Why is the 757 a/c so noisy?
Thread Starter
Join Date: Jan 2005
Location: Europe
Age: 63
Posts: 137
Likes: 0
Received 0 Likes
on
0 Posts
Why is the 757 a/c so noisy?
We have several 757´s and they are quite a mystery in many ways. I used to think that airliners were quality built and precisely. But the air-conditioning noises (in the cockpit) are driving me mad (and deaf). Why doesn’t Boeing take pride in the working environment of the pilots?
Also, the noise differs between aircraft. While some 757s may be tolerable other are just screaming loud, so loud that they can’t be flown with both packs on. Is this difference because of sloppy craftsmanship?
Are there any jet cockpits noisier than the 757?
Also, the noise differs between aircraft. While some 757s may be tolerable other are just screaming loud, so loud that they can’t be flown with both packs on. Is this difference because of sloppy craftsmanship?
Are there any jet cockpits noisier than the 757?
Join Date: Dec 2001
Location: Middle East
Posts: 413
Likes: 0
Received 0 Likes
on
0 Posts
http://aeromedical.org/Articles/NIHL.html
Noisiest cockpit research... scroll about halfway down. The 767 is the quietest, from what I can see...
Noisiest cockpit research... scroll about halfway down. The 767 is the quietest, from what I can see...
Join Date: Jan 2006
Location: US
Posts: 2,205
Likes: 0
Received 0 Likes
on
0 Posts
Try turning off the right recirc fan and then re-engaging it. The "OFF" light goes out but the duct noise typically decrease. In about 80% of the a/c it drops the air conditioning duct noise in half. Keep in mind it's not something to do on the ground, or right after takeoff. The additional air pressure only comes back after landing. I used to know, but can't remember, if switching electrical power or shutting an engine down reactivates the fan.
Run the cabin temp slightly cooler(71-72 F/22 C) prior to attempting.
I avoid this technique on full/short/sweaty/daytime/combinations thereof flights.
Unfortunately the loudest a/c often seem to be in the 20% were it doesn't decrease the duct noise.
Cockpit noise? Aircraft design (767/757 +++ ) helps. Next is reduction in KIAS. With fuel issues dictating .78-.79 crz and higher alts = lower KIAS (250-260 KIAS at altitude) the 757 cockpit, especially after R recirc fan cycling, is very quiet.
Run the cabin temp slightly cooler(71-72 F/22 C) prior to attempting.
I avoid this technique on full/short/sweaty/daytime/combinations thereof flights.
Unfortunately the loudest a/c often seem to be in the 20% were it doesn't decrease the duct noise.
Cockpit noise? Aircraft design (767/757 +++ ) helps. Next is reduction in KIAS. With fuel issues dictating .78-.79 crz and higher alts = lower KIAS (250-260 KIAS at altitude) the 757 cockpit, especially after R recirc fan cycling, is very quiet.
Join Date: Jul 2005
Location: OZ
Posts: 580
Likes: 0
Received 0 Likes
on
0 Posts
Noisey cockpits I can't speak for the 757 but the 767 suffers the following problem.
The cockpit aircon and equip cooling noise reaches an unbearable level due the buildup of debris, dust etc in the ducts that supply the air.
I have seen the buildup so bad that the internal diameter of the duct is almost reduced to half capacity (imagine an old gal water pipe with rust inside).
As we all know air at subsonic speed is incompressable therefore to get the same amont of air thru the aircon/equip cooling ducts it must move faster and therefore alot more air noise.
Therein lies how to fix this problem, most of the cockpit panels need to be removed as it would appear the cockpit is assembled after and around all ducting installation.
Which means some heavy ground time. A luxury no airline wants to afford.
The cockpit aircon and equip cooling noise reaches an unbearable level due the buildup of debris, dust etc in the ducts that supply the air.
I have seen the buildup so bad that the internal diameter of the duct is almost reduced to half capacity (imagine an old gal water pipe with rust inside).
As we all know air at subsonic speed is incompressable therefore to get the same amont of air thru the aircon/equip cooling ducts it must move faster and therefore alot more air noise.
Therein lies how to fix this problem, most of the cockpit panels need to be removed as it would appear the cockpit is assembled after and around all ducting installation.
Which means some heavy ground time. A luxury no airline wants to afford.
