Aviation Incandescent Bulbs

[AtomicSheep]

Does anyone know whether aviation incandescent light bulbs used for various cockpit lighting are special in any way? How precise do voltages need to be? How sensitive are they to ripple/noise/spikes/etc in the power supply?

 

[Comcokid]

Not special in any way. Standard 24 or 28 volt bulbs when they are incandescent, or 12V in smaller/older propeller planes. Many instrument manufacturers buy an industry standard bulb from a source known for higher quality, but you can probably find the same bulb at a local auto supply. Many instruments today are LED or CCFL or other types that may require an authorized service facility. Normal system voltage may be typically 18V (engines starting) to 32V max with normal voltage of 27 to 28VDC.

BTW - in the truck market they may call it 24V. In the aircraft market they call it 28V. In either case it's the same voltage equivalent to two 12V car batteries.

 

[IRstuff]

A lot of military aircraft used electroluminescent panels for the instrument backlights, since they need to be dimmable without changing color, which incandescent bulbs cannot do. The incandescents tended to be for button backlights, but I'm guessing they're been replaced with LEDs.

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[EdStainless]

Quality is important as vibration resistance is needed.
Some critical indicator lamps are dual filament, and some are deliberately run at low voltage to extend life (48V lamp run at 24V).
The other reason to use EL is that it is vibration proof (until a connector breaks). They also have a very long life.

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[AtomicSheep]

Thanks guys