AJRfromSYR
Topic Author
Posts: 439
Joined: Tue May 17, 2005 6:03 am

A350 - Cabin Pressure

Fri Dec 16, 2005 8:22 am

A lot of people keep saying the A350 will have equal or better cabin pressure then the 787. I don't know if either will be really noticeable but, when I prompt these people for supporting information I get nothing. Is there documentation I can read about this?
-AJR-
 
ikramerica
Posts: 13762
Joined: Mon May 23, 2005 9:33 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 8:50 am

Airbus did claim most recently that it will. I'm pretty sure it's on the website, and it is in their multi-page ads IIRC. Yet QF claimed the advantage still goes to the 787 in cabin comfort, so I wonder what they found out that Airbus is not advertising?
Of all the things to worry about... the Wookie has no pants.
 
AJRfromSYR
Topic Author
Posts: 439
Joined: Tue May 17, 2005 6:03 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 8:54 am

I've checked the website, nothing under the A350 passanger comfort section.
-AJR-
 
abba
Posts: 1380
Joined: Mon Jun 06, 2005 12:08 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 9:15 am

http://www.flug-revue.rotor.com/FRheft/FRHeft05/FRH0512/FR0512f.htm

It says:

Quoting Flug Revue:
Inside the A350 passenger cabin, which has been slightly enlarged due to the use of flattened ribs, Airbus plans to increase the air humidity to 20 percent, that is, five percent more than in the 787 which already has a particularly comfortable design. Again, the internal pressure will defy the Boeing model, with a typical pressure altitude of only 1,830m.

Abba
 
Ruscoe
Posts: 1577
Joined: Sun Aug 22, 1999 5:41 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 9:31 am

I posted a comment in another thread regarding this.

The reason the 787 could be given greater pressure is because carbonfibre is a lot more fatique resistent than Al.
The 350 can be pressurised to whatever altitude they want but it will result in higher maintenace requirements.

Similarly for the humidity. The Al fuselage will suffer more corrossion, and I have been told that the limiting factor for the 787 will be growth of fungi and microrganisms if the humidity is raised too high.(same applies to 350)

Ruscoe
 
NAV20
Posts: 8453
Joined: Thu Nov 27, 2003 3:25 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 9:40 am

Quoting Ruscoe (Reply 4):
The reason the 787 could be given greater pressure is because carbonfibre is a lot more fatique resistent than Al.
The 350 can be pressurised to whatever altitude they want but it will result in higher maintenace requirements.

Thanks Ruscoe, interesting point. But surely it'll be more that 'higher maintenance requirements'? Won't both aircraft require appropriate cyclic pressure-testing at the pre-certification stage? And wouldn't some re-design of the Airbus fuselage be required?

[Edited 2005-12-16 01:41:32]
"Once you have flown, you will walk the earth with your eyes turned skywards.." - Leonardo da Vinci
 
AJRfromSYR
Topic Author
Posts: 439
Joined: Tue May 17, 2005 6:03 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 9:53 am

Hmm, this is similar to Airbus saying

Quote:
You will be able to use your cell phone on the A350

They seem to be telling you what you can do, but if its feasible is a different story.
-AJR-
 
Ruscoe
Posts: 1577
Joined: Sun Aug 22, 1999 5:41 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 9:59 am

Yes Nav20 what you say is correct. The 350 fuselage would need to be stronger but that may be a relatively minor problem considering that they plan to use Al/Lithium, which is stronger pound for pound than the current Al alloys used.

Boeing are using the decreased maintenance requirements of a carbon fibre fuselage as a positive selling point. From what I have read, cycle for cycle the carbonfibre fuselage will require less maintenance.

Did you happen to see the Defense Industry stand at Avalon? Carbon composites are actually being used the other way also to repair Al structures. eg F111. It is the way of the future.

Ruscoe
 
BoomBoom
Posts: 2459
Joined: Fri Nov 04, 2005 2:26 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 10:02 am

Quoting Abba (Reply 3):
http://www.flug-revue.rotor.com/FRheft/FRHeft05/FRH0512/FR0512f.htm

It says:...

Quoting Flug Revue:

The question becomes is this Flug Revue article accurate or was this just John Leahy running at the mouth again?

If this claim doesn't even appear on Airbus' website, I would give it no credence.
Our eyes are open, our eyes are open--wide, wide, wide...
 
