Winglets have been understood since the beginnings of aviation. In fact an Englishman, Frederick W. Lanchester described them in 1897 before the Wright Brothers had even taken flight. Like many great pioneers of his time, Lanchester looked to birds for inspiration. He noted that soaring eagles had splayed upturned feathers at their wingtips and he incorporated this into his designs for model gliders.
It was some time back in the early '80s when aircraft wings started to sprout "winglets" –those things that look like fins attached to the end of the wing. But what are they, what do they do and how do they do it? Do they make the plane go faster, use less fuel or are they just another billboard for our marketing team to decorate?
Winglets give aircraft a performance improvement of anything between five and 7%. They do that by reducing the powerful vortexes that curl out behind the wingtip as the aircraft slices through the air. These occur when low-pressure air flowing over the wing and the high pressure flowing under the wing meet at the tip. The vortexes create drag, slowing the aircraft down and need to be countered with increased thrust and therefore more fuel burn. With the clever aeronautical design, and it is really complicated, winglets can change and drastically reduce the vortex, so the aircraft needs less thrust to maintain the same speed.
Apart from some small wing tip plates seen on military aircraft during the wars, the first time the winglet appeared was on an enthusiasts aircraft called the Rutan VariEze in 1975. This was designed by Virgin Galactic founder Burt Rutan. A legendary aircraft designer, Burt is known for designing extremely efficient and sometimes unusual looking aircraft.
The next stage in the winglet story came in the executive jet sector when they appeared on the Learjet 28 in 1977. Originally a test aircraft, the vertical winglets had first been conceived by NASA aerodynamics genius Richard T. Whitcomb at the Langley Research Centre. He went on to fit winglets to large tanker aircraft and realised impressive efficiency gains of up to 5%.
Winglets really hit the mainstream after aviation was hit hard by a huge hike in oil prices in the mid-70s. This precipitated the jump to commercial airliners. Airbus put tiny fences on an early version of their A310, but the real beginning of winglet mania came with the new variation of the mighty Boeing 747-400 series. The first 747-400 was delivered to Northwest Airlines in 1989, the first commercial aircraft with proper winglets.
Since then winglets have become the norm with nearly as many designs as there are types of aircraft. The ones found on our 747’s and A330’s are the original design created as a bolt on to an existing wing. Then there are those where the winglet extends above, and below the wing (called ‘The Fence’!) Later aircraft had what is called a blended winglet which has a smooth curved integration with the wing. Different winglet designs can boost different phases of flight. So long haul aircraft winglets are designed to give greatest efficiency gains in cruise, while short-haul would look to boost performance around the take-off and landing phases of flight.
Airbus has developed their own brand of winglet design they are calling ‘sharklets’. The best of these come with their new A350 XWB and when we first caught sight of them our inner avgeek went into overdrive. They look amazing. Swept up and back in a graceful scimitar curve, they are as beautiful as they are efficient. Aircraft are a good example of where great design comes from the engineers and scientists. One thing’s for sure; wing design will continue evolving, and we look forward to seeing where the engineers, aerodynamics specialists and designers will take it next.
Boeing is introduced the very latest in advanced winglet technology on the controversial 737 MAX, known as the AT Winglet. In addition to the inward, upward and slightly forward lift components of the upper aerofoil, the new lower aerofoil generates a vertical lift component that is vectored away from the fuselage, and also slightly forward. Working together, these provide the perfectly balanced winglet that maximizes the overall efficiency of the wing. Believing there was even more efficiency to be gained on top of the benefits from this ingenious solution, the 737 MAX team went on to incorporate Boeing's advanced natural laminar flow technology into the surface material specification for the MAX AT winglet.
Boeing’s 777x was designed with folding wing-tips that will increase wingspan and, as a result, fuel efficiency without limiting access at airports. Boeing claim the 777X will be both the largest and most efficient twin-engine jet in the world. The wings are based on those of the 787 Dreamliner and will stretch to 71 m when extended thus taking winglet design to even higher levels.