Raptor Composite Aircraft

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Kyle Boatright

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If it was my plane I would take a large step back and fit tubes and bell cranks.
Yep. Or properly brace the hard points for the previous cable actuated system. That woulda been easy, particularly for a prototype where today's solution doesn't need to be the final solution.
 

Rik-

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My day job is with hydraulic machinery. Trust me, I know a vast number of ways that it can go wrong, some of which I've been told are not possible! I would never put hydraulic primary controls on my own small aircraft and I naturally repel water! I don't need to overthink this...

1. It leaks. You need the surface to be in a definite position relative to the stick. That requires active feedback or you are up a very smelly creek without a paddle in short order. That is beyond a simple system. It needs a servo system. Skip that, you can have the stick on a stop, the surface can, and will, drift anywhere. The only variable being the speed at which it happens.

A cable system is several orders of magnitude easier to accomplish. Someone who cannot design a simple cable system has a zero chance of designing a hydraulic system.
Your listing fear not reality. Leaks, the engines leak, the tires leak and even the windows leak. I don’t know what type of hydraulics you deal with but I manufacture my own hydraulic cylinders and I don’t have leaks especially if someone doesn’t step upon a hose. There’s an oil pressure hose on the motor, are we so fearful that it will leak that we don’t use one? Certainly not.

A simple hydraulic system can be made really easy, cheap and light.
 

AdrianS

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My day job is with hydraulic machinery. Trust me, I know a vast number of ways that it can go wrong, some of which I've been told are not possible! I would never put hydraulic primary controls on my own small aircraft and I naturally repel water! I don't need to overthink this...

1. It leaks. You need the surface to be in a definite position relative to the stick. That requires active feedback or you are up a very smelly creek without a paddle in short order. That is beyond a simple system. It needs a servo system. Skip that, you can have the stick on a stop, the surface can, and will, drift anywhere. The only variable being the speed at which it happens.

A cable system is several orders of magnitude easier to accomplish. Someone who cannot design a simple cable system has a zero chance of designing a hydraulic system.
Hydraulic steering is pretty common in boats, even smallish ones.
It's the "creep" that would concern me - in a boat that just means the wheel is a bit off-centre, which is no big deal, especially as it's often multi turn.

But to have the neutral stick position off centre in a plane...brrr
 

gtae07

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1. It leaks. You need the surface to be in a definite position relative to the stick. That requires active feedback or you are up a very smelly creek without a paddle in short order. That is beyond a simple system. It needs a servo system. Skip that, you can have the stick on a stop, the surface can, and will, drift anywhere. The only variable being the speed at which it happens.
That doesn't require active feedback, at least not in the "electronic servo controller" sense. You just use cables/pushrods to do it. In a very simplified sense, you have a mechanical linkage between the actuator and surface, and a parallel mechanical linkage between the stick and surface, with a little bit of "slop" in it (just a little bit!). Finally, you have a finely-balanced directional valve on the actuator that's linked to the stick-to-surface connection.

Any difference in commanded position (stick input) and actual surface position moves the control linkage on the directional valve, which causes the actuator to move and push the surface. When the commanded and actual positions match again, the valve is shut off and the actuator doesn't move.

It took me a while looking at models of the mechanism and playing with a disconnected actuator to really grasp how it works, but it's quite clever and entirely mechanical. It also has a built-in mechanical override with the loss of hydraulic pressure (assuming you set up your bypass valves properly); the control forces are high but it works. Of course, there's a lot more to the details, like hardover prevention and hydraulic redundancy and all that, but my point is that there's no need for electronic feedback. Oh, and you get some measure of force feedback.

This is what's traditionally been called a "hydraulically-boosted" flight control system. It's quite popular in various flavors and been used on thousands of large aircraft, many of which are still in production.

A cable system is several orders of magnitude easier to accomplish. Someone who cannot design a simple cable system has a zero chance of designing a hydraulic system.
We're in 100% agreeement here.

Hydraulic steering is pretty common in boats, even smallish ones.
It's the "creep" that would concern me - in a boat that just means the wheel is a bit off-centre, which is no big deal, especially as it's often multi turn.

But to have the neutral stick position off centre in a plane...brrr
The system I described can result in a bit of off-center (from the "slop" mentioned earlier) but even in the worst case it's extremely small (I haven't done the math but perhaps a degree at most). Before it would get to the point a pilot would notice, you'd be tripping the hardover prevention system.


