Hi guys,
I have always why the A343 is "underpowered".
I flew it yesterday and the take off roll was so long (with so much vibration)! And the climb was so slow!

Holy crap this subject has come up at least 20 times on this site in various ways.

#1 answer you will hear from Airbus cheerleaders is: it was designed with enough power for the mission and being a quad does not require the reserve power of a twin.

You might also hear an argument that the geared fan it was designed around never made it to production. I'm sure I'm missing something.

Simple mathematics. A plane has to be able to take off with one engine out of action.

When a twin engined plane takes of, and looses one engine, it looses half its thrust. Therefor, one engine has to be able to deliver 100% of thrust needed to safely take off. Therefor total thrust force is 200% of what is needed to safely take-off.

When a quad engined plane takes of, and looses one engine, it looses one quarter of its thrust. Therefor, one engine has to be able to deliver 33% of thrust needed to safely take off. Therefor total thrust is "just" 133% of what is needed to safely take-off.


So, assuming the plane matches the minimum required thrust level, the quad can be build with about a third less thrust then the twin.

(1 - ((100 / 3 * 4) / (100 / 1 * 2))) * 100 =
(1 - (133 / 200)) * 100 =
(1 - 0,66) * 100 =
0,33 * 100 =
33%

LY777 wrote:

I flew it yesterday and the take off roll was so long (with so much vibration)! And the climb was so slow!

A passenger has no way of knowing if the takeoff roll was long or not, nor the rate of climb. Almost every takeoff I did on the A340 was with “FLEX” thrust, an artificial assumed temperature method used as the aircraft has too much thrust, and you could takeoff and climb with less than full thrust even with an engine out.

The A340 runway performance at maximum performance is better than many twins, most passengers who fly on twins are on short to medium haul flights where those aircraft are well below maximum weights, and then try and compare that to an A340 on a long haul flight. If you put a 737 load into an A340, over a short/median haul, the A340 will outclimb it. Once out of TPE for HKG I passed 20,000 ft with the A340 on downwind, doing in excess of 6000 fpm, short 1.5 hr flight with a light load.

Difference in MTOW Between A340-300 and A340-600

610,000 vs 840,000

The A340-600 is 1.37 times the weight of the A340-300

Difference in Max Thrust (Highest rated engines) Between A340-300 and A340-600

61,902*4/34,000*4

136000lb vs 247608lb

The A340-600 has 1.82 times the thrust of the A340-300

It's safe to say that Airbus got the point, and no matter how you try to spin it, the -300 was under powered and Airbus corrected the issue with the heavier variants.

If the -300 wasn't under powered then you would expect the weight and thrust to change by roughly the same amount but those amounts are HUGE.

Andre3K wrote:

Difference in MTOW Between A340-300 and A340-600

610,000 vs 840,000

The A340-600 is 1.37 times the weight of the A340-300

Difference in Max Thrust (Highest rated engines) Between A340-300 and A340-600

61,902*4/34,000*4

136000lb vs 247608lb

The A340-600 has 1.82 times the thrust of the A340-300

It's safe to say that Airbus got the point, and no matter how you try to spin it, the -300 was under powered and Airbus corrected the issue with the heavier variants.

If the -300 wasn't under powered then you would expect the weight and thrust to change by roughly the same amount but those amounts are HUGE.

The -600 had a different wing, and was able to rotate on takeoff less due to its length. At max weight the -600 may have had a faster takeoff speed than the -300, requiring more runway to accelerate - or - more thrust to accelerate to the higher speed in less distance. Directly comparing thrust/weight ratios doesn't provide all the details.

rendezvous wrote:

The -600 had a different wing, and was able to rotate on takeoff less due to its length. At max weight the -600 may have had a faster takeoff speed than the -300, requiring more runway to accelerate - or - more thrust to accelerate to the higher speed in less distance. Directly comparing thrust/weight ratios doesn't provide all the details.

Are you serious? This thread is LITERALLY talking about engine power NOT wing efficiency. The OP didn't ask about wing's or anything of the sort.

But since you want to throw the -600 out over the length let me fix it for you.

A340-300 vs A340-500

610,000 vs 840,000

The A340-500 is 1.38 times the weight of the A340-300

Difference in Max Thrust (Highest rated engines) Between A340-300 and A340-500

58,462*4/34,000*4

136,000lb vs 233,848lb

The A340-500 has 1.7 times the thrust of the A340-300

It doesn't matter if it's the -600 or -500. The change in WEIGHT was VASTLY inferior to the change in THRUST.

And I don't care what kind of wing you have, there is no substitute for thrust. The A340-200 and -300 were under powered, live with it.

And yet as I said above, almost every takeoff I did with the A340-300 was with FLEX thrust as it had too much thrust. Your numbers do nothing to address that simple fact.

zeke wrote:

And yet as I said above, almost every takeoff I did with the A340-300 was with FLEX thrust as it had too much thrust. Your numbers do nothing to address that simple fact.

Every mainstream aircraft could be considered overpowered. An A340 can manage with 3 engines or an A330 with 2, but it obviously wouldn’t be very safe or practical especially during takeoff. This is the same when it comes to cars. Some are much better than others, but generally they have more acceleration and braking performance than they need to make them easier to drive. Not everyone could safely drive something that accelerates and brakes like a bus or truck nor would they want to even if it would save a lot of money to make a car that has that little performance.