Ruscoe
Posts: 1577
Joined: Sun Aug 22, 1999 5:41 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 10:08 am

Quoting AJRfromSYR (Reply 6):
You will be able to use your cell phone on the A350

It amazes me that this could be seen as a + selling point. Can you imagine what it would be like in a craft with cell phones going off everwhere, and the odd loud and obnoxiuos person speaking rubbish at a very loud level.

Ruscoe
 
trex8
Posts: 4603
Joined: Sat Nov 02, 2002 9:04 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 10:14 am

Quoting BoomBoom (Reply 8):
The question becomes is this Flug Revue article accurate or was this just John Leahy running at the mouth again?

If this claim doesn't even appear on Airbus' website, I would give it no credence.

this was also in either Flight International or AWST as I read something similar and I don't ever read Flug Revue but you can't walk out of the office without tripping over a FI or AWST where I am!, Now they could all be getting it from each other or the same source. Just because its not in the Airbus website doesn't mean diddly.
 
abba
Posts: 1380
Joined: Mon Jun 06, 2005 12:08 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 10:17 am

Quoting BoomBoom (Reply 8):
The question becomes is this Flug Revue article accurate or was this just John Leahy running at the mouth again?

If this claim doesn't even appear on Airbus' website, I would give it no credence.

I expected this comment to come. No surprise it is from you. If you do not like what you see - then deny it.

Abba

(And by the way I have also read the information from Airbus but cannot remember where pt - and I am not going to waste my time finding it again just because you happen not to like what you read in a respected publication)
 
AJRfromSYR
Topic Author
Posts: 439
Joined: Tue May 17, 2005 6:03 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 10:22 am

Quoting Trex8 (Reply 10):
Just because its not in the Airbus website doesn't mean diddly.

OK, but now the question is at what cost?

Is this like either company saying their A350 or 787 can cruise at Mach .98? Sure it can cruise at that speed but at what cost to the wing and fuselage? Will the airline actually be able to have the pressure and humidity that these articles talk about or is it just Airbus saying it can be done - and leaving out "at the cost of x to the fuselage".
-AJR-
 
roseflyer
Posts: 9606
Joined: Fri Feb 13, 2004 9:34 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 10:30 am

Well I am quite familiar with the 787 environmental control system since Hamilton Sundstrand is responsible for it. It is a much more powerful and an electrical system. When you have an electrical system the pressure can really be whatever you want. I honestly don't know what amount the cabin will actually be pressurized to. I never knew that when I was working on the project. But I heard it was in the vicinity of 8,000 feet above MSL.

As far as I know, no one has been awarded the contract for teh Airbus environmental control system, since the plane isn't that far in the development stage compared to the 787. Nothing has been announced that I know of.
If you have never designed an airplane part before, let the real designers do the work!
 
NAV20
Posts: 8453
Joined: Thu Nov 27, 2003 3:25 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 10:33 am

Good point, AJR. I fancy it would cost fuel/performance as well. Boeing are going 'bleedless' with the 787, the A350 would presumably have to draw the extra power/air from the engines.
"Once you have flown, you will walk the earth with your eyes turned skywards.." - Leonardo da Vinci
 
zvezda
Posts: 8891
Joined: Sat Aug 28, 2004 8:48 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 10:45 am

Quoting NAV20 (Reply 14):
I fancy it would cost fuel/performance as well. Boeing are going 'bleedless' with the 787, the A350 would presumably have to draw the extra power/air from the engines.

Either way the power comes from the engines. In the B787 case, the additional electrical load on the generators (which are attached to the engines) puts a corresponding additional load on the engines. There is no free lunch.

However, as RoseFlyer points out, in the electrical case one can produce just as much pressure as is needed. In the bleed-air case, one produces as much pressure as might ever be needed and then discards the rest. So there is an efficiency advantage for the bleedless case, but I expect it's minor.
 
abba
Posts: 1380
Joined: Mon Jun 06, 2005 12:08 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 11:08 am

Quoting Zvezda (Reply 15):
Either way the power comes from the engines. In the B787 case, the additional electrical load on the generators (which are attached to the engines) puts a corresponding additional load on the engines. There is no free lunch.

"Nothing comes from nothing. Nothing ever did"

(including air)

Abba
 
ikramerica
Posts: 13762
Joined: Mon May 23, 2005 9:33 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 11:10 am

Well, the APU can be designed do it with the engines only serving backup, and the APU can be designed to be most efficient at a certain speed required to produce the electricity while the engines can be designed to be most efficient at the speed required for cruise.

