Print from Airliners.net discussion forum
http://www.airliners.net/aviation-forums/tech_ops/read.main/325033/

Topic: B757 Emergency Exit Sign Question
Username: hagiograph
Posted 2012-11-06 08:18:08 and read 3356 times.

As I am finding myself sitting on more jets these days with little more to do than stare blankly off into space I have begun noticing the differences in cabins and their fixtures. Recently on a flight back home on a Delta 757 (if I recall correctly) I noticed the following type of exit sign:



and it looked like it was unlit throughout the flight. All the similar signs to this also looked unlit. Are these simply "electrical" lightbulb-based lights that are activated during an emergency or are they supposed to 'glow' during the entire flight? I know some emergency exit signage in various other places looks like it has some "glow-in-the-dark" capability but this type of light didn't look like that.

Topic: RE: B757 Emergency Exit Sign Question
Username: Mender
Posted 2012-11-06 11:36:17 and read 3356 times.

They are activated by the emergency lighting system and are simple electrical bulbs, not photoluminescent. You can find aircraft with photoluminescent floor path lighting which requires less maintenance than conventional 'bulbs'.

Topic: RE: B757 Emergency Exit Sign Question
Username: hagiograph
Posted 2012-11-06 13:43:21 and read 3356 times.

Mender, thanks! I was always curious why some signs appear to be "electric lights" or bulbs and some are those little red block "tritium signs" which, if I understand correctly, contain some amount of radioactive material and still others are the photoluminescent type of lighting that charges from incoming light and then glows a long time.

Topic: RE: B757 Emergency Exit Sign Question
Username: FlyDeltaJets
Posted 2012-11-10 01:43:51 and read 3356 times.

Quoting hagiograph (Reply 2):
if I understand correctly, contain some amount of radioactive material

  
you are correct

Topic: RE: B757 Emergency Exit Sign Question
Username: 1337Delta764
Posted 2012-11-10 15:55:20 and read 3356 times.

I wonder, which particular aircraft types have tritium signs? I know MD-80s have them, and I think some non-Signature Interior 767s have them as well (the white on red ones). What other aircraft types have them?

Topic: RE: B757 Emergency Exit Sign Question
Username: Dalmd88
Posted 2012-11-10 17:29:17 and read 3356 times.

The electric signs and path way lights are powered by dedicated battery packs that are powered on when armed and the aircraft power is lost.

Topic: RE: B757 Emergency Exit Sign Question
Username: HAWK21M
Posted 2012-11-11 11:22:18 and read 3356 times.

Quoting Dalmd88 (Reply 5):
The electric signs and path way lights are powered by dedicated battery packs that are powered on when armed and the aircraft power is lost.

To add they can be switched on if needed too.

Topic: RE: B757 Emergency Exit Sign Question
Username: hagiograph
Posted 2012-11-12 14:20:31 and read 3356 times.

Quoting FlyDeltaJets (Reply 3):

FlyDeltaJets,
I assume that the picture of the one I was looking at is NOT one that contains tritium or radioactive material, correct?

Topic: RE: B757 Emergency Exit Sign Question
Username: 1337Delta764
Posted 2012-11-12 17:46:01 and read 3356 times.

Quoting hagiograph (Reply 7):
I assume that the picture of the one I was looking at is NOT one that contains tritium or radioactive material, correct?

No, that one contains incandescent bulbs. I have seen them lit once while we were on the ground at ATL at one point. Typically, tritium signs are white on red, rather than red on white like image you posted.

Topic: RE: B757 Emergency Exit Sign Question
Username: AA737-823
Posted 2012-11-12 21:43:29 and read 3356 times.

Quoting 1337Delta764 (Reply 4):

I wonder, which particular aircraft types have tritium signs? I know MD-80s have them, and I think some non-Signature Interior 767s have them as well (the white on red ones). What other aircraft types have them?

Some of the late model 737-200's had them, and I think LOTS of the 737-Classics had them, but for the NG, they reverted back to incandescent light bulbs. Evidently all of United's Global Service whiners were getting ankle cancer when they sat in the exit row window seats...........  
Quoting hagiograph (Reply 7):
I assume that the picture of the one I was looking at is NOT one that contains tritium or radioactive material, correct?
Quoting 1337Delta764 (Reply 8):
No, that one contains incandescent bulbs.

Indeed, they're incandescent in that assembly, and much smaller than a pencil eraser. They also burn out a lot, and run at just 6 volts DC. They're seriously tiny- maybe the diameter of the tip of a small headphone plug.

Topic: RE: B757 Emergency Exit Sign Question
Username: hagiograph
Posted 2012-11-13 06:11:01 and read 3356 times.

Quoting 1337Delta764 (Reply 8):
No, that one contains incandescent bulbs. I have seen them lit once while we were on the ground at ATL at one point. Typically, tritium signs are white on red, rather than red on white like image you posted.
Quoting AA737-823 (Reply 9):
Indeed, they're incandescent in that assembly, and much smaller than a pencil eraser. They also burn out a lot, and run at just 6 volts DC. They're seriously tiny- maybe the diameter of the tip of a small headphone plug.

Thanks!

[Edited 2012-11-13 06:12:02]

Topic: RE: B757 Emergency Exit Sign Question
Username: 1337Delta764
Posted 2012-11-13 09:35:09 and read 3356 times.

