MAUZAO
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A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 3:22 am

On a recent review on AF447 loss published on the brazilian site jetsite.com.br, first official and co-pilot on the AF plane mentioned while entering the stormy area: "... é melhor estarem voando em um A330, pois este tem performance superior ao A340" (... that´s better to be flying on an A330, due it´s superior performance than the A-340).

What they meant? I always imagined that the A-340, for being bigger and having 4 engines, had a much better performance than an A-330. And I feel much more confortable, even safer, flying over the stormy South Atlantic, Brazil to Europe, on any A-340 or B-747-400 than on an A-330. Give me a LX , IB, LH or TP A-340 anytime over an CA, AF or JJ A-330 to Europe!!!

Any thoughts? Thanks.
 
Independence76
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 3:42 am

I can't entirely answer your question, but it would be ironic if it were true. The A340 program was originally marketed with the tagline of "If you're over the middle of the Pacific, you want to be in the middle of four engines."

(Also, by any chance, does anyone have the high-res version of that 2-page advertisement?)

Here:
http://boeingblogs.com/randy/images/stormy%20seas%20ad.jpg
 
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seabosdca
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 4:31 am

With all engines working, twins have more excess power than quads. I think that's all he meant.
 
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ADent
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 6:40 am

One of the design drivers for engine size is one engine out takeoff at MTOW.

If a plane needs 90,000 of thrust to get off the runway in the case a quad engined plane could use (4) 30,000 thrust engines, because with one engine out you still have 90,000.

On a twin you would need (2) 90,000 thrust engines, so with one engine out you still have 90,000.

So in normal, day-to-day use the quad would have 120,000 thrust available and the twin would have 180,000 thrust (at sea level, but at altitude presumably the ratios would be the same).
 
jollo
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 9:52 am

The overall reliability advantage of a 4-holer has nothing to do with thrust margin at cruise.

A340's climb performance at altitude is notoriously sluggish compared to, say, a 777. Of course, that's with all engines running: with one engine out the picture is rather different.
 
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zeke
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 12:22 pm

Quoting jollo (Reply 4):
A340's climb performance at altitude is notoriously sluggish compared to, say, a 777. Of course, that's with all engines running: with one engine out the picture is rather different.

As far as I am aware, the A340-300 will reach a high initial operating altitude than a 777-200ER at max weight, and a A340-600 will climb about 4000 ft higher than a 777-300ER at max weight.
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dennys
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 4:06 pm

Excuse me , but if i had the choice i would prefer crossing any oceans on a 4 jets aircraft !
 
Thenoflyzone
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 4:23 pm

Quoting dennys (Reply 6):
Excuse me , but if i had the choice i would prefer crossing any oceans on a 4 jets aircraft !

Sure, but it doesn't necessarily mean you're any safer than on a twin !

Twice the number of engines means twice as many things could go wrong with those engines.

Quoting zeke (Reply 5):
As far as I am aware, the A340-300 will reach a high initial operating altitude than a 777-200ER at max weight, and a A340-600 will climb about 4000 ft higher than a 777-300ER at max weight.

He's talking about climb performance (i.e rate of climb), not initial climb altitude.

Thenoflyzone
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Semaex
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 4:59 pm

Quoting thenoflyzone (Reply 7):
Twice the number of engines means twice as many things could go wrong with those engines.

Aaah here comes the point that has brought people to the edge of war for centuries  
Often times pilots / airlines / engeneers / pax / enthusiasts argue on what is the better solution. You have the "fail-safe" (redundancy) supporters in the one corner and you have the "damage-tolerant" (over-engeneering) geeks in the other. There are pilots which say that when one engine is out, you're better off still having three instead of one to carry you home. And then there are those who support your view and say "when one engine has a problem, and the other three are the exact same engine, then they might have the same problem". Who's right? I don't know, up to the individual to decide.
You can even extend the discussion onto other airplane structures, for example the school of thought promoting "fly-by-wire". There are those who say that when pullies and levers actuate flight controls, then the more you use those tools the more redundancy the system has, but the likelier it is that one failing component (eg. being stuck) corrupts the whole system.

Interesting topic nontheless, worth thinking about the quad vs. twin performance. It would be great though to know what is meant by "performance", as there are numerous subcategories where, depending on who you ask, a twin is better in the one and a quad better in the other aspect.
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roseflyer
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 5:00 pm

The A332 has more thrust and lower MTOW than the A343 that AF operate. That translates into much better climb performance. The A332 can achieve higher initial cruise altitude than the A343 can when operating near MTOW. However it all depends on the load and weather of a specific flight.
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tjcab
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 5:42 pm

Quoting thenoflyzone (Reply 7):
Twice the number of engines means twice as many things could go wrong with those engines.

With that logic, then one engine should be the best solution.

Why the need for ETOPS then? If cost was not a factor, I would imagine most would prefer more engines.
 
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seabosdca
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 6:48 pm

Quoting tjcab (Reply 10):
With that logic, then one engine should be the best solution.

There is a balance between redundancy and increasing probability of failure as you increase redundancy.

