Future rotorcraft control systems
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Location: Huntsville AL
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IFMU,
I would actually like to have my old carburetor and distributor back! but that may be just me. I agree that fly by wire could do the job quite well but I have one real issue with the whole electronics method. You just can't see when it's broke! I work with fly by wire systems everyday and even with the self diagnostics built in, troubleshooting can be a real nightmare. In more complex and expensive helicopters fly by wire could work and does today. When you are going to trust the control of an aircraft to something we must periodically inspect it to see that it is in working order. With a mechanical system you can normally see any anomalies that could cause you harm on the next flight but it is very difficult to see a short in a wire bundle or a bad contact somewhere in a cannon plug. So to be sure the system is ok we build in self tests and parameters that will warn us of what we can't see. Now we have just added another expense to the whole shebang and more complexity. Our simple off the shelf solid state fly by wire system is now a full blown computer control system that cost much more money and I'd be willing to bet much more difficult to certify. So again for the big expensive aircraft this is justified but for the R22 or comparable small aircraft it becomes costly ...maybe too costly. So back to square one. If we can get the same job done with a relatively simple spider with some weights and a couple springs mounted to the rotor head then why not. I suppose Graviman is right...one step at a time as there are still some things to work out. But even if it never comes to be it is still good exercise for the brain!
Max
I would actually like to have my old carburetor and distributor back! but that may be just me. I agree that fly by wire could do the job quite well but I have one real issue with the whole electronics method. You just can't see when it's broke! I work with fly by wire systems everyday and even with the self diagnostics built in, troubleshooting can be a real nightmare. In more complex and expensive helicopters fly by wire could work and does today. When you are going to trust the control of an aircraft to something we must periodically inspect it to see that it is in working order. With a mechanical system you can normally see any anomalies that could cause you harm on the next flight but it is very difficult to see a short in a wire bundle or a bad contact somewhere in a cannon plug. So to be sure the system is ok we build in self tests and parameters that will warn us of what we can't see. Now we have just added another expense to the whole shebang and more complexity. Our simple off the shelf solid state fly by wire system is now a full blown computer control system that cost much more money and I'd be willing to bet much more difficult to certify. So again for the big expensive aircraft this is justified but for the R22 or comparable small aircraft it becomes costly ...maybe too costly. So back to square one. If we can get the same job done with a relatively simple spider with some weights and a couple springs mounted to the rotor head then why not. I suppose Graviman is right...one step at a time as there are still some things to work out. But even if it never comes to be it is still good exercise for the brain!
Max
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"Whoops! I should go yank out my fuel injection and electronic ignition out of my car, slap in a carb and distributor."
Hehehe, i drive a mechanical injection pump diesel - what's electronic ignition?
Seriously though you have a point - I am an oddball in that i have degree quals in mechanical and electronics. I just believe that you only turn to electronics (with potentially complex modes of failure) when you can't get there mechanically. Carbs are actually a good example due to emissions, but you should see the hassle AMTL are going through to convice the world about steer-by-wire (No, i wasn't totally convinced either). Ask Nick how much the FBW program is costing Sikorsky sometime...
"I suppose Graviman is right...one step at a time as there are still some things to work out. But even if it never comes to be it is still good exercise for the brain!"
I've learnt some good stuff - it's good to explore new concepts. I think my final conclusion has to be that the best control system for a light heli is:
1. Lockheed gyro augmentation of rigid (or do i mean articulated
) rotor system cyclic pitch.
2. Motor feedback to collective pitch, as part of (R22) auto throttle to assist the pilot make fast but safe decisions.
3. Non-augmented pedal system, primarily to keep the tail rotor forces sensible (use top rearward rotation to stop occasional R22 tail rotor vortex ring).
These ground rules would be applicable to any light heli, regardless of config. The whole point is to enable the design of a light heli that really is easy to fly - sort of a 21st century S300 if you like. The whole thing comes from my frustration at realising how much it would cost to make me a proficient heli pilot
- in the mean time i'm going back to gliders! 
Mart
[Edit: it's a plank driver thing, typing and thinking at the same time...
]
Hehehe, i drive a mechanical injection pump diesel - what's electronic ignition?
Seriously though you have a point - I am an oddball in that i have degree quals in mechanical and electronics. I just believe that you only turn to electronics (with potentially complex modes of failure) when you can't get there mechanically. Carbs are actually a good example due to emissions, but you should see the hassle AMTL are going through to convice the world about steer-by-wire (No, i wasn't totally convinced either). Ask Nick how much the FBW program is costing Sikorsky sometime...
