frmrCapCadet
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77X - Folding Wingtip

Tue Nov 06, 2012 4:24 pm

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]
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Stitch
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RE: 77X - Folding Wingtip

Tue Nov 06, 2012 4:32 pm

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.
 
iFlyLOTs
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RE: 77X - Folding Wingtip

Tue Nov 06, 2012 4:33 pm

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..
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roseflyer
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RE: 77X - Folding Wingtip

Tue Nov 06, 2012 5:07 pm

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.
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Aesma
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RE: 77X - Folding Wingtip

Tue Nov 06, 2012 5:24 pm

Wouldn't that weigh a lot ?
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Stitch
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RE: 77X - Folding Wingtip

Tue Nov 06, 2012 6:27 pm

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]
 
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Aesma
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RE: 77X - Folding Wingtip

Tue Nov 06, 2012 6:30 pm

Well if they're folding they need a folding mechanism, that's what I was wondering about.
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cosmofly
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RE: 77X - Folding Wingtip

Tue Nov 06, 2012 6:46 pm

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.
 
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Stitch
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RE: 77X - Folding Wingtip

Tue Nov 06, 2012 6:52 pm

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]
 
JAAlbert
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RE: 77X - Folding Wingtip

Tue Nov 06, 2012 7:28 pm

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?
 
roseflyer
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RE: 77X - Folding Wingtip

Tue Nov 06, 2012 7:48 pm

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.
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LLA001
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RE: 77X - Folding Wingtip

Tue Nov 06, 2012 7:49 pm

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.
 
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RE: 77X - Folding Wingtip

Tue Nov 06, 2012 7:54 pm

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.   
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sweair
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RE: 77X - Folding Wingtip

Tue Nov 06, 2012 8:03 pm

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.
 
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Aesma
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RE: 77X - Folding Wingtip

Tue Nov 06, 2012 8:08 pm

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 ?
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ferpe
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RE: 77X - Folding Wingtip

Tue Nov 06, 2012 9:30 pm

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! .
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roseflyer
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RE: 77X - Folding Wingtip

Tue Nov 06, 2012 10:19 pm

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.
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RE: 77X - Folding Wingtip

Tue Nov 06, 2012 11:41 pm

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.
 
roseflyer
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RE: 77X - Folding Wingtip

Tue Nov 06, 2012 11:47 pm

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.
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EPA001
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RE: 77X - Folding Wingtip

Wed Nov 07, 2012 12:00 am

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.
 
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RE: 77X - Folding Wingtip

Wed Nov 07, 2012 12:05 am

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.
 
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Stitch
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RE: 77X - Folding Wingtip

Wed Nov 07, 2012 12:44 am

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.
 
strfyr51
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RE: 77X - Folding Wingtip

Wed Nov 07, 2012 1:41 am

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 .
 
roseflyer
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RE: 77X - Folding Wingtip

Wed Nov 07, 2012 5:09 pm

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.
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OldAeroGuy
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RE: 77X - Folding Wingtip

Thu Nov 08, 2012 12:38 am

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

Or a landing gear door.
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Mike89406
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RE: 77X - Folding Wingtip

Thu Nov 08, 2012 12:53 am

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.
 
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Stitch
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RE: 77X - Folding Wingtip

Thu Nov 08, 2012 3:01 am

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.
 
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RE: 77X - Folding Wingtip

Thu Nov 08, 2012 4:55 am

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.
What the...?
 
roseflyer
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RE: 77X - Folding Wingtip

Thu Nov 08, 2012 5:38 am

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.
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scbriml
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RE: 77X - Folding Wingtip

Thu Nov 08, 2012 6:29 am

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.
Time flies like an arrow. Fruit flies like a banana!
 
JoeCanuck
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RE: 77X - Folding Wingtip

Thu Nov 08, 2012 7:18 am

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.
What the...?
 
Wisdom
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RE: 77X - Folding Wingtip

Thu Nov 08, 2012 8:30 pm

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.
 
JoeCanuck
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RE: 77X - Folding Wingtip

Thu Nov 08, 2012 8:45 pm

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.
What the...?
 
roseflyer
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RE: 77X - Folding Wingtip

Thu Nov 08, 2012 9:44 pm

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.
If you have never designed an airplane part before, let the real designers do the work!
 
tdscanuck
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RE: 77X - Folding Wingtip

Thu Nov 08, 2012 11:10 pm

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.
 
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kanban
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RE: 77X - Folding Wingtip

Fri Nov 09, 2012 2:10 am

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.
 
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Stitch
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RE: 77X - Folding Wingtip

Fri Nov 09, 2012 2:24 am

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.
 
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kngkyle
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RE: 77X - Folding Wingtip

Fri Nov 09, 2012 2:51 am

I hope they do it, just for the sake of it being something new and interesting, like the 747 hump.
 
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kanban
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RE: 77X - Folding Wingtip

Fri Nov 09, 2012 6:39 am

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!
 
JoeCanuck
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RE: 77X - Folding Wingtip

Fri Nov 09, 2012 7:39 am

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]
What the...?
 
KC135Hydraulics
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RE: 77X - Folding Wingtip

Fri Nov 09, 2012 7:56 am

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.
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rheinwaldner
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RE: 77X - Folding Wingtip

Fri Nov 09, 2012 1:42 pm

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...
 
tdscanuck
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RE: 77X - Folding Wingtip

Fri Nov 09, 2012 2:18 pm

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.
 
bigjku
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RE: 77X - Folding Wingtip

Fri Nov 09, 2012 3:00 pm

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.
 
roseflyer
Posts: 9606
Joined: Fri Feb 13, 2004 9:34 am

RE: 77X - Folding Wingtip

Fri Nov 09, 2012 5:09 pm

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.
If you have never designed an airplane part before, let the real designers do the work!
 
OldAeroGuy
Posts: 3187
Joined: Sun Dec 05, 2004 6:50 am

RE: 77X - Folding Wingtip

Fri Nov 09, 2012 5:43 pm

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.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
Joost
Posts: 1841
Joined: Wed Apr 20, 2005 8:27 pm

RE: 77X - Folding Wingtip

Fri Nov 09, 2012 5:57 pm

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.
 
roseflyer
Posts: 9606
Joined: Fri Feb 13, 2004 9:34 am

RE: 77X - Folding Wingtip

Fri Nov 09, 2012 6:11 pm

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.
If you have never designed an airplane part before, let the real designers do the work!
 
sweair
Posts: 1816
Joined: Sun Nov 20, 2011 9:59 am

RE: 77X - Folding Wingtip

Fri Nov 09, 2012 6:19 pm

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..
 
User avatar
EPA001
Posts: 3794
Joined: Tue Sep 12, 2006 8:13 pm

RE: 77X - Folding Wingtip

Fri Nov 09, 2012 6:37 pm

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.  

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