Fuselage diameter vs. drag

[ProPax]

I'm looking at B777 and how airlines are trying to squeeze 10-abreast rows in it. How much would its drag change if its fuselage was, say, 10-20 cm wider? Would an increase like that even be noticeable on the fuel gauge?

[oldchina]

Airlines have been operating 10-abreast for many years. They feel they can get away with it.
10-20 cm is a lot of metal. The real question is what would the airline gain from putting up with the extra weight and drag.

[pattern_is_full]

Frontal area would increase by 6.6% (using the old π*r(adius)^2 formula for the area of a circle, and your 20cm figure).

Wetted area (total fuselage skin area - i.e. friction drag) would increase by the added circumference of the fuselage - 2π(radius). About 100 m^2 additional skin surface to enclose the wider cabin, or 3%

Now, the fuselage drag is only a part of the total drag (parasite drag from other shapes (wings, nacelles), induced drag from lift). So the increase in total drag might be 3-4%. Less at lower speeds (climbs), but significant in high-speed cruise.
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That, of course, leaves aside how much more airlines would have to pay Boeing, per aircraft, to completely revise the jigs and tooling to accomodate differently-sized airframe parts. Including, for example, control runs, floor panels, or a new ceiling (unless you'd accept a 20cm gap down the middle overhead between the carry-on bins ;) ). Do you use the same wings, and increase the span by 20cm? Or shorten the wings 10cm each to maintain the current span? etc. etc.

Thought experiment - you want to increase the size of your house by 20cm in every dimension. How much would it cost to tear out the walls and roof and rebuild them, offset by 20cm? ;)

[TURIN]

Assuming 30 rows in ten abreast on a 777-300, as opposed to 9 abreast, that's an extra 30 seats, or about 3 more rows.

Much easier to either reduce the seat pitch and the leg room, or stretch the aircraft by three rows, whats that, er 3ft per row, so another 9 or 10 feet should do it. 10 feet is 120 inches, assuming standard 20 inch frames thats a stretch of 6 frames?

How much longer than a 777-300 is the 777X?

[tdracer]

How much longer than a 777-300 is the 777X?

It depends on which 777X you're referring to. The 777-8X is actually about 10 ft. shorter than the -300ER, the -9X is about 10 ft. longer (so basically 3 seat rows either way).

The 777X is retaining the same outside fuselage diameter as the original 777, but the fuselage structure is being reworked to add several inches of internal width so 10 across should be a little less painful on the X.

[DaveReidUK]

That, of course, leaves aside how much more airlines would have to pay Boeing, per aircraft, to completely revise the jigs and tooling to accomodate differently-sized airframe parts. Including, for example, control runs, floor panels, or a new ceiling (unless you'd accept a 20cm gap down the middle overhead between the carry-on bins ;) ).

Yes - the best time to increase the cabin diameter of an aircraft is while it's still on the drawing board, cf A350 -> A350XWB. :O

[DuncanDoenitz]

I'm of an age were I can remember those magnificent cutaway drawings in the Eagle boys' paper which dropped through the letterbox every Wednesday. The future would apparently be filled with airliners of increasing size and levels of comfort. Two ubiquitous features on all of these projects, apparently, would be a walk-up bar and a grand piano in the spacious first-class lounge.

In practice, of course, once the airlines get their hands on these airframes, like tract-housing, its just a matter of squeezing as many people into the available space as technology and user-tolerance will permit. If Boeing did make their fuselage 20cm wider (and, by implication, deeper), then the someone, somehow, would find a way to squeeze in a 12th row.

"Recliner on the mezzanine, Sir"?

[tdracer]

I'm of an age were I can remember those magnificent cutaway drawings in the Eagle boys' paper which dropped through the letterbox every Wednesday. The future would apparently be filled with airliners of increasing size and levels of comfort. Two ubiquitous features on all of these projects, apparently, would be a walk-up bar and a grand piano in the spacious first-class lounge.

In the early days of the 747, DC-10, and L1011, the operators couldn't regularly fill the larger aircraft, so they did have first class lounges, walk up bars, and a special light weight piano was designed for the 747 upper deck lounge. However over the following years two, things changed: first, deregulation started taking hold, so airlines could start charging less for ticket, which meant that more people could afford to start flying so load factors went up and they could fill the seats that soon replaced the lounges.

[Checkboard]

The L1011 once had a lounge in the forward cargo hold. With a business jet style door and stairs just forward of the left wing root so that the lounge doubled as a boarding reception area.

https://travelupdate.com/psa-lockheed-tristar-lounge/