Little Plus symbols on avionics

[Stingman]

What are the little plus symbols on some avionics equipment for? Some seem to have a tiny little '+' at various places on radios and other do-hickeys which screw into panels.

 

[Timebuilder]

Often, the "+" is used to indicate a resultant increase in a value when a control input is made, such as an increase in radio volume.

 

[ATRCA]

Ok, this will sound very far fetched, but;

On the EMB 135/145 I was told during training that the small "+" was were the backlighting was grounded. Hence, if the lighting is not working properly, this is where you "tap" to attemtp to restore lighting.

Havnt tried it yet. Havnt had to so far.

Anyone else want to give it a try?

 

[Boeingman]

ATRCA, I'll agree.

 

[abexpilot]

I will second the above.

P.S. Speaking of panel backlighting, here's a dirty trick to play on (A) crew you don't like and (B) those who don't already know better.

If your plane has an autopilot engage paddle like on the DC-9/8's and probably the MD-80's, engage the autopilot, get the sucker to "feel how hot the back lighting makes the area just below the paddle", when they feel it, kick the autopilot off with the yoke disconnect button. If all goes well, it will smash their finger.

 

[Tim47SIP]

Coming from Boieng and Collins itself, and also a very good military question during orals. The little + symbols are alignment marks for the rest of the lettering on the radio. This is where the equipement that either paints, overlays, applies stickers, etc is alligned so that it is centered on the equipement. The pluses are not centered, but are in various locations due to different manufacturing processes. I actually watched this at the factory that produced radios for Boeing's CH-47/BV-234 15 years back. I didn't believe it to be true, so when picking up aircraft at the factory, I was shown this procedure. So now you know the rest of the story!

 

[Timebuilder]

I guess I was thinking about some different "+" marks.

Interesting.

 

[rudderdog]

I will second the above.

P.S. Speaking of panel backlighting, here's a dirty trick to play on (A) crew you don't like and (B) those who don't already know better.

If your plane has an autopilot engage paddle like on the DC-9/8's and probably the MD-80's, engage the autopilot, get the sucker to "feel how hot the back lighting makes the area just below the paddle", when they feel it, kick the autopilot off with the yoke disconnect button. If all goes well, it will smash their finger.

You must be from the Kentucky.

 

[Speedtree]

or it's a phillips head screw.