Around here you can get them in any auto parts store. We've got a lot of general aviation activity here so that *may* affect things, but I would expect that if not on the shelf, they are in the local warehouse of any decent parts outlet. GE makes them, as does Wagner and probably other big bulb makers. The 5 3/4 inch diameter seems to be commonly sold as a replacement for KC type lights with sealed beams. There are also very similar units simply labeled as "spot lights". They have a slightly wider pattern. There are also 4 inch versions (I use these in rubber "tractor light" housings on rigs where I don't have room for a larger light ( under the front bumpers of the Saabs for example). There is also a larger unit which fits perfectly in a 7 inch round headlight mount. This one is called a "marine spotlight" in the manufacturers listing. Very nice reflector and lens, tight driving light type of pattern with an amazing amount of light thrown downrange and decdnt sidescatter too. This big one is kinda spendy for a bulb ($45). I have installed a pair of these in my dedicated trail rig (the big '40 that is still a Hanger Queen). Since it won't beon the road there isn't any need for low beams. The side scatter of this light illuminates the close in stuff as well as a low beam and the main patter really reaches out there when you are wandering the tundra and alpine ridges at night.
It has been a while since I actively looked at the lights on a Cessna of any size, but I think that most of the smaller ones will use the 4 inch light. The 5 3/4 would be found on slightly larger general aviation aircraft (light twins and such) on up to smaller commercial stuff. I have no iea what a B747 uses but I would expect that it would ge the big 7 inch light or something equivilent.
There is nothing exotic about these lights. They probably have a heavier filiment than lights not built/marketed for aviation use. The vibrations they will be subjected to in an aircraft are more severe than expected for automotive use and that will kill the filiments quickly. They are a higher quality bulb in terms of the reflector and lemes than any comparably priced bulb marketed to the automotive world (Basically only the cheap "made in China" KC knockoffs with the H3 bulbs fall into the same price range... Even when you factor in buying one of these cheap sets for the housng and throwing the guts away). You won't find any other small 100 watt driving lights that are actually acceptable as driving lights to put up against the 4 inch landing light. (I won't dignify the little 55 watt glorified parking lights that are sold everywhere by even cmparing them.) It's size is a big plus and it puts out as much light as the aforementioned KC knockoffs (the smaller size reflector is more than compensated by the quality of the refelctor).
Oh yeah... These lights are all sealed beams so water intrusion is not a concern. That's a big one for me becuase of all the water crossings our trails have.
Anyway, nothing exotic, just good quality, commonly available stuff for reasonable prices.
Mark...
