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A380 - the best is yet to come

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A380 - the best is yet to come

Old 26th Jul 2018, 11:07
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Originally Posted by Volume
Compared to the design of some aircraft carrier operated military aircraft or some folding wing motorgliders I do not think so.
There are for example 4 individually actuated latch pins, there is a locking mechanism and there is a folding actuator meaning 6 actuators where most landing gears have only two...
And the folding axis is not perpendicular to the wing centerline, making the structure around it extremely complex. (The alternative would have been more air loads during taxi).
I'm not certain, but I believe you are describing the optional 777 wing fold mechanism. The 777X mechanism is much simpler. The 777 wing folded 21 ft of wing. The 777X only folds 10 feet of wing, with essentially only the raked wing tip getting folded. Each folding wingtip has a single rotary fold actuator and four latch pins with integral actuators.

As for the number of actuators in a landing gear system, in order to sequence the doors properly, many systems require a separate actuator for each door and each leg often has multiple doors.

It puts the A/C packs in the fairings, the recirc filters, mixers, fans etc. are all between the cargo bay and the center wing box reducing the available cargo volume.
Those components are indeed behind the center wing box in the belly.. However, the landing gear retract into the area further behind the center wing box. That area is not available for cargo loading anyway.

Last edited by KenV; 26th Jul 2018 at 12:06.
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Old 26th Jul 2018, 12:42
  #122 (permalink)  
 
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Originally Posted by procede
Where the comparison with the 747 flap system goes astray, is that the folding wing folds in the direction of the main force (up) where the track system folds in the direction of the wing cord (and down). The flap system thus needs less safety measures to stop it from extending or retracting due to aerodynamic forces.
A few points:
1. The wingtip only folds/unfolds on the ground. The flaps MUST extend and retract in flight.
2. The wingtips only have two positions. The flaps have multiple positions.
3. The wingtips each have four simple lock pins to lock them in place and are fail safe (if they fail, they fail locked). The flaps have multiple failure modes, and not all are fail safe.
4. The wingtips can fold/unfold assymetrically with no concern. The flaps MUST extend and retract symmetrically, requiring complex sensors and redundant controls to ensure this ALWAYS happens.
5. The wingtips each have a simple single rotary actuator. The flaps have multiple segments and multiple actuators
6. The wingtips have a very simple rotary motion. The flaps have a complex motion that includes translation and rotation.at constantly varying ratios which requires a complex track/link system.
7. The wingtips are structurally and aerodynamically simple and if one or both wingtips are lost in flight the aircraft remains fully controllable. The flaps are much more complex structurally and aerodynamically. Lose a flap in flight and you're screwed.
8. The wingtips only need to fold to taxi off the runway and/or fit into a gate, so the consequences of a failure to fold are minor and at most an annoyance. The flaps need to extend to land and the consequences of a failure to extend are much more serious.
9. The wingtips unfold on the ground before becoming airborne so if there's a problem you know about it well before you even commit to flight. The flaps retract AFTER takeoff and MUST retract to continue the flight. If they fail to retract the flight must be aborted.
10. There's more, but this will suffice.

I'll let the reader decide which system is "safer", "more complex", "requires more safety measures", etc
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Old 26th Jul 2018, 19:14
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Originally Posted by KenV
A few points:
1. The wingtip only folds/unfolds on the ground. The flaps MUST extend and retract in flight.
2. The wingtips only have two positions. The flaps have multiple positions.
3. The wingtips each have four simple lock pins to lock them in place and are fail safe (if they fail, they fail locked). The flaps have multiple failure modes, and not all are fail safe.
4. The wingtips can fold/unfold assymetrically with no concern. The flaps MUST extend and retract symmetrically, requiring complex sensors and redundant controls to ensure this ALWAYS happens.
5. The wingtips each have a simple single rotary actuator. The flaps have multiple segments and multiple actuators
6. The wingtips have a very simple rotary motion. The flaps have a complex motion that includes translation and rotation.at constantly varying ratios which requires a complex track/link system.
7. The wingtips are structurally and aerodynamically simple and if one or both wingtips are lost in flight the aircraft remains fully controllable. The flaps are much more complex structurally and aerodynamically. Lose a flap in flight and you're screwed.
8. The wingtips only need to fold to taxi off the runway and/or fit into a gate, so the consequences of a failure to fold are minor and at most an annoyance. The flaps need to extend to land and the consequences of a failure to extend are much more serious.
9. The wingtips unfold on the ground before becoming airborne so if there's a problem you know about it well before you even commit to flight. The flaps retract AFTER takeoff and MUST retract to continue the flight. If they fail to retract the flight must be aborted.
10. There's more, but this will suffice.

