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May 27, 2024
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Its not only Boeing that is looking at folding wingtips.  Airbus is at it too, but their solution folds down rather than up.2015-10-26_8-09-33Airbus’ patent application can be seen here.  As the image suggests, it looks like this idea is focused on a twin engine aircraft.

Airbus points out that larger aircraft need longer wings but this runs into the airport gate box size limitation.  Which is of course the same thinking Boeing has.  But then they point out that the the upwards folding wing “requires heavy actuators and/or locking systems”.  They also point out that during flight the forces of flight are “urging the wing to the folding position”.  Hence their interest in downward folding tips.

These are interesting points Airbus makes.  Of course Boeing could point out that the upward folding wing offers considerably less opportunity for “ramp rash”.  It is, unfortunately, true that vehicle drivers around aircraft are often clumsy and hit aircraft.

Either way, now that both big OEMs are moving towards folding wingtips, the path ahead is clearer about this concept.  We know why Boeing is doing this.  But why would Airbus be doing this?  Might this idea be signalling a growth model A350?

19 thoughts on “Airbus’ new winglet patent

  1. The one model that Airbus currently has that would benefit most from this is the A380.

    If they were for putting new engines on, and decided to revisit the wing in a substantial way, this could go a long way to reducing induced drag.

  2. This is not one of Airbus’s brightest ideas.
    Folding the wing up is a sound and proven solution, Boeing is on the right track. US Navy, Royal Navy, and French Navy carrier deployed aircraft have had up-wards folding wings for decades, so more aircraft can fit on aircraft carriers. The concept goes back before WWII. These fighter, bomber, recon, cargo, and AWACS aircraft all are subjected to more aggressive maneuvering and “G” forces than commercial aircraft will ever face.
    To my knowledge, there has never been a folding wing locking latch failure because of maneuvering. Yes, there have been some because of combat damage, but commercial airliners generally don’t go there.
    Airbus needs to go back to the drawing board.

  3. All I see in that design is ground damage. Would love to know the ground damage statistics from the new 737 scimitar winglets. I’ve seen a few flying around without the lower piece, so apparently it is not a problem by design, but that is not the case for a folding wingtip.

  4. OK, now that it did work.

    Its not a great idea I agree, but as you can see from image above, there is space for a downward fold. Although prob not on A350.

    Also, a downward fold should be a little lighter. Its not an option on fighters as they don’t have the ground clearance a large wingspan with dihedral gives.

    To be honest, given there are only 4 ways you can fold a wingtip, up, down, forward or backward, I don’t really see how this is non-obvious and thus patentable. Seems a bit like apple’s patent on a rectangle with rounded corners to me. Daft.

  5. Very interesting concept: Keep it simple, stupid (KISS)!

    Since the wing is swept, the hinge line is thus at an angle to the direction of flight. The wing tip device therefore presents a larger frontal area when it is on the ground configuration than when it is in the flight configuration.

    For take-off, the wing tip device is first configured in the ground configuration. The Aircraft then commences the take-off run. There’s no lock on the wing tip device in this configuration, and the hinge is sufficiently free-moving to allowing the wing tip device to rotate from the ground configuration towards the flight configuration by virtue of the drag acting on the device. As the speed of the aircraft increases and the device rotates upwardly, the drag decreases but the device begins to generate sufficient lift to assist in moving itself to the flight configuration. The actuator is also used to assist in this movement, until the wing tip device reaches the flight configuration. At that point, the lock is engaged to prevent the wing tip device falling back down under negative-g flight conditions.

    For landing the process is reversed. Namely the Lock is disengaged (for example at the same time the landing gear is deployed). As the angle of attack of the aircraft decreases as the nose is brought down, the lift/drag forces on the wing tip device decreases to the point that gravity overcomes it and the tip returns to the ground configuration. In this scenario it is not actually necessary to use the actuator at all.

  6. @kc135topboom

    I think it’s a great idea! As i said gown-thread; keep it simple, stupid (KISS)!

