olddominion727 From United States of America, joined Jan 2012, 336 posts, RR: 0 Posted (11 months 1 week 2 days 17 hours ago) and read 21618 times:
I am not going to profess to know much about science etc. But how come there are no winglets for the 777? Wouldn't it have the legs to fly further on less fuel? I thought that's why all of the newer commercial equipment have them?
"In testing by Boeing and NASA, raked wingtips have been shown to reduce drag by as much as 5.5%, as opposed to improvements of 3.5% to 4.5% from conventional winglets"
The 767-400, 787 and the 747-8 have the same type as well
ghifty From United States of America, joined Jul 2010, 758 posts, RR: 0 Reply 3, posted (11 months 1 week 2 days 17 hours ago) and read 21483 times:
I wonder how well the raked wingtip design will hold up against the 737 MAX's AT winglet. Or.. I assume the 737 MAX doesn't have raked wingtips (or the kind the B787 has) because of gate-space restrictions.
Stitch From United States of America, joined Jul 2005, 26705 posts, RR: 83 Reply 5, posted (11 months 1 week 2 days 16 hours ago) and read 21380 times:
Back in 2004, Boeing and Aviation Partners looked into winglets for the 777, but nothing seems to have come of it.
There just might not be enough frames to justify moving forward: while the 777-200ER was a strong seller, the 777-200 and 777-300 both delivered under 100 units, each. Compare this to the over 1000 757s and 767s delivered.
As for the 737, the P-8 does have raked wingtips, which were chosen in part, I believe, because they don't block the onboard sensors and because the P-8 spends much longer in cruise and that is where raked wingtips are most-advantageous.
jetjack74 From United States of America, joined Jul 2003, 7336 posts, RR: 52 Reply 6, posted (11 months 1 week 2 days 16 hours ago) and read 21362 times:
Quoting ghifty (Reply 3): I wonder how well the raked wingtip design will hold up against the 737 MAX's AT winglet. Or.. I assume the 737 MAX doesn't have raked wingtips (or the kind the B787 has) because of gate-space restrictions.
1337Delta764 From United States of America, joined Oct 2005, 5759 posts, RR: 2 Reply 7, posted (11 months 1 week 2 days 16 hours ago) and read 21134 times:
Quoting ghifty (Reply 3):
I wonder how well the raked wingtip design will hold up against the 737 MAX's AT winglet. Or.. I assume the 737 MAX doesn't have raked wingtips (or the kind the B787 has) because of gate-space restrictions.
Actually, the 737 MAX wingtip devices resemble a three-way hybrid of a blended winglet, raked wingtip, and wingtip fence.
The Pink Delta 767-400ER - The most beautiful aircraft in the sky
DocLightning From United States of America, joined Nov 2005, 16819 posts, RR: 57 Reply 8, posted (11 months 1 week 2 days 16 hours ago) and read 21104 times:
Quoting Stitch (Reply 5): As for the 737, the P-8 does have raked wingtips, which were chosen in part, I believe, because they don't block the onboard sensors and because the P-8 spends much longer in cruise and that is where raked wingtips are most-advantageous.
Why are raked wingtips better in cruise and winglets not as optimal for longer trips?
solarflyer22 From US Minor Outlying Islands, joined Nov 2009, 395 posts, RR: 0 Reply 9, posted (11 months 1 week 2 days 15 hours ago) and read 20930 times:
Raked wingtips incur slightly less drag than winglets and have the added bonus of not needing to be checked as often (according to some other forum threads). Winglets are apparently better at high cycle (lots of take off and landings) vs raked wingtips which are better for long distance cruise (ie 777). 787 and 748 also fall into that category.
Winglets have the advantage of advertising (great sign post) and can be retrofitted. They also reduce gate space. I would not be surprised at all if the P-8 raked wingtip is on the 737 max but that wing is much stronger and heavier than a regular commercial plane so the entire design cannot be used. More likely, they'll do something similar to what Airbus does. A vertical element and smaller down element.
Personally, I would rather see a flexible but strong wingtip that can provide more lift at low speed (i.e. take off and landing) and then sweep backward above 300 knots (i.e. at high cruise). I think if you use a strong woven material like Kevlar like it would work.
atcsundevil From United States of America, joined Mar 2010, 667 posts, RR: 1 Reply 10, posted (11 months 1 week 2 days 15 hours ago) and read 20928 times:
Winglets on a 777-200 and -200ER would not improve performance enough to justify the costs. They came without winglets or raked wingtips because the -200 and -200ER were developed prior to their widespread use. As it is, it's a pretty well-designed aircraft aerodynamically. API looked into it a few years ago, but my understanding is the ROI wouldn't have been worth it to bother with flight testing.
