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Is Bell testing a multi-fenestron?

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Is Bell testing a multi-fenestron?

Old 19th Feb 2020, 13:21
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Is Bell testing a multi-fenestron?

Strange design

Bell 429 Fenestron

skadi
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Old 19th Feb 2020, 15:18
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Electric perhaps?
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Old 19th Feb 2020, 20:19
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such a crappy video to tell, but perhaps its just camouflage painting techniques so that you have trouble telling the design from a distance as most auto manufacturers do.
I cant see 4 small fans being anywhere near efficient to carry out the task required.
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Old 19th Feb 2020, 21:14
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My money is on 'fake news', TBH.

Well, I never. Mildly gobsmacked.

Last edited by Bravo73; 20th Feb 2020 at 15:54.
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Old 19th Feb 2020, 22:21
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Originally Posted by GrayHorizonsHeli View Post
such a crappy video to tell, but perhaps its just camouflage painting techniques so that you have trouble telling the design from a distance as most auto manufacturers do.
I cant see 4 small fans being anywhere near efficient to carry out the task required.
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.

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Old 20th Feb 2020, 00:04
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I cant post URLs yet, but verticalmag has the story. 4 electric motors driving fixed pitch blades at varying RPMs
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Old 20th Feb 2020, 00:04
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guess I was wrong, and it's too early for april fools day


https://www.verticalmag.com/news/bel...eOFkXLR7vvPFp0

Last edited by Senior Pilot; 20th Feb 2020 at 01:42. Reason: Add YouTube
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Old 20th Feb 2020, 00:52
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Originally Posted by krypton_john View Post
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"
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Old 20th Feb 2020, 01:59
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Originally Posted by jimjim1 View Post
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
From the Vertical Magazine article...
“In a nutshell, we removed all of the conventional mechanical anti-torque components — which is gearboxes, driveshafts and tail rotor hub and blades — and replaced it with four electric motors and fans,” Eric Sinusas, program director of light aircraft at Bell, told Vertical. “They are fixed-pitch blades and they’re changing rpm constantly.”
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Old 20th Feb 2020, 02:13
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In forward flight at speed, they might even be able to turn them off?

How much bigger is the generator to run them? How long can the battery run them if Gen stops? Total electric failure might be a worry...
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Old 20th Feb 2020, 02:58
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Originally Posted by FH1100 Pilot View Post
From the Vertical Magazine article...
Thanks,
I was a while writing my post and did not re-visit to see if there were relevant updates:-)

Thing is, if an Electric Transmission works for the tail rotor then it will surely work for that other even peskier rotor?

Electric tail rotor is a dead end since if the main rotor is electrified similarly there is no need for a tail rotor at all. Of course Bell and Airbus are on the case. e.g. see Bell Nexus
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Old 20th Feb 2020, 05:24
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if the main rotor is electrified similarly there is no need for a tail rotor at all.
Isaac Newton might have something to say about that. Electric motor mounted on fuselage, drives rotor one way, fuselage must rotate the other way.

The only way around it was like the Djinn, using jet reaction motors on each blade tip. Interesting idea, but horrendously noisy.
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Old 20th Feb 2020, 07:09
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Originally Posted by Ascend Charlie View Post
In forward flight at speed, they might even be able to turn them off?

How much bigger is the generator to run them? How long can the battery run them if Gen stops? Total electric failure might be a worry...
Why generator schould stop? Generator is continously powered from main gearbox. I like this idea and I see many profits from this design.

Last edited by RichiRich; 20th Feb 2020 at 07:28.
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Old 20th Feb 2020, 08:02
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Originally Posted by RichiRich View Post
Why generator schould stop? Generator is continously powered from main gearbox. I like this idea and I see many profits from this design.
Generators can fail, are there redundant gennies or is there battery backup?
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Old 20th Feb 2020, 08:33
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I suspect that there would also be more engine power available to drive the main rotor if not having to send it down the back with the associated loses. When I first read the thread I wondered if they would shut down one or multiple/all of the fans in the cruise. I don't like it visually but guess its an idea that is inevitable given the advances in electric motors, the multiple fans would provide redundancy. And I agree with Charles, main rotor will require anti-torque
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Old 20th Feb 2020, 08:55
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Originally Posted by Bell_ringer View Post
Generators can fail, are there redundant gennies or is there battery backup?
I think there will be more than one generator for powering the tail rotor system.
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Old 20th Feb 2020, 09:03
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I guess it would also reduce noise as most helicopter noise comes from the tail rotor
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Old 20th Feb 2020, 10:17
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Interesting points covered such that it can be turned off in cruise, it can be quieter, etc. It could even be turned off with skids on ground, collective fully down and with mains turning for that extra safety. What I'd like to know is how authoritative is it over the original one, especially with a gusting wind abeam. Being fixed pitch I guess they can spin the motors in reverse if the anti-torque ain't enough. Being electric also makes it susceptible to the water ingress and will need extra environmental testing.
I guess you don't even a long tail anymore and just have a stubby tail with 2 of these things either side of the stabiliser. Computer controlled heading would also a doddle to install.

Having said all that I'm still not convinced.
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Old 20th Feb 2020, 10:32
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Originally Posted by cattletruck View Post
Interesting points covered such that it can be turned off in cruise, it can be quieter, etc. It could even be turned off with skids on ground, collective fully down and with mains turning for that extra safety. What I'd like to know is how authoritative is it over the original one, especially with a gusting wind abeam. Being fixed pitch I guess they can spin the motors in reverse if the anti-torque ain't enough. Being electric also makes it susceptible to the water ingress and will need extra environmental testing.
I guess you don't even a long tail anymore and just have a stubby tail with 2 of these things either side of the stabiliser. Computer controlled heading would also a doddle to install.

Having said all that I'm still not convinced.
More great points, the more you think about this I expect the more advantages will present. It's only a hop, skip and a jump to the Avatar type contra rotating fans. As long as the power source can replenish the batteries quicker than the fans can deplete them the only limit is imagination.
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Old 20th Feb 2020, 10:40
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Would be interested to understand the difference in weight and CoG for this experimental configuration and what the increased surface area does to handling.
A fly by wire tail rotor system does allow for some interesting options for improved stability.
Bell could be onto a good idea, though it could look a bit sexier.
Still, not as fugly as fenestron

Last edited by Bell_ringer; 20th Feb 2020 at 10:41. Reason: bad spelling
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