DC10Heavy From United States of America, joined Aug 2004, 45 posts, RR: 0 Posted (9 years 8 months 1 week 1 day 19 hours ago) and read 5628 times:
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.
Fl1tpa From United States of America, joined May 2004, 258 posts, RR: 0
Reply 1, posted (9 years 8 months 1 week 1 day 17 hours ago) and read 5492 times:
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.
"Looks like I picked the wrong week to stop sniffin' glue."
KAUSpilot From United States of America, joined Jan 2002, 1963 posts, RR: 32
Reply 3, posted (9 years 8 months 1 week 1 day 17 hours ago) and read 5464 times:
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 From Denmark, joined Mar 2000, 6545 posts, RR: 54
Reply 4, posted (9 years 8 months 1 week 1 day 17 hours ago) and read 5401 times:
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.
Always keep your number of landings equal to your number of take-offs, Preben Norholm
TinPusher007 From United States of America, joined Feb 2005, 983 posts, RR: 1
Reply 8, posted (9 years 8 months 1 week 1 day 16 hours ago) and read 5374 times:
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 From United States of America, joined May 2004, 3623 posts, RR: 21
Reply 9, posted (9 years 8 months 1 week 1 day 16 hours ago) and read 5336 times:
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.
NW747-400 From United States of America, joined Jun 1999, 504 posts, RR: 0
Reply 10, posted (9 years 8 months 1 week 1 day 16 hours ago) and read 5313 times:
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 From , joined Dec 1969, posts, RR:
Reply 11, posted (9 years 8 months 1 week 1 day 16 hours ago) and read 5292 times:
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!).
DC10Heavy From United States of America, joined Aug 2004, 45 posts, RR: 0
Reply 13, posted (9 years 8 months 1 week 1 day 15 hours ago) and read 5215 times:
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.