CASE STUDY: A new solution for fuel efficiency at Viva Aerobus
Author: Paola Cavazos, Operations Engineering Manager – VIVA AEROBUS and François Chazelle, Head of Sales Support, Flight Efficiency, SITA FOR AIRCRAFTSubscribe
Paola Cavazos, Operations Engineering Manager at VIVA AEROBUS and François Chazelle, Head of Sales Support, Safety Line at SITA FOR AIRCRAFT describe how predictive analytics to have been used to drive flight efficiencies, fuel savings, and sustainability.
In this case study, we want to take readers through how the experience at Viva Aerobus has been using the OptiClimb® solution, a solution for fuel efficiency in the climb-out phase. But first, and to set the scene, we’ll share with you some information about Viva Aerobus.
Viva Aerobus is known for being the most affordable, low-cost airline in Mexico (figure 1) with the youngest fleet in Latin America: also, Viva Aerobus is one of the fastest growing airlines in the world.
The airline, founded in November 2006 so with seventeen years of operations, has a fleet of 64 aircraft with an average age of five years; recognized as the second youngest fleet in North America by ch-aviation. Most operations are in Mexico where the airline has a 27.7 percent market share but there are some international flights, to the USA as well as to Cuba and Colombia; Viva Aerobus has an 18.4 percent share of international flights from Mexico. There are over 3,000 employees across five operating bases and they are all really proud of what Viva Aerobus has achieved since launch.
Looking at the fleet, all the aircraft are from the Airbus A320/A321 family and are all with high density configuration, for a low-cost carrier, with a growing number of the aircraft being NEO versions. The goal is to have a fleet of 80 aircraft by 2026 which will enable Viva Aerobus to transport 100 million passengers by the end of 2030.
HOW OPTICLIMB WORKS – THE SCIENCE BEHIND THE SOLUTION
It was fortunate for SITA for Aircraft to have been able to engage with Viva Aerobus during the period of the COVID pandemic. Mexico was hit by COVID a bit later than other places and so it was possible to start flights when activity was really slow in other regions of the world.
The process started with building OptiFlight® Machine learning (ML) performance models using historical flight data from Viva Aerobus and collecting one year of actual flight data for each aircraft (figure 2).
Then, using Machine learning, the OptiFlight® team built predictive models that allowed them to predict the vertical profile, fuel burn and the flight time in different phases of flight. The OptiFlight® team continued to receive data from Viva Aerobus so that they could, first, measure the savings but also continuously refresh the tail specific performance models. Now, on a day-to-day basis, OptiFlight® collects the information for each specific upcoming flight from the flight plan plus weather information in order to be able to make tactical recommendations for each flight (figure 3).
This was done using OptiFlight®’s predictive models to run tens of thousands of scenarios, virtually flying the aircraft in order to be able to predict the fuel burn for each scenario and recommend the best scenario to the pilots. The way that the recommendations are sent to the pilots is in the briefing package which we’ll look at below.
Because the aim was to get the most efficient outcome as soon as possible, the focus was on OptiClimb® to optimize the climb-out phase (figure 4).
Climb-out uses a high level of thrust during the first twenty to thirty minutes of the flight, so there is significant potential for savings; but it’s also the most complex phase of the flight with many parameters evolving as the aircraft ascends, such as winds and temperatures, altitude, the weight of the aircraft, the aerodynamics, the changing angle of attack and more. Because of this complexity, efficiency in the climb-out cannot be resolved in a simple equation and that is where the predictive models come into play. By virtually flying the aircraft in tens of thousands of scenarios, the fuel burn can be predicted for each of them to make the best recommendation to pilots.
Those recommendations come in the form of recommended climb speeds; there are two indicated air speeds and one climb Mach being used for the climb phase. Instead of using 250kt to flight level 100, which complies with the regulation which says 250kt maximum up to a minimum of 10,000ft, you can actually use a lower initial speed. A lower indicated air speed is a lower horizontal speed resulting in a higher vertical speed with a higher climb angle to get higher sooner where less fuel will be consumed. You can see in the example in figure 4 we’re actually using a first speed of 241kt instead of 250kt and then that speed is being maintained not just to flight level 100 but to flight level 120 maintaining the initial climb angle to get higher sooner whereas, if the pilot accelerates at flight level 100, as ECON (ECONomy mode for flight cost index) always does, that will increase the horizontal speed, decreasing the vertical speed and flattening the trajectory, staying low.
