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Topic: 77X - Folding Wingtip
Username: frmrCapCadet
Posted 2012-11-06 08:24:32 and read 3574 times.

http://seattletimes.com/html/businesstechnology/2019614451_777x06.html

This morning Seattle Times has a longer article on why a 777X will offer a folding wingtip, also quotes Clark as liking the idea, also believes that this plane will be offered. There is a fairly extensive discussion of Class E and F airplanes.

Question to engineers, the WWII carrier planes of my youth had folding wings, but they folded fairly close in. A 10 foot folding wing tip seems to be a different sort of thing, plane wings have a lot of moving parts that fold in, up, out down etc. How big a deal is it to fold the outer 10 feet of a 233 foot wing span?

[Edited 2012-11-06 08:30:59]

[Edited 2012-11-06 08:32:06]

Topic: RE: 77X - Folding Wingtip
Username: Stitch
Posted 2012-11-06 08:32:47 and read 3585 times.

When Boeing dropped the folding wingtips for the 777-200/777-300, that allowed Boeing to extend the wing fuel tanks to increase range.

Assuming a 72m wing, being able to raise the outer 3m of each would keep it within the 65m limit and would allow Boeing's new wing to have the same tank lengths as the current 777.

Topic: RE: 77X - Folding Wingtip
Username: iFlyLOTs
Posted 2012-11-06 08:33:53 and read 3585 times.

I think that this was also offered on the earlier 777 versions, American wanted them so that they could get the planes into the same gates as the DC-10, but I don't think there were any takers though..

Topic: RE: 77X - Folding Wingtip
Username: Roseflyer
Posted 2012-11-06 09:07:38 and read 3591 times.

Quoting frmrCapCadet (Thread starter):

Question to engineers, the WWII carrier planes of my youth had folding wings, but they folded fairly close in. A 10 foot folding wing tip seems to be a different sort of thing, plane wings have a lot of moving parts that fold in, up, out down etc. How big a deal is it to fold the outer 10 feet of a 233 foot wing span?

The outer 10ft is relatively simple. There’s no flight controls actuation, which makes the design relatively simple. The original 777 folding wing was 21 feet and that created problems with the leading edge slats and outboard aileron. Folding hydraulic plumbing, and all the components necessary for actuation was quite difficult.

All that a 10ft section would require is an upsized ground spoiler actuator. It would be two position and have a locking mechanism in the down position. You also have to have indication and control in the flight deck, but again it isn’t that difficult compared to having to fold your aileron and a slat which would be very heavy and complex.

Topic: RE: 77X - Folding Wingtip
Username: Aesma
Posted 2012-11-06 09:24:23 and read 3585 times.

Wouldn't that weigh a lot ?

Topic: RE: 77X - Folding Wingtip
Username: Stitch
Posted 2012-11-06 10:27:09 and read 3586 times.

Quoting iFlyLOTs (Reply 2):
I think that this was also offered on the earlier 777 versions...

Yes it was, but no airline took it up so Boeing designed it out when they developed the 777-200ER / 777-300.



Quoting iFlyLOTs (Reply 2):
Wouldn't that weigh a lot?

I would not be surprised if Boeing used the "scimitar tip" style found on the 787 for the folding bit as they don't have any control surfaces. So the weight and complexity could very well be minimal.

[Edited 2012-11-06 10:29:03]

Topic: RE: 77X - Folding Wingtip
Username: Aesma
Posted 2012-11-06 10:30:05 and read 3584 times.

Well if they're folding they need a folding mechanism, that's what I was wondering about.

Topic: RE: 77X - Folding Wingtip
Username: cosmofly
Posted 2012-11-06 10:46:14 and read 3588 times.

From the picture in the link, it looks B is also changing the angle of sweep.


The folding wing tecnology actually could be a major advantage in the next gen narrow body where an ultra efficient wing span is required to still fit into a 737 gate. Major differentiator will be necessary in the upcoming cut throat market with C919 and MS21 using the latest avionics and engines, but listing at half the price of A and B.

Topic: RE: 77X - Folding Wingtip
Username: Stitch
Posted 2012-11-06 10:52:01 and read 3585 times.

Quoting Aesma (Reply 6):
Well if they're folding they need a folding mechanism, that's what I was wondering about.

Clearly there will be a trade-off, , but that mechanism would likely not be supporting much weight so that should help with how heavy the mechanism needs to be.

[Edited 2012-11-06 10:53:32]

Topic: RE: 77X - Folding Wingtip
Username: JAAlbert
Posted 2012-11-06 11:28:37 and read 3586 times.

I have always read on this site that folding wingtips equal unacceptably higher weight. So what, if anything, has changed?

From the article, it looks like the wings will be a bit longer and the engines places a bit farther out on the wings. What is the benefit of having a longer wing? The article mentions fuel savings, but how does the wing length increase fuel savings?

Topic: RE: 77X - Folding Wingtip
Username: Roseflyer
Posted 2012-11-06 11:48:37 and read 3591 times.

Quoting JAAlbert (Reply 9):
From the article, it looks like the wings will be a bit longer and the engines places a bit farther out on the wings. What is the benefit of having a longer wing? The article mentions fuel savings, but how does the wing length increase fuel savings?

Here's the coefficient of drag equation:

Drag= K + [2* Lift/(Density * Area * Speed^2)]^2 / ( Pi * e * Aspect Ratio)

K = zero lift drag coefficient
e = efficiency coefficient

In simple terms, Aspect ratio is in the denominator, which means a larger aspect ratio means lower drag. Aspect ratio is the wingspan squared over the area of the wing.

In even simpler terms, the longer the wing, the less drag created.

Quoting JAAlbert (Reply 9):
I have always read on this site that folding wingtips equal unacceptably higher weight. So what, if anything, has changed?

Folding wing means more weight, which means more drag. If the greater wingspan lowers the drag enough to counteract the higher weight, then you have a business case supporting a folding wing tip. It all comes down to math, and Boeing has plenty of PhD level aerodynamics engineers to do the math. The constraint of wingspan and gate/taxi clearance is what helps force them into a trade between short span, winglet or folding wing tip.

Topic: RE: 77X - Folding Wingtip
Username: LLA001
Posted 2012-11-06 11:49:41 and read 3588 times.

I don't know how much will it cost, or how feasible it is, but it will be cool to see something like that at the airports. Since all the aircraft begin to look like each other, it will be good to see something different for once.

Topic: RE: 77X - Folding Wingtip
Username: scbriml
Posted 2012-11-06 11:54:12 and read 3590 times.

Quoting Aesma (Reply 4):
Wouldn't that weigh a lot ?

No, they could make it all out of CFRP, that always comes in lighter than Aluminium.   

Topic: RE: 77X - Folding Wingtip
Username: sweair
Posted 2012-11-06 12:03:47 and read 3586 times.

Quoting scbriml (Reply 12):
No, they could make it all out of CFRP, that always comes in lighter than Aluminium.

Yeah CFRP in the F35 sure beats the F35 in plain old aluminium. The current gen CFRP is not the most ideal, coming gen2 that the JSF uses is another thing. I wonder if 777-X is too soon to realise this tech though. I guess B wants to go a notch above 787s gen of CFRP if possible, and out of autoclave hardening is useful as well, saving time, but the 777 will never be produced in the numbers that the 787 is, still it could save time and money.

Folding wingtips work, look at the F18/F14 etc You cant get more punishment than in a naval fighter, never heard that a wingtip failed.

If it works out, I could see Airbus follow in Boeing's foot steps, a great way of making your mega wing fit in a code E space.

Topic: RE: 77X - Folding Wingtip
Username: Aesma
Posted 2012-11-06 12:08:35 and read 3587 times.

Quoting scbriml (Reply 12):
No, they could make it all out of CFRP, that always comes in lighter than Aluminium.

:D

Wouldn't adding weight so far out also mean more structure for the entire wing ?

Topic: RE: 77X - Folding Wingtip
Username: ferpe
Posted 2012-11-06 13:30:23 and read 3584 times.

Quoting Aesma (Reply 14):
Wouldn't adding weight so far out also mean more structure for the entire wing ?

A weight lump far out on the wing is relieving wing bending moment, ie if well done it does not cost any heftier wing inside of the mechanism. For a CFRP raked tip the mechanism should be reasonable both in complexity and weight. The locking mechanism better be fool proof however  , can see the headline photos from the first tip that goes beating  Wow! .

