5 Effective Strategies for Saving Fuel on Aircrafts

Strategy for saving fuel number 1: Winglets

Everyone who has made an airplane with paper knows that bending the sides of the wings makes your plane, not only much cooler but fly farther. Nowadays, airplanes tend to use this technology more regularly. So, the next time you see an airplane, look at the wing, as there is a great possibility that its end is bent up. You can also find that it is tilted gently smoothly like eagles do while they are flying. Although obviously these modifications are much more complicated, they perform the same aerodynamic role as the ends of the folded wings of a plane made of paper. Then, it is not only an aesthetic issue, but it is one of the most visible and used technologies of fuel saving and performance improvement in the aviation industry.

This technology is based on two forces: lift and drag. Lifting is the one that makes it possible for airplanes to fly. It is created by unequal pressure in a wing thanks to the air that flows around it. This way the aircraft has positive pressure under the wing and negative above it. Drag, however, provides resistance against the movement of the airplane. The main source of drag is the result of the huge pressure that we can find above the wing, which, in consequence, makes the air to flow upward on the tip of the wing and convert into a vortex. These also called induced drag, have the enough power to resist aircrafts that fly very close to each other, and this is one of the reasons for the carefully monitored separation between flights at takeoff and in the air. The induced resistance reduces the efficacy of the airplane, reducing the mileage, range and speed of the fuel. A typical Southwest Boeing 737-700 aircraft saves approximately 100,000 gallons of fuel each year. The technology in general offers between 4 and 6 percent of fuel savings. A Boeing 747-400 consumes 3,411 gal./hour. At $ 3 per gallon = $ 10,233 per hour. Then this plane can save up to 613.98 $ per hour. It cost about 1,060,000$ to install them in a 737-700 aircraft. However, in the new aircraft model they are already included. Although it is difficult to estimate how many hours a year these planes fly, because it depends on their schedule and type of aircraft, the average number of 2,500 hours/years would be used for the calculations. Then, the total earnings per year are 1,534,950 $ per year. Finally, it is possible to estimate the payback as the realized investment divided by the savings, this shows a total time of 8 months and 9 days.

Conclusion

This aerodynamic improvement has really good benefits and has a great payback, that's why most of the airplanes are using winglets. What is more, here I have calculated only fuel savings, but it also has impact in time and the aircraft speed. To sum up, it seems a really good way to save fuel.

Strategy for saving fuel number 2: Satellite Navigation

Global navigation satellite systems (GNSS) provide a great benefit to aviation by allowing aircraft to fly directly from departure to their destination using the routes with higher fuel efficiency and allowing them to navigate in difficult terrain at low altitude. Satellite navigation gives the alternative to design new procedures that allow aircrafts to fly closer between them to increase arrival and departure rates and perform continuous climb and descent operations to minimize fuel, noise and carbon emissions.

Using the language of the aviation community, GNSS allows performance-based navigation, which consists of area navigation (RNAV) and required navigation performance (RNP) (Aviation Benefits from Satellite Navigation, Stanford University). Both RNAV and RNP can perform point-to-point flight paths without restrictions. RNP is different from RNAV, since it also has a monitoring and warning function that allows the pilot to be warned when a correction is required, in addition, this allows the aircraft to use tighter flight routes. GNSS is the only navigation source approved for RNP operations.

Global navigation satellite systems (GNSS) is used by a huge range of users in the air, on land, at sea, and in space. These generalized customers enjoy a location precision of 5 m worldwide, 24 h / day, in any climate. If the user needs greater precision, differential techniques are available to provide decimeter accuracy or even centimeter accuracy. Nowadays, Alaska Airlines uses GPS to help navigation in 30 airports in Alaska and the continental United States. They own a fleet of 117 Boeing 737 equipped with this technology, and its sister airline Horizon Air operates Bombardier Q400 turboprops with similar capacity. According to Alaska Air, the airline performed 12,700 approach and departure procedures in 2011, avoiding the diversion of 1,545 flights through the use of GPS navigation. In that year, the airline used GPS to help reduce fuel use by 210,000 gallons. ( Aviation Benefits from Satellite Navigation, Stanford University). Using the same data as in the previous point, with a price of 3 $ per gallon, they can save a total amount of 610,000 $ per year, and its cost is not comparable with that amount.

Conclusion

To sum up, this technology has multiple benefits to aircrafts, again I have just focused on fuel savings, however, it also has an impact in time consuming and other factors related to the industry. In addition, the calculations have been made based on the company Alaska Airlines, so this data may not be applicable to other companies, but it can give us an idea of the possible savings. Finally, it is possible to say that it is a good alternative to save fuel.

Strategy for saving fuel number 3: Single-Taxi Engine

When airplanes circulate on the surface of an airport, they consume a large amount of fuel. This is because the jet engines are designed to have an efficient operation of energy at high speeds and high altitudes, but when working on land they are less efficient. A single engine can produce enough thrust to move an airplane on land. Then, airlines can reduce fuel consumption at airports by operating with all engines off except one. If the aircraft is rolling for takeoff, the other engines will start several minutes early to allow the warm-up. If the plane landed and is rolling towards the boarding gate, all engines, except one, go off as soon as the plane leaves the runway.To understand this, some consideration must be made:

• Weight of the ramp: the greater the weight, the more power is needed to roll the plane.
• Ramp gradient: steep taxiways require more power.
• Heating and cooling period of the motor: a minimum interval of 2 minutes must be applied.
• The taxi time to the active runway must be estimated to start the second engine on time.
• Slippery or contaminated taxiways: in this scenario, you should avoid rolling with a single motor.