On a tangent, during my intern days I once had the opportunity to "fly" a simple (PC-based) simulator that had a stick with no feedback, not even a centering spring--it just flopped around. The testers wanted a floor-mounted center stick and the only one they could find off-the-shelf was a helicopter cyclic. Anyway, trying to fly that thing was a *****. Holding a steady attitude was a lot of work; trying to fly a normal pattern was sweat-inducing.

I found it much easier to "fly" the pseudo-F-16 model with the artificial stability turned off in my flight dynamics class the following semester. It was still a lot of work but the centering springs on the commercial joystick made all the difference.
 
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pictsidhe

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That doesn't require active feedback, at least not in the "electronic servo controller" sense. You just use cables/pushrods to do it. In a very simplified sense, you have a mechanical linkage between the actuator and surface, and a parallel mechanical linkage between the stick and surface, with a little bit of "slop" in it (just a little bit!). Finally, you have a finely-balanced directional valve on the actuator that's linked to the stick-to-surface connection.

Any difference in commanded position (stick input) and actual surface position moves the control linkage on the directional valve, which causes the actuator to move and push the surface. When the commanded and actual positions match again, the valve is shut off and the actuator doesn't move.
That is an active feedback system. I didn't say that it has to be electronic.

This is what's traditionally been called a "hydraulically-boosted" flight control system. It's quite popular in various flavors and been used on thousands of large aircraft, many of which are still in production.
Large aircraft. it isn't worth the trouble on small aircraft...
 
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cheapracer

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A cable system is several orders of magnitude easier to accomplish. Someone who cannot design a simple cable system has a zero chance of designing a hydraulic system.
Depends on your background, I personally have built way more scratch hydraulic systems than cables*, and would use hydraulic in a heartbeat IF not for the anti-anything that's not 1950s in aviation, so cables and rods it is.

Note there's billions of simple hydraulic systems in use by you lot everyday, i.e. clutch and brakes for your car. Billions, not just some.

* made plenty of stock replacement cables for motorcycles working in a motorcycle shop, but only a few number of scratchbuilt cable systems. One of those systems is still to hand, I'll get some pictures of it.

The last aircraft rudder cable system I did was dead straight runs from pedal to rudder, so nothing special there.
 

TFF

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Hydraulics are fantasy. He can’t make cables work. How is he going to run pumps, lines and actuators? Is he going to make actuators? He is not going to find anything off the shelf that will fit and mount. Talk about hole cutting all over that thing. Does he know where not to cut?

The Canadair regional jets are full hydraulic except flaps. Cables run from yoke to flight control into hydraulic actuators. No hydraulic no control. That’s why that plane has three systems with three backups and each system is split from the other’s. Big springs in cockpit to fake control pressure. Worked fine. Still leaks from bad factory swedges and leaking actuators was a monthly fix on at least one plane out of 150 we had. Better than the teleflex flap system.

He does not have the room or ability to redesign the whole control circuit. He is only thinking In fixes as is. He needs to go back to cables because he at least had that moving and shore up all mounting.
 

pictsidhe

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Depends on your background, I personally have built way more scratch hydraulic systems than cables*, and would use hydraulic in a heartbeat IF not for the anti-anything that's not 1950s in aviation, so cables and rods it is.

Note there's billions of simple hydraulic systems in use by you lot everyday, i.e. clutch and brakes for your car. Billions, not just some.

* made plenty of stock replacement cables for motorcycles working in a motorcycle shop, but only a few number of scratchbuilt cable systems. One of those systems is still to hand, I'll get some pictures of it.

The last aircraft rudder cable system I did was dead straight runs from pedal to rudder, so nothing special there.
My day job is with hydraulic machinery. I naturally repel water... Hydraulics became common in military aircraft in the 40s when speeds got too high for unboosted systems.
Hydraulic brakes systems are one way and do not have a fixed positional relationship. I would happily use such a system for brakes, and perhaps gear and flap actuation. But not ailerons. That needs a way more complex system.
Many of the early hydraulic designs are no longer permitted to fly in all but a very few countries. They lacked fail safe modes other than an ejection seat...
 

BJC

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After seeing today’s video, I’m wondering if there is any access for future inspections and maintenance of the systems.