Kind of like a hybrid engine vs. a conventional engine. the conventional is designed to be most fuel efficient at cruise at lower RPMs but provide the most power at high RPMs, while the hybrid is designed to be most efficient with the engine OFF or at high rpms generating a lot of power to charge the batteries, then turn OFF. (At least that's how the most efficient hybrids are designed, though some of the recent ones are "hybridized" conventional setups that are used to boost efficiency but not to the same degree.)

If the APU is designed to run all the generators and the engines are allowed to just provide locomotion, you may get an efficiency savings. It would allow for a lighter, smaller engine for the same task. I assume this is their plan, but I don't know, so I'll ask.

Is the design for the APU on the 787 one that is meant to power all the systems of the aircraft under normal conditions, or is it only for use when the engines aren't running or as a backup?
Of all the things to worry about... the Wookie has no pants.
 
474218
Posts: 4510
Joined: Mon Oct 10, 2005 12:27 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 11:18 am

Quoting Zvezda (Reply 15):
However, as RoseFlyer points out, in the electrical case one can produce just as much pressure as is needed. In the bleed-air case, one produces as much pressure as might ever be needed and then discards the rest. So there is an efficiency advantage for the bleedless case, but I expect it's minor.

On the "old system" where engine bleed air was used to pressurize the cabin, "all the pressure that might ever be needed" was also available, if it wasn't then there would be no need for outflow valves.
 
roseflyer
Posts: 9606
Joined: Fri Feb 13, 2004 9:34 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 11:20 am

Quoting Ikramerica (Reply 17):
If the APU is designed to run all the generators and the engines are allowed to just provide locomotion, you may get an efficiency savings. It would allow for a lighter, smaller engine for the same task. I assume this is their plan, but I don't know, so I'll ask.

Is the design for the APU on the 787 one that is meant to power all the systems of the aircraft under normal conditions, or is it only for use when the engines aren't running or as a backup?

The APU is not designed to power electrical systems in flight. I worked on the testing of the 787 electrical generators that are being mounted in the engines. The 787 is basically making everything electrical. The generators on the 787 are the most powerful generators ever on an airplane by far. They produce somewhere in the vicinity of a gigawatt of electrical power. These are the most efficient generators ever produced and are far more powerful and efficient than those on previous jets.

Electricity will be used to power the environmental control system that will pressurize the cabin and keep everything in order for the passengers. I assume that the A350 will operate in a similar way, but I don't know of any finalized designs since I haven't done any work on that project and as far as I know contracts for systems have not been awarded yet.

[Edited 2005-12-16 03:26:36]
If you have never designed an airplane part before, let the real designers do the work!
 
BoomBoom
Posts: 2459
Joined: Fri Nov 04, 2005 2:26 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 2:06 pm

Quoting Trex8 (Reply 10):
Just because its not in the Airbus website doesn't mean diddly.

Just because it's in a magazine, doesn't mean diddly.
Our eyes are open, our eyes are open--wide, wide, wide...
 
McGoose
Posts: 35
Joined: Thu Aug 05, 2004 2:37 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 2:15 pm

Quoting Ruscoe (Reply 4):

Similarly for the humidity. The Al fuselage will suffer more corrossion, and I have been told that the limiting factor for the 787 will be growth of fungi and microrganisms if the humidity is raised too high.(same applies to 350)

Air Mauritius will install a humidification system in their A340s next year. It will probably be possible to use the same system for the A350 and the B787.
 
BoomBoom
Posts: 2459
Joined: Fri Nov 04, 2005 2:26 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 2:23 pm

Quoting Abba (Reply 11):
(And by the way I have also read the information from Airbus but cannot remember where pt - and I am not going to waste my time finding it again just because you happen not to like what you read in a respected publication)

I'm sure this respected publication is just reporting what Leahy said; there's nothing wrong with that. It's just that we all know Leahy has 'credibility problems'--kind of like you, Abba.
Our eyes are open, our eyes are open--wide, wide, wide...
 
abba
Posts: 1380
Joined: Mon Jun 06, 2005 12:08 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 3:32 pm

Quoting BoomBoom (Reply 22):
I'm sure this respected publication is just reporting what Leahy said; there's nothing wrong with that. It's just that we all know Leahy has 'credibility problems'--kind of like you, Abba.

