Originally Posted by
krypton_john
Indeed. I can't imagine any benefit but can think of several detractions for this idea. 4 fans have 4 times as many parts to maintain. Small fans have to spin faster than large fans so are noisy and stressed. 4 fans mean 4 times the risk of something failing and high speed moving parts failing is very dangerous.
As
mindsweeper alluded to if they are electric many of these objections turn into advantages.
Much fewer parts, especially moving parts, and possible redundant operation. Losing a singe motor is not necessarily a catastrophe. I have no idea how the number might work out for such a drive system but it doesn't seem completely ridiculous anymore. If it were possible to get rid of variable pitch blades then such a system would be even more attractive, however that may be straying into the ridiculous
Google for -- helicopter electric tail rotor
Helicopter Electric Tail Rotor
"to meet the requirements of an electric tail rotor drive for the Bell 206A/B helicopter as part of a recent Navy SBIR Phase I Award. "
https://www.navysbir.com/13_1/171.htm
"Bell 206 helicopter ... The drive system is estimated to add 7 to 9 kg to the vehicle while increasing vehicle efficiency, reliability, flyability, and operational performance"