747400sp
Topic Author
Posts: 3833
Joined: Sat Aug 09, 2003 7:27 pm

Why Don't Anybody Build Airliners Out Of Steel?

Sat Dec 09, 2006 12:19 pm

I know this sound like a stupid question, but why nobody builds airliners out of steal? The 2707 and L-2000 both was design to be build out of stainless steal. If Boeing or Airbus start using steal instead of plastic or aluminum, they may have stonrger plane thats could take a collusion or hard landing, also they could last longer. MCI and Prevost build there buses using steal. Now an airliner is supposed to have a stronger structure than a bus, so it dose not make since to keep build these aluminum and plastic airliner. I do not care if it will burn more gas, a steal airliner is safer than the one we have today, and Boeing and Airbus should try it.

That's my opinion, and please tell me with grace?  Smile
 
MD11FR8Jock
Posts: 8
Joined: Wed Nov 08, 2006 4:45 am

Why Don't Anybody Build Airliners Out Of Steel?

Sat Dec 09, 2006 12:41 pm

One word, WEIGHT!! Even though there are lots of merits for the strength, the weight difference would make most A/C unable to fly or so heavy that they would not be able to carry any pax or cargo. Even today Boeing and AB are beginning to use substantial amounts of composites that are in many cases just as strong as some types of steel yet weigh less than alum. On a side note both MCI and Prevost superstructers of their coaches are made of Aluminum (Got this from my brother that owns a charter company and runs both types of coaches) I hope this sheds some light on a very admirable idea.
 
EMBQA
Posts: 7795
Joined: Sat Oct 25, 2003 3:52 am

Why Don't Anybody Build Airliners Out Of Steel?

Sat Dec 09, 2006 12:44 pm

Quoting MD11FR8Jock (Reply 1):
One word, WEIGHT!!

Second word.... CORROSION....!!!
"It's not the size of the dog in the fight, but the size of the fight in the dog"
 
lincoln
Posts: 3133
Joined: Mon Nov 01, 2004 11:22 pm

Why Don't Anybody Build Airliners Out Of Steel?

Sat Dec 09, 2006 12:45 pm

Ok... I'm not an engineer, but my dad is in Management for one of aviation's leading fabricated metal suppliers (and he's 2500 miles away, so fat lot of good that does for this thread)...

I think it all comes down to weight, resilliance, and how easy it is to work with

Aviation grade aluminum is a very light metal, and relatively easy to tool, and is plenty strong.

I'm not sure about the weight or structural integrety of stainless (and it depends on the "class" of that stainless, but from what I understand it is a major pain in the ass to machine-- special tools, special techniques, etc. which would likely be cost prohibitive and difficult to service.

Hell, I have my eye on a $1400 "entertainment console". The only difference I can tell between it and the $300 version is the one I want has welded stainless (and marginally different styling).

You mention that you aren't concerned if it burns a little more gas since it would be "safer". I would counter that there hasn't been an accident in recent memory* where a change from aluminum to any other material would have any appreciable impact on the survivability, not to mention that the odds of such a situation occurring are so slim the "cure is worse than the disease", so to speak.

If two planes are going to run into each other (or terrain) at full tilt, regardless of what the birds are made out of, it will NOT BE A GOOD THING--aluminum vs. aluminum, aluminum vs. steel. etc.... The sheer forces involved virtually gaurntee this (two objects coming from opposite directions at 400 miles per hour hitting would be a 800 mile per hour speed delta).

Lincoln
* - The two potential I can think of: The early British jet model had squared window openings, resulting in metal fatigue at the corners and failure, and the Aloha 737-200 that "peeled open"... I don't know that any other material would have had better performance characteristics in either of these cases.
CO Is My Airline of Choice || Baggage Claim is an airline's last chance to disappoint a customer || Next flts in profile
 
2H4
Posts: 7960
Joined: Tue Oct 19, 2004 11:11 pm

Why Don't Anybody Build Airliners Out Of Steel?

Sat Dec 09, 2006 12:51 pm



To my knowledge, only two aircraft ever utilized steel as their primary airframe material:

The Budd RB-1 Conestoga:






...And the Fleetwings Seabird amphibian:





2H4


Intentionally Left Blank
 
Fly2HMO
Posts: 7207
Joined: Sat Jan 24, 2004 12:14 pm

Why Don't Anybody Build Airliners Out Of Steel?

Sat Dec 09, 2006 12:52 pm

Quoting 747400sp (Thread starter):
they may have stonrger plane thats could take a collusion or hard landing,

Strength doesn't necessarily equal safety. If you look at the car's made back in the 50's, they'd always survive almost intact after a crash because they were massive and very robustly built. But yet, in the inside, the passengers would be tossed around as rag dolls against the sides of the cars. Today's cars might seem flimsy in comparison, but they are safer because the cars frame and body panels are designed to take absorb energy on impact, therefore minimizing the energy transfer to the occupants inside.

