Originally Posted by [email protected]
(Post 10328771)
The advantages seem purely theoretical and you have yet to establish the need for an ETR.
Millions of hours flown with the conventional tail rotor in all aspects of the helicopters versatile roles and the number of TR failures and malfunctions is very small. One crash with an as yet undetermined cause but some form of TR issue and you are proposing ETR as the saviour to that scenario and ignoring the realities of system failure/loss of power in the ETR, not to mention that many of the solutions, such as jelly's, ignore the amount of time many helicopters spend in the hover as opposed to the high speed cruise. Keep on with your blue-sky thinking but I will be surprised if we see ETR in the next 10 years at least. Why do you say I don't consider system failure or loss of power? The motor will meet the required failure rate as will the generation system. They are already multiple redundant systems. All things start as theoretical. However analysis and testing so far have backed up the theory. Do you believe there are no practical advantages to a variable speed rotor? I will continue, thanks, as long as there is a commercial incentive. I don't establish the need, that's done by either regulation or operational requirement. Whether that will happen with an ETR is out of my hands, but so far it has been worthy of attention up to an iron bird. |
Grey horizons, glad you enjoyed. I always feel equally reassured when making consumer purchases with the Inspector #45 tag. Pilots en mass around the world are finally getting their biggest wishes met with the advent of the ETR. They can live with the chronic lower back problems from the cruddy seating, if only the archaic driveshafts and gearboxes would disappear. So...back to this locomotive. We have got power to weight figures for electric motors being flung around the conversation with nary a mention of duty cycle, never mind record in service. Kinda of like sailors arguing where mean sea level sits in 100 foot seas....amusing but pointless. Seeing as we are improving the type , I think it fair to ask the new ETR model to have the ability to hover at max continuous for prolonged periods. So using the aw169 as our testbed once again, this occurs at 1350 hp. So using 15% of Max continuous Q as being TR consumption again........ 200 hp. Sure electronic motor controls have made leaps and bounds in the past couple decades. Complete control of the waveforms operating within the stators of a synchronous motor allowing near perfect efficiency of the principles of electromagnetic induction. Have the ground bound and efficiency obsessed , industrial process industries not innovated and taken advantage of this? Of course they have, sparing no amount of complexity in order to achieve efficiency of power. Lighting fast microprocessors paired with power transistors and resistors, all guided by millions of lines of possibly conflicted computer code.....what kind off fault or failure mode could possibly present itself? So much better than a clunky old driveshaft and gearbox, and there are no bearings to fail in an electric motor. Even If there were , you just use mag/lev tech.(Always use a laser to do the same job a builders string has been doing for the past 10,000 yrs...so much cooler and its called "progress".) After perfect efficiency has been obtained in controlling the repulsive electro magnetic forces between the rotor and stator where do you find your power density gains? Higher voltages through better cooling(.....like all the practical geometries haven't been tried yet) Insulation that doesn't melt or crack, and conductors that don't melt or heat up too much. I know that if we just stretch a little harder cold fusion , super conductors, super steel the weight of feathers are just around the bend....but in the meantime we are stuck with good old copper. Yes even consumer grade products like Tesla and Dyson. Though I feel we are on the cusp of a wave of stc's replacing the 1930's vintage, starter genies still on most helicopters with beer can size , LED backlit , hollow plastic ones accomplishing the same thing. So we need an electric motor based on the best of industrially vetted technology to operate consistently at 200 hp to mirror our max continuous hover missions for SAR or aerial work. Doing a little window shopping I came up with this https://www.ziehl-abegg.com/us/en/pr...maxvent-owlet/. (Pg.44 of 66) A drop in fenestron. Good looking, scimitar-scalloped blades , meets all the euro engineering approvals. 1.4 m diam. Bout right for the back end of a aw169. Power to weight for continuous duty? 50 hp at the svelte weight of 637 kg. Ahh but all that steel fat to be trimmed. Shes's gonna need some beefing up in the motor (4x 50) I think it's a fair trade off to add all that extra copper and substitute steel for aerospace material and call it even ~650 kg....she 'll taxi like a freight train because thats all She'll ever do. I guess until the next invention comes along we are stuck with the practical limit of the electric motor being a quadcopter the size of most windscreens. Send me enough money and I'll build you one to ride in. You can't beat em join em. |
