Cubsrule
Topic Author
Posts: 11656
Joined: Sat May 15, 2004 12:13 pm

Why Not A Twin A346?

Mon Oct 22, 2007 2:46 am

On a (unnecessarily long) journey through ORD this afternoon, I spent some quality time staring at a beautiful IB 346 (EC-JLE, lest anyone cares). And that led me to wondering... if the 772 is a twin, when Airbus was developing the 346, why did it become the 346 instead of, say, the 334? While the wings of the 330 would almost certainly have needed to be redesigned, the 345 and 346 do not share wings with the 342 and 343.

Certainly the whole "4 engines 4 longhaul" mentality at Airbus had something to do with it. I'm also not so sure that the 345 would have been viable as a twin (perhaps I'm wrong). But even if that's true, the 345 is a niche aircraft, and TG is the only carrier that operates both 345s and 346s, so it's not like Airbus gains a lot due to the 345/346 commonality. Am I missing something? Or did Airbus miss the boat in the name of 4 engines 4 longhaul?
I can't decide whether I miss the tulip or the bowling shoe more
 
gigneil
Posts: 14133
Joined: Fri Nov 08, 2002 10:25 am

RE: Why Not A Twin A346?

Mon Oct 22, 2007 2:47 am

They DO share wings with the 342 and 343 for the most part.

There's just an insert to increase span and some obvious strengthening.

NS
 
ikramerica
Posts: 13808
Joined: Mon May 23, 2005 9:33 am

RE: Why Not A Twin A346?

Mon Oct 22, 2007 2:50 am

Because Airbus was shortsighted. That's my opinion. Well, actually, it should have been the A330-500 and A330-600 or something like that. The A330-500 a straight upgrade of the A330-300, like the 777-200LR is the 777-200, to give it 8800nm range. The A330-600 something more like the 350-1000, that is 350 seats and 7500nm range target (which likely would end up 7800 or so). I think they bought into their own quad hype, and it cost them in the long term...
Of all the things to worry about... the Wookie has no pants.
 
Cubsrule
Topic Author
Posts: 11656
Joined: Sat May 15, 2004 12:13 pm

RE: Why Not A Twin A346?

Mon Oct 22, 2007 2:54 am

Quoting Gigneil (Reply 1):
There's just an insert to increase span and some obvious strengthening.

Correct; I should have been more clear, as saying that the 340s do not share wings is quite a bit different than saying that the 73Gs do not share wings with their older siblings. I stand by my previous point, though. Airbus could have modified the 330 wing in much the same way to enlarge the aircraft and increase the range, as the 330 basically has the 343 wing.
I can't decide whether I miss the tulip or the bowling shoe more
 
Leskova
Posts: 5547
Joined: Wed Oct 08, 2003 3:39 pm

RE: Why Not A Twin A346?

Mon Oct 22, 2007 5:54 am

Quoting Cubsrule (Reply 3):
Airbus could have modified the 330 wing in much the same way to enlarge the aircraft and increase the range, as the 330 basically has the 343 wing.

If I recall correctly, modifying the wing itself would not have been sufficient - the landing gear would have had to be lengthened to allow for the larger engines to have enough ground clearance.

However much I enjoy flying on A340s, I do have to agree that it would have been wiser for Airbus to not only expand the 4-engined line, but to at least also expand the twin line (if not only the twins): the A340 has, unfortunately, sold less than spectacularly, something that Airbus originally hadn't expected - according to a book I have in some box in the basement, they expected the split between the A330 and A340 to be something around 1:3... I think they weren't even wrong with the relation between the two, except that they were expecting the A340 to be the better-selling one.

Then again, European and Asian airlines took far longer to embrace the concept of twins than their US counterparts did, so Airbus obviously expected that to create more than enough selling-possibilities; but once the airlines outside of the US started realizing that ETOPS did not constitute a major step down in safety, but that it did - on certain routes - constitute a major step up in revenue, it was obvious that twins would be the way to go...
Smile - it confuses people!
 
gigneil
Posts: 14133
Joined: Fri Nov 08, 2002 10:25 am

RE: Why Not A Twin A346?

Mon Oct 22, 2007 1:43 pm

I don't think the plane being a twin or a quad has as much to do with it as the fact that the A330/340 family has shitty structural efficiency.

Perhaps some part of that is related to wing strengthening for the extra engines, but I don't really think the lion's share.

NS
 
na
Posts: 9211
Joined: Sun Dec 12, 1999 3:52 am

RE: Why Not A Twin A346?

Mon Oct 22, 2007 1:52 pm

Quoting Cubsrule (Thread starter):
Why Not A Twin A346?  

