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Unusual Noise During Takeoff In A330  
User currently offlineRyfly777 From United States of America, joined Aug 2005, 10 posts, RR: 0
Posted (9 years 1 month 2 weeks 6 days 21 hours ago) and read 3242 times:

During a normal t/o in a A330, i hear somthing that sounds like rocks rolling down the plane when taking off in the ceiling. Every A330 i've been on does that sound. I hear this sound when i fly in China on Cathay Pacific, Singapore, etc. Does anyone know what it is?

15 replies: All unread, jump to last
 
User currently offlineZarniwoop From United Kingdom, joined Apr 2005, 265 posts, RR: 0
Reply 1, posted (9 years 1 month 2 weeks 6 days 18 hours ago) and read 3225 times:

Hi Ryfly777.
I also noticed a similar noise on a CX 330 from SIN to HKG on both the outward and return legs. I noticed it more just before landing, sounded like the ceiling creaking.


User currently offlineBuckFifty From Canada, joined Oct 2001, 1316 posts, RR: 19
Reply 2, posted (9 years 1 month 2 weeks 6 days 18 hours ago) and read 3221 times:

It's probably the overhead luggage lockers creaking, or the contents inside.

User currently offlineJkw777 From , joined Dec 1969, posts, RR:
Reply 3, posted (9 years 1 month 2 weeks 6 days 13 hours ago) and read 3173 times:

I have also experienced this on Thomas Cook's A332. I'm pretty certain it's something to do with the overhead lockers moving. You think it's bad on the A330, try the A340!

Cheers,
Justin  Smile


User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 4, posted (9 years 1 month 2 weeks 6 days 12 hours ago) and read 3163 times:

If it sounds like very small rocks rolling it is probably ice crystals in the air conditioning ducts.

Going to takeoff power provides much more airflow for the packs and the temp may go below that commanded. I've seen other types do this, and even blow snow out of the cockpit air vents.

It will usually sort it out rather quickly, especially once you go back to climb power.

That's my guess, not having been on board your flight.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineVzlet From United States of America, joined Mar 2004, 839 posts, RR: 0
Reply 5, posted (9 years 1 month 2 weeks 6 days 11 hours ago) and read 3145 times:

Quoting SlamClick (Reply 4):
If it sounds like very small rocks rolling it is probably ice crystals in the air conditioning ducts.

Insightful as usual, SlamClick. It's probably only the second time I've seen that term used in a technical explanation.



"That's so stupid! If they're so secret, why are they out where everyone can see them?" - my kid
User currently offlineHAWK21M From India, joined Jan 2001, 31712 posts, RR: 56
Reply 6, posted (9 years 1 month 2 weeks 6 days 10 hours ago) and read 3130 times:

Quoting SlamClick (Reply 4):
If it sounds like very small rocks rolling it is probably ice crystals in the air conditioning ducts.

Won't the Water seperator take care of it.
I'd vouch for Airflow thru the distribution ducts when T/O power is used.
regds
MEL



Think of the brighter side!
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 7, posted (9 years 1 month 2 weeks 6 days 9 hours ago) and read 3104 times:

Quoting HAWK21M (Reply 6):
Won't the Water seperator take care of it.

I don't know the answer to that. I can't imagine any kind of water separator that would be 100% It may be that the ice forms downstream from this component. I just don't know. I have seen it happen on a number of different types though.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3708 posts, RR: 34
Reply 8, posted (9 years 1 month 2 weeks 6 days 6 hours ago) and read 3047 times:
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Quoting Ryfly777 (Thread starter):
i hear somthing that sounds like rocks rolling down the plane when taking off in the ceiling.

Why do you sit in the ceiling for T.O.?


User currently offlineCCA From Hong Kong, joined Oct 2002, 846 posts, RR: 14
Reply 9, posted (9 years 1 month 2 weeks 6 days 4 hours ago) and read 3004 times:

It's ICE that formed in the airconditioning ducts due due high humidity.