Now that some of the 777-200s and -200ERs are getting old, my guess is there will be more research into this to improve their efficiency, thus allowing them to stay in service longer. I wonder if they'll come up with a way to install raked wingtips featured on the rest of the 777 line.
1337Delta764 From United States of America, joined Oct 2005, 5759 posts, RR: 2 Reply 11, posted (11 months 1 week 2 days 15 hours ago) and read 20870 times:
Here is the 737 MAX wingtip device:
A hybrid of a blended winglet, wingtip fence, and raked wingtip.
The Pink Delta 767-400ER - The most beautiful aircraft in the sky
Stitch From United States of America, joined Jul 2005, 26705 posts, RR: 83 Reply 13, posted (11 months 1 week 2 days 14 hours ago) and read 20667 times:
Quoting cheeken (Reply 12): Is it just me, or does that look like an enlarged version of the Airbus winglets on the A320s and A380s?
Those wingtip devices are fences and are quite different in geometry from the 737 MAX.
The 737 MAX wingtip shares a closer relationship to the MD-11's.
LAXintl From United States of America, joined May 2000, 22038 posts, RR: 51 Reply 14, posted (11 months 1 week 2 days 14 hours ago) and read 20538 times:
Something might be around the corner...
From the desert to the sea, to all of Southern California
I think the anti-drag was built into the wing, however. Different from the raked winglets but still designed as such. I highly doubt we'll see actual winglets on the early models of the T7.
Quoting 1337Delta764 (Reply 11): A hybrid of a blended winglet, wingtip fence, and raked wingtip.
Kinda resembles a larger version of the Airbus winglet
travelhound From Australia, joined May 2008, 556 posts, RR: 0 Reply 16, posted (11 months 1 week 2 days 13 hours ago) and read 20427 times:
Quoting Stitch (Reply 5): As for the 737, the P-8 does have raked wingtips, which were chosen in part, I believe, because they don't block the onboard sensors and because the P-8 spends much longer in cruise and that is where raked wingtips are most-advantageous.
You would think 737BBJ's would be better suited to the raked winged tips as the custiomers tend to fly longer trips?
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 17, posted (11 months 1 week 2 days 12 hours ago) and read 20248 times:
Quoting ghifty (Reply 3): I wonder how well the raked wingtip design will hold up against the 737 MAX's AT winglet.
Better. Aerodynamically, it's always better to go out (tip extension) than up (winglet). You only go up (and down) if there's some other constraint: wingspan, retrofit capability, etc.
If you don't have another constraint, you go out...that's why the most recent designs (787, 747-8, A350) all went with raked tips.
Quoting ghifty (Reply 3): I assume the 737 MAX doesn't have raked wingtips (or the kind the B787 has) because of gate-space restrictions.
DocLightning From United States of America, joined Nov 2005, 16819 posts, RR: 57 Reply 18, posted (11 months 1 week 2 days 11 hours ago) and read 19541 times:
Quoting solarflyer22 (Reply 9): Winglets are apparently better at high cycle (lots of take off and landings) vs raked wingtips which are better for long distance cruise (ie 777). 787 and 748 also fall into that category.
Yes, but... why? What about raked wingtips make them better for cruise? What about winglets make them better for takeoff and climb? Why doesn't Airbus really use raked wingtips?
I know that Boeing has offered a PIP for existing 777's that replaces the vortex generators on the upper surface of the wing with smaller, more streamlined ones from the 737NG wing. It reprograms the outboard aileron to droop down by two degrees, which improves wing loading and twist. It also replaces the Ram Air intake with a more aerodynamic profile. Offers 1-1.5% improvement in performance.
Boeing's 777 test crew told me that winglets were considered, but that they would have needed to be extremely tall to be worth the effort, and the idea was dropped.
Loran From Germany, joined Jul 2005, 436 posts, RR: 2 Reply 20, posted (11 months 1 week 2 days 8 hours ago) and read 17093 times:
Quoting tdscanuck (Reply 17): Aerodynamically, it's always better to go out (tip extension) than up (winglet). You only go up (and down) if there's some other constraint: wingspan, retrofit capability, etc.