The aircraft will then accelerate to a second IAS (Indicated Airspeed) speed, in this example at FL 120 (speeds and acceleration altitudes are different for each flight). This speed will be based on the altitude at which the speed change is made but also taking into account winds and temperatures every one thousand feet. Finally, we’ll use a climb Mach instead of using the Cruise Mach for the final phase of the climb because, if you use the cruise Mach at a lower altitude than cruise, that will result in a higher True Airspeed than the final True Airspeed which is a loss of energy. This is not a policy, it’s something that comes out of predicting tens of thousands of scenarios and usually this is what OptiClimb® finds; a lower speed than 250kt or 250kt itself but maintained to a higher altitude and a lower climb MACH than the cruise MACH or equal to the cruise MACH. This is why climb-out offers a systematic savings opportunity because we can actually bring the aircraft to the same point and distance at the same time – we don’t want to compromise on time, we want to respect the Cost Index of the airline so OptiClimb® will only make those recommendations that achieve the same results in time but save fuel thanks to a more optimal trade-off between horizontal and vertical speeds.
TESTING OPTICLIMB®AT VIVA AEROBUS
All of that makes a lot of sense but how can an airline or operator make sure that what a vendor is trying to sell to them is right for their airline. When they try to put new solutions or new software into their businesses, what they want to be sure of is that it’s actually saving money because, of course, all of these solutions have a cost. So how can airlines and operators actually make sure that those promised savings will be realized? This is why, for Viva Aerobus, it was very important to have a proof of concept for the proposed solution.
Figure 5 will give readers an understanding of why Viva Aerobus took the decision to implement OptiClimb® and why it was quite an easy decision to make. With this proof of concept, the airline could see the results that they wanted to have for the business.
Viva Aerobus ran a trial campaign from April to July 2020, a four-month trial period which seems a lot of time but that was at the start of the pandemic so there was not a lot of flying taking place. But the airline wanted to gather a lot of data in order to generate a good case for the business. Prior to the trial, Viva Aerobus shared historical data with OptiFlight® in order to build the models and then, when the trial was underway with real operations and day-to-day flights, the best recommendations could be generated for the specific conditions encountered on those flights because they took into account the actual weight for that mission as well as the weather and other material conditions.
In this trial, Viva Aerobus saw an outstanding application rate for OptiClimb® of 83%. That enabled the airline to analyze almost four thousand flights with an average of 71kg of fuel saved per climb compared to the standard climb profile at the time. That was why the decision was quite easy and why Viva Aerobus was very comfortable moving forward with the solution.
It was an outstanding application rate which was very useful because it meant a lot of OptiClimb® flights to analyze. The first step in the analysis is to look at the flight data to see whether the pilots have applied the recommended speeds, not just any speeds but selected speeds where it can be seen that there was a pilot action to choose the speeds that the solution recommended. Then, for each of the nearly four thousand OptiClimb® flights, using the same predictive models that were used before the flights but this time with the parameters from the actual flight itself, using the aircraft’s sensors, it was possible to predict what would have been the equivalent ECON flight in the exact same conditions. That allowed the solution to come up with savings for each OptiClimb® flight. In figure 6, you can see the distribution of those four thousand flights based on take-off weight and top of climb.
Figure 6 shows that, when the flights go higher, they conserve and save more fuel. Within the ellipse is where there was the highest concentration of flights and it can be seen that the numbers are converging towards the average fuel saving of 71kg or 72kg of fuel saved per climb.
ACTUAL SAVINGS ACHIEVED
Viva Aerobus started operations with OptiClimb® as the standard operating procedure in the company on January 1st 2021 and the results that were gathered for that first year of operation (figure 7) delivered an average fuel saving per climb of 72kg.
The application rate was also 72% and the cumulative savings for the year were 5,000 tonnes total fuel saved compared to the previous climb procedures. That all translated into a carbon footprint reduction of more than 15,000 tonnes of CO2 over the 96,000 flights analyzed. You won’t be surprised to know that Viva Aerobus was very happy with those results.
