A fuel-saving angle for cargo
A GKN Aerospace employee assembles a winglet for a 767. Photo courtesy of GKN Aerospace.
Though usually touted for fuel savings, winglets give cargo carriers other opportunities – including opening new markets.
Winglets have been widely used by airlines since the 1990s and 2000s. They help blend the air that runs on the top and bottom of the wing tip. Under the wing, the pressure is high, and above it, the pressure is low. Without a winglet, the two different levels of pressure around the wing tip create a vortex – which makes extra drag on the plane. The plane must then work harder to get through the vortex. (The effects of winglets on a plane and off a plane are shown in the picture to the right. Image courtesy of Bombardier Inc.)
“What the winglet does, it kind of creates an obstacle at the wingtip, a kind of a fence, that will be an obstacle to the creation of that vortex,” says Jean-François Viau, section chief for the advanced design group of Bombardier Aerospace.
Typically, airlines’ largest single expense is fuel, so using less of it is the obvious benefit of winglets.
But winglets provide other benefits, especially for cargo carriers.
Viau says if a plane burns less fuel on its route, an airline can save money or can choose to put more cargo on the plane. An airline can also use the same payload and fly a longer distance with the fuel saved.
“That gives you all the flexibility,” Viau says. “Either it opens up new routes, more revenue because you have more cargo, or less fuel burn so it’s better profit.”
Airplane manufacturers tell Air Cargo World that planes made with winglets lead to an approximately 5 percent saving in fuel burn.
“I know some airlines that would probably sell their organs and close family members for 1 percent fuel burn reduction. Imagine 4 or 5 percent – it’s very important,” Viau says.
A winglet retrofitted onto a plane provides a 2-3 percent reduction in fuel burn, says Chris Gear, vice president global engineering and senior technical fellow for manufacturer GKN Aerospace.
Winglets also help takeoff by improving a plane’s initial climb capabilities.
“Maybe your aircraft can now operate from more demanding airports, so airports with shorter runways or airports located at high altitude or in hot temperatures,” Viau says. “It opens up new markets.”
With that extra takeoff capability, the airplane also requires less thrust, meaning less noise. This could make night operations easier.
“Maybe that allows you to operate from an airport you wouldn’t normally,” Viau says.
How to create winglets
In 2013, Boeing tasked UK-based GKN Aerospace with manufacturing the winglet for the 737 MAX.
Gear says this is a different type of winglet, with a part swooping up and down. GKN has an engineering team who has been at Boeing for a year helping to design the winglet. Manufacturing in the UK will start shortly, before going to the U.S. for final assembly.
GKN has also built winglets for the Boeing 737, the new C-series Bombardier aircraft and a retrofit kit for the 767-300.
GKN makes a winglet to meet 1.5 times its normal operating flight conditions. In addition to 3D modeling, the company has a testing facility where it attaches the winglet to a dummy wing and applies loads.
Quebec-based Bombardier, which was the first aircraft manufacturer to integrate winglets on aircraft, follows a similar process, Viau says. After computer modeling future winglets, Bombardier does designs of these simulations. The company selects a few different designs to build on a small scale and test in its wind tunnel.
Every Bombardier aircraft but the Q400 uses winglets.
“Designing winglets, even though it’s very technical with the tools and the wind tunnel, it’s still kind of an art,” Viau says. “Winglets, being at the tip of the wing, they’re in the region of the wing that’s a bit more complex. The phenomenon occurring in those locations is a bit more complicated than let’s say in the middle of the wing.”
Boeing and Airbus declined to comment for this story.
Fuel is a large expense for airlines, so anything that can cut down on that bill captures their attention.