King Air Switches

[IHL]

I posted this on "Tech Log" but got no replies; thought I would try here.

On King Airs some switchs have a white circle around the switch eg. Eng Auto Ignition, Engine Anti Ice.

The left pitot heat switch has a white circle the right pitot heat does not.

I have heard various explanations of why, but I'm still not sure.

Any replies would be welcome.

[kitekruncher]

White Ring around a switch denotes equipment and systems are powered from the center AND triple-fed bus bar on the F90. IE right pitot heat is fed off the right generator bus but the left pitot heat is fed off the Center and Triple fed bus bar.

I imagine 200s without the triple fed bus bar system will have white collars for similar reasons. Also I think a purpose is to aid the grey matter when load shedding during electrial emergencies?

maybe worth a read of your flight manual for further enlightenmeant?

[Black Maria]

IHL

On the King Air B350/300 series the white circle denotes that electrical equipment which remains operable in the event of a dual generator failure (ie: powered solely by the battery).

With all those switches in the on position and both generators off, the battery life will be approx 30minutes (based on a 50amp load and a 75% battery capacity).

I would imagine that this would be the case for other King Air models.

[604guy]

In other words...stuff that's on the triple fed bus.

[max6462]

same on the 1900.:sad: