Control mechanism for Tractor Gyros?

[rtfm]

Hi,
I notice from the LW web site (Specifications page) the following information:

Control Method:

* Conventional rudder, fully-tilting head (LW-3)
* laterally-tilting head with elevator (LW-2, long frames only).

Question:
Why the difference? Is the traditional fully-tilting rotor head insufficient for the longer body? Or is there another reason for the difference?

Duncan of Devonport
Auckland, NZ

[Al_Hammer]

Could it be that there is an advantage to controlling the pitch attitude with the tail rather then with the rotor? A relatively powerful tail on a long moment arm can tilt the body easily, while doing the same thing with the rotor would require a larger deflection of the RTV away from the cg. This would induce a lift change as well. The rotor will tilt when the body tilts, but it may be a smaller tilt.
At low airspeed, the tail, of course becomes less effective, so it is a tradeoff.

I'm sure Ron H. will have the answer.

[mceagle]

As I understand it, one of the problems of a fixed pitch head is the control lag caused by having to move the whole fuselarge to effect a change (which becomes worse as airspeed decreases), and another is the extra fuselarge and stabilizer drag caused by different rotor disc angles (and consequently fuselarge angles) for both higher and lower airspeed extremities of the normal flight envelope.

As Al said - I'm sure Ron H would be able to tell us.

[WindRyder06]

Ron will doesn't suggest using the fixed head with the elevator. In fact LW-2 (the airframe) is for sale. A couple of years ago Ron told me he was going to "fix" the elevator in place and remove the tilting head when someone buys the airframe.

[mcbirdman]

Quote:
"Why the difference? Is the traditional fully-tilting rotor head insufficient for the longer body? Or is there another reason for the difference?"

Traditional isn't the "fully tilted rotor". The old "tradditional" design needed tail surface controls because the head wouldn't move. Now the more commonly seen what I would call contemporary .....IS the fully articulated design and it seems to be the preffered choice.

[Screw]

Screw-In

On the LW-2 and other Long frames, you can iether go with a full tilt head or a lateral tilt head with an elevator.

The reason Ron Herron only offers the lateral tilt head and elevator on the LW-2 and other long frames is because you need leverage of the long frame for the elevator to be effective.

You can get a full tilt head on any of his models. I have an LW-4 long frame with a full tilt head.

Screw-Out

[WHY]

Also, think about it, if you land with a good head wind and the rotor is tilted back about 10 degrees and the fuselage is angled about 10 degrees (total 20 degrees combined angle of attack into the wind and you only have lateral control on the rotor it is going to be a problem getting the rotor stopped unless you have a auxilliary system to decrease the rotor angle into the wind, which means you going to have the head hinged in longitude anyway so why not the full system?

Tony

[Screw]

Screw-In

Usually after landing a gyro of this configuration, to slow the blades you simply steer the gyro down wind and wait till the blades slow down.

As James mentioned earlier, a lateral tilt head and an elevator was the origional configuration of early gyroplanes known as Autogyros.

Now, most prefer the full tilt head. There are some advantages like have full control of the pitch at any airspeed, however, there is really nothing wrong the old configuration other than a slight lack of elevator authority at super low airspeeds.

Amilia Erhart and Charles Linberg liked it.

Screw-Out

[mcbirdman]

Actually the reason that ron went to the fully tilted head is because every time he designs something someone wants to change it. When he made the tail dragger tractor everyone said yea, that is great but what about a tricycle landing gear and so.......

Also note that his LW3 with the Radial is a LONG frame same as mine. The short version is only 2 foot shorter. Note that it doesn't have a moving elevator..... I think Ron had the same thing happen with the elevator..... people said yea but....... and you will notice that all his newer designs, the LW3 thru 5 - long or short..... all have a Simple 0 degree incedence stab and that is all that is Needed.

[pwendell]

Screw-In

As James mentioned earlier, a lateral tilt head and an elevator was the origional configuration of early gyroplanes known as Autogyros.

Screw-Out

Actually the earliest Autogiros had a totally fixed rotorhead and used ailerons on stub wings for roll control along with an elevator for pitch control. I think there was slightly later model that had a head that only tilted to the side. Once Cierva perfected cyclic pitch control, all of the Autogiros quickly moved to the full tilt head. The major problem with using ailerons and elevator to control the gyros was a severe lack of control authority at low speeds. This made landing the early Autigiros challenging in x-winds. The full tilt head solved that problem.

[rtfm]

Hi guys,
As usual, your comments have proved most interesting and informative. They have certainly cleared up the confusion in my mind. It's like having a bunch of gyro guys over for a beer, and getting into a discussion. Ask a question, and then sit back, relax, and learn. Good stuff. Thanks.

Duncan
Auckland, NZ

[Screw]

Screw-In

PWendall, you are right and I stand corrected. But the point remains.

