well - blue and brown I guess...
Solid state gyros are not yet suitable for use as directional gyros for any length of time (even the very good ones we use in our premium SP-9 AHRS).
However, they are largely no longer needed.
Our SP-6 magnetometer has become so good over the years it gives you accurate heading even during turns. It is calibrated to your aircraft and installation location in flight using a procedure quite similar to what you use to (sort of) calibrate a mobile phone compass (i.e. fly a series of figure eights at various bank angles until the compass tells you it has enough data to calculate a correction matrix that represents the total hard and soft iron magnetic deviation created by your aircraft in three dimensions).
You can get accuracies to 1 degree or so in any direction and any attitude. As your aircraft's magnetic profile can change you may have to repeat this once in a while (but it is quick and fun to do).
The interesting part of the SP-6 is that the algorithm used in the SP-6 does not need to know the aircraft's attitude with respect to the Earth to do the calibration so any errors normally caused by attitude not being 100% correct do not affect the calibration result at all...
So - it effectively does what your DI used to do - except you do not have to set it to the current heading since it knows it...
It also never topples or needs caging.
The small version of this exists - it is our Vega AHRS.
Then - have a look at the Razor head just released for the MGL V16 radio - that also fits a 3.1/8" hole but with a nice and big 3.2" touch screen. Needless to say - that is going to become a whole new series of instruments as well - and even a OEM version where you can make your own, we provide the hardware and the thing has two empty PCB slots where you can plug in your own hardware if needed (whatever interfacing needs you may have etc). It runs a STM32F7 processor (for those that know what to do with those things) and comes with a "hello World" program in source you can use as a base for your own instrument...
Rainier
CEO MGL Avionics
