BR715-A1-30 From , joined Dec 1969, posts, RR: Posted (12 years 8 months 3 weeks 1 day 17 hours ago) and read 5961 times:
Hello All of you Technical people. How are you?
My question today is about the 717... Again.
I noticed when the pilot throttles up, There is a sound that sounds like Air Whooshing right through the overhead bins. The pilot will advance the throttles, and you will hear the engine accelerate, and at the same time you will hear the WHOOOOOSSSSSHHHHHHHH.
Also, I have noticed that while sitting at the gate, there is this whining sound that goes like "EEWMMPH" every 5-6 seconds. It sounds like it is coming from the Cargo area. Can anyone explain this?
747Forever From United States of America, joined Jun 2008, 0 posts, RR: 0
Reply 2, posted (12 years 8 months 3 weeks 8 hours ago) and read 5800 times:
yup, thats it, i noticed the same thing on the 747, on the descent, every so often the engines would spool up, and as they did there would be an increase in the wooshing sound of the air conditioning, obviously due to the packs getting more bleed air as the engines turn faster
AA737-823 From United States of America, joined Mar 2000, 6091 posts, RR: 12
Reply 3, posted (12 years 8 months 2 weeks 6 days 15 hours ago) and read 5742 times:
That sound is strange, and really worried me the first time I heard it. It is the hydraulics. You can hear it on any MD-80 or 717 flight, any airline. It's a grinding, moaning sound at first when they power up the hydraulics at the gate, then it goes to exactly as you describe it...
Cdfmxtech From United States of America, joined Jul 2000, 1341 posts, RR: 26
Reply 5, posted (12 years 8 months 2 weeks 6 days ago) and read 5704 times:
The MD80 hydraulic sound at the gate (using auxilairy hyd) is not like most aircraft. It is not a steady whine.
The sounds breaks unsteadily. It almost sounds like something is wrong, which was what I thought the very first time I worked the aircraft.
Atlamt From United States of America, joined Sep 2001, 241 posts, RR: 3
Reply 7, posted (12 years 8 months 2 weeks 5 days 2 hours ago) and read 5658 times:
The reason you hear the sound coming from the overhead bins is because of the layout of the air distribution ducts. The main line is running along the top of the cabin. This main duct starts just forward of the aft door and runs the length of the cabin stopping just short of the cockpit door. The main line through a series of ducts spaced every few feet feeds two smaller ducts, one on each side of the cabin just above the bottom of the overhead bins. These line provide air to the gasper vents above your head.
As mentioned before as the engines spool up more bleed air is sent to the packs which causes more air to be introduced into the system. This is what causes the sound of the air whooshing to increase and hopefully I explained why it comes from the overhead bins.
The link below is a picture of an MD88 during overhaul. The picture quality isn't the greatest but it will show you where everything is.