wing levelers

On Fri, 25 Feb 2005 12:10:45 -0500, "Peter Dohm"
wrote:

In an effort not to go too far beyond my own knowledge, I'll avoid detail.

My best recollection, being about twenty years from being current as either
a pilot or a technician, is that "wing leveler" is a very missleading term
applied
to a single axis auto-pilot. Typically, the single axis would be yaw
(heading)

Try a Cherokee. They turn just fine using the ailerons with very
little adverse yawh.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
and would have been accomplished be slaving to either a rate gyro (such as
a turn coordinator or turn and slip) and a potentiometer, or a system of an
air jet and heated resistors, to provide a correction signal with
considerable
integration (a/k/a damping or low pass filtering). Although it would seem
intuitive to have the wing leveler steer the plane with the rudder and have
the dihedral roll the wings, the only systems that I have seen used the
ailerons and depended on the vertical stabilizer to keep the resulting yaw
within reason.

If you are still interested in learning more about how autopilots work, I
would
suggest trying to obtain some of the factory trianing manuals for the
technicians who will work on them. Try Bendix/King, S-Tech, and others.
Some books may also be available at college bookstores on booksellers
like Borders or Barnes & Noble.




"Dick" wrote in message
. com...
Sitting around the hanger and discussing the possibility of somehow using
off-the-shelf electronic/computer components or gadgits for semi-automatic
wing leveling on lightly loaded, short wingspans.

Not being computer guys, the current thought is that something should be
out
there that is available cheaply and modifiable to use a simple wing
leveler.

Having heard someplace that automotive computers, as an example, sense
data
millions of times leads us to believe that sensing the wing tip initial
movement and counteracting very very quickly would be a good thing.

As an example: One fellow pictured a rolling ball bearing inside a tube
somehow activating a magnetic switch which in turn pulses a dc linear
motor
to operate the aileron minutely.

We are not sure how to detect the very earliest initial wing tip movement
or
drive the small trim type motor and would appreciate some thoughts or
site
recommendations to investigate.

Thanks, Dick

Trim tabs you say- Well that makes a lot of sense then. Some nice big
servos embedded in the wing and horizontal stab could do double duty as
conventional trim and with addition of controller, an automatic
stabilazation system.

wrote:
Trim tabs you say- Well that makes a lot of sense then. Some nice big
servos embedded in the wing and horizontal stab could do double duty as
conventional trim and with addition of controller, an automatic
stabilazation system.


As has been already pointed out the devil is in the details. The theory
is simple when thinking of damping. Think of a child swinging on a
swing. You want to stop him. At what point do you apply influence? Not
at the bottom where the swing there is the most kinetic energy you have
to fight. You want to apply force at the end of each swing.

Simple, ain't it? If it really were that simple you could use a rate
sensing gyro hooked more or less directly to your servo. The gyro would
have to be mounted near the center of motion in your aircraft. I worked
on autopilit systems on several types of aircraft and none was simple.

One thing that you need to figure out is how to install your servo in
such a way as you can still manually trim without damaging it. Another
thing that would be handy is a quick disconnect button on your yoke or
stick. You'd be surprised how fast a malfunctioning power steering
system can get out of hand if it wants to.

Dan, U.S. Air Force, retired

Dan, U.S. Air Force, retired

Thats what is done on RC Heli's, the rate gyro directly sums into the
normal command. The only control you have is the gain on the gyro and
I'd guess you'd have to adjust this to particular aircraft and
preference of the pilot.

I assume the gyro(s) would be pretty near the center of motion along
with the pilot, but why is this a requirement? Doesn't any ridged part
of the aircraft experience the same yaw,pitch,roll accelerations? One
possible implimentation could be a gryo co-located with the actuator
(servo) that controls that axis.

I think this would replace manual trim because if you could do the
stability control, you sure as heck could make it move back and forth
in response to a 3 position toggle switch.

If it breaks you fly without trim till you land. I think there is some
rule that the aircraft must be controllable with any trim to it's full
limit.

wrote:

Thats what is done on RC Heli's, the rate gyro directly sums into the
normal command. The only control you have is the gain on the gyro and
I'd guess you'd have to adjust this to particular aircraft and
preference of the pilot.

I assume the gyro(s) would be pretty near the center of motion along
with the pilot, but why is this a requirement? Doesn't any ridged part
of the aircraft experience the same yaw,pitch,roll accelerations? One
possible implimentation could be a gryo co-located with the actuator
(servo) that controls that axis.

Take a 12" ruler rotate it around 4" mark. Imagine you have rate gyros
at the 4" and 11" marks. The one at the 4" mark senses only rotational
rate, the one at the 11" mark senses rotational rate plus a G force. If
you read the specs on pizeo rate gyros they are G limited. You can buy
them with G limits in excess of 50G but they can be pricy. Exceding the
G limit on a pizeo gyro won't neccesarily kill it, but you will get an
error which defeats the purpose.

None of the aircaft I worked on had pizeo gyros, but the theory still
holds. The power steering rate gyros on the F-4E are mounted in the
wings near the roots. It's not my idea of fun to change them either.

Sometimes design considerations preclude mounting near the axis, but if
you can do it it will reduce induced errors.

I think this would replace manual trim because if you could do the
stability control, you sure as heck could make it move back and forth
in response to a 3 position toggle switch.

To be really cool install a coolie hat switch.

If it breaks you fly without trim till you land. I think there is some
rule that the aircraft must be controllable with any trim to it's full
limit.

I used to fly R/C way back in the dark ages. Unless servos have
radically changed you shouldn't have problems unless they don't provide
enough force to the tabs near the limits of the servo's travel.

