Analog From United States of America, joined Jul 2006, 1900 posts, RR: 1 Posted (7 years 2 months 4 days 6 hours ago) and read 3626 times:
Last week I was on a CO 735 that had the most awful, seizure-inducing flickering cabin light. One of the bulbs was going bad (I assume). The flicker stopped when we pulled away from the gate. Why is this?
I assume that the flicker stopped when the aircraft stopped using ground power. Is this because ground power is at 60Hz and power generated on board is 400Hz? Or is it related to voltage (ground power or APU vs. generators on the engines)?
This wasn't the first CO 73x that had this problem. The previous one (733) flickered at the front of the F cabin where the FAs work. I can't believe that the FAs can live with this. If I were an FA I'd make damn sure to bitch and moan until these things were fixed. Sorry, I would bring this to the attention of the appropriate persons in an effort to resolve this maintenance issue.
Tdscanuck From Canada, joined Jan 2006, 12710 posts, RR: 80
Reply 1, posted (7 years 2 months 4 days 6 hours ago) and read 3616 times:
Quoting Analog (Thread starter): Last week I was on a CO 735 that had the most awful, seizure-inducing flickering cabin light. One of the bulbs was going bad (I assume). The flicker stopped when we pulled away from the gate. Why is this?
It sounds like a bad ballast in lamp (I'm assuming it was a fluorescent). Could be that ground power was just flaky enough to throw it off but aircraft power was OK.
Quoting Analog (Thread starter): Is this because ground power is at 60Hz and power generated on board is 400Hz?
Ground power is 400 Hz too (plus or minus some tolerance).
Bartonsayswhat From Canada, joined Oct 2007, 438 posts, RR: 0
Reply 2, posted (7 years 2 months 4 days 5 hours ago) and read 3600 times:
yeah ground power constantly fluctuates, be it from bridge power or a diesel GPU. APU power is much more consistant, which is why most of the fmc updating is done on the APU, as a power surge can wipe out the whole thing, or so i've been informed. also does anyone know, just as a plane arrives or leaves the gate, when it is switched from GEN/APU to GPU the lights flick once?
DALMD88 From United States of America, joined Jul 2000, 2695 posts, RR: 14
Reply 5, posted (7 years 2 months 3 days 20 hours ago) and read 3491 times:
Even relatively new ground power units can cause all sorts of strange happenings. Here in BOS our new terminal has new units at every gate. We frequently get calls in the morning about systems not testing correctly. The standard answer is switch to apu power and run the test again. If it is still a problem call back and will send someone out. I think the 737NG tends to have the most issues with flakey ground power.