Thats the key point. Drag is a function of the wing's aspect ratio. So the higher the aspect ratio, the lower the drag. That's why modern gliders have extremely large wingspans with a short chord. Hence raked wingtips contribute to a higher aspect ratio while generating lift whereas winglets do not provide as much additional lift. Of course other factors contribute such as weight, cost, gate clearance, etc.
On the A380 airbus went for wingtip fences so that it would not increase the length of the wing which would have caused a problem with space when the aircraft was at a gate.
SLCPilot From United States of America, joined Aug 2003, 529 posts, RR: 3 Reply 23, posted (11 months 1 week 2 days 5 hours ago) and read 15033 times:
Quoting EGLL (Reply 22):
Quoting DocLightning (Reply 18):
Why doesn't Airbus really use raked wingtips?
On the A380 airbus went for wingtip fences so that it would not increase the length of the wing which would have caused a problem with space when the aircraft was at the gate.
It's also safer for people in buildings near the airport!
connies4ever From Canada, joined Feb 2006, 3857 posts, RR: 13 Reply 24, posted (11 months 1 week 2 days 4 hours ago) and read 14739 times:
Quoting tdscanuck (Reply 17): Better. Aerodynamically, it's always better to go out (tip extension) than up (winglet). You only go up (and down) if there's some other constraint: wingspan, retrofit capability, etc.
If you don't have another constraint, you go out...that's why the most recent designs (787, 747-8, A350) all went with raked tips.
What about structurally ? The longer a high aspect ratio wing gets, I would assume the bigger aeroelasticity issues you bring into the picture. You would counter this I suppose by beefing up the wing structure itself, and that puts a weight penalty into the picture. Winglets themselves impose a bit of a weight penalty, of course. I believe something around 150kg for the 73G might be fairly accurate.
Quoting Loran (Reply 20): Thats the key point. Drag is a function of the wing's aspect ratio. So the higher the aspect ratio, the lower the drag.
I always thought the winglet effectively increased the aspect ratio for a given wing. ?? Also, it tends to reduce "lost" air due to tip vortex generation, to my understanding.
richiemo From United States of America, joined Jul 2008, 195 posts, RR: 0 Reply 25, posted (11 months 1 week 2 days 2 hours ago) and read 13303 times:
Not only would winglets for the 777-200 and 200ERs be too tall but I think they determined that the wings were pretty well designed even without winglets, that the added weight would cancel out any advantage.
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 26, posted (11 months 1 week 2 days 1 hour ago) and read 11270 times:
Quoting connies4ever (Reply 24): What about structurally ? The longer a high aspect ratio wing gets, I would assume the bigger aeroelasticity issues you bring into the picture. You would counter this I suppose by beefing up the wing structure itself, and that puts a weight penalty into the picture. Winglets themselves impose a bit of a weight penalty, of course. I believe something around 150kg for the 73G might be fairly accurate.
Turning corners is a pain; if you're designing from scratch and you don't have some constraint (typically span) you go outwards (tip extension). They both add weight but the raked tip is easier to implement *if you design it in*. Retrofit is a different matter; this is why you see winglets much more commonly as retrofits (they don't impose as much of a structural margin demand on an existing wing).
Quoting connies4ever (Reply 24): I always thought the winglet effectively increased the aspect ratio for a given wing. ??
It does. So does a tip extension. Tip extensions produce more effective aspect ratio increase for their weight than winglets, which is why they perform better aerodynamically.
Quoting connies4ever (Reply 24): Also, it tends to reduce "lost" air due to tip vortex generation, to my understanding.
In aerodynamic speak, that the same thing as having a higher effective aspect ratio.
Quoting richiemo (Reply 25): Not only would winglets for the 777-200 and 200ERs be too tall but I think they determined that the wings were pretty well designed even without winglets, that the added weight would cancel out any advantage.
Any wing will always have less induced drag with properly designed winglets (or tips), regardless of how good it was to start with. The key is the trade off...is it better enough to pay for itself. That's a pretty easy trade to make for tips, pretty difficult for winglets.
What skews all the options around are all the other trades going on: cost, weight, retrofitability, gate spacing, flutter, etc.
JerseyFlyer From United Kingdom, joined May 2007, 458 posts, RR: 0 Reply 27, posted (11 months 1 week 2 days ago) and read 10981 times:
Quoting atcsundevil (Reply 10): They came without winglets or raked wingtips because the -200 and -200ER were developed prior to their widespread use.
