CurbedEnthusiasm

For 9 abreast aircraft (sadly, the 787, and hopefully for a while longer, the 777), a 3x3x3 coach configuration have been the standard - certainly for all new 787 deliveries, and for most 777s since about 2000 (2x5x2 was the first configuration in the 90s). However, why have so few airlines adopted the 3x4x2 configuration for 9 abreast planes? It seems like such a great layout, with pairs for couples, 4-across in the center where everyone is one seat away from the aisle, and only one "double excuse me" with the 3-bench window seat. Any reason why most airlines chose 3x3x3 over 3x4x2?

DenverBrian

Because the seat manufacturers can make 10,000 sets of 3-abreast seats instead of 3,300 sets of 2-abreast, 3,300 sets of 3-abreast, and 3,300 sets of 4-abreast.

IOW: It's cheaper.

skywardhunter

Mass and balance. It'd be aerodynamically inefficient and a safety hazard.
​​​​​​The alternative would be alternating every few rows but that'd make for jigs in the aisles and loss of seats at the switchover points.

It's also visually displeasing. The manufacturing inefficiency could probably be overcome or would be minimal. Also it'd have lots of pax feeling like they "lost" unless the get the set of 2

Loose Cannon

Back in the spring of 1977 when my parents took me on holiday to Greece via ORD and LHR, I remember TWA had its 747 3x4x2 in economy.

CurbedEnthusiasm

I hear you on the safety and aerodynamics, but at least one ANA 777 variant has the 3x4x2 layout.

https://www.seatguru.com/airlines/AN...77-300ER_E.php
http://weekendblitz.com/ana-flight-n...rt-b777-300er/

OskiBear

I seem to recall something similar when I was a kid, flying transpac on 747s.

One time it was a trip with my mom and brother and we had the 3-across row. Another trip it was just mom and I, and we had the section with 2-across.

caverunner17

What are you talking about? The shift of 18" doesn't cause much, if any change in balance due to the weight being close to the CG. Otherwise popular aircraft like the MD80 wouldn't fly due to the 2-3 seating.

In addition, there's no more safety hazard than a 3-4-3 setup

B747-437B

The different types of 3-abreast seats are not interchangeable.

Left aisle, right aisle and center section seats are different part numbers and cannot be swapped. So there really isn't a significant economy of scale due to that.

skywardhunter

It was an opinion, of course it may be wrong.

You're right the arm is quite small, however a significant enough mass even at an 18" arm might have an effect, hence my opinion.

The Safety hazard comes if there is a mass and balance issue and one were to counter by staggering every 5 or 10 rows by going 3-4-2 and then 2-4-3 and now the aisles have jigs in them instead of being straight.

​​​​​one would need to do the math and know the relevant CG figures to know if it causes an actual issue and probably can balance it with a smart aux tank in a wing tip which the aircraft pumps full or empty based on the day's actual load, as the much longer arm would necessitate a much lower mass to counter-balance.

Basically at full load the plane might fly a bit skew if unbalanced is what I'm saying, keyword being "might"

B747-437B

It is no more of an issue than having more passengers seated on the left of an aircraft than on the right. On larger jets like widebodies, this is almost insignificant.

Modern load control programs are very good at calculating CoG and other parameters based on static LOPA and dynamic DCS inputs, including how these change as fuel burns off and how trim should be altered accordingly.

VivoPerLei

FWIW, I was a big fan of the 2-5-2 layout. Can easily accommodate all size parties from 1 to 5. 3-3-3 requires all window seat passengers to disturb two people when getting up whereas that middle seat in the 2-5-2 was probably (guessing) the least occupied of the 9.

mediator

But if you are a solo traveler, and stuck in the middle of the center seat… Oh well…

Sixth Freedom

There are some passenger comfort issues.

Theoretically 3-3-3 offers economy cabin passengers the highest chance of an empty seat next to them. To see why, consider the seat factors that would be required for every passenger to have an empty seat next to them:

3-3-3 = o-o o-o o-o = 6/9 seats occupied = 67%
3-4-2 = o-o o-o- o- = 5/9 seats occupied = 56%
2-5-2 = o- o-o-o o- = 5/9 seats occupied = 56%
2-4-2 = o- o-o- o- = 4/8 seats occupied = 50%
3-4-3 = o-o o-o- o-o = 6/10 seats occupied = 60%

(o = occupied, - = not occupied)

The higher the "empty seat guarantee seat factor", the more likely it is that a passenger will be on such a flight. So 3-3-3 will cause the most passengers possible to have a more comfortable journey.

Now the problem with this approach is that most passengers travel on busy flights and/or that at some stages of the cycle most flights are busy, but that is another story...

pinniped

Yeah, but those flights cruised with a 3-degree lean to the left. It was uncomfortable...

ft101

The different seat sections have different part numbers, but there are multiple parts within these which are common. There would be less of these common parts if there were sets of 4 and 2 as well.