Looking for a XYZ ARINC407 syncho explanation in simple terms

Jan Panteltje wrote in news:s00s3q$1s4n$ snipped-for-privacy@gioia.aioe.org:

It would seem to me that there would be a MEMS chip out there that does it.

Hell, GE uses an IRU (Inertial Reference Unit) for precise motion transitions in all directions.

I put a couple hundred in mobile satellite transceivers. They are $50k each and we were charging $100k each. Every C-130 in service now has a secure, hot, mobile Internet connection back to the Pentagon with the cost being a small 2 foot tall bump on top of the fuselage at the center escpape hatch port. A 12" dish sits under that continually tracking its bird.

snipped-for-privacy@highlandsniptechnology.com wrote in news: snipped-for-privacy@4ax.com:

It is called an inertial reference unit. They replaced gyros over a decade ago. The GE unit is like 7 x 7 x 9 inches cube and has several miles of fiber optic coils in it, but has a super fine resolution too. Smaller units like that in your phone uses MEMS and are far less resolved.

Here's one (another military grade unit):

Or slow turns.

I recall pilots manually zeroing the artificial horizon now and then to correct for gyro drift, when they could clearly see the horizon.

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John Larkin      Highland Technology, Inc 

The best designs are necessarily accidental.

I owned a Piper Malibu, N4360V, for many years. It was a 6-place, pressurized, air conditioned, full IFR, certified for flight into known icing, 25,000 foot ceiling, full autopilot, yaw damper, RNAV, LORAN, VOR, radio altimeter, 16GPH cross-country plane.

It was a dream to fly.

I flew it all over the US, from Boisie to San Diego, Rochester to LA, San Jose to Boca Raton, San Jose to Boulder, CO, and many other places.

In all the years I owned it, I never had to reset the artificial horizon even once. Any drift would have messed up the autopilot really bad, which could have been a disaster at midnight in IMC.

A problem with gyros is they can fail without warning. This invariably leads to a crash if you are flying in the clouds. I duplicated the pilot's instrument panel for the copilot's seat so I would always have at least one working horizon.

Planes that required resetting the artificial horizon may have had bad gyros that could fail soon. This needs to be fixed before the next flight.

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The best designs are no accident - sw

Steve Wilson wrote

I have not flown anything which needed resetting the AI (art. horizon) but all planes without a slaved compass system need the DI (heading) resetting from the liquid compass every x minutes, which is a total PITA and this is why all "proper" IFR tourers have a slaved compass system, mostly the KCS55 (KG102A, KMT112, KA52, KI525, KI229 etc). I now have the Sandel SG102 which drives two SN3500 EHSIs and that is solid state and saved a few kg on the KG102A gyro.

But it still uses XYZ from the Gemini era to distribute the heading data :) OTOH it all works, whereas digital comms (ARINC429 typ.) is often incompatible.

On a sunny day (Wed, 10 Feb 2021 15:16:43 +0000) it happened Peter wrote in :

I wrote, years ago a small simulation in what was it language? for an an object (say plane) in space using those 6 axis chips. I then wanted to know if inertial navigation was possible (so no GPS but just by recording the MEMS output) After asking in some some group I ran a drift experiment on that chip, using its internal sensor to stabilize temperature then ran some drift tests

I also wanted to know if I could detect the moon orbiting from G measurement with that chip: from that data I concluded what I was seeing was day-night temperature variation in spite of using the chips internal temperature sensor to keep it at a fixed temperature. Thinking about that, it seemed to me PCB temperature change does put mechanical stress on the chip, could be an explanation. Then some uni repeated that experiment with the whole thing in a temp controlled oven. IMO that was a good move,, usually those projects then go silent as DOD gets interested, I went on to playing with the next interesting thing..... But big mechanical giros (V2?) or laser giros (bit later)? or MEMS ? MEMS may be good enough,

So have been camp fires :-) Personally I use a microwave.

On a sunny day (Wed, 10 Feb 2021 17:58:24 +0000 (UTC)) it happened snipped-for-privacy@decadence.org wrote in :

Nice!

The guy was an aerobatics instructor. He'd fly radically for an hour at a time, which probably affected gyros. I don't get motion sick, but an hour with him before lunch did reduce my appetite.

We's steal cheap toilet paper from work, unfurl a roll at 7000 feet, and see how many times we could cut it in half before it (or we) hit Lake Pontchartrain.

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John Larkin      Highland Technology, Inc 

The best designs are necessarily accidental.