Could you please explain why it should become more credible by being written on the Airbus homepage?

Abba
 
AJRfromSYR
Topic Author
Posts: 439
Joined: Tue May 17, 2005 6:03 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 3:53 pm

Quoting Abba (Reply 23):
Could you please explain why it should become more credible by being written on the Airbus homepage?

They would be more held to it, this could of just been Leahy talking as he tends to do. If its on their site it makes it more firm.
-AJR-
 
abba
Posts: 1380
Joined: Mon Jun 06, 2005 12:08 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 4:55 pm

Quoting AJRfromSYR (Reply 24):

They would be more held to it, this could of just been Leahy talking as he tends to do. If its on their site it makes it more firm.

Leahy sure does indeed have a BIG mouth (and some of members of the Boeing fan club get rather upset about it - I find it typical American and as such a part what makes Americans so very charming). But to say that he is without credibility is approaching plain nonsense. Leahy is - no matter what - an important part of what allowed Airbus to become a significant player in its industry. He has sold more airplanes than many a car dealers has sold cars. Come on! He can't neither be stupid nor lack credibility completely. If you really believe that then you (in particular if you also include the senior management of Airbus in the description as some of the more active members of the fan club does) have an even bigger issue to explain: why has Airbus been so successful. And that will ridiculous indeed!

BoomBoom only makes a fool of himself writing as he does.

Abba
 
PlaneDane
Posts: 347
Joined: Wed Feb 09, 2005 3:08 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 5:02 pm

Quoting Abba (Reply 23):
Quoting BoomBoom (Reply 22):
I'm sure this respected publication is just reporting what Leahy said; there's nothing wrong with that. It's just that we all know Leahy has 'credibility problems'--kind of like you, Abba.

Could you please explain why it should become more credible by being written on the Airbus homepage?

Abba

It would be a more credible claim because then Airbus would actually be promoting it as a genuine feature of the A350. As for now, we don't have this.

To me, it is rather simple logic, really.
 
AJRfromSYR
Topic Author
Posts: 439
Joined: Tue May 17, 2005 6:03 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 5:32 pm

Quoting PlaneDane (Reply 26):
It would be a more credible claim because then Airbus would actually be promoting it as a genuine feature of the A350. As for now, we don't have this.

To me, it is rather simple logic, really.

Exactly what I've been thinking.

Abbi, would Enders be just as important to Airbus as Leahy if not more? And didn't he run his mouth about having sum 164 firm orders? Does being in upper management mean your creditable? So where are all these firm orders?
-AJR-
 
User avatar
garpd
Posts: 2308
Joined: Thu Aug 11, 2005 9:29 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 5:41 pm

I struggle to see how Airbus can raise the Cabin pressure and Humidity to levels equal or beyond those planned on the 787. Reason being that the 787 has an inherently stronger construction that will easily take the increased pressure. Its carbon fibre construction will. as already mentioned, resist corrosion to a higher level that a conventional metal frame & skin aircraft. This is essentially what the A350 will be! Regardless how much spin Airbus put on it, the A350 will still largely be of metal construction. And unless they strengthen it by increasing structural strength and or perhaps skin thickness (thereby making the thing a damn sight heavier!), I cannot see the 350 benefiting from the higher cabin pressure loads.

This can only be Leahy spin.

Tis simple logic.
arpdesign.wordpress.com
 
AJRfromSYR
Topic Author
Posts: 439
Joined: Tue May 17, 2005 6:03 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 5:48 pm

Quoting GARPD (Reply 28):

The spin is, the plane can be at any humidity and pressure you want, how long the fuselage lasts is a different question. But the simple fact is, you can have rain forest conditions in there for at least a couple flights.
-AJR-
 
abba
Posts: 1380
Joined: Mon Jun 06, 2005 12:08 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 5:53 pm

Quoting PlaneDane (Reply 26):
It would be a more credible claim because then Airbus would actually be promoting it as a genuine feature of the A350. As for now, we don't have this.

Do you really believe that airlines base their purchase decisions on what they read in the press or on Airbus' webpage (or Boeing's for that matter)? Come on. Nothing of this is "real" in that sense. Consider it more like a service to the public and as a very indirect way of promoting themselves in the broader public (even if I am sure that people at Airbus and Boeing know as well as you and me that most ordinary people have no clue as to what they are flying). If you were to buy an aircraft you give A and B a phone call and you would have their representatives at your door with the material that really matter.