I’m confused as to what your point is though. Most takeoffs regardless of plane are done with FLEX (assumed temp if it’s a Boeing) and/or a derate. A330s almost always takeoff on FLEX, but they almost always perform better. Furthermore FLEX may not explain the abysmal climb performance. Dare I say this is a really weak arguement acutally because if your explanation of the A340’s typical performance is 100% correct, then why don’t other planes behave the same way to get extra fuel savings? My suspicion is you are partly correct that the A340 is used slightly different but because the engines really can’t handle the thrust they are rated to make without quick EGT deterioration so in order for them last as long as they should you have to baby them a little more. Similar reason to why most A321s are fitted with V2500s. But again, the A340 isn’t the only plane that takes off everyday with a FLEX temperature, the vast majority of FLEX takeoffs done every day are done by planes that are not the A340.

We got the A343 here from Edelwiess during the summer season and I always got a kick out of how low it stayed in the sky after takeoff. I made a special trip just to see the thing as I do find the A340 exciting, but the best part was the Air Canada 77L that took off just after it that used much less runway and went much steeper into the sky to do almost the same flight the A340 was doing, but the A340 sounded better doing it! Of course this isn’t the fairest of comparisons, but when that 77L and A340 flights used to both be the A330s they always performed better that what the A340 did.

To sum it up in my mind, you take the A330 and give it somewhere between 2000lbf and 4000lbf less but about 8000lbs heavier powerplant configuration and then increase the airframes’s weight in other ways such as the added gear and increase the MTOW you are invariably going to get worse performance unless you make the wing bigger which of course is not the case. Another plus for the A330 in this case is that the engines are actually designed and optimized for the thrust they make, the CFM56 not so much.

Andre3K wrote:

The A340-600 is 1.37 times the weight of the A340-300
The A340-600 has 1.82 times the thrust of the A340-300

It only got 1.2 times the wing area and its aspect ratio is lower.

There goes your improved thrust

Oh yes, the eternal topic. First I heard something about slow climbing A340s was sometime in 2001-02, at this site actually. Those days it was all about slowly climbing A343, when would Northwest replace its DC9s and how does Continental manage to own and operate its own catering company. It´s too bad that while the latter two topics are thankfully history now, this one will surely keep popping up for the next 15 years.

But back to topic: No A340-300 is not exactly underpowered as it can take off with only 3 engines, as per regulation. It is also featuring Flex, a fuel and engine wear saving technique, which can result in longer take-offs and/or slower climb. Yet people are talking about long take offs on A340. But what is a long take-off exactly? Each take-off is carefully calculated before, using full thrust or not. It´s not like pilots line up on the runway, push the thrust forward and start praying for the old timer A343 to actually manage to take off before the runway end.

A340-300 has been used regularly at hot and high airports without more difficulties than other widebodies of its generation. I have experienced slow climb in 340 (sic!), 772, 77W, 738, 330, 320 and so on, and so on. I have experienced my longest take off roll on a AF 747-400. Should I say 747 is underpowered? As for actual speed of climb, that is much less about raw available thrust, and much more about economics, weather and air traffic control. No offense, but someone sitting at 48A has no chance of knowing which factors are being considered in the cockpit, resulting in actual plane performance.

The A343 has been certified as a four-engined airliner.

In regulatory terms that means that it can safely lose an engine on a MTOW-takeoff and proceed to maintain a minimum climb gradient of 3.0%.

It also means that it can lose two engines on approach (naturally at a lighter aircraft weight) and proceed to go-around and safely land after that.

Its airfield perfomance is safe because it has been extensively tested and certified as safe.

Now different safely-certified airliners will of course have different levels of airfield performance. The A343 does indeed have less spectacular airfield performance numbers than other airliners.

Do this simple, quick-and-dirty airfield performance index computation:


A343's thrust-to-weight ratio (at MTOW and max thrust option)

divided by

A343's max wing loading (at MTOW)


You will get a figure that, if compared to the same index computed for other airliners will be one of the lowest of the lot.

The A343's performance is and remains certifiably safe...yet it does not compare favourably with other airliners...which is really not significant at all...except to anutters and assorted other air enthusiasts...


Faro

Andre3K wrote:

Holy crap this subject has come up at least 20 times on this site in various ways.

#1 answer you will hear from Airbus cheerleaders is: it was designed with enough power for the mission and being a quad does not require the reserve power of a twin.

You might also hear an argument that the geared fan it was designed around never made it to production. I'm sure I'm missing something.

The IAE SuperFan would have been less powerful than the CFM56-5C series. IAE projected that the SuperFan would have delivered between 28000 lbf and 32000 lbf, compared to the 31200 lbf to 34000 lbf for the CFM.

The biggest hit was fuel efficiency, not power.

VSMUT wrote:

The biggest hit was fuel efficiency, not power.

Which would have resulted in a much lighter ( OEW, MTOW ) airframe for the same range.
( wing would have been smaller, less tankage, ... overall less thrust required. )

The A330 would have then shown less upgrade potential?

