Electrical Q

[West Coast]

Seems I need a memory jogger to remember all the memory joggers...


Way back when I remember hearing something to aid in remembering how SOV's failed (open/closed) depending on source of power.

Something along the lines of "AC lies, DC dies" or something close to that. I'm comfortable with the concepts of AC and DC but its killing me that I can't remember the saying.

Any help?

[gas-chamber]

Maybe that's too general, and still requires you to know the power source in the 1st place, so maybe not practical in application. Usually, where the valve fails when power is lost is linked to the need for that system to be 'fail-safe'. Thus, anti-ice valves will often fail to the on position, pressurization ditto, so that when you suffer a major electrical loss you can at least continue in cloud and breathing normally. Others fail to off to conserve power. Sometimes the off position on the valve is the on position for the system - to both conserve power and fail safe the system. Others will fail in position selected - e.g. often the crossfeed does this, as you can work around it with selective use of boost pumps.

[Old Smokey]

West Coast,

Perhaps it was fortunate that you did forget, because, as gas-chamber indicates, it's a far too general statement, and will not apply to all aircraft. The 'rule' that you state did apply to one 1950's type that I flew, but not to any subsequent aircraft.

Now, if you're talking about indications of a FAILED AC Synchronized or DC synchronized (dessyn) instrument, that's a different matter altogether.

Happy Holidays,

Old Smokey

[West Coast]

I agree with both of you, however its the memory jogger I'm in search of here.

[catchup]

Listen to a couple of AC/ DC songs. Maybe this helps.

regards