I'll let the reader decide which system is "safer", "more complex", "requires more safety measures", etc
KenV: Now that is a pretty overwhelming set of arguments. I guess we will see if they all hold true in practice once the 777X is flying. But one more thing. I had heard that wing-folding was to be an option on the 777X. If this is correct, it would be interesting to hear how many frames are being ordered with, and how many without. That might indicate a bit the confidence level that airlines have in the mechanism -- or the tightness of the typical gates at which they expect to park these planes.
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Old 26th Jul 2018, 19:32
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Originally Posted by SeenItAll
KenV: Now that is a pretty overwhelming set of arguments. I guess we will see if they all hold true in practice once the 777X is flying. But one more thing. I had heard that wing-folding was to be an option on the 777X. If this is correct, it would be interesting to hear how many frames are being ordered with, and how many without. That might indicate a bit the confidence level that airlines have in the mechanism -- or the tightness of the typical gates at which they expect to park these planes.
No, it's not an option on the 777X - the folding wingtip is basic. There is too much confusions with the originally proposed 777 folding wing (~1990) which was never implemented.
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Old 27th Jul 2018, 02:29
  #125 (permalink)  
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I ain't flying on anything that has folding wings.

In a previous life I missed a wings folding event by 24 hours. The result is quite terminal, I know.

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Old 27th Jul 2018, 02:49
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Originally Posted by ImageGear
I ain't flying on anything that has folding wings.

In a previous life I missed a wings folding event by 24 hours. The result is quite terminal, I know.

IG
How about a folding wingtip which does not affect the basic controllability of the airframe is extended or retracted asymetrically?
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Old 27th Jul 2018, 04:54
  #127 (permalink)  
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Asymmetrically?, which buffoon is going to flight test that? I still would not get on the damn thing. I guess I won't be going sub-orbital either. Engineers are like Doctors and Accountants, lots of talk, big bills, and often pushing you off their bleeding edge.

..and don't now get me going about FBW, do I ride airbus - yes, do I also try hopelessly to push it into a cold dark cell in the deep inner core of my brain, absolutely.

IG

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Old 27th Jul 2018, 07:21
  #128 (permalink)  
 
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I agree with the flaps with respect to complexity, but I disagree that they are good performers. There is an awful lot of wear and tear on the flap hinges and actuation system for practically any aircraft, there is a lot of maintenance involved.
To get the turn back to the A380, its flap system is significantly simpler than that of the 747, still it is more efficient. There are a lot of details where the A380 is well ahead of its competitors of its time. This advantage by now has been deleted with the 787 and with Airbus own A350. Their flap system is even simpler.

The flaps are mandatory, the folding wing is a choice. You cannot avoid the complexity of the flap system, but you can avoid the folding wing. Especially when you have a high capacity aircraft which will only operate from large airports. Probably on many airports you can manage to park 777X between 787s or similar, so that the additional 3 meters do not hurt.
Airbus intentionally accepted the restriction in wing span for the A380, especially after they have learned Boeings lesson that no operator selected the optional folding wing on the 777. It costs some efficiency, but it saves a lot of complexity and extra weight.
A 777 with "permanently folded wings" (aka Winglets) would be only marginally less efficient, mainly depending on the exact mission they will finally operate.

We will see how the 777X outsells the A380. Or not. The time of the very large aircraft may simply be over. Today you can have range without size, you can have higher flexibility with less risk. It might not be a technically (i.e. DOC based) decision to go for smaller aircraft. It looks like the 777X just like the A380 only makes sense for the gulf hubs, high capacity airports far away from anybodies destination, where you need size and range. The 777X will probably never become the Queen of the north Atlantic, maybe an A321 XULR will be instead...
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Old 27th Jul 2018, 07:46
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Originally Posted by Mk 1
How about a folding wingtip which does not affect the basic controllability of the airframe is extended or retracted asymetrically?
Having one retract and the other not will always cause a lift asymmetry. If it doesn't affect the aircraft at all, you might as well just leave the entire wingtip off in the first place.

What I think will happen: For the next round of weight savings on the 777X, the movable tip will be moved from a fixed item to an optional item, removing the weight penalty from the performance guaranties. As no airline will want to accept the penalty, it will die a quiet death. I think long range aircraft are not the best application for this technology, due to the increased payload-range penalties. They also do not spend a lot of time on the ground.