Andre3K wrote:

rendezvous wrote:

The -600 had a different wing, and was able to rotate on takeoff less due to its length. At max weight the -600 may have had a faster takeoff speed than the -300, requiring more runway to accelerate - or - more thrust to accelerate to the higher speed in less distance. Directly comparing thrust/weight ratios doesn't provide all the details.

Are you serious? This thread is LITERALLY talking about engine power NOT wing efficiency. The OP didn't ask about wing's or anything of the sort.

But since you want to throw the -600 out over the length let me fix it for you.

A340-300 vs A340-500

610,000 vs 840,000

The A340-500 is 1.38 times the weight of the A340-300

Difference in Max Thrust (Highest rated engines) Between A340-300 and A340-500

58,462*4/34,000*4

136,000lb vs 233,848lb

The A340-500 has 1.7 times the thrust of the A340-300

It doesn't matter if it's the -600 or -500. The change in WEIGHT was VASTLY inferior to the change in THRUST.

And I don't care what kind of wing you have, there is no substitute for thrust. The A340-200 and -300 were under powered, live with it.

Lol, are you seriously suggesting that we should ignore the wings effect on takeoff performance? That's like wondering why a 500hp truck is slower than my 100hp car but we aren't allowed to talk about weight.

Fred


Sent from my iPhone using Tapatalk

767333ER wrote:

A330s almost always takeoff on FLEX, but they almost always perform better.

The A330 does not perform better, by regulation the A330 only needs to meet a smaller climb gradient engine out.

Secondly the A340-300 would be taking off around 45 tonnes higher MTOW, ie 450 passengers, a 747 load above the A330, and fly a full payload further than a A330.

But don’t let facts get in the way of the fantasy, the A340 outclimbed to the 744 ( in smdistance also 77W in level) to a higher initial cruise level.

Andre3K wrote:

Are you serious? This thread is LITERALLY talking about engine power NOT wing efficiency. The OP didn't ask about wing's or anything of the sort.

Are you serious? This thread is LITERALLY made up of BOTH the topic title (which is limited) AND the OPs first post (which is unlimited)

If you had bothered to read it, you would have noticed;

Original Poster wrote:

I flew it yesterday and the take off roll was so long (with so much vibration)! And the climb was so slow!

The take off roll being "so long" is very basic aerodynamics that even a non-pilot can understand (usually).

What is the power to weight ratio ? This gives us raw acceleration.
What is the V²? This, along with acceleration, defines the length of take off roll.

And what helps to define V²? I think you will find that wing design has just a little to do with that.

As for "the climb was so slow"; I think you will find wing design has some bearing on that too.

But as someone who has yawned his way thru' so many similar debates on this subject, you must already know all this, so why the pretend histrionics?

zeke wrote:

767333ER wrote:

A330s almost always takeoff on FLEX, but they almost always perform better.

The A330 does not perform better, by regulation the A330 only needs to meet a smaller climb gradient engine out.

Secondly the A340-300 would be taking off around 45 tonnes higher MTOW, ie 450 passengers, a 747 load above the A330, and fly a full payload further than a A330.

But don’t let facts get in the way of the fantasy, the A340 outclimbed to the 744 ( in smdistance also 77W in level) to a higher initial cruise level.

If they don’t perform better than the A343, why are we not discussing the A333 being underpowered all the time?

I’ll give you another scenario that I already mentioned if you read my previously reply. On YYC-ZRH Edelwiess was using A333 in previous years, but this year they switched to A343 which has 1 less seat. Not a whole lot of difference there. On the same route one would assume the A330 was using a higher percentage of its available payload than the A340 was and yet the A330 always seemed to use less runway and do much better in the climb below 10000ft or so. All of the active people in the spotters community noticed this too, and these people watched these things everyday they came.

Again:

To sum it up in my mind, you take the A330 and give it somewhere between 2000lbf and 4000lbf less but about 8000lbs heavier powerplant configuration and then increase the airframes’s weight in other ways such as the added gear and increase the MTOW you are invariably going to get worse performance unless you make the wing bigger which of course is not the case. Another plus for the A330 in this case is that the engines are actually designed and optimized for the thrust they make, the CFM56 not so much.

Please read my full reply next time and respond to all of it instead of doing irresponsible cherry picking like the media always does.

Faro wrote:

The A343 has been certified as a four-engined airliner.

In regulatory terms that means that it can safely lose an engine on a MTOW-takeoff and proceed to maintain a minimum climb gradient of 3.0%.

It also means that it can lose two engines on approach (naturally at a lighter aircraft weight) and proceed to go-around and safely land after that.

Its airfield perfomance is safe because it has been extensively tested and certified as safe.

Now different safely-certified airliners will of course have different levels of airfield performance. The A343 does indeed have less spectacular airfield performance numbers than other airliners.

Do this simple, quick-and-dirty airfield performance index computation:


A343's thrust-to-weight ratio (at MTOW and max thrust option)

divided by

A343's max wing loading (at MTOW)


You will get a figure that, if compared to the same index computed for other airliners will be one of the lowest of the lot.

The A343's performance is and remains certifiably safe...yet it does not compare favourably with other airliners...which is really not significant at all...except to anutters and assorted other air enthusiasts...


Faro

WIederling wrote:

Andre3K wrote:

The A340-600 is 1.37 times the weight of the A340-300
The A340-600 has 1.82 times the thrust of the A340-300

It only got 1.2 times the wing area and its aspect ratio is lower.