No thanks, I prefer a quad 777!
 Wink
 
trex8
Posts: 4662
Joined: Sat Nov 02, 2002 9:04 am

RE: Why Not A Twin A346?

Mon Oct 22, 2007 2:18 pm

wasn't the problem the availability of the necessary engines which is why the A345/6 was on the market earlier as the 77W/LR needed GEs development of the latest GE90-1xxs
 
AirbusA6
Posts: 1502
Joined: Tue Apr 26, 2005 5:53 am

RE: Why Not A Twin A346?

Mon Oct 22, 2007 3:05 pm

Quoting Trex8 (Reply 7):
wasn't the problem the availability of the necessary engines which is why the A345/6 was on the market earlier as the 77W/LR needed GEs development of the latest GE90-1xxs

Well Airbus could have lauched a slightly shorter A330-400 twin with Trent 892s, which would have produced a better 772ER rival?
it's the bus to stansted (now renamed National Express a6 to ruin my username)
 
zak
Posts: 1926
Joined: Mon Sep 22, 2003 12:17 pm

RE: Why Not A Twin A346?

Mon Oct 22, 2007 3:22 pm

Quoting Cubsrule (Thread starter):
. Am I missing something?

yes, the fuel price was not that big of a part of the equation when the 340NG was developed as it is these days.

10=2
 
Cubsrule
Topic Author
Posts: 11656
Joined: Sat May 15, 2004 12:13 pm

RE: Why Not A Twin A346?

Mon Oct 22, 2007 4:57 pm

Quoting Zak (Reply 9):

yes, the fuel price was not that big of a part of the equation when the 340NG was developed as it is these days.

...but wouldn't carriers prefer to pay less for fuel regardless of what the actual price is?
I can't decide whether I miss the tulip or the bowling shoe more
 
vanguard737
Posts: 523
Joined: Wed Aug 08, 2001 7:02 am

RE: Why Not A Twin A346?

Mon Oct 22, 2007 8:50 pm

I already asked this question a few months ago..and many said it was because the engines being so large would require so much structural changes to the wings as well as the landing gear that is would simply be to costly to be practical.
320 717 722 732 733 735 737 738 744 752 753 763 772 DC9 DC10 MD80 B1900 S340 E120 ERJ CRJ CR7
 
r2rho
Posts: 2475
Joined: Tue Feb 27, 2007 10:13 pm

RE: Why Not A Twin A346?

Mon Oct 22, 2007 8:54 pm

A similar aircraft (in the A343 size though) was, in fact, proposed. It was called the A350 (Version 1.0), and rejected by most customers...
 
zak
Posts: 1926
Joined: Mon Sep 22, 2003 12:17 pm

RE: Why Not A Twin A346?

Mon Oct 22, 2007 8:57 pm

Quoting Cubsrule (Reply 10):

...but wouldn't carriers prefer to pay less for fuel regardless of what the actual price is?

indeed, but it becomes more important versus the other factors when the price per kg of fuel increases a few 100%.

Quoting Vanguard737 (Reply 11):
structural changes to the wings as well as the landing gear that is would simply be to costly to be practical.

apparently, airbus made the development decision with a different oilprice scenario in mind. who knows, if they had known that the barrel would appraoch 100$, they may have concluded that its time for a large twin before.
lufthansa is interesting in this regard, as their well over average fuel hedging allows them to operate on "good ol days" fuel prices, and for them the a346 was good enuff to order quite a bunch of them. one can assume that operating economics with the hedged price did play at least one variable in that decision, even if it might not have been the key factor.
10=2
 
User avatar
SEPilot
Posts: 5022
Joined: Sat Dec 30, 2006 10:21 pm

RE: Why Not A Twin A346?

Mon Oct 22, 2007 9:01 pm

Quoting R2rho (Reply 12):
A similar aircraft (in the A343 size though) was, in fact, proposed. It was called the A350 (Version 1.0), and rejected by most customers...

But that was against the 787, not against the 767/777.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
trex8
Posts: 4662
Joined: Sat Nov 02, 2002 9:04 am

RE: Why Not A Twin A346?

Mon Oct 22, 2007 10:26 pm

Quoting AirbusA6 (Reply 8):
Well Airbus could have lauched a slightly shorter A330-400 twin with Trent 892s, which would have produced a better 772ER rival?

but weren't they after a 747 classic replacement and not a better competitor to the 772ER?
 
CJAContinental
Posts: 343
Joined: Sat May 27, 2006 9:03 pm

RE: Why Not A Twin A346?