Topic: RE: 77X - Folding Wingtip
Username: Roseflyer
Posted 2012-11-06 14:19:58 and read 3582 times.

Quoting ferpe (Reply 15):
The locking mechanism better be fool proof however  , can see the headline photos from the first tip that goes beating   .

Ailerons elevators and rudders are not frequently falling off airplanes so a 10ft section of wing with a two position actuator should not be too complicated. Ailerons are far more complex.

Topic: RE: 77X - Folding Wingtip
Username: Viscount724
Posted 2012-11-06 15:41:28 and read 3585 times.

Quoting LLA001 (Reply 11):
I don't know how much will it cost, or how feasible it is,

It's feasible because it was offered on the 777 originally, but no customers were interested, no doubt due to concerns re the complexity and related maintenance issues, as well as the weight. I doubt anything has changed since Boeing dropped the idea.

Topic: RE: 77X - Folding Wingtip
Username: Roseflyer
Posted 2012-11-06 15:47:04 and read 3585 times.

Quoting Viscount724 (Reply 17):

It's feasible because it was offered on the 777 originally, but no customers were interested, no doubt due to concerns re the complexity and related maintenance issues, as well as the weight. I doubt anything has changed since Boeing dropped the idea.

The Seattle Times article points out that it has changed. The original design was a 21 ft section that would fold which included the aileron and slat. This proposal is 10ft which does not include the aileron or slat, so that's a big difference in complexity and weight.

Topic: RE: 77X - Folding Wingtip
Username: EPA001
Posted 2012-11-06 16:00:12 and read 3585 times.

Quoting Roseflyer (Reply 18):
This proposal is 10ft which does not include the aileron or slat, so that's a big difference in complexity and weight.

Sounds like a smart move. We could see this feature maybe with other airliners in the future as well. In this way it sounds more like easy money, meaning an efficiency gain which is not too heavy or too complex.

Topic: RE: 77X - Folding Wingtip
Username: Viscount724
Posted 2012-11-06 16:05:22 and read 3589 times.

Quoting Roseflyer (Reply 18):
This proposal is 10ft which does not include the aileron or slat, so that's a big difference in complexity and weight.

Anything that moves adds complexity. It's just one more thing to malfunction and cause delays and cancellations.

Topic: RE: 77X - Folding Wingtip
Username: Stitch
Posted 2012-11-06 16:44:22 and read 3587 times.

Quoting Viscount724 (Reply 20):
Anything that moves adds complexity. It's just one more thing to malfunction and cause delays and cancellations.

True, but Boeing has a fair bit of experience with such things from their Naval Aviation programs and this should reduce risk.

Topic: RE: 77X - Folding Wingtip
Username: strfyr51
Posted 2012-11-06 17:41:39 and read 3589 times.

with a 233'10" wingspan for the 777X a folding wing Might NOT be a half bad Idea if trying to use them domestically as well as International Service I've seen rumours of as much as 242' 8". With a fly By Wire airplane a folding wing is pretty much a Moot point except for where they place the folding actuator and the hinge Locking device .

Topic: RE: 77X - Folding Wingtip
Username: Roseflyer
Posted 2012-11-07 09:09:35 and read 3585 times.

Quoting Viscount724 (Reply 20):
Quoting Roseflyer (Reply 18):
This proposal is 10ft which does not include the aileron or slat, so that's a big difference in complexity and weight.

Anything that moves adds complexity. It's just one more thing to malfunction and cause delays and cancellations.

That’s true, but Boeing has plenty of experience making parts of the wing move. A folding wing tip is about the complexity of a ground spoiler. I think many people hear folding wing and immediately think it is very heavy and complex, when in reality if you only fold the tip outboard of the slats and aileron, it isn’t that complicated. It’s essentially one giant load bearing spoiler. It also would likely be able to be locked in the down position for airlines that don’t need the folding option and also it should be able to be locked out and deferred if the actuator fails which would prevent cancellations.

Topic: RE: 77X - Folding Wingtip
Username: OldAeroGuy
Posted 2012-11-07 16:38:27 and read 3580 times.

Quoting Roseflyer (Reply 23):
A folding wing tip is about the complexity of a ground spoiler.

Or a landing gear door.

Topic: RE: 77X - Folding Wingtip
Username: Mike89406
Posted 2012-11-07 16:53:24 and read 3948 times.

I used to work on Navy jets and they are designed to park more aircraft on the flight deck/hangar bay. The biggest problems are MX. Since they require actuators, linkages etc... it does increase maintenance hours due to added flight control mechanisms etc...

One of the biggest problems are when the wings fail to lock then you have to op-check and replace components and downing planes. Actually that's common with any movable flight control/surface.

Sometimes line or ramp workers have been known to damage outer wings by collisions in to other aircraft.

Topic: RE: 77X - Folding Wingtip
Username: Stitch
Posted 2012-11-07 19:01:25 and read 3897 times.

Quoting Mike89406 (Reply 25):
The biggest problems are MX. Since they require actuators, linkages etc... it does increase maintenance hours due to added flight control mechanisms etc...

Which is why I am of the opinion that the 777-X's folding wingtips will not include any control surfaces.

Topic: RE: 77X - Folding Wingtip
Username: JoeCanuck
Posted 2012-11-07 20:55:35 and read 4061 times.

Quoting Stitch (Reply 26):
Which is why I am of the opinion that the 777-X's folding wingtips will not include any control surfaces.

The 737ng doesn't overly suffer from having the ailerons a significant distance from the wing tip. With 2 sets of ailerons and the addition of spoilers to help out, a few meters of control free wing at the tip really shouldn't cause much of a problem, control wise.

Topic: RE: 77X - Folding Wingtip
Username: Roseflyer
Posted 2012-11-07 21:38:23 and read 4046 times.

Quoting JoeCanuck (Reply 27):
The 737ng doesn't overly suffer from having the ailerons a significant distance from the wing tip. With 2 sets of ailerons and the addition of spoilers to help out, a few meters of control free wing at the tip really shouldn't cause much of a problem, control wise.

The 737NG has its aileron further inboard than other airplanes because the forces using manual reversion would be too high if it was further outboard without proper balance weights. If Boeing could, they'd push the aileron further outboard which allows for additional flap span which improves short field performance.

Topic: RE: 77X - Folding Wingtip
Username: scbriml
Posted 2012-11-07 22:29:42 and read 4029 times.

Quoting sweair (Reply 13):
You cant get more punishment than in a naval fighter, never heard that a wingtip failed.

But that strength typically come at the cost of weight. Adding more mechanical devices to the wing will also increase maintenance - probably only a very small percentage, but it's more stuff that needs to be checked and will fail.

Topic: RE: 77X - Folding Wingtip
Username: JoeCanuck
Posted 2012-11-07 23:18:26 and read 4030 times.

Quoting Roseflyer (Reply 28):

The 737NG has its aileron further inboard than other airplanes because the forces using manual reversion would be too high if it was further outboard without proper balance weights. If Boeing could, they'd push the aileron further outboard which allows for additional flap span which improves short field performance.

I didn't actually know the specifics on the 737 but the upshot is an inboard from the wingtip aileron isn't necessarily detrimental to roll control.

My point is the 777 has plenty of roll mechanisms and a few meters of extra uncontrolled outboard wingtip really shouldn't be a big deal for roll control. I'm guessing a significant portion of that extra span will be some spiffy upswept shape that wouldn't have any control surfaces anyway.

Topic: RE: 77X - Folding Wingtip
Username: Wisdom
Posted 2012-11-08 12:30:52 and read 3970 times.

I think that it's not a good idea.

The safeguards needed, and the actuating mechanism would add massive weight of several hundreds of kg.
The additional fuel needed to carry around this added weight would result in a massive additional cost in the millions, over the lifespan of an aircraft.
In addition, a folded wing is very complex for flexible wings as found on civil airliners. It splits the wing in 2 pieces, as you can never make it a continuous piece of airfoil. Sure military jets have folding wings, but their wings are very stiff and they don't flex like airliner wings. The flex is largest at the tip, where the torque is largest.

Did I mention the risk of the wing folding inflight or malfunctioning actuating/guiding mechanisms piercing into the wing/wing tanks?

It would just be much easier, efficient and economic to draw a few lines of fresh paint on the tarmac.
Airports are made to accommodate aircraft and not the other way around.

Topic: RE: 77X - Folding Wingtip
Username: JoeCanuck
Posted 2012-11-08 12:45:14 and read 3973 times.

