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Dani
6th Jun 2006, 03:45
Most of us have learned through the years that CRT (cathod ray tubes) - conventional screens in cockpits - shouldn't be turned off but dimmed. For enhanced life (or other reasons?).

Now with new aircraft arriving more and more with nice flat LCD screens, what do you do when you leave the flight deck?

Serious opinion and technical facts required.

Thanks guys,
Dani

LME (GOD)
6th Jun 2006, 08:30
CRT's were dimmed to prevent screen burn through. LCD's dont suffer from this problem buts its still good practice to dim the screens. I don't think you'll be able to turn them off, not on a Boeing anyway.

slender
6th Jun 2006, 08:58
Best example I can think of is lcd on your home radios. on most of the time and no performance degradation, far superior to crt.It should not make any difference if you switch them off or not

MrBernoulli
6th Jun 2006, 08:59
Why is it "still good practise to dim" an LCD?

Capt Claret
6th Jun 2006, 09:12
Dani

I was told the other day that having the LCDs set to about 2/3 brightness as opposed to full brightness, doubles their life. At 2/3 they're quite bright enough to see easily.

I do not know the source of the information.

mcdhu
6th Jun 2006, 09:13
We are told to dim them on leaving the FD and never switch them off (Ezy).
In the Fcom 3 under SOPs, one of the last items in 'Parking' is DUs....Dim'

Cheers,
mcdhu

Watchdog
6th Jun 2006, 09:44
and in my company's SOP's (A320's with LCDs) the leaving acft c/list is:

DU's.....OFF/DIM
(E/WD's have no 'off' position) :suspect:

computer jockey
6th Jun 2006, 09:54
As LME said, CRTs were dimmed to prevent screen burn-in. It was not recommended to turn off CRTs as continually switching them on and off stresses the high voltage circuits and could result in premature failure. Better to keep them running. This was true of most applications for CRTs, not just in cockpits.

LCDs are much more reliable and can be left on for as long as you like. I would guess that it is "good practice" to dim them when not used is either to save power by turning the backlight down, or avoiding the distraction of brightly glowing screens in an otherwise dark and empty flight deck.

---
cj

-I wish life had a "pause" button

Denzil
6th Jun 2006, 23:11
I believe on the Airbus aircraft there was a sofware issue that caused the displays to go into "self test" mode after a certain amount of hours powered up. This could make all displays useless for 20-30 seconds. This could be the reason that some operators turn the DU's off.

Loose rivets
7th Jun 2006, 04:17
I'm not sure of the methods used on the flight-deck, but to compare to modern T/Vs, the LCD component takes very little current, but the illuminating bulb is very much a ‘lifed' component.

The bulbs on a 50-60 inch screen used to cost $1,000, but now are around $350. One T/V shop in Essex does not leave the big Sonys on display because of the life of the bulb.

If there is a similarity in the method of displaying LCD information, it would be safe to assume that to under-run the back-light would give it more life.