Winglets, near-vertical wingtip extensions, are seen on an increasing amount of commercial airliners today. For aircraft spotters a feature giving an aircraft a smooth look, for airlines an opportunity to increase operating efficiency. But what exactly are the driving forces behind the decision to install such devices on specific aircraft? Before we can answer this question we have to address the benefits of winglets.
The purpose of winglets is to reduce induced drag and increase overal operating efficiency by smoothening the airflow at the tip of the wing (where the upper and lower airflows meet and cause so-called vortices). As a result the aircraft encounters less resistance during flight and thus operates more fuel efficient. Infact, depending on the airplane type, its payload, route flown and other operational variables, winglets enable airlines to lower operating costs by reducing fuel burn by approximately 3.5 to 4 per cent on missions greater than 1,000 nautical miles. In addition, it improves payload capability by up to 6,000 pounds (737NG) while boosting take-off and obstacle clearance capability significantly. Furthermore, winglets not only reduce fuel burn, they also reduce aircraft noise by .5 to .7 EPNdB, or Effective Perceived Noise Level in Decibels, on take-off.
Advantages of winglets
- Lower operating costs by reducing block fuel burn by 3.5 to 4.0 percent on missions greater than 1,000 nautical miles
- Reduce engine maintenance costs
- Increase range up to 130 nautical miles
- Improve payload capability by up to 6,000 pounds (.5 to 3 metric tons)
- Improve take-off performance and obstacle clearance
- Increase optimum cruise altitude capability
- Reduce community noise by .5 to .7 EPNdB on take-off
- Lower emissions through lower cruise thrust (less drag)
The Blended Winglets, seen installed on Boeing 737, 757 and 767 aircraft, add approximately 5 feet to the aircrafts total wingspan. They are either available as a standard feature on newly acquired aircraft or through a retrofit carried out by Aviation Partners Boeing.
So if these winglets bring such benefits to the operation of aircraft, why aren’t they installed on every aircraft? At this moment approximately 85 to 90% of newly acquired Boeing 737’s is fitted with these blended winglets, with Airbus installing them as a standard feature on their entire A320, A330, A340 and even A380 aircraft. Second, many operators decide to fit their aircraft with them through a retrofit operation. Prices for a set of winglets (in this case those from Boeing) lie somewhere around $725,000 per aircraft.