Quoting Wisdom (Reply 31):
Did I mention the risk of the wing folding inflight or malfunctioning actuating/guiding mechanisms piercing into the wing/wing tanks?

The modern aircraft wing has many, many moving parts already and they are very reliable. The gear has a folding, locking mechanism which is also pretty reliable. Once it's locked, it pretty much stays locked.

The wing won't be under any flight stresses when it is extended. The flex of the wing may even help by reducing shock loads under stress.

I really don't think Boeing would have ever proposed the concept if they hadn't worked out the variables.

Topic: RE: 77X - Folding Wingtip
Username: Roseflyer
Posted 2012-11-08 13:44:30 and read 3953 times.

Quoting Wisdom (Reply 31):
The safeguards needed, and the actuating mechanism would add massive weight of several hundreds of kg.

I’m not sure how much it would weigh, but an actuator that size is about 75lbs. The support structure and hydraulic plumbing doubles that weight. I’d assume maybe 150lbs per wing. That’s about the weight of a winglet.

Quoting Wisdom (Reply 31):
Did I mention the risk of the wing folding inflight or malfunctioning actuating/guiding mechanisms piercing into the wing/wing tanks?

I don’t really see that as a huge problem. The flaps already retract into the wing. There are spoiler panels above the fuel tank. There’s the ailerons. I think it is important to realize it is a folding wing tip, and not a folding wing. Also, a lockout mechanism to keep it down isn’t that overly difficult. The inboard aileron is locked out in flight for example.

Topic: RE: 77X - Folding Wingtip
Username: tdscanuck
Posted 2012-11-08 15:10:24 and read 3952 times.

Quoting Wisdom (Reply 31):
The safeguards needed, and the actuating mechanism would add massive weight of several hundreds of kg.

Flaps are far more complex and highly loaded than the proposed tips, and even they don't have several hundred kg of actuation mechanism. This is an area where sizing and weight estimates are pretty mature.

Quoting Wisdom (Reply 31):
It splits the wing in 2 pieces, as you can never make it a continuous piece of airfoil.

Sure you can...on each side of the hinge you have the hinge attachment. That means the wing is really stiff right around the hinge, so you can get continuity. You have a *stiffness* discontinuity in the wing but the airfoil doesn't care about that.

Quoting Wisdom (Reply 31):
The flex is largest at the tip, where the torque is largest.

The torque is largest at the wing-to-body joint. The *displacement* is largest at the tip. But displacement doesn't imply stress or load, it's the result of integrating the very high torque at the inboard wing outwards to the tips.

Quoting Wisdom (Reply 31):
Did I mention the risk of the wing folding inflight or malfunctioning actuating/guiding mechanisms piercing into the wing/wing tanks?

The risk of the former is comparable to the risk of losing all the fuel out of one side, which is the usual aileron sizing criteria. It's within the existing roll authority capability. The risk of the later is exactly analogous to slat tracks (which actually do go inside the wing tanks)...this is how a 737 burned to the ground in Japan several years ago. Not to say it's not a risk, but it's a risk the industry is well acquainted with.

Quoting Wisdom (Reply 31):
It would just be much easier, efficient and economic to draw a few lines of fresh paint on the tarmac.
Airports are made to accommodate aircraft and not the other way around.

The 727 had triple-slotted flaps and an airstair because it was designed to operate from airports built in the turboprop age. Several airports can't operate simultaneous approaches for widebodies because their parallel runways are too close together (they're at the narrowbody limit). The 767 has kinked main landing gear to handle the load-bearing capability of the piers at La Guardia. The 737NG and MAX won't materially increase span because they need to fit into "737-sized" gates. The A380 is stuck with 80m span (even though pure aerodynamics would suggest more) because that's the largest even a max-size airport will reliably handle. The 777 has three MLG axles because it would exceed the pavement loading of the airports if it had two.

Aircraft are always made to accommodate airports, not the other way around.

Tom.

Topic: RE: 77X - Folding Wingtip
Username: kanban
Posted 2012-11-08 18:10:59 and read 3924 times.

how high is the wing tip from the ground? everybody seems to be talking about the wing tip folding up, what if it folded down? Gravity would drop it and some snubbers would slow the decent. then find a lift weight method of lifting it back before flight.. like a electrically powered small drum and cable.

Topic: RE: 77X - Folding Wingtip
Username: Stitch
Posted 2012-11-08 18:24:22 and read 3926 times.

Quoting kanban (Reply 35):
how high is the wing tip from the ground?

For the 777-300ER, the wing tip is between 24 and 26 feet (7.29-7.90m) off the ground.

Topic: RE: 77X - Folding Wingtip
Username: kngkyle
Posted 2012-11-08 18:51:36 and read 3899 times.

I hope they do it, just for the sake of it being something new and interesting, like the 747 hump.

Topic: RE: 77X - Folding Wingtip
Username: kanban
Posted 2012-11-08 22:39:32 and read 3886 times.

Quoting Stitch (Reply 36):
For the 777-300ER, the wing tip is between 24 and 26 feet (7.29-7.90m) off the ground.

so if it dropped instead of being raised vertically, there would still be 14-16 foot clearance.. hmmmmm!

Topic: RE: 77X - Folding Wingtip
Username: JoeCanuck
Posted 2012-11-08 23:39:59 and read 3885 times.

Quoting kanban (Reply 38):
so if it dropped instead of being raised vertically, there would still be 14-16 foot clearance.. hmmmmm!

Almost exactly the right height to get bashed by service vehicles whose drivers are too lazy to look up.

[Edited 2012-11-08 23:40:30]

Topic: RE: 77X - Folding Wingtip
Username: KC135Hydraulics
Posted 2012-11-08 23:56:31 and read 3887 times.

Quoting JoeCanuck (Reply 32):
The modern aircraft wing has many, many moving parts already and they are very reliable. The gear has a folding, locking mechanism which is also pretty reliable. Once it's locked, it pretty much stays locked.

So much so that I once observed crew chiefs having to beat on a stuck NLG on a KC-135 with a wheel chock (a BIG one)to get it to unlock during troubleshooting. Once it's up, it's up and it's not going anywhere unless everything works perfectly. I would imagine a few relatively simple but high strength downlocks can be installed to hold a few feet of wing down and locked without much hassle.

Topic: RE: 77X - Folding Wingtip
Username: rheinwaldner
Posted 2012-11-09 05:42:24 and read 3852 times.

Quoting tdscanuck (Reply 34):
Aircraft are always made to accommodate airports, not the other way around.

Often maybe but not always.

- The 767 replacement won't fit into 767 gates anymore.

- The design of the 747 and the A380 did not respect the available space at the airports when they were launched.

These two examples are 1:1 applicable to the situation the 77X faces and the context of Wisdom's post. Other than most of your examples.

---

These plans are taken far too lightheartedly IMO. It may not be so risky and also not add too much additional weight. But it still is a significant divergence from usual methods and no matter what there will be a penalty for the 77X's bottomline. The internal and external competition of the 77X (781HGW and A350) won't suffer from that penalty at all.

When we recently judged the effort to create the 77X vs the effort to create a 787-based A351 competitor, hardly anybody did take into account this complexity-and-weight adding feature of the 77X. As if a completely new wing including a material paradigm shift would not be enough. Though, could the 77X's composite wing later be used for Y3?

Anyway, folding wingtips carry a slight tone of desperation IMO...

Topic: RE: 77X - Folding Wingtip
Username: tdscanuck
Posted 2012-11-09 06:18:03 and read 3845 times.

Quoting rheinwaldner (Reply 41):
But it still is a significant divergence from usual methods and no matter what there will be a penalty for the 77X's bottomline.

It's not a penalty, it's a trade. In return for the extra weight/cost/maintenance, you get better fuel burn. That return has to come out positive, obviously, otherwise they wouldn't do it, and the magnitude of the trade probably depends on your route structure and payloads. This is exactly the same type of "penalty" as winglets and we see how that worked out.

Quoting rheinwaldner (Reply 41):
When we recently judged the effort to create the 77X vs the effort to create a 787-based A351 competitor, hardly anybody did take into account this complexity-and-weight adding feature of the 77X.

Given that they designed a far more difficult folding wingtip for pretty much the same wing about 20 years ago, the risk is abnormally low. Although I agree it probably wasn't taken into account by a.net's armchair designers, I think the delta of taking it into account is much smaller than you think.

Quoting rheinwaldner (Reply 41):
Anyway, folding wingtips carry a slight tone of desperation IMO...