Quoting AA737-823 (Reply 9):
Some of the late model 737-200's had them, and I think LOTS of the 737-Classics had them, but for the NG, they reverted back to incandescent light bulbs. Evidently all of United's Global Service whiners were getting ankle cancer when they sat in the exit row window seats...........

Where are the tritium signs located on 737 Classics? Every 737 Classic I have been on has the same type as that 757 sign in the OP's post.

Topic: RE: B757 Emergency Exit Sign Question
Username: Mender
Posted 2012-11-14 01:34:05 and read 3356 times.

Quoting 1337Delta764 (Reply 11):
Where are the tritium signs located on 737 Classics? Every 737 Classic I have been on has the same type as that 757 sign in the OP's post.

I have seen at least one 757 with some tritium signs on the hatracks next to the exits. Why, I've no-idea, but it had incandescent bulb signs in the ceiling as per the OP and small tritium sign in the doorways.

Thinking about it, the aircraft wasn't being operated by the original customer who had specified the aircraft at build. Maybe some of the lavs and galleys had been re-located so that it had the same layout as the rest of the aircraft in their fleet. In this instance it would be easier to install tritium exit signs rather than wiring in new incandescent signs where they hadn't previously been installed.

Topic: RE: B757 Emergency Exit Sign Question
Username: AA737-823
Posted 2012-11-18 16:55:50 and read 3356 times.

Quoting 1337Delta764 (Reply 11):
Where are the tritium signs located on 737 Classics? Every 737 Classic I have been on has the same type as that 757 sign in the OP's post.

Floor-level guidance signs, I.E., the floor-level signs at the overwing exits, as well as 1R/1L and 2R/2L doors, and the center aft guidance light, mounted to the base of the F/A jumpseat.

Quoting Mender (Reply 12):
I have seen at least one 757 with some tritium signs on the hatracks next to the exits. Why, I've no-idea, but it had incandescent bulb signs in the ceiling as per the OP and small tritium sign in the doorways.

The tritium units last a long time with virtually no maintenance, which compares favorably to the incandescent equivalent, which requires at least one of its 21 bulbs to be replaced pretty dependably at every monthly check.

Topic: RE: B757 Emergency Exit Sign Question
Username: A36001
Posted 2012-11-19 17:23:30 and read 3356 times.

Hi all,

Why is the floor lighting red at a exit? Shouldn't this be green, given that green in most parts of natural thinking is a go or safe to go signal. In a dire emergency I would of thought most people would respond better if they see what they normally see. Meaning... red light = no entry - green light = safe to go.

Have a nice day  

Topic: RE: B757 Emergency Exit Sign Question
Username: tdscanuck
Posted 2012-11-19 19:16:58 and read 3356 times.

Quoting A36001 (Reply 14):
Why is the floor lighting red at a exit? Shouldn't this be green, given that green in most parts of natural thinking is a go or safe to go signal.

The US used, and still uses, red for exit signs and that carried over into aircraft exit lighting.

The 787 switched over to the international standard green.

Tom.

Topic: RE: B757 Emergency Exit Sign Question
Username: HAWK21M
Posted 2012-11-20 02:49:09 and read 3356 times.

Quoting tdscanuck (Reply 15):

The US used, and still uses, red for exit signs and that carried over into aircraft exit lighting.

The 787 switched over to the international standard green.

Whats the US justification for this...Out here its Green.

Topic: RE: B757 Emergency Exit Sign Question
Username: Fabo
Posted 2012-11-20 03:18:38 and read 3356 times.

I once read a good discussion on this, might be here on a-net. IIRC red was deemed as the color that is easiest to notice. Same reason fire engines are usually red, btw.

Topic: RE: B757 Emergency Exit Sign Question
Username: tdscanuck
Posted 2012-11-20 05:53:31 and read 3356 times.

Quoting HAWK21M (Reply 16):
Whats the US justification for this...

At this point, same reason the US still uses feet/inches/pounds...because they've always done it that way. I have no idea why it started that way. But if you go into any US building the exit signs will almost universally be red; that's just what colour you expect to see for exits here.

The FARs as they currently stand required red for several portions of exit markings (e.g. the word "EXIT" on the door, the arrow showing which way the handle should turn to open the door) and that seems to be carried over into everything exit related.

Quoting HAWK21M (Reply 16):
Out here its Green.

That's true for most of the world, as far as I know.

Quoting Fabo (Reply 17):
I once read a good discussion on this, might be here on a-net.

Here are some good threads:
New Kind Of Exit Sign (by Lucce Sep 23 2011 in Tech Ops)
No Smoking/Fasten Seat Belt Signs On 787? (by 1337Delta764 Jul 30 2010 in Civil Aviation)

And here's a good slate article on the general red vs. green exit issue:
http://www.slate.com/articles/life/s..._word_vs_the_little_green_man.html

And here's the FAA Equivalent Level Of Safety finding for the green exit sign on the 787:
http://rgl.faa.gov/Regulatory_and_Gu...005c242a/$FILE/PS07-0585-CS-10.pdf

Tom.

[Edited 2012-11-20 05:58:32]


The messages in this discussion express the views of the author of the message, not necessarily the views of Airliners.net or any entity associated with Airliners.net.

Copyright © Lundgren Aerospace. All rights reserved.
http://www.airliners.net/