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777222LR
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787 Clicking Sound - Startup

Sat May 02, 2015 12:34 pm

Hey All! Just did my very first trip on a Boeing 787-8! Phenomenal aircraft. We did IAH-LHR-IAH on United. The IAH-LHR sector was on a new build 787 of United. Once the first engine was started, there was all of this clicking sounds that happened. On the return sector, we flew on United's first 787 and I didn't hear this. Can anyone explain?

Thanks!
 
Okie
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RE: 787 Clicking Sound - Startup

Sat May 02, 2015 3:30 pm

I am guessing you were sitting in a different seat on different sectors.

There are several electrical panels with contactors within the aircraft that switch the source of the electrical loads between Ground/APU/Engine.
I would make a wild guess the clicking sound was the contactors closing and opening when switching the electrical load to or from the generator/starter for the engine or disconnect from ground power.

I will point you to the ZA002 panel fire that was claimed to have been caused by FOD early in the test program there was several topics related to that incident.

Okie
 
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777222LR
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RE: 787 Clicking Sound - Startup

Sun May 03, 2015 2:02 am

Actually, was only one row difference in seating on both flights. I tried to listen for it on the return flight, didn't notice it at all. It was very loud on the IAH-LHR flight on the newer bird.
 
Okie
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RE: 787 Clicking Sound - Startup

Sun May 03, 2015 3:49 am

Quoting 777222LR (Reply 2):
Actually, was only one row difference in seating on both flights. I tried to listen for it on the return flight, didn't notice it at all. It was very loud on the IAH-LHR flight on the newer bird.

We still do not know if one flight the engine start was by ground equipment and the other the apu.
I still suspect you heard contactors shifting loads to or from one source to another, the contactors have to be pretty large for the amperage they have to switch.


Okie
 
cobra27
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RE: 787 Clicking Sound - Startup

Thu Jun 04, 2015 2:59 pm

Could it be spark (ignito) plugs?
 
OMP777X
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RE: 787 Clicking Sound - Startup

Thu Jun 04, 2015 3:16 pm

Quoting Okie (Reply 3):
I still suspect you heard contactors shifting loads to or from one source to another, the contactors have to be pretty large for the amperage they have to switch.

I believe that your completely right, only I've always thought of the sound that contactors make while shifting loads as loud hard popping sound, not a click like I'd get out of putting on a seatbelt. Especially if the loads are very heavy, then they can be very loud! I'm not playing a game of semantics here either, I just don't feel like "clicking" is the appropriate word for it. It doesn't give the sound enough credit, IMHO.

Best,

OMP777X
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roseflyer
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RE: 787 Clicking Sound - Startup

Fri Jun 05, 2015 4:30 pm

Were you seated right over the wing? The electronics bay where all the high powered electrical panels is in that area.

There is also a clanky clunky noise that you will hear from the engines sometimes as they spin in the breeze.
If you have never designed an airplane part before, let the real designers do the work!
 
sharles
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RE: 787 Clicking Sound - Startup

Sat Jun 06, 2015 8:32 pm

Quoting OMP777X (Reply 5):
only I've always thought of the sound that contactors make while shifting loads as loud hard popping sound, not a click like I'd get out of putting on a seatbelt

Both of these descriptions correspond to sounds that I've heard from contactors.
Depends at the very least on the strength of the current, on whether it is AC or DC, and on the contactor itself.
 
OMP777X
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RE: 787 Clicking Sound - Startup

Sun Jun 07, 2015 12:18 am

Quoting sharles (Reply 7):
Depends at the very least on the strength of the current, on whether it is AC or DC, and on the contactor itself.
Quoting OMP777X (Reply 5):
Especially if the loads are very heavy

I addressed that above^.

Even the lightest loads on contactors in my mind "pop", not "click", but maybe I'm used to working around equipment that transfers larger amounts of current (A/C or D/C) than you are? To me, a click is the sound a socket wrench makes as you tighten something, or a rachet will click as you strap something down. You'd have to be near some seriously Mickey Mouse sized contactors to have me hear a click come from them IMHO.
"Happy Flighting!"
 
sharles
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RE: 787 Clicking Sound - Startup

Sun Jun 07, 2015 12:40 pm

Quoting OMP777X (Reply 8):
Even the lightest loads on contactors in my mind "pop", not "click", but maybe I'm used to working around equipment that transfers larger amounts of current (A/C or D/C) than you are? To me, a click is the sound a socket wrench makes as you tighten something, or a rachet will click as you strap something down.

Contactors in an electric vehicle (tram & trolleybus) is what I'm used to hearing.
The ones I come in contact with have some contactors that need the ability to break 1000V 1000A DC, but usually deal with 600V 0A DC. So they really are quiet as a mouse most of the time – the only sound is the purely mechanical click. But they pop when they have to break the arc at 700V 500A.
 
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777222LR
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RE: 787 Clicking Sound - Startup

Wed Jul 15, 2015 1:06 pm

Yes, was seated right over the aft portion of the wing. It happened once the engines were started up. It was a popping/clicking sound. Maybe 3-4 pops in succession. I have never heard that on any other aircraft, and being that this was my first time on a 787, I was being hyper vigilant of what I heard and saw. The funny thing is, I didn't notice this on the return LHR-IAH flight. The outbound IAH-LHR flight was on a newer 787, the return leg was on United's first 787.

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