The 777s were developed after the MD 11, B744, A330 and A340 which all had winglets.
My recollection is that the 777 wings were designed to bend upwards more in flight than those earlier designs to create a similar effect to winglets. That at least was the "spin" at the time.
amccann From United States of America, joined Mar 2008, 171 posts, RR: 0 Reply 28, posted (11 months 1 week 2 days ago) and read 10694 times:
Quoting connies4ever (Reply 24): What about structurally ? The longer a high aspect ratio wing gets, I would assume the bigger aeroelasticity issues you bring into the picture. You would counter this I suppose by beefing up the wing structure itself, and that puts a weight penalty into the picture.
Something interesting to think about in regards to raked wingtips is that because they produce additional lift they induce a moment on the wing. This moment is much greater with raked wingtips because the moment arm is much longer when the aerodynamic force of the wingtip is primarily vertical. This is the primary reason retrofitted airplanes have blended winglets and not raked wingtips. Blended winglets do not induce as great of a moment on the wing as do raked wingtips.
What one person receives without working for, another person must work for without receiving. - Ronald Reagan
pikachu From Bhutan, joined Feb 2002, 89 posts, RR: 0 Reply 29, posted (11 months 1 week 1 day 23 hours ago) and read 9149 times:
No discussion about the 777 and winglets is complete without knowing the aircraft has a supercritical wing. 757/767 has the same but early generation. Retrofits in progress now. Maybe another twenty years of computer advancement will find more efficiencies in the 777 wing design.
connies4ever From Canada, joined Feb 2006, 3857 posts, RR: 13 Reply 30, posted (11 months 1 week 1 day 22 hours ago) and read 8711 times:
Quoting amccann (Reply 28): Something interesting to think about in regards to raked wingtips is that because they produce additional lift they induce a moment on the wing. This moment is much greater with raked wingtips because the moment arm is much longer when the aerodynamic force of the wingtip is primarily vertical. This is the primary reason retrofitted airplanes have blended winglets and not raked wingtips. Blended winglets do not induce as great of a moment on the wing as do raked wingtips.
Exactly what I was trying to get at. So to counter the bending moment, the wing structure itself has to be stiffer, and not just around the wingtip, I'm thinking.
OTOH, Boeing apparently doesn't worry about the extreme bend in the 787 wing - that thing really bends a lot as Vr is reached, and then on landing it seems to flap a little. I wonder about fatigue issues, but I am sure Boeing thought this through.
1. The effective wingspan from a wing with upswept winglet is the wingspan + about 45% of the physical length of the winglet. A raked tip wing counts 80% of the raked tip length, ie the raked tip is more efficient for the same structural mass and wetted area of the tip device, it does build span and therefore landing fees and gatespace however.
2. CM which worked on the 777 and the 787 stated that a raked tip gives an overall lighter wing for the same effective wingspan not only because because a smaller device gives the same effect as a larger winglet but a raked tip induces less torsional forces to the wingbox then an upward going winglet.
3. In the thread CM also gave references to Airbus research with downward going winglets, they gave similar effects to an upward going winglet, had some wing bending moment advantage but decreases of course your free roll margin for landing and start.
4. The Max winglet uses this fact to get more effective wingspan for the same gate wingspan with a shorter downward going blade, it should also even out the torsional stress a bit.
5. The Airbus wingfence uses a different flow principle, at low speed it works as a deltawing (60° sweep angle and therefore vortex flow ) to keep some effect for start and landing, at cruise it has attached flow. The raked tip and winglet work with conventional aero for cruise, landing and start. At stall at least the raked tip uses it's high sweep angle to switch to vortex flow (not to have a total loss of tip lift when the wing stalls, you never want the tip to stall more then the root), if it didn't one would need to extend the slats to the raked tip area.
PlymSpotter From Spain, joined Jun 2004, 11125 posts, RR: 63 Reply 32, posted (11 months 1 week 1 day 20 hours ago) and read 6662 times:
A major consideration is the wingspan. The -200/200ER and -300 have a 60.9m span and the -200LR/300ER have a 64.8m span. In ICAO terms the maximum span for a Code E aircraft is 64.99m, anything above that and the aircraft would be considered Code F (A380/B748 territory) and would enter a whole different set of regulations which would significantly restrict where it could be used and what taxiways could accommodate it. So whilst a blended winglet could probably be developed for the earlier 777 versions within Code E it could not (unless the span somehow remained unchanged) be applied to the latest 200LR or 300ER without changing their operational parameters.
brilondon From Canada, joined Aug 2005, 3172 posts, RR: 1 Reply 33, posted (11 months 1 week 1 day 20 hours ago) and read 6421 times:
Quoting DocLightning (Reply 8): Why are raked wingtips better in cruise and winglets not as optimal for longer trips?
