There is a small difference in rotation rate for aircraft with winglets installed and, as a result, the crew needs to be cautious of pitch rate. There is approximately a ½ unit take-off trim change between non-winglet and winglet aircraft so the green band is slightly different for winglet aircraft. Finally, the dry “maximum demonstrated” crosswind limit is slightly reduced with winglets to 34kts. According to APB this is because “the FAA will only let us document the max winds experienced during flight test... so if we had been able to find more crosswind, then the 33kts might have been more. There appears to be no weather cocking effect due to winglets.”

If winglets are so good, you may wonder why all 737s don’t have them. In fact 85% of all new 737s are now built with winglets, particularly the 800 and 900 series and of course all BBJs. It comes down to cost versus benefits. Winglets cost about $725,000USD and take about 1 week to install which costs an extra $25-80,000USD. Once fitted, they add 170-235kg (375-518lbs) to the weight of the aircraft, depending upon whether they were installed at production or a retrofit. The fuel cost of carrying this extra weight will take some flying time each sector to recover, although this is offset by the need to carry less fuel because of the increased range. In simple terms, if your average sector length is short (less than one hour) you wont get much the benefit from winglets - unless you need any of the other benefits such as reduced noise or you regularly operate from obstacle limited runways.

Winglets are also available for Classics. The first winglet equipped 737-300 flew in Nov 2002 and gained its FAA supplemental type certificate (STC) on 30 May 2003. Winglet equipped Classics are known as Special Performance (SP).

Boeing has now developed, built* and are installing their own winglets for the 737 MAX family. The "Advanced Technology" winglet combines rake tip technology with a dual feather winglet concept into one advanced treatment for the wings of the 737 MAX.". They are split-tipped, straight-edged winglets for the 737 MAX. (see photo below)

There are two types of winglet available, Boeing's own built into the wing at the time of manufacture and the APB winglet as a retrofit.

Description Winglets are wing tip extensions which provide several benefits to airplane operators. The winglet option increases the Next-Generation 737's lead as the newest and most technologically advanced airplane in its class. These new technology winglets are now available on 737-800s as well as on the Boeing Business Jet (737-700 and 737-800).

Blended Winglets bring a modern look and feel to aircraft, and improve customers' perceptions of the reliability and modernity of the Airline.

By increasing Payload Range and Overall Performance, Blended Winglets add flexibility to fleet operations and route selection. Air Berlin notes, "Previously, we'd step-climb from 35,000 to 41,000 feet. With Blended Winglets, we can now climb direct to 41,000 feet where traffic congestion is much less and we can take advantage of direct routings and shortcuts which we could not otherwise consider."

With winglets, you can be a good neighbour in the community you serve. They enhance performance at noise-restricted airports and cut the affected area by 6.5 percent, saving you money on airport noise quotas or fines. By reducing fuel consumption, winglets help lower NOx emissions by 5%.

The addition of Aviation Partners Blended Winglets to the 737 Next Generation has demonstrated drag reduction in the 5 to 7% range that measurably increases range and fuel efficiency . In addition, the Blended Winglets allow the 737-NG to take off from higher, hotter airports with increased payload.

Winglets lower drag and improve aerodynamic efficiency, thus reducing fuel burn. Depending on the missions you fly, blended winglets can improve cruise fuel mileage up to 6 percent, especially important during a time of rising fuel prices.

The new split scimitar winglets with which United Airlines is retrofitting its Boeing 737-800 and 737-900ER fleets look similar to the winglets which feature on the new Boeing 737 MAX family. United estinates each set of split scimitar winglets will reduce by 2 per cent the fuel burn of any Boeing 737NG on which they are installed Once the split scimitar winglets are installed, United expects the winglet technologies installed on its 737NG, 757, and 767-300ER fleets to save it more than $200 million per year in jet fuel costs. United will begin retrofitting its 737-800 and 737-900ER fleets with the new winglets beginning early next year, once testing and FAA certification of the winglets are complete.

United Airlines’ program to retrofit its Boeing 737-800s and 737-900ERs with split scimitar winglets consists of replacing each existing blended winglet aluminum winglet tip cap with a new aerodynamically shaped “Scimitar” winglet tip cap and adding a new Scimitar-tipped ventral strake Using a newly patented design, the program consists of retrofitting United’s Boeing 737NG blended winglets by replacing the aluminum winglet tip cap with a new aerodynamically shaped “Scimitar” winglet tip cap and adding a new Scimitar-tipped ventral strake. “We are always looking for opportunities to reduce fuel expense by improving the efficiency of our fleet. The Next-Generation 737 Split Scimitar Winglet will provide a natural hedge against rising fuel prices while simultaneously reducing carbon emissions,” says Ron Baur, vice president of fleet for United Airlines. According to United, the new winglet design demonstrates significant aircraft drag reduction over the basic blended winglet configuration United uses on its current fleet. United expects the new split scimitar winglet to result in approximately a 2 per cent fuel saving for any 737NG fitted with it.

