Wingtip Devices - what are the different types and how do they function?

Wings are an essential part of an airplane, producing the necessary lift and that's a given. Have you ever noticed though, they are never flat and are either angled or upward sloping?

The tips of airplane wings are adorned with all types of winglets, sometimes featuring a distinct curve, like the Airbus A350 or Boeing 787. Passenger jets without winglets are becoming increasingly rare.

So, what are winglets and what function(s) do they perform? Winglets, or Wingtip devices, are touted to help with fuel efficiency by reducing the drag caused by airflow patterns over the wingtip and increasing range for more efficient travel.

A brief history

Although been around since the early days of aviation, researchers at NASA are officially credited for the research and development of these innovative design features.

Dr. Richard Whitcomb | Baltimore Sun

Dr. Richard Whitcomb, an aerospace engineer at NASA Langley Research Center, tested winglets — vertical airfoils on the tips of wings — compared to longer wings in a wind tunnel. Whitcomb showed that the winglets would improve cruising efficiency by 6-9%; tests by the NASA Dryden Flight Research Center using a military version of the Boeing 707 showed an increase in mileage of 6.5% for the same amount of fuel.

How do they work?

Winglets are basically "mini-wings". Hence it is imperative to have an understanding of how wings work to grasp how they function.

 The wing shape generates lift by exerting downward pressure on the air mass it is travelling through, causing a pressure difference below the wing compared to above; there is less pressure on the upper surface of the wing and more on the lower surface.  This pressure difference, the air below the wings rolls up and wraps around the top of the wing, causing a whirlwind named a wingtip vortex.

Phys.org

Now, wingtip vortices are notorious for increasing drag and reducing lift that results in less flight efficiency and higher fuel costs. Winglets produce “lift” as well, but because they are tilted upwards, that lift results in forwarding movement inside the vortex and reduce the strength of that vortex.

There is, however, a trade-off though. As is with everything, winglets also add to the overall weight and drag- around 500 pounds on average. But all said and done, the aerodynamic benefits outweigh the additional weight and drag. That’s why most jetliners made today come from the factory with winglets.

Some common types of winglets

1. Raked

The Points Guy

Raked wingtips feature a “raked” shape by curving backwards. Many aeroplanes, including the Boeing 787, feature raked wingtips. In the case of the 787, those raked wingtips also have a slight upward curve

2. Canted

Wikimedia Commons

Canted winglets are short, upward-sloping wedges; they can be found on Airbus A330 and A340 aircraft and on the Boeing 747-400.  It’s believed that the use of canted wingtips increased the range of the Boeing 747-400 by over 3%. These winglets are likely to disappear from view as the current models of the A330 go out of production and new wing shapes are developed

3. Blended

Victor Tango Aviation

They feature a much smoother transition from the wing itself to the winglet, which produces additional efficiencies compared to a canted winglet or wingtip fence. Mostly seen on many models of the Boeing 737.

4. Winglets on the Boeing 737 MAX

Eurocontrol

The Boeing 737 MAX has winglets that look similar to the split-scimitar ones, but they are slightly different and come as standard equipment with every MAX

5. Split-scimitar winglet

Houston Chronicle

Found on many Boeing 737 aircraft, they are either delivered with new airplanes, or retrofit by Aviation Partners Boeing; the former appears on Boeing 737-900ERs flown by Delta, and the latter on many United Airlines 737s. They are a cross between a blended winglet and the wingtip fence, essentially blended winglets with an added airfoil below the wing.

6. Wingtip fences-An Airbus innovation

The small winglets that are seen on many Airbus variants are called wingtip fences. This type of winglet was meant to address the wingtip vortices that originate from the bottom of the wing, and therefore have a physical barrier below and above the wing. Spotting them is an easy way to differentiate between a Boeing 737 and an Airbus A320 family aircraft.

Did you know? The newer Airbus A320-family aircraft also sport blended winglets that look very similar to the winglets on the Boeing 737 — except they’re called "sharklets". The name is simply a unique way of marketing.

The Flying Engineer

SOURCE(s)

COVER: FlightGlobal

The Air India Express cabin crew have decided to launch an indefinite strike from January 15 if the management does not address their concerns. Over 500 cabin crew under the Air India Express Employees Union (AIXEU) are likely to strike work. They allege that the management has shown discrimination while issuing contracts. 

"The contract period for cabin crew was reduced to one year from five years. At the same time, the contracts of other staff and new recruits are for five years. We met the management nine times in the presence of the central labour commissioner to resolve the issue but we didn’t get any positive response.The labour commission had ordered to offer a ground staff job to the cabin crew member who got injured. Instead, the management terminated his contract. This is an unfair labour practice."Vijaykumar KK, President, Air India Express Employees Union AIXEU (BMS)

The crew under the Air India Express Employees Union have sent a strike notice to the airline's CEO and will proceed with their plan if the management does not reply favourably. Air India Express cabin crew form over 70% of the union members. The strike, if it does happen, will affect flight operations.

