Aircraft lights

[Diedtrying]

Can someone please explain why during take off and landing the flight crew have to switch off the internal lights on the aircraft?

[BackPacker]

It's one of those measures that theoretically, under certain conditions, may or may not enhance safety. The idea behind it is that as a pax, your eyes are used to low light conditions, which may be beneficial in case of an emergency, when having to evacuate the aircraft in the dark.

[27mm]

Similar to that euphemistic statement during the safety brief, where they don the lifejacket and say "...in the event of landing on water...."

[the dean]

....and if there was smoke it would make the floor lighting to the exit easier to see...

[PAXboy]

The really amusing thing about this Diedtrying, is that ... the rules vary in various countries. This question is asked in here about once a year and the best answers tell you that in country A the internal lights must be dimmed for take off at night but if you land in country Z late on (also in darkness) then you have to keep the cabin lights on.

Doubtless, each country's Aviation Authority can justify it:

With the lights dimmed, the pax will be adjusted to darkness if they have to make a rapid exit.
With the lights on, the emergency services can put their ladders up and look in more easily to see what the situation is.When the emergency arrives, it will always be slightly different to the ones that were imagined/planned/rehearsed anyway.

[Flap Track 6]

Can someone please explain why during take off and landing the flight crew have to switch off the internal lights on the aircraft?

Aside from the 'night blindness' issue covered by other replies, there is also the issue of reducing the power offtake load on the engines in case of a go-around.

If our steely-eyed aviator is on finals when (s)he gets a late go-around call, TOGA power and a rapid spool up is the order of the day. As the lights are powered by the electrical generators running off the engines, you want to reduce the power offtake load so you don't get reduced engine performance.

Same for take-off.

[manintheback]

A few lightbulbs affecting an aircrafts power generator? Now I know nought about the aircrafts internals but that does seem a tad unlikely :confused:

[Bob Lenahan]

Yeh, especially on the DC-B 320. You know, the one with the 4 engines in the tail.

[419]

Not knowing too much about plank wing, is the APU running throughout the flight, (and therefore helping to feed the bus system) or is this only used when the aircraft is on the ground.

[Bob Lenahan]

Depends on the EPR/RPM (RAM ratio) being produced by the anti-magnetic egnausiator system.

[Diedtrying]

Cheers everyone. :ok:

[Bob Lenahan]

419,
Sorry, thought your were responding to my response, but now on second thought, maybe you weren't, so in normal ops the apu is only used on the ground to supply electrical power and air for cabin comfort and engine starting. Some a/c can use apu in the air if necessary, some can't.