View Full Version : Omni vs uni directional lights!
PPRuNeUser0211
30th Nov 2006, 10:35
This slightly random question came up in conversation with a civvy the other day. Why are 2/3rds of runway lights (in my limited night experience!) uni-directional, so you can't see them downwind at night and therefore have to guestimate the location of the runway?
c-bert
30th Nov 2006, 12:33
This seems fairly obvious to me. It's so you can see the location of the runway without being confused as to whether you are up wind or down wind of the active.
chevvron
30th Nov 2006, 13:15
'cos the MOD likes to illuminate 3 bulbs for every 1 used on a civil runway, thus using more electricity for the same job. Don't forget runway edge light fittings on MOD airfields are spaced closer than civil ones too, (30m instead of 60m)so there's more of them.
PPRuNeUser0211
30th Nov 2006, 15:00
C-bert, did think of that, but then thought surely they'd give us credit for a little more SA?!
Chev, didnt know that! but still doesnt come any closer to the real reason......
Do they still have ATC putting out the LE58's as well??
VEEPS
sirsaltyhelmet
1st Dec 2006, 14:55
Do they still have ATC putting out the LE58's as well??
VEEPS
Not here thank god...
Aren't the lights uni directional to show Main Instrument Runway?
PPRuNeUser0211
1st Dec 2006, 15:30
maybe maybe, but then you'd think if you were using the main instrument runway it'd be pretty obvious anyhow? Certainly if you were 180 deg out I'd be worried!
Raven30
1st Dec 2006, 15:45
Not sure of the official reason why they are uni-directional without wading through the manuals, but widen the question slightly and ask why are the approach lights uni-directional. Would the answer to that question also answer your query??
Just a thought.
Raven
StopStart
1st Dec 2006, 16:52
Runway lights?? Madness! You'll be wanting it tarmacked next...
:}
sirsaltyhelmet
1st Dec 2006, 17:00
maybe maybe, but then you'd think if you were using the main instrument runway it'd be pretty obvious anyhow? Certainly if you were 180 deg out I'd be worried!
Why would it be obvious? Well other than the fact that there is a CL5B at one end ie the main instrument runway and the reciprocal runway non main instrument runway has a CL2B.
SAR Bloke
1st Dec 2006, 17:34
I thought it was because unidirectionals are brighter, therefore, they are used to assist with the more critical part of approach and landing.
The omnis are there to give you a bit of SA whilst in the circuit or joining from an odd direction. They do not need to be as bright.