winglets- whats the point in not having them!!
 

hello all, i hope someone may be able to enlighten me on a question i have been asking myself!

Taking into account that winglets singnificantly reduce the amount of drag that is created on the wing tip hence increasing fuel efficency hence more money why aren't all a/c equipped with them!?!

I assume it will have something to do with stability or maybe for structural reasons... I know it is potentially a silly question but i cant come up with solid answer!

Thanks

On a new design, the wings may be sufficiently advanced that winglets don't make an appreciable difference.

On an older design (eg 727), it may be a matter of not being able to recover the cost of designing, certifying and installing winglets.

Notice that the 777 and 787 have simpler designs (raked wingtips) and older airplanes have the horrific looking blended winglets that seem to be in vogue nowadays.

They add weight. They are an addition to an a/c, hence costly to acquire and install. Today's iterations are generally not tunable, they cannot be optimized through a wide speed range, limited to generally, cruise.

They stress the wing, adding more weight to accomodate added root and spar strength. They can hit obstacles on the ground. Probably more reasons...

winglets!
 

It all comes down to the aspect of the wing
If the wings are able to create more lift to drag ratio the wings don't require winglets, rather becomes a added weight to the wings than being a performance feature.

I understand that winglets can REDUCE the demonstrated crosswind landing/takeoff component.

And on some a/c their economic benefit only becomes apparent on flights of greater than a couple of hours.

Some suggestions -

(a) wingtip treatment is an alternative, but generally not as good, way of getting what you get with a longer wingspan.

(b) we have a massive investment, worldwide, in airport infrastructure

(c) for the recent larger aircraft, wingtip treatment is a far cheaper alternative to not be able to get into existing aerobridges

(d) for smaller aircraft .. marketing .. they look good/modern/pretty/technologically with it/etc ... pick your choice

(e) as an add on there are structural penalties especially in fatigue but that may be a far better option than a very expensive wing redesign ?

(f) and, as Stallie suggests, not really a proposition for short range ops

Well, there is certainly a can o wahtever.

The wing design must be balanced. There is an optimum wingspan for the ac config...
but that is optimum...

while the optimum wingspan for fuel efficiency at flight is X (that also depends on optimum) The wingspan must be able to work with all of the settings, and access, for it all to work.

With the 737, the wingspan optimum wingspan for each wing, ends up to be about 6 feet longer that the ac has. This is a function of better design software than 20 years ago, but also as a balance.
If the wingspan on the 737 were extended to the new optimum, the ac would no longer be a CAT C aircraft. Hence, it was found, that if you turn the wingtip up, you had an 'equivalent' wingspan, the software showed reduced drag, and therefore...better fuel efficiency.
But this was all based on the average model, of the wing section in flight.

So, what you really needed was more of a variable section, that would better perform though more phases of flight.

While the Airbus T and the end of the wing was really good, the software models didnt really understand how to properly calculate the results, hence a square peg in a round hole.
The recent 737 MAX winglet, appears to optimize more flight conditions, but in reality, still appear to use the same CFD models, which get you so far, but are still 40 year old technology.

In reality, we are seeing a transition.
From trying, at all cost, to keep within certain CAT wingspan requirements, to optimum wingspan design.

Winglets on long range flights
 

Given that the winglets are best suited for longer flights, why are they being fitted to 737's? I never could figure that one out.

if you turn the wingtip up, you had an 'equivalent' wingspan,

ballpark, sails are worth around 3/4 their length in span extension

why are they being fitted to 737's

same as for any design, it comes down to doing the sums and figuring the compromise .. unless, of course, the Chairman's wife just happens to like the look of them

One other reason is that it also increases your maintenance costs, so if you don't need them, don't install them.

Why fit winglets to B737?
 

Check Airman. The B737-BBJ has a claimed range of 5980 nautical miles with up to 25 PAX or up to 5510 with 50 PAX. The RAAF use it as their primary VIP aircraft. Maybe that may help you figure it out.

JAL B747-400D
 

For anyone who does not know, the JAL B747-400D is used on domestic services with high density seating and standard passenger capacity of 568, although up to 660 can be carried in one class configuration. Extra windows on the upper deck and lack of winglets are give-aways.

The airline that i work for operates a fleet of several leased 757's without winglets. The owners of the aircraft have blocked the proposal to install winglets for the sole reason of the modification will roughly half the resale value of a high hour 757 due to the fact that the alteration in wing loading transfered to the fuselage will not allow the large freight door to be installed in the event of a cargo conversion. Its very common for high hour 757's to be snapped up by cargo operators. The airline or operator would see some financial benefit but the owner will be out of pocket long term.

The wing configuration is an average design for optimization. Each configuration or use, would have a different optimized wing design.
The 737 first went into service in 1968 (?!?!?) damn!
Computer modelling and design have changed a bit, and due to access and CAT, the wingspan is stuck. turn em up, turn em down, or both..the longer and thinner at the end, the less 'theoretical' drag, and better economy, theoretically.
Of course, it has nothing to do with the ever reducing size or lack of outboard flaps...negating the size of that big round dork hanging off the bottom of the wing structure!

Winglets save around 2-5% fuel, but cost $100,000's to install.

It's simple maths really - draw a graph of installation cost and operating costs against the operating life of the airframe. The point where the lines cross defines your break-even point, and give you an idea of whether winglets are worth having for your particular route structure.

U

For anyone who does not know, the JAL B747-400D was used on domestic services with high density seating and standard passenger capacity of 568, although up to 660 could be carried in one class configuration. Extra windows on the upper deck and lack of winglets were give-aways.

There you go Old Fella, just bringing your post up-to-date. All part of my pedantic git service ;)

Few pilots are capable enough to fly the aircraft to design limits, then seek that extra 5-10% performance.

It's beyond frustrating sitting in a plane all day long at lower altitudes, limited ranges, lower speeds, because the FAA is trying to buffer the performance envelope for a battalion of golf buddies, pals, idiots nephews, airline SOP robots, marshmellow first officers, unqualified owners, 200 hour ab initio wannabee pilots and so on.

I would like to see if there is any benefit to variable or folding/extendable winglets - either in the lateral or longitudinal planes.

Modern technology and materials must have made this possible.

Folded for ground operations & high speed cruise & climb.

Extended for increased aspect ration benefits in takeoff, cruise and landing.

Any thoughts?

I was involved with such investigations as an undergrad in the early 70s. The idea goes back a long way.