I was just wondering in anticipation of the PMDG 777 why it doesnt have winglets. I was under the impression they increase efficiency and reduce drag.

In fact the 747-8 and the 787 dont have any either just more of a curve at the end. Yet the NGX . 767, 747-4, MD-11 and a number of Airbus have them Is this now a customer option?

 

 

The answers in google search seem to be more of a guess and opinions. Perhaps someone on here would give a more definitive answer.

It was found that the raked wingtip offers better efficiency through less drag, when compared to winglets:

http://en.wikipedia.org/wiki/Wingtip_device#Raked_wingtip

The 77L/F/W have a different type of winglet. Called "Raked Wingtips". I prefer them in my eyes, I believe they do a better job. I noticed the B738WL always seems to float for me prior to touchdown. To be honest, I've not looked into the technical aspects of the 737's winglets but all of my wake turbulence encounters at KSNA (Real World) have been from B737/8's with Winglets, so I can't tell that they've reduced Drag/Vortex's. Somebody might be able to clear up!

I'm sure there would be issues if the 777 had winglets. Just imagine how many things those massive winglets could possibly hit....

 

The raked wing tips are awesome. Flying on an AC 777 LR and seeing first hand how beautiful it makes those wings look!

 

Cheers,

 

Tino

The 77L/F/W have a different type of winglet. Called "Raked Wingtips". I prefer them in my eyes, I believe they do a better job. I noticed the B738WL always seems to float for me prior to touchdown. To be honest, I've not looked into the technical aspects of the 737's winglets but all of my wake turbulence encounters at KSNA (Real World) have been from B737/8's with Winglets, so I can't tell that they've reduced Drag/Vortex's. Somebody might be able to clear up!

 

Reduced is not the same as eliminated. The pressure on top of the wing is smaller than that below it, and it's going to equalise somehow.

 

As for why the 777, 787 and 747-8 have raked wingtips, whereas the other planes mentioned in the OP's post don't:

First of all the planes mentioned are from different design generations. As technology has marched on we have become ever better at designing winglets, so the shape that is known to provide the best results has changed over time.

Furthermore a short-haul plane like the 737 will, relatively speaking, spend a greater portion of a typical flight in climb, compared to a long-haul plane like the 777, which will spend much longer in cruise. Thus on the 737 the winglet will have to also work well during climb, whereas on a 777 it can be almost completely optimised for cruise. Typically winglets work by reducing the induced drag, which is low during cruise anyway.

Another point regarding the winglet discussion is often overlooked, but it is quite important for the airline - wingspan.

 

You know how A380 had to fit into 80m wingspan so it does not have the best wing it could have, and unlike A330/340(and soon A32F) only has wingtip fences ISO winglets?

 

Well, there are "boxes" of different sizes. These are standarts airports are designed around. As it is, one of these boxes is the size of 36m.

And 737NG with winglets happens to have 35.79m wingspan. Juuuust right.

 

There is an NG variant with raked wingtips though - P-8 Poseidon. Its wingspan of 37.64m is not a problem for the Navy, however, for airlines, it would mean that all the gates, that 737NG is made to fit, would be unusable, and they would have to use widebody gates. With the 737 being one of the most common types of the planet, it would either mean massive redesign of many airports, or quite a number of airlines fleeing to A320, which would be cheaper to operate, as it fits into 36m "box".

 

(meanwhile, widebodies are less sensitive to wingspan issues, and most of their wings were designed with raked wingtips from the outset)