He indicated that, after initially planning on all push-pull tubes for the ailerons, he went to a combination of cables and push-pull, but the system had too much flex, so he added metal plates to stiffen the structure where the poorly conceived pulleys mount, then he went to the sheathed cables, which have way too much flex, so now he is mulling over a simple electric actuation system with just a pot on the cable actuation wheel. The guys who designed the control systems in the Cozy, Velocity, Speed Queen, et al, must have patents that prevent the Raptor from using a proven system.

One wonders how much more money, time and complexity will be injected into the project.


BJC
 

Hot Wings

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Adding my 2 cents worth - in Venezuelan Bolívar:

I think wsimpso1 had the best "get it done" solution. Go back to the original system and add a tube between the pulleys in the tunnel/keel. A simple EMT tube hammered flat on the ends with some holes drilled for the pulley axle bolts would stiffen the system considerably. It's cheap, fast and isolates that part of the system so he can find the next weak area.

I'd hire him for a project I had been assigned if his skill set fit well, but not as a project manager. He seems to be a clever and adaptable person, but he just doesn't have the background or experience needed for his current role in the project.
Sad to watch this all unfold the way it has......:(

I'm actually surprised that an electronic servo actuated system, not FBW, wasn't part of his original project parameters, given his background. :rolleyes:
 

Rik-

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After seeing today’s video, I’m wondering if there is any access for future inspections and maintenance of the systems.

He indicated that, after initially planning on all push-pull tubes for the ailerons, he went to a combination of cables and push-pull, but the system had too much flex, so he added metal plates to stiffen the structure where the poorly conceived pulleys mount, then he went to the sheathed cables, which have way too much flex, so now he is mulling over a simple electric actuation system with just a pot on the cable actuation wheel. The guys who designed the control systems in the Cozy, Velocity, Speed Queen, et al, must have patents that prevent the Raptor from using a proven system.

One wonders how much more money, time and complexity will be injected into the project.


BJC
‘If we notice one thing that he said about the flex in the current system, which is 10% or 1”.

A teleflex, Morse or what ever brand we want to use will have slop of about 1/4” minimum to 7/16” as we have to push the we noodle inside the jacket housing.

how much slop is to much? How much slop is acceptable?
 

BBerson

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After seeing today’s video, I’m wondering if there is any access for future inspections and maintenance of the systems.
He has better than average access. (Grob has no wing access)
Grob sent me engineering instructions for installing access panels anywhere I wanted.
 

Marc Zeitlin

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After seeing today’s video, I’m wondering if there is any access for future inspections and maintenance of the systems.
In many places, the maintenance access is great - way better than many planes. However, in other areas, it's miserable and unless you're an octopus, you're not getting at stuff. So, it depends.

The guys who designed the control systems in the Cozy, Velocity, Speed Queen, et al, must have patents that prevent the Raptor from using a proven system.
I assume you're being facetious here, since even if there WERE patents on anything (which of course there aren't, since it's just a bunch of pushrods, torque tubes and belcranks) they would have long since run out. Since Peter stated that originally, he was going to use pushrods, etc., but then went to cables for unstated reasons, the opportunity existed...
 

Staggermania

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It seems like there are is a lot of stuff in that tunnel, and elsewhere, such as oil lines, I think, that could be removed to give him space to work to shore up the pulley mounts?
Also, at about 6 minutes or so in the video, he said that he is open to suggestions.
I hope he truly is, because this saga is becoming a little bit exhausting:(
 

cheapracer

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He seems to be a clever and adaptable person
You in the right thread?


It seems like there are is a lot of stuff in that tunnel, and elsewhere, such as oil lines, I think, that could be removed to give him space to work to shore up the pulley mounts?
Lesson for all those budding builders, test as soon as possible, as bare as possible, install the other fruit later.

He was told this numbers of times over the years.


If it was my plane I would take a large step back and fit tubes and bell cranks.
Yup, strip all the fruit out (auto-pilot, seriously?), fix the essentials, test it bare bones.
 

Hot Wings

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You in the right thread?
Yup, at least I think so!?
Just the fact that he managed to put together the funding and get a plane built to the taxi stage shows he has some useful skills - some of which I could use a bit more. But he has, or has developed, an antibiotic resistant case of tunnel vision.
 
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