Mon Oct 22, 2007 10:54 pm

Quoting Leskova (Reply 4):
However much I enjoy flying on A340s, I do have to agree that it would have been wiser for Airbus to not only expand the 4-engined line, but to at least also expand the twin line

Expanding both lines would be silly. If you had a 330-500, 330-600, then that would probably kill off 340-300, 340-500 and 340-600. You can only do one or the other. Personally, I would have expanded the 330 line, would've taken away a lot from 773ER, more than the present 346.

I think the reason airbus has not done this can be traced to inaccurate, and somewhat unfortunate predictions in the early stages of this decade; with factors like 9/11, the war, increasing oil prices have damaged the four engine popularity if we compare the A340 to the 777.
Work Hard/Fly Right.
 
MD-90
Posts: 7835
Joined: Mon Jan 17, 2000 12:45 pm

RE: Why Not A Twin A346?

Mon Oct 22, 2007 10:57 pm

Quoting Gigneil (Reply 5):
I don't think the plane being a twin or a quad has as much to do with it as the fact that the A330/340 family has shitty structural efficiency.

The A332/A333/A343 do not have shitty structural efficiency.
 
CJAContinental
Posts: 343
Joined: Sat May 27, 2006 9:03 pm

RE: Why Not A Twin A346?

Mon Oct 22, 2007 11:56 pm

Quoting MD-90 (Reply 17):
Quoting Gigneil (Reply 5):
I don't think the plane being a twin or a quad has as much to do with it as the fact that the A330/340 family has shitty structural efficiency.

The A332/A333/A343 do not have shitty structural efficiency.

Well, we don't know that for sure, the engineers came clean about the A346 to the concern of some airlines, though this surely has to be exclusive to the 346 due to the length. I'm scepticle that the engineers didn't realise that by creating a flying pepperami, they may jeopardise the structural quality, though I think airbus may have been reluctant to widen the fuselage on the A346 because their lazy (from A340-200, through to 600, diameter is 5.64m), (I suppose this could not be done on the A345, as range deliberately made this aircraft a niche product, and increasing fuselage diameter would have increased weight, making the aircraft pointless). Although they have to save money where they can, it shouldn't come into practice when the structural quality is seriously affected, which in my opinion, regarding the 346, the quality was affected.



[Edited 2007-10-22 17:04:20]

[Edited 2007-10-22 17:09:51]

[Edited 2007-10-22 17:10:35]
Work Hard/Fly Right.
 
Lemurs
Posts: 1320
Joined: Sat Mar 12, 2005 5:13 am

RE: Why Not A Twin A346?

Tue Oct 23, 2007 1:02 am

Quoting Cubsrule (Reply 10):
...but wouldn't carriers prefer to pay less for fuel regardless of what the actual price is?

Not necessarily. It all depends on where the greatest percentage of your cost is. If one plane burns a few thousand pounds liters of fuel per average sector versus another, but has half the long term operating and maintnance costs, it could be the much better airplane if fuel only costs a few cents per liter.

Essentially: Saving thousands of something worth very little is different than saving a few of something worth a whole heck of a lot. If you're going to run into a burning building to save some bags of money, are you going to grab the huge sack of $1s because "there are so many more!" or are you going to grab the small sack of $1,000s?
There are 10 kinds of people in the world; those who understand binary, and those that don't.
 
Burkhard
Posts: 1916
Joined: Fri Nov 17, 2006 9:34 pm

RE: Why Not A Twin A346?

Tue Oct 23, 2007 11:59 am

I still do not understand why it is inevitable that a quad is less effective than a twin.

Fact is, given the same MTOW, a twin needs more power than a quad if an engine fails during takeoff. So, in the approximation that the weight of the engine is proportional to its power, a quad should be more efficient.

So this is not an inherent explanation. In the case of A345/6 things are more clear. The Trent 500 is a slightly shrinked version of any Trent, still a large engine and so has more than half the weight of a Trent 900. It is the only engine available in this class.

What I wonder more is that comparing the numbers for CF6 vs CFM56 as example, again the smaller engines are not so much lighter - anybody has an insight why?
 
BRxxx
Posts: 74
Joined: Mon Aug 06, 2007 2:29 pm

RE: Why Not A Twin A346?

Tue Oct 23, 2007 12:05 pm

IF it is really made a twin at that time, how is Airbus going to answer the airlines that don't like flying two-engined aircraft over big ponds?
Flown on:A320,A332,A333,B737,B738,B763,B744,B77W,B773,E175,E190,MD90,MD11
 
Burkhard
Posts: 1916
Joined: Fri Nov 17, 2006 9:34 pm

RE: Why Not A Twin A346?