How so? They're a good and proven solution to a particular problem: how do I get the span I want in flight when that span won't fit in my gate?

Tom.

Topic: RE: 77X - Folding Wingtip
Username: BigJKU
Posted 2012-11-09 07:00:10 and read 3839 times.

Quoting rheinwaldner (Reply 41):
Anyway, folding wingtips carry a slight tone of desperation IMO...

I think that is just silly. It is one thing to build the 747 or A380 that won't fit into gate dimensions as they exist at that time. There just never were going to be that many of them so it won't be a huge deal for airports to adapt a few gates for them. The 777 on the other hand sells at a greater pace than the smaller A330 does. There are lots and lots of airlines operating out of fairly space constricted airports with large numbers of 777's.

Those airports are not Dubai. They don't have unlimited funds and space to add to airports. What will determine if the 777x can survive in the face of the A350 is really its ability to generate profits. Since it will be able to carry significantly more cargo than either the A351 or the A380 it seems well positioned to generate very good revenue to me. The relevant question will be how much MX cost does the folding wing generate (I don't think it will be much) vs how much additional revenue can I make by having a more efficient wing.

Frankly the tradeoff makes sense to me. If I trade 1% or 2% of my total efficiency to be able to fit into existing 777 terminals I think I save a ton of money in both the short and long term. In truth I doubt the efficiency loss for having a folding wingtip is even that much.

Topic: RE: 77X - Folding Wingtip
Username: Roseflyer
Posted 2012-11-09 09:09:41 and read 3835 times.

Quoting rheinwaldner (Reply 41):

Anyway, folding wingtips carry a slight tone of desperation IMO...

Here’s my train of thought:

1: Airlines say that they want to limit wingspan to a certain dimension to fit existing airports otherwise they won’t buy the plane
2: Boeing evaluates wing tip options: winglet, folding wing, shorter wingspan
3: Boeing engineering analysis finds that an increased span is most efficient (x% better than a winglet), and that the weight & maintenance cost of a folding wingtip is more than accounted for by improved efficiency
4: Boeing proposes a folding wingtip as a new creative idea

It’s hardly desperation. It’s looking at things in new ways to continuously improve designs and find that way to make the 777x the best airplane.

Innovation is a great thing. Here’s some once common beliefs and the airplanes that proved them wrong:

There was a day when no one thought that an 8ft blended wingtip would be a good design (737NG)
There was a day when active load alleviation was never thought of as a way to reduce structural weight of the wing (L1011 and other various models)
There was a day when variable camber and spoiler droop were thought of as too complicated to be implemented (787)
There was a day when a moving production line was thought impossible for an airplane (737NG)
There was a day when semi-levered gear was thought of as too complex of a way to increase takeoff pitch angle (777-300ER)
There was a day when fly by wire was thought of as too unreliable to be used in commercial airplanes (A320)
There was a day when geared turbofans were thought of as too complex for a commercial jet (BAE 146 and then Cseries)
There was a day when twin engine airplanes were viewed as too unreliable to be used for transoceanic operations (767)

Boeing creates designs based on trade studies using math, not based on opinions and desperation.

Topic: RE: 77X - Folding Wingtip
Username: OldAeroGuy
Posted 2012-11-09 09:43:31 and read 3826 times.

Quoting Wisdom (Reply 31):
It would just be much easier, efficient and economic to draw a few lines of fresh paint on the tarmac.Airports are made to accommodate aircraft and not the other way around.

New paint won't help at an airport where the runway - taxiway separation distance is too close to support Code F operation without restrictions.

Quoting rheinwaldner (Reply 41):
But it still is a significant divergence from usual methods and no matter what there will be a penalty for the 77X's bottomline.

You're using an argument similar to what was said about the initial use of retractable landing gear.

Quoting Roseflyer (Reply 44):
It’s hardly desperation. It’s looking at things in new ways to continuously improve designs and find that way to make the 777x the best airplane.

Well said.

Topic: RE: 77X - Folding Wingtip
Username: joost
Posted 2012-11-09 09:57:29 and read 3836 times.

My thoughts:

The concept is presented to the press as a creative idea, to make airlines decide they don't want it.

I expect maintenance to be quite expensive for folding wingtips. Especially, as it's part of the primary structure of the aircraft: a 10ft wingtip is very likely to be on the MEL  

Boeing might offer it as an option. An expensive option. Then, airlines will start negotiating with their hub airport operators: "what are the costs to restructure the gates to allow class F aircraft?". Discussion will start, and eventually it will work out that airport changes are more cost-effective than airplane design changes. Then, the airline says "we don't need the option". That's different from Boeing saying "we can't offer". It very much improves the negotiation position of airlines towards airports.

Just look at the 787-3. The prime reason for the alternative design, was that it would fit 767 gates in Japan. Eventually, JAL and ANA found it, together with Boeing, more attractive to change airport usage and buy 787-8s.

Topic: RE: 77X - Folding Wingtip
Username: Roseflyer
Posted 2012-11-09 10:11:28 and read 3819 times.

Quoting joost (Reply 46):

I expect maintenance to be quite expensive for folding wingtips. Especially, as it's part of the primary structure of the aircraft: a 10ft wingtip is very likely to be on the MEL

I don't agree. For scheduled maintenance, a failure of the folding wingtip actuation would be evident to the flight crew, so it's not a hidden failure. Boeing is going to design enough redundancy, so that a single failure won't cause loss of the wingtip in flight. Using the latest industry guidance on scheduled maintenance, I'd predict that there would be no scheduled maintenance task for the wing tip.

There would be zonal inspections for the wingtip, but those already exist. So in total, I'd predict no change to scheduled maintenance costs. If it is a high corrosion area (which is possible), you might see some replacements, but flap and slat actuation is in the same or worse operating environment, and typically flap and slat actuation is not the primary cause for flight controls problems.

As for unscheduled maintenance, similar two position actuators like ground spoiler actuators last the lifetime of the airplane. Rarely are they ever replaced. Unscheduled maintenance should be relatively low, unless Boeing makes a bad failure prone design, which could happen, but I wouldn't assume that.

Topic: RE: 77X - Folding Wingtip
Username: sweair
Posted 2012-11-09 10:19:56 and read 3858 times.

Airbus has the A350, Boeing has the 787+777. Why on earth would they EOL the 777, the 787 is hardly even close to the 777 on the upper end. That would be the most stupid idea ever if B goes that route.

They can better optimize the market with 2 different families, 787 covers the lower market and the 777 the upper market, this combo will make it very hard for Airbus to compete. And I think our Swiss friend understand that too..

Topic: RE: 77X - Folding Wingtip
Username: EPA001
Posted 2012-11-09 10:37:40 and read 3849 times.

Quoting sweair (Reply 48):
this combo will make it very hard for Airbus to compete

Not at all. They will all find their place in the market easily.  

Topic: RE: 77X - Folding Wingtip
Username: sweair
Posted 2012-11-09 10:53:26 and read 3831 times.

Quoting EPA001 (Reply 49):

Sure, but it is harder to combat 2 separate families with just one and that is my point. Why give up an advantage?

Topic: RE: 77X - Folding Wingtip
Username: EPA001
Posted 2012-11-09 11:01:43 and read 3848 times.

Off-topic, but ok.

Quoting sweair (Reply 50):
Sure, but it is harder to combat 2 separate families with just one and that is my point.

Why? As long as you have the right product, your product will do fine up to very fine.

Quoting sweair (Reply 50):
Why give up an advantage?

Who is giving up what advantage?

But we better get back to the possible folding wing tips on the possible B777-X program.  

[Edited 2012-11-09 11:02:15]

Topic: RE: 77X - Folding Wingtip
Username: Wisdom
Posted 2012-11-09 11:05:56 and read 3827 times.

Quoting tdscanuck (Reply 34):

Quoting Wisdom (Reply 31):
The safeguards needed, and the actuating mechanism would add massive weight of several hundreds of kg.

Flaps are far more complex and highly loaded than the proposed tips, and even they don't have several hundred kg of actuation mechanism. This is an area where sizing and weight estimates are pretty mature.

Yes they do. On an aircraft the size of the B777, the hydraulic actuators alone weigh hundreds of kilograms. Heck, the torque tube, torque transfer rods and limiters together weigh in the hundreds. You need 4 and more people to carry one flap track fairing, how many does it take to carry a flap track itself? What about the attachment points of the flap itself, do they come for free?