Quoting DocLightning (Reply 18): Yes, but... why? What about raked wingtips make them better for cruise? What about winglets make them better for takeoff and climb? Why doesn't Airbus really use raked wingtips?
I am not an engineer so this may be way off but the raked winglets on the longer range aircraft allow for the increased performance at altitude for long distances. Where as on the 737/757/767 the winglets they have increase lift over the non-winglet aircraft and thus, on short haul routes give a bigger savings economically.
DocLightning From United States of America, joined Nov 2005, 16819 posts, RR: 57 Reply 34, posted (11 months 1 week 1 day 19 hours ago) and read 6224 times:
Quoting brilondon (Reply 33): I am not an engineer so this may be way off but the raked winglets on the longer range aircraft allow for the increased performance at altitude for long distances.
But you just answered my question by repeating it. What specifically are raked winglets doing to airflow that makes them superior to winglets in cruise and what about them makes them inferior during climb?
connies4ever From Canada, joined Feb 2006, 3857 posts, RR: 13 Reply 35, posted (11 months 1 week 1 day 19 hours ago) and read 5696 times:
Quoting ferpe (Reply 31): 2. CM which worked on the 777 and the 787 stated that a raked tip gives an overall lighter wing for the same effective wingspan not only because because a smaller device gives the same effect as a larger winglet but a raked tip induces less torsional forces to the wingbox then an upward going winglet.
I find this to be interesting, I would have thought out of ignorance that by generating more lift there would be more torsion.
Quoting DocLightning (Reply 34): But you just answered my question by repeating it. What specifically are raked winglets doing to airflow that makes them superior to winglets in cruise and what about them makes them inferior during climb?
I think Ferpe's point #1 is your answer; for a given size the raked wing tip produces more effective lift, at the cost of a larger gate footprint.
Quoting ferpe (Reply 31): 1. The effective wingspan from a wing with upswept winglet is the wingspan + about 45% of the physical length of the winglet. A raked tip wing counts 80% of the raked tip length, ie the raked tip is more efficient for the same structural mass and wetted area of the tip device, it does build span and therefore landing fees and gatespace however.
brilondon From Canada, joined Aug 2005, 3172 posts, RR: 1 Reply 36, posted (11 months 1 week 1 day 19 hours ago) and read 5592 times:
Quoting DocLightning (Reply 34):
Quoting brilondon (Reply 33):
I am not an engineer so this may be way off but the raked winglets on the longer range aircraft allow for the increased performance at altitude for long distances.
But you just answered my question by repeating it. What specifically are raked winglets doing to airflow that makes them superior to winglets in cruise and what about them makes them inferior during climb?
Sorry. The raked winglets are more aerodynamic and produce less drag on the aircraft. It allows for the air flow to be less turbulent thus allowing for easier travel through the air and there for using less fuel. I am sure that there are engineers that can explain this better then me, but from my memory of high school physics, this seems to be the answer.
DocLightning From United States of America, joined Nov 2005, 16819 posts, RR: 57 Reply 37, posted (11 months 1 week 1 day 19 hours ago) and read 5531 times:
So what I am getting is that the raked wingtip is superior in all cases (given an original build), except that because it enlarges the span, for shorter-range aircraft that incur landing fees as a higher percentage of their operating costs, this would be disadvantageous.
Quoting connies4ever (Reply 35): I find this to be interesting, I would have thought out of ignorance that by generating more lift there would be more torsion.
As I understand it, winglets convert some vortex energy into forward thrust. Given that they extend well above the plane of the wing, that implies that they would cause a forward twisting moment at the wingbox. A raked tip, which increases lift, would increase bending moment but not necessarily torsion.
Quoting tdscanuck (Reply 17): If you don't have another constraint, you go out...that's why the most recent designs (787, 747-8, A350) all went with raked tips.
