2-4-2 is the way to go. Not luxurious 2-4-2 but 17.2" seat and narrower aisle 2-4-2. It's about 10" wider than the 767, which still allows a non-cramped 2-2-2 J or domestic F (vs a cramped 2-2-2 J or 2-1-2 F) and a 1-1-1 lie flat product.
Totally agree. 8 17.2" seats, 11 2" armrests, and 2 18' aisles = 195.6in. Call it 196in but maybe 194/195in with 17in aisles.
If it's a circular fuse and Boeing can use the 777X's 4in sidewalls at the critical points, that's a 204in fuselage. Call it 208in just to be safe (6in sidewalls and 18in aisles).
At 208in, diameter and wetted area per seat for Y cabin is equal to the A320's upper bubble ( 8/6 * 156in); total wetted area is less including A320's belly bulge.
Compared to A300/330/340, same Y seats abreast for 6.3% less wetted area (8.1% less if 204in diameter).
So basically there's extremely little - if any - wetted area penalty for a feasible 8ab circle measured against A320. More if measured against 737. Seat width is smaller than A320 but I'd trade 2-4-2 and an inch of width against 3-3. Most probably would. In addition to the seated experience, the boarding/deplaning process would be better for pax and airlines.
For the smallest family member at around A321 capacity (240 seats at 28in pitch), minimum parallel cabin length would be ~71ft (assuming non-parallel portions contain only lavs/galleys, +1ft for exits).
In fact you'd squeeze 3-4 rows at 7ab into the tapering sections, especially aft where the taper is more gradual. That would mean A321-scaled capacity is ~261-268 seats.
So the smallest member would sit ~8-12% above A321 capacity - about where it should be.
Assuming nose- and tail-cone fineness ratio of 1.6 (standard) and 2 respectively, total fuse length would be ~133ft. Fuse fineness ratio would be 7.7 - low but not fatal.
One of the biggest drawbacks of stubby fuselages is lower moment arm for the empennage. For this generation of aircraft, however, with lower weights and thrust levels, empennage will be significantly smaller (plus advances in FBW allowing smaller control margins).
A310's rudder, for example, handled up to 58k thrust per engine. Here we won't go much over 40k. MTOW will be much, much lower (less wing lift = less HTP lift = smaller HTP).
The possibility of using the 789's HLF tech for the rudder further reduces the concern about empennage size (this was seen as a wash for 779, which has proportionately less rudder impact due to much longer moment arm).
So it seems clear that a small twin-aisle can be as efficicient as the A320 even before we get to the weight savings of a stubby tube versus a long narrow one, CFRP/NewMetal vs. old metal.
That's what the airlines are probably learning via Boeing's presentations.
An 8ab circle would lose LD3 ability, but LD3-45's are doable and we've already seen plans to use even MAX-8's extensively on TATL. So I don't think cargo is going to tip this picture, especially with an inevitable trend of declining yields as cargo prices approach the marginal cost of filling the world's burgeoning belly capacity (i.e. very low).
And that's just for the smallest family member of A321 plus ~10% size. The next-largest member at ~753/762 size is even more optimal.
I have no idea whether an oval would be better than the above-sketched 8ab circle - whether 7ab or 8ab. It doesn't need to be better IMJ; if it is that's just gravy.
I never bought the line that it HAD to be priced at ~$70mil.
A plane's value proposition is the sum of its life-cycle costs and revenues. Boeing can change the price at which its products sell by making them more or less fuel- or otherwise efficient.
The idea of a fixed $70mil cost was a bit like airlines saying it had to be CFRP - maybe it does but let Boeing figure that out.
Likewise, let Boeing figure out at what airline cost in capital it can offer airline savings on fuel and other expenses, explain the numbers to airlines, and see what sells.
We're now hearing that $80mil could be the price target; we may see a higher willingness to pay - especially for the larger version(s).
IMO a baseline at ~A321+10% size and a stretch at ~753/762 size - both with MOM range - could be followed by a further stretch approaching A332 size with only transcon range. That kind of plane could end up dominating domestic/regional trunk routes - no small market.
What's the business case for Boeing? Say they'll spend $15bil and want 20% annual ROI at production maturity - $3bil profit per year.
If they build 200/year, they'd need $15mil/plane. If the plane sells at $80mil, that's 19% profit margin. Doable...
Still you have to be aggressive to close that business case, especially given the risks inherent in airliner programs and especially given 787 PTSD.
Maybe 20% ROI is too low a minimum. At 30% it's harder to see.
I think everyone looking at this seriously sees it would be a great plane for airlines and would yield serious production profit for Boeing.
The only open question seems to be whether there's a sufficient ROI for a big new program.
I hope they launch but can't say for certain I'd bet my job on it were I in the nice offices in Chicago.