So far, real-world operational history of all types of aircraft seems to indicate that two engines strikes that balance better than any other number, provided the two-engine aircraft is operated to ETOPS standards.
 
135mech
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 7:10 pm

My buddy started going to ATC school. One of the things they were instructed upon was that the A342/343 needed extra "time" to get off of the ground due to being underpowered on normal take off with the small CFM's. They were notorious for taking the "full" runway and their climb rates were sluggish at best. The couldn't climb out of cities fast or high enough, so that might be a factor for maneuverability at altitude.

As I said, this was what the ATC school was teaching future air traffic controllers.
135Mech
 
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Aquila3
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 7:53 pm

Quoting seabosdca (Reply 11):
So far, real-world operational history of all types of aircraft seems to indicate that two engines strikes that balance better than any other number, provided the two-engine aircraft is operated to ETOPS standards.

Respectfully, I beg to disagree.
There is no straight demonstration of that theory that I have seen since now, in mathematical or statistic sense.
First, the demonstration is weak because it is a "reverse" demonstration (A twin did not have a double independent engine failure so it is absolutely reliable), then the sample base is too small for both cases (independent multiple engine failures).
I suspect that the choice of ETOPS (to clarify what I mean: to authorize twins to cross large extents of water) was driven only by economics, and I better I do not go too in deep on how the may have worked.
So, in absence of straight theories I stay with my common sense. Better four than two, God forbids one.
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zeke
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 8:02 pm

Quoting thenoflyzone (Reply 7):

He's talking about climb performance (i.e rate of climb), not initial climb altitude.

That is not how I was reading the OP, getting to altitude to get over weather.

Quoting Roseflyer (Reply 9):
The A332 can achieve higher initial cruise altitude than the A343 can when operating near MTOW.

When the A330 and A340 are operated over the same route, with the same payload, the climb altitude would be the same, same wing. At MTOW the A340 is less than an A330 at MTOW, because it is 40+ tonnes heavier, nothing to do with the engine, it is still higher than a 777 at MTOW.

Quoting 135mech (Reply 12):
My buddy started going to ATC school. One of the things they were instructed upon was that the A342/343 needed extra "time" to get off of the ground due to being underpowered on normal take off with the small CFM's. They were notorious for taking the "full" runway and their climb rates were sluggish at best. The couldn't climb out of cities fast or high enough, so that might be a factor for maneuverability at altitude.

I sure hope that is not what they teach in ATC school. The A340 is NOT underpowered, every takeoff meets regulated performance, it is the exact opposite, it is overpowered, almost every takeoff is performed with less than full thrust. We normally do not use all the thrust available to save on longer term maintenance costs.

Yes an A340 does need more runway than a 737, it is also going a lot further. Even at max weight, I almost never need to use full thrust when departing from a sea level runway at max weight, when I do it is normally due to reported windshear.

A340s do not take the "full" runway, no aircraft does with all engines operating, and the climb rates and initial altitude are often better than a 744 when both are operated at MTOW. This sounds more like a fanboy, rather than someone in industry.

Everyone knows that long haul wide bodies use more runway, and do not have the rate of climb as a short haul twin, it is not rocket science. Most airports in the US however do not get to see regular departures at MTOW, most are short to medium haul flights.

What does effect our performance is that in some countries they do not let us accelerate above our minimum clean speed, the have speed restrictions of 250 kts below 10,000 ft. Heavyweight aircraft need to climb out closer to 300 kts to get their best climb performance.
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Semaex
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 8:05 pm

Quoting 135mech (Reply 12):
The couldn't climb out of cities fast or high enough, so that might be a factor for maneuverability at altitude.

Not exactly sure what the one has to do with the other.

Yes the A340 uses a lot of runway, because if it was going for a larger flap setting for takeoff, then the climb performance would be even worse than it is, hence lower flaps for the TOR.
That said, I'm sure an A340 would never take off on a field where it would be performance limited, so it really doesn't matter whether it takes all the runway or just half of it, as long as it is able to take off. Even for an ATC it's not such a big difference whether a 777 or an A340 is departing. Wake turbulence category is the same, and even if an aircraft is holding short wanting to cross an active runway, it doesn't matter whether the a/c taking off has a TODR of 2000 or 4000 meters.

Quoting seabosdca (Reply 11):
There is a balance between redundancy and increasing probability of failure as you increase redundancy.

That's basically what I was trying to say with my previous comment.

Quoting tjcab (Reply 10):
Why the need for ETOPS then? If cost was not a factor, I would imagine most would prefer more engines.

If cost was not a factor, I'm sure ETOPS whould be the smallest of changes we'd see in the airline industry  
// You know you're an aviation enthusiast when you look at your neighbour's cars and think about fleet commonality.
 
135mech
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 8:38 pm

Quoting zeke (Reply 14):
The A340 is NOT underpowered, every takeoff meets regulated performance, it is the exact opposite, it is overpowered, almost every takeoff is performed with less than full thrust.



I was specifically talking about the A342 and A343 (as i previously mentioned) NOT the A345/A346; I did NOT say the A340. The earlier ones were/are underpowered and there are plenty of pics on this site of them taking off at the END of the runways. [Along with several IL-96's] The A345/346 got the much needed engine upgrade to the frames and are much better capable acft. So, there's no need to be condescending (again) towards others that might know different things.