"I suppose Graviman is right...one step at a time as there are still some things to work out. But even if it never comes to be it is still good exercise for the brain!"
I've learnt some good stuff - it's good to explore new concepts. I think my final conclusion has to be that the best control system for a light heli is:
1. Lockheed gyro augmentation of rigid (or do i mean articulated
) rotor system cyclic pitch.2. Motor feedback to collective pitch, as part of (R22) auto throttle to assist the pilot make fast but safe decisions.
3. Non-augmented pedal system, primarily to keep the tail rotor forces sensible (use top rearward rotation to stop occasional R22 tail rotor vortex ring).
These ground rules would be applicable to any light heli, regardless of config. The whole point is to enable the design of a light heli that really is easy to fly - sort of a 21st century S300 if you like. The whole thing comes from my frustration at realising how much it would cost to make me a proficient heli pilot
- in the mean time i'm going back to gliders! Mart
[Edit: it's a plank driver thing, typing and thinking at the same time...
]
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Graviman,
We must hand it to you! You settled on the failed gyro system from an experimental helicopter that killed its crew, added an unbuilt and unproven system to bottom the collective and create a hazard all of its own, and finished with a direction of spin for the tail rotor that COSTS rotor control!
Not too shabby, what comes next, nuclear power as a lunch-time hobby?
We must hand it to you! You settled on the failed gyro system from an experimental helicopter that killed its crew, added an unbuilt and unproven system to bottom the collective and create a hazard all of its own, and finished with a direction of spin for the tail rotor that COSTS rotor control!
Not too shabby, what comes next, nuclear power as a lunch-time hobby?
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RJSquirrel,
"...the failed gyro system from an experimental helicopter that killed its crew"
The gyro system was extremely well proven on CL475 and 186 before AH56. The AH56 problems came when DOD insisted on spec that pushed disk loading to the point of cambered aerofoil divergence (thanks Lu). As far as i know both 186s and CL475 were finally destroyed in a hangar fire, but had no serious flight incidents. Please correct if wrong.
Don't forget light helis don't currently have ANY cyclic augmentation. I have only ever hovered a teetering machine, so couldn't say how much easier an articulated head is (open to offers
), but I'll bet the S300 still won't hover hands off like the CL475 did (even with an offset CG!).
"added an unbuilt and unproven system to bottom the collective and create a hazard all of its own"
Well that's engineering, and is why we do system FMECAs. The proposed system does strike me as the most fail safe method to reduce autorotation incidents, but would naturally take development. As a final say the pilot (or instructor) can just switch it off, like the auto-throttle.
"and finished with a direction of spin for the tail rotor that COSTS rotor control!"
The XH-40 (prototype UH-1) and the AH56 (amongst many others) had the prototype tail rotor rotating top forwards, but later changed to top rearwards for improved controlability. As i understand it the rotor is always countering main rotor wake, so suffers less from vortex ring state. I'll eat crow if i need to here.
Out of interest which way does it turn on AS350?
Mart
"...the failed gyro system from an experimental helicopter that killed its crew"
The gyro system was extremely well proven on CL475 and 186 before AH56. The AH56 problems came when DOD insisted on spec that pushed disk loading to the point of cambered aerofoil divergence (thanks Lu). As far as i know both 186s and CL475 were finally destroyed in a hangar fire, but had no serious flight incidents. Please correct if wrong.
Don't forget light helis don't currently have ANY cyclic augmentation. I have only ever hovered a teetering machine, so couldn't say how much easier an articulated head is (open to offers
), but I'll bet the S300 still won't hover hands off like the CL475 did (even with an offset CG!). "added an unbuilt and unproven system to bottom the collective and create a hazard all of its own"
Well that's engineering, and is why we do system FMECAs. The proposed system does strike me as the most fail safe method to reduce autorotation incidents, but would naturally take development. As a final say the pilot (or instructor) can just switch it off, like the auto-throttle.
"and finished with a direction of spin for the tail rotor that COSTS rotor control!"
The XH-40 (prototype UH-1) and the AH56 (amongst many others) had the prototype tail rotor rotating top forwards, but later changed to top rearwards for improved controlability. As i understand it the rotor is always countering main rotor wake, so suffers less from vortex ring state. I'll eat crow if i need to here.
Out of interest which way does it turn on AS350?
Mart
Last edited by Graviman; 29th Jun 2005 at 18:51.