Screw-Out

[Al_Hammer]

It's like having a bunch of gyro guys over for a beer, and getting into a discussion. Ask a question, and then sit back, relax, and learn. Good stuff. Thanks.

What beer? I didn't get any beer. :confused: :confused:

[RHerron]

Hi all,

Have not been on the forum for a long while. Then, I forgot my password!

Anyway, I scanned through this discussion and will get beck with more details later.

In the meanwhile:

1. The long fuselage does not in any way require more head tilting to control. Response is crisp and positive.

2. The elevator control eliminates any lag and is a more positive system. The downside is ground handling (takeoff and after landing) since you have no control over the disc fore and aft. The elevator control, in the air, is PIO proof...period.

3. The fully-tilting system was decided upon as the best overall when all things are considered. It does create a very close rotor-to-tail clearance when the blades are slow (ground operations) and the stick is full-back.
This is not a factor with the elevator control because the head does not tilt back.

4. The short frames diminish this issue. The long frames require that the stick be held forward when the blades are stopped or turning slowly and that the blades be started with the stick forward. After that, just like any other gyro.

5. On my webpage (Thanks Mike G) go to History of Little Wing Autogyros for a complete explanation of all these things.

www.littlewingautogyro.com

Sincerely,
Ron H

[rtfm]

G'day Ron,
Nice to have you back. Your comments re: elevators vs tilting rotorhead are most enlightening. However, (and I pose this question in the spirit of genuine enquiry) why not use both?

If I understand the control system of the CC correctly, they use both systems. At low speed they get full control from the rotor tilt, but as speed increases the elevator becomes more important. Sure, they use wings, which generate lift at higher speeds which in turn unloads the rotor, but it strikes me that this hybrid control system might also be applicable to slower tractor gyros which don't use wings.

As you probably know, I'm designing a tractor gyro (which may use wings a-la-the CarterCopter - depending on how long wishful thinking survives in the harsh light of reality). But even without the wings, I'd be interested in hearing your comments regarding the merits of using both control systems on a tractor gyro.

Kind regards,
Duncan

[RHerron]

G'day Ron,
Nice to have you back. Your comments re: elevators vs tilting rotorhead are most enlightening. However, (and I pose this question in the spirit of genuine enquiry) why not use both?

If I understand the control system of the CC correctly, they use both systems. At low speed they get full control from the rotor tilt, but as speed increases the elevator becomes more important. Sure, they use wings, which generate lift at higher speeds which in turn unloads the rotor, but it strikes me that this hybrid control system might also be applicable to slower tractor gyros which don't use wings.

As you probably know, I'm designing a tractor gyro (which may use wings a-la-the CarterCopter - depending on how long wishful thinking survives in the harsh light of reality). But even without the wings, I'd be interested in hearing your comments regarding the merits of using both control systems on a tractor gyro.

Kind regards,


Duncan

Duncan,

I designed the first three LW's to use the elevator-for-pitch simply in an attempt to forever render PIO and Buntover to a non-issue.

This it did. The downside was ground handling.

Now, when I built LW-3 with the fully-tilting head, I had a direct comparison. Flying one (LW-2) right after the other (LW-3) made something very obvious. This was the fact that the horizontal stabilizer alone was totally adequate to make the machine rock-solid in pitch. This due to its large size and the fact that it is located 10 ft. from the rotor axis.

Very little difference in stability was noted between it and LW-2 with the elevator. The main difference was control power and lag. The elevator had a very solid, firm "feel" to it and there was no time lag between input and response. In cruise flight, I preferred the elevator control.

Like I said earlier, when all things are considered (like take off distance, rotor management on the ground and multiple flare capability) the tilt-head won.

A control system that used both, yes, I considered it. (By the way, the CC needs both because the rotor gets progressively slower as the wing takes over and the rotor begins to be "along-for-the-ride".) However, it involved making a simple design much more complicated and introduced the posibility of control system malfunction. Again, the stability of the Little Wings is rock-solid using either system. The faster you fly, the more stable the aircraft becomes. Non-believers won't believe this but it is true.

If your aircraft has the engine pulling through CG and has a tail volume of around 20+% (LW-3, LW-4) or even 15% (LW-5), then it will be pitch-stable and this will not diminish with high airspeed (in fact it will get better).

So, I didn't feel the need to integrate the two systems.

The elevator models were a pleasure to fly but I felt that newbies would have a hard time with the rotor management (on the ground) issue. I learned to deal with them and certainly others could too. This is why they are still available in the drawings.

I wish you well with your project. If I can be of any help, let me know.

Sincerely,
Ron H

[richard lidke]

Hi all,

Have not been on the forum for a long while. Then, I forgot my password!

Anyway, I scanned through this discussion and will get beck with more details later.