Abba
 
abba
Posts: 1380
Joined: Mon Jun 06, 2005 12:08 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 6:11 pm

Quoting AJRfromSYR (Reply 29):
The spin is, the plane can be at any humidity and pressure you want, how long the fuselage lasts is a different question. But the simple fact is, you can have rain forest conditions in there for at least a couple flights.

Isn't most of the upper fuselage of the 350 made of composits - from about the floor up?

Abba
 
AJRfromSYR
Topic Author
Posts: 439
Joined: Tue May 17, 2005 6:03 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 6:57 pm

Quoting Abba (Reply 31):
Isn't most of the upper fuselage of the 350 made of composits - from about the floor up?

Not according to Airbus...
-AJR-
 
User avatar
garpd
Posts: 2308
Joined: Thu Aug 11, 2005 9:29 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 7:23 pm

Quoting AJRfromSYR (Reply 29):
The spin is, the plane can be at any humidity and pressure you want, how long the fuselage lasts is a different question. But the simple fact is, you can have rain forest conditions in there for at least a couple flights.

Very true.
arpdesign.wordpress.com
 
Joni
Posts: 2613
Joined: Thu Aug 10, 2000 11:05 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 7:26 pm

Quoting BoomBoom (Reply 8):
The question becomes is this Flug Revue article accurate or was this just John Leahy running at the mouth again?

What? Someone asked for a source, and when one was provided it was dismissed. If John Leahy says the pressure will be X, then would you seriously doubt that?

Quoting AJRfromSYR (Reply 12):
Will the airline actually be able to have the pressure and humidity that these articles talk about or is it just Airbus saying it can be done - and leaving out "at the cost of x to the fuselage".

Why not ask the same of Boeing?

Interestingly, there's also this quote on bleed vs. bleedless: (same source)

“We believe it is better to use bleed air than to generate power separately. That would require liquid-cooled heat exchangers, which would raise the maintenance costs by 40 percent in return for only a 1.5 percent reduction in fuel consumption.”

Quoting GARPD (Reply 28):
I struggle to see how Airbus can raise the Cabin pressure and Humidity to levels equal or beyond those planned on the 787. Reason being that the 787 has an inherently stronger construction that will easily take the increased pressure. Its carbon fibre construction will. as already mentioned, resist corrosion to a higher level that a conventional metal frame & skin aircraft.

Your struggles are appreciated. However, the issues really aren't that complex and not dissimilar to what Boeing has to do with the 787. The strength of the fuselage is a design parameter that can be specified - and a composite fuselage is not necessarily stronger or weaker than an aluminum-built fuselage, for the same weight. Similarly the interior surface of the fuselage, and various fittings, can be designed to accomodate a given humidity level.

Do you have a source for your claim that the "787 has an inherently stronger construction"? Why would that be, is is aerodynamically less efficient and thus require a stronger "construction"?

Boeing itself has stated that:

generally accepted assumptions that composites would weigh significantly less and cost significantly more than aluminum were found to be not universally true.

http://www.jobwerx.com//news/Archive...rials_advances_news_id_102703.html

Curiously, Airbus seems to disagree with Boeing on the maintenance costs of metal vs. composite structures, and overall the composites vs. metals debate has been turned 180 degrees - now Boeing is using more composites and Airbus metals, whereas historically this has been the other way around. The A340 was even derisorily called "superplastic" at some point.
 
User avatar
garpd
Posts: 2308
Joined: Thu Aug 11, 2005 9:29 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 7:38 pm

Quoting Joni (Reply 34):
What? Someone asked for a source, and when one was provided it was dismissed. If John Leahy says the pressure will be X, then would you seriously doubt that?

Err.... Yes!

Quoting Joni (Reply 34):
Do you have a source for your claim that the "787 has an inherently stronger construction"? Why would that be, is is aerodynamically less efficient and thus require a stronger "construction"?

The CarboFibre fuselage construction is designed to be much stronger. This is the main reason the 787 can achieve a higher cabin pressure. For sources, checkout the endless discussions on these forums and the countless sources they link to.

Quoting Joni (Reply 34):
Curiously, Airbus seems to disagree with Boeing on the maintenance costs of metal vs. composite structures, and overall the composites vs. metals debate has been turned 180 degrees - now Boeing is using more composites and Airbus metals

Well, airbus are hardly going to say "Yes, Boeing are on the right track" are they?
arpdesign.wordpress.com
 
Stealthz
Posts: 5546
Joined: Wed Feb 02, 2005 11:43 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 7:47 pm

Quoting RoseFlyer (Reply 19):
gigawatt of electrical power.