Tue Oct 23, 2007 12:12 pm

It turned out that the number of "airlines that don't like flying two-engined aircraft over big ponds?" was smaller than expected - good old "Safety first!" has been replaced by "Profit only!" in most parts of the world.
 
User avatar
Richard28
Posts: 1638
Joined: Thu Aug 14, 2003 5:42 am

RE: Why Not A Twin A346?

Tue Oct 23, 2007 12:27 pm

Quoting Gigneil (Reply 1):
They DO share wings with the 342 and 343 for the most part.


The A346 wing was a new design to the previous A340/A330 wing.

Quoting CJAContinental (Reply 18):
I think airbus may have been reluctant to widen the fuselage on the A346 because their lazy

I think cost was more of a factor than laziness

if you widen a plane, then its practically a whole new design. to lengthen a plane is a lot lot cheaper.

[Edited 2007-10-23 05:29:00]
 
User avatar
SEPilot
Posts: 5022
Joined: Sat Dec 30, 2006 10:21 pm

RE: Why Not A Twin A346?

Tue Oct 23, 2007 12:37 pm

Quoting Burkhard (Reply 20):
I still do not understand why it is inevitable that a quad is less effective than a twin.

Weight, for one. One large engine weighs quite a bit less than two small ones, even though the two smaller ones need less total thrust. Also, the larger you can build a jet engine the more efficient it becomes in terms of thrust per unit of fuel with all other things being equal. The weight and drag of support structures is also less. The only area where a quad has an advantage is in wing structure, because distributing the engine weight over the wingspan instead of concentrating it near the root allows a lighter wing structure.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
Burkhard
Posts: 1916
Joined: Fri Nov 17, 2006 9:34 pm

RE: Why Not A Twin A346?

Tue Oct 23, 2007 1:11 pm

Quoting SEPilot (Reply 24):
One large engine weighs quite a bit less than two small ones... Also, the larger you can build a jet engine the more efficient it becomes in terms of thrust per unit of fuel with all other things being equal

This seems to be the case, but why? Thrust is proportional to the inlet area in first approximation - more air makes more thrust. Efficiency increases if you increase area over thrust ratio, the by pass ratio.The weight of the turbine also should be proportional to the inlet area - there must be something in the equation that is not proportinal to the area but to the radius only to give an advantage.

I also assume that the weight and drag of support structures on a 737 is lower than on a 777, so this argument could count for half a percent, but not for 10 or twenty.
 
User avatar
SEPilot
Posts: 5022
Joined: Sat Dec 30, 2006 10:21 pm

RE: Why Not A Twin A346?

Tue Oct 23, 2007 1:50 pm

Quoting Burkhard (Reply 25):

This seems to be the case, but why?

I am not an expert in jet engines-perhaps Lightsaber could give us more info. But I do know it to be the case.

Quoting Burkhard (Reply 25):
there must be something in the equation that is not proportinal to the area but to the radius only to give an advantage.

The column of air exiting the engine encounters the air outside the engine, and the boundary between the two is going to be a source of losses. This boundary is defined by the circumference of the column, which is proportional to the radius, not the area.

Quoting Burkhard (Reply 25):
I also assume that the weight and drag of support structures on a 737 is lower than on a 777, so this argument could count for half a percent, but not for 10 or twenty.

The point is that the weight and drag of the four engine pylons of the A340 will be greater than the two on the 777.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
gigneil
Posts: 14133
Joined: Fri Nov 08, 2002 10:25 am

RE: Why Not A Twin A346?

Tue Oct 23, 2007 5:57 pm

Quoting Richard28 (Reply 23):
The A346 wing was a new design to the previous A340/A330 wing.

No, it really wasn't.

NS
 
CJAContinental
Posts: 343
Joined: Sat May 27, 2006 9:03 pm

RE: Why Not A Twin A346?

Tue Oct 23, 2007 7:45 pm

Quoting Richard28 (Reply 23):
I think cost was more of a factor than laziness

if you widen a plane, then its practically a whole new design. to lengthen a plane is a lot lot cheaper.

The point I was trying to make is that although widening the plane would mean a whole new design, and more hassle, money etc... losing out on development costs is the only option if the intentions are to build the aircraft whilst sustaining safety through making sure the structure of the frame is strong. I'm stressing this because although airbus have saved money by making the aircraft longer instead of wider, they have not managed to achieve an adequately strong frame whilst doing so, and therefore, it should not have been built this way in the first place, unless of course they found a way to strengthen the lengthened structure:

http://business.timesonline.co.uk/to...ors/engineering/article1624119.ece
Work Hard/Fly Right.
 
gigneil
Posts: 14133
Joined: Fri Nov 08, 2002 10:25 am

RE: Why Not A Twin A346?

