VC-10 From United Kingdom, joined Oct 1999, 3719 posts, RR: 32 Posted (15 years 4 months 4 days 7 hours ago) and read 6516 times:
There have been many references on this forum to the A340 being under powered. Let's look at a few facts.
The principle citeria in the 340 design are a) long range and b) low operating costs.
The results of this are a 6500 Nm range with 295 pax + baggage (27t payload). This has been acheived by:-
1. New technology (high wing efficiency, composite materials etc )
2. A Crz Mach No. of M 0.82 (chosen as result of a survey of prospective purchasers to assess the best compromise of fuel burn & cruise speed)
3. Fuel Burn optimisation which is a result of the previous factors which dictated the choice of engine definition (thrust for T.O. & climb, and optimised specific fuel consumption in cruise).
Twin Vs Quad Engines.
An "all engines operating" twin has a higher thrust than a quad due to the performance requirements in the case of an engine failure during T.O.
A340 with CFM56-5C 4 x 31200 lbs = 124 00 lbs thrust
A330 with GE80C2-A1 2 x 67 500 lbs = 135 000 lbs thrust
This overpowering does have benefits in Clb however.
As a result the time to reach cruise flt lvl in a quad is greater. The 340 could have had a greater ROC but at the expense of a greater engine size and a greater fuel consumption in cruise, thus destroying the balanced design of the a/c. Or, to put it another way, the A340 would not do what it was designed to do if the climb gradient times had been a priority
In the cruise phase however, the quad comes in to its own. The long range cruise Mach No. of 0.82 is, as mentioned previously, a result of a compromise between wing definition & efficiency, engine thrust & size, fuel burn etc.
This cruise speed was commonally agreed by the launching airlines as the best compromise in terms of direct operating costs.
M 0.82 does not penalise traffic, few a/c cruise at M.86 (747) whereas most a/c fly around M.80.
Additionally a/c flying at M.86 use most of the time at a lwr alt than the 340 because of their Max Alt is lower limited
When you compare a 747-400 with an A340 the -400 comes out as overpowered.
The drag/lift ratio of the -400 is 30% higher at low speed & 14% higher at cruise speed. An A340 with a -400 charecteristic wing would require 39 000 lb engines to T.O. at MTOW instead of the 31 200 lb engines it has now.
The initial cruise FL of a -400 after a T.O. at MTOW is lower than that of a 340
-400 Opt FL 295
340 Opt FL 325
The cruise M No. are
-400 M .86
340 M .82
The association of both a higher Crz M No. & lower optimum Flt lvl gives the -400 a far higher fuel consumption e.g.
For an A340 pax load of 295 & a -400 load of 402 over a sector of 4000 Nm the fuel burn is:-
-400 79 T
A340 51 T
or put another way the fuel burn per seat of the -400 is 14% higher than the 340. This difference will increase as the range increases.
So in conclusion the A340 is a well tuned a/c, correctly optimised & fulfilling the intial design objectives.
Ben88 From United States of America, joined Dec 1999, 1093 posts, RR: 2
Reply 1, posted (15 years 4 months 4 days 6 hours ago) and read 5821 times:
Thanks for the informative post. I'm taking my first A340 this summer and i'm very excited about it. From an economical standpoint, the Airbuses seem to be more cost efficient. I am not at all worried about taking an "underpowered" aircraft. I feel very confident that this plane is more than capable.
Dnalor From Australia, joined Mar 2000, 369 posts, RR: 0
Reply 2, posted (15 years 4 months 4 days 6 hours ago) and read 5786 times:
So you did decide to put all those figures together
I spose the sales figures and retainment of fleet over time will tell if the A340 has really met all of its objectives for its buyers.
Personally, from what I have witnessed though, I'd rather be on a 744 or 777 with and engine out on take off over the A340, they just look to be struggling when they leave here @ MTOW ie, full runway used and extremely low ROC compared to the Boeing variants listed above.
No denying their economical status or excelent wing design, just a shame that engines of the same physical size arent available with say 20% more power for better field and initial climb performance.
VC-10 From United Kingdom, joined Oct 1999, 3719 posts, RR: 32
Reply 11, posted (15 years 4 months 4 days 2 hours ago) and read 5685 times:
Dnalor is correct.
I did expect your understandable response Dnalor and I cannot counter it. All I can say is there are enough airlines that operate both types to be able to point Airbus in the right direction if they got their figures wrong. Conversly it is highly likely that Airbus got their Boeing figures from an airline that operates both types.
