C172- how gauges lights and radiopanel lights are switched on?

[trakon]

Sorry for the silly question, but I am trying to build C172/C182 dimmer potentiometers for the instrumentation /radio panel lighting and I realized, I don’t know how the gauges lights are switched on/off. I know they are dimmed by two couples of concentric shaft potentiometers allocated left of throttle. But how/ when they get powered on/off in the real airplane. Within the flight sim they go on when I switch nav lights button. Does it work same way in the real plane too or they are illuminated right from the beginning when battery switch is engaged. Or dimmer potentiometers themselves are with switch on/off? Thanks.

[hyamesto]

Hi trakon:
In the real C172/C182, the NAV button only turn on the external navigation lights (Red and Green in wingtips and White in the tail stinger).
You have too a Beacon Switch (pulsating red light in top of tail), and Anticollision or Strobe Lights Swicht (Flash type lights in wingtips together with Navigations lights).

The manual say:
"The flashing beacon should not be used when flying through clouds or overcast; the flashing light reflected from water droplets or particles in the atmosphere, particulary at night, can produce vertigo and loss of orientation."

Others manuals says only the flashing or strobe lights (anticollision) must be turned off, and the beacon must be on all time (even after start, and before shutdown engine)
With FSUIPC, you can control each separately. In FS2004 or FSX interface the beacon and anticollision lights are operated by one switch for simplicity.

The dimmers don´t have an on/off switch.

The Instrumentation and radio panel lights, are controled by dimmers, and the dimmers are powered by Primary Bus, that it´s on when battery switch is engaged,
and are independent of the Avionics Swicht status.
If you need, i have the Complete Pilot´s Operating Handbook of a C-182RG in pdf format with the electrical system description and squematics.
Let me know, and i send you a copy.
Sorry if my english it´s no good.
Regards.
Horacio.

[trakon]

Hi,
Thank you so much for your brilliant explanation. Now I know how to make dimmers work the right way. Thank you once more.

[crossaint]

The dimmers are a little bit more complicated:
Radio dimmer controls backlighting of the bezels in the radio stack
Panel dimmer controls the instruments' illumination, but not the magnetic compass!
Pedestal dimmer controls the small lamp above the fuel selector, and the compass
Glareshield dimmer controls the light in the glareshield.
These pots control the output voltage of a voltage regulator (LM317) feeding the lamps.

And there is another one:
In the pilot control wheel is a small light to illuminate a map on the pilot's knees. There is also a rheostat controlling its brightness. This map lamp is only on if the nav lights (red-green-white) are on.

[Xpendable]

I have only 1 thing to add to what the others said. This applies at least to the 172R and 172S (which I have a combined total of about 300 hours in)... the 2 knobs to the left of the throttle actually have an outer dial and an inner dial. So each dial actually controls 2 separate lighting functions depending on whether you turn the outer dial or the inner dial. I can never remember which one is which... When I'm in the real airplane, I just adjust each one until I get all the lighting the way I want it. The POH refers to these dials as rheostats.