And even then, composites are even stronger than steel, and are lighter than aluminum in most cases. The only real benefit I would see is that steel is reltively cheap and easy to work on.
 
OPNLguy
Posts: 11191
Joined: Tue Jun 15, 1999 11:29 am

Why Don't Anybody Build Airliners Out Of Steel?

Sat Dec 09, 2006 12:53 pm

Quoting 747400sp (Thread starter):
I know this sound like a stupid question, but why nobody builds airliners out of steal?

Because it's a felony?  Wink
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
kl671
Posts: 122
Joined: Sat Jul 09, 2005 10:00 am

Why Don't Anybody Build Airliners Out Of Steel?

Sat Dec 09, 2006 1:05 pm

First of all the metal is called steel.

The overiding reason steel is not used extensively for an aircraft's structure is weight. An all steel airliner would simply be too heavy.
 
User avatar
HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

Why Don't Anybody Build Airliners Out Of Steel?

Sat Dec 09, 2006 6:12 pm

Quoting 747400sp (Thread starter):
but why nobody builds airliners out of steal

Its reffered to as STEEL.
The reason for not using steel is Weight.You don't want things that fly to be heavy,as it'll require you to burn & carry more Fuel to carry that excess weight.Not Economical.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
MD11Engineer
Posts: 13916
Joined: Sun Oct 26, 2003 5:25 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Sat Dec 09, 2006 8:48 pm

Quoting 2H4 (Reply 4):
To my knowledge, only two aircraft ever utilized steel as their primary airframe material:

You forgot the very first all metal aircraft built by Hugo Junkers back during 1915, the Junkers J1. Since back then aluminium was a strategic metal, he had to try out his folly using steel (Who would build an aircraft out of something as heavy as metal instead of wood and fabric?).
He also pionered the cantilevered "thick wing", giving it space on the inside for a strong spar, which did not need external bracing wire to hold it straight.
After he proved the concept, he got access to aluminium and build his later aircraft out of this metal

Jan
Je Suis Charlie et je suis Ahmet aussi
 
2H4
Posts: 7960
Joined: Tue Oct 19, 2004 11:11 pm

RE: Why Don't Anybody Build Airliners Out Of Steel?

Sat Dec 09, 2006 10:09 pm




Quoting MD11Engineer (Reply 9):

Interesting piece of history there. Thanks, Jan.  Smile


2H4


Intentionally Left Blank
 
Blackbird
Posts: 3384
Joined: Wed Oct 06, 1999 10:48 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Sun Dec 10, 2006 1:06 am

It's too heavy predominantly.
 
474218
Posts: 4510
Joined: Mon Oct 10, 2005 12:27 pm

RE: Why Don't Anybody Build Airliners Out Of Steel?

Sun Dec 10, 2006 1:25 am

Many thousands of aircraft were built from steel, examples:

View Large View Medium
Click here for bigger photo!

Photo © Jean-Pierre Bonin



View Large View Medium
Click here for bigger photo!

Photo © Stephen Lane


Mild steel tubing was used to fabricate the frame of the fuselage, wings and empennage. It was then covered with fabric.
 
User avatar
lightsaber
Crew
Posts: 11744
Joined: Wed Jan 19, 2005 10:55 pm

RE: Why Don't Anybody Build Airliners Out Of Steel

Sun Dec 10, 2006 2:53 am

Quoting 747400sp (Thread starter):
I do not care if it will burn more gas,

Every added kg in an aircraft that doesn't ad value drops its purchase value by $500. Yes, that's the added cost, in a commercial airliner, of the weight.

Weight is break wear and tear.
Weight is range. You're saying build a plane with ~60% of the range of a competitor because you'll feel safer? Ugh... you won't be safer. At 200kts, its doesn't matter what material a plane is made from if you crash.

Since traveling by plane is already the safest way to travel, its not safety. Besides, carbon fiber/carbon-carbon planes will be able to take the dings and hits that cause so much concern with an Aluminum plane.

Quoting FLY2HMO (Reply 5):

And even then, composites are even stronger than steel, and are lighter than aluminum in most cases. The only real benefit I would see is that steel is reltively cheap and easy to work on.

 checkmark  There is only two areas in a plane where steel makes sense. The first is the landing gear (nothing takes shock loads better than steel). The second is in the engine (there are cases were the lightest way to make a component is steel).

Otherwise, for strength you need "moment of inertia" in an aircraft frame. In other words, volume of material. Due to how thin everything must be, shape must be used to prevent buckling, not material strength as much. That is one reason why the composites are the future of airliners.

Heck, they are even starting to make cars out of aluminum to save gas/improve performance. This of an airplane as a bus version of a ferrari.

