It seems to me that we have heard these arguments before.  Let me see if
I understand them.

1.  A certified EFIS system is better than an uncertified one, which
seems reasonable.
2.  The Chelton certified system is therefore likely to prove more
reliable than any uncertified system.
3.  Because it is so expensive, and outside the budgets of many of us,
Chelton produced a non-certified version.  Contrary to what had been
inferred, this system does not use identical hardware to the certified
version.
4.  However the Chelton non-certified version is claimed to be
demonstrably better than all the other non-certified EFIS systems out
there, and we should all stay clear of the others for IFR flight.

This would sound a lot more credible if we had not just heard that the
Chelton non-certified version has been using an AHRS that has been
failing catastrophically on a regular basis.  Sorry, but I really do not
buy the argument.  If you can afford the certified Chelton system, you
are lucky, and it will probably be very reliable.  If you cannot, the
Chelton non-certified system has proven to be no different from the others.

Surely the key point is that with any of these systems, certified or
otherwise, you must have back up instrumentation, and you have to
conduct regular cross checks in flight, particularly in IFR.   I have
been let down by some much more expensive and better tested
instrumentation  than any of our EFIS  systems, certified or otherwise.

By the way, Sagem is a highly reputable and well established company and
certainly comparable in most respects to Chelton's parent company.  I
have nothing against Chelton, they are a good company with a good
product base, but let us stop knocking every competitor in the market.
There is room for the competition, and Chelton has been shown not to be
perfect.

Jerry Fisher