The stratux folks are working on a AHRS using an IMU like that.
I think the dedicated device Peter and I were discussing is a much simpler solution than any software based approach that does a lot more than rate of turn.
We are really trying to remove a complex and failure prone mechanical device and replace it wth a “plug compatible” alternative, no more.
I was not expecting such an elegant option to arise – these sensors look very very promising.
Also found someone on the pprune forum who apparently has tested solid state TCs (but not in relationship with an autopilot).
I am not yet in touch with him personally but his posts seem to confirm that the solid state solution will be far better than a mechanical gyro.
Apparently much less sensitive to turbulence, more symmetrical behavior etc…
He says that the vertical axis of the TC is mounted with a 35 angle forward in order to generate a blended signal from yaw and bank inputs.
In an ideal world we’d find a supplier willing to produce a 1:1 replacement with adequate resolution and full swing voltage
I wonder if it could be legally installed with a switch so that the mechanical TC remains in place.
I wonder if it could be legally installed with a switch so that the mechanical TC remains in place
In general this is not strictly legal because any change in what feeds an autopilot (and the pilot needs to know about) needs an amendment to the autopilot AFMS (the pilot’s handbook). The other thing which gets you is another strict interpretation of the regs: any connections not shown in the IM are illegal.
A lot of people have been up this road before, on stuff like a KI256 replacement (that one is worth way more $$$ than any other GA gyro replacement). To legalise it you would need at least a field approval (if N-reg) and a new AFMS which would need an approval by an ACO. I did that here but these things are very hard to do from Europe.
the vertical axis of the TC is mounted with a 35 angle forward in order to generate a blended signal from yaw and bank inputs.
Yes; that’s how the TC works. It’s fairly crude. This is why I said you might need to do some software, but if you can get a rate of turn directly, that’s even better. BTW I heard the STEC TC output voltage is relative to the reference voltage, not to aircraft ground.
Thx Peter. Comment about floating voltage reference well noted.
I have read some rather detailed posts by someone called flyer101flyer on the pprune forum. My present assessment is:
1. Mechanical TCs have huge issues that will vanish in the solid-state version.
2. The current state of the available technology is such that building a prototype will be very easy and inexpensive
3. Disregarding certification issues it seems that the idea makes a lot of sense from a manufacturing perspective.
I believe the best way forward is to
1. procure/install both device types on a turntable, compare output to roughly calibrate the output of the piezo version.
2. Install both devices on a board, connected to a laptop for data acquisition take it flying.
My Extra 400 is very useful for that: one can easily affix a test board on a rear facing seat in front of the “engineer”, a 24 V socket is installed in the cabin and there’s even a spirit level integrated in the cabin door so the straight and level pitch angle can be correctly set.