The flaps require a lot of maintenance and they jam or get too loose and start vibrating. Regular A-checks lubrication is required, which requires a hangar and high access platforms.

Is a folding tip less complex than a flap? In its construction maybe, but you need to keep in mind that unlike flaps, slats and ailerons, the separation line to the wing runs in the length of the airplane, parallel to the direction of airflow. This makes it much much more complex to seal off from incoming air in order to provide a smooth continuous surface, especially for a wing that tends to bend upwards and down, resulting in additional drag.
In addition; the movement of flaps and ailerons is managed by single-axis screwjacks and gear mechanisms, but screwjacks aren't good at folding big heavy things at an agle of 90 degrees. So you need to use servo's, which add complexity and weight.

So yes, count 120kg each side for actuators, guides, rods, attachments, position sensors and locking mechanisms, additional 30kg each side for strengthening of the primary structures, and additional 20kg each side of weight for lubricating fluids, hydraulic fluids, piping, wiring for sensors and actuation running all the way to the avionics compartment where you would have a LRU weighing 10kg installed.
Did I mention the additional airfoils that will be required to seal off the space between the main wing and the tip, the additional mechanisms required to run and protect the bending wiring to the position and strobe lights, plus the additional position lights that will need to be installed so that when the tip is folded upwards, the extremities of the airplanes would still be visible at its parked position at night. What about anti-ice? The last place where I would want ice is at the leading edge of my tips! How are you going to guide bleed air in there?

Yadayada, on airliners.net everything is easy but if you had already managed a project like that, you would realise that it's much more complex than putting a few actuators on and voila. Armchair engineer

[Edited 2012-11-09 11:17:24]

Topic: RE: 77X - Folding Wingtip
Username: 7BOEING7
Posted 2012-11-09 11:55:37 and read 3802 times.

What if they're electric?????

Topic: RE: 77X - Folding Wingtip
Username: Aesma
Posted 2012-11-09 12:12:37 and read 3806 times.

If they do it, I'm hoping for an A380-9X with a massively longer fuselage, and 10m folding wingtips !

Topic: RE: 77X - Folding Wingtip
Username: BigJKU
Posted 2012-11-09 12:16:54 and read 3801 times.

Quoting joost (Reply 46):
Just look at the 787-3. The prime reason for the alternative design, was that it would fit 767 gates in Japan. Eventually, JAL and ANA found it, together with Boeing, more attractive to change airport usage and buy 787-8s.

That is a vastly different situation really. I don't think it compares at all.

Quoting Wisdom (Reply 52):
So yes, count 120kg each side for actuators, guides, rods, attachments, position sensors and locking mechanisms, additional 30kg each side for strengthening of the primary structures, and additional 20kg each side of weight for lubricating fluids, hydraulic fluids, piping, wiring for sensors and actuation running all the way to the avionics compartment where you would have a LRU weighing 10kg installed.

Even if we accept everything you say here we are talking about 340kg total which is something like 0.2% of the weight of the airplane overall. That is all probably pretty easily offset by the efficiency gains of the wing.

Topic: RE: 77X - Folding Wingtip
Username: OldAeroGuy
Posted 2012-11-09 12:43:50 and read 3823 times.

Quoting Wisdom (Reply 52):
What about anti-ice? The last place where I would want ice is at the leading edge of my tips! How are you going to guide bleed air in there?

De-icing the raked tip is not required. On the 7773ER today, there is no de-icing system for the outboard slat or raked tip.

Quoting BigJKU (Reply 55):
Even if we accept everything you say here we are talking about 340kg total which is something like 0.2% of the weight of the airplane overall.

On an airplane the size of the 7773ER, A350 or 777X, airframe weight must increase by 2.0t - 2.5t to increase mission fuel burn by 1%

Quoting BigJKU (Reply 55):
That is all probably pretty easily offset by the efficiency gains of the wing.

Very true. A 71m span wing has significantly less induced drag than a 65m wing with a winglet.

Topic: RE: 77X - Folding Wingtip
Username: rheinwaldner
Posted 2012-11-09 13:12:30 and read 3809 times.

Quoting tdscanuck (Reply 42):
It's not a penalty, it's a trade.

They fix an issue, that the competition does not face from the start (in order to achieve compelling economics). So there is a penalty achieving the same overall but investing more compexity, weight, manitenance cost and development effort...

Quoting tdscanuck (Reply 42):
proven solution

That's wrong. Not a single pax has flown with a civil aircraft equipped with something similar. Never before proved such a solution to offer cost efficient operations.

Quoting Roseflyer (Reply 44):
There was a day when no one thought that an 8ft blended wingtip would be a good design (737NG)
There was a day when active load alleviation was never thought of as a way to reduce structural weight of the wing (L1011 and other various models)
There was a day when variable camber and spoiler droop were thought of as too complicated to be implemented (787)
There was a day when a moving production line was thought impossible for an airplane (737NG)
There was a day when semi-levered gear was thought of as too complex of a way to increase takeoff pitch angle (777-300ER)
There was a day when fly by wire was thought of as too unreliable to be used in commercial airplanes (A320)
There was a day when geared turbofans were thought of as too complex for a commercial jet (BAE 146 and then Cseries)
There was a day when twin engine airplanes were viewed as too unreliable to be used for transoceanic operations (767)

True, the things that you quote mostly have or will set new standards. But the fact that they did set standards is the difference to the 77X folding wingtips. Or do you think that folding wings will be the standard for passenger jets in the future?

If the future will turn out that way, you can call me Hugo...

Quoting OldAeroGuy (Reply 45):
You're using an argument similar to what was said about the initial use of retractable landing gear.

No, the landing gear was obvious and is unchallenged state of technology today. Do you think that folding wings will be the standard for passenger jets in the future?

If that would be reasonable it could have been used long before. But as the gains never made worth the disadvantages so far, to me it sounds that Boeing is facing some hefty challenges to bring in the economic gains that are needed.

Remember the planned 789 wing that suddenly was not worth the effort to get somewhat better span and efficiency? What is a credible explanation that the 789 is fine without such addons and the 77X needs it?

Quoting Wisdom (Reply 52):
on airliners.net everything is easy

Not everything. Mostly this applies if Boeing presents their drafts.

Topic: RE: 77X - Folding Wingtip
Username: OldAeroGuy
Posted 2012-11-09 13:31:24 and read 3812 times.

Quoting rheinwaldner (Reply 57):
No, the landing gear was obvious and is unchallenged state of technology today.

It's not obvious until you try it, foldng gear was not unchallenged technology in the 30's when it was developed. Besides, retractable landing gear does increase maintenance costs vs fixed gear. The efficiency gains make it worthwhile.

Quoting rheinwaldner (Reply 57):
Do you think that folding wings will be the standard for passenger jets in the future?

Quite possible if span added for efficiency exceeds an operating Code limit.

Quoting rheinwaldner (Reply 57):
Remember the planned 789 wing that suddenly was not worth the effort to get somewhat better span and efficiency? What is a credible explanation that the 789 is fine without such addons and the 77X needs it?

The proposed 789 span didn't exceed the Code E limit. There would have been no point to have a foldng tip on the 789.

The 777X is a larger airplane and can benefit from a span increase that exceeds the Code E limit. Therefore a folding tip becomes viable. Design philosophies do evolve over time.

Topic: RE: 77X - Folding Wingtip
Username: sweair
Posted 2012-11-09 14:07:30 and read 3800 times.

Even in these modern times people are very sceptical of new ways of solving problems. Remember how many said that CFRP wasnt realistic? Bleedless architecture was a no go etc

We should all strive for technoloical steps forward, dont be so conservative!

Topic: RE: 77X - Folding Wingtip
Username: JoeCanuck
Posted 2012-11-09 18:08:30 and read 3784 times.

Just ask the folks trying to get a third runway at LHR how easy it is to modify an airport.

A folding wing isn't rocket surgery. It's been done in a variety of ways since the 30's...and most of those with the cables, torque tubes, wires and hydraulics passing through the hinge. Just like with the carrier planes, the tradeoffs of weight and complexity, with simplicity were well worth the effort.

Let's say the mods weigh as much as 500kg...not very significant for a plane with an MTOW over the 77W's 350,000kg. That's around 0.14 percent of the MTOW...not a lot of weight for something which may add significant aerodynamic benefits.

Boeing has worked out way tougher problems.

Topic: RE: 77X - Folding Wingtip
Username: jetmech
Posted 2012-11-09 20:24:07 and read 3795 times.