There goes your improved thrust

Last time I checked WING AREA and THRUST were not the same thing. We aren't talking about climb performance. We are literally talking about the acceleration aspect here. Stop trying to skirt around the issue. It's under powered and nothing you can say about wing area or aspect ration or rotation angle or anything can change the fact that the A340 T/W ratio was terrible.

Guess what? The 707 was under powered. Am i getting butthurt by admitting that? No. So why are you trying to skirt around the truth so bad?

767333ER wrote:

Please read my full reply next time and respond to all of it instead of doing irresponsible cherry picking like the media always does

I did read the entire prior non factual ramblings, and took the key point out and discussed that. I am under no obligation to appease you. You have an agenda that you want to push, and nothing will change your mind.

767333ER wrote:

I’ll give you another scenario that I already mentioned if you read my previously reply. On YYC-ZRH Edelwiess was using A333 in previous years, but this year they switched to A343 which has 1 less seat. Not a whole lot of difference there. On the same route one would assume the A330 was using a higher percentage of its available payload than the A340 was and yet the A330 always seemed to use less runway and do much better in the climb below 10000ft or so. All of the active people in the spotters community noticed this too, and these people watched these things everyday they came.

Over that distance the 343 would carry around 15 tonnes (equivalent to around 150 passengers) more payload than the 333. The 343 also has more thrust, not less than the 333 for takeoff performance, that is predicated on engine out, where the 333 has around 72 klb, and the 343 around 102 klb. On a runway that is takeoff limited on the 333 (ie where the 72 klb cannot lift any more), the 343 would still have excess thrust at the same weights, so they can either have a larger FLEX, carry more payload, or a combination of both.

No one really gives a toss about all engine performance.

SheikhDjibouti wrote:

Andre3K wrote:

Are you serious? This thread is LITERALLY talking about engine power NOT wing efficiency. The OP didn't ask about wing's or anything of the sort.

Are you serious? This thread is LITERALLY made up of BOTH the topic title (which is limited) AND the OPs first post (which is unlimited)

If you had bothered to read it, you would have noticed;

Original Poster wrote:

I flew it yesterday and the take off roll was so long (with so much vibration)! And the climb was so slow!

The take off roll being "so long" is very basic aerodynamics that even a non-pilot can understand (usually).

What is the power to weight ratio ? This gives us raw acceleration.
What is the V²? This, along with acceleration, defines the length of take off roll.

And what helps to define V²? I think you will find that wing design has just a little to do with that.

As for "the climb was so slow"; I think you will find wing design has some bearing on that too.

But as someone who has yawned his way thru' so many similar debates on this subject, you must already know all this, so why the pretend histrionics?

Ok let me make this simple.

No matter what you do or say, if a A340-300 and A340-600 were lined up on tandem runways, in perfect conditions for engine performance. And they are both at max takeoff weight, the -600 will beat the -300 to 100 knots without a doubt. Climbing out it will also beat the -300. I don't care if the wing for the -600 is a little under optimized, THERE IS NO SUBSTITUTE FOR THRUST.


Or are we going to start making fighter jet's with less thrust now because of wing efficiency?

Andre3K wrote:

Climbing out it will also beat the -300. I don't care if the wing for the -600 is a little under optimized, THERE IS NO SUBSTITUTE FOR THRUST.

You are over-simplifying things. Climb rate at any given weight is based on lift, not just thrust. Lift will depend on both thrust and wing efficiency.

Andre3K wrote:

Or are we going to start making fighter jet's with less thrust now because of wing efficiency?

Different missions. An airliner has to make money, and in the A340-class of aircraft, go far. A fighter has to go fast, cost be damned, but nowhere near as far (and if it does need to go far, it gets refuelled in flight). An efficient wing is integral to aircraft performance and economics. An aircraft flies on the wing, not the engine. Fighters have a power-to-weight ratio so high that they can get by with stubby little razor-thin wings that also produce little drag. They didn't call the F-104 a "missile with a man in it" for no reason. But such an airliner would have truly awful economics.

Here's a concrete example of two aircraft with exactly the same engine: a Cherokee 140 and a Cessna 172, both with 150 hp Lycomings.

The Piper has a 30 ft wingspan and 160 sq ft of wing area. MGTOW is 2150 lbs, initial climb at MGTOW 660 ft/min.
The Cessna 172L, same engine, has a 36 ft 1 in wingspan, 174 sq. ft of wing area, 2300 lbs MGTOW, and initial climb of 645 ft/min. At the same weight as the Cherokee, it will out-climb it, in spite of identical engine power; with both at max weight, the Cessna nearly matches the climb rate as the Piper in spite of a 150 lb higher gross weight.

Again, an aircraft flies on the wing, not the engine. Gliders have hugely efficient wings, which is why they need little "engine" power to fly (a glider's "engine" is updrafts... either solar or wind-induced, or the tow plane or winch).

Beech

Andre3K wrote:

Ok let me make this simple.

You can make it simple if you like, but the real world is full of real complications.

