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Bell's Electrically Distributed Anti-Torque (EDAT)

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posted on Feb, 20 2020 @ 12:09 AM
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www.verticalmag.com...

“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.”

The system has been installed on a Bell 429 demonstrator aircraft at Bell’s facility in Mirabel, Quebec, and began flight testing on May 23, 2019. Since then, the program has completed about 25 flight hours, with the aircraft gradually expanding its flight envelope.




Essentially replacing the tail rotor with four electric variable-speed fans. Should be less mechanically complex, so reliability/safety would be increased. Quite clever, actually.
edit on 20-2-2020 by RadioRobert because: (no reason given)




posted on Feb, 20 2020 @ 03:46 AM
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Less complex than NOTAR?



posted on Feb, 20 2020 @ 07:37 AM
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a reply to: Blackfinger

Probably roughly the same. In theory, it could be less. They're stealing shaft power and turning it into electricity. NOTAR still runs a shaft to drive a fan, albeit a shorter and lighter shaft than drives a tail rotor.
So basically the equivalent of a.big alternator.driving big electric fans for a small radiator or trying to run a transmission that drives a larger shaft -powered fan to do it. In theory, the electric fans/large alternator is simpler, lighter, and easier to fix (simply swap out components).

Right now they are just validating the concept. I imagine you could do it with two or three larger fans, make the tail assembly lighter, etc For now, it's just "can this work", and the answer appears to be yes. Turning the theoretical advantages into reality from the paper math is frequently more difficult than anticipated. So, we'll see...

I have some old Hughes and McDD brochures somewhere. Including some NOTAR stuff. I'll try to remember to scan it and upload it if I run across them if there is interest. Or next time I'm out by MD I can drop in and ask them if they've got any freebies.I think all the people I know are still at Boeing,.not MD.



posted on Feb, 20 2020 @ 09:29 AM
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I’ve always wondered why NOTAR isn’t used on Little Birds in the 160th Special Operations Aviation Regiment. It seemed to have big advantages such as lower noise level, better safety for soldiers on the ground and possibly less vulnerability to ground fire a la Blackhawk Down.



posted on Feb, 20 2020 @ 10:35 AM
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a reply to: Scapegrace

I don't know the decision making process, and I'd think the NOTAR would be great down in the weeds where you could put the tail boom into the brush and branches without worrying much about it. Might be a little better hot and high. I'd guess that the weight and range penalty on the 520 probably limits the interest.



posted on Feb, 20 2020 @ 11:27 AM
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a reply to: Blackfinger

i would say more complex

notar - basically has a ducted rotar where the alternator on this concept is then just ducting to direct the air flow . the tail is just a tube

this electric hybrid - has the take off from the gearbox - then alternator , powercables running to the tail unit - 4 fans with 4 motors - and ECUs to control power distribution



posted on Feb, 20 2020 @ 11:31 AM
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i have a question - :

if both engines failed on this - would the main rotor rotation still drive teh alternator as the pilot attempts to do an autorotation emergency landing ?



posted on Feb, 20 2020 @ 11:43 AM
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a reply to: ignorant_ape
If the aircraft has a freewheeling unit for the engines, using to rotor to drive the main gearbox in an auto-rotation should still power the generators and thus this tail rotor configuration.



posted on Feb, 20 2020 @ 11:49 AM
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a reply to: ignorant_ape

Don't need a tail rotor to autorotate.


RE: complexity
I think the greatly simplified gearbox more than makes up for the additional electric engines. Also, the NOTAR tail still has mechanical elements to control the thruster. I've got some 520 pics from a couple years ago at their open house. I'll try to find those, too.
edit on 20-2-2020 by RadioRobert because: (no reason given)



posted on Feb, 20 2020 @ 11:53 AM
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a reply to: JIMC5499

You'll get torque if it's driving gears to generate electricity. And it sucks energy from the rotor blades to do it. Not sure that'd be the preferred method...



posted on Feb, 20 2020 @ 12:26 PM
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originally posted by: ignorant_ape
i have a question - :

if both engines failed on this - would the main rotor rotation still drive teh alternator as the pilot attempts to do an autorotation emergency landing ?


