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Rainier Lamers
11-11-2008, 04:32 AM
I'm getting a lot of builders wanting to know some details on our autopilot so I'd like to post this here on VAN's...

The MGL Enigma, Voyager and Odyssey is currently being updated with autopilot functionality in addition to the existing external autopilot interfaces (NMEA, ARINC). The status of this project is very far advanced and I expect release in roughly 2 weeks if we get a break in the weather for final test flights.

We have teamed up with the good folks at Trio and as a result we are using the Trio "Gold standard" servos. However, we also support any servo that can handle a standard PWM signal. In addition to this we will be releasing the details on the MGL standard servo protocol which is open to any third party to construct their own servos.

The autopilot implementation, true to our normal style of making things flexible can be extended to 5/6 servos of different styles if required with autopilot characteristics ranging from single function to a full five/six axis control. Further characterisation caters for helicopters as well.
Each axis is highly configurable in control response to installation and aircraft characteristics. "Axis" is here used to indentify a distinct control, for example "throttle, lift, aileron, rudder, elevator, etc".

Our first release caters (from a software point of view) for typical 2 axis systems with two servos (allthough single axis control can also be done).

From an autopilot functionality point of view, litteraly everything that opens and shuts can be thrown at the autopilot which in the case of our EFIS systems means you can select any horizontal and/or vertical navigation source, including bugs, connected external sources (ILS, VOR, etc) or any internal source (Flightplans, GPS, compass, altimeter, GVOR, GLS etc).

In order to implement the functionality of the autopilot on any of our instruments, a further small unit needs to be purchased but this is very low cost. This we call a "COM Extender" and it provides an additional 4 serial ports as well as 4 PWM signals and optional servo power control.
While the primary function of this unit is to give you additional serial ports for things like COM and NAV radios, traffic systems etc, it does contain the final part of the autopilot which thus divorces final servo control from the connected EFIS for safety reasons.

Trio servos can be purchased via any of our distributors for use with MGL systems or you can contact Trio direct. Be sure to mention that you will be using the servos for a MGL system so you get the good price !

Rainier
CEO MGL Avionics

RecVehicle123
11-22-2008, 04:33 PM
What is the average failure rate on all of your hardware?

MauiLvrs
12-01-2008, 02:22 PM
So,....
What is the current status?

Rainier Lamers
12-02-2008, 06:04 AM
What is the average failure rate on all of your hardware?

???

Impossible to answer this question with accuracy as we don't know what happens with our instruments once they leave our factory.

In use failures are very low, perhaps nearly non existant - most issues are during installation - but even that is very low if our return for repair rate is anything to go by. Overall, as a rough estimate I'd say we see around 0.1-0.2% of our instruments again after they left our factory sometime during their life.
Sometimes they come back smashed. Really smashed. The kind of smashed you get after an aircraft crash.
We even had one of our Ultras returned after it was recovered from the bottom of a lake. We cleaned it out, fixed some minor corrosion and that's all - it's flying again.

Things that tend to fail are probes (EGT, CHT oil pressure are the most common here).

In case you are wondering, I know our stuff tends to be low cost - but that has nothing to do with cheap. All our EFIS systems and most of our other items are manufactured in a certified high tech facility that is also being used by Airbus to manufacture some of their systems. They also do a lot of military avionics.

Rainier
CEO MGL Avionics

Rainier Lamers
12-02-2008, 06:24 AM
So, its been about 18 months....
What is the current status?

18 months ?

The active development started about 5 weeks ago (this is the software part), the servo interface part (which is hardware) took longer and was delayed because we wanted to get the Voyager out first.

Apart from that, our autopilot development started with the development of our own servos. This was before Oshkosh. At Oshkosh we agreed with Trio to use their servos. After Oshkosh we modified the hardware design for our COM Extender and threw the first 50 units away - we needed to change this to better accomodate the Trio servos. This is complete and we have started production of this module.
So, I don't think we have been doing bad here...

Current status ?
Lots of test flying. The current status would be best described as "tweaking".
The process is about like this: Fly some test, note results, back to lab, tweak something, simulate it, when happy get back in the air, repeat cycle.
This repeats itself once or twice a day.
Roll/Bank is done. Pitch is mostly fine but I'm not yet happy with the response on our Jora test bed if vertical steering comes into play. Hold is fine but changing altitude (without touching the throttle) is fun currently. The Jora's two-stroke engine has a very limited torque band so it overreacts in dramatic fashion to pitch changes with some interesting side effects.
But - it's getting close.

