Tupolev154B2 From United States of America, joined Jun 2000, 1332 posts, RR: 2 Posted (11 years 11 months 2 weeks 5 days 11 hours ago) and read 838 times:
The A345 is stretched from the A343 by a few meters only (3.19 to be specific). What then will give it its superior range? The wings are to be modified only minimally but it will have the new engines. Please answer my question.
White Eagle From Australia, joined May 2001, 47 posts, RR: 0 Reply 1, posted (11 years 11 months 2 weeks 5 days 9 hours ago) and read 797 times:
I think it carries a lot more fuel. 140,000 litres for the 343 versus 205,000 litres for the 345. Also, the wing is a lot larger allowing the plan to fly faster and higher. The higher you fly, the more fuel you save.
Boeing nut From , joined Dec 1969, posts, RR: Reply 5, posted (11 years 11 months 2 weeks 5 days 7 hours ago) and read 755 times:
If it was very clear than this post wouldn't have even started. Don't forget spotter, some poeple want to know these things. Unlike you that has sold their encyclopedia set because you already know everything.
Sndp From Belgium, joined Feb 2000, 553 posts, RR: 2 Reply 6, posted (11 years 11 months 2 weeks 5 days 6 hours ago) and read 748 times:
Because of the new engines the aircraft can take more pay load either in the form of fuel or passangers/cargo. So, the wing is increased and can take a lot more fuel. That is also why the A340 can go a lot futher than the A330. I know it has a centre fuel tank also, but due to the second engine at each side, the bending of the wing is less, which makes it possible to take more fuel in, as I read somewhere. The stupid thing is I cannot remeber how well it was explained when I read it.
Zauberfloete From Austria, joined Nov 2000, 302 posts, RR: 0 Reply 7, posted (11 years 11 months 2 weeks 5 days 3 hours ago) and read 720 times:
The Trent 500´s will have much more power then the CFM56´s, because of that the A345 and A346 will be NOT as fuel efficient as the A342 and A343. They will need much more fuel in cruise off course.
In fact they will be less fuel efficient then a 777.
But that´s not a big problem, because there are other things the market demands from them.
Whats different from the A340-300?
The wing surface of the A343 is 361.1m2, the A346 has 437.3m2 -> that´s an increase of 20.4%.
That provides more fuel capcity and more lift.
But the wingspan increased only from 60.3 to 63.6m, that is an increase of only 5.5%. (it is not practical to have more than 64m wingspan on an aircraft of that size)
That is the reason why the A345 and A346 have a
higher cruise speed. Because due to the new wingdesign, the sweep angle increased from 29.7° to 31.1°, while the aspect ratio decreased by 7.5%.
(the original wing of the A340/A330 offers an uncompareable good characteristic in the slow phases of flight (climb, descent approach, the A340/A330 are in CAT C for approaches, compared to a 767 that is in cat D; so the A340/A330 can do their visual approaches etc. with slower speeds), and is very economic in cruise)
The optimum cruise speed of the A345/6 is therefore about M.83 - M.84 (opt. cruise of A343 is ~M.82), as a direct effect of the new wing design.
The range increased mainly because of the increase in fuel capacity. The fuel capacity of the A340-500 is 50% higher then that of the A340-300, the fuel capacity of the A340-600 is 36% higher then that of the A340-300.
Fuel capacity of A345: 213 120 liters
fuel capacity of A346: 195 620 liters
The wing tank increased from 135270 liter in the A343 to 187220 liter in the A345/6.
Therefore also the mtow increases, with 365t for the A345/6 compared to the 271t of the A343.
The fuselage of the A345 is 3.2m longer then the A343, the fuselage of the A346 is 10.6m longer then the A343.
Both aircraft get a new gear off course, to withstand the new weight. They also have a new horizontal stabilizer and a bigger vertical stabilizer (like the A330-200).
Due to the long fuselage and the mtow, the A340-600 can carry more freight with max. passenger load then any other aircraft. Both aircraft with max. passengers, the A340-600 can carry twice the ammount of add. freight compared to a 747-400.
Why do airlines buy a A340-600?
Beacause it can operate on a hot summer day (or in winter with a snow covered rwy with anti ice on ...) with max. passenger payload and a huge ammount of freight to a ~7000nm destination. A compareable 777-300(X) can not offer the same performance.
The A340-500 and 600 are not as fuel efficient as the A340-300 or the A340-200, but they serve a specific market and they will have success there.
Skystar From Australia, joined Jan 2000, 1363 posts, RR: 3 Reply 8, posted (11 years 11 months 2 weeks 5 days 3 hours ago) and read 711 times:
I honestly don't understand the logic of some when they assert that more powerful engines use less fuel - it's quite simple, you need more fuel to produce more thrust. The amount of fuel you need to produce each pound of thrust may be lower, but that's not the issue.
The Coachman From Australia, joined Apr 2001, 1410 posts, RR: 0 Reply 9, posted (11 years 11 months 2 weeks 5 days 3 hours ago) and read 704 times:
Can someone explain to me why this is so?
My thought process went along the lines of if the maximum thrust of the engine is say "x", then to power the aircraft at the same speed (take for instance 0.83M), the engine could run at a lower percentage of it's maximum output.
Then again, I should look at a car and know that a V8 consumes more generally than a V6...is it the same principle?
Zauberfloete From Austria, joined Nov 2000, 302 posts, RR: 0 Reply 10, posted (11 years 11 months 2 weeks 5 days 2 hours ago) and read 695 times:
An Aircraft need the full power of it´s engines only in rare circumstances.
You need most power during takeoff with mtow and an engine failure.
As you said, in cruise you need far less thrust then max. cont. thrust.
So if you have big engines that can produce a lot of thrust, you carry also a lot of ind. drag.
The bigger the eniges (and their fans etc.) the bigger the induced drag.
An "overpowered" aircraft is therefore less fuel efficient, espescially on long range flights.
The big engines of a twin are somewhat more efficient than the four engines of a quad if you look at the engines itself. But that is lost to some degree because the twin has to have much more thrust for the "1 engine failure after V1 event".
Some people say that an "overpowered" aircraft climbs very fast and therefore it is earlier in cruise and that would be efficient. If you look at a long range flight: both need only a very small part of the flight for climb. (one aircraft maybe 25 min f. its initial climb, the second for example 35 min.), most of the flight both are in cruise (and small step climbs). During climb, the "overpowered" aircraft is little bit more efficient, but in cruise the other aircraft is better (the quad). That means that the longer a flight is, the more efficient is a quad concept compared to a twin concept for an aircraft of similar size.
That is why an A340-200/300 is that fuel effective. An A340 needs for a flight from e.g. Atlanta to Frankfurt 30% less fuel than a DC10-30 (the DC10 is of similar size).
To summarize that:
The A340-500/600 have very strong engines, to fullfill special performance wishes of some airlines (340-380 Paxe, a huge ammount of freight, take off from hot high airfields), but are no world champions regarding their fuel efficiency. They are a special solution for a special market niche.