Chuck,
You can't use yaw in a C336/337. You have to use the knobs & dials to determine the failure. I reckon it's more difficult in one of these than in a 'conventional' twin. Also, what about multi's with more than one engine on each wing? Surely you're not advocating yaw alone be used to determine failure? (yes, there's nearly always a second pilot & probably an FE to do the determining....)
Re the mixture control breaking:
That the mixture lever happened to fail doesn't make this example supportive of your argument. There is the same outcome regardless of what device is used to 'fail' the engine. An idling engine is just as failed if the throttle lever breaks off & you can no longer restore useable power.
There is no single point failure protection built in to any of these classes of engine's controls, except perhaps single engine CSUs that default to max RPM (thereby enabling max power to still be available) if the governer gubbins go tits up. I'm ignoring the C208's manual FCU since this engine installation WAS designed to have some amount of backup.
I could argue a **possible** workaround in a few Piper twins that use the pressure x-feed logic eg Aztecs, Chieftans etc. The workaround would be to use the fuel selector to provide the 'failure'. This MIGHT have a backup in case the fuel selector handle broke, by selecting the x-feed switch to 'ON' - bypassing that engine's fuel selector - & allowing fuel to be fed from the other engine's supply.
I'm presuming in the above that OFF is bypassed by x-feed select. Not sure if this is the case anyway. All the manuals I've seen for these types require/presume x-feed is OFF when they mention switching the fuel supply off but none seem to say what would happen with x-feed on. I don't have any fuel schematics to view to work it out myself.
Just a thought...
