Old Oct 30, 04, 10:57 am
  #59  
spotwelder
 
Join Date: Jun 2004
Location: SCL, MCT, LGW and a variety of 1W lounges in between.
Programs: BA Mucci (Seigneur et Ingenieur des Appareils Volants (Gold)), QF (WP and LTG), AA EXP, GF Gold
Posts: 3,929
777ER vs 345

The operating cost debate is rather difficult to sum up in 2, 3 or 4 engines. For example, the 777 usually cruises faster than a 340 so it gets there faster but it has more drag at higher speed so it might burn more, if they were equally efficient in design. Then there is time to climb which depends on wing design and efficient climb power. Then there is fuel lift capability which depends on runway length, atmospheric conditions and excess take-off power for the engine failure case as well as wing volume.

Then you have the cruise flight level. Does the aircraft need to do lots of step climbs as it burns off fuel, like a 747, or can it get straight to the best levels. Then there are the headwinds, if your aircraft route goes into them then the faster aircraft may win.

There are thousands of calculations to do to work out these values for particular city pairs at all times of the year and then dynamic updating throught the flight management system on the actual day.

So 2 large engines against 4 smaller ones is not so simple. If you run out of fuel, ingest volcanic ash or get a load of birds then it simply does not matter. Descent is inevitable as the aircraft cannot reach escape velocity.
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