The first United Airlines Boeing 737-800 fitted with new split scimitar winglets from Aviation Partners Boeing takes off on its maiden test flight on July 16, 2013. The aircraft flew from Pained Field in Everett, Washington According to United Airlines, the new winglet design improves on the existing blended winglets currently fitted to the carrier’s Boeing 737NG fleet. In January, United served as the launch customer for the new split scimitar winglet when it made a firm commitment with Aviation Partners Boeing to retrofit its Boeing 737-800 fleet. In June, United announced it would also retrofit its Boeing 737-900ER fleet.

A United Airlines Boeing 737-800 retrofitted with new split scimitar winglets has performed its maiden test flight. The Boeing 737-800 with the new split scimitar winglet design ‒ similar to that to be used on the Boeing 737 MAX family ‒ made its first test flight on July 16, from Paine Field in Everett, Washington.

The modifiocation requires a trailing edge wedge, strengthened stringers and ballast weight but no changes to any avionics or the FMC. The base price cost for an upgrade from brlended winglets to SSWs was $555,000 as of 2014.

A set of SSWs weigh 133kg (294Lb) per aircraft but give fuel savings of 1.6% on sectors of 1000nm rising to 2.2% on sectors of 3000nm. This equates to an extra 65nm range.

Split Scimitar Winglets are offered by APB for the 737-800 and 737-900ER and came into service in early 2014. They are available as a retrofit to existing winglet aircraft .

*Two suppliers are manufacturing winglets for the 737 MAX programme, GKN and Korean Air Aerospace Division in South Korea. Production of the GKN winglets is at the GKN site at Cowes on the Isle of Wight in the United Kingdom with final assembly at GKN's facility in Orangeburg, South Carolina.

This graphic from Boeing shows from top to bottom, a non-winglet aircraft, a current blended winglet and an AT winglet. The AT winglet has a more even lift profile across its span.

Boeing claim they will give 1.5% fuel burn improvement over current technology winglets. They explain this as follows:"The AT winglet further redistributes the spanwise loading, increasing the effective span of the wing. The AT winglet balances the effective span increase uniquely between the upper and lower parts and therefore generates more lift and reduces drag. This makes the system more efficient without adding more weight."

The AT Winglets measure 8 feet from root to top of winglet and a total of 9 feet 7 inches from bottom of lower tip to top of higher tip. The top portion is 8 feet 3 inches and the bottom portion is 4 feet 5.8 inches. The ground clearance of the bottom tip is 10 feet 2 inches.

Boeing has now developed, built* and are installing their own winglets for the 737 MAX family. The "Advanced Technology" winglet combines rake tip technology with a dual feather winglet concept into one advanced treatment for the wings of the 737 MAX.". Using what they call "Natural Laminar Flow Technology"

This is a 737-200Adv, L/N 628, fitted with mini-winglets. This is part of the Quiet Wing Corp flap modification kit which gained its FAA certification in 2005. The package includes drooping the TE flaps by 4 degrees and the ailerons by 1 degree to increase to camber of the wing. Benefits include:

Operational Considerations There is a small difference in rotation rate for airplanes with winglets installed and, as a result, the crew needs to be cautious of pitch rate. There is also approximately a ½ unit take-off trim change between non-winglet and winglet aircraft so the green band is slightly different for winglet aircraft.

Availability 737-700, 737-800, 737-900, 737-BBJ - available now. Deliveries began May 2001. Initial customers included: South African Airways, Air Berlin, American Trans Air, Polynesian Airlines, and Hainan Airlines - both through direct purchase and leasing options via ILF, GATX, GE Capital Corp., and Flightlease.

Certification Retrofit FAA Supplemental Type Certificate (STC) was granted to APB on 3/23/2001. LBA (German regulatory agency) STC was granted to APB on 5/4/2001. JAA STC was granted May 2001. Boeing PLOD (program letter of definition) was granted 5/9/2001 by both the FAA and JAA for Boeing production.

Offerability Production and retrofit winglets for the Next-Generation 737s are available through Boeing (production) and Aviation Partners Boeing (retrofit). Aviation Partners Boeing (APB) is a joint venture partnership between Boeing and Aviation Partners Inc. (API).

Airplane provisions Structural modifications to accommodate the winglet include strengthening the wing's centre section and other internal strengthening on the wing. These enhancements are done in the normal production process. Various systems changes have also been made to accommodate winglet installation.

Weight Each winglet weighs about 132 pounds. Increased weight to the airplane for modifying wing and installing winglets is about 480 pounds.

Added wingspan Winglets add approximately 5 feet to the airplane's total wingspan - from 112 feet 7 inches to 117 feet 2 inches. (All Next-Generation 737 models have the same wingspan.)

Dimensions Each winglet is 8 feet long and 4 feet in width at the base, narrowing to approximately two feet at the tip.