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A340 Under Powered?  
User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3702 posts, RR: 34
Posted (14 years 5 months 3 weeks 2 days 6 hours ago) and read 5518 times:
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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.

e.g.

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.





56 replies: All unread, showing first 25:
 
User currently offlineBen88 From United States of America, joined Dec 1999, 1093 posts, RR: 3
Reply 1, posted (14 years 5 months 3 weeks 2 days 5 hours ago) and read 4823 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.

User currently offlineDnalor From Australia, joined Mar 2000, 369 posts, RR: 0
Reply 2, posted (14 years 5 months 3 weeks 2 days 5 hours ago) and read 4788 times:

So you did decide to put all those figures together  
well done

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.


User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3702 posts, RR: 34
Reply 3, posted (14 years 5 months 3 weeks 2 days 5 hours ago) and read 4775 times:
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The following gives a comparison of time/distance from brakes release needed to reach 4 different Flt Lvls for both a -400 and an A340-300 taking off @ MTOW

FL ------------ A340-----------400

150 -----------11'/51Nm -------10'/50 Nm

100------------ 8'/29 Nm -------7'/27 Nm

50--------------5'/15 Nm -------4'/16 Nm

15--------------3'/7 Nm---------3'/-

Both a/c have similar T.O. & intial climb charecteristics


User currently offlineDnalor From Australia, joined Mar 2000, 369 posts, RR: 0
Reply 4, posted (14 years 5 months 3 weeks 2 days 4 hours ago) and read 4753 times:

Can you tell me where you get all those figures from?

User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3702 posts, RR: 34
Reply 5, posted (14 years 5 months 3 weeks 2 days 4 hours ago) and read 4740 times:
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A340 Flt Crew Operating Manual

User currently offlineDnalor From Australia, joined Mar 2000, 369 posts, RR: 0
Reply 6, posted (14 years 5 months 3 weeks 2 days 4 hours ago) and read 4720 times:

And the Boeing figures?

User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3702 posts, RR: 34
Reply 7, posted (14 years 5 months 3 weeks 2 days 3 hours ago) and read 4714 times:
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Same Place !

User currently offlineDnalor From Australia, joined Mar 2000, 369 posts, RR: 0
Reply 8, posted (14 years 5 months 3 weeks 2 days 3 hours ago) and read 4709 times:

hmmm, I'd be interested to see Boeing's own figures.

Kinda like Cessna having Piper performance figures in a Cessna manual.
Doesn't make sense.


User currently offlineBen88 From United States of America, joined Dec 1999, 1093 posts, RR: 3
Reply 9, posted (14 years 5 months 3 weeks 2 days 3 hours ago) and read 4705 times:

I think VC-10 means he got the Airbus figures from the A340 manual and the Boeing figures from the 744 manual. Why would the A340 manual have Boeing 744 specs in it? Thanks VC-10......good post

User currently offlineDnalor From Australia, joined Mar 2000, 369 posts, RR: 0
Reply 10, posted (14 years 5 months 3 weeks 2 days 2 hours ago) and read 4690 times:

That's not how I read it Ben  

User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3702 posts, RR: 34
Reply 11, posted (14 years 5 months 3 weeks 2 days 2 hours ago) and read 4687 times:
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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


User currently offlineDnalor From Australia, joined Mar 2000, 369 posts, RR: 0
Reply 12, posted (14 years 5 months 3 weeks 2 days 1 hour ago) and read 4685 times:

Good point VC-10

Yeah both are very good airliners catering to different needs.

Night, sleep well.


User currently offlineSndp From Belgium, joined Feb 2000, 553 posts, RR: 2
Reply 13, posted (14 years 5 months 3 weeks 2 days ago) and read 4659 times:

Where did you got these manuals from, VC-10?
thanks
sndp


User currently offlinePanman From Trinidad and Tobago, joined Aug 1999, 790 posts, RR: 0
Reply 14, posted (14 years 5 months 3 weeks 1 day 21 hours ago) and read 4667 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


User currently offlineRichie From Switzerland, joined Dec 1999, 143 posts, RR: 0
Reply 15, posted (14 years 5 months 3 weeks 1 day 20 hours ago) and read 4647 times:

VC10

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.