"We have raised our concerns and have put forward our demands to the management. The strike notice was issued in December 2021. No reply has been received so far," said a cabin crew member.

Over 500 cabin crew under the Air India Express Employees Union (AIXEU) are likely to strike work.

He said that they had staged a national-level protest in front of the Air India Express headquarters in Kochi last month, raising their demands and citing the unfair labour practices followed by the management.

The AIXEU has raised two issues with the management. One, to reconsider the contract period of the cabin crew members. The second, to offer a job to a cabin crew member who got injured and is currently in a wheelchair.

The AIXEU represents about 500 cabin crew personnel, and any strike would significantly impact aircraft operations.

The employee protest at AI Express comes at a time when a change of ownership is just around the corner for the airline. While the carrier’s handover to the Tatas has been delayed slightly over some regulatory approvals, it is still very much on track.

The Tatas have been keeping a close eye on protesting employees of the Air India group and would want the airline to fix these issues before the official handover. Furthermore, with reports of a possible merger of AI Express with AirAsia India, the Tata Group would want to resolve any pending issues with employees for a relatively smooth transition.

Multiple headwinds for the Indian aviation sector from rising ATF prices and restriction on movement due to the Omicron variant of Covid-19 to bad weather in North India leading to numerous flight cancellations. Air traffic numbers of 5th January 2022 paints a very grim picture. Only 3.08 lac passengers took flight as compared to 4.09 lac (daily average) that boarded planes in December 2021. That is a clear 24.4% slump shot in the already limping aviation sector.

Passenger load factor(PLF) is an airline industry metric that measures how much of an airline’s passenger carrying capacity is used. PLF is one of the most critical metrics from a capacity management perspective. Airlines not only try to maximize their PLF but also take decisions about pricing, capacity and frequency of flights based on this key performance indicator. Below is the table you can find this data for major Indian carriers and compare them.

Airlines of India 5th January 2022 November 2021 Indigo66.4%80.5%Air India60.2%82.0%SpiceJet70.2%86.7%Vistara50.0%77.0%GoFirst60.0%78.2%AirAsia India57.0%74.6%

Moreover, if we follow the global trend, further decline is expected in the air traffic numbers. European major, Ryanair’s monthly traffic has already slipped to the lowest level since July 2021. Airline operators in the United States have been seeing 3000 flight cancellations on an average daily. This has been quite a messy end to the holiday season all over the world.

The Omicron wave in South Africa, the UK, Denmark has seen a sudden surge followed by a quick dip, based on which experts are estimating that India's peak will arrive in the next four weeks. We can only hope to get back on the growth and recovery cart once again soon. The aviation market is poised for the entry of new players, including Akasa and Jet Airways, with asset cost at an all-time low, talent in abundance, and incumbent airlines struggling with legacy issues.

The West Bengal government will now allow flights from New Delhi and Mumbai, the two cities witnessing a huge surge in Covid-19 cases, thrice a week instead of twice as was decided a couple of days ago, a senior official said on Tuesday.

From January 5, flights from the two metros will be allowed to come to the state on Mondays, Wednesdays and Fridays, he said.

A communication from state Home Secretary BP Gopalika was sent to Secretary of the Ministry of Civil Aviation Rajiv Bansal on Tuesday, January 4, the official told PTI.

The West Bengal government will now allow flights from New Delhi and Mumbai. (Image Courtesy - Mint)

"... this is to kindly inform that the matter was reviewed and that the state government is extremely sensitive towards the inconvenience that may be caused to the passengers but restrictions are absolutely essential for containment of COVID cases in the state," Gopalika wrote to Bansal.

"However, the incoming domestic flights from Mumbai and Delhi will be allowed thrice a week on Monday, Wednesday and Friday with effect from January 5, 2022, and the same will be reviewed again shortly depending upon the COVID situation in the state," the letter read.

On Sunday, January 2 Chief Secretary HK Dwivedi had announced that as a part of the restrictions imposed in the state, flights from the two metros would be allowed only on Mondays and Fridays.

This is affecting Air India’s once-weekly London-Kolkata flight.

The state has also banned direct flights from the UK in the wake of the surge of the Omicron variant of Covid-19 in that country. This is affecting Air India’s once-weekly London-Kolkata flight.

During the second wave in April-May, West Bengal had imposed similar restrictions on flights from some states. Every day, 25 flights from Delhi and 15 from Mumbai arrive in Kolkata.

The Delhi High Court on January 4 reserved its order on BJP MP Subramanian Swamy’s plea challenging the procedure through which Air India selloff took place.

Fixing the date for orders on January 6, a bench headed by Chief Justice DN Patel gave the government as well as the Tata Group time till the end of the day to file their brief notes explaining their case.

Swamy has been afforded a day to respond to the government’s case. The order will be pronounced on January 6, the court said.

BJP MP Subramanian Swamy

Swamy has sought a detailed investigation into the disinvestment process which, he claimed, was rigged in favour of Tatas. He said the “gigantic corruption” calls for a CBI inquiry into the role played by officials in the entire disinvestment process and urged that the report be submitted exclusively to the court.