Dan, U.S. Air Force, retired

On Fri, 25 Feb 2005 00:12:06 GMT, "Dick" wrote:

Sitting around the hanger and discussing the possibility of somehow using
off-the-shelf electronic/computer components or gadgits for semi-automatic
wing leveling on lightly loaded, short wingspans.

To paraphrase the manual for my auto-pilot. When encountering more
than moderate turbulence, turn off the autopilot. I believe Pete
touched on this as well.

The same is true for altitude excursions.

Mine can do a much better job of holding altitude and attitude than I
when the going gets really rough.

That's when I turn it off and manually hold the attitude (more or
less).

Yes it can be done and I'd think the simplest would be to get a solid
state gyro, or turn coordinator... and build around that.


Not being computer guys, the current thought is that something should be out
there that is available cheaply and modifiable to use a simple wing
leveler.

All it takes is money. The less ingenuity, the more money.


Having heard someplace that automotive computers, as an example, sense data
millions of times leads us to believe that sensing the wing tip initial
movement and counteracting very very quickly would be a good thing.

Counteracting very quickly with a lightly loaded wing could possibly
break something very quickly as well.


As an example: One fellow pictured a rolling ball bearing inside a tube
somehow activating a magnetic switch which in turn pulses a dc linear motor
to operate the aileron minutely.

Rule number one...no... sorry that one is already taken. An airplane
and any thing in it does not know up from down in anything except
straight and level flying. However a gyro tends to stay in the same
position you put it when starting out, so it makes a good reference
platform. (as long as you don't do anything drastic to confuse it such
as causing it to tumble)
I haven't seen any prices on the components for a solid state gyro.


We are not sure how to detect the very earliest initial wing tip movement or
drive the small trim type motor and would appreciate some thoughts or site
recommendations to investigate.

Find an old DG, or TC and experiment from there.
Build in sufficient disconnects so if it goes TU you can put the
greasy side on the bottom again.

You can over-ride a wing leveler or AP, but it always gives me a
strange feeling to be telling the airplane to do one thing when it's
fighting me to do something else and its attempt is readily apparent.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Thanks, Dick

"Roger" wrote in message
...
To paraphrase the manual for my auto-pilot. When encountering more
than moderate turbulence, turn off the autopilot. I believe Pete
touched on this as well.

Driving an auto-pilot too hard can put your servos on the rate limit. On a
rate limit, a servo develops serious amplitude-dependent lag, which can
destabilize your loop closures. THe way arount this problem? Big, huge,
powerful, fast servos. This solution opens up a whole other can of worms.

All it takes is money. The less ingenuity, the more money.

Being intimate with the hazards associated with such a project, I would
never recommend this as a casual development project. In this case, less
ingenuity means great exposure to serious hazards. It all seems so simple in
concept, but the devil.......

Counteracting very quickly with a lightly loaded wing could possibly
break something very quickly as well.

And that's just one of the hazards.

I haven't seen any prices on the components for a solid state gyro.

The ones the R/C guys use, which are, in my opinion, quite rugged and
accurate enough for this kind of an application, pretty innexpensive. I
think I saw one model that sold for under $200. Systron-Donner makes
single-axis chips for (working from memory) under $500. Full 6-dof Motion
Packs go for around $20k. I think Crossbow has a 6-dof package for under
$12k.

Build in sufficient disconnects so if it goes TU you can put the
greasy side on the bottom again.

Yup. On the stick. Fly it with a gun to it's head.

Pete Schaefer wrote:

snip
I think Crossbow has a 6-dof package for under
$12k.

Crossbows prices have dropped over the past 2 years. The AHRS they had
at $10K is now under $8K per UI of 1.

Now if the made and interface to drive synchro instruments....

Dan, U.S. Air Force, retired

Pete Schaefer wrote:

"Dan, U.S. Air Force, retired" wrote in message
news:IfyVd.20906$Sn6.20727@lakeread03...

Crossbows prices have dropped over the past 2 years. The AHRS they had
at $10K is now under $8K per UI of 1.


Probably still a bit too pricey for a home-brew rate damper, autopilot,
etc., to be built by a novice.


Now if the made and interface to drive synchro instruments....


All that effort to package up accurate solid-state measurement devices and
you want to drive synchro instruments?

I am a tad old fashioned. Besides, I have yet to see a glass display I
like.


Isn't there some PDA software that uses a Crossbow AHRS to drive a set of
displays?

I think there is such software at Crossbow's site. I can imagine a PDA
as a back up device or temprary upgrade. That is if you want to spend
$8K for something temprary. The PDA can be mounted ona a panel or yoke
clip. Where do you put the AHRS? Strap in to a seat and you have lost a
passenger. I don't know if it would be worth it.

Dan, U.S. Air Force, retired

"Dan, U.S. Air Force, retired" wrote in message
news:MUAVd.21080$Sn6.16679@lakeread03...
I am a tad old fashioned. Besides, I have yet to see a glass display I
like.

I'm kinda liking the looks of the Blue Mountain EFIS Sport these days. I
think it can even support a slave display. Would be nice to spread out the
data and declutter the individual displays. A lot of the EFIS type products
out there just look too damned busy for my tastes. Gonna order the Blue
Mountain for a work project pretty soon. I'm using my current project at
work to evaluate stuff I'd eventually like to stick in an RV-8.

I think there is such software at Crossbow's site. I can imagine a PDA
as a back up device or temprary upgrade.

I haven't seen a PDA that I'd want in the cockpit, myself.

clip. Where do you put the AHRS?

They're not very big. You would probably build a small shelf and mount it
behind the firewall. You typically have to mount devices like that at a
structural node - right under the pilot's ass is often a good spot.
Otherwise, structural vibration will clutter up your data.

passenger. I don't know if it would be worth it.

I don't think I'd ever bother to mess around with such an expensive device,
especially when there are complete instrument packages for less.