User currently offlineFlyf15 From , joined Dec 1969, posts, RR:
Reply 16, posted (14 years 5 months 3 weeks 1 day 19 hours ago) and read 4641 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?


User currently offlineWorldTraveller From Germany, joined Jun 1999, 624 posts, RR: 5
Reply 17, posted (14 years 5 months 3 weeks 1 day 19 hours ago) and read 4639 times:

Airbus did a lot of tests with the A340 in hot and high environments.

In Quito, Ecuador, the did take-off's with only two engines running (both on one side), and absolutely no problems surfaced.

The 747 classics and the DC-10 may have better climb rates, but do you know how much fuel they burn until they reach cruising altitude?? A LOT!

I think the A340's slower climb rate was never a reason not to order this plane!

Regards


User currently offlineDnalor From Australia, joined Mar 2000, 369 posts, RR: 0
Reply 18, posted (14 years 5 months 3 weeks 1 day 19 hours ago) and read 4633 times:

Richie first of all thanks for your ealier post and relevent comments.

How heavy was the A340 that took off with two engines on one side out???? I thought double Assymetric training and testing was a big no no especially since the RAAF lost a 707 and 5 crew that way.

Flyf15 150%????? I cant get that on my calculator, wanna recheck the maths on that one mate???  


User currently offlineCricri From France, joined Oct 1999, 581 posts, RR: 7
Reply 19, posted (14 years 5 months 3 weeks 1 day 18 hours ago) and read 4625 times:

There is a little joke among the A340 tech crews saying that thank god the earth is curved for a t/o with this plane...  

User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3702 posts, RR: 34
Reply 20, posted (14 years 5 months 3 weeks 1 day 11 hours ago) and read 4611 times:
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Sndp
The manuals are in my office.

Panman.
I find it difficult to believe AI can't get such basic 747 info. I would question the how good the book is.

How do you know the 777's, 747 & A340's were all operating at or close to MTOW ?

Richie
All the info came from FCOM Bulletin, not a sales brochure.

Flyf15
I have no idea what the fuel capacity of the MD-11 is.

Finally I have no particular views on the subject, I just thought I would throw into the debate the figures I have at my disposal



User currently offlinePanman From Trinidad and Tobago, joined Aug 1999, 790 posts, RR: 0
Reply 21, posted (14 years 5 months 3 weeks 1 day 8 hours ago) and read 4593 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.

Page99


User currently offlineFlyf15 From , joined Dec 1969, posts, RR:
Reply 22, posted (14 years 5 months 3 weeks 1 day 7 hours ago) and read 4589 times:

A340 with CFM56-5C4 4x31200 lbs = 124800lbs thrust
MD-11 with PW4462 3x62000 lbs = 186000lbs thrust

186000/124800 = 1.49 (approx 150%)



User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3702 posts, RR: 34
Reply 23, posted (14 years 5 months 3 weeks 1 day 7 hours ago) and read 4585 times:
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I make that 50% more power

User currently offlineFlyf15 From , joined Dec 1969, posts, RR:
Reply 24, posted (14 years 5 months 3 weeks 1 day 6 hours ago) and read 4583 times:

"but it has up to 150% the power"

50% more or 150% of... same thing, sorry they got confused.


