A question about the safety briefing and the guide lights
 

During the safety briefing at the start of the flight, it's stated that in the event of an evacuation guide lights will illuminate on the floor. Why don't they actually illuminate them to show passengers?

in days gone by, they used to do that. nowadays they don't as they are run on an independent battery system and it runs the battery down


they need to make sure they will actually work if anything were to require their use

It used to be a good idea, since we did find bits u/s on occasions:eek:

Don't see the need to if I'm honest. Ryanair used to not sure if they did. It is pretty self explanatory - follow the lights to an exit. The safety card shows them quite nicely.Besides I can never see them from the window seat when they are being demonstrated. Never seen it done on an airbus - perhaps it is not possible. Been a long time since I looked at a forward attendant panel.

Actually - it is possible to do this using the hard keys on the FAP on the A32S I've just checked an old manual but it is not an SOP to do this at my airline and seemingly not on any over A32S operator I've flown with. It is a guarded switch and CC1 is at the front for the demo so technically they could but there must be reason for not. Personally I think it better to have one crew member at the front and rear of the cabin maintaining situational awareness during the demo and not fiddling with switches whilst there are two crew in the cabin doing a manual demo.

How would you rate the failure of the system or of one or more bulbs in the system in the MEL? It'd be a no go wouldn't it? Much better to ignore the troublesome thing. After all, in the event of an emergency evacuation the lights functioning is likely to be way down on anyone's list of memories to recall for the AIB inquiry?

No - MEL is quite clear on 'allowables'.

When they were first devised, they would have been filament lamps but now (MY GUESS) is that they are LEDs that illuminate a Fluorescent strip, so failure greatler reduced. (/MY GUESS)

Unless of course the cabin is full of thick, black, acrid smoke at the time (remember Manchester?) and escape path lighting would have been your only chance of finding an exit as you crawl with your nose pressed to the floor trying to find some air to breathe. :ugh:

Manchester would not occur today due to numerous factors including the widening of aisles at critical parts throughout the cabin and now luminescent strips are placed on top of the floor level lighting so it is still possible to find a oath to the exits if the worst were to happen. Cabin layout, design, materials and lighting now ensure that the fateful KT flight will not re-occur not to mention evacuations procedures are now one of the most common simulator exercises.

Uummm, 'Never say Never'. Humans have a way of repeating themselves ...

I thought the lights were replaced with charging reflective stripes thus they don't need to be turn on - they just shine when is dark.

Trend is toward photoluminescent strips to avoid reliance on power supplies and connectivity that have a high risk of degradation in an accident environment

and make savings on weight and maintenance costs

Ah, so with photo-luminescent strips they can't show them. Thanks.

The Dreamliner has LEDs every two rows built into the seats. They're not demonstrated because they're pretty obvious when they're on, you couldn't really miss them.

The MEL Question :
From the top of my head for my aircraft type:
floor path exit lights:
1) no two adjacent lights can be broken
2) the light next to the emergency exits MUST work

We used strips that stored energy during the daytime and glowed in the dark. i loved them, low maintenance. The downside was that on a long night flight there were time limitations and sometimes the cabin lights would be required on to ensure a charge. Emergency lighting is not very bright in the event of power loss and a dark and possibly smoky cabin the illumination is more than sufficient.

and the (important bit left out): ...and guide you to an exit.

But the bit that puzzles me is how exactly will they guide you to an exit. I must be stupid because all I think they will do is show you where the aisle is. So as you approach the lights, say on your hands and knees in darkness, in thick acrid smoke, your exit will be either to the left or the right. Errmm... And that's the bit left out.

Returning to the initial post, you will see them if you fly at night after the cabin lights are dimmed/turned off before departure/landing.

The cabin crew would have to call the cockpit to switch ON the emergency lights for your display demo.
The switch will have been selected to ARM and the emergency lights will come ON after a massive power failure..
Batteries are re-chargeable and should last 20-30 mintues so a quick demo will not kill the system.

MEL
 

Always a hard one so the lights normally have four lamps inside each light unit.
Is a light broken when one filament fails or when the total assy has failed??

Same again, four lamps will be fitted inside the light and lens will be amber or red in colour for the exit.

MEL
 

BOAC

This has in my experience caused more problems between Engineer and Pilot that the MEL on emergency lighting is not clear...