Just to put it in perspective, a steel plane would cost about $5k more per flight than an aluminum plane. Would you really pay $100/ticket more just to have a plane out of a material you like than no aerospace engineer would want to touch? If we wanted to work with steel we would have become civil engineers. You do know the difference between civil engineers and aerospace engineers? Civil engineers make the targets.  duck   Wink


Lightsaber
"They did not know it was impossible, so they did it!" - Mark Twain
 
User avatar
Scooter01
Posts: 1183
Joined: Tue Nov 28, 2006 11:06 pm

RE: Why Don't Anybody Build Airliners Out Of Steel?

Sun Dec 10, 2006 4:09 am

What about being magnetic? What would happen in case of a lightning strike?
There is always a good reason to watch airplanes
 
SlamClick
Posts: 9576
Joined: Sun Nov 23, 2003 7:09 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Sun Dec 10, 2006 4:59 am

Why don't we skip one layer of unnecessary complexity and simply build the passengers out of steel. Then we could build airplanes out of eggcrate because it wouldn't matter! I think a 747 made of eggcrate, filled with steel passengers (who would obviously need less clothing/luggage) would weigh less than the standard model.
Happiness is not seeing another trite Ste. Maarten photo all week long.
 
flametech21
Posts: 46
Joined: Mon Sep 18, 2006 9:08 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Sun Dec 10, 2006 5:04 am

Weight, Corrosion, other factors make it uneconomical.

Airliners have many steel parts inside of them, just not on the fuselage skin. As an aerospace engineer you would just choose the right material for the job. Many different materials make up an aircraft including aluminum, steel, carbon-fibre, plexiglass, titanium, and many others.

Steel might be "strong", but we're talking about 50 ton turbine powered monsters that somehow have to get airborne. I have a better chance of getting killed in a car wreck on the neighboring I-635 then crashing in a plane on the runway. Besides, in a wreck aluminum has compressibility properties that absorb much of the impact. And carbon-fiber is lighter, stronger, and just as safe as it shatters, making the aircraft's structure take the brunt force of the impact, but saving the passengers inside from being crushed, like in aluminum.

My point is that steel is just to damned heavy for fuselage skin. If steel were light enough to fly, then the M1 would be an airplane, not a tank.

Lightning strikes are a non-issue, the fuselage skin is either connected to or is itself an electrical ground. Lightning passes right through it on it's journey to the ground, leaving the aerostructure relatively unharmed.  airplane 
They build them to a higher standard at Long Beach!
 
User avatar
Scooter01
Posts: 1183
Joined: Tue Nov 28, 2006 11:06 pm

RE: Why Don't Anybody Build Airliners Out Of Steel?

Sun Dec 10, 2006 5:18 am

Quoting Flametech21 (Reply 16):
Lightning strikes are a non-issue, the fuselage skin is either connected to or is itself an electrical ground. Lightning passes right through it on it's journey to the ground, leaving the aerostructure relatively unharmed

..and right through sensitive electonics and people touching any STEEL parts??
There is always a good reason to watch airplanes
 
saintsman
Posts: 2037
Joined: Fri Mar 15, 2002 12:34 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Sun Dec 10, 2006 5:36 am

Aluminium will conduct electricity as well as steel

Lightning strikes are a non issue.
 
User avatar
Starlionblue
Posts: 17058
Joined: Fri Feb 27, 2004 9:54 pm

RE: Why Don't Anybody Build Airliners Out Of Steel?

Sun Dec 10, 2006 6:08 am

Quoting SlamClick (Reply 15):
Why don't we skip one layer of unnecessary complexity and simply build the passengers out of steel. Then we could build airplanes out of eggcrate because it wouldn't matter! I think a 747 made of eggcrate, filled with steel passengers (who would obviously need less clothing/luggage) would weigh less than the standard model.

Man I'd love to see those eggcrate turbines. Big grin
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
lehpron
Posts: 6846
Joined: Tue Jul 10, 2001 3:42 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Sun Dec 10, 2006 7:21 am

Steel on average (as there are many variants of the stuff) is about 3 times heavier than Auminum based materials. If structural weight goes up, either fuel or payload goes down without having to redesign the engines.
Quoting 747400sp (Thread starter):
I do not care if it will burn more gas

You won't have to, you'll have either less payload or less range because the damn thing is heavy.
Quoting 747400sp (Thread starter):
but why nobody builds airliners out of steal? The 2707 and L-2000 both was design to be build out of stainless steal.