On a sunny day (Thu, 11 Feb 2021 03:19:41 -0800) it happened snipped-for-privacy@highlandsniptechnology.com wrote in :

We'd teleport to Mars before dinner to gets some Martian rabbits:

Lots of people have been trying to do this, using solid state devices for navigation, and it is no good by a factor of 100+. Maybe one day.

Too much drift.

The temp stabilisation, typically +65C, doesn't produce very reliable electronics too, due to the thermal cycling.

Yes; you can't do this with mechanical gyros. They topple, hit stops, etc.

On a sunny day (Thu, 11 Feb 2021 14:36:59 +0000) it happened Peter wrote in :

Since I actually measured that stuff I have to disagree. As to thermal cycling, why cycle? My project with that raspberry pi had an uptime of > 220 days or so, could have left it on, but was moving house, now it is back on on a UPS. The tritium decay project with build in temp control was on for many years from 2013 to end of last year:

full battery backup (twice, added lipos later), stopped only because I had enough data.

All these small things need very little power to keep at some elevated temperature. MEMS... TCXOs etc

There are often simple solutions for all those, often hypothetical, problems.

I noticed that he liked to do rolls clockwise, which probably biased the gyros.

Frank had a wild snap roll. He let me fly straight up into a vertical stall and come down backwards. That was cool.

I'm guessing that an artificial horizon is a slow averaging response to the gravity vector, so maneuvers can fool it. No affordable gyro is going to be set on the ground and remain pointed at the center of the earth for long, especially in a Aerobat.

MEMS accelerometers probably use electronic averaging, same problem. Time constants are apparently in the minutes range.

There must be wires or slip rings or something to power the gyro in an artificial horizon. Shipboard gyrocompasses float their gyro inside a sphere, in a pool of conductive liquid, and use the liquid for conduction. So there's no friction. But people don't fly ships upside down.

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John Larkin      Highland Technology, Inc 

The best designs are necessarily accidental.

On a sunny day (Thu, 11 Feb 2021 08:44:04 -0800) it happened snipped-for-privacy@highlandsniptechnology.com wrote in :

You are aware that those chips are in every [toy] drone right? reaction time is milliseconds, to keep the thing horizontal.

From MPU-6000/MPU-6050 Product Specification; (PS-MPU-6000A.pdf google it)

5 Features 5.1 Gyroscope Features The triple-axis MEMS gyroscope in the MPU-60X0 includes a wide range of features: Digital-output X-, Y-, and Z-Axis angular rate sensors (gyroscopes) with a user-programmable full-

External sync signal connected to the FSYNC pin supports image, video and GPS synchronization Integrated 16-bit ADCs enable simultaneous sampling of gyros Enhanced bias and sensitivity temperature stability reduces the need for user calibration Improved low-frequency noise performance Digitally-programmable low-pass filter Gyroscope operating current: 3.6mA

Factory calibrated sensitivity scale factor User self-test

5.2 Accelerometer Features ...

------- It also says: "The part features a robust 10,000g shock tolerance, and has programmable low-pass filters for the gyroscopes, accelerometers, and the on-chip temperature sensor."

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10,000 g is a lot...

And that is an older chip, I am sure better ones are now available. And no I have connection and have no shares in InvenSense...

Why does he even bother with an artificial horizon? He is not going anywhere, just up and down. Save the wear and tear. Cage the attitude indicator.

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The best designs are no accident - sw

You're right about the averaging. It is not difficult to get time constants of minutes in digital processing of electronic sensors.

The traditional aircraft gyros run on air pressure, or actually suction. There is usually a vacuum indicating instrument on the panel for monitoring.

For redundancy, the turn rate indicator is usually electrically driven. Due to the limited movement of the gyro frame, it is pretty easy to feed electricity to the motor without needing brushes.

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-TV

But in a moving airplane, the gravity vector does not point at the center of the earth. People die from that difference.

I wonder if the electronic attitude indicators have a manual zero reset button. Something has to reset the integrators.

An accelerometer doesn't tell you if you are horizontal. It tell you that you think you are horizontal.

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John Larkin      Highland Technology, Inc 

The best designs are necessarily accidental.

Beats me. I just saw him tweak the instrument now and then, in rare moments of level flight.

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John Larkin      Highland Technology, Inc 

The best designs are necessarily accidental.

[...]

The venturi are subject to icing, so they fail when you need them the the most.

Pitot tubes for airspeed indicators are also subject to icing, which brought down air France flight 447. They did not turn on the pitot heaters.

Wires bias the gyro frame leading to precession which generates error.

The Malibu has a vacuum pump to drive the attitude indicator. There are no wires attached to the gyro.

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The best designs are no accident - sw