Increased workload of the pilot: it is not recommended to start the second engine during taxiing. ( Fuel Conservation Strategies Through Flight Operation Optimization at PGA, Técnico Lisboa) However, the periods of heating and cooling of the motor must be fulfilled to allow thermal stabilization of the motor. In addition, the second engine must be kept running for at least 2 minutes at idle before selecting high thrust or shutdown settings. What is more, when rolling, the second engine starts with the airplane static to avoid the pilot heads down condition (start-up checklist) during taxiing. Average fuel reduction per flight: up to 45 gallons, this means 135 $ per flight. We can assume that a 737 has an average of four flights per day, this means a save of 540 $ per day. In addition, 300 flight days are scheduled, then the total amount of money goes up to 162,000$ per year and plane.

Conclusion

In this case, no technology is involved, we can say his savings are based on fuel efficiency use of the aircraft. Actually, most of the American Airlines use this strategy, in fact, it is an easy way of saving money and fuel, without costs or technologies.

Strategy for saving fuel number 4: Idle Descent

One of the possible solutions to reduce fuel consumption is to do continuous descent (CDA) approaches. Eurocontrol defines this as an air operation in which an "airplane descends from an optimal position with a minimum thrust and avoids level flight segments". In a traditional approach, not CDA, the airplane descends step by step, with intermediate flight portions. When performing with CDA, the aircraft stays in higher altitudes for longer and operates with a much lower thrust of the engine. Both elements lead to a reduction in fuel use, emissions and noise during the descent profile before the point at which the aircraft is established on the final approach path. The CDA begins at the top of the descent and finalize when the aircraft begins the final approach and follows the glide slope to the runway.

Generally, this type of descent cannot be used for all types of flights and time, nor during all descents. But increasingly in more airports, the necessary measures are being taken to be able to use CDA flights.The descent phase usually consumes a lower fuel than the cruise or cruise phases, with a percentage of the travel time that should be around 10% for short and medium range flights, and the fuel is much smaller.From the point of view of fuel, the descent must be done as quickly as possible, using high speeds. On the other hand, this can discomfort the passengers, due to the pressure change generated in the cabin, and also for really high speeds. Then, it can cause the trip fuel to increase due to the cruise period and the high fuel flows during the descent. (Fuel Conservation Strategies Through Flight Operation Optimization at PGA, Técnico Lisboa) All this to a reduction of 147 kg per flight which means 38.22 gallons per flight. Then, we can have a savings of 114.66 $ per flight and 458.64 $ per day. At the end the total cost of the fuel that is saved by an aircraft in a year is 137,592 $.

Conclusion

With this strategy we can save up to 137,592 $ by year and plane. It is really close to the point 3 saving amount. What is more, we have no additional costs in doing this, so we can conclude the same as before, it is a good way of saving money and fuel.

Strategy for saving fuel number 5: Ground Power Use

Commercial aircraft are usually equipped with a small jet engine situated on the tail that acts as a generator. When the main engines are turned off, the Auxiliary Power Unit (APU) uses them to provide electrical power while the aircraft is standing at the door. The APU is also used to power all the systems that are used, in turn, to start the main engine. The APU uses the same fuel as airplanes, so prolonged use of the gate results in higher fuel consumption. An alternative to avoid the prolonged use of this technology is to use an external ground power (provided through the cable that is connected to the aircraft). This ground power is generated with much more efficacy and can power all the systems on board until it is time to start the engines, at which point the APU starts briefly.

Until recent days, the equipment supplied by the general manufacturers did not allow the APU to be completely replaced by external ground power, which obliged the pilot to start the APU to guarantee the comfort of the passengers while the aircraft was at the door. The APU does not require the ground support equipment to be turned off, the ground equipment operates without powering the aircraft, while the APU provides the necessary electrical and climate supply for the aircraft.As for the fuel, the average reduction per flight is about 11 gallons, which is 33$. Then in a day it is possible to save up to 132$, and in a year 39,600 $ per year and aircraft.

Conclusion

Ground power is a good alternative, maybe, compared to the other alternatives, it seems that the total savings of this are not worthy, however, these strategies and technologies are complementary and can be used at the same time. To sum up, ground power can help companies to save some fuel, however, not all the companies and aircrafts are prepared from its use.

Overall Conclusion

In this paper, five technologies have been analyzed, all of them have a great potential. As people can expect the most expensive one gives better results, in fact, winglets can save up to 1,534,950 $ in a year and by aircraft. On the other hand, we have the ground power which only helps us with 39,600 $. In order to have a general overview, if an aircraft uses all these strategies and technologies would be able to save an overall amount of 2,484,142 $. If an airline has, for example, 319 aircraft as American Airlines has, this amount goes to 792,441,298$. In addition, there are more technologies or strategies that are not named such as carbon fiber, 3D printing, electric assisted taxi, engine washing, cruise altitude optimization, cruise speed optimization, Double-Bubble D8, blended wing body, the use of alternative fuels and much more. Then, it is possible to say that aircrafts have invested a lot of money in reducing its fuel consumption since the fuel cost has increased. In fact, many other technologies are being investigated, and other solutions are being used, some of them are as ingenious as changing the material of the magazine that people can find in the aircrafts.