737-Max Winglet Concept Doesn’t Cause A Stir

The new Boeing 737 MAX Concept still being drawn up as the economical answer to the current world’s best selling aircraft has developed what can only be described as a brand-new old idea. The big story here is the main wing will now feature a ‘split’ winglet which should generate a 1.5% reduction in fuel efficiency. This now pushes the 737 MAX past the 12% of fuel burn improvements over its current model with the new engines and aerodynamic tweaks to the airframe.

In a conference call with journalists, Michael Teal, chief project engineer for the 737 MAX, called the concept “the most advanced wing-tip technology in the single-aisle market.” Whilst this has been touted as a huge development in wing-tip technology, it does have a striking resemblance to the wing-tips found on the MD-11s of yesteryear (shown below). Whilst the aerodynamic design looks a lot slicker, they fundamentally has a rudimentary father in the aviation industry.

The MAX, is competing against the Airbus A320neo. The ‘Neo’ is adding winglets — Airbus however, calls them “sharklets” — to the current A320 design, but they basically the same as the winglets seen on the modern 737 aircraft currently in service. Boeing still has some work to do though, as Airbus are still estimating 10% more fuel efficiency than the 737 MAX, even with these rather peculiar looking winglets.

What the bejesus is a winglet and why do they exist?
This was a question I asked myself before commencing a commercial pilot course, and only through the course really understood, with any great detail, the reason why they exist. I’ll explain as best I can whilst trying to keep it simple here…

The wings are aerodynamically similar to a birds wing. They create lift by passing the air faster over the top surface, creating an area of low pressure above the wings which, like a vacuum cleaner, sucks the wing and rest of the plane higher into the sky. The faster you go, the more lift you create. This is simply done by having that curve you see on the top of the wing. This said, the downside to all this lift is a thing called drag. To explain drag, it’s like sticking your hand out the window of a car and facing it palm forwards. You instantly feel the force pushing the hand back. To make it less resistant, we hold our hands parallel to the direction of the car. Suddenly, no force is felt against our hand – a ‘reduction’ in drag. The wings create the most drag by creating vortices (horizontal mini tornadoes) at the end of the wing, where the two airflows above and below the wing mix.

The idea of a winglet is to try and reduce the vortices by blending the air as smoothly as possible. By doing this, less energy is needed to produce the same amount of lift. Therefore, engines don’t need to work as hard to keep the plane in the sky. By doing this, fuel burn is saved and fundamentally the cost of the flight can be reduced. 1.5% might not sound a lot, but put that into comparison on the tonnage of fuel a plane has to carry, suddenly 1-2% of ‘a lot of fuel’ can be a huge saving. It’s fair to say for most carriers, roughly 1/3rd of the weight of a plane is in its fuel load.

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