grbauc wrote:What I see your saying and showing is common sense. You using data points of other models and variants to show a point and make a estimate of a possible range..

Thank you. It is by far the most accurate way providing we don't stray too far from that single data point.

It is far more accurate than a model that has dozens of unknown variables. In these models changing each variable by only 1% can give you an massive 10% change in the final answer.

Another way to double check the result is to look at the fuel burn per hour. The A359 and 789 both burn just under 6000kg of fuel per hour. So if we use very high fuel burn of 7000kg per hour for the 777-8 we can calculate it that way.

The 777-8 can fly 36,500kg of payload 8690nm. At a speed of 490 knots we can add and subtract 490nm and 7000kg of fuel. That gives the following:

36,500kg of payload 8690nm

29,500kg of payload 9180nm

22,500kg of payload 9670nm

So as you can see the 777-8 can nearly carry 300 passengers (30,000kg) the full 9200nm trip distance of Sydney to London. It works out to be approx 290 passengers.

We can do the same calculation for the A350-1000.

It is listed as 366 passengers (36,600kg) over 8400nm. If we assume a low fuel burn of 6000kg and 490knot cruising speed that means.

36,600kg of payload 8400nm

30,600kg of payload 8890nm

24,600kg of payload 9380nm

The A350-1000 can carry approx 260 passengers 9200nm.

So the 777-8 carries 30 more passengers and that is assuming the 777-8 burns 1000kg of more fuel per hour. If they burnt the same fuel per hour then the 777-8 could carry 50 more passengers.

The A350-1000 then needs a MTOW increase of 10T to match the 777-8.