Arguing the case himself, the MP said that he was not opposed to the general policy of disinvestment and was in fact in favour of it. The specific case of Air India sale, however, reeks of corruption, he argued. “There is no accountability in the process and therefore requires a full-fledged investigation.”

Swamy also urged the court to quash the entire process through which the airline was bought out by the Tata Group. Swamy has prayed before the court to revoke any future approvals that may be granted for the Air India sale.

In October 2021, the Centre accepted the highest bid made by a Tata Sons company for 100% equity shares of Air India and Air India Express, along with the government’s 50% stake in ground-handling company AISATS — the first privatisation in the country in 20 years.

In October 2021, the Centre accepted the highest bid made by a Tata Sons company for 100% equity shares of Air India and Air India Express.

Raising the question of “impropriety, illegality, and corruption” in this case, Swamy said that the sale was painted as a “great return”. The only second bidder, according to him, was SpiceJet which remained disqualified on account of insolvency proceedings initiated against it before the Madras High Court, he said.

Solicitor General Tushar Mehta said that Swamy’s plea was based on certain misconceptions and sought to outline that SpiceJet was never a part of the consortium to bid for Air India. Moreover, the decision to privatise Air India was a policy decision taken in 2017 and is not a decision taken recently. The government has been bearing the brunt of the losses the airline has been running into which made the need for selling it off more prominent.

Swamy, during his arguments, also invoked the link between Tata Group and Air Asia. But, Senior Advocate Harish Salve, representing the conglomerate, clarified that the company buying out Air India was a wholly-owned subsidiary of Tata Sons and was a “100% Indian company”.

As of August 31, 2021, Air India had a total debt of INR 61,562 crore.

After hearing the case somewhat at length, the court has given a short date now for the orders on the plea to be pronounced later this week.

The government signed the share purchase agreement with Tata Sons on October 25, 2021, for the sale of Air India for INR 18,000 crore. The Tatas would pay INR 2,700 crore in cash and take over INR 13,500 crore of the airline’s debt.

The Tatas beat the INR 15,100 crore offer from a consortium led by SpiceJet promoter Ajay Singh and the reserve price of INR 12,906 crore set by the government for the sale of its 100% stake in the loss-making carrier.

As of August 31, 2021, Air India had a total debt of INR 61,562 crore, of which 75% or INR 46,262 crore will be transferred to a special purpose vehicle, Air India Assets Holding Limited (AIAHL), before handing over the airline to the Tata group.

As of January 6, 2022, India's largest passenger-load airline IndiGo owned by InterGlobe Aviation, has a fleet of 290 aircraft out of which only 4 are parked and the rest are in active service. The fleet consists of 35(ATR 72), 63(Airbus A320ceo) & 140(A320neo) and 52(A321neo). IndiGo has the largest share of Airbus aircraft in the Indian aviation market.

Airbus A320 CEO

In an official statement by the airline's CEO Ronojoy Dutta, he said the company will work towards consolidation and won't be expanding its fleet for the next two years. As per the latest release by Airbus, Indigo's outstanding order tally stands at 203(A320neos) and 331(A321neos). Future deliveries of A321neos will be a combination of its base option, long-range and extra long-range versions. In the case of its regional airliner ATR-72, 12 more will be joining the fleet to fuel UDAN aspirations.

88 older Airbus A320ceos were deregistered by IndiGo during the pandemic and replaced with an almost similar number of more fuel-efficient A320neos and A321neos. This move has helped keep the fleet young, under 4 years on average. The process of A320ceo replacement is expected to be completed only by the end of 2023 mainly because of their sheer number.

Airbus A321-200 P2F

The low-cost carrier had placed an order for 4 Airbus A321-200 P2Fs in April 2021. As per sources, the first of which is ready to be delivered in all-cargo configuration. Upon taking delivery, the Gurugram headquartered airline will become the third major player in the Indian aviation freighter market after Blue Dart Aviation and SpiceXpress.

Sticking with a single type of aircraft has helped Indigo not only grow but also become the undisputed leader of the Indian sky. A common fleet with a single class seat configuration has aided in high employee productivity and lower cost in terms of training and maintenance. Also, the cost of aircraft acquisition became considerably lower through the bulk purchase strategy. In October 2019, it placed an order for 300 A320 Airbus aircraft, making it one of the largest aircraft orders with a single airline operator.

While with the induction of A321XLR, Indigo will be able to reach(non-stop) most of the major destinations of Europe, Africa and Asia. But to truly tap into the international market, the company at some stage will have to think of a widebody order. Market experts feel that a huge order of either A330 or A350 from Indigo is imminent in near future. Traditionally Indian airlines have favoured Boeing whenever they had long-range and passenger comfort in mind.

Airbus A330-800 NEO

Indigo fans and aviation enthusiasts may have to wait longer considering new variants of Covid-19 has started to erode much of the growth and recovery accomplished in the past few months. Only time will tell how future fleet expansion shapes up in this ever-changing dynamic business environment.