Re: Airliner lights

Date:         09 Mar 97 12:39:42 
From:         "john r." <john@guava.demon.co.uk>
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In article <airliners.1997.568@ohare.Chicago.COM>, Jean-Francois Mezei
<"[nospam]jfmezei"@videotron.ca> writes
>It seems that on a clear day, on can see the lights from an incoming
>airliner on approach that is still quite far.
>
>I assume that those are not your everyday headlight you would put on
>your car. What sort of power (watts) do these beasts consume ? How long
>would they normally last before they are replaced ?

I think most of them are 600 watts quartz units. They do not have a very
long life, I think it is around 30 to 40 hours nominal but as they are
cheap by aircraft standards no one worries. Its a chore for us
mechanics.

They are run from 28vac with a local transformer to reduce the 115v
supply, so keeping the cables lighter.

>Is there a special material/glass used to allow it to operate in extreme
>conditions and most importantly, fairly rapidly changing temperatures
>without cracking/failing ?

The lamp is mounted within a robust sealed beam unit and that makes them
tough.

>Are they designed solely "to be seen" or do they also help pilots see
>what is out there ?

Prime function is to see, however they are used on approach a lot to
signify on finals.

Its very dramatic at night going through patchy cloud with them on,
great white ghosts flit past and somtimes rear up and slam into you at
speed. Its pretty well the only way you can get an impression of speed
in an airliner.

--
john r.