    There’s a reason why military-type folding wings have not found much traction on the civilian side. First, they require heavy actuators and locking mechanisms for wing deployment and to ensure a secure lock while in flight. 2nd, due to the aerodynamic lift forces acting upon the wing in the direction towards the wing tip’s folded position, there’s always the risk of the wing tip folding upwards. 3rd, these highly maintenance-prone devices are obviously acceptable for jet fighter operations on carriers – where airframe hours are at most, a few hundred hours per year – but not for civilian airliners having at least 10 times the number of airframe hours per year.

  7. My point was, this is technology that goes back to before WWII. There have been improvements, and yes, on Naval Aircraft the systems are heavy. But they are reliable, and not as maintenance intense as you imply. Boeing choose a similar, but newer technology for it’s B-777X folding wing system ( a major improvement over the original optional B-777 folding wing option of the 1990s) to be used in the carbon-fiber-reinforced polymer wing. This is the lightest (weight), but longest wing ever used on a B-777 variant. Only about 12′ of each wingtip on the B-777 will fold up, That is not very much taller than the Aviation Partners Boeing blended winglets (about 10′) on the B-767. Most of the folded up B-777X wingtip is actually the raked wingtip, so it is relatively light in weight.

  8. Naval aircraft – typically the ones that require folding wings – have movable surfaces on the folded wing tips. They also have low ground clearance, so it’s pretty obvious why you wouldn’t want to fold a wing down on a carrier deck. Now, the original 777-200 folding wing option from the 1990s also had movable surfaces on the leading and trailing edges of the wing – in contrast to the relatively simple folding raked wing tips on the 777X. Due to the complexity of moving surfaces on a folded wing tip, this was probably why no airline customers of Boeing ever took up the option. However, you point was: “Folding the wing up is a sound and proven solution, Boeing is on the right track” – using upwards folding wings on naval aircraft in order to bolster your point. My point is that the experience from naval aviation will have little, or no bearing on the future of civil aviation, due to the cumbersome and heavy actuators and locking mechanism and the control surfaces. In contrast, the Airbus patent allows for much simpler actuation and locking devices than the Boeing method which has to work against gravity.

    During flight, with the wing tip device in the flight configuration, the bending moment generated about the hinge line is preferably reacted against the abutment surface of the wing. Thus, the bending moment is preferably no taken by an actuator or locking mechanism but is instead taken up by the primary wing structure.

    For sure, folding wings per se, is the right move forward, but I’m not sure if the relatively skimpy folding wing tips on the 777X demonstrates what’s possible. For example, assuming that the raked wing tip is a perfect triangle – a folded wingtip that’s double in length and chord will have 4 times the area – and consequently, it will be much heavier and require much more robust actuators and locking mechanisms. The folded wing tips on the 777X measures 3.75m in length (i.e. an increase from 3.4m as originally envisaged)*. Now, the ground clearance on the outer wing on the A380 and A350 is, respectively, about 6.5m and 7m. Assuming that you’d need at least 1.5m of ground clearance for the Airbus patented downward folding wing tip – a folding wing tip on these aircraft could have a length of at least 5m in order to ensure a sufficient ground clearance. Interestingly, the wing tip device may take a number of forms – according to the invention. Hence, it could take the form as that of the current A350 wing tip – namely an upwardly extending winglet (i.e. in the flight configuration). Also, because the hinge line is oriented at angle to the flight direction, an upwardly extending winglet would not add to the span when in the ground configuration. If the height of the upwardly extending winglets were, say, 3m – and assuming that the A350 wing tip device is similar to a raked tip where the latter adds about 80 percent in the effective aspect ratio calculation – you would add 2 x (5m + 2.4m) = 14.8m of increased wingspan to the wing. So, it may look as if both the A350 and A380 wings would be able to have wing tip devices that could be up to 4 times as large as the one that’s going on the wing of the 777X, while having much lighter actuation and locking devices that would be required for a 777X-style folding raked wing tip.