Those were meant for supersonic flight. When an object goes past sound, air compresses so much that the temperatures and pressures rise like crazy. Concorde was made of aluminum and went to Mach 2, if faster then aluminum woud melt, hence the use of steels and titanium based alloys. Yes they would have been heavier and it would cut down their range, but they are not and should not be compared with regular airliners.
Quoting 747400sp (Thread starter):
If Boeing or Airbus start using steal instead of plastic or aluminum, they may have stonrger plane thats could take a collusion or hard landing,

Airplanes are not designed to crash, they are designed to fly. Air crashes don't happen that often, the newsmedia brightens this aspect a bit, giving the impression of unsafe flying. They are not like cars that have airbags to protect people from thier own stupidity or by those that are stupid. Pilots have years of training before they are certified to carry people.

Quoting 747400sp (Thread starter):
a steal airliner is safer than the one we have today

What is your confidence in the idea of 'steel airliners' based on?

[Edited 2006-12-09 23:23:34]
The meaning of life is curiosity; we were put on this planet to explore opportunities.
 
CosmicCruiser
Posts: 2049
Joined: Tue Feb 22, 2005 3:01 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Sun Dec 10, 2006 9:55 am

Quoting 747400sp (Thread starter):
stonrger

stronger

Quoting 747400sp (Thread starter):
collusion

collision

Quoting 747400sp (Thread starter):
steal.

steel

Quoting 747400sp (Thread starter):
dose not

does not

Quoting 747400sp (Thread starter):
since

sense

Quoting 747400sp (Thread starter):
keep build

keep building

Quoting 747400sp (Thread starter):
Why Don't Anybody

Why doesn't anyone
 
AirframeAS
Posts: 9811
Joined: Thu Feb 05, 2004 3:56 pm

RE: Why Don't Anybody Build Airliners Out Of Steel?

Sun Dec 10, 2006 10:06 am

Quoting CosmicCruiser (Reply 21):

Cut the dude some slack, I think he is hearing impaired/deaf like I am...so his english skills are not top notch like hearing people's skills are...

American Sign Language and the english language is not the same.
A Safe Flight Begins With Quality Maintenance On The Ground.
 
fr8mech
Posts: 6601
Joined: Mon Sep 26, 2005 9:00 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Sun Dec 10, 2006 10:22 am

Quoting Flametech21 (Reply 16):
Lightning strikes are a non-issue, the fuselage skin is either connected to or is itself an electrical ground. Lightning passes right through it on it's journey to the ground, leaving the aerostructure relatively unharmed.

Apparently you have never seen the results of a lightning strike on an aircraft. Sometimes little damage, sometimes major damage. Certainly not a non-event.
When seconds count...the police are minutes away.
 
User avatar
Starlionblue
Posts: 17058
Joined: Fri Feb 27, 2004 9:54 pm

RE: Why Don't Anybody Build Airliners Out Of Steel?

Sun Dec 10, 2006 10:47 am

One important point here, and it was covered a bunch of replies back but I would like to repeat it, is that it doesn't matter what you build the plane out of with regard to collisions. Two objects colliding at airliner speeds are going to suffer major damage no matter what they are made of.

"If the black box can resist a fall from 30000 feet, why don't they build the whole plane out of black box material?"
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
SlamClick
Posts: 9576
Joined: Sun Nov 23, 2003 7:09 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Sun Dec 10, 2006 10:54 am

Quoting Starlionblue (Reply 24):
Two objects colliding at airliner speeds are going to suffer major damage no matter what they are made of.

Even if the airplanes were not damaged the passengers would end up as a homogeneous layer of miscellaneous protein matter at the forward end of the tube.

Somewhere out there is a video of the crash at Indianapolis that killed Bill Vukovich (1956?) in which you see a basically intact Indy roadster tumbling down the back straight. Contrast that with today's carbon-fiber, composite material race cars that seeminly explode into a million pieces leaving the driver unhurt.

Safety in a less than perfect world is about protecting the important bits (like people) and in a more perfect world it is more about not crashing.
Happiness is not seeing another trite Ste. Maarten photo all week long.
 
flametech21
Posts: 46
Joined: Mon Sep 18, 2006 9:08 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Sun Dec 10, 2006 11:24 am

Quoting Fr8Mech (Reply 23):
Apparently you have never seen the results of a lightning strike on an aircraft. Sometimes little damage, sometimes major damage. Certainly not a non-event.

Let me rephrase that. From a pilot's standpoint it is a non-event. I realize that it can cause various degrees of structural damage, almost always leaving an entrance and exit mark. Yes, that's a mx headache. My point was it is not a serious emergency that puts the passengers in imminent danger, like an uncontained engine failure, total hydraulic failure, etc.

I have never been struck by lightning while flying, however I have seen the results many times before. Being an engineer I am one of the first ones that sees the results of various aviation mishaps. I can tell you that in my 4 years at the airline, every plane we have had that was struck by lightning was able to continue on to its regularly scheduled destination.
They build them to a higher standard at Long Beach!
 