Tue Oct 23, 2007 7:50 pm

The A340-500 and -600 are PERFECTLY safe aircraft.

They have obviously been EXTENSIVELY strengthened, hence my comments about structural efficiency.

The plane is PLENTY strong but as a result of the added structure it is too heavy.

NS
 
Cubsrule
Topic Author
Posts: 11656
Joined: Sat May 15, 2004 12:13 pm

RE: Why Not A Twin A346?

Tue Oct 23, 2007 7:57 pm

Quoting Gigneil (Reply 29):
The plane is PLENTY strong but as a result of the added structure it is too heavy.

Airbus had no choice, though. The 777 family beats the pants off of the 340 in every mission save the few long range missions for which the 345 was designed, and any further delay in getting the second generation 340s to market would likely have resulted in even more market share loss to 777s.
I can't decide whether I miss the tulip or the bowling shoe more
 
AirplaneFan
Posts: 196
Joined: Wed Nov 22, 2006 5:56 am

RE: Why Not A Twin A346?

Tue Oct 23, 2007 9:18 pm

Quoting Cubsrule (Thread starter):
Why Not A Twin A346?

I taught TG & VS already operated that type. Wink

Modified Airliner Photos:
Click here for bigger photo!
Design © Abdullah M.
Template © K.H. Ng - HKAEC


Modified Airliner Photos:
Click here for bigger photo!
Design © Abdullah M.
Template © Joel Vogt
I GOT YOUR SIX
 
flysherwood
Posts: 881
Joined: Thu Jul 20, 2006 2:58 am

RE: Why Not A Twin A346?

Tue Oct 23, 2007 9:24 pm

Quoting NA (Reply 6):
No thanks, I prefer a quad 777!

Now that would have been one hell of an aircraft!!!  Wink
 
flysherwood
Posts: 881
Joined: Thu Jul 20, 2006 2:58 am

RE: Why Not A Twin A346?

Tue Oct 23, 2007 9:26 pm

Quoting R2rho (Reply 12):
A similar aircraft (in the A343 size though) was, in fact, proposed. It was called the A350 (Version 1.0), and rejected by most customers...

That was because the 787 was already around.  Yeah sure
 
Burkhard
Posts: 1916
Joined: Fri Nov 17, 2006 9:34 pm

RE: Why Not A Twin A346?

Wed Oct 24, 2007 9:31 am

To my understanding, the main purpose of the A345/6 was to keep in the large aircraft race until the VLA race gets won. It never was intended to blow away the 773, it was a foot in the door. The two bad years in terms of orders, we know, was that the door opened too late, but that isn't the A346 fault.

What we have to understand is that Airbus has the big advantage of the family concept. They do not really mind if they sell A332,A333,A343,A345,A346 as long as the production line is full for years. Even if an airline that has 10 A346 on order comes in time and says no, better 12 A333, brings them a profit.

This makes aircraft profitable that look awful at order sheet. As example, if I remember well, BA initially ordered A318 as first Airbusses. These got converted to A319-321 later, and these opened the door for BA to order the A380. This alone is worth the development of the A318 - I expect the margin on the A321 to be bigger than on an A318, so they prefer to fill the production slots with the larger ones anyways.
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: Why Not A Twin A346?

Fri Oct 26, 2007 4:58 am

Quoting Burkhard (Reply 20):
I still do not understand why it is inevitable that a quad is less effective than a twin.

Because the TSFC of each individual engine is lower for a quad than an equivalent twin. The twin will burn less fuel for the same trust.

Quoting Burkhard (Reply 20):
So, in the approximation that the weight of the engine is proportional to its power, a quad should be more efficient.

It's not proportional to power, far from it. Max thrust goes up considerably faster than weight, although that's not the driving factor. TSFC goes down with increasing thrust (higher compression ratio and higher bypass), hence larger engines burn less fuel per unit of thrust.

Quoting Burkhard (Reply 25):
Thrust is proportional to the inlet area in first approximation - more air makes more thrust. Efficiency increases if you increase area over thrust ratio, the by pass ratio.The weight of the turbine also should be proportional to the inlet area - there must be something in the equation that is not proportinal to the area but to the radius only to give an advantage

Thrust isn't directly proportional to inlet area, for starters. Efficiency does go up with increased bypass ratio but that's not a size-specific parameter (you can have any bypass ratio at any max thrust level). Weight of the turbine also isn't proportional to inlet area.

What's proportional to radius is the speed of the engine airfoils. Larger engines swing the blade faster at the same RPM.

Tom.

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos