Despite the advances in other areas, Airbus lagged behind when it came to wingtip devices. The conventional and all too familiar wingtip fences that we see on the Airbus A300s, A310s, A320s and the A380s did their job, but a scope for improvement always existed. The Airbus A330s and the A340s broke from the norm by employing conventional winglets, similar to the ones seen on a Boeing 747-400.
On the 30th of November 2011, when the first ever A320 to be produced: MSN 0001 took to the skies, this wingtip complacency was relegated to a page in history. With the first flight of an A320 with “Sharklets”, the Airbus lingo for winglets, Airbus was ready to give to the world a much awaited confirmation and assurance of a winglet that will finally make its way to production aircraft.
Vortices which result at the tips of wings as a result of the pressure difference that exists between the upper and lower surfaces of the wings induce a drag which reduces the wing’s aerodynamic efficiency. Winglets are small , nearly vertical aerodynamic surfaces which are designed to be mounted at the tips of aircraft wings. A properly designed winglet impedes these vortices, shifting them instead further up to the tip of the winglet, resulting in much weaker vortices. As a result, the induced drag is significantly reduced, improving the lift to drag ratio of the new compound wing structure.
An increased lift to drag ratio implies lesser engine thrust requirement for a desired amount of lift, which directly relates to fuel savings. Like other winglets, these Sharklets bring with them a bundle of realistic promises, the biggest of which is a 3.5% fuel saving over 3000NM-long flying sectors, and around 1% fuel saving over 500NM long sectors, in comparison to A320s flying with the conventional wingtip fences.
For an A320 operator like Indigo, which deploys its A320s on a mix of medium haul international and short haul domestic routes, the savings can be huge. Based on the flight schedule, Indigo can comfortably deploy one A320 on the Bangalore-Mumbai-Singapore-Mumbai-Bangalore pattern every day. Fuel cost at Bangalore and Mumbai have been approximated to be the same.
Projected savings on a single A320. Fuel Prices as of Dec 25th, 2011. 3% fuel savings (assumed) used for 2000NM and 1% fuel savings (Airbus data) for 500NM.
With this pattern, the same A320 operating with Sharklets can save about US$400,000 per annum on fuel related costs.
According to John Leahy of Airbus, the price for the winglet will be similar to the forward fit, of around US$950,000, although the retrofit kit could add to the cost, though not substantially. A pair of Sharklets attached to an A320 flying the above pattern can pay back for itself in 2.5 years. Six A320s in Indigo’s fleet (INA-INF) are 5 years old. If Indigo plans to get rid of aircraft around 5 years old, a potential US$ 1M is saved by the airline, per aircraft.
But these are not the only savings. Either the revenue payload can be increased by 500kgs, or the range can be extended by 100NM at the original payload. The increased lift to drag ratio of the wing will result in higher available takeoff weights, notably from obstacle-limited runways, and where runway performance is not limiting, operators could profit from a reduction in average takeoff thrust (with consequent savings in engine maintenance costs by around 2%). The Sharklets lend the aircraft a better takeoff performance and rate-of-climb, higher optimum altitude, higher residual aircraft value, and greater safety margins in the event of an engine failure.