Andre3K wrote:

No matter what you do or say,

It's encouraging to see you have such an open mind

Andre3K wrote:

if a A340-300 and A340-600 were lined up on tandem runways, in perfect conditions for engine performance. And they are both at max takeoff weight, the -600 will beat the -300 to 100 knots without a doubt. Climbing out it will also beat the -300. I don't care if the wing for the -600 is a little under optimized,

Sit down and prepare yourself for a shock, because I'm not going to disagree with you.

THERE IS NO SUBSTITUTE FOR THRUST.

This is the old Jeremy Clarkson / Cave man approach. To be fair, it works .....most of the time.

Or are we going to start making fighter jet's with less thrust now because of wing efficiency?

****NEWS FLASH*****
We've been doing that for years already.

Going back to your example of " a A340-300 and A340-600 ...both at max takeoff weight" - what is your point?
I'm betting I could take almost ANY pair of aircraft and make an argument for why one is underpowered compared to the other.
But that proves exactly nothing.
I'm intrigued to discover what you think you have proved.

Andre3K wrote:

No matter what you do or say, if a A340-300 and A340-600 were lined up on tandem runways, in perfect conditions for engine performance. And they are both at max takeoff weight, the -600 will beat the -300 to 100 knots without a doubt. Climbing out it will also beat the -300. I don't care if the wing for the -600 is a little under optimized, THERE IS NO SUBSTITUTE FOR THRUST.

Both aircraft on a standard day wouldn’t need full thrust at MTOW. The 343 would have lower takeoff speeds, and use less runway.

zeke wrote:

Andre3K wrote:

No matter what you do or say, if a A340-300 and A340-600 were lined up on tandem runways, in perfect conditions for engine performance. And they are both at max takeoff weight, the -600 will beat the -300 to 100 knots without a doubt. Climbing out it will also beat the -300. I don't care if the wing for the -600 is a little under optimized, THERE IS NO SUBSTITUTE FOR THRUST.

Both aircraft on a standard day wouldn’t need full thrust at MTOW. The 343 would have lower takeoff speeds, and use less runway.

Yes, but it's definitely underpowered, apparently.

Andre3K wrote:

Guess what? The 707 was under powered. Am i getting butthurt by admitting that? No. So why are you trying to skirt around the truth so bad?

Was the 707 really under powered?
I would say that is a matter of opinion.
The early JT-3C's were a bit of a dog-in-a-manger, but the later models did just fine. And being the most successful airliner of it's generation tells you I am not alone in that thought.
But if you like...yes, it was under powered...compared to an X-15.

Here ya go, the original Boeing 717, c/w water injection

VSMUT wrote:

The IAE SuperFan would have been less powerful than the CFM56-5C series. IAE projected that the SuperFan would have delivered between 28000 lbf and 32000 lbf, compared to the 31200 lbf to 34000 lbf for the CFM.
The biggest hit was fuel efficiency, not power.

SuperFanned A340 must be an A330 class MTOW, needed less power compared to real A340

The original A340 MTOW was around 250 tonnes.

Has society reached a point where people feel offended over hearing that an airplane doesn't have enough power?

speedbird52 wrote:

Has society reached a point where people feel offended over hearing that an airplane doesn't have enough power?

It has on this site.

These 343 threads are so predictable I don't know whether to laugh or cry.

Define "underpowered". What do those who claim the 343 is underpowered mean when they say "underpowered". Subjective assessments like "terrible T/W ratio" don't count. Please define your criteria objectively. Saying the 343 has a lower T/W ratio than the 777-300 is fine, but that that's like saying car A has less horsepower than car B. It's a datapoint but it doesn't make car A less useful per se.

For me, there are only two objective criteria.
- Too little power for the mission? Apparently not or you wouldn't see it being used out of JNB on a summer day.
- Too little power for the certification requirements? Definitely not or it would not have been certified.

If the 343 had not been able to meet certification requirements, or if operators had not bought it at all due to anemic performance, the "underpowered" argument might hold water. But she was certified and sold, if not magnificently, at least decently.

speedbird52 wrote:

Has society reached a point where people feel offended over hearing that an airplane doesn't have enough power?

It's not about that. It's about arbitrary standards of how much oomph an airliner should have, typically coming from non-pilots.

As has been mentioned on this forum thousands of times, unless you're in the cockpit you don't even have any idea what FLEX thrust level is being used. If the runway is long you use less thrust than maximum. Can a take-off at MTOW with 80% of TOGA thrust seem a bit slow from seat 63A? Sure. But that's not an objective measure.

zeke wrote:

Andre3K wrote:

No matter what you do or say, if a A340-300 and A340-600 were lined up on tandem runways, in perfect conditions for engine performance. And they are both at max takeoff weight, the -600 will beat the -300 to 100 knots without a doubt. Climbing out it will also beat the -300. I don't care if the wing for the -600 is a little under optimized, THERE IS NO SUBSTITUTE FOR THRUST.

Both aircraft on a standard day wouldn’t need full thrust at MTOW. The 343 would have lower takeoff speeds, and use less runway.

Again that’s been sidestepping the point. I’m sure the majority here I know that flex takeoffs are the norm. But there is no getting around the fact that the A340-300 has less power for its weight than either of the later models. Anyone who would argue against that is just blinded by stupidity(not saying you, just a general statement)

beechnut wrote:

Andre3K wrote:

Climbing out it will also beat the -300. I don't care if the wing for the -600 is a little under optimized, THERE IS NO SUBSTITUTE FOR THRUST.