This quote from the pilots was what led me to this..."(... that´s better to be flying on an A330, due it´s superior performance than the A-340)."

Regards,
135Mech

[Edited 2012-08-22 14:15:52]

[Edited 2012-08-22 14:37:25]
135Mech
 
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Francoflier
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 9:02 pm

If I may digress from the monthly 4 vs. 2 engines debate, I'd like to offer that when you're about to enter a stormy area over the ocean in subtropical regions, you could well have 43 engines, it won't make a hint of a difference to your chances.

Let's not take everything that comes out of pilots' mouths for unchallengeable aviation facts... It's just cockpit talk.
I'll do my own airline. With Blackjack. And hookers. In fact, forget the airline.
 
135mech
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 9:07 pm

Quoting Semaex (Reply 15):
Quoting 135mech (Reply 12):
The couldn't climb out of cities fast or high enough, so that might be a factor for maneuverability at altitude.

Not exactly sure what the one has to do with the other.



Well, the phrase/sentence was...
"The couldn't climb out of cities fast or high enough, so that might be a factor for maneuverability at altitude."

The second part of that was where the sentence was hinged on. At altitude, you may need your engines to "help" you get out of situations from weather, etc... if your engines are smaller and slower responding, you may not get out of that situation as easily or maybe not at all.

"(... that´s better to be flying on an A330, due it´s superior performance than the A-340)."

That was what that sentence (along with the entire post) was going towards.

Not trying to get under your feathers, just putting my two cents in and using my experiences to back them up.

[Edited for spelling]

Regards,
135Mech

[Edited 2012-08-22 14:14:12]

[Edited 2012-08-22 14:17:05]
135Mech
 
135mech
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 9:19 pm

Quoting francoflier (Reply 17):
If I may digress from the monthly 4 vs. 2 engines debate, I'd like to offer that when you're about to enter a stormy area over the ocean in subtropical regions, you could well have 43 engines, it won't make a hint of a difference to your chances.

Let's not take everything that comes out of pilots' mouths for unchallengeable aviation facts... It's just cockpit talk.



What stinks is the sad reality is we lost these lives, it's a very unfortunate thing!

[Edited 2012-08-22 14:27:35]
135Mech
 
roseflyer
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 9:22 pm

Quoting zeke (Reply 14):
When the A330 and A340 are operated over the same route, with the same payload, the climb altitude would be the same, same wing. At MTOW the A340 is less than an A330 at MTOW, because it is 40+ tonnes heavier, nothing to do with the engine, it is still higher than a 777 at MTOW.

Correct me if I am wrong, but I thought climb rate depended more on thrust and efficient cruise altitude depended more on lift/wing. The A332 has a lower weight, but same life and wing as well as more thrust, so it will climb higher and faster.

Quoting zeke (Reply 14):

I sure hope that is not what they teach in ATC school. The A340 is NOT underpowered, every takeoff meets regulated performance, it is the exact opposite, it is overpowered, almost every takeoff is performed with less than full thrust. We normally do not use all the thrust available to save on longer term maintenance costs.

I couldn't agree more that it is not under powered. That's a perception issue. However the A340 certainly has a lower climb rate than the 777 (which is common between twins and quads). If you look at JFK-JNB on the A346 and JFK-HKG on the 77W, the CX 77W averages 21 minutes to cruise whereas the A346 averages 33 minutes to cruise altitude. Both typically are filed at 31,000, so the slower climb rate of the A340 gives the impression of it being underpowered.
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Fabo
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 22, 2012 11:40 pm

Quoting zeke (Reply 14):
The A340 is NOT underpowered, every takeoff meets regulated performance, it is the exact opposite, it is overpowered, almost every takeoff is performed with less than full thrust. We normally do not use all the thrust available to save on longer term maintenance costs.

It IS underpowered - when compared to normal ops on A330 (or 777). That does not mean it has not enough thrust that it needs.

Quoting zeke (Reply 14):
Yes an A340 does need more runway than a 737, it is also going a lot further.

It might also need more runway compared to a 777 that goes just as far, but that is irrelevant, as long as it goes off.

Quoting zeke (Reply 14):
This sounds more like a fanboy, rather than someone in industry.

I guess I could tell that about you. Nothing wrong about liking and defending your plane, but you can be realistic and accept other planes are better in some ways.

Quoting Semaex (Reply 15):
Not exactly sure what the one has to do with the other.

Think vertical manuevering. The reason you are climbing is excess thrust. A twin has more excess thrust than a quad.

Quoting Semaex (Reply 15):
That said, I'm sure an A340 would never take off on a field where it would be performance limited, so it really doesn't matter whether it takes all the runway or just half of it, as long as it is able to take off.

This does not, but this is tower controller.

Quoting Semaex (Reply 15):
Even for an ATC it's not such a big difference whether a 777 or an A340 is departing.

