Hello everyone,
with interest I had been reading a lot of the posts here.
I thought that most of the people posting here are well trained pilots themselves and therefore I had been waiting for a response regarding the performance of the A340 in regards to other aircrafts and the specialties concerning long haul flights and economy. But I didn’t see a comforting reply. I know the airplane you fly, always is the best in the world.
I would like to explain some of the facts regarding performance of the A340 with my humble knowledge from the flight school in Bremen.
If somebody knows better, please correct me.
Aircraft Performance can have a lot of different aspects. Like in the Olympics there
are sprinters, weight lifters, jumpers and long distance runners among aircrafts.
Top performers in a specific quality often lack behind in all the others.
The A340 is a slow aircraft and a airwayblocker..
That is not true. Design Cruise speed is M 0.82 and the plane is mostly flown at .83 ( flying at .84 is 6% more fuel consumption ).
design cruise for the 747 is also .83, but due to the conventional wing design the affects of flying faster do not matter so much in fuel consumption.
mostly the 747 is operated at .86.
Flying M.01 slower you are loosing 45 seconds per hour. That means on a flight to New York from Europe that will be around 8x3x45 seconds or 18 minutes.
It is different with the A340-600, which flies faster and doesn´t has the fuel penalties from the A340-300. the A346 is flying usually with .84 and the fuel saving is on a 13h flight tremendous.
747-400 - A346 .86 - .83 27t fuel -27minutes
747-400 - A346 .86 - .84 23t fuel - 23min.
same payload, same wind conditions etc..
would like to know, how the 777-300 ER is doing ?
The A340 is not climbing and slow during the climbout The A340 is due to his wing design a slow climber, also there is the possibility of a derated climb.
The A 340 has a supercritical airfoil, which provides low drag at the design Mach
number of .82, without using too much wing sweep. The benefits are a high available
fuel volume, structural efficiency and good slow flying characteristics. However at
higher speeds the shock wave will move forward and the wave drag will increase
drastically. The wings of the A 340 also have a comparably long span, a large area and a very
shallow sweep angle.
A340-300 29,7; 747-400 37,5; B777 31,5 degrees sweep
The long span, and therefore the high aspect ratio reduce the induced drag, which is
especially beneficial at low speeds and high altitudes.
The aspect ratio of the A340-300 is at around 10,1; B747-400 is at 7,7; B777 is at 8,7
"An A 340 with the wing and technology of the B 747-400 would require
39 000 lbs thrust engines in order to take off with 257 to, whereas only 31 200 lbs
thrust engines are required with the A 340-200 efficient wing". ( Airbus statement )
The A340 and A330 have the option of a derated Climb which is normally used in my company I work for. This is not the same as a derated Take-Off! It takes a little more fuel because you need a longer time in lower levels, but you reduce the EGT’s significantly and that saves engine overhaul and reduces the risk of an engine failure.
But if you are heavy you have to fly faster anyhow then 250 knots and a normal climb out speed will be around 270kt-280kt.
With MTOW the A340 will reach initially FL330, I heard the 747 can only do 290 initially, is this correct?
Why aren’t there stronger engines on the A340 ?
Power considerations for an aircraft depend upon the operation at the highest power
demand. For a twin the one engine out case at MTOW sets the lowest possible limit. The thrust loss is 50% compared to 25% on a quad.
Therefore a twin has greater all engine thrust and better all engine climb rates. But the net climb gradient for 4 engine aircraft is also higher ( 3 ) compared with 2- engine aircraft ( 2,4 ).
The A 340 provides enough power for
takeoff as well as to reach the OPT/MAX FL with 300 ft/min residual rate of climb.
I have to admit the thrust to weight ratio is not the best and I love to have surplus power, but under the economic and environmental point of view, it is better to fly an A340 on the long routes and up to about 8 hours an A330.( or not to fly )
I suggest fly around the A340 if you are faster, just like you do on the ski slopes and if you climb better, just pass above.
But do not forget:
the airplane with the longer routing has the right of way.
always happy landings