You are over-simplifying things. Climb rate at any given weight is based on lift, not just thrust. Lift will depend on both thrust and wing efficiency.

Andre3K wrote:

Or are we going to start making fighter jet's with less thrust now because of wing efficiency?

Different missions. An airliner has to make money, and in the A340-class of aircraft, go far. A fighter has to go fast, cost be damned, but nowhere near as far (and if it does need to go far, it gets refuelled in flight). An efficient wing is integral to aircraft performance and economics. An aircraft flies on the wing, not the engine. Fighters have a power-to-weight ratio so high that they can get by with stubby little razor-thin wings that also produce little drag. They didn't call the F-104 a "missile with a man in it" for no reason. But such an airliner would have truly awful economics.

Here's a concrete example of two aircraft with exactly the same engine: a Cherokee 140 and a Cessna 172, both with 150 hp Lycomings.

The Piper has a 30 ft wingspan and 160 sq ft of wing area. MGTOW is 2150 lbs, initial climb at MGTOW 660 ft/min.
The Cessna 172L, same engine, has a 36 ft 1 in wingspan, 174 sq. ft of wing area, 2300 lbs MGTOW, and initial climb of 645 ft/min. At the same weight as the Cherokee, it will out-climb it, in spite of identical engine power; with both at max weight, the Cessna nearly matches the climb rate as the Piper in spite of a 150 lb higher gross weight.

Again, an aircraft flies on the wing, not the engine. Gliders have hugely efficient wings, which is why they need little "engine" power to fly (a glider's "engine" is updrafts... either solar or wind-induced, or the tow plane or winch).

Beech

That’s cool and all, and I didn’t really learn anything I didn’t know save for the wing areas and weight of those two planes but you are missing te point. We aren’t talking about aircraft with the same power. We are talking about one that OBVIOUSLY is on the LOOOOOW side of the T/W ratios of contemporary designs. Or are you going to argue with the numbers I posted earlier?

SheikhDjibouti wrote:

Andre3K wrote:

Or are we going to start making fighter jet's with less thrust now because of wing efficiency?

****NEWS FLASH*****
We've been doing that for years already.

Going back to your example of " a A340-300 and A340-600 ...both at max takeoff weight" - what is your point?
I'm betting I could take almost ANY pair of aircraft and make an argument for why one is underpowered compared to the other.
But that proves exactly nothing.
I'm intrigued to discover what you think you have proved.

Let’s see a list of fighter aircraft from 1969 till now and I guarantee the T/W ratios have been getting higher. Sure the F-35 is a pig but how many others follow that trend? This really isn’t about fighters it’s just a point.

Nobody is arguing that the A340-200/300 couldn’t:

1. Pass certifications
2. Perform the mission
3. Do it economically

The fact of the matter is, if they thought the thrust to weight ratio was in the butter zone, then they never would have increased it when they upsized to the -500 And -600.

Sure wings can make up for some of the LACK of oomph(like the 777-9 having less thrust than the -300ER) but even then they had to bump up the thrust.

I don’t have a hatred towards the A340, I actually think the -500 is very sexy. But the smaller weaker versions are pigs. And even they fly.

Andre3K wrote:

Last time I checked WING AREA and THRUST were not the same thing. We aren't talking about climb performance. We are literally talking about the acceleration aspect here. Stop trying to skirt around the issue.

If I skirt around anything at all it is your limited grasp of the physics involved.

Question of V1/V2 values.

More wing and better high lift ( no thrust gate forex ) will need less thrust to lift off.
A large well designed wing will have higher L/D which again needs less thrust.

A 777 has all the omphf you seem to expect but can't bring it to bear
as the tire speed limit is reached before all of the runway available is used.

to wit the A343 has all the thrust it needs
The A345/6 have worse L/D and thus need more thrust per ton MTOW.
It all fits together and is definitely not "independent".

LY777 wrote:

Hi guys,
I have always why the A343 is "underpowered".
I flew it yesterday and the take off roll was so long (with so much vibration)! And the climb was so slow!

It's all in the mind and you have convinced yourself that it is so.

Variant ............................................A340-200[145]................. A340-300[146]...............A340-500[112...................A340-600[147]
Take off distance (MTOW, SL, ISA) 2,900 m (9,500 ft)[148] 3,000 m (10,000 ft)[148] 3,350 m (10,990 ft)[149] 3,400 m (11,200 ft)[149]

speedbird52 wrote:

Has society reached a point where people feel offended over hearing that an airplane doesn't have enough power?

If you want to become a pilot, I suggest you buckle up and read/listen to those who know what they're talking about.

LY777 wrote:

I have always why the A343 is "underpowered".
I flew it yesterday and the take off roll was so long (with so much vibration)! And the climb was so slow!

Most airliners, especially quads, use extensive thrust reduction methods. The 747 which has far higher takeoff speeds than the 340 (and thus runway requirements) is able to use flex/atm regularly, even when it's near mtow. As for why your climb was slow, that could be for a number of reasons but more often than not, it's due to atc requirements. Sometimes airlines will have derate climb policies depending on aircraft type which further decrease climb rate. Our A330s, 777s and 787s have a derate climb setting. The A340-500/600 have derate options too but you'll have to defer to Zeke for the -300.

