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A340 Long Takeoff roll?

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A340 Long Takeoff roll?

Old 21st Sep 2008, 23:47
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A340 Long Takeoff roll?

Hello A340 drivers, just watched a Lufthansa A340 (the older one with smaller engines) taking off from DFW today... runway 18L, winds about 170/5 and temperature around 32C. It was shocking to see how much runway that aircraft used up, along with a climb rate that looked almost scary. I would say he used close to 10,000ft and what looked like an 800fpm initial climb. Is this normal for this aircraft? I know it was heavy (DFW-FRA) but when I watch similarly laden 777s they use much less runway and climb better.

Thanks,
73
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Old 22nd Sep 2008, 00:19
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Part of the reason is the certification climb criteria:

2-engine transport aircraft, OEI (one engine inop) - min. climb gradient = 3.0%

3-engines, OEI, min. climb gradient = 2.7%

4-engines, OEI, min. climb gradient = 2.4%

I have no doubt that DLH could have climbed out faster, but they religiously use flex thrust to set no more than necessary for a safe TO. This lets engines run cooler & last longer.

It's a matter of running their equipment efficiently and economically.
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Old 22nd Sep 2008, 00:30
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Understood re: flex vs max power. However, when we flex on the 767 with a full load, it is a much quicker takeoff roll/climb rate than the 340. It must have to do with the climb certification you mentioned. But I've been told while awaiting the answer here that the older A330s/A340s with the first generation engines are indeed dogs.


73
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Old 22nd Sep 2008, 01:21
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Part of the reason is the certification climb criteria:

2-engine transport aircraft, OEI (one engine inop) - min. climb gradient = 3.0%

3-engines, OEI, min. climb gradient = 2.7%

4-engines, OEI, min. climb gradient = 2.4%
I think you've got it backwards - 2.4% for 2-engines, 2.7% for 3-engines, and I'm not sure if it's 3.0% for 4-engines
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Old 22nd Sep 2008, 01:34
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I think you've got it right. I found your numbers in "Airplane Design"
By Jan Roskam

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Old 22nd Sep 2008, 02:18
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pssssst Gentlemen...!

2nd segment climb... which iis =
from gear retraction to 400 feet above reference datum...
xxx
2 engine aircraft = 2.4 % gradient
3 engine aircraft = 2.7 % gradient
4 engine aircraft = 3.0 % gradient...
xxx

Happy contrails
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Old 22nd Sep 2008, 03:42
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A330-300: MTOW 213T 2 x Trent 700 at 67,000lbs thrust each.

A340-300: MTOW 275t 4 X CFM 56 at 32,000 thrust each.

A similar thrust/weight ratio in the one engine out case. The 340 doesn't need so much thrust, which is why it's popular with accountants. It's ideal for long lean routes.
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Old 22nd Sep 2008, 04:10
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Greetings,
A340 rate of climb thanks to the earth curvature
 
Old 22nd Sep 2008, 05:06
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The WAT climb requirements end up giving the twin an impressive AEO climb .. the excess grunt is necessary to ensure that, on one, the WAT limit is achievable. The twin loses a far greater proportion of the net grunt than does the quad when one stops making desirable noises ...
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Old 22nd Sep 2008, 05:52
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The joys of Airbus optimized takeoff performance...... They adjust the V2/VS and V1/VR rations to give the most optimum result. Therefore the whole runway will almost always be used. Airlines have the choice to used fixed ratios, but i dont know of any who do........

Mutt
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Old 22nd Sep 2008, 08:28
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Compared to 767, A340 has 100% more engines. Losing an engine on twin leaves you with 50% of the power and losing an engine on quad leaves you with 75% percent. Or to take a look at the second segment climb requirements from the AEO perspective, during normal take-off, twinjet has to develop 100% more thrust than required to maintain required climb gradient (bar odd types with automatic RTO power), while quad needs only 33% more. So while 340s do climb and cruise slower than comparable twins, their performance is quite adequate and safe.

when we flex on the 767
Do B767 FLEX or ATM? It's only semantics question but I'd like to know if A-speak is starting to permeate B-company.
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Old 22nd Sep 2008, 12:26
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Do B767 FLEX or ATM? It's only semantics question but I'd like to know if A-speak is starting to permeate B-company.
Uhh never heard of ATM... we here at AA call it "flex" or "standard" as opposed to max, using assumed temperature, or "derated thrust."
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Old 22nd Sep 2008, 13:14
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ATM = Assumed Temperature Method
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Old 22nd Sep 2008, 13:26
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A340-200 from Dallas will have 4.06% 2nd segment climb rate, which will equate to about 700fpm. b777 will have around 8%.

Mutt
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Old 22nd Sep 2008, 15:47
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Thanks Mutt, now it makes more sense.
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Old 23rd Sep 2008, 00:38
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Reminds me of an old ATC joke that went something like this.

Swissair 340 climbing out of Zurich:-

"Swissair 123 can you confrim you're an A340?"

"affirm Zurich, we are a 340"

"well, could you start the other 2 Engines please?"
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Old 23rd Sep 2008, 16:17
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The bottom line is this; all aircraft, 2, 3, or 4 engines, must meet minimum climb gradients with One Engine Inoperative (OEI). As previous posters have stated, these are 2.4%, 2.7%, and 3.0% respectively. There's not a huge difference between these.

On the day that an engine doesn't fail (99.9999% of the time), the 2 engined aircraft has an EXCESS thrust of 100% above minimum requirements, the 3 engined aircraft has an EXCESS thrust of 50% above minimum requirements, and the 4 engined aircraft has an EXCESS thrust of a mere 33% above minimum requirements

So, if I have an engine failure, I much preferred the times when I flew 4 and 3 engined aircraft. On the 99.9999% of occasions that I don't have an engine failure, I MUCH prefer to be flying an aircraft with a 100% thrust reserve, the twin!

Things like wind shear, Middle East low altitude inversions etc. come to mind...............

Regards,

Old Smokey
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Old 24th Sep 2008, 09:41
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Apparently A340s are so slow they are the only aircraft that get birdstrikes from behind!
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Old 24th Sep 2008, 11:07
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Apparently A340s are so slow they are the only aircraft that get birdstrikes from behind
At least we get them but Boeing only gets the bird droppings on the wings and the body!
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Old 24th Sep 2008, 12:28
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Why do they serve Orange Juice on the Bus?

To prevent Scurvy.
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