C152 G115 TB10 CAP10 SR-22 Be76 PA-34 NDN-1T C500 A330-300 A340-300 -600 B747-200F -200SF -400 -400F -400BCF -400ERF -8F
User currently offlineHAWK21M From India, joined Jan 2001, 31712 posts, RR: 56
Reply 10, posted (9 years 1 month 2 weeks 5 days 10 hours ago) and read 2905 times:

Quoting SlamClick (Reply 7):
don't know the answer to that. I can't imagine any kind of water separator that would be 100% It may be that the ice forms downstream from this component. I just don't know. I have seen it happen on a number of different types though.



Quoting CCA (Reply 9):
It's ICE that formed in the airconditioning ducts due due high humidity

Post the Water Seperator Isn't that a bit difficult.Im referring to Commercial Aircraft only In case there are Exception.

regds
MEL



Think of the brighter side!
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 11, posted (9 years 1 month 2 weeks 5 days 10 hours ago) and read 2905 times:

There is a common mistake people make in thinking about water and this might help to understand this.

We all know water has three form: Liquid (water) Solid (ice) and vapor - steam, right?

Wrong. Steam is liquid. Free steam in the air is tiny droplets of superheated liquid water suspended in the atmosphere. Water vapor is a gas and thus, is not visible to the eye at all -except as a reduction to atmospheric visibility on days of high humidity. For example, where I live, on a clear day I can see a mountain range about fifty miles away as if it was just across the valley. Anywhere on the eastern seaboard of the US that mountain range would not be visible at all except on maybe one or two extraordinarily dry days a year.

Water separators will take out the liquid droplets and the ice crystals but it will not take out the water vapor. If conditions still exist downstream from the water separators where the water vapor will freeze, it will form ice crystals. I don't know if this is what was happening on the takeoff in question but I'll say it again. It is common at high power settings for the cockpit vents to be blowing snow.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineHAWK21M From India, joined Jan 2001, 31712 posts, RR: 56
Reply 12, posted (9 years 1 month 2 weeks 4 days 16 hours ago) and read 2821 times:

Quoting SlamClick (Reply 11):
If conditions still exist downstream from the water separators where the water vapor will freeze, it will form ice crystals

What equipment/Circumstanses would cause that to occur.

Quoting SlamClick (Reply 11):
Water separators will take out the liquid droplets and the ice crystals but it will not take out the water vapor

Vapour would have some filteration requirements vis-a-vis dry air.

What would the Temperature regulation circuit be doing in this case.

regds
MEL



Think of the brighter side!
User currently offlineCCA From Hong Kong, joined Oct 2002, 846 posts, RR: 14
Reply 13, posted (9 years 1 month 2 weeks 4 days 13 hours ago) and read 2801 times:

Sorry I should have explained, the humid air is from open doors on the AC at the gate, not from the AC packs. This humid air gets mixed with the aircon pack air which is in the order of 2-3 degrees C which forms condensation which gets into the ducts and eventually forms frost, you can tell it's going to happen when you walk on the AC and you can see moisture forming from the mixing of relatively warm humid air with the as SlamClick said very cold pack air. I've only ever noticed it during the humid months in Hong Kong and Australia.


C152 G115 TB10 CAP10 SR-22 Be76 PA-34 NDN-1T C500 A330-300 A340-300 -600 B747-200F -200SF -400 -400F -400BCF -400ERF -8F
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 14, posted (9 years 1 month 2 weeks 4 days 11 hours ago) and read 2777 times:

Quoting HAWK21M (Reply 12):
Vapour would have some filteration requirements vis-a-vis dry air.

It is a gas!

To separate one gas from another takes mechanical sophistication more at home in a laboratory than in an airplane. Water separators, coalescer bags etc. just take the big drops or ice crystals out. They are really pretty coarse.

Furthermore they don't want to take out ALL the moisture from the air. People already dehydrate badly on long flights. Most of the moisture in the cabin comes from other passengers exhaling!

What "conditions?" Temperature, dewpoint, water content.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineHAWK21M From India, joined Jan 2001, 31712 posts, RR: 56
Reply 15, posted (9 years 1 month 2 weeks 3 days 18 hours ago) and read 2702 times:

Quoting SlamClick (Reply 14):
People already dehydrate badly on long flights. Most of the moisture in the cabin comes from other passengers exhaling!

So Moisture to an extend is good.
regds
MEL



Think of the brighter side!
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