When I went to A&P school, I remember that the L-1011 had partially
electronic engines (the R-R RB211): they were mechanical up to 92% or
so power and fuel flow was modulated from there. In the event of total
electrical or ECU failure you had power fully throttleable from idle
to approximately 92%. My father was an L-1011 F/E and F/O and he says
that's as he remembers it, but he no longer has manuals. We were
taught that FADEC engines-turbines, that is- had redundant computers
but in case of total electrical failure the engine would stay at its
last power setting but with changes in altitude or airspeed you would
get power changes because fuel flow would be constant. Your only
option would be to shut off fuel flow by a manually actuated valve, if
there was one.

It would be very easy, in the case of recips, to just use the EEC to
trim the existing ignition and fuel injection systems instead of going
to full electronic option. I don't know why that option isn't pursued,
or the replacement of _one_ magneto with an electronic system. Common
sense, it would seem.

I do think single pilot IFR with passengers should require single
lever power control. I've thought that for twenty years. Otherwise,
make 'em carry a rated pilot or a Piston F/E in the right seat. (I got
my 727 F/E rating before my private ticket-privilege of being an
A&P-did little good though, but used up my GI Bill benefits in a fun
way.)