737NG Offside Tuning Light
 

Can someone smarter than me please explain exactly what the ‘Offside Tuning Light’ on the 737-NG is telling me?
The FCOM says “ Illuminated (white) –

• the radio normally associated with this panel is being tuned by another radio tuning panel, or

• the radio tuning panel is being used to tune a radio not normally associated with this radio tuning panel.”

Thank you in advance :)

Assuming you have a typical setup with three RTPs, so left one will be VHF1, right one VHF2 and somewhere else there will be VHF3 - that is the normal setting for each of those panels.

If you now select VHF2 on the left RTP, the offside tuning light will illuminate on both the left and the right RTP, signaling:

• On the left RTP: that it is used for VHF2 instead of VHF1
• On the right RTP: that VHF2 is now also selected on the left RTP

Generally you should avoid using RTPs in a way that brings up the offside tuning light, except if you need HF or you have a failed panel/radio.

Umm, why? As long as both pilots know what's going on, use the panels in a way that makes sense to you!

Personally I just lean over, but each to their own!

Your method doesn't make sense to me! :}

Why’s that? If you can control all the radios from your panel, why reach across the cockpit?

Typically because in the event of an interruption in the process, like making or receiving a radio call, the switcher forgets to return tuning to the appropriate side. Now the offside tuning light remains illuminated, and no-one knows (immediately) why.

Conversely the offside tuning technique might be used if the the PF (helpfully?) tunes a new frequency while the PM uses the transmit switch on their side Audio Control Panel...

I see. You’re talking about a temporary use. I was envisioning a scenario where the FO would just keep his panel on com 1 (assuming all ATC transmissions are on com 1).

And then if you have an emergency descent, or any kind of other emergency where you have to promptly switch PF/PM roles, there's an additional distraction and increased workload in figuring out which radio is set where.

Not really. At my company, ATC is always on com 1. Com 2 is on guard unless it’s being used for something else.