Someone posted an AF A340 takeoff clip from Juliana a few months ago. It shows the A340 can move when she needs to.

No, the A340-200/300 doesn't reach cruising altitude in record time. BFD; it'll get there in its own good time, providing the most quiet cabin in its class whilst doing so.

Andre3K wrote:

zeke wrote:

Andre3K wrote:

No matter what you do or say, if a A340-300 and A340-600 were lined up on tandem runways, in perfect conditions for engine performance. And they are both at max takeoff weight, the -600 will beat the -300 to 100 knots without a doubt. Climbing out it will also beat the -300. I don't care if the wing for the -600 is a little under optimized, THERE IS NO SUBSTITUTE FOR THRUST.

Both aircraft on a standard day wouldn’t need full thrust at MTOW. The 343 would have lower takeoff speeds, and use less runway.

Again that’s been sidestepping the point. I’m sure the majority here I know that flex takeoffs are the norm. But there is no getting around the fact that the A340-300 has less power for its weight than either of the later models. Anyone who would argue against that is just blinded by stupidity(not saying you, just a general statement)

Because it is a Quad and a Quad does not need that much power as, one engine does not need to have enough power to allow a save take-off.

A Á340 with 3 engines operating climbs better than a later aircraft with one engine out and that is what matters from a safety point of view.

Irony mode one.

C'mon you people. You pilots are all stupid and don't get it. All 4holers are poor performers, and I know how to fill a gap. Since 4holler needs 33% extra thrust (gets required climb gradient in engine failure scenario), and two holers need 100% extra thrust, there's no arguing. Two holers are simply better performers.

Irony mode two.

To all those claiming the performance is important: Go and get your extra 300, or other acrobatic, they're the best. But remember, since your thinking is one dimension, don't expect it to do required climb out gradient if the engine fails. But hey, I'm just having problem admitting that it's not.

Irony mode off.
Trolls spotted. Not worth any effort, discussion is where you assume other side to be ready to accept arguments. Go find your playground children. Any mod to clear up?

Have fun

Cheers,
Adam

PS. Sorry for some lame explanations in irony sections, had to overpaint the picture to suit the purpose better.

Andre3K wrote:

Again that’s been sidestepping the point. I’m sure the majority here I know that flex takeoffs are the norm. But there is no getting around the fact that the A340-300 has less power for its weight than either of the later models. Anyone who would argue against that is just blinded by stupidity(not saying you, just a general statement)

Nothing was sidestepped, it was a simple statement of fact.

You have missed a number of the aspects of the physics involved, which has blind sighted your outlook. The 340NG has higher rolling friction by virtue of the additional wheels and mass, and additional drag. With the higher mass however with only a little bit more wing area, higher speeds are required to generate the lift to reach relative to the increased mass. It is the greater rolling friction, greater drag, and higher operational speeds results longer takeoff distances.

Don’t underestimate the effect increase or decrease in drag has on takeoff performance, for example with 777X the reduced drag of the wing means the engines can be smaller for the same TOW and achieve better performance. Your incorrect perception would have the 777X with worse takeoff performance relative to the 77W by virtue it has a lower thrust to weight ratio.

It is not the simplistic incorrect perception you have stated of higher thrust to weight means greater performance, rolling friction, lift, and drag also play their roles.

zeke wrote:

Andre3K wrote:

Again that’s been sidestepping the point. I’m sure the majority here I know that flex takeoffs are the norm. But there is no getting around the fact that the A340-300 has less power for its weight than either of the later models. Anyone who would argue against that is just blinded by stupidity(not saying you, just a general statement)

Nothing was sidestepped, it was a simple statement of fact.

You have missed a number of the aspects of the physics involved, which has blind sighted your outlook. The 340NG has higher rolling friction by virtue of the additional wheels and mass, and additional drag. With the higher mass however with only a little bit more wing area, higher speeds are required to generate the lift to reach relative to the increased mass. It is the greater rolling friction, greater drag, and higher operational speeds results longer takeoff distances.

Don’t underestimate the effect increase or decrease in drag has on takeoff performance, for example with 777X the reduced drag of the wing means the engines can be smaller for the same TOW and achieve better performance. Your incorrect perception would have the 777X with worse takeoff performance relative to the 77W by virtue it has a lower thrust to weight ratio.

It is not the simplistic incorrect perception you have stated of higher thrust to weight means greater performance, rolling friction, lift, and drag also play their roles.

I have not ignored any of that, but i don't know the rolling friction and drag differences between the two, so why would i speak on it?

What i do know is that the thrust to weight ratio is much lower for the -200/300 models over the -500/600.

Are you ever going to speak on that or just keep bringing up things even you have no numbers for?

Chaostheory wrote:

Someone posted an AF A340 takeoff clip from Juliana a few months ago. It shows the A340 can move when she needs to.

You mean when it's nowhere near MTOW like all the other aircraft that takeoff out of there?

WIederling wrote:

Andre3K wrote:

Last time I checked WING AREA and THRUST were not the same thing. We aren't talking about climb performance. We are literally talking about the acceleration aspect here. Stop trying to skirt around the issue.

If I skirt around anything at all it is your limited grasp of the physics involved.