747400sp
Topic Author
Posts: 3833
Joined: Sat Aug 09, 2003 7:27 pm

RE: Why Don't Anybody Build Airliners Out Of Steel?

Mon Dec 11, 2006 1:07 am

Quoting MD11FR8Jock (Reply 1):
On a side note both MCI and Prevost superstructers of their coaches are made of Aluminum (Got this from my brother that owns a charter company and runs both types of coaches) I hope this sheds some light on a very admirable idea.

The MCI D 4500 is Cor-Ten steel from the floor up and the G 4500 frame is all stainless steel.

I got this from, WWW.Busmag.Com/PDF/MCIG4500.pdf, look in G4500 Detail. I think we both are right they have a steel frame but aluminum skin.
 
kaddyuk
Posts: 3697
Joined: Thu Nov 08, 2001 1:04 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Mon Dec 11, 2006 8:15 am

Quoting Starlionblue (Reply 24):
"If the black box can resist a fall from 30000 feet, why don't they build the whole plane out of black box material?"

Because then the only people who could touch it would be Avionic engineers and only GOD knows what sort of Mayhem would Pursue!
Whoever said "laughter is the best medicine" never had Gonorrhea
 
User avatar
HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: Why Don't Anybody Build Airliners Out Of Steel?

Mon Dec 11, 2006 2:38 pm

Quoting Kaddyuk (Reply 28):
Because then the only people who could touch it would be Avionic engineers and only GOD knows what sort of Mayhem would Pursue!

 biggrin 
So its the same out there too.I thought it only occured out here.

On the topic....Efforts are being made to make Aircraft more lighter & strong enough as needed.In the future hopefully some lighter Material will be Manufactured.

regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
xv408
Posts: 52
Joined: Sat Nov 25, 2006 1:24 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Mon Dec 11, 2006 9:59 pm

The design problems often faced by engineers is stiffness and fatigue life rather than absolute strength. Hence aluminium being used in preference to steel, being a lower density, and the trend to carbon composites, whose specific stiffness (Youngs modulus/density) is much higher than steel, aluminium, titanium etc.

Quoting Lehpron (Reply 20):
Concorde was made of aluminum and went to Mach 2, if faster then aluminum woud melt

Aluminium doesn't melt at these temperatures, but the strength of any metal falls with increasing temperature, and will start to creep beyond a certain point. Mach 2 temperatures (c.120deg C) are around the limit for aluminium.

Quoting Lightsaber (Reply 13):
The second is in the engine (there are cases were the lightest way to make a component is steel).

As air compressed in the engine, it gets hotter. For the same reason as above the early stages of an engine are aluminium, then steel and nickel at the back end for high compression ratios and turbines. To get high strength and creep resistance at high temperatures is very difficult and is one of the reasons turbine components are so expensive - the alloy is more expensive than silver and a pig to machine.
 
747400sp
Topic Author
Posts: 3833
Joined: Sat Aug 09, 2003 7:27 pm

RE: Why Don't Anybody Build Airliners Out Of Steel?

Tue Dec 12, 2006 8:51 am

Take in mind that the XB-70 and B-58 Hustler was made with a honeycomb stainless steel structure.
 
lehpron
Posts: 6846
Joined: Tue Jul 10, 2001 3:42 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Tue Dec 12, 2006 4:25 pm

Quoting Xv408 (Reply 30):
Quoting Lehpron (Reply 20):
Concorde was made of aluminum and went to Mach 2, if faster then aluminum woud melt

Aluminium doesn't melt at these temperatures

What temperatures?  Wink I just said faster, while that could be anything from Mach 2 to infinity, aluminmin melts around 1200F and those temperatures do not occur until about M4 (unless the body is blunt), but like you said, melt fatigue occurs much earlier. Even SR-71/A-12 use Titanium and it melts at 3300F.

Until composites can be made to be used at these temperatures, I won't trust them beyond proven alloys. Ceramics maybe.
The meaning of life is curiosity; we were put on this planet to explore opportunities.
 
User avatar
HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: Why Don't Anybody Build Airliners Out Of Steel?

Tue Dec 12, 2006 5:46 pm

Quoting Lehpron (Reply 32):
Until composites can be made to be used at these temperatures

Whats the Progress with Composites,Temperature resistant wise.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
xv408
Posts: 52
Joined: Sat Nov 25, 2006 1:24 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Wed Dec 13, 2006 2:01 am

Quoting Lehpron (Reply 32):
What temperatures?