25 Dnalor : I would have called that 50% more too but I see what you mean now Flyf15
26 Richie : VC10 that is very nice, but I recently talked to some ATC guys, and their biggest worry is, that A340s never make the projected climb and trouble the
27 Iberiaa340 : VC-10, very informative post. With the demise of the DC-8 and 707, it is good to see a smaller 4 engine comercial aircraft for spotting. Sure it's a l
28 ZRH : Will the A340-500/600 be better powered?
29 Panman : Yes they will be using Trent 500s which are about twice as powerful as the CFM56. Don't have the exact figures. PANMAn
30 Ruscoe : If the A342 & A343 are not underpowered why are the A345 & A346 going to have a signifigantly higher thrust to weight ratio? Ruscoe
31 Panman : Because they won't be using CFM56s (i.e. engines designed for the Boeing 737) which are only capable of producing around 30000 lbs.thrust. The Trent 5
32 Turbulence : It has been said so macuh about this subject!!! As World Traveller says, I do not think the ROC is a sales argument. Something which is much more impo
33 Tripl7 : I flew on an A340 three months after it was introduced in service by (launch customer?) Lufthansa. The plane was D-AIBA, now wearing the Star alliance
34 Panman : "We also spoke about winglets, and when I asked the Captain what is the advantage of the winglets, he replied that the plane simply looks better ! " T
35 Tripl7 : Panman, would you fly in aircraft with no pilots? I agree that some pilots are a detriment in the cockpit for serveral reasons, including being incapa
36 FDXmech : The onboard computers I take it you are referring to are the flight management computers (FMC). The specific function I think you are talking about, "
37 TEDSKI : Airbus, because the development of the IAE Superfan version of the V2500 was dropped they had to go for the CFM56. I think this was a mistake to put a
38 Prebennorholm : Please keep in mind that the name CFM-56 refers to an "engine family". Those on the A340 are roughly 50% more powerful than an avarage CFM-56 on 737 o
39 Post contains links Dnalor : Re thrust to weight ratios, check this out http://www.airliners.net/discussions/general_aviation/read.main/211609/
40 Dash8 : This subject isn't all that complex. All modern jetliners have FMC's with CI, optimum flight altitude/cruise speed calculations. All are designed to b
41 777x : An A340 might continue to fly w/ 2 engines, but it could never climb out - that's what everyone's talking about AFAIK for certification, 4 holers need
42 Prebennorholm : A340-300 with CFM56-5C4 at MTOW is 4.21lbs per pound of thrust. Airliners have a lift to drag ratio (L/D) in the low 20'es meaning that it needs 1/20
43 TEDSKI : I was in Rolls Royce's website where I read that yesterday 20 Jun 2000, marked the first flight of the new RR Trent 500 that will be used on the A340-
44 TEDSKI : Airbus A340-300 CFM56, 34,000X4=136,000 Boeing 777-200ER RR Trent 895, 98,000X2=196,000
45 VC-10 : A340-600 RR Trent 500, 56,000 x 4 = 224,000
46 TEDSKI : I hope in the future I have the opportunity to fly on one of Virgin Atlantic's A340-600s. I my book I rank Rolls Royce #1 with the best quality reliab
47 BigGiraffe : "Underpowered" is a term from the early days of jet airliners when engine development was young and they could not provide as much thrust as ideally r
48 TEDSKI : In an earlier reply, I stated that the A340 was originally to be powered by a new Superfan version of the IAE V2500. Because of technical risks the Su
49 Dnalor : I would have thought the RB211 would have too large a diameter for ground clearance on a A340? is this subject gonna die*L*
50 TEDSKI : Isn't the new RR Trent 500 based on the RB211?
51 BigGiraffe : How does the weight of an RB211 compare to that of the CFM56? I believe the RB is much heavier. Hauling around the extra engine weight would reduce ea
52 VC-10 : The high thrust is required for T.O. only. I would expect in the crz the thrust settings will be fairly similar and with a more modern engine the sfc
53 TEDSKI : How about adding water injection to the CFM56s so they provide extra power on takeoff? I believe they were used on the P&W J57 turbojets on the US Air
54 BigGiraffe : Isn't the CFM56 more modern than the RB211, so the Specific Fuel Consumption on the CFM should be better? It hadn't dawned on me the increased thrust
55 TEDSKI : You are correct BigGiraffe, early model 747-100s with P&W JT9Ds did have water injection for takeoff.
56 Post contains images Eg777er : I bet that this A340-300 isn't underpowered... It's the AI flying testbed for the Rolls Royce Trent 500.
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