PROVIDING THE RECOMMENDATIONS TO PILOTS
It was very important to the Viva Aerobus that, when the trial campaign was carried out, they actually worked with the crews in order to get their impressions of how they felt about the solution but also, how was their reception of the information and if it was easy for them to receive it, to use it and to analyze it (figure 8).
While, at the beginning, this information was being sent by email, as the airline was also moving forward at the same time with developing an in-house EFB solution, the team developing the EFB was able to incorporate this into the briefing package (figure 9).
Nowadays, the crews receive all of the crucial information for their flight in the flight package on the same screen as the Weight & Balance, the Flight Plan, etc. in the OptiClimb® briefing. This is very useful for them and the airline is very happy to have been able to do that with SITA for Aircraft.
Sometimes there are some ATC directives that impact on using OptiClimb® and there might be airport requirements such that the OptiClimb® profile cannot be flown. It doesn’t happen often but there are cases. Viva Aerobus’s instruction to pilots is to try to follow the whole recommendation through the whole climb phase, as we said above, but if they are asked by ATC to, say, speed up in order to separate the traffic, they must comply. It is important to mention that even if the pilot doesn’t follow one hundred percent of the OptiClimb® recommended climb profile for a flight, there will still be savings.
Also, airlines will want to be sure that, in making fuel savings, they are not increasing maintenance costs. OptiFlight® has a partnership with Safran which is an engine manufacturer who looked at OptiClimb® flight profiles and deduced that reaching top of climb earlier puts less strain on the engine and is actually likely to be reducing maintenance costs
THE BIGGER PICTURE
Before we close the article, there has been a lot of talk about efficiency, mainly fuel efficiency, but what is the reason why an airline like Viva Aerobus would do this? There are two main reasons. Of course, when we talk about fuel, that is directly related to cost because, in the case of Viva Aerobus, fuel accounts for more than fifty percent of the total cost of operations; so, when we are talking about fuel efficiency, we are talking about money.
And it’s really important to not forget that we are also actors in the drive for sustainability and aviation is contributing to reduce the global CO2 footprint. Sometimes we might think that the actions we are taking are meaningless. But, if we all hold ourselves accountable to do so, we can really make a difference and it’s very important not to forget that. We might also think that disrupting technologies, such as OptiClimb®, have no impact but they really do. It’s really important for all of us in the industry to seek for all the solutions out there, give them a try but in the event that they let airlines and operators try out campaigns and proofs of concept, it can be seen that there’s an impact. So, we would really encourage readers to look for these disruptive solutions like OptiClimb® to really make a difference, not just for cost but also for sustainability, a win-win for all involved.
After graduating in Aeronautical Engineering from Universidad Autónoma de Nuevo León, Paola joined Viva Aerobus in 2017 as a Flight Operations and Performance Engineer. In 2020, she was appointed Fuel Conservation and Performance Chief and, in 2021, Operations Engineering Manager. Paola has experience with Airbus A320 Boeing 737 fleet fuel consumption analysis as well as performance analysis support for performance engineers. She also has experience with Lean and Six Sigma projects.
With previous experience in Bureau Veritas and Airbus, François Joined Safety Line in 2016 as Chief Commercial Officer. In 2021, when safety Line became part of SITA FOR AIRCRAFT, François was appointed Head of Sales Support, Safety Line then, in 2022, VP Commercial Middle East & Africa for SITA FOR AIRCRAFT. Later in 2022, François was appointed Head of Sales Support, Flight Efficiency, SITA FOR AIRCRAFT.
As the most profitable and accessible low-cost airline in Mexico, Viva Aerobus has carried more than 64.5 million passengers in its 17-year history, thanks to the efforts of its more than 3,000 employees and a well-structured business model. The fleet includes 64 aircraft from the Airbus A320 family of Airbus A321 and A321, both CEO and NEO versions. The fleet is recognized as the youngest in Latin America and there are further new aircraft on order.
SITA FOR AIRCRAFT
SITA For Aircraft represents the aircraft arm of SITA, the IT provider for the air transport industry, delivering solutions for airlines, airports, aircraft and governments. Today, SITA drives operational efficiencies at more than 1,000 airports. SITA’s technology provides solutions that help more than 40 governments strike the balance of secure borders and seamless travel, while delivering the promise of the connected aircraft to more than 400 airlines on 17,000 aircraft globally.