Eurocopter X3 hybrid
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Faireys, Flettners, and F----ps
It'd be great if people would just get their facts straigt. Obviously the 1936 Flettner 185 was an autogyro (even if the motor could engage the rotor for jump-start). The Fairey Rotodyne was a gyroplane, which is just an autogyro with tip jets. The same was true the (conspicuously named) VFW H3 from 1969. Keeping with the nerd theme, the X3 is more like the Lockheed AH-56 Cheyenne compound helicopter. The clever bit, though, is apparently that they've combined this design with a variable-RPM rotor like the Boeing Hummingbird. That was the key missing ingredient for high speed. Insofar, it's fair to assume that Eurochopper's goal to provide high speed at less cost and complexity than for a tiltrotor, might be quite achievable.
And yes, I expect them to introduce shrouds, and to disengage the props while on ground. And to make the actual product better looking. But those are details. And anyway, I've recently flown on a plane with two open propellers. Guess what - they only started turning after we were all inside!
BTW, one has to hand it to Lewis Page, he's always a good laugh...
And yes, I expect them to introduce shrouds, and to disengage the props while on ground. And to make the actual product better looking. But those are details. And anyway, I've recently flown on a plane with two open propellers. Guess what - they only started turning after we were all inside!
BTW, one has to hand it to Lewis Page, he's always a good laugh...
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After watching the video, it looks like the X3 aero and structures guys will need to do some more work before it flies again. The oscillations in the tail surfaces and stub wings looked pretty severe while it was just flying in hover. I would suspect the problem will only get worse at speed.
I'm not sure shrouding the props would enable safe rotors running (dis)embarkation - still too easy to contact the blades. But perhaps there will be a clutch or failing that, just no rotors running turnrounds allowed. After all, you don't often get into an airliner whilst the engines are running!
The wobble looks to me more like autopilot-induced - perhaps the loop gains need turning down a bit to cater for structural flexing?
HC
The wobble looks to me more like autopilot-induced - perhaps the loop gains need turning down a bit to cater for structural flexing?
HC
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Pretty it isn´t, but i guess as some say here it´s a technology demonstrator.
And yes quite a bit of the shakes happening.
Remember the Piasecki speedhawk demonstrator that came out some years ago as well?
It was a pusher with the Seahawk as a baseframe.
Wonder what happened to that?
Piasecki X-49A Speeedhawk Compound Helicopter: 250-mph Black Hawk?
And yes quite a bit of the shakes happening.
Remember the Piasecki speedhawk demonstrator that came out some years ago as well?
It was a pusher with the Seahawk as a baseframe.
Wonder what happened to that?
Piasecki X-49A Speeedhawk Compound Helicopter: 250-mph Black Hawk?
Would anybody here want their anti-torque to run through clutches? Would you like to be able to de-clutch your tail rotor for ground ops? Not for me, thanks!
HeliComparitor,
I am not sure the oscillations are from the autopilot. The rotor and fuselage look quiet while the tail and wings shake. I would have said they were tuned to the 1P main frequency. Just my guess.
I believe the speedhawk was sold. There was a thread on it.
-- IFMU
HeliComparitor,
I am not sure the oscillations are from the autopilot. The rotor and fuselage look quiet while the tail and wings shake. I would have said they were tuned to the 1P main frequency. Just my guess.
I believe the speedhawk was sold. There was a thread on it.
-- IFMU
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We also have been working on this for sometimes and predict to take Russia, China and India markets so dont believe that only America and Eurocopter is going for this.
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The F27 had a clutch one one engine to disconnect the prop and allow it to be used in what IIRC was called 'hotel mode' to provide bleed air and power instead of an APU.
EC's and the final Russian concepts are certainly far less hazardous than a tilt rotor and lighter than Sikorsky's designs.
EC's and the final Russian concepts are certainly far less hazardous than a tilt rotor and lighter than Sikorsky's designs.
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Competition fosters development. Perhaps conceptual engineering will return to the VTOL arena.
The challenges of developing an aircraft with high-speed and VTOL capability will be formidable. However, with damn little humility, I would suggest that the participants solve some of the specific and obvious limitations, THEN apply them to a craft.
Dave
The challenges of developing an aircraft with high-speed and VTOL capability will be formidable. However, with damn little humility, I would suggest that the participants solve some of the specific and obvious limitations, THEN apply them to a craft.
Dave
Avoid imitations
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It'd be great if people would just get their facts straigt. Obviously the 1936 Flettner 185 was an autogyro (even if the motor could engage the rotor for jump-start). The Fairey Rotodyne was a gyroplane, which is just an autogyro with tip jets.
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IFMU,
"Would anybody here want their anti-torque to run through clutches?"
On most every rotorcraft I can think of, both main and tail rotor drives run through a type of clutch. That clutch is usually a roller or sprag type clutch.
As for friction clutches, the main lift fan on the F-35B (VTOL fixed wing aircraft) is engaged/disengaged/driven through a massive CRC friction clutch pack. The lift fan on this VTOL aircraft is a much more critical application than a rotary wing tail rotor drive.
