The missions that we look at are modeled with Great Circle Mapper in Figure 1. Great circle distance Helsinki Vantaa to Shanghai Pudong is 4000nm. As we fly the Finnair mission from West to East, where the normal block time is 8.5 hours there is very little wind to calculate with, we have therefore modeled it at 4000nm.
The Vietnam Airlines route, Saigon Ho Chi Minh airport to London Heathrow, we fly in a Westerly direction. The prevailing headwinds on Westerly legs forces us to count with at least 10% longer air distance, we therefore model that we fly 6000nm or a little over 12 hours for this mission.
Figure 2 shows the result. The table is calculated with a fuel cost of $3.00 per US Gallon. Aircraft purchases are done with a horizon of 10-20 years and we assume that $3.00 would be most representative fuel price over such a period.
The differences in efficiency are considerable. Trip mile costs are around 20% higher for Helsinki-Shanghai and 22-25% higher for Saigon-London. The A350 is slightly larger in the cabin than 777-200ER and A340-300. This assumes that the 777-200ER is operated as they are configured today, with economy sections at nine abreast. Should the aircraft’s cabin be refurbished it is likely that an updated economy in a 777-200ER would be installed at 10 abreast as this would make the investment more worthwhile.
As the majority of 777-200ER that fly now, including the ones from Vietnam Airlines, are configured for nine abreast we have used this in our modeling. For the seating we use our proprietary normalized cabin configurations to make all per seat values comparable. We fly with a payload equivalent to a 100% load-factor, that represents a cabin with 75-80% load-factor and the remaining weight to full pax+bags payload being cargo. On a per seat base the differences grow to around 30%, a large figure and a clear motivation to plan for changing to a more modern generation of aircraft for long haul even with fuel at $2.00 per US Gallon.
The background to the large differences in fuel efficiency differs a bit between the aircraft. The problem for A340 is the engines. The A340-300 was forced to use upgraded CFM56-5 when the Superfan project was stopped by Pratt & Whitney. That the CFM56-5 were originally conceived for short-haul can be seen on the low overall pressure ratio of 30. Airframe wetted area, wing aspect ratio and empty weight are all competitive for the aircraft. This is also the background why the sister aircraft, A330, is worth an upgrade to a neo variant. The high fuel burn leads to high takeoff weights, max 275 tonnes, which on a wingarea of 362m2 leads to high wingloading. The consequence is low initial cruise Flight Levels which leads to less efficient mission altitude profiles.
The 777-300ER has rather modern engines in comparison, here modeled with the most popular option, Rolls-Royce Trent 800. They trail the engines of A350 with about 10% in SFC. Here the wing is the problem, it is too stubby. Wing aspect ratio is 13% worse due to lower effective span on a larger wing area. This means the heavier aircraft (both due to higher empty weight but also heavier fuel load for the same payload-range as A350) generates more induced drag (drag due to weight) on long haul missions.
Airlines around the world have started to take delivery of the aircraft that will replace A340-300 and 777-200ER. On long haul distances of eight to 12 hours the savings with these new aircraft are considerable for the dominant cost factor, fuel. The present lower fuel price might give these aircraft another year or so with their airlines, then they will be passed on for their second life with operators which are less sensitive to fuel costs.