A340 v B777

[Espada III]

This is really a question about the differences between a four engines plane and a two engine plane of similar range and passenger capacity.

What are the benefits and disadvantages of each type and why did/does the B777 outsell the A340?

From a laymen's perspective, four engines means reduced risk of accidents at take off, a general ability to continue flying with one engine out and presumably improved take off characteristics at hot and high airfields. So what am I not seeing?

[11Fan]

So what am I not seeing?

On a 777, two less engines. :}

Seriously, there are hundreds of factors, but compare the 777 to the A330 for a better match on sales.

From a laymen's perspective, four engines means reduced risk of accidents at take off, a general ability to continue flying with one engine out and presumably improved take off characteristics at hot and high airfields.

Pretty much summarizes "Four For The Long Haul" campaign. Both have advantages and disadvantages though.


Cheers,
11Fan

[wiggy]

four engines means reduced risk of accidents at take off

Why?

presumably improved take off characteristics at hot and high airfields.

Depends what you mean by "improved", but a twin, on all engines, will have more in hand than a four engined type, hot and high..or anywhere for that matter.

a general ability to continue flying with one engine out

That is true - the four engined aircraft does give you a lot more flexibility in the engine out case.

[Non Zero]

A340 v B777
Costs. Operating a 2 engine costs less than a 4 engine. And by costs you have to consider all of the possible meaning of the word 'cost', not only the one purely related to money (environmental, social etc...) ... (including a percentage of what you are not able to predict with nowadays measurement systems).

four engines means reduced risk of accidents at take off
That's not really the reason why you build a 4 eng plane.
4 units rotating at the same time at the maximum allowed thrust increase the chances of mechanical failure by 50%. There are lots of variable to consider when pieces of heavy metal rotate on the same shaft (gyroscopic, temperature etc...)

Depends what you mean by "improved", but a twin, on all engines, will have more in hand than a four engined type, hot and high..or anywhere for that matter.
Absolutely! The fan blade of a twin eng is at least twice the size of a 4 eng ... and the greater amount of lift is produce by the terminal part of the blade itself.

The real added value is in ETOPs scenario but I would like to see the face of 4 eng jet crew experiencing an eng. failure at 30 west and listen to their decision making process!