At Mach 2, the peak temperature is around 120 deg C. At mach 3, it is around 340 deg C. Aluminium's creep properties start to degrade at around 140 deg C (but it is not a cliff edge). I can't find a direct link as the data is proprietary and VERY expensive to generate to a quality suitable for aircraft design, but this page gives some hints.
http://www.key-to-nonferrous.com/default.aspx?ID=CheckArticle&NM=153
Suffice to say that roughly speaking, aluminium gives up at around 120-140 deg C (light, cheap and easy to work), steel is good to around 400 deg C (heavy, cheap and generally easy to work), beyond that you are into exotic alloys starting with titanium (light, expensive and hard to machine) and moving into nickel alloys(heavy, expensive and a pig to machine).
 
777236ER
Posts: 12213
Joined: Sat Aug 18, 2001 7:10 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Wed Dec 13, 2006 7:21 am

Quoting Lehpron (Reply 20):
Airplanes are not designed to crash, they are designed to fly.

We wish. Crashworthiness keeps structures people awake at night.
Your bone's got a little machine
 
User avatar
lightsaber
Crew
Posts: 11744
Joined: Wed Jan 19, 2005 10:55 pm

RE: Why Don't Anybody Build Airliners Out Of Steel?

Wed Dec 13, 2006 8:05 am

Quoting 777236ER (Reply 35):
We wish. Crashworthiness keeps structures people awake at night.

 checkmark 
9G crash requirement. Trust me, you have not known engineering pain until you've had to scrap a design because the weight of the wires takes you out of "crash margin."  Wink

Lightsaber
"They did not know it was impossible, so they did it!" - Mark Twain
 
B2707SST
Posts: 1258
Joined: Wed Apr 23, 2003 5:25 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Wed Dec 13, 2006 9:17 am

Quoting 747400sp (Thread starter):
The 2707 and L-2000 both was design to be build out of stainless steal. If

Both aircraft were to be built from titanium alloyed with small amounts of vanadium and aluminum. Stainless steel is too heavy and aluminum loses strength quickly at speeds above Mach 2.2. The XB-70 used a stainless steel honeycomb, but this was largely because the technology to mill titanium was still in development in the 1950s and '60s. Since then, titanium has replaced steel in many applications due to its superior strength-weight ratio.

As in the subsonic realm, most promising material for a new SST would be a heat-resistant composite. This would dramatically reduce aircraft weight and might reduce or eliminate the problems associated with thermal expansion of metallic structures during supersonic cruise.

--B2707SST
Keynes is dead and we are living in his long run.
 
User avatar
ThrottleHold
Posts: 545
Joined: Tue Jul 18, 2006 11:00 pm

RE: Why Don't Anybody Build Airliners Out Of Steel?

Wed Dec 13, 2006 9:35 am

Quoting AirframeAS (Reply 22):
Quoting CosmicCruiser (Reply 21):

Amen.

Signed,
The grammar gremlin.
 
lehpron
Posts: 6846
Joined: Tue Jul 10, 2001 3:42 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Wed Dec 13, 2006 10:00 am

Quoting 777236ER (Reply 35):
Quoting Lehpron (Reply 20):
Airplanes are not designed to crash, they are designed to fly.

We wish. Crashworthiness keeps structures people awake at night.

Took me a while to figure it out: For some reason, I expect planes that survive say a belly landing to be repaired and reflown. I don't know how often it occurs. To make matters worse, I don't think of conventional shapes (which may indeed be repairable after a crash landing).

Quoting HAWK21M (Reply 33):
Whats the Progress with Composites,Temperature resistant wise.

Using Xv408's website of choice:

http://www.key-to-nonferrous.com/Articles/Article103.htm

Quote:
A major effort underway in this area is the Advanced High Temperature Engine Materials Technology Program (HITEMP) of the National Aeronautics and Space Administration (NASA), which focuses on providing revolutionary high-temperature composite materials: to 425°C for polymer-matrix composites (PMCs); to 1250°C for metal-matrix / intermetallic-matrix composites (MMCs / IMCs); and to as high as 1650°C for ceramic-matrix composites (CMCs).

I'd be interested to see the results of their research.

Quoting Xv408 (Reply 34):
beyond that you are into exotic alloys starting with titanium (light, expensive and hard to machine) and moving into nickel alloys(heavy, expensive and a pig to machine).

What about Inconel?  Wink
The meaning of life is curiosity; we were put on this planet to explore opportunities.
 
777236ER
Posts: 12213
Joined: Sat Aug 18, 2001 7:10 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Wed Dec 13, 2006 10:52 am

Quoting Lehpron (Reply 39):

Took me a while to figure it out: For some reason, I expect planes that survive say a belly landing to be repaired and reflown. I don't know how often it occurs. To make matters worse, I don't think of conventional shapes (which may indeed be repairable after a crash landing).

The structures people do quite a lot of work on crashworthiness, both on individual parts to ensure they meet the regulations, and as a concept to increase the crashworthiness of the aircraft as a whole (though I don't think overall crashworthiness is part of the regulations).