I don't think so.. do you have any grasp of how much power that actually is!!
something like 746,000 HP.
I read somewhere that a Trent (can't quote the version)turbine used in a marine or power station installation produces something like 70,000 HP, it would then require 10+ of those to generate the electrical power you claim with none left over for propelling the aircraft.

Need to get a grip on these decimal points!!!

C
If your camera sends text messages, that could explain why your photos are rubbish!
 
Joni
Posts: 2613
Joined: Thu Aug 10, 2000 11:05 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 7:49 pm

Quoting GARPD (Reply 35):
The CarboFibre fuselage construction is designed to be much stronger. This is the main reason the 787 can achieve a higher cabin pressure. For sources, checkout the endless discussions on these forums and the countless sources they link to.

If it's stronger, then it's going to weigh more and burn more fuel. And according to the quote given, the A350 will have higher cabin pressure than 787.
 
User avatar
garpd
Posts: 2308
Joined: Thu Aug 11, 2005 9:29 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 7:52 pm

Quoting Joni (Reply 37):
If it's stronger, then it's going to weigh more and burn more fuel. And according to the quote given, the A350 will have higher cabin pressure than 787.

Ah, therein lies the flaw of your logic. Composites can be stronger than metals while being lighter. This the whole point of Boeing using composites for the 787 fuselage. It will be lighter than any other aircraft of its size.

The A350 may well eventualy have a higher cabin pressure, but at what cost? That is going to seriously reduce the life expectancy of its large metal fuselage.
arpdesign.wordpress.com
 
Joni
Posts: 2613
Joined: Thu Aug 10, 2000 11:05 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 7:55 pm

Quoting GARPD (Reply 38):
Ah, therein lies the flaw of your logic. Composites can be stronger than metals while being lighter. This the whole point of Boeing using composites for the 787 fuselage. It will be lighter than any other aircraft of its size.

Composites can be stronger for given weight than metals, but the opposite can also be true - as stated by Boeing's VP I quoted in Reply #34.
 
User avatar
garpd
Posts: 2308
Joined: Thu Aug 11, 2005 9:29 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 8:14 pm

Quoting Joni (Reply 39):
Composites can be stronger for given weight than metals, but the opposite can also be true - as stated by Boeing's VP I quoted in Reply #34.

To a certain extant only.
arpdesign.wordpress.com
 
eilennaei
Posts: 1003
Joined: Tue Nov 23, 2004 8:41 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 8:15 pm

It is customary and to use the term "(cabin) pressure differential", which is the diffrerence between the cabin overpressure and the outside underpressure that varies with the altitude. This differential value will be set at the design stage, and the maximum value will never be exceeded, not even for a short period "at the expense of the maintenance costs", as some seem to have understood the matter.

Also I'd like to point out that there's no such single fantastically strong and enduring material as "the composite(s)". They should rather be understood as a generic technique to create various structures, "strong" AND "weak" according to very precise specifications. The ability to tailor the material's behaviour accurately is the key point, but it all comes with a hefty price tag in the design and manufacturing stages.
 
AJRfromSYR
Topic Author
Posts: 439
Joined: Tue May 17, 2005 6:03 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 8:36 pm

Quoting Joni (Reply 34):
Why not ask the same of Boeing?

Boeing is honest about its limits, and have said that fungi will be a problem at higher levels.

Airbus has not outlined its limits, and the only thing they give us is unconfirmed by anyone but Leahy. You would think if Leahy was so confident in telling a reporter, he would put it on his own website.

Like I say, Leahy is just saying its possible, nothing about if its feasible.

"The 787 can do mach 3"
-AJR-
 
eilennaei
Posts: 1003
Joined: Tue Nov 23, 2004 8:41 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 9:16 pm

Quoting Ruscoe (Reply 4):
Similarly for the humidity. The Al fuselage will suffer more corrossion, and I have been told that the limiting factor for the 787 will be growth of fungi and microrganisms if the humidity is raised too high.(same applies to 350)

I'm afraid the greatest provider of microorganisms into the cabin air are the passengers themselves.