    * http://www.aspireaviation.com/wp-content/uploads/2013/12/777X-airport-compatibility.pdf

  9. A downward hinged wing tip device on a large aircraft like the A380 wouldn’t necessarily be more exposed to damage from “ramp rash” than the engines. Like the engines, the wing tip devices would be large and noticeable. Under an A380 wing there should be sufficient space between the outer engines and the downward folded wing tip for the safe operation of ground vehicles.

  10. The A-380, nor the B-747-8 don’t need folding wingtips. But if they did, the ground clearance on a downward folding wingtip would depend where on the wing the hinge for the folding equipment is. BTW OV-099, engines and cowlings suffer ramp rash everyday. Also, there is a reason why the airlines have their aircraft fully retract the flaps and slats while approaching the gate….ramp rash.

  11. KC, induced drag would be reduced by at least 25 percent on the A380 if the wing would have 14.8m of additional wingspan. The induced drag reduction alone would lead to a reduced fuel consumption of at least 10 percent. That’s equal to what you’d get from a all new state-of-the-art engine in 2020.

    As for ramp rash, are the engines and cowlings on the Qantas and Emirates A380s operating into DFW suffering ramp rash every day – or is ramp rash during loading and unloading really much more of a concern for narrow bodies that are landing eight or 10 times a day – versus one or two for a wide body.

  12. Yes, NBs are more at risk for ramp rash than WBs are.
    If a 45′ increase in the A-380 wingspan were feasible, I’m sure Airbus would consider it. To my knowledge, they have not.
    I know of no ramp rash incidents at DFW to the engines on the A-380 or B-747. But about 10-12 years ago the #3 engine cowling of a LH A-340 was damaged by a cargo bin. Likewise the engine cowling of a DL B-767 was also damaged by ramp rash, years before the A-340 incident.
    But DFW is just one airport. There are hundreds of airports around the world that handle WBs on a daily bases, and engine/cowling incidents have occurred at some of them.
    I think you and I are starting to get to far away from the subject here, the downward fold of Airbus’s proposed wing fold system. At the end of the day it will be the airline customers who will decide to order, or not order this option based on their own evaluation.

  13. KC, I wouldn’t be too surprised if Airbus is currently contemplating a massive increase in wingspan for the A380. IMO, they’re not just going to do a “neo”.

    As for ramp rash, I think it’s really more of a non-issue for a very large aircraft sitting in a 80m x 80m box, and where the engines are not in close proximity to the loading operations of cargo etc. Now, if ramp rash where to occur on a composite downward folded wingtip it would probably be easier to repair than ramp rash on a composite fuselage, since the wing tip obviously wouldn’t be pressurised.

  14. It may look as if Airbus is seriously studying a larger version of the A350-1000. I wouldn’t be too surprised if Airbus would be contemplating an A340-600-type chord-wise wing insert (i.e. insert equal to 2 x 0.635m; or the equivalent of two fuselage frames), and two large downward folded wingtips – increasing span to well over 75m and wing area to well over 550m2. In contrast the wing area of the A350-1000 is 460m2.

    Airline sources say Airbus is exploring more seriously than before a larger version of its A350-1000 widebody jet with a capacity of up to 450 seats to counter the latest Boeing 777, probably powered by the next generation of “UltraFan” engines from Rolls-Royce.

    At the same time, they say it may hold off on upgrading its slow-selling 544-seat A380 as it gains a clearer idea of costs, keeping open the option of producing an even bigger version later with 100 more seats to keep a gap with the A350 and 777.


  15. Looking at the drawn picture, above, it looks like the folded wingtips hang down as low as the bottom of the engine cowlings. If that is represented as a 4 engine airplane, that would be the inboard engines.
    Ramp rash on the wingtips could be very serious. On many airplanes the pressurizing scoop for the fuel vent system is there. Additionally, many airplanes have their magnetic compass sensors on the wingtips to get the sensors as far away from steel parts (ie. landing gear) as possible. Damage the sensor on either wingtip ( a sensor is on each one), and your airplane is OTS. The red and green navigation lights are also found on the wingtips, damage either one, and you cannot fly outside of day VFR. The Nav Lights are required for IFR flying. You can fly with a broken wingtip strobe light, as long as the upper and lower anti-collision lights are operable.
    I still think this is a dumb idea.