Afaik (as mentioned) the rotor is connected using freewheeling unit, can not drive the engine. You don't really want it to drive anything anyway, create any torque.



posted on Feb, 20 2020 @ 12:40 PM
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As soon as you pull up on the collective to land, you want that tail rotor working. In other aircraft there is a direct mechanical linkage between the main gearbox and the tail rotor. On this aircraft the main gearbox would be driving the generators as soon as the collective is pulled and should provide power to the tail rotor motors.



posted on Feb, 20 2020 @ 01:45 PM
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a reply to: JIMC5499




As soon as you pull up on the collective to land, you want that tail rotor working

Won't matter when it's free wheeling. I freely admit all of my extremely limited rotary wing time is all bootleg, but there's no reason for it. When people practice autorotation, it's nice (and safer) to have yaw authority using the tail rotor, and when you apply power at the end of practicing, you want the tail rotor to offset the sudden torque. But with no power, this is not something that happens in freewheeling decent, regardless of the collective setting. Depending on your forward speed, you might have enough yaw-stability with the surfaces.



posted on Feb, 20 2020 @ 02:51 PM
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a reply to: RadioRobert
Frewheeling (at least on the helicopters that I've worked on (SH-3H, CH-53, SH-60B & SH-2) is for the engines only. They allow the rotor to drive the Main gearbox using the air resistance on the rotor blades during the start of the auto rotation. The flare part of the auto-rotation uses the momentum of the blades to generate enough lift to land safely. The Main Gearbox is being driven the entire time or else you would lose electrical and hydraulic power. A conventional tail rotor or the type discussed here would continue to operate.



posted on Feb, 20 2020 @ 04:01 PM
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a reply to: JIMC5499

The tail rotor still turns on a typical helicopter because the rotor is turning. It is mechanically linked by the transmission even though both are "free" of the engine. What I'm saying is that the tail rotor is not necessary in autorotation. The collective blade pitch makes no difference in that need (unless, like in practice, you are slowing the blades enough that the engine RPM becomes higher than the blades rpm -- in an engine out scenario, this will never be true. Blade RPM will always be greater than zero engine RPM, and virtually no torque exists).

If the tail rotor fails completely, one can still autorotate by making sure blade RPM is higher than engine RPM so you are free wheeling, though yaw authority may be substantially reduced as speed decreases.

I'm not sure that stealing rotor RPM by having the electric generation tied to the rotor as opposed to the engine is the plan. I'd be surprised if it is, but it's possible. Since it's likely to be a short flight post-engine failure, the battery might even be the answer.



posted on Feb, 20 2020 @ 04:07 PM
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Re-reading the article, I've got this:

The electrically distributed anti-torque (EDAT) system is composed of four small fans within a tail rotor shroud in an offset two-by-two pattern. Each of the rotors contains four blades, and they are powered by four separate motors, with the electrical energy provided through generators driven by the turbine engines.

That would seem to indicate the shaft won't be turning if the engines aren't turning. So no new electricity. The answer is either battery power or no/limited yaw-authority on descent. Since no torque is being created engine out, the battery might well be the answer.



posted on Feb, 21 2020 @ 10:32 AM
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In AW&ST



But fitment of the EDAT has required significant modifications from nose to tail. Rather than mechanically actuated anti-torque controls, the pedals now provide commands to a fly-by-wire system that controls the output of the four fans. The air-cooled fan motors are powered by a liquid-cooled generator running off the aircraft’s two Pratt & Whitney Canada PW207 turbines. Wires connecting the generator with the motors run down the tail boom, where the tail rotor shaft once sat.



posted on Feb, 24 2020 @ 04:51 PM
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Interesting idea, but I wonder if something along the lines of a NOTAR driven by an electrically powered fan(s) might prove even better for weight saving? Generator efficiency and electric motor developments are moving ahead at quite a pace so this might be possible.



posted on Feb, 26 2020 @ 05:12 PM
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a reply to: RadioRobert

I am sure the battery would provide enough juice for an auto-rotation. They can't suck that much juice for those last few seconds.




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