What are the gases used in electric lights?

What additional runway lights are used during ILS approach?

• http://abcnews.go.com/US/wireStory?id=2848034 In the above article additional lights are referenced that are used by pilots during an instrument landing. These are in addition to those which line the runway. What exactly are these additional lights they are talking about here? I fly commercially often and only see lights on the ramps and runways (but then I never see the runway on approach so maybe something from the air?)

• Answer:

  The lights referred to in the article are lights that basically extend the runway and provide the pilot a visual clue to the runway environment before he gets to the runway. Sometimes, a pilot will "break out" from under the overcast during an instrument approach over the runway and too high to land. There are various configurations, many of which use a flashing white strobe-light effect, (nickname - the "rabbit") giving the impression that the light is travelling toward the runway centerline. These lights are part of the "runway environment" which on being seen by the pilot, allows him to visually land the airplane without necessarily seeing the actual runway. As one of the previous responders mentioned, VASI (visual approach system indicator lights) provide the pilot a visual indication of whether he is above, below or on the glideslope. These would not be used during a precision instrument approach because the pilot would be gliding the plane down the glideslope by using a glideslope radio beam broadcast from the runway (the little orange and white house down near the end of the runway). For a complete guide to runway lighting see the Airman's Information Manual chapter at: http://www.faa.gov/airports_airtraffic/air_traffic/publications/ATpubs/AIM/Chap2/aim0201.html The article makes a good point - typically these runway extension lights are much brighter than the runway edge or centerline lights. Also, in fog, the flashing strobe shows up usually before the other lights do, as it's bright and moving. If you drive around a major airport, you'll usually see a series of towers extending out from the end of the runway. The lights are mounted on those towers. When you're shooting an instrument approach at night or in bad weather and those lights pop into view, it sure is a welcome sight!