DC10Heavy
Topic Author
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MD-88 Noise In The Cabin

Mon Apr 25, 2005 5:16 am

As soon as the roll in the MD-88 starts, why does the cabin sound like a vacuum starts up in reverse mode ? No other aircraft does this that I am aware of. Does it have something to do with the way the air circulation unit works on that type of a/c ? I was on DAL 943 ATL to SYR last night and soon as we powered up for the roll, it sounded like a Hoover. Great flight nonetheless. I love the climb rate of those MD-88's.

Any info would be appreciated.

Thanks.
Matthew.
NWA DC10 LAX to HNL the only way to go!
 
FL1TPA
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RE: MD-88 Noise In The Cabin

Mon Apr 25, 2005 7:18 am

I'm not sure what part of the cabin you're in when this noise becomes apparent, but in the aft cabin of the 717 (the most similar a/c I have experience with) the air conditioning packs are located in the space above the ceiling. When the pilots turn on those packs for heat or cooling, they produce a quite loud rushing air sound but not really a "vacuum in reverse" noise.

Could be something unique to the MD-80 series a/c.

FL1TPA
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N766UA
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RE: MD-88 Noise In The Cabin

Mon Apr 25, 2005 7:19 am

Probably something to do with the A/C packs. The ERJ, for example, makes a loud whining noise in the rear cabin.
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KAUSpilot
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RE: MD-88 Noise In The Cabin

Mon Apr 25, 2005 7:30 am

The ERJ's PACK's are located on the lower fuselage along the wing root. The loud whining noise in the rear of the cabin is most likely simply the engines.....high bypass turbofans make a buzzsaw sounding noise.

In the ERJ, when full power is applied at the beginning of the takeoff roll, the cabin is pressurized to .2 psi at a rate equivalent to descending at 450 ft per minute. A similair effect in the MD80 may account for the "reverse vacuum" noise you describe. Was the noise constant or temporary?
 
prebennorholm
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RE: MD-88 Noise In The Cabin

Mon Apr 25, 2005 8:06 am

Sounds strange. After maybe a hundred flights on MD-80 (mostly MD-82, MD-83 and MD-87 - never MD-88) and MD-90 I cannot recognize a Hoover sound.

On the other hand it is my experience that the MD-80/-90 is the quietest plane of them all, at least as long as you sit in the forward half of the cabin.

Sitting in between the engines, however, makes you count every minute until landing and makes you wonder why the hell you chose an MD operator to serve you. But that's no Hoover sound, it's a plain old P&W sound. Anyway not nearly as aggressive as its ancestor the DC-9.
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N766UA
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RE: MD-88 Noise In The Cabin

Mon Apr 25, 2005 8:08 am

Quoting KAUSpilot (Reply 3):
The loud whining noise in the rear of the cabin is most likely simply the engines.....high bypass turbofans make a buzzsaw sounding noise.

The noise I'm thinking about has something to do with the A/C. I asked an ERJ captain friend of mine about it once. The whining sound is totally independent of the engines.
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KAUSpilot
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RE: MD-88 Noise In The Cabin

Mon Apr 25, 2005 8:18 am

He could be talking about the Gasper Fan I guess, it's located toward the rear of the cabin.
 
Boeing73G
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RE: MD-88 Noise In The Cabin

Mon Apr 25, 2005 8:19 am

Quoting DC10Heavy (Thread starter):
As soon as the roll in the MD-88 starts, why does the cabin sound like a vacuum starts up in reverse mode ?

Must be pressure change. I have heard this happen as well on all of the AS MD-83 a/c I have flown on.
 
tinpusher007
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RE: MD-88 Noise In The Cabin

Mon Apr 25, 2005 8:19 am

If Im not mistaken, in most a/c when takeoff power is applied, the air conditioning (which is bleed air from the engines) is suppressed momemtarily so that they can produce the required power for takeoff. Maybe this is what you're noticing. Other than that, I think it might just be the sound of the engines themselves.
"Flying isn't inherently dangerous...but very unforgiving of carelessness, incapacity or neglect."
 
September11
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RE: MD-88 Noise In The Cabin

Mon Apr 25, 2005 8:40 am

Interesting thread. I love the feeling when M80s engines go up for take off. I can not hear the "noise" but I can feel the deep "whiring" vibration. It stops soon after plane is off ground. It's like engines "on high power".. it sure does feel different on other aircraft type but the M-80 is spectular to me, especially on take off.

[Edited 2005-04-25 01:43:22]
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NW747-400
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RE: MD-88 Noise In The Cabin

Mon Apr 25, 2005 8:53 am

I've never noticed this sound before, I have been on DL's MD88's dozens of times over the last few months. Usually the a/c blows harder as engine RPM increases, but it sounds more like a whooshing noise than a vacuum.

The buzzsaw sound of a high bypass turbofan wouldn't apply to the MD80, its JT8's have a bypass ratio of 2:1, making it low to medium bypass =)
 
UAL747
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RE: MD-88 Noise In The Cabin

Mon Apr 25, 2005 8:58 am

I know exactly what you are talking about.

It's almost like a woooooosh of air. Whenever I take off in an MD-80, I always liken it to taking off down the highway in a Lexus LS430. So quiet, all you hear is the wind rushing outside, (and that's extremely soft sounding as well!).

UAL
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KAUSpilot
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RE: MD-88 Noise In The Cabin

Mon Apr 25, 2005 9:37 am

Quoting NW747-400 (Reply 10):
its JT8's have a bypass ratio of 2:1, making it low to medium bypass =)

I'm aware, I was referring to the 2nd reply which made reference to the ERJ.
 
DC10Heavy
Topic Author
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RE: MD-88 Noise In The Cabin

Mon Apr 25, 2005 9:51 am

Wow, I did not know this thread would get so much play, I am glad it did, I initially described it as a Hoover in reverse, perhaps a bit much on the analogy, I could not think of a better term until I saw the " woooosh of air " post by UAL747, that is more closer to what I am talking about.

I think it must be the air cond or heating system getting that first push of air upon take off. The noise did seem to diminish as we climbed out.

Thank you to all that contributed to this matter.

Matthew A. Ware
NWA DC10 LAX to HNL the only way to go!

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