Where is that Like button again..........:)
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Originally Posted by Washeduprotorgypsy
(Post 10329379)
So we need an electric motor based on the best of industrially vetted technology to operate consistently at 200 hp to mirror our max continuous hover missions for SAR or aerial work. Doing a little window shopping I came up with this https://www.ziehl-abegg.com/us/en/pr...maxvent-owlet/. (Pg.44 of 66) A drop in fenestron. Good looking, scimitar-scalloped blades , meets all the euro engineering approvals. 1.4 m diam. Bout right for the back end of a aw169. Power to weight for continuous duty? 50 hp at the svelte weight of 637 kg. Ahh but all that steel fat to be trimmed. Shes's gonna need some beefing up in the motor (4x 50) I think it's a fair trade off to add all that extra copper and substitute steel for aerospace material and call it even ~650 kg....she 'll taxi like a freight train because thats all She'll ever do. But so that the design goal does not move around, what is the weight of the power takeoff & shafting & control & gearboxes for the tail rotor on the AW169 ? And how long do you expect to sit in the hover for at that power ? |
Originally Posted by Washeduprotorgypsy
(Post 10329379)
I guess until the next invention comes along we are stuck with the practical limit of the electric motor being a quadcopter the size of most windscreens. Send me enough money and I'll build you one to ride in. You can't beat em join em. |
The Siemens motor in the Extra 330 LE is rated at 260 kW continuous and is 50kg. But don't let facts get in the way of plucking random numbers out of thin air.
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The 330LE is constructed with light-weight materials and is suitable for 20-minute flights, including take-off, climbing and five minutes of full throttle flight. The electric 20-minuters.......... |
Battery capacity?
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Originally Posted by gevans35
(Post 10329546)
Battery capacity?
What is the weight of conventional tail rotor transmission, power offtake, controls, etc ? |
Originally Posted by [email protected]
(Post 10329539)
that's very useful.......
The electric 20-minuters.......... Now where's that like button |
So at least you now acknowledge the existence of a suitable motor with an appropriate continuous rating. Why haven't Extra elected to use a generator with a prop in the slipstream on it? Cooling issue perhaps with going longer than 20 minutes? It is a small step in the right direction but a very long way from challenging a conventional TR. |
Does one need more than 5 minutes continuous, would 30 minutes at 90% suffice?
I read 20 minutes as battery life, the ETR application would be generator driven. Surely a prop in the slipstream makes no sense... drag? |
Does one need more than 5 minutes continuous, would 30 minutes at 90% suffice? The 20 minute limitation clearly is battery life on the Extra which is why I asked about a generator as you suggest for ETR - if the answer to that is cooling then you would have to keep 'resting' your ETR to stop it overheating. |
Originally Posted by [email protected]
(Post 10329622)
I've spent over an hour in the hover at max continuous, so no, it isn't enough.
The 20 minute limitation clearly is battery life on the Extra which is why I asked about a generator as you suggest for ETR - if the answer to that is cooling then you would have to keep 'resting' your ETR to stop it overheating. I doubt that Leonardo would have developed a prototype ETR and ground tested it if they didn't see any advantage, or think it had a chance of working in flight. |
Originally Posted by [email protected]
(Post 10329607)
hmmm, not quite - 5 mins at max continuous isn't going to cut the mustard in pretty much any helicopter role and a 20 minute max life????