Quoting Wisdom (Reply 52):
On an aircraft the size of the B777, the hydraulic actuators alone weigh hundreds of kilograms

The primary actuation device for 777 flaps are screwjacks.

http://www.youtube.com/watch?v=b3fEoTfE8Hw

I agree with you that the entire setup would probably add 200-300kg to the weight of the aircraft, but the actuators alone weighing hundreds of kilograms?

Quoting Wisdom (Reply 52):
This makes it much much more complex to seal off from incoming air in order to provide a smooth continuous surface, especially for a wing that tends to bend upwards and down,

The actual sealing of the differential air pressure between the upper and lower surfaces of the wing can be achieved using rubber seals of the type and design used for doors, where much greater differential pressures exist. A smooth contour can be then achieved with carefully machined panels.

Quoting Wisdom (Reply 52):
What about anti-ice? The last place where I would want ice is at the leading edge of my tips! How are you going to guide bleed air in there?

As for anti-ice, as others have mentioned, the tip region does not have this feature, but it appears that it has been done prior.

Quoting Wisdom (Reply 52):
So you need to use servo's, which add complexity and weight.

An electrically or hydraulically driven, planetary reduction actuator would be ideal for folding a 777 wingtip. The following photo shows how anti-ice, a planetary reduction actuator for folding and automatically connecting / disconnecting mechanical flight controls have been done before.

http://johnwright.smugmug.com/Aviation/Air-Museums/Midway-Magic/IMG533-3324-20D/341312696_SFPQE-L.jpg

http://johnwright.smugmug.com/Aviati...533-3324-20D/341312696_SFPQE-L.jpg

According to others, the 777 wingtip will not have anti-ice or any flight controls, so the main element of concern would be the folding actuator only.

Quoting Wisdom (Reply 52):
Yadayada, on airliners.net everything is easy but if you had already managed a project like that, you would realise that it's much more complex than putting a few actuators on and voila. Armchair engineer

No one here is saying it will be a simple job; then again, it won't be the most difficult aerospace engineering task ever encountered either.

Regards, JetMech

[Edited 2012-11-09 20:31:27]

Topic: RE: 77X - Folding Wingtip
Username: tdscanuck
Posted 2012-11-09 20:38:36 and read 3779 times.

Quoting Wisdom (Reply 52):
On an aircraft the size of the B777, the hydraulic actuators alone weigh hundreds of kilograms.

Yes, all of the actuators *together* weight that much. But you're only talking about two to do both folding tips. Individual actuators don't weight nearly that much, especially ones that aren't called on to handle flight loads and only do one cycle per flight.

Quoting Wisdom (Reply 52):
Heck, the torque tube, torque transfer rods and limiters together weigh in the hundreds. You need 4 and more people to carry one flap track fairing, how many does it take to carry a flap track itself? What about the attachment points of the flap itself, do they come for free?

This was exactly my point...a flap is *far* more complex and we're fine with that level of weight/complexity/reliability. A folding wing joint (that doesn't have to actuate in the air) is, in comparrison, vastly simpler and lighter.

Quoting Wisdom (Reply 52):
Is a folding tip less complex than a flap?

Yes, hugely so. Folding tip mechanisms don't require multiple slots, be able to operate under air load, be able to assume more than two positions, handle flight loads through the actuators, sync with their counterpart on the opposite side, etc.

Quoting Wisdom (Reply 52):
In its construction maybe, but you need to keep in mind that unlike flaps, slats and ailerons, the separation line to the wing runs in the length of the airplane, parallel to the direction of airflow. This makes it much much more complex to seal off from incoming air in order to provide a smooth continuous surface, especially for a wing that tends to bend upwards and down, resulting in additional drag.

This is exactly the same problem as slat aerodynamic seals (only the folding tips have two, as opposed to the ~12 for slats). Somehow, we muddle through.

Quoting Wisdom (Reply 52):
In addition; the movement of flaps and ailerons is managed by single-axis screwjacks and gear mechanisms, but screwjacks aren't good at folding big heavy things at an agle of 90 degrees. So you need to use servo's, which add complexity and weight

I'm not aware of any modern large jet actuating ailerons by screwjacks or gears. Folding big heavy things is what you do with hydraulic rams, just like we actuate landing gear today. I'm not aware of any modern large jet that uses servos for landing gear either.

Quoting Wisdom (Reply 52):
What about anti-ice? The last place where I would want ice is at the leading edge of my tips! How are you going to guide bleed air in there?

We don't anti-ice the tips now (or the empennage)...why would we suddenly start just because they're folding tips?

Quoting Wisdom (Reply 52):
Yadayada, on airliners.net everything is easy but if you had already managed a project like that, you would realise that it's much more complex than putting a few actuators on and voila.

I've managed projects like this. I didn't say it was easy in the abstract. I said that, compared to things that have already been done, it's relatively easy.

Quoting Wisdom (Reply 52):
Armchair engineer

Sorry, actual engineer.

Quoting rheinwaldner (Reply 57):
Quoting tdscanuck (Reply 42):
proven solution

That's wrong. Not a single pax has flown with a civil aircraft equipped with something similar.

Are we going to claim that digital FBW wasn't proven until the A320 had it then? Or that jet engines were unproven before the Comet? Folding wings have been around for ~80 years. We can quibble all we want to about whether the economic trade works out, but it's pretty difficult to claim it's unproven technology. The wing fold mechanism has no idea if it's attached to a carrier jet or an airliner.

Quoting rheinwaldner (Reply 57):
Remember the planned 789 wing that suddenly was not worth the effort to get somewhat better span and efficiency? What is a credible explanation that the 789 is fine without such addons and the 77X needs it?

The 777X is bigger. That's about all the credible explanation required.

Tom.

Topic: RE: 77X - Folding Wingtip
Username: rheinwaldner
Posted 2012-11-10 05:00:24 and read 3765 times.

Quoting sweair (Reply 59):
We should all strive for technoloical steps forward, dont be so conservative!

I did propose mind boggling aviation innovations that were beyond the wildest imaginations of basically everybody:
Orbital Transit Aircraft (by rheinwaldner Apr 5 2011 in Tech Ops)

So I don´t feel guilty of being conservative.

About the 77X I try to be realistic (unrealistic optimism won´t serve Boeing neither). And about the folding wings I just tried to counter the applauding crowd a bit.

Without raising the slightest form of a doubt they wanted us to believe, that folding wings are that solution that should always have been used. I wonder why this idea did not materialize long time ago? Why did earlier tradeoff analysis never favour the folding wings before? I just recognize that the strive to achieve compelling economics makes Boeing rethinking solutions that were never worth the effort earlier...

Quoting tdscanuck (Reply 62):
That's wrong. Not a single pax has flown with a civil aircraft equipped with something similar.

Are we going to claim that digital FBW wasn't proven until the A320 had it then?

So why were the airlines not convinced the first time Boeing did try to sell 777´s like that? I bet the word "unproven" was often heard when the airlines argued against it...

Topic: RE: 77X - Folding Wingtip
Username: tdscanuck
Posted 2012-11-10 05:41:11 and read 3766 times.

Quoting rheinwaldner (Reply 63):
Without raising the slightest form of a doubt they wanted us to believe, that folding wings are that solution that should always have been used.

No. The 777 was just fine without folding wings before because the airlines decided they'd rather handle the span operationally (gate spacing, etc.). That may not be an option for the 777X, or at least not as attractive an option, so the idea is back on the table because the span is even bigger.

Quoting rheinwaldner (Reply 63):
I wonder why this idea did not materialize long time ago?

Because the wing wasn't as big a long time ago.

Quoting rheinwaldner (Reply 63):
Why did earlier tradeoff analysis never favour the folding wings before?

Because it's easier to operationally accommodate a smaller span than a bigger one.

Quoting rheinwaldner (Reply 63):
I just recognize that the strive to achieve compelling economics makes Boeing rethinking solutions that were never worth the effort earlier...

Of course. That's *always* why you rethink solutions. The last time Boeing was faced with this decision, the span wasn't as big so the operational/aerodynamic trade was different. Airbus almost certainly went through a similar trade, internally or externally, over the A380 but decided that they would take unprecedented operational limitations to keep the span down. That may well be how the 777X goes as well, but Boeing is right to at least offer the option and see which way the customers want to go.

Quoting rheinwaldner (Reply 63):
Quoting tdscanuck (Reply 62):
That's wrong. Not a single pax has flown with a civil aircraft equipped with something similar.