Of course, having noted the above exceptions, I would agree with you that any friction type clutch device in an aircraft drivetrain presents inherent reliability/fault tolerance issues. And in my opinion, such devices should be avoided, since by nature they cannot be designed with adequate fault tolerance for any aircraft primary drivetrain application.
Regards,
riff_raff
"Would anybody here want their anti-torque to run through clutches?"
On most every rotorcraft I can think of, both main and tail rotor drives run through a type of clutch. That clutch is usually a roller or sprag type clutch.
As for friction clutches, the main lift fan on the F-35B (VTOL fixed wing aircraft) is engaged/disengaged/driven through a massive CRC friction clutch pack. The lift fan on this VTOL aircraft is a much more critical application than a rotary wing tail rotor drive.
Of course, having noted the above exceptions, I would agree with you that any friction type clutch device in an aircraft drivetrain presents inherent reliability/fault tolerance issues. And in my opinion, such devices should be avoided, since by nature they cannot be designed with adequate fault tolerance for any aircraft primary drivetrain application.
Regards,
riff_raff
Received the latest HeliData ( HeliTech issue ) this morning.It has quite a good technical description and explanation of the X3 cubed ,confirming that the main rotor does slow down in high speed flight .The demonstrator has a simplex autopilot with manual reversion and mechanical flight controls ,apparently all part of a Eurocopter desire to make the eventual production aircraft commercially affordable.
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IMHO we have here two of the bravest/daftest Test Crew doing a proper "best aircraft I've ever flown" interview after.
... After what though. I reckon in the long shots I saw an inch (25mm) amplitude at the prop boss and possibly more than that at the wing tip. The rotor start-up seemed normal until ground resonance, when I notice they cut the video, but in later shots there are several shakes new to the Dauphin.
The Rotodyne had several design advantages over this in terms of driving vibration ... and still cracked all over.
... After what though. I reckon in the long shots I saw an inch (25mm) amplitude at the prop boss and possibly more than that at the wing tip. The rotor start-up seemed normal until ground resonance, when I notice they cut the video, but in later shots there are several shakes new to the Dauphin.
The Rotodyne had several design advantages over this in terms of driving vibration ... and still cracked all over.
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Dear Rengineer, it sure would be great if people, as you say, could get their facts straight..
A HELICOPTER with the ability to hover for an extended period of time does not become an “autogyro with ability to jump-start” just because you say so..
A HELICOPTER with the ability to hover for an extended period of time does not become an “autogyro with ability to jump-start” just because you say so..
"Flettner then turned in 1935, to the design of the two-seat FL-184, which was similar to an autogyro but had part of the power applied to the rotor during normal forward flight."
"Flettner then took the opportunity that year to explore another system in the design designated FL-185, which could be operated as a helicopter or autogyro by clutching or un-clutching the rotor to the engine gearbox. Cowled and with a frontal cooling fan, a Siemens-Halske Sh 14A 140 h.p. radial engine was mounted in the nose of the FL-185 with a gearbox behind it. From this gearbox, the drive was taken to the three-bladed wooden rotor and also to two variable-pitch airscrews mounted on outrigger arms extending from the fuselage sides.
These airscrews (designed by Flettner as possibly the first with reverse pitch capability) used the full power of the engine to provide forward thrust when the machine acted as an autogyro. When, however, power was applied to the main rotor for helicopter flight, the pitch of the auxiliary airscrews was altered to give thrust in opposite directions and thereby counteract main rotor torque. The amount of anti-torque thrust was automatically governed by a planetary gear unit according to the torque transmitted to the main rotor. Also, the pilot's rudder pedals could act on the anti-torque airscrews as needed to control turns."
______________________
"This machine was the closest a German design came to the Sikorsky system, but only one example of it (D-EFLT) was built. Furthermore, the FL-184 was abandoned prematurely since, by January 1938, Flettner had decided that this new twin rotor system then being tested promised a better power efficiency by converting total engine power into lifting force as far as possible. At the same time this permitted a more compact arrangement. Flettner's quite different intermeshing contra-rotating synchronized rotor scheme ensured that one rotor inherently balanced the torque of the other."
from Aeroplane Monthly, October 1975
Dave
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Svenestron,
You are correct. You only discussed the FL-185.
I was wrong in assuming that the discussion was about both craft, after reading "Obviously the 1936 Flettner 185 was an autogyro."
Dave
Edit:
Information on the Flettners;
The FL-184 (autogyro with partially powered rotor) flew in November and December of 1936. The FL-185 (helicopter, which was the intended successor to the FL-184) first flew in the summer of 1937.
Information relevant to the Eurocopter X3;
"Hovering proved quite easy. Whilst the FL-185 V1 behaved beautifully at speeds under 65 km/h (40 mph), speeds in excess of this were not possible as the rearward thrusting airscrew would begin to vibrate badly."
You are correct. You only discussed the FL-185.
I was wrong in assuming that the discussion was about both craft, after reading "Obviously the 1936 Flettner 185 was an autogyro."
Dave
Edit:
Information on the Flettners;
The FL-184 (autogyro with partially powered rotor) flew in November and December of 1936. The FL-185 (helicopter, which was the intended successor to the FL-184) first flew in the summer of 1937.