Personally, I agree with the jist of what you're saying (I think, you're a bit confusing...). If the industry (read: regulators) were serious about real crash protection, they'd have accepted the repeated recommendations made by many of the accident boards for three-point belts or independent power supplies for DFDR/CVR and should move the industry towards considering crashworthiness as an airframe concept, rather than putting useless seat deceleration rules in place.
Your bone's got a little machine
 
pygmalion
Posts: 815
Joined: Thu Jun 29, 2006 12:47 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Wed Dec 13, 2006 11:36 am

And all the pax would be facing the back of the aircraft.
 
Starglider
Posts: 657
Joined: Sun Oct 01, 2006 12:19 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Wed Dec 20, 2006 7:15 pm

For the XB-70, conventional sheet metal skins, reinforced plates of various constructions, and sandwich or composite panels were designed and evaluated. These studies indicated that the sandwich panel construction showed superior characteristics for the major portion of the airframe. This was largely because a structure with good insulating properties was needed to prevent the aerodynamic heat generated during high-speed flight from raising the temperature of the fuel in the integral tanks to an unacceptable level, thus reducing its value as a heat sink or raising its temperature above the 300 F limit for fuel at the engine feed lines. Although titanium was used in the form of integrally stiffened structures in the forward fuselage, it was eliminated for use as a honeycomb structure. Because the best available titanium alloys could not be brazed and heat treated at the same time and could not be formed to the angles required to produce an efficient corrugation. Today, 45 years since the XB-70 was designed and built, the titanium alloys and production techniques will probably have improved dramatically.

Here are 2 graphs:

The first shows variations of a representative material efficiency parameter with increasing temperature fo a number of structural materials. It is immediately apparent that aluminums typified by RR-58A1 and 2024-T86A1 lose most of their strength in the design temperature range of the XB-70. On the other hand, the corrosion resistant steel alloys, titanium alloys, and H11 steel exhibit good strength characteristics in the 450-630F range.

The second shows the relative thermal efficiency of honeycomb and conventional structure with insulation, from which it is apparent that the honeycomb structure is substantially lighter. Evaluation of additional factors supported the selection of this material. An important factor was the stiffness of the honeycomb panel. The high-speed, long range performance of the XB-70 is achieved through aerodynamic as well as structural efficiency. One aerodynamic efficiency is minimizing drag, because surfaces exposed to airflow are smooth, both on airframe exterior and on the engine air inlet duct walls. The pressures of these airflows produce less deflection in honeycomb sandwich structure, and hence a smoother surface than in conventional (integrally stiffened) airframe structures. The honeycomb sandwich is also more resistant to sonic fatigue caused by the sound pressures developed during high-speed flight and from noise generated by the engines.


Big version: Width: 604 Height: 409 File size: 45kb
Big version: Width: 602 Height: 409 File size: 54kb


Quoting B2707SST (Reply 37):
As in the subsonic realm, most promising material for a new SST would be a heat-resistant composite.

As a honeycomb sandwich construction it would, for the above explained reasons.
 
prebennorholm
Posts: 6409
Joined: Tue Mar 21, 2000 6:25 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Fri Dec 22, 2006 6:01 am

If we strip down a modern airliner, even a "plastic bird", and sort the different components by material from which it was produced, then we will find a surprisingly high percentage of the weight to be steel.

Quoting Saintsman (Reply 18):
Aluminium will conduct electricity as well as steel.

Aluminium is a much better conductor than steel.

Aluminium is by weight the best conductor we have.

By volume only copper is better.

The only reason why aluminium is not much in more widespread use for electric wires etc. is that it has a very bad habit of creating really nasty corrosion where connected to any other metal. Such a joint has to be sealed so it will never be in contact with atmospheric air.

And unfortunately, aluminium-oxide is a very bad conductor.
Always keep your number of landings equal to your number of take-offs
 
L-188
Posts: 29881
Joined: Wed Jul 07, 1999 11:27 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Fri Dec 22, 2006 2:48 pm

One other issue is that the softer Aluminum takes a rivet easier. The Budd Conestoga went with welds instead of rivets. Over time those welds began to develop cracks.

Rivets tend to have more, "give" in them.
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
 
aaden
Posts: 774
Joined: Mon Jan 09, 2006 9:49 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Fri Dec 22, 2006 5:15 pm

[quote=MD11FR8Jock,reply=1]One word, WEIGHT!! Even though there are lots of merits for the strength, the weight difference would make most A/C unable to fly or so heavy that they would not be able to carry any pax or cargo. Even today Boeing and AB are beginning to use substantial amounts of composites that are in many cases just as strong as some types of steel yet weigh less than alum. On a side note both MCI and Prevost superstructers of their coaches are made of Aluminum (Got this from my brother that owns a charter company and runs both types of coaches) I hope this sheds some light on a very admirable idea.



basicly
 
747400sp
Topic Author
Posts: 3833
Joined: Sat Aug 09, 2003 7:27 pm

RE: Why Don't Anybody Build Airliners Out Of Steel?