Anyway I'm off to bed now after my nightshift - so thank you & goodnight
Panman From Trinidad and Tobago, joined Aug 1999, 790 posts, RR: 0
Reply 14, posted (15 years 4 months 3 days 22 hours ago) and read 5665 times:
I have to agree with Dnalor in this respect. I would prefer to see Boeing's figures than Airbus' version of Boeing's performance. This is because I have am currently reading a book on the A340 where the author got his figures from Airbus and Airbus claiming not to have certain information on the 747 that can easily be obtained over the net such as fuselage size. I bet if VC10 was to have gotten the Airbus figures from Boeing they would be different to what he has put here.
Then again there are also many cases when what is written is not what is actually achieved. I have no qualms with the A340 don't get me wrong. I am not a member of the immature Airbus vs Boeing fanclub. But the way I see it the A330 is giving the performance it was designed to do and from all reports the A340 isn't.
Just yesterday I was looking at fully loaded 747s, 777s and A340s takeoff from heathrow and there is no way I would say that the A340s were climbing at anywhere near the same rate as the 744's (according to VC10s p
Richie From Switzerland, joined Dec 1999, 143 posts, RR: 0
Reply 15, posted (15 years 4 months 3 days 20 hours ago) and read 5645 times:
where do you get that ailines effectively operate A340 (-200 and 300 Series) at Mach 0.82. Usually the quads and tri jet aircraft have cruising speeds depending on weather and payload requirements of between 0.81 and 0.84 (only unaware people cruise their 747-400 at 0.86, as it deteriorates the engines much too fast). The actual cruise speed is determined by the settings in the Flight Management Computer. The exception is the A340. It usually cruises in the twin speeds (exception of A330/777) of 0.78 to 0.80.
I have talked to pilots who know the A340, the DC10 and the 747, and thir far preferred aircraft is the DC10, followed by the 747. The A340 is underpowered in their view.
Here a little anecdote: one of the former check captain for PanAm did become one of the major presentation pilots for Airbus and for the A340 in the US. An old friend of his, who was becoming the VP of Operations from a start up (finally they centered on the MD11), asked him, what his aircraft could really do. The Airbus pilot had to admit to his long time friend, that even the747-100 (which was a rela slump) was better in climb than the airbus.
Never believe what the sales book says, look at the real world. Please understand me right, I am very much a friend for airbusses, and one of my most preferred aircraft (short behind the Douglas Tris) is the A330-200, but that does not change the actual performance of the A340. I've sat in evaluation meetings, and one of the most important issues was the effetive performance of the A340-600 and -500 compared to the -200/-300. They (the Airbus sales guys) admitted that their product initially is underpowered. Still does the job, but you don't want to experience an engine failure on a hot and high day.
Flyf15 From , joined Dec 1969, posts, RR:
Reply 16, posted (15 years 4 months 3 days 20 hours ago) and read 5639 times:
Relating back to the original post..
Why is this? The MD-11 is approximately the same size as the A340-300, but it has up to 150% the power of the A340 (MD-11 has 186000lbs of thrust) and a higher cruise speed, yet it still has about the same range as the A340-300? Does it carry more fuel or is it efficient as the A340-300 during flight?
Panman From Trinidad and Tobago, joined Aug 1999, 790 posts, RR: 0
Reply 21, posted (15 years 4 months 3 days 9 hours ago) and read 5591 times:
VC10, a good way to tell if an aircraft is heavily loaded if you are not sure is to look at two things.
1. The length of the takeoff roll and
2. How much the wings are flexed (bent) during initial rotation).
You will never get a lightly laden aircraft with the wings flexed to a high degree on rotation. The bend in the wings is showing how much lift is being generated in order to lift the aircraft off the ground. Now obviously with these aicraft mentioned (747, 777, A340) they are no anorexics even when empty but you can still notice the difference in how much the wings are flexed between an empty 747/777/A340 and a heavy one. Case in point there was one BA 777 followed by an AA 777 and you could tell the AA one was carrying more than the BA 777 it took up more runway and the wings were bent upwards more.
So even though I don't have the figures with me, I was making an educated guess.
As to the book, I agree with you, I doubted myself when I read it that Airbus couldn't get the figures for the 747 fuselage size (yet they quoted the 777). So it was as I was saying constructive figures from Airbus. The book in question was the Airliner Tech Series, Airbus Industrie, Airbus A340, written by Scott E Germain who himself is an A320 pilot. Page 99.