Information relevant to the Eurocopter X3;
"Hovering proved quite easy. Whilst the FL-185 V1 behaved beautifully at speeds under 65 km/h (40 mph), speeds in excess of this were not possible as the rearward thrusting airscrew would begin to vibrate badly."
Last edited by Dave_Jackson; 5th Oct 2010 at 06:49. Reason: Added past fact and future concern.
Chief Bottle Washer
Dave_Jackson & Svenestron,
The thread is about the Eurocopter X3: let's try to keep it on topic
The thread is about the Eurocopter X3: let's try to keep it on topic
IFMU,
On most every rotorcraft I can think of, both main and tail rotor drives run through a type of clutch. That clutch is usually a roller or sprag type clutch.
As for friction clutches, the main lift fan on the F-35B (VTOL fixed wing aircraft) is engaged/disengaged/driven through a massive CRC friction clutch pack. The lift fan on this VTOL aircraft is a much more critical application than a rotary wing tail rotor drive.
Regards,
riff_raff
On most every rotorcraft I can think of, both main and tail rotor drives run through a type of clutch. That clutch is usually a roller or sprag type clutch.
As for friction clutches, the main lift fan on the F-35B (VTOL fixed wing aircraft) is engaged/disengaged/driven through a massive CRC friction clutch pack. The lift fan on this VTOL aircraft is a much more critical application than a rotary wing tail rotor drive.
Regards,
riff_raff
Agreed that all helicopters that I have flown (only about 4 types) or I am familiar with (a few more) have an overrunning clutch between the engine(s) and the rest of the drivetrain. This serves to disconnect the engine should it fail, allowing the pilot to autorotate. They work great. When the engine fails, the torque goes away, yet the tail rotor still spins, allowing full yaw control. This is a lot different than a clutch between the main rotor and the source of anti-torque, as proposed in the X^3. If that clutch fails, you can still have torque on the main rotor, but you have no anti-torque. This is generally bad.
The F-35B is really cool. It also has ejection seats, so if the clutch fails in hover you have another option. To me that makes the clutch a lot less critical.
The failure modes of a clutch located between the main and tail rotor of the X^3 would be bad, as they would be bad on a more conventional helicopter as well.
-- IFMU
IFMU yes, on reflection I agree with your point on clutches in anti-torque components! Looks like it will be no RRTR then!
As for the wobble, the fuselage is resonating, but I suppose we can't tell whether the excitation comes from rotor imbalance, pulses of downwash as the rotor blade passes, or flight control input (from the AFCS). I still think its most likely the last one.
HC
As for the wobble, the fuselage is resonating, but I suppose we can't tell whether the excitation comes from rotor imbalance, pulses of downwash as the rotor blade passes, or flight control input (from the AFCS). I still think its most likely the last one.
HC
The AS-316C Allouette III utilizes a friction clutch that is manually engaged and disengaged by the pilot. I don’t believe that there have been any significant issues with any failures of this system over the years. The duel thrust system on the X3 could actually provide a level of tail rotor redundancy if properly integrated.
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IFMU,
I watched the X3 video again, but did not see or hear any mention of the prop drives having a decouple/clutching function from the MR drive.
The video has a nice see-through CAD image of the MRGB input bevel gear drives that I captured and enlarged. Couldn't see any clutches in that image either. Just a 2-way power split at the first bevel mesh, with two more bevel meshes changing the shaft angle and providing the necessary offset to pass the driveshaft inside the stub wing box. There is also another bevel gearbox at each prop nacelle, but I don't think there's any clutching device located there.
There was mention of slowing the MR at high forward speeds, but I'd speculate that this is accomplished simply by reducing engine speed. Those RTM322 engines can probably be run at 80% (or less) of rated speed without encountering combustion stability issues.
riff_raff
I watched the X3 video again, but did not see or hear any mention of the prop drives having a decouple/clutching function from the MR drive.
The video has a nice see-through CAD image of the MRGB input bevel gear drives that I captured and enlarged. Couldn't see any clutches in that image either. Just a 2-way power split at the first bevel mesh, with two more bevel meshes changing the shaft angle and providing the necessary offset to pass the driveshaft inside the stub wing box. There is also another bevel gearbox at each prop nacelle, but I don't think there's any clutching device located there.
There was mention of slowing the MR at high forward speeds, but I'd speculate that this is accomplished simply by reducing engine speed. Those RTM322 engines can probably be run at 80% (or less) of rated speed without encountering combustion stability issues.
riff_raff
riff_raff,
I either read in an article somewhere, or read it on pprune, that clutched props were the answer to passenger entry & exit. I would have said I heard it on the video, but I think you are saying it is not there. I would agree there are no clutches on their demonstrator. Makes sense to keep the demonstrator simple and work out the details later.
-- IFMU
I either read in an article somewhere, or read it on pprune, that clutched props were the answer to passenger entry & exit. I would have said I heard it on the video, but I think you are saying it is not there. I would agree there are no clutches on their demonstrator. Makes sense to keep the demonstrator simple and work out the details later.
-- IFMU