737 overhead question

[Sean]

On the NG's FWD OHD, there is a 'thingy' between the ATTEND and GRD CALL buttons. It can be seen clearly in this picture.

http://www.airliners.net/photo/Air-Berlin/Boeing-737-86J/1023576/L/

Any ideas what it is? Volume slider?

I can't see any reference to it in the FCOM or Bulfer guide.

Cheers

Sean

[727737Nut]

That is the release lever to unlock the overhead to allow it to swing down.  Very handy!  When i had my real cockpit, that was a arm saver to latch the o/h up w/o having to hold it.

Rob

[Sean]

Excellent! Thanks for that.

Next question...

Staying with the FWD OHD, moving onto the EMER EXIT LIGHTS switch, which can be seen to be in the OFF position in the same photograph above...

The FCOM has the centre ARMED position as the guarded position. What stops the switch moving to the ON position when the guard is closed, as is the case with the FLT CONTROL switches? Different switch arrangement?

I notice in the photograph there is a steel tab between the ARMED and ON positions. Is this some kind of stopper, or perhaps a seperate switch for activating the emergency lights manually to ON?

Hope that makes sense!

Sean

[Jetcos]

It is a special switch guard, i have a real one. But most offsets are made to work around that and use a 3 position toggle and a Black Guard.

[jackpilot]

Have some like that, with the hole to guard the middle position.
You may also cheat by drilling a regular toggle guard at the right place (not easy)

[jackpilot]

Dean at Ruscool has what you (we) need...
http://www.ruscool.co.nz/atr_2.html

[Sean]

The Boeing ones don't have the hole in. Minor issue I know.

Incidentally, I think I came across the real ATR ones a couple of days ago, I'll have a check.

EDIT: That Ruscool one appears to be for a 2 position switch, and it holds the toggle in one of the extreme positions. The Boeing type will do the same. The Emergency Exit light switch is a 3 position and it's the centre position that's guarded.

[727737Nut]

Its an optical illusion, it's easy to replicate by adjusting the mounting depth of your switch.  The tab you see is there to wire the switch guard down if needed. If you notice the toggle is real low in the panel. Thats why when you push the guard down, it only goes to armed. 

Rob

[Sean]

Won't that tab hinder putting the switch on?

[727737Nut]

Thats why i said its an optical illusion, no it does not hinder it.  The switch is mounted really deep in the pnl so it makes it look like it hits it.  Hope that makes since.

Rob

[Garys]

That small tab is also a guard. It moves backward and fwd with the main guard. its sole purpose is to see to it that the switch cant be moved any further fwd than the armed position when the cap is closed. The switch can only be pushed manually into the on position when the cap is open. The reason for this setup is so not to  drain the battery if the switch is accidently pushed into the the on position by closing the cap as you normally would with any other guarded switch.

[Sean]

Thanks for all the input guys. I'm expecting my overhead next week and I'm trying to get to understand the real world one as much as I can.

The reason for asking about the Emergency Light Switch is that a friend has the Sismo overhead, and using their propriety software, with the guard closed the NOT ARMED light is illuminated, obviously because the guard is pushing the switch to the ON position. I didn't think that was correct, hence the researching.

My next overhead question, if I may continue...

It regards the Pull-To-Unlock Lever switches (made by Honeywell I gather).

Here's the list as I see it. Any comments, corrections or additions?

Fuel Pumps - 2 position - Locked out of centre position (or rather locked in both extremes)

Ground Power - 3 position - Locked in centre position (both extreme positions momentary)

Generator Switches - 3 position - same as ground power

Engine Anti-Ice - 2 position - same as fuel pumps

Hydraulic Pumps - 2 position - same as fuel pumps

Pack Switches - 3 position - Locked in all 3 positions

Isolation Valve - 3 position - Locked in centre position

Bleed Switches - 2 position - same as fuel pumps

The APU start switch I'm not sure about. It looks different to the Honeywell switches, Cutler perhaps? I know it's a 3 position, with the ON position being momentary, but is it locked in and out of the OFF position to prevent unwanting operation?

Thanks again.

Sean

[Garys]

Yep you are correct with all those switches. APU switch needs to be unlocked in and out of the off position as you suspected.