  16. Excellent point, OV-099. Airbus needs desperately to compete with the B777-9X. The A350-1000 looks a bit weak for this. Therefore, an A350-1100 becomes necessary. The current -1000 wing (and engine combo) will NOT get the job done. A significant folding wingtip might be the answer, but I still do not like that it would fold down. Despite the potential weight savings from the locking mechanism, the ramp rash component could significantly affect dispatch reliability.

    The problem for an A350 with folding wingtips is that Airbus would have three different wings within one aircraft family. That can’t be efficient from a production standpoint. By contrast, Boeing offers five different WB aircraft with only two wings – B787-8/9/10 and 777X-8/9. This is the type of design and production choice which causes Boeing to be roughly twice as profitable as Airbus. Boeing plans and innovates while Airbus reacts. They always seem to be a day late and a dollar short in their WB market moves. Their only big WB success to date is the A330, which was really an afterthought of the A340 program. Dare I suggest a bit of luck involved?

    The A380 has plenty of wing as is, even for a stretched -900NEO. It does NOT need a folding wingtip. What it needs are more efficient engines. A folding wingtip might help with airport compatibity, but I think that ship has sailed. Other than EK, the rest of the industry has moved on from the A380. It’s all about big twins now.

  17. KC, the vent tank is in the outer portion of the wing box and not in the winglet. On the 757, for example, the wing box ends just short of the wing tip. In contrast, on the A350 wing the winglet unit consists of the wingtip (wing extension) and the attached winglet, and it sweeps 5.2m from the attachment point to the outer wing box and to the rear tip. By locating the magnetic compass sensors in the wing tip just outboard of the hinge line, they should be well out of “harms way”. As for navigation and strobe lights, you’d probably have a second pair of navigation and strobe lights on the fixed wing – located between the hinge line and the slat on the leading edge and between the hinge line and aileron on the trailing edge. Anyway, this seem to be much ado about nothing. As I’ve already indicated, ramp rash seems to be a very infrequent occurrence on large wide bodies, and if there were to be serious ramp rash on a downward folded wingtip, you’d just remove the aircraft from service for a few days, repair the structure and replace damaged components – just like it’s done when anything is broken or damaged on an airliner.




  18. @Scratch

    I’m not talking about an all new wing, but about a chord-wise wing insert – similar to how it was done on the A340-500/-600. The insert wouldn’t be “tapered”, though, as was the case on the A345/A346 wing, where the tapering increased the sweep angle of the leading edge. The movable surfaces on the trailing and leading edges would be nearly identical to the ones on the A350-1000 – except for the the addition of a 7th slat on the leading edge.


    Apparently, Airbus is looking at a 450 seat derivative. That would mean 85m overall length and it would be 18 frames (x 0.635m) longer than the A350-1000. It’s interesting that the new airport being built in Dubai will have a box-size of 85m x 85m for Category F aircraft stands – in order to accommodate 85m long A360-1000Xs and A380-1000Xs? Of course, such a derivative would need a larger wing. IMJ, Airbus would very likely call this new aircraft (-family) the A360. The A360-1000X would be the 85m long model. The A360-900 might be 9 frames shorter, and would have an overall length of about 79.5m. This model would be the direct competitor to the 777-9. An A360-800 would be the URL model and have about the same fuselage length as that of the A350-1000. So, two families having the same fuselage and huge amount of commonality in the wing. Wouldn’t that be superior to the 787/777X – two families having virtually no commonality. Of course, over at the VeroVenia blog, the 787/777X combo will always be superior, right? As for the two OEM’s financials, I’m not sure if the situation for Boeing is as rosy as you’re claiming it to be if you look at the deferred costs of the 787.

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