It can be for an approach or center controller. Lets say you route your arrivals under departure track 10 miles off the airport. Assuming normal departure, 777 will be quite a bit higher than the 340.
Similarly if you need an airplane cross perpendicular airway over such and such altitude for traffic separation, 777 will use less time and track to get up there than 340 (and subsequently you might need to keep the 340 under the airway, or vector for avoidance, or similar)
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RE: A330 X A340 Performance: South Atlantic Crossings

Thu Aug 23, 2012 12:12 am

Quoting Roseflyer (Reply 9):
That translates into much better climb performance.
Quoting MAUZAO (Thread starter):
And I feel much more confortable, even safer, flying over the stormy South Atlantic,

Unfortunately in this case, AF447 did still have excess thrust and could climb into a high-speed stall. Ironically, with a worse engine performance at altitude, the outcome might have been better.

While in this case the number of engines was irrelevant, the excess power worked against them here (albeit very very indirectly of course, ultimately the plane merely did what the pilots told it to do).
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jollo
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RE: A330 X A340 Performance: South Atlantic Crossings

Thu Aug 23, 2012 2:24 am

Quoting zeke (Reply 5):
a A340-600 will climb about 4000 ft higher than a 777-300ER at max weight

IIRC the 346 has a service ceiling of about 41000 ft whether the 773ER has a MOA of 43100 ft. If you try climbing to 47000+ ft with your 346, wouldn't you be violating an Airplane Flight Manual operating limitation?

Quoting zeke (Reply 14):
When the A330 and A340 are operated over the same route, with the same payload, the climb altitude would be the same, same wing

? 340-500 and -600 have almost 80 square meters more wing area than any 330.

Quoting zeke (Reply 14):
The A340 is NOT underpowered

I never claimed that.

Quoting zeke (Reply 14):
every takeoff meets regulated performance, it is the exact opposite, it is overpowered, almost every takeoff is performed with less than full thrust.

I'm relieved to hear this! Certification authorities must know what they are doing in handing out type certificates, after all... However, I was talking about climb performance at altitude, not at takoff.

Quoting zeke (Reply 14):
That is not how I was reading the OP, getting to altitude to get over weather.

There you have a point: I was talking about rate of climb, whereas the OP was probably thinking about maximum altitude. My bad.
 
LH707330
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RE: A330 X A340 Performance: South Atlantic Crossings

Thu Aug 23, 2012 2:29 am

Quoting MAUZAO (Thread starter):
On a recent review on AF447 loss published on the brazilian site jetsite.com.br, first official and co-pilot on the AF plane mentioned while entering the stormy area: "... é melhor estarem voando em um A330, pois este tem performance superior ao A340" (... that´s better to be flying on an A330, due it´s superior performance than the A-340).

It's very simple. The A343 and the A332 have the same wing, but the 332 has less structural weight, payload, and fuel, and is therefore lighter. Thus you get more low end margin on your coffin corner in the 332, which was already impacted on the warm night they had. Their computer calculated limit was FL375 IIRC, and it would have been lower in a heavier (for the same mission) 343.
 
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RE: A330 X A340 Performance: South Atlantic Crossings

Thu Aug 23, 2012 3:13 am

Quoting thenoflyzone (Reply 7):
Twice the number of engines means twice as many things could go wrong with those engines

And you can loose twice as many. It all balances out.
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sharles
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RE: A330 X A340 Performance: South Atlantic Crossings

Thu Aug 23, 2012 4:59 am

Quoting rcair1 (Reply 25):
It all balances out.

Except if one takes out the other. Having 4 engines also increases the probability of damage to other aircraft systems (as it increases the probability of catastrophic engine failure).
 
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zeke
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RE: A330 X A340 Performance: South Atlantic Crossings

Thu Aug 23, 2012 8:26 am

Quoting 135mech (Reply 16):
The earlier ones were/are underpowered and there are plenty of pics on this site of them taking off at the END of the runways.

It should be easy for you to show me one then, unless the end you mean the end they commence the takeoff roll from !!!

Quoting 135mech (Reply 16):
This quote from the pilots was what led me to this..."(... that´s better to be flying on an A330, due it´s superior performance than the A-340)."

I fly both, and I do not find them that different to operate when the are operated to their same relative capacity. That being said, I do more short haul work on A330s, and they are going out at time 50t below MTOW, they do perform differently to a A340 on a long haul that would be 90t heavier.

Quoting Roseflyer (Reply 20):
Correct me if I am wrong, but I thought climb rate depended more on thrust and efficient cruise altitude depended more on lift/wing.

True, however the difference on thrust between our A330-300s (RR) and A340s (CFM56) at sea level is only 6,000 lb, at altitude the difference is much smaller as less thrust is being produced by the fan.

Quoting Roseflyer (Reply 20):
The A332 has a lower weight, but same life and wing as well as more thrust, so it will climb higher and faster.

The QRH performance charts for all engines operating for the A330-300 and A340-300 show almost identical cruise altitudes at the same weight.

Quoting Roseflyer (Reply 20):
Both typically are filed at 31,000, so the slower climb rate of the A340 gives the impression of it being underpowered.

The 77W is typically goes to FL290, I used to go to FL330 directly at max weight in the 346.

