A/c train From United Kingdom, joined Jun 2001, 501 posts, RR: 4 Posted (12 years 1 month 2 weeks 1 day 2 hours ago) and read 1468 times:
Why are cabin lights dimmed on T/O, My lecturer reckons it's because the load on the IDG's is to much, I know about the CSD and the TRU's and stuff and I can't work it out, can someone with more experience saught this one out, ?
A/c train From United Kingdom, joined Jun 2001, 501 posts, RR: 4 Reply 2, posted (12 years 1 month 2 weeks 1 day 2 hours ago) and read 1397 times:
Your correct , my bro is an FA, he said that it helps vision in the event of an evacuation, but what did an Avionics Tech mean when he says theres to much load on the IDG's? the Tech being my lecturer.....
Metwrench From United States of America, joined Aug 2001, 750 posts, RR: 2 Reply 4, posted (12 years 1 month 2 weeks 21 hours ago) and read 1360 times:
I don't buy into the "too much load" theory. Even with all the switches that could possibly be turned on be actuated the electrical supply system shouldn’t be anywhere near capacity. Aside from that, any transport category A/C that I’ve been around that is less than 20 years old has automatic “load shedding” capabilities. Meaning that non-essential systems are deactivated automatically in the event that power needs exceed a predetermined percentage of capacity i.e. failure of a DC generator, etc. Cabin lighting is one of the non-essential systems.
Dc10hound From United States of America, joined Dec 2000, 463 posts, RR: 6 Reply 5, posted (12 years 1 month 2 weeks 20 hours ago) and read 1336 times:
Load Shed is a good thing.
The fluorescent lighting in the cabin are among the largest loads on the aircraft's generating system. Ovens and coffee makers take alot of current too (Not usually operating on TO). Next comes fuel boost pumps and electric hydraulic pumps.
Turning the lights off on TO lets the system monitor essential loads without having to look at the extra cabin bus load. Conditions that would cause Load Shed are probably recognized with in seconds or milli-seconds, but why take a chance on TO roll?
Each A/C operator probably has their own policy on this..
BTW, Metwrench, does "failure of a DC generator" mean failure of a Transformer Rectifier (TR)? I would think that would decrease the load on the AC generating sytem.
"Eagles soar. But weasels never get sucked into jet intakes.."
Musang From United Kingdom, joined Apr 2001, 797 posts, RR: 7 Reply 7, posted (12 years 1 month 2 weeks 10 hours ago) and read 1289 times:
I believe your lecturer is looking at it from a technical viewpoint - as a pilot I go with the pax evacuation theory, because (a) I'm not aware of any procedures to reduce electrical loads during t/o to protect the generators, (b) the gens. would be at high speed at t/o, i.e. most capable, whilst if they did need protecting, the low speed regime would be where it happened. (c) As you will know, eye adjustment to dark conditions takes several minutes. In an emergency, cabin lighting will go down automatically to emergency level as the generators go off line, and evac. will need to be completed in a couple of minutes or so.
Metwrench From United States of America, joined Aug 2001, 750 posts, RR: 2 Reply 8, posted (12 years 1 month 1 week 6 days 23 hours ago) and read 1248 times:
I was just supposing a primary source with a theoretical DC gen failure. With the abundant redundant (I rhymed, that’s cool) systems installed on modern A/C that really isn’t a cause for concern, or return (I did it again) to base.
Funny From Greece, joined May 2001, 333 posts, RR: 0 Reply 9, posted (12 years 1 month 1 week 6 days 14 hours ago) and read 1229 times:
The biggest reason is that if an emergency were to occur at takeoff, and the cabin lights were on, it would take time to adjust to a sudden black-out for the eyes.
Lights are dimmed to avoid this and save crucial time.
Flashmeister From United States of America, joined Apr 2000, 2892 posts, RR: 7 Reply 12, posted (12 years 1 month 1 week 6 days 6 hours ago) and read 1207 times:
I can remember when I was a kid flying - they'd only turn the lights off if it was dark outside. They had the cabin lights on all the time otherwise, on takeoff and landing.
Was there a regulation issued sometime to change that practice?
Also, I noticed on my last flights in mid-October that (on a DL 767 SLC-PDX) they turned on the 'sidewall' lights before landing to help with the FA's cabin checks, but they never turned them off. We landed with them on. Was that a violation of some procedure?
FBU 4EVER! From Norway, joined Jan 2001, 998 posts, RR: 7 Reply 13, posted (12 years 1 month 1 week 5 days 17 hours ago) and read 1186 times:
The practice of dimming the lights during night take-off and landings was introduced for emergency evac. reasons.It is also used to increase visibility of the floor-mounted emergency evacuation stripes in cabin smoke situations neccessitating an evacuation.
Andrewfung From , joined Dec 1969, posts, RR: Reply 14, posted (12 years 1 month 1 week 23 hours ago) and read 1135 times:
a couple of other things to consider:
1) in the event of aborted take off, the engines may not be at full thrust. thus the "ability" of the generators to handle the load is not static. while the systems are likely designed to handle the load, from a safety perspective one would want to minimise any risks.
2) FAs also need to be able to see outside the A/C in case of an emergency. An engine fire or other structural damage is easier spotted when the internal lights are dimmed. Think about how hard it is to see out a window at night when your room light is on - all you see is a reflection of inside your room, not what is outside.