I have been holding back download updates on all our instruments as the next version will have two of our autopilot characters released, the first one is "2 axis capture and track" and the second one is "2 axis capture and track with yaw damper".
Should have a third and fourth character released after that that includes throttle control (about the only way to handle ascent and descent properly).

Rainier
CEO MGL Avionics

MauiLvrs
12-02-2008, 09:48 AM
18 months ?
That would be a math error for the announcement date.
We are ready to seal up the RV-9 wings, so the real question would be how are the servos going to mount. Dynon will just bolt in through the access hole. Trio didn't seem to have any info on how to mount the servos on their site. It seem as the rest of the issues should be resolved before spring when we expect to be in the air.

Rainier Lamers
12-02-2008, 10:16 AM
That would be a math error for the announcement date.
We are ready to seal up the RV-9 wings, so the real question would be how are the servos going to mount. Dynon will just bolt in through the access hole. Trio didn't seem to have any info on how to mount the servos on their site. It seem as the rest of the issues should be resolved before spring when we expect to be in the air.

Yes you are right on the servo mounting side of things. The Trio's don't seem to need brakets in most cases due to the convenient mounting flange (they were a doodle to install in our Jora).
So it's a matter of finding a suitable location I guess. There must be a lot of Trio autopilots flying on RVs - perhaps a post on this group for a photo or advice will result in some response ?

You might need access to the servos to adjust the clutch - so don't seal them in "forever".

Actual coupling to the controls is not hugely critical due to the adjustments you can do in the software - the Trio's active control angle on the bellcrank is around +/-40 degrees (you can move the bellcrank well outside this range but you can't engage the autopilot if you are outside this as the host (in this case our EFIS) cannot determine the bellcrank position.

So what I have done on our test aircraft is to install the roll servo such that the servo can control about 50% of travel of the stick each way in roll.
Pretty much the same for pitch.
The remaining 50% or so of travel is prerogative of the pilot (and seldom used on the Jora anyway).
In actual flight pitch movements tend to be very small except if the pitch stabilizer kicks in (this happens if large uncommanded pitch is applied turing turbulence).
Our Jora is pretty sensitive to uncommanded roll during turbulence (large wings, low wing loading) so the roll stabilizer tends to keep the servo busy at times and firm corrections are needed - but the 50% the servo can control the stick seems quite enough for that.

From the little flying I have been priviliged to do in a RV6 I know that stick movement is very small during normal flight. The RV6 (and I suppose all other RVs ?) fly very nicely with just small input and don't seem to need much (if any) rudder to fly a nice turn. They are also very insensitive to turbulence (unlike our own aircraft). All this combines to making life relatively simple for an autopilot.

As they say - we shall see....

Rainier
CEO MGL Avionics

Mike S
12-02-2008, 11:52 AM
(they were a doodle to install in our Jora).


Rainier
CEO MGL Avionics

Little culture clash going on here.

Is the doodle good or bad???

Rainier Lamers
12-03-2008, 12:04 AM
Little culture clash going on here.

Is the doodle good or bad???

Sorry. "Doodle" means "easy".

All you need is a suitable surface where you can mount the servos such that you have a good connection between the servo bellcrank and control rods, hinges or whatever you need to connect to.
The servos are in the same form factor than the old Navaid servos so perhaps there is some further info around installations that are still using those servos.

Rainier
CEO MGL Avionics

John H
12-07-2008, 11:31 AM
Hi all,

FYI. A while back I installed the TRIO AP servo ina RV-9 attached to a .063 plate mounted to the next outboard rib from the aileron belcrank. That location was fine for the linkage but was not very ridgid. With the servo engaged and you slipped the clutch the rib would flex. I didn't care too much for the flexing, thought with time and the dynamic loading of the control surfaces we could be dealing with some metal failing.

A different approach was applied to the mounting. I didn't want to mount directly to the spar, figured it didn't need any more holes than necassary in it. I again mounted the servo to a .063 plate with 3/4" angles nestled as a 'Z' stringer. These were attached to the .063 plate and then attached to the 4 AN3 bolts that secure the aileron belcrank attach brackets to the spar. I then fabricated 2 angle clips from 3/4" angle. These are attached to the outboard end of the .063 plate and the next outboard rib.

Sorry but I don't have any pix to share they went with a crashed HD. However I did send them to TRIO, I'm sure they would pass them on if requested.

John H.