Quoting Fabo (Reply 21):
It IS underpowered - when compared to normal ops on A330 (or 777). That does not mean it has not enough thrust that it needs.

Underpowered means the thrust is not adequate to meet performance requirements, or payload need to offloaded. The A340 even at MTOW normally takes off with less than full thrust as it is overpowered. You must to too young to remember earlier 4 holers how they used to climb, older aircraft used to have all sorts of tricks to improve performance like water injection.

Quoting Fabo (Reply 21):

It might also need more runway compared to a 777 that goes just as far, but that is irrelevant, as long as it goes off.

The 777 typically will need more runway than an A340 when calculating the takeoff performance.

Quoting jollo (Reply 23):
IIRC the 346 has a service ceiling of about 41000 ft whether the 773ER has a MOA of 43100 ft. If you try climbing to 47000+ ft with your 346, wouldn't you be violating an Airplane Flight Manual operating limitation?

Nothing about service ceiling, it is what the aircraft can achieve at max or normal operating weights. You do not get long haul aircraft operating at max altitudes unless they are very empty. At max weight on the A340 I would typically get to FL330 on a hot day, same conditions on a 77W you would be going to FL290.

Quoting jollo (Reply 23):
340-500 and -600 have almost 80 square meters more wing area than any 330.

I was comparing the A340-300 to the A330-300, essentially the same fuselage and wing, just different engine configurations.

Quoting jollo (Reply 23):
However, I was talking about climb performance at altitude, not at takoff.

And as I said before, the A340 will achieve a high initial cruise altitude than a 777 can at max weights, i.e. A340-300 better then the 777-200ER, and the A340-600 is better than the 777-300ER.
We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
 
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Starlionblue
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RE: A330 X A340 Performance: South Atlantic Crossings

Thu Aug 23, 2012 10:42 am

Quoting MAUZAO (Thread starter):
always imagined that the A-340, for being bigger and having 4 engines, had a much better performance than an A-330

A common misconception.

Quoting dennys (Reply 6):
Excuse me , but if i had the choice i would prefer crossing any oceans on a 4 jets aircraft !

Sure, but there's no statistical or technical basis for your preference.

Quoting 135mech (Reply 12):

My buddy started going to ATC school. One of the things they were instructed upon was that the A342/343 needed extra "time" to get off of the ground due to being underpowered on normal take off with the small CFM's. They were notorious for taking the "full" runway and their climb rates were sluggish at best. The couldn't climb out of cities fast or high enough, so that might be a factor for maneuverability at altitude.

Sure they do. But he should ask his instructors about a fully loaded 744. I dare say it will be no more sporty.

Quoting Aquila3 (Reply 13):
So, in absence of straight theories I stay with my common sense. Better four than two, God forbids one.

"Common sense" does not drive engineering. Results drive engineering. Name one incident on jets where two engines failed due to separate causes.

Quoting francoflier (Reply 17):

If I may digress from the monthly 4 vs. 2 engines debate, I'd like to offer that when you're about to enter a stormy area over the ocean in subtropical regions, you could well have 43 engines, it won't make a hint of a difference to your chances.

Let's not take everything that comes out of pilots' mouths for unchallengeable aviation facts... It's just cockpit talk.

Word. Those pilots would have crashed any airliner.

Quoting Fabo (Reply 21):
It IS underpowered - when compared to normal ops on A330 (or 777). That does not mean it has not enough thrust that it needs.

Tsk. I take "underpowered" to mean "does not mean requirements". The FAA, the JAA and the rest all agree that the 340 has enough power to meet certification requirements.
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RE: A330 X A340 Performance: South Atlantic Crossings

Fri Aug 24, 2012 12:29 pm

Quoting tjcab (Reply 10):
Why the need for ETOPS then? If cost was not a factor, I would imagine most would prefer more engines.

Since 2007, modified ETOPS rules have also applied to 3- and 4-engine aircraft. At least for the U.S. FAA, ETOPS now stands for "Extended Operations". The T no longer stands for "Twin".
 
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RE: A330 X A340 Performance: South Atlantic Crossings

Mon Aug 27, 2012 6:41 am

Quoting thenoflyzone (Reply 7):
Sure, but it doesn't necessarily mean you're any safer than on a twin !

Twice the number of engines means twice as many things could go wrong with those engines.

There has been more than one quad that went on to it's destination even though they had an engine out, a twin can't do that, (depending on where it was when the engine failed).
 
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RE: A330 X A340 Performance: South Atlantic Crossings

Mon Aug 27, 2012 1:36 pm

It's all really very simple: Engines very rarely go wrong, whether operated under ETOPS standards or not. Thus the chances of actually loosing one are pretty low indeed. But, even so, if you loose 1 engine on a 4-holer you have an abnormal situation. If you loose 1 engine on a twin, you have an emergency.

I know which one I prefer.
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RE: A330 X A340 Performance: South Atlantic Crossings

Tue Aug 28, 2012 6:32 am

Quoting zeke (Reply 14):
The A340 is NOT underpowered, every takeoff meets regulated performance, it is the exact opposite, it is overpowered, almost every takeoff is performed with less than full thrust.