Are we going to claim that digital FBW wasn't proven until the A320 had it then?

So why were the airlines not convinced the first time Boeing did try to sell 777´s like that? I bet the word "unproven" was often heard when the airlines argued against it...

They didn't care about unproven, they cared about "How much cost/weight/complexity am I going to pick up compared to how much I'm going to save and how much of a pain will it be to simply accept the bigger span." At the time the 777 was originally designed, the "how much will I save" was *much* smaller in dollar terms operational impact was much smaller than the proposed 777X.

Tom.

Topic: RE: 77X - Folding Wingtip
Username: PITingres
Posted 2012-11-10 07:31:09 and read 3737 times.

Quoting rheinwaldner (Reply 63):
So why were the airlines not convinced the first time Boeing did try to sell 777´s like that?

To elaborate somewhat on what tdscanuck has already tried to tell you, the initial 777 folding wing idea involved much more of the wing length (21 ft vs 10, according to earlier posters) and involved control surfaces. This made the earlier folding wing heavier and more complex compared to the 777X proposal, which made it less desirable.

Quoting rheinwaldner (Reply 63):
And about the folding wings I just tried to counter the applauding crowd a bit.

Why? Good ideas are good ones, even if it is Boeing proposing them. If it's a worthwhile tradeoff airlines will buy it. If they don't see enough benefit, they won't. That is simple enough. What here do you think needs countering?

Topic: RE: 77X - Folding Wingtip
Username: shankly
Posted 2012-11-10 08:34:35 and read 3732 times.

Quoting tdscanuck (Reply 34):
Aircraft are always made to accommodate airports, not the other way around


And of course that sometimes means not seeing the wood for the trees.......VC-10? Designed for short, hot n' high runways. Wonderful, except everyone with a short, hot n' high runway then went and made their runways longer so that 707's and DC-8's could operate

I would imagine that the Certification issues of a folding wing tip, particularly relating to in flight failure (and of course ETOPS) will be far more interesting than the technical solution

Topic: RE: 77X - Folding Wingtip
Username: OldAeroGuy
Posted 2012-11-10 08:58:39 and read 3748 times.

Quoting shankly (Reply 66):
I would imagine that the Certification issues of a folding wing tip, particularly relating to in flight failure (and of course ETOPS) will be far more interesting than the technical solution

I suspect that 777X folding wing tip Certification issues will be on a par with those of a cargo door. Both depend on ground operation with robust locking and position detection systems.

In fact, given that the 777X folding tip is rather small compared to the total wing span and doesn't involve control surfaces, a cargo door failure probably repesents a greater risk to airplane safety.

Topic: RE: 77X - Folding Wingtip
Username: Stitch
Posted 2012-11-10 09:02:33 and read 3751 times.

Quoting rheinwaldner (Reply 63):
And about the folding wings I just tried to counter the applauding crowd a bit.

I don't see much "applauding" the idea - more countering negative arguments.



Quoting rheinwaldner (Reply 63):
I wonder why this idea did not materialize long time ago? Why did earlier tradeoff analysis never favour the folding wings before?

The 747 family was already a Category V | Code E airframe so in the over two decades since that family had entered service, most major airports had re-designed themselves to accommodate large aircraft with upwards of a 65m span. So the number of airports and gates that could only accommodate a 777 with a sub-53m span were few enough that it wasn't worth the benefit.



And to that end, it may very well be that Boeing limits the span to the 68m of the 747-8. While a Category VI | Code F plane, 68m is close enough to 65m that it appears to not be much of an issue for airport compatibility considering how many airports have been certified to handle the 747-8 with little to no modification.

So we may see something like the 787-9, where the benefits of pushing it out another 3m to 71m (and therefore requiring folding wingtips) are outweighed by the weight and complexity.

Topic: RE: 77X - Folding Wingtip
Username: sweair
Posted 2012-11-10 09:43:07 and read 3732 times.

I bet if this works out fine that Airbus goes this route on a future A380 update, this is how things work out, one takes a step ahead and if that works and catches on, others follow. Its perfect for making a large airframe more flexible in ground operations, opens up a larger market/airports that can handle it.

Topic: RE: 77X - Folding Wingtip
Username: tdscanuck
Posted 2012-11-10 11:12:00 and read 3749 times.

Something I hadn't noticed until I checked today is the magnitude of the folded span difference between the two models.

777X: 68m full span / 62m folded
777 original: 61m full span / 49m folded (basically 767 sized)

The original 777 folding proposal was *much* smaller ( than what's being proposed now. The folded 777X is basically the same span as the original 777 without the fold. In other words...folding the 777X lets it use almost all the existing 777 infrastructure. That's probably the main reason the idea is back.

The prior fold was trying to stuff a 777 into existing 767 infrastructure; a much taller order, hence the much larger fold and related step-change in complexity. The proposed fold is trying to keep the 777X in the 777 infrastructure, which isn't nearly as hard. If the airports & airlines decide they don't mind bumping the 777X up to need the extra room, the fold will disappear.

Tom.

Topic: RE: 77X - Folding Wingtip
Username: EPA001
Posted 2012-11-10 11:26:21 and read 3748 times.

Quoting tdscanuck (Reply 64):
Of course. That's *always* why you rethink solutions. The last time Boeing was faced with this decision, the span wasn't as big so the operational/aerodynamic trade was different. Airbus almost certainly went through a similar trade, internally or externally, over the A380 but decided that they would take unprecedented operational limitations to keep the span down. That may well be how the 777X goes as well, but Boeing is right to at least offer the option and see which way the customers want to go.

Agreed. One has to go through all the motions before offering an option like this. Every design issue is always a trade-off, but this could be the solution with the smallest number of downsides and the highest number of upsides.  

If I recall correctly Airbus wanted a wing on the A380 which was about 84-85 meters in span. With 79.8 meters they got close enough for their goals, and the operational data of the A380 justified their choice.

Quoting sweair (Reply 69):

I bet if this works out fine that Airbus goes this route on a future A380 update,

They might, they might not. It is not a foregone conclusion that they would do so, even if it was going to be a success on the B777-X program. There are a lot of variables to take into account before one would offer this option. These might not necessarily be the same things as on the B777-X program.

Topic: RE: 77X - Folding Wingtip
Username: rheinwaldner
Posted 2012-11-12 05:36:10 and read 3680 times.

Quoting tdscanuck (Reply 64):
Quoting rheinwaldner (Reply 63):
I wonder why this idea did not materialize long time ago?

Because the wing wasn't as big a long time ago.

The wing of any aircraft in the past was larger than the gatespace the aircraft ideally would have fitted into. So there is absolutely no new requirement for the 77X. But if the trade-off would have favoured such a solution in the past we would have seen it.

See, I simply focus on the "what has changed?"-question. And as I can see no other evident factor, I just feel that the need to squeeze out the last bit of efficiency is the driver behind this "unusual" step. I don't say it does not work or it is not a net-positive tradeoff. I just sense that the net-gain never made worth such solutions in the past so there must be an unusual urge to haunt efficiency in case of the 77X.

Boeing seems willing to cross a line, that nobody thought to be worth to be crossed in the past. I mean the re-wingged A350MK1 would have benefitted from such a solution, the A330 with a 747-kind-of-span or basically any other aircraft (because operating from smaller gates would be a nice incentive for any aircraft).

Quoting PITingres (Reply 65):
To elaborate somewhat on what tdscanuck has already tried to tell you, the initial 777 folding wing idea involved much more of the wing length (21 ft vs 10, according to earlier posters) and involved control surfaces.

According to Tom both solutions are equally proven.

Quoting PITingres (Reply 65):
If it's a worthwhile tradeoff airlines will buy it.

I don't disagree...

Quoting Stitch (Reply 68):
I don't see much "applauding" the idea - more countering negative arguments.

And what was the tone in the first ~40 posts? Before my first one?

Quoting sweair (Reply 69):
I bet if this works out fine that Airbus goes this route on a future A380 update

IMO the chance is small. Because of the condition you define.

Quoting tdscanuck (Reply 70):
The prior fold was trying to stuff a 777 into existing 767 infrastructure; a much taller order, hence the much larger fold and related step-change in complexity.

Why would it be a taller order if per your definition a technology is proven if it just exists somewhere?

Topic: RE: 77X - Folding Wingtip
Username: bikerthai
Posted 2012-11-12 06:31:46 and read 3658 times.

Haven't been on for a few days so I'm late to this conversation. So apologies while I try to catch up.