Wed Dec 27, 2006 1:01 pm

Quoting AAden (Reply 45):
On a side note both MCI and Prevost superstructers of their coaches are made of Aluminum (Got this from my brother that owns a charter company and runs both types of coaches) I hope this sheds some light on a very admirable idea.



basicly

Not to get off subject, but are passenger rail cars still made of steel.
 
B2707SST
Posts: 1258
Joined: Wed Apr 23, 2003 5:25 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Wed Dec 27, 2006 1:28 pm

Quoting Starglider (Reply 42):
As a honeycomb sandwich construction it would, for the above explained reasons.

Not necessarily; the structural construction method depends on the properties of the material being used. Stainless steel seems suited for honeycomb construction for maximum strength-weight. However, the SR-71 and Boeing and Lockheed SST designs, all primarily titanium aircraft, made relatively little use of honeycomb, favoring simpler and cheaper rolled titanium plates riveted to a titanium airframe.

If possible, a composite SST would probably use the integral lay-up process being pioneered on the 787, which allows tape thickness and fiber orientation to vary as needed in each structural component. For example, integral composite structures could probably handle twisting and bending stresses, which are a particular area of concern given the complex shapes of modern cranked-delta SST wings, better than machined aluminum or titanium:



--B2707SST
Keynes is dead and we are living in his long run.
 
User avatar
Starlionblue
Posts: 17058
Joined: Fri Feb 27, 2004 9:54 pm

RE: Why Don't Anybody Build Airliners Out Of Steel?

Wed Dec 27, 2006 10:03 pm

Quoting 747400sp (Reply 46):
Not to get off subject, but are passenger rail cars still made of steel.

Older ones are. Newer high speed cars are normally made of aluminum to save weight.

I believe one of the myriad reasons for the failure of Acela Express was that antiquated safety regs insisted on steel cars, thus making the train much heavier than equivalent European and Asian high speed trains.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Starglider
Posts: 657
Joined: Sun Oct 01, 2006 12:19 am

RE: Why Don't Anybody Build Airliners Out Of Steel?

Fri Dec 29, 2006 6:30 am

Quoting B2707SST (Reply 47):
Not necessarily; the structural construction method depends on the properties of the material being used. Stainless steel seems suited for honeycomb construction for maximum strength-weight. However, the SR-71 and Boeing and Lockheed SST designs, all primarily titanium aircraft, made relatively little use of honeycomb, favoring simpler and cheaper rolled titanium plates riveted to a titanium airframe.

If possible, a composite SST would probably use the integral lay-up process being pioneered on the 787, which allows tape thickness and fiber orientation to vary as needed in each structural component. For example, integral composite structures could probably handle twisting and bending stresses, which are a particular area of concern given the complex shapes of modern cranked-delta SST wings, better than machined aluminum or titanium:

True, depending on the design of the airframe. Current SST studies focus on a cruising speed of Mach 1.6 to 2.4. Perhaps using fuel as a heat sink, and therefore insulation, and aerodynamic loads are less of a factor and merits the use of integral structures more liberally. The SR-71 was a Mach 3+ aircraft and its integral structures, although fluid tight at cruising speed, were allowed to leak as it cooled down. Even if its structure may have been simpler and cheaper when compared to the B-70 design (which was actually delayed during manufacturing to get the fuel tanks fluid tight), i don't think that would be a selling point for a M2.7 to M3 SST design.

I'm sure that the B787 development will create many spin-offs which will contribute to progress, both in- and outside of aviation. Just like the B-70 design did and still does.

Here is an example to quote Boeing on the F-22 Raptor:

"By weight, the Boeing-built portion of the wing is 42 percent titanium, 35 percent composite and 23 percent aluminum, steel and other materials in the form of fasteners, pins and other miscellaneous parts. Each wing measures 16 feet (side-of-body) by 18 feet (leading edge) and weighs approximately 2,000 pounds.

These are the first wings to contain spars produced by resin-transfer molding, an advanced process for manufacturing complex composite parts that reduces cost and improves quality and consistency. Also, the spars use a corrugated "sine-wave" design that makes them stronger and lighter than the traditional "I-beam" design."

Here is one of many B-70 spin-offs: The "sine-wave" spar, although for the B-70, not made from composites but made from titanium sinusoidal webs which were burn-through welded to titanium sheet metal caps to form spar and rib sections, was taken directly from the B-70 design. Boeing, as a subcontractor to North American Aviation, built the XB-70 wings. Boeing has used the "sine-wave" spar design from the B747 onwards to this day.


Starglider

Who is online

Users browsing this forum: No registered users and 16 guests