By that definition, isn't every aircraft overpowered? Would it be true to say that it is less overpowered than other aircraft?
 
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RE: A330 X A340 Performance: South Atlantic Crossings

Tue Aug 28, 2012 9:03 am

Quoting thegeek (Reply 32):
Quoting zeke (Reply 14):
The A340 is NOT underpowered, every takeoff meets regulated performance, it is the exact opposite, it is overpowered, almost every takeoff is performed with less than full thrust.

By that definition, isn't every aircraft overpowered? Would it be true to say that it is less overpowered than other aircraft?

:D

Getting into semantics I guess. But surely modern aircraft all have more power than necessary to do the job. In part this may be because derating saves engine life, so it might be better to have more power available and not use it than to firewall the engines on every take-off.

Operators only care about excess power (defined as "beyond regulatory minimum requirements") to the extent that it supports the mission. So sure, they'll want more power, but only if it is needed to, say, fly further or heavier.
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RE: A330 X A340 Performance: South Atlantic Crossings

Tue Aug 28, 2012 12:17 pm

Quoting zeke (Reply 27):
And as I said before, the A340 will achieve a high initial cruise altitude than a 777 can at max weights, i.e. A340-300 better then the 777-200ER, and the A340-600 is better than the 777-300ER.

Looks like I'm unable to make myself clear, let me try again with a theoretical situation without any A vs. B strain: A330-300 vs. A340-300 (same wing, different engine configurations, say 2xTrent 700 vs. 4xCFM-56), in level formation flight at FL310, same speed (say M0.78), *same gross weight* at a given instant (and never mind how they got there). At that instant they start together a max rate climb to FL350: which one will get there first (least time)?

IIRC, that boils down to asking which a/c has the highest excess power (not thrust) given the initial conditions.

I don't have a point to prove, I'm genuinely curious. Thanks.

[Edited 2012-08-28 05:41:42]
 
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RE: A330 X A340 Performance: South Atlantic Crossings

Tue Aug 28, 2012 3:03 pm

Quoting jollo (Reply 34):
Looks like I'm unable to make myself clear, let me try again with a theoretical situation without any A vs. B strain: A330-300 vs. A340-300 (same wing, different engine configurations, say 2xTrent 700 vs. 4xCFM-56), in level formation flight at FL310, same speed (say M0.78), *same gross weight* at a given instant (and never mind how they got there). At that instant they start together a max rate climb to FL350: which one will get there first (least time)?

IIRC, that boils down to asking which a/c has the highest excess power (not thrust) given the initial conditions.

All other things being equal, the 330 would have more power, so would reach FL350 first. This is the nature of engine-out regs.
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RE: A330 X A340 Performance: South Atlantic Crossings

Tue Aug 28, 2012 6:24 pm

There is a lot of flak spread over the A340 and especially over the A340-300. If I understand it right this is however one of the more economical on fuel in the 340 family.

This is of course the case for trip vs. the -600 but on a typical 10 hour flight it seems the 340-300, -600 and the 330-200 are pretty close on fuel consumed per pax. The 330-300 would be some 10% better per pax over the 332, 343 and 346. Given that the 340-300 is lower on fuel burn per trip then the -600 is should be more flexible in use if your load-factors vary over the year or week.

I therefore don't understand all the bad words about the 340-300 vs the 340-600, if I don't have routes that can motivate 350 pax frames the -300 should be the better asset then the -600, the trip fuel diff seems to be in the 20% range.

Of course a 333 is the best asset if you only have to go 10 hour legs or less, but if you have the occasional 13-14 hours legs the choice between the 332 and 343 is then really how many pax do you need to haul, 250-ish or more like 300.

Of course engine overhaul cost will hit the 343 and skew the balance more towards the 330 range, now how long-lived are those maxed CFMs on a 340 wing compared to the 330 engines?
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RE: A330 X A340 Performance: South Atlantic Crossings

Tue Aug 28, 2012 10:17 pm

Quoting Starlionblue (Reply 35):
All other things being equal, the 330 would have more power, so would reach FL350 first. This is the nature of engine-out regs.

Perhaps so, but the A340 wouldn't be too far behind it if they both started at the same weight. The A340 uses its one engine out advantage to haul more weight normally, but if the starting weight is the same, there isn't much difference.
 
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 29, 2012 8:14 am

Quoting Starlionblue (Reply 35):
All other things being equal, the 330 would have more power, so would reach FL350 first. This is the nature of engine-out regs.

I think you're correct, but I don't know by how much: one would need the actual speed polars of both ac to quantify the difference. I'd also like to hear the voice of direct experience from zeke.

That said, I'm a fan of the A340 as a passenger: arguably one of the best-looking airliners flying, great comfort for ULR, great reliability, and obviously "right-powered" (or it wouldn't fly daily the longest legs worldwide). I would love a fresh production run with new engines and all the tweaks developed in the meantime for the 330. Alas, it's not gonna happen.
 
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 29, 2012 8:43 am

Quoting jollo (Reply 38):
Quoting Starlionblue (Reply 35):
All other things being equal, the 330 would have more power, so would reach FL350 first. This is the nature of engine-out regs.