Some actual measurements on air pollutants in the cabin, a very extensive study:

http://www.dft.gov.uk/stellent/group...s/page/dft_aviation_503475-10.hcsp

http://www.dft.gov.uk/stellent/group...ments/page/dft_aviation_027562.pdf
 
Joni
Posts: 2613
Joined: Thu Aug 10, 2000 11:05 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 9:20 pm

Quoting GARPD (Reply 40):
To a certain extant only.

True, both ways.
 
NAV20
Posts: 8453
Joined: Thu Nov 27, 2003 3:25 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 9:21 pm

Ever since the Comet 1 it has been known that cycles of pressurisation/depressurisation can cause fatigue in aircraft structures. As a result, pressurised areas such as the fuselage have to be subjected to exhaustive tests (the Comet 4 fuselage was tested through 120,000 pressure reversals, the equivalent of 480,000 flying hours).

For Boeing, that will have meant that a lot of the time they have already spent designing the 787 will have been taken up with making sure that the mainly-composite fuselage will stand up to repeated pressurisation cycles through the full 'design life' of the aircraft, and then some.

For Airbus it means that, unless the conventional A300 fuselage was 'over-designed' to a ridiculous extent in the first place (which is highly unlikely), a complete redesign and a similar exhaustive testing programme will be required before they too can offer increased cabin pressures.
"Once you have flown, you will walk the earth with your eyes turned skywards.." - Leonardo da Vinci
 
roseflyer
Posts: 9606
Joined: Fri Feb 13, 2004 9:34 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 9:52 pm

Quoting StealthZ (Reply 36):
Quoting RoseFlyer (Reply 19):
gigawatt of electrical power.

I don't think so.. do you have any grasp of how much power that actually is!!
something like 746,000 HP.
I read somewhere that a Trent (can't quote the version)turbine used in a marine or power station installation produces something like 70,000 HP, it would then require 10+ of those to generate the electrical power you claim with none left over for propelling the aircraft.

Need to get a grip on these decimal points!!!

Sorry Roseflyer needed a little more sleep. 1500 horsepower = 1100000 watts
not 1 gigawatt. I always discussed it in terms of horsepower. In an overspeed (200% power) condition those generators can take in up to around 1500HP from the engine although normal operations are somewhere in the vicinity of below 500HP. It has been a while since I looked at that torque curve.

[Edited 2005-12-16 13:59:34]

[Edited 2005-12-16 14:06:27]
If you have never designed an airplane part before, let the real designers do the work!
 
Joni
Posts: 2613
Joined: Thu Aug 10, 2000 11:05 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 10:31 pm

Quoting NAV20 (Reply 45):
For Boeing, that will have meant that a lot of the time they have already spent designing the 787 will have been taken up with making sure that the mainly-composite fuselage will stand up to repeated pressurisation cycles through the full 'design life' of the aircraft, and then some.

For Airbus it means that, unless the conventional A300 fuselage was 'over-designed' to a ridiculous extent in the first place (which is highly unlikely), a complete redesign and a similar exhaustive testing programme will be required before they too can offer increased cabin pressures.

This would be necessary in any case since the fuselage of the A350 is dis-identical to A330 and is built from different materials.
 
AJRfromSYR
Topic Author
Posts: 439
Joined: Tue May 17, 2005 6:03 am

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 10:50 pm

Quoting Joni (Reply 47):
This would be necessary in any case since the fuselage of the A350 is dis-identical to A330 and is built from different materials.

So Leahy's comments are more of a goal then a fact?
-AJR-
 
Joni
Posts: 2613
Joined: Thu Aug 10, 2000 11:05 pm

RE: A350 - Cabin Pressure

Fri Dec 16, 2005 11:03 pm

Quoting AJRfromSYR (Reply 48):
So Leahy's comments are more of a goal then a fact?

In the same way that Boeing's goal of increasing the cabin pressure is a "goal and not a fact". In other words, the testing hasn't been done but the design is set. We don't factually know that a 787 won't burst at the intended pressure since no complete fuselages have been built yet. However, the materials for both planes have been largely chosen and the qualities of the materials are known in detail, so it's quite unlikely either plane will not handle the respective target pressure.

Who is online

Users browsing this forum: 747m8te, A330freak, A330NZ, Alexa [Bot], dn280tls, Google Adsense [Bot], HELyes, hkcanadaexpat, IslandRob, Menzenski, mmo, nabla, NWOrientDC10, pacman3, rokklagid, SFOJFK, Zaf and 240 guests