Boeing Chart (Map) Lights - B737NG and Classic B737 Types
/Chart lights removed from a Boeing 737-800 NG airframe. Colour, appearance and design is different to the the older style lights used in the classic airframes
Chart lights (also called map lights) are attached adjacent to the overhead panel and are used to illuminate, in particular, the chart holders attached to the yoke during night time operations. There are two lights, one on the Captain-side and the other on the First Officer-side.
The light from the unit can be focused from a wide angle to a narrow beam by twisting the focus ring at the front of the light. Each light can also be swiveled and moved vertically to position the light beam in a particular place on the flight deck (for example, chart plates).
The switches (knobs) that turn the light on and off are located on the sidewalls of the Captain and First Officer side of the flight deck. The light can be dimmed if necessary by rotating the knob.
The chart lights are mounted near each the eyebrow windows.
Chart light removed from a Boeing 737-400 airframe. The light has a differing focus ring, appearance and colour to the NG style (click to enlarge). I believe this style of chart light is also used on the B747 aircraft
Two Styles (Classic and NG)
To my knowledge, there are two styles of chart light that have been used in the Boeing 737. The fatter style used in the classic series airframes and the more slender style used in the in the Next Generation airframes. I have little doubt that there may also be small differences between light manufacturers.
The main aesthetic difference between the older 737 classic airframe chart lights and the newer Next Generation style is that the older lights are squatter and a little fatter in shape; the Next Generation is longer, more slender-looking and has a smaller footprint.
Chart light showing reflector dish on inner side of end cap. This style is the older light type used in the 737 classic airframes
Other differences are internal and relate to how the light is focused on the lens and the physical shape of the focus rung used to alter the angle of light coverage.
Ingenious Design
Both style lights have an ingenious design to allow the light to be focused. Removing the rear plate of from the older style light reveals the inner side to be a circular reflector dish (see image) which evenly distributes the throw of light when the unit is set to wide angle.
The newer Next Generation style lights use an aperture blade which either enlarges or contracts as the focus ring is turned. This design is identical to how a camera aperture works.
Both styles can use either a 12 or 28 Volt bulb; the later will generate a brighter light. Connection is direct to the power supply (12 or 28 Volt). An interface card is not required.
The NG style chart light. A blade aperture controls the amount of light that is reflected onto the thick lens glass
Original Equipment Manufacturer (OEM)
Put bluntly, you cannot achieve a more realistic end product than when using a real aviation part. Genuine parts, although at times difficult to find, are built to last; if they can withstand the continue abuse of pilots in a flight deck then they are more than adequate for home simulation use.
It's true that while some parts appear used with faded and missing paint, they can easily be cleaned up with a fresh coat of paint. Personally, I prefer the worn-appearance.