Quoting sweair (Reply 13):

Yeah CFRP in the F35 sure beats the F35 in plain old aluminium. The current gen CFRP is not the most ideal, coming gen2 that the JSF uses is another thing.

The F-35 composite is a high temperature composite that is needed to meet supersonic skin heating requirement. That material is much harder to work with than the standard epoxy. I believe the material use is a bismaleimide system.

Quoting Wisdom (Reply 31):

Did I mention the risk of the wing folding inflight or malfunctioning actuating/guiding mechanisms piercing into the wing/wing tanks?

So if the failure is typically in the mechanism, then any failure mode would cause wingtip to be up. They can then manually lower the tip and lock it . . . thus allowing for dispatch until the mechanism can be fixed.

Now if the failure is structural, which is a lot less likely, would they be able to fly with a lost wing tip? That would be an interesting certification question.

bt

Topic: RE: 77X - Folding Wingtip
Username: ferpe
Posted 2012-11-12 07:37:39 and read 3664 times.

Quoting tdscanuck (Reply 70):
777X: 68m full span / 62m folded

I don't know where you did get the 68m span from, the talk is of 71m.

Anyway, the easiest way to judge what a folding raked tip of 71m span would give (blue curve) vs. a feathered winglet like the MAX staying inside Cat E (65m, red curve) is to show the payload-range diagram and average fuel burn for the two, here with the 35J (orange curve) as reference (click on the chart to see better) :


http://i298.photobucket.com/albums/mm262/ferpe_bucket/PR35J9X679X70.jpg


As always, a frame always flies best on a ppt payload-range chart, especially when made with my crude model, ie no guarantees that this is close to reality   . It seems the folding complexity is worth the while however, the L/D at average cruise weight goes from 20.5 to 21.2 (everything else is kept equal).

Re 35J, this is the nominal 35J, by 2020 it might have got the first PIP onboard    .

Edit: added the L/D change.

[Edited 2012-11-12 08:02:23]

Topic: RE: 77X - Folding Wingtip
Username: PITingres
Posted 2012-11-12 07:42:30 and read 3660 times.

Quoting rheinwaldner (Reply 72):
And what was the tone in the first ~40 posts? Before my first one?

And I ask you again, why do you think that there is a problem?

You insist on painting the folding wingtip as something weird if not downright outrageous, and apparently your justification for doing so is that too many people think it might possibly be a good idea?  

Topic: RE: 77X - Folding Wingtip
Username: tdscanuck
Posted 2012-11-12 07:53:45 and read 3673 times.

Quoting rheinwaldner (Reply 72):
See, I simply focus on the "what has changed?"-question. And as I can see no other evident factor

How is crossing from Group V to Group VI not a relevant factor? *That* is what changed.

Quoting rheinwaldner (Reply 72):
Boeing seems willing to cross a line, that nobody thought to be worth to be crossed in the past. I mean the re-wingged A350MK1 would have benefitted from such a solution, the A330 with a 747-kind-of-span or basically any other aircraft (because operating from smaller gates would be a nice incentive for any aircraft).

The tradeoff is always different when you change aircraft sizes. You need to look at how many gates/ramps/airports are available to you with the two spans and how that compares to how many you need to be economically viable. Since the airports typically design around group boundaries, crossing into another group causes a step-change in how many facilities are available to you. Moving within the group may cause some small changes but nothing drastic.

Quoting rheinwaldner (Reply 72):
Quoting PITingres (Reply 65):
To elaborate somewhat on what tdscanuck has already tried to tell you, the initial 777 folding wing idea involved much more of the wing length (21 ft vs 10, according to earlier posters) and involved control surfaces.

According to Tom both solutions are equally proven.

Yes. One is a lot cheaper/lighter/easier to maintain though.

Quoting rheinwaldner (Reply 72):
Quoting tdscanuck (Reply 70):
The prior fold was trying to stuff a 777 into existing 767 infrastructure; a much taller order, hence the much larger fold and related step-change in complexity.

Why would it be a taller order if per your definition a technology is proven if it just exists somewhere?

Orbital flight is proven too but that doesn't mean it's a viable method for commercial travel (yet). In order to get the original 777 into a 767 gate, they had to fold with control surfaces (ailerons and slats) outboard of the fold. Although such folds are proven (the military has been using them for decades) they're heavy, complicated, and expensive. The airlines decided it was easier to deal with the 777 not fitting into a 767 gate and the fold went away.

This time they're *not* trying to get the 777 into a 767 gate (that's the answer to your "What has changed?"). The 777 already has plenty of Group V infrastructure. They're trying to *keep* it in that group, but they want a Group VI wingspan for efficiency. But that doesn't require nearly as much of a span reduction so they're looking at only folding the outer chunk of the wing with no control surfaces. This means that the fold, although still heavier/more complex/more expensive than no-fold, is much lighter/simpler/cheaper than the one they proposed ~20 years ago. It *may* be that the additional benefits are sufficient to pay for the increased weight/complexity/cost (expecially given a much different fuel price situation than the original 777). If it is, you'll see the fold. If the airlines decide they'd rather upgrade their 777X operations to Group VI, then we won't.

Tom.

Topic: RE: 77X - Folding Wingtip
Username: rwessel
Posted 2012-11-12 08:46:47 and read 3648 times.

Quoting tdscanuck (Reply 76):
But that doesn't require nearly as much of a span reduction so they're looking at only folding the outer chunk of the wing with no control surfaces. This means that the fold, although still heavier/more complex/more expensive than no-fold, is much lighter/simpler/cheaper than the one they proposed ~20 years ago.

Had Boeing wanted to include control surfaces in the folding part of the wing, using 787-style electro-hydraulic actuators would have greatly simplified that problem as well. Increasing the mass of the folding bit would increase the mass of the folding mechanism, OTOH.

Topic: RE: 77X - Folding Wingtip
Username: Roseflyer
Posted 2012-11-12 09:43:21 and read 3655 times.

Quoting rheinwaldner (Reply 72):

See, I simply focus on the "what has changed?"-question. And as I can see no other evident factor, I just feel that the need to squeeze out the last bit of efficiency is the driver behind this "unusual" step. I don't say it does not work or it is not a net-positive tradeoff. I just sense that the net-gain never made worth such solutions in the past so there must be an unusual urge to haunt efficiency in case of the 77X.

What changed? Boeing is trying to build the highest capacity twin engine jet ever built. They also realized that they hope to sell more of them than the 747-8, so while the 747 program went ahead with increasing the span since they knew the airplane was going to be a lower production airplane, they figured airlines could work around the wingspan stretch. I assume they are finding based on talking to potential customers that a higher wingspan would prevent some airlines from ordering the airplane.

Boeing is trying to increase useable payload, but not increase MTOW. That’s a different approach and quite innovative in my mind. They are trying to do it with efficiency, and the higher payload and range of the 777-9X over A350-1000 (according to Ferpe’s charts) indicate that they need to push the design harder.

“there must be an unusual urge to haunt efficiency in the case of the 77X” ????? HUH? What are you talking about? There’s always an urge to increase efficiency. There have been many designs that have been complicated in an attempt to chase efficiency without making other tradeoffs.

Here are some examples:
777-300ER Semi-levered gear. The gear design is heavier and more complex so that the airplane can rotate off of the aft axle. This allowed getting 1 extra degree of takeoff rotation to improve MTOW without lengthening the gear.
737-900ER/737-800 Short Field Performance: Spoiler panels exceed typical deflection rates and there is a two position tail skid that adds complexity, but helps improve takeoff and landing performance
737MAX Winglets: Gate restrictions prevented a raked wingtip, so the wingtip extension is now even more complicated

If Boeing wasn’t trying every new idea to get extra efficiency then they wouldn’t be in the business.

I have a sense there is an underlying tone in your posts (I know you didn’t say this) that “Boeing is crossing lines that were never crossed in the past because they fear that the A350-1000 is going to be so good that the 777X won’t have a chance at being as good”.

Topic: RE: 77X - Folding Wingtip
Username: tdscanuck
Posted 2012-11-12 17:36:15 and read 3629 times.

Quoting ferpe (Reply 74):
I don't know where you did get the 68m span from, the talk is of 71m.

I took it from the OP and stuck with it for consistency:

Quoting frmrCapCadet (Thread starter):
How big a deal is it to fold the outer 10 feet of a 233 foot wing span?

If it's actually 71m, all the arguments apply even more so.

Tom.


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