In the meanwhile:

1. The long fuselage does not in any way require more head tilting to control. Response is crisp and positive.

2. The elevator control eliminates any lag and is a more positive system. The downside is ground handling (takeoff and after landing) since you have no control over the disc fore and aft. The elevator control, in the air, is PIO proof...period.

3. The fully-tilting system was decided upon as the best overall when all things are considered. It does create a very close rotor-to-tail clearance when the blades are slow (ground operations) and the stick is full-back.
This is not a factor with the elevator control because the head does not tilt back.

4. The short frames diminish this issue. The long frames require that the stick be held forward when the blades are stopped or turning slowly and that the blades be started with the stick forward. After that, just like any other gyro.

5. On my webpage (Thanks Mike G) go to History of Little Wing Autogyros for a complete explanation of all these things.

www.littlewingautogyro.com

Sincerely,
Ron H
Its nice to see the guy who knows what he is talking about clear the air of those comments which don't mean a whole lot . Its simple guys, you have a choice, Ron gives it to you to benefit the performance you are looking for. ON the ground the full tilting head has benefits, IN the air the tailfeathers help out, but one must weight both to get what one wants from this little bird. I cant wait to fly mine, now its more than just a box of tubing! Booster Rich :D :D

[magilla]

First of all: Great Stuff!!! Thanks for all the input!! I am learning a ton!!

What about incorporating elevator trim (a small control surface on rear elevators) into tractor designs to complement the fully tilting rotor head?? i see benefits at higher airspeeds.

I am going to build a LW, (haven't decided on LW-3/4/5 yet, or engine, or rotors - pretty much just decided that the LW is the tractor for me - this forum just adds to the credibility of the design :) )

Anyway: I am UH-60 Blackhawk maintenance test pilot, and we have this huge thing on the back of the helo called a "stabilator." A ton of functions, but it boils down to "It keeps the acft level at all airspeeds" - that is, it maintains a stable platform.

Changing power settings through collective causes the stab to move up or down in opposite direction, keeping acft level. For gyros, I think this would be great to be able to plane out the acft with elevator as opposed to cyclic at different power settings!!!

Airspeed reference - based on inputs from an airspeed transducer, stabilator automatically "planes out" as acft accelerates to keep acft level. At higher airspeeds, the stab is actually pointed up
For gyros, this could be done manually - set elevator trim at different settings for different airspeeds


Could we not design some of the benefits of a moving stabilator into the LW or other tractor design (keeping the fully tilting head????

Why not have a manually controlled elevator trim (on a china hat on the cyclic or a trim wheel)??
This would alleviate the different pilot perspectives from different airspeeds, and actually increase the reliability of the airspeed indicator by keeping the air hitting it at the same AOI. Trim the acft "level" at all airspeeds.

Might also have a "fail-safe" mode in case of power off descent to tilt up, keeping the nose higher. I understand that it may reduce available aft cyclic for the flare, but it would keep the acft more level, and if outfitted with G-Force landing gear or equivalent, could actually increase safety by allowing acft to land wings level.

Anyway, just some thoughts.

How much weight penalty or complexity to add elevator trim??

Spencer

[Rotor-Head]

I've only skimmed through this topic, but it seems like it may have something to do with Cierva's discovery of control surfaces (like alerons and elevators) becoming usless at very slow speeds, mainly during landings... which at the time of limited controllable rotor heads, tended to roll over on slow landings. hmmm

[magilla]

Sorry for the confusion folks, - I will edit my post to make sense, and ask the question first!!

Bottom line: I think that elevator trim, IN ADDITION TO a fully tilting rotor head would be a great idea. Rotor head stability for slow speeds, and elevator at 0 degrees with small surfaces for trim at higher airspeeds.

ADVANTAGES:
* trim acft level at all airspeeds/power settings
* emergency mode for power offs to keep nose from dropping too low

Disadvantages: trim cables, moving control surface design/weight/cost

What do you think?

[C. Beaty]

The drawings contained in Cierva’s patent of direct control (rotorhead tilt) show evelator trim. US Patent #2,380,580.

[magilla]

I guess I'm not the first to think of it.

However, I would like Ron H. to weigh in on this (or some other gyro juggernauts) to see if it is even worth it for the control authority.

Complexity and safety vs. simplicity (and safety)

I'm just wondering with the modern fully tilting heads if it would be possible to trim attitude at different cruise speeds with elevator trim, and then if it is even worth it.

Thanks for the posts so far - the cierva diagram was great. Where did you get it?

[C. Beaty]

The US Patent Office website is here:

http://patft.uspto.gov/netahtml/srchnum.htm

Just paste the patent number into the box.

Patent drawings are in tiff format. You’ll a plugin for your browser to view the drawings.

As long as the horizontal stabilizer is of adequate power, the fuselage will stay level in the upper speed range without need for trim.