I would like to see the spread sheet on all of that monkey motion to fold the wing tip:

(1) How much fuel does it save?
(2) How much does the folding wing tip cost vs. having a hard wing?
(3) How many years do you have to fly it before it starts to make money?
(4) How much additional weight is added to the ZFW for the hinge and all of it’s components?
(5) If the plane is out of service because the wing tip is jammed in the up position how much revenue is lost with the plane on the ground for three days waiting on parts and how many years does it take in fuel savings to make up for three days of lost revenue?
(6) What cost savings would there be if it was just a hard wing with NO hinge and you made accommodations for the extra wing length at your stations?
(7) Can maintenance manually lower the wing tip and lock it into place so you can fly the plane on a MEL?

https://x.com/Turbinetraveler/status/19 ... 9943284096

“The Boeing 777X folding wingtips stand tall at 11.5 feet (3.5 metres) an engineering marvel that lets this beast of a plane fit at any airport gate!”

Q: What is the wingspan for the B777-200LR & B777-300ER?

A: 212 ft 7 in (64.8 m)

Q: What is the wingspan for the B777X with the wing tips extended vs. folded?

A: The Boeing 777X has a wingspan of 235 feet, 5 inches (71.7 meters) when the wingtips are extended. When the wingtips are folded for ground operations, the wingspan reduces to 212 feet, 9 inches (64.85 meters). This folding mechanism allows the 777X to fit into standard airport gates and stands, as many airports are not equipped to handle aircraft with a wingspan greater than 213 feet, the threshold for the larger, more demanding ICAO Class F.

Q: What is the wingspan for the A380?

A: The Airbus A380-800 has a wingspan of 261'8” (79.75 m).

The increased wingspan improves aerodynamic performance.

However, based on discussions I had with my engineering peers while I was on the production line at Everett, the increased wingspan was greater than the production line door opening, necessitating folding tips

Seriously? That sounds crazy to me. My door isn’t wide enough so my solution is folding wingtips? Not “I’ll cut a notch in the door?” Not “I’ll do the final install after roll-out?” Instead I’ll add all of this weight and complexity and cost to the airplane so that it fits through my door?

The original design proposal for the 7X7 that became the 777-200 had a folding wing tip option for clearance at the gate. United, and others, said no thanks because of the complexity. The design has been around for decades. Long wings are more efficient but no one wants to change airport infrastructure to accommodate significant aircraft configuration changes. It is why some aircraft ideas, like flying bodies don’t make it past the proposal stage. Airports infrastructure puts real limits on aircraft design

Old school tech

Seriously? That sounds crazy to me. My door isn’t wide enough so my solution is folding wingtips? Not “I’ll cut a notch in the door?” Not “I’ll do the final install after roll-out?” Instead I’ll add all of this weight and complexity and cost to the airplane so that it fits through my door?

Correct, that would have let the 777-200 use the same gates as the 767, but it added IIRC ~3,600 lbs. to the empty weight, which the airlines saw as 18 fewer paying passengers and they weren't interested. For the 777X, working in carbon, the added weight is only ~900 lbs., for a reduced trip fuel burn of ~3%, and the airlines like that tradeoff a lot better.

I can't find a Boeing source, but Wikipedia says the folded wingtips are worth a 7% efficiency advantage. I believe engine manufacturers are approaching the limit of finding 15-20% savings exclusively from high-bypass turbofan innovation, so Boeing had to find an advantage elsewhere... hence the wing.

Many of you probably know this, but I'll cite the other half of the discussion below.

Page 15 of FAA AC 150/5300-13 (link, screenshot below) describes Airplane Design Groups (ADG) based on tail height and wingspan. EASA has a similar organizational structure either exact matching or within about an inch of each category (king's shoe vs base 10), so generally this table is applicable globally.

Infrastructure is developed around this chart, so if you exceed 214 ft, you have to find a new gate. The 777X wingspan is 235 feet, so airlines could not drop-in replace the 777X for 777 routes (nor can the model be substituted in a AOG event) because the gate infrastructure doesn't match. The folded wing conveniently comes to about 212.7 feet.

Similarly, this is why the 737MAX wingspan is 117.8 feet... it has to fit inside 118 ft to use the same gate as other 737s.

Its not just the gate spacing that becomes an issue, although that is a big issue and would be at every airport the aircraft services.

There are also design clearance issues with taxiways and runways. If they kept the 235 foot wingspan distance, the FAA would have to create a whole new design category for these aircraft, and many major hubs would probably have issues meeting it. Most big airports have been developed to maximize every inch of available space based around their design categories. This is part of the problem the A380 had in service, not many airports could accommodate them.

So does this show that winglets are a hoax and the real performance increase comes from the small wing span extensions that seem to be part of every winglet add on STC.

Let's see a add on winglet kit with NO span extension for a performance comparison.

I think that is proven to be true with the 421 vs 414 winglet STC. The 421 gains 3'-ish wingspan, with a significant performance difference, the 414 gains no wingspan and marginal performance difference.

The winglets work based on slowing flow along the span-length of the wing versus over the wing (think helping to keep the flow closer to perpendicular to the wing face). A longer wing helps but the primary initial purpose of the winglet was span wise flow reduction at high speed where it is more prevalent.