I think you're correct, but I don't know by how much: one would need the actual speed polars of both ac to quantify the difference. I'd also like to hear the voice of direct experience from zeke.

I said "all other things being equal", meaning only engine power is different. Same MTOW in other words. With the same MTOW, the same wing and much more power on the 330 it stands to reason it can climb faster. Probably much faster since climb performance is directly correlated to excess thrust.

Definitely a theoretical exercise with little validity in the real world. Big grin

[Edited 2012-08-29 01:45:08]
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tom355uk
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 29, 2012 2:12 pm

Quoting Starlionblue (Reply 39):
much more power on the 330

That's not exactly true is it?? 

The 4 x CFM56-5C's on most A340's have 34k each, whereas 2 x Trent 772's on an A330 have about 71k each, and that is at Sea Level, Standard Day.

At FL350, where the fan makes much less difference to the thrust produced I would guess it is much, much closer than people would think.

I remember reading somewhere about the correlation between static SL thrust and aloft, 0.2-0.25 seems to stick in my mind but I can't be 100% on that.
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ymincrement
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 29, 2012 6:01 pm

I would prefeer being in the middle of 4 engine when crossing the ocean but it may be my psychological needabout safety..  



but what you prefer when you have to overtake on the left ? 4 cylinder classical VW or V8 bmw or a benz?  

thanks
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RE: A330 X A340 Performance: South Atlantic Crossings

Wed Aug 29, 2012 11:30 pm

Quoting tom355uk (Reply 40):
Quoting Starlionblue (Reply 39):
much more power on the 330

That's not exactly true is it?? 

The 4 x CFM56-5C's on most A340's have 34k each, whereas 2 x Trent 772's on an A330 have about 71k each, and that is at Sea Level, Standard Day.

Oops. I guess I walked into that one. "All other things being equal"!!! 
Quoting ymincrement (Reply 41):
I would prefeer being in the middle of 4 engine when crossing the ocean but it may be my psychological needabout safety..

Exactly. Yes, two engines can fail for unrelated reasons but it is so unlikely that the risk is completely acceptable.
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RE: A330 X A340 Performance: South Atlantic Crossings

Thu Aug 30, 2012 1:55 am

Quoting tom355uk (Reply 40):
That's not exactly true is it??

The only part untrue is the exaggeration "much".
 
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RE: A330 X A340 Performance: South Atlantic Crossings

Fri Aug 31, 2012 6:00 am

Quoting zeke (Reply 14):
A340s do not take the "full" runway, no aircraft does with all engines operating, and the climb rates and initial altitude are often better than a 744 when both are operated at MTOW. This sounds more like a fanboy, rather than someone in industry.

Im currently a radar controller and in my experience A340's are pigs. They dont speed up fast or climb fast. I liken them to the classic 747's (-100/200/300) when im working them. When I worked a tower we had Lufthansa and China Airlines A340's and again, both were pigs. They ate up alot of runway (11,000ft +/-) and climbed like dogs. The triple sevens (British Airways, Continental, Air France) didnt eat up as much and climbed better. The Classic 747's were pigs but the newer ones, once up to speed, climb awesome. I dont work many A330's (used to work Air France A332's, now occaisonally Korean Air A330's) but from what ive seen I liken them to 763's or Md11's. Not awesome but not bad for a heavy. When it comes to performance, give me a 77L going 5000nm anyday. Emirate's 77's going IAH-DXB were a little doggy, but still not in the league of A343's or 742's.

So yes, I teach my trainees never to count on an A340 "topping" someone. The 77L, anyday of the week. The A343 (or B742), never. I know its all about weight, but overall in my experience, A343's are pigs.

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RE: A330 X A340 Performance: South Atlantic Crossings

Fri Aug 31, 2012 7:51 am

Quoting atct (Reply 44):
I know its all about weight, but overall in my experience, A343's are pigs.

Yes, they climb slower. But airlines care about economics, not sportscar performance.
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RE: A330 X A340 Performance: South Atlantic Crossings

Fri Aug 31, 2012 10:49 am

Quoting jollo (Reply 34):
A330-300 vs. A340-300 (same wing, different engine configurations, say 2xTrent 700 vs. 4xCFM-56), in level formation flight at FL310, same speed (say M0.78), *same gross weight* at a given instant (and never mind how they got there). At that instant they start together a max rate climb to FL350: which one will get there first (least time)?

They would almost be identical. If anything the A340 might be a little better, the CFMs are a little more responsive for thrust changes, they would spool up faster at that level. Flying at 0.78 would have both aircraft engines operating below normal cruise thrust levels.

Quoting jollo (Reply 34):

IIRC, that boils down to asking which a/c has the highest excess power (not thrust) given the initial conditions.

True, and give the same mach and level, TAS is the same, so it is a matter of excess thrust. The speeds for best rate are slight different between the two.

Quoting tom355uk (Reply 40):

At FL350, where the fan makes much less difference to the thrust produced I would guess it is much, much closer than people would think.

Agreed, looking at takeoff performance, the A330 drops off quicker as density height increases.