Question of V1/V2 values.

More wing and better high lift ( no thrust gate forex ) will need less thrust to lift off.
A large well designed wing will have higher L/D which again needs less thrust.

A 777 has all the omphf you seem to expect but can't bring it to bear
as the tire speed limit is reached before all of the runway available is used.

to wit the A343 has all the thrust it needs
The A345/6 have worse L/D and thus need more thrust per ton MTOW.
It all fits together and is definitely not "independent".

Do not confuse my lack of A.net dissertation's for lack of understanding. I was shoving these posts out in the few breaks I have at work.

Why are you bringing up the 777? I'm not comparing a quad to a twin, that's ridiculous.

Do me a favor, answer this one question. If you put a giant scale behind a A340-300 and an A340-600 and connected them via some cable at an appropriate hard point, which one would pull harder?

Let's take an example where none of you can start shoving in a million other variables, one that is closer to home for me.

The C-5B had 43,000lb of thrust for each engine, the C-5M has about 53,000lb of thrust per engine. The performance between the two is night and day. For a plane as heavy as the 747 it was under powered, can we all agree? Of course it could still fly mission's, but not like it does as the C-5M. The original engines were almost as weak as the C-17 engines which is sad for a plane that weighs so much more. Yes the C-5 wing is a high lift wing but it's also designed in the 50/60's. Lockheed admitted by proxy that the C-5 was under powered 2 times now. The first was the step up from 41,000lb thrust to 43,000lb thrust and then of course the -M mod.

That is a VERY similar situation they A340 had going on. The difference is, in the military they just add more power, in the civilian world they usually try change other aspects in the process as well.

Andre3K wrote:

I have not ignored any of that, but i don't know the rolling friction and drag differences between the two, so why would i speak on it?

What i do know is that the thrust to weight ratio is much lower for the -200/300 models over the -500/600.

Are you ever going to speak on that or just keep bringing up things even you have no numbers for?

I am not the one making the assertion, you are. Feel free to do the calculations for yourself http://www.dept.aoe.vt.edu/~lutze/AOE31 ... anding.pdf

Andre3K wrote:

Why are you bringing up the 777? I'm not comparing a quad to a twin, that's ridiculous.

If your higher thrust to weight ration “law” was actually true, it should not matter the number of engines being discussed. The 77W to 77X is an interesting discussion point at they have the same MTOW, however the 77X has less thrust installed than the 77W because the wing improvements reduced the drag. The gear configuration is the same, the weights are the same, however the 77X with less thrust has better takeoff performance than the 77W.

Your thrust to weight ratio “law” isn’t actually true.

zeke wrote:

Andre3K wrote:

I have not ignored any of that, but i don't know the rolling friction and drag differences between the two, so why would i speak on it?

What i do know is that the thrust to weight ratio is much lower for the -200/300 models over the -500/600.

Are you ever going to speak on that or just keep bringing up things even you have no numbers for?

I am not the one making the assertion, you are. Feel free to do the calculations for yourself http://www.dept.aoe.vt.edu/~lutze/AOE31 ... anding.pdf

Andre3K wrote:

Why are you bringing up the 777? I'm not comparing a quad to a twin, that's ridiculous.

If your higher thrust to weight ration “law” was actually true, it should not matter the number of engines being discussed. The 77W to 77X is an interesting discussion point at they have the same MTOW, however the 77X has less thrust installed than the 77W because the wing improvements reduced the drag. The gear configuration is the same, the weights are the same, however the 77X with less thrust has better takeoff performance than the 77W.

Your thrust to weight ratio “law” isn’t actually true.

First I already spoke on the 777 earlier. Second I am only talking about the difference in T/W of the -200/300 vs the -500/600. Speak on that. The increase in thrust is much higher than the increase in weight. I’m not talking about the difference in L/D or wing area, or rolling friction or anything OTHER than the drastic T/W ratio increase. Let’s talk about that. Can we do that?

Andre3K wrote:

That is a VERY similar situation they A340 had going on. The difference is, in the military they just add more power, in the civilian world they usually try change other aspects in the process as well.

In the military they have zero interest in cost and efficiencies.

Additionally for a military lifter better runway and climb rate performance
is of interest. It increases flexibility and the time unfriendlies can shoot at you.

But:
AFAIK did the A343 never have problems fulfilling its spec performance.
It wasn't even the fuel hog it was alleged to be.

Chaostheory wrote:

speedbird52 wrote:

Has society reached a point where people feel offended over hearing that an airplane doesn't have enough power?

If you want to become a pilot, I suggest you buckle up and read/listen to those who know what they're talking about.

Take that as a yes

Andre3K wrote:

Chaostheory wrote:

Someone posted an AF A340 takeoff clip from Juliana a few months ago. It shows the A340 can move when she needs to.

You mean when it's nowhere near MTOW like all the other aircraft that takeoff out of there?

I haven't watched the video, and neither do I know the exact circumstances. But apparently you do.
Why was this A340 nowhere near MTOW? Was it on a positioning flight? Had all the passengers missed their connections?

And why do "all the other aircraft" take off at or near MTOW?
SXM -AMS is only 3747nm, and SXM-CDG even less. Are those planes at MTOW?
What about the US flights? Isn't the US even closer?