So my next question is: why are the tips raked? What is about raking them that makes them superior to just putting a triangular extension on the wingtip?
solarflyer22 From US Minor Outlying Islands, joined Nov 2009, 395 posts, RR: 0 Reply 38, posted (11 months 1 week 1 day 14 hours ago) and read 4165 times:
Quoting DocLightning (Reply 18): Yes, but... why? What about raked wingtips make them better for cruise? What about winglets make them better for takeoff and climb? Why doesn't Airbus really use raked wingtips?
Quoting DocLightning (Reply 34): But you just answered my question by repeating it. What specifically are raked winglets doing to airflow that makes them superior to winglets in cruise and what about them makes them inferior during climb?
I'm splaining it to you Lucy! Its the drag issue. Winglets induce more drag and are longer and add more weight to the frame than raked wingtips. Think of a winglet and if it were folded down. It would be an additional 7-9 ft of wing whereas a raked wingtip is only an extra 2-3 feet or so.
Winglets do help more at low speed where there is less drag and necessarily are more beneficial during take off and landing. Thats why high cycle aircraft (i.e. 737) benefit more because they spend more of their careers flying slow and taking off or landing. Raked wingtips don't help much during takeoff and landing.
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 39, posted (11 months 1 week 20 hours ago) and read 3312 times:
Quoting pikachu (Reply 29): No discussion about the 777 and winglets is complete without knowing the aircraft has a supercritical wing.
I'm not really sure how those two things are related...you can do winglets or raked tips on supercritical or non-supercritical airfoils.
Quoting connies4ever (Reply 30): OTOH, Boeing apparently doesn't worry about the extreme bend in the 787 wing - that thing really bends a lot as Vr is reached, and then on landing it seems to flap a little. I wonder about fatigue issues, but I am sure Boeing thought this through.
The bend is designed in. The aerodynamics guys figure out where they want the wing in flight, the structures guys figure out the build position ("jig position") so that the wing ends up where the aero guys wanted it once it's subject to flight loads.
Quoting DocLightning (Reply 37): As I understand it, winglets convert some vortex energy into forward thrust.
Strictly from an energy point of view that's sort of valid but it's aerodynamically dangerous territory. It's better to think of winglets as causing a weaker vortex in the first place.
Quoting DocLightning (Reply 37): So my next question is: why are the tips raked? What is about raking them that makes them superior to just putting a triangular extension on the wingtip?
It's the balance between lift and structural weight...as the chord goes down, the lift generated goes down. If you run the wing out as a triangle to a point, the point is basically making "zero" lift therefore not really doing anything. Hence you want to, at least, chop the point off. I think sweeping the leading edge back rather than having an abrupt corner gives you an aerodynamically cleaner setup (and probably helps with torsion) but that's somewhat out of my field.
connies4ever From Canada, joined Feb 2006, 3857 posts, RR: 13 Reply 40, posted (11 months 1 week 20 hours ago) and read 3203 times:
Quoting tdscanuck (Reply 39): Quoting DocLightning (Reply 37):
As I understand it, winglets convert some vortex energy into forward thrust.
Strictly from an energy point of view that's sort of valid but it's aerodynamically dangerous territory. It's better to think of winglets as causing a weaker vortex in the first place.
Thinking about this aspect, your explanation makes more sense to me.
ferpe From France, joined Nov 2010, 1781 posts, RR: 57 Reply 41, posted (11 months 1 week 19 hours ago) and read 3091 times:
US Patent 5039032 is the first basic B patent on the raked wingtip, it gives the reason for the high sweep of the forward surface:
- to avoid wingtip stall without having to go to the complication of slats.
The sweep angle gets to the area where a stable wintip wortex is formed at high AOA from the leading edge like for a deltawing aircraft and therefore the rake tip also works in start and landing without any leading edge device to increase it's AOA tolerance.
Sponsor Message: 
From United States of America, joined Jan 2012, 336 posts, 
From United Kingdom, joined Oct 2010, 19 posts, 
From Switzerland, joined Oct 2006, 21481 posts, 
From US Minor Outlying Islands, joined Nov 2009, 395 posts, 
From Singapore, joined Feb 2010, 48 posts, 
From Japan, joined Mar 2012, 4965 posts, 
From Australia, joined May 2008, 556 posts, 
From Canada, joined Jan 2006, 12709 posts, 
From Germany, joined Jul 2005, 436 posts, 
From Bhutan, joined Feb 2002, 89 posts, 
From France, joined Nov 2010, 1781 posts, 
From Spain, joined Jun 2004, 11125 posts, 
Printer friendly format 
