provide power to an aircraft that i happen to be inhabiting at the time 2) RR Merlin in Spit and/ or Hurricane and 3) R1830 powered DC-3s ...melody in 36 cylinder harmony