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Yellow Cabin Lights  
User currently offlineATLflyer From United States of America, joined Jan 2006, 736 posts, RR: 0
Posted (8 years 1 week 16 hours ago) and read 1974 times:

I flew to Miami last Thursday and back to Atlanta this morning on Air Tran, and I noticed that on both planes the light covers had turned a dark, unattractive yellow color. Parts of thel light cover looked ok, but the majority was a yellowish color. Does anyone know why lights on airplanes turn this particular color? Also, it seems to me that I only notice this on Boeing planes; Airbus seems to always have clean, white light.

7 replies: All unread, jump to last
 
User currently offlineEMBQA From United States of America, joined Oct 2003, 9364 posts, RR: 11
Reply 1, posted (8 years 1 week 16 hours ago) and read 1955 times:

For the same reason overhead florescent lights do the samething. The light effects the plastic and causes it to brittle and turn yellow.

[Edited 2006-09-11 03:25:55]


"It's not the size of the dog in the fight, but the size of the fight in the dog"
User currently offlineLincoln From United States of America, joined Nov 2004, 3887 posts, RR: 8
Reply 2, posted (8 years 1 week 16 hours ago) and read 1932 times:

Quoting ATLflyer (Thread starter):
Does anyone know why lights on airplanes turn this particular color?



Quoting EMBQA (Reply 1):
For the same reason overhead florescent lights do the samething. The light effects the plastic and causes it to brittle and turn yellow.

More percisely, IIRC, it's the UV output of the lights which causes the plastic to change color as well as become more brittle. It also causes colored paper to fade (witness any display in a school/office building).

Lincoln



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User currently offline777WT From United States of America, joined Jan 2005, 876 posts, RR: 1
Reply 3, posted (8 years 1 week 16 hours ago) and read 1932 times:

Either it's the heat from the light causing the plastic to turn that color or it's the plastic turning brittle as a result.

That happens to lamp covers in offices too.


User currently offlineATLflyer From United States of America, joined Jan 2006, 736 posts, RR: 0
Reply 4, posted (8 years 1 week 15 hours ago) and read 1886 times:

Then why does it only seem to happen on Boeing planes and not Airbus?

User currently offlineEMBQA From United States of America, joined Oct 2003, 9364 posts, RR: 11
Reply 5, posted (8 years 1 week 15 hours ago) and read 1858 times:

Quoting ATLflyer (Reply 4):
Then why does it only seem to happen on Boeing planes and not Airbus?

The type of plastic used for the lens...
The age of the aircraft...
The type of bulb used...

Also, many newer aircraft are going the LED bulbs.

Quoting Lincoln (Reply 2):
Lincoln

Yup, I just didn't want to go that deep... but glad you added it.



"It's not the size of the dog in the fight, but the size of the fight in the dog"
User currently offlineWarreng24 From United States of America, joined Nov 2005, 707 posts, RR: 0
Reply 6, posted (8 years 1 week 15 hours ago) and read 1813 times:

It is correct.

Most aircraft use florescent lighting. Florsecent lighting is very common, cheap, and is very energy efficient (compared to incandescent lights).

However, florescent lighting provides a very large spectrum of light waves. Most are towards the upper end of the visible spectrum.

The florescent lights have a layer of phorphorus on the inside of the blub. This phorphorus flilters out all the wavelenghts that are above the visible light waves. This is mostly ultra-violet light. Sometimes as the bulb's age, the phorphporus ages as well, and allows a greater amount of ultra-violet light through.

Ultra-violet light adversely affects plastics. It clouds them, yellows them, and makes them brittle. Look at most car head lamps. The lenses are sometimes made of plastic. As the car ages (and is affected by ultra-violet light from the sun) the plastic will turn yellow or get cloudly. This is especially true of "clear" plastics.

The plastic resin used by Boeing's suppiler must be more supectiable to yellowing than the plastic resin used by the Airbus supplier.

On the other hand it may just by the bulbs. Warm White florescent bulbs produce a "warmer" more reddish-yellow light. Cool White florescent bulbs produce a "cool" more pure "white" light. AirTran (as the OP mentioned) might prefer using the Warm White bulbs.  Smile

As we move to LED based lighting, the yellowing of the plastic shouldn't occur as LED's emit a much narrower spectrum of light (more visible light and not as much ultra-violet).


User currently offlineTod From Denmark, joined Aug 2004, 1725 posts, RR: 3
Reply 7, posted (8 years 1 week 3 hours ago) and read 1610 times:

Quoting Warreng24 (Reply 6):
Warm White florescent bulbs produce a "warmer" more reddish-yellow light. Cool White florescent bulbs produce a "cool" more pure "white" light. AirTran (as the OP mentioned) might prefer using the Warm White bulbs

Most operators chose warm white because they feel it makes that cabin appear less stark. CX is one of the few that go with cool white.

Quoting Warreng24 (Reply 6):
As we move to LED based lighting, the yellowing of the plastic shouldn't occur as LED's emit a much narrower spectrum of light (more visible light and not as much ultra-violet).

And the LED systems allow for ajdusting the color as required.

Tod


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