One thing I must say for Boeing, is that at least they are taking the effort now of trying to certify it, so maybe it will work in the future. With the previous tip on the original 777, any airline wanting the folding tip basically had to arrange and pay for the certification as well, clearly indicating Boeing did not want anyone to actually take the option.
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Old 27th Jul 2018, 07:58
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I don't see what all the fuss is about:



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Old 27th Jul 2018, 08:43
  #131 (permalink)  
 
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..and don't now get me going about FBW, do I ride airbus - yes, do I also try hopelessly to push it into a cold dark cell in the deep inner core of my brain,
You do realise that Boeing and Embraer are also FBW? The difference is that they both kept a conventional control "wheel".
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Old 27th Jul 2018, 08:56
  #132 (permalink)  
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Originally Posted by ImageGear
Asymmetrically?, which buffoon is going to flight test that? I still would not get on the damn thing. I guess I won't be going sub-orbital either. Engineers are like Doctors and Accountants, lots of talk, big bills, and often pushing you off their bleeding edge.
If it ever gets off the ground, (excuse the pun), it will surely have a lock-out system whereby either both work or neither work? A simple dynamic pressure sensor, in the leading edge of the tip, could lock-out any tip movement whilst the aircraft is doing more than, say, forty knots? If the dynamic sensing on one side fails then the asymmetric lock-out function should operate?
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Old 27th Jul 2018, 09:21
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Rather than a folding wing, why not a partial swing-wing, say one that swings at approx 2/3 of the way out? Fully forward for landing, swung partly back for cruise, all the way back at the gate? I know it would mean extra weight, though.
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Old 27th Jul 2018, 09:52
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Originally Posted by DaveReidUK
I don't see what all the fuss is about:



Parking on (or actually in) aircraft carriers is at a slightly higher premium than at most international airports. Also these short range aircraft with a thrust to weight close to one have ejection seats and the 777X probably does not. ;-)
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Old 27th Jul 2018, 09:54
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Originally Posted by parabellum
If it ever gets off the ground, (excuse the pun), it will surely have a lock-out system whereby either both work or neither work? A simple dynamic pressure sensor, in the leading edge of the tip, could lock-out any tip movement whilst the aircraft is doing more than, say, forty knots? If the dynamic sensing on one side fails then the asymmetric lock-out function should operate?
Sound like the design of the DC-10 cargo door: https://en.wikipedia.org/wiki/McDonn...ajor_accidents
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Old 27th Jul 2018, 10:03
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You do realise that Boeing and Embraer are also FBW? The difference is that they both kept a conventional control "wheel"
I choose to ride FBY because there is little alternative today unless I go for the three stops option, and in any case I have conditioned myself to think that FBY is just a marketing sell and is only a figment of my imagination. Please don't tell me otherwise.

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Old 27th Jul 2018, 10:08
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Originally Posted by tdracer
No, it's not an option on the 777X - the folding wingtip is basic. There is too much confusions with the originally proposed 777 folding wing (~1990) which was never implemented.
Further on that, the unfolded wingspan is too much for the everett assembly line.
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Old 27th Jul 2018, 10:47
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Originally Posted by Volume
We will see how the 777X outsells the A380. Or not. The time of the very large aircraft may simply be over. .
We really don't have to wait. Boeing has already received 326 orders for the 777X. Airbus has received 331 orders for the A380. So essentially already the same sales. 777X is not yet in production. A380 has been in production for over a decade. 777X was specifically designed to replace the 777-300ER, which will begin reaching the end or their economic service lives a few years after 777X begins deliveries. There were over 830 777-300ER ordered, so a pretty large market. That's also when many 747-400 reach the end of their service lives, which adds further to the size of the potential market. 777X is a much better replacement candidate for both than the A380. That being said, A350-1000 will compete in the bottom end of that market, so not all of that market will go to Boeing. But the likelihood that A380 will capture a significant portion of that market is close to nil. A380 operates in its own market, and its a niche. A niche market that is apparently shrinking, with both the 777X and A350 nibbling away at it.

Last edited by KenV; 27th Jul 2018 at 11:01.
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Old 27th Jul 2018, 10:51
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Originally Posted by unexplained blip
Further on that, the unfolded wingspan is too much for the everett assembly line.
Then just fit the raked wingtips as the last item, when it is outside the door. They should be line replaceable anyway.
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Old 27th Jul 2018, 10:55
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Originally Posted by unexplained blip
Further on that, the unfolded wingspan is too much for the everett assembly line.
Keep in mind that the folding portion is the raked wigTIP. The wingtip does not need to be installed inside the assembly area and can be installed outside, just as the engines are installed outside on many Boeing aircraft. But you do make a good point in that the 777X with folded wing tips can be handled just like the 777 today. No need to change either the final assembly area or the flight line to accommodate 777X. And maybe why the folding wingtip is standard and not an option.
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