Quoting atct (Reply 44):

Im currently a radar controller and in my experience A340's are pigs. They dont speed up fast or climb fast. I liken them to the classic 747's (-100/200/300) when im working them.

I do not care what ATC thinks when I am flying, we look after our aircraft. ATC is there to facilitate the traffic, the traffic is not there to facilitate ATC. I normally never do toga takeoffs, and full thrust climbs, that reduces longer term maintenance costs.

Quoting atct (Reply 44):
When I worked a tower we had Lufthansa and China Airlines A340's and again, both were pigs.

Compared to what types doing what sectors ? with what loads ? what engines ? what speeds ? Without any of the additional information, your comments are idle observations.

Quoting atct (Reply 44):
They ate up alot of runway (11,000ft +/-) and climbed like dogs. The triple sevens (British Airways, Continental, Air France) didnt eat up as much and climbed better.

A340s use less runway than 777s.

Quoting atct (Reply 44):
Emirate's 77's going IAH-DXB were a little doggy, but still not in the league of A343's or 742's.

Our 77W cannot climb as high as an A340 at max weight. The A340-300 will also out climb a 744.

Please review my reply 35 in A340 Lack Of Power - Is It True? (by NEMA Oct 10 2008 in Tech Ops) for some factual comparisons.

Quoting Starlionblue (Reply 45):
Yes, they climb slower. But airlines care about economics, not sportscar performance.

Exactly, the A340 is a gentleman's aircraft, nothing happens fast, and nothing bites. Engine failure after takeoff is hardly noticeable, you know you have heaps of thrust, you know you will clear terrain, and you know you do not have an emergency. Flying a quad in turbulence like a typhoon is much easier than a twin, the thrust couple is not as great, and you only need 4 smaller thrust movements compared to two larger thrust movements on a twin.
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RE: A330 X A340 Performance: South Atlantic Crossings

Sat Sep 01, 2012 8:43 am

Listen, we all know a 340 Classic doesn't leap very sprightly off the ground. Neither does a heavy 747 for that matter. But they are not under-powered, they are just not over-powered the way twins have to be.

I've stood watching a GF A340 trying to defy gravity and attempt to reach BKK or MNL direct from BAH. At 2 in the afternoon, in the July heat. No mean thing for anybody, and that thing just hung there until it vanished in the haze, doing it's best, but generally failing, to overcome gravitational pull and gain altitude. Now the reason I was standing there was because of the first 3S 777F departure to HKG, I think it was. Less than 20 tons of payload onboard, less than half a tank of fuel, and because the aircraft was new they were not yet allowed to do de-rated take-offs. That think came off the ground half way down the runway and shot up like a rocket. And it kept going until it reached F410, whereas I'd hazard a guess the poor A340 would have struggled to reach 10.000 ft before entering Indian airspace. Well, perhaps a bit earlier then  

But is that a fair comparison between the two? Eh, hardly. I know which one is more fun to take-off in, I used to fly the 757, but I'm also of the kind who likes to be surrounded by as many engines as possible when crossing large pieces of nothingness. And for that reason I'll hang in there, willing the poor thing to go up where the air is thin, cause I'd rather have 4 hair-dryers hanging off the wing of a 340 Classique than two industrial grade turbines under a 330, 767, 777 etc. And if it wasn't for the noisy, I'd be even happier to sit in a 747 even if she's hardly an early day altitude master either on a heavy day.

Note that I left the A380 out. That thing needs neither more power or wing. Jeebus, she climbs!
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AirlineCritic
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RE: A330 X A340 Performance: South Atlantic Crossings

Sat Sep 01, 2012 9:38 am

Obviously, people will want a powerful aircraft.

How would we otherwise leave other aircraft standing still, when the light changes to green in an intersection? And isn't power also needed if you need to impress the stewardesses with a quick donut on the runway?
 
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RE: A330 X A340 Performance: South Atlantic Crossings

Sun Sep 02, 2012 4:09 pm

Quoting zeke (Reply 46):
A340s use less runway than 777s.

I believe you that is the truth when using TOGA.

Now, a little mental excercise for FLEX takeoffs. Lets suppose the aircraft is go-limited (because brakes count into stop-limited, and we are not talking brakes).

So, suppose there is a 777 which would normally need 9000ft on a 12000ft runway, AST take-off (same thing as FLEX).
My line of thinking is, 777 uses 200% of single engine AST thrust to accelerate 0-V1 and 100% of thrust to accelerate V1-Vlof. (in V1 cut - limiting situation)

A340 is next in line, and would normally need 7500ft. Uses FLEX.
This A340 uses 133% of OEI thrust to accelerate 0-V1 and 100% V1-Vlof.

As I look at it, A340 will need bigger portion of the runway to get to V1, and then almost the same distance to Vlof on all engines as it would in V1 cut situation.
777 will use smaller part of the runway to get to V1, so it can use big chunk of left runway to accelerate to Vlof if one engine quits.

However, if neither engine quits, it will get to Vlof quickly, and will lift off sooner than A340.


I tried to put my thought into image. Red line is trajectory of either aircraft in case of V1 cut. Blue is normal 777 trajectory and green is normal A340 trajectory.
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