Why haven't Extra elected to use a generator with a prop in the slipstream on it? Cooling issue perhaps with going longer than 20 minutes? It is a small step in the right direction but a very long way from challenging a conventional TR. I'll say again the technology is available. In my personal opinion the research into flux, isolation and thermal flow modelling over the past few years is exceptional. So Crab, there is an ETR that can do everything your mechanical TR can do ( let's face it it would have to otherwise it wouldn't be flyable) Disadvantages Not yet certified. Needs electrical source, changing the safety case for the EPGDS. Advantages Less installation constraints. Simpler installation and maintenance. Power sharing with other systems. Easily varied rotor speed. For a number of years I looked at a variable speed tail rotor, but mechanically the penalty was just too much. The ETR changes the equation. ... I admit that I don't know whether it changes it enough, time will tell. |
Originally Posted by dClbydalpha
(Post 10329774)
Advantages
https://publicapps.caa.co.uk/docs/33/CAPAP2003_01.PDF CAA PAPER 2003/1 |
JimJim1,
The twin tail rotor concept was thought of very many years ago. From a purely academic/theoretical point of view, a tail rotor at each end of the helicopter would be a better design. But it wouldn't be convenient. Early designers realised that the single tail rotor at the rear end was a necessary compromise. |
DcL - I'll take your word for the advancement of the technology - I'm just a guy who flys helicopters for a living not a boffin. but given these constraints
Disadvantages Not yet certified. Needs electrical source, changing the safety case for the EPGDS. |
I have always liked this method of implementing twin tailrotors. They're not mounted on the tail, admittedly.
I don't know whether they provide redundancy in this case, but as a concept I don't see why it couldn't. |
That machine isn't very practical, for a number of reasons discussed here a long time ago.
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Originally Posted by [email protected]
(Post 10329971)
DcL - I'll take your word for the advancement of the technology - I'm just a guy who flys helicopters for a living not a boffin. but given these constraints how close are we really to seeing ETR in production?
The thing I see is that technology is advancing so fast that the move to hybrid and all electric may mean it's not worth the short term investments for just an ETR. Hence my comments about the next 10 years. As I say, my opinion only . |
I have been reliably informed the UH-60 Blackhawk Tail Rotor can demand as much as 800 Horsepower. How much would a 24VDC Electric Motor weigh in order to provide that much output? What kind of gearing/gearbox/shafting would it require? What Electric Load would it have to have feeding it....and what would the Generator/Alternator weigh for that? Where would you place the Electric Motor along the Tail Boom not to have a CG Issue? Let's carry this a bit further......what size motor would be required to power the CH-47F's Aft Rotor considering it already has two 4700 shp Engines driving the rotor system now. |
How much would a 24VDC Electric Motor weigh in order to provide that much output? What kind of gearing/gearbox/shafting would it require? What Electric Load would it have to have feeding it....and what would the Generator/Alternator weigh for that? 800 HP is close to 600 kVA. A 250kVA B787 generator weighs a bit less than 300 lbs IIRC. Motors and generators are similar machines, so figure something like 600 lbs, unless somebody comes up with better technology. You should not need a gearbox for the UH60 tail rotor speed range with an electric motor. you would need a big honking generator to run that 800 HP motor. |
I think SAS wrote “ as much as.....” so that 800 number would be treated as a peak value, not steady state. |
Brother Dixson is correct that the demand would vary with the amount of Tail Rotor Thrust being applied or in the Chinook example what the Aft Rotor Head demand range could be from setting stationary on the Ground to lifting at Max Allowable Gross Weight.
If you think you need a big generator for the Hawk Tail Rotor....the Chinook application would be really huge! |
Chinook is a different ball game, as is V22, although large hybrid VTOL multi motor tilt wing transport aircraft are suggested in various NASA articles.
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I expect James Dyson could find a solution.:)
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...Dyson sucks...
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But nothing sucks like an Electrolux.
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If someone did come up with a bolt on spin recovery system (not a parachute!) for existing helicopters, would the industry adopt it? Here is one hypothetical scenario: Bolt on apparatus with no or min adaptions required to the air frame. Derigable. Operates independently Weight 30 kg (moving CoG rear of mast.) Engauges automatically Low maintenance No other use but for countering the high speed yaw on light and medium helicopters. At what price would such a safety device be considered too expensive? For reference, we saw that despite the obvious benifits of crash resistant fuel cells for the r44, they were not widely retrofitted as a matter of free choice, due to cost. mjb |
30 kg on the tail would be a sizeable CG change - we used to put 10kg there to counter a massive camera on the nose. Without a camera, and 30 kg on the tail - fuggeddabardit!
Automatic engagement just invites undemanded deployment - that would be exciting. No use for it, other than the 1:1million chance of a tail fail - no thank you, rather have 30kg more payload and a workable CG for the 999,999 other flights. |
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