CASE STUDY: Real-time flight path optimization at Volaris

Author: Luis Fernandez San Miguel, Fuel Efficiency Manager, Volaris and David Rytter, CEO, AVTECH

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Luis Fernandez, Fuel Efficiency Manager, Volaris and David Rytter, CEO, AVTECH share leveraging a flight profile optimizer solution for eco-efficiency flying

Case studies are always valuable because they not only tell readers about the product but also relate a story of how the product was implemented in and performed in an airline environment. So, before diving into the topic for this case study, let’s first look at the subject airline, Volaris.

VOLARIS

Volaris, the largest Ultra-Low-Cost Carrier (ULCC) in Latin America, flew 33.4 million passengers on 245 routes in the twelve months to June 2023.

The fleet includes 124 aircraft with most of them neo models and operated to and from 71 airports on three AOCs (Air Operator Certificates) – one in Mexico, one in Costa Rica and one in El Salvador.

Now we’ll look at the solution that has delivered real and measurable savings and efficiency gains to Volaris.

CLEARPATH

ClearPath is a real-time flight path optimization service that has been built to be easy to implement and to start using in an airline environment. The solution uses existing on-board technology, so requires no investment other than the investment in ClearPath itself – any airline with an FMS (Flight Management System) and with ACARS connectivity will be good to go. The solution calculates a cost optimal flight path based on the cost index (CI) that the pilots have entered into the flight management computer (FMC) with the active flight path, weight and other factors.

It’s based on sit-down loads, small pieces of data, and uses the computational power on the ground together with the high-resolution weather, high-resolution performance model and actual flight parameters to calculate a fully cost-optimal flight profile. The flight profile is then automatically uplinked to the pilots who can request new authorizations for the flight which can be presented on an EFB, or on the cockpit screen or printer.

There are real savings for airlines that have trialed ClearPath with average savings of up to two and a half percent fuel and CO₂ reductions in the cruise phase. We’ll explain how it works.

After take-off, or even pre-departure, the system automatically downloads the information, the cost index and active flight plan, from the FMS. Based on this, the system calculates a 4D trajectory of the flight and retrieves high-resolution weather forecasts for the specific flight; it then does a ClearPath full optimization of the flight which is delivered back to the cockpit and the pilots.

This is a flight sample of a Boeing 787; rather an extreme case but good to show how ClearPath works. On the left of the image, the black line is the OFP (Original Flight Plan), how the flight was planned, while the blue line is the ClearPath recommendation. To the right of the figure, you see the message that was uplinked to the pilots. This was pushed during climb at around 16,000ft and it presents the pilots with really simple readable information and a simple message showing what, if they can follow it, would be the most optimum flight profile for this flight, at this time/day. They also get presented with what would the potential savings be if they can follow and achieve this profile. Also, this year, AVTECH has added a new feature to ClearPath, ‘Avoidance of In-Flight Hazards’, turbulence and temperature avoidance.

ClearPath has really great turbulence forecast information which is based on the same weather forecast that the system uses for winds and for temperatures. With this information, ClearPath can now provide pilots with a turbulence warning delivered automatically, after departure, if there is turbulence along the flight path above an airline’s threshold. The system allows airlines to specify those turbulence thresholds according to different aircraft types even down to individual aircraft, ClearPath will notify the pilots and even tell them the most cost-optimal way to avoid the turbulence.

Of course, what really matters is how the solution worked in a live airline environment. So, let’s have a look at how it has worked for Volaris.

CLEARPATH FLIGHT OPTIMIZATION IN VOLARIS

The first question that any airline would want to answer about ClearPath is, are the savings that are being sent to the pilots the real ones? Here is how Volaris answered that question.

ClearPath savings analysis

In order to perform this analysis, Volaris made an audit including the flight with all the fields used during the flight. When the auditor comes to the airline, he will want a sample of 1,000 flights to show the exact results for those flights. In Volaris’ case, the airline took five random flights and then analyzed them with the FDL data and the ACARS data; the results that ClearPath was giving were near spot-on. Volaris did obtain more savings in one case than ClearPath was saying but that was not regarded as accurate.

In practice, it was not easy to find five flights to analyze because it had to be taken into account that the lateral performance of the flight has to be as similar to the flight plan as possible. Because pilots sometimes take directs and given that the ATC will be better on one flight than on others: it was difficult to find five flights that flew perfectly, or almost perfectly, the flight plan provided. Also, on the figure you can see the data from the flight used, it was a flight from Los Angeles to El Salvador with the plan in the EFB showing flight level 350 and the ClearPath, message at the top right of the figure, suggested flight level 370. The final route that the pilots followed was at 370 as proposed by ClearPath.

Also, on the right of the figure, you can see the different profiles for that flight; the red one, for example, is for the OFP, the flight level of the flight plan. The flight level that ClearPath proposed is in purple; the flight level that the FMS proposed is in green and the actual flight level is blue. As you can see, ClearPath was also proposing some 1,300 miles from the start of the cruise, it’s quite a long flight, to make another step. However, when Volaris contacted the pilot of this flight, he explained that the ATC had said that was not possible to perform that step. Finally, it was not what we wanted in an ideal world to compare with the results of ClearPath but we can see, in the table at bottom right, is that the savings that ClearPath was showing in the message were at least the same as or, as in this case, better than expected. The key message is that there were savings.

ClearPath performance

Looking the ClearPath performance in Volaris during the first four months of use, the airline divided the study into two periods, the first two months, April and May 2023, and then the period covering June and July, because the performance varies, it is not the same during low season as it is during summer, which is why the study was divided into two periods but here are the final results that were obtained during this four-month period.

Around 40 percent of flights in the study were flights optimized by ClearPath, a further 36 percent were already optimized by the flight plan and, for a further 25 percent of the flights, there was a lack of data and the airline was not able to share with AVTECH 100 percent of the flight plans in this case so they were not optimized.

There was quite a large sample of more than 66,000 flights from which 40 percent were optimized by ClearPath but in those flights there was an average fuel saving of 96 kg per flight, including some time savings and some flight level optimization savings. As already mentioned, Volaris has three AOCs so the results were broken down by carrier.

With more than 80 percent of Volaris’ flights, the most important AOC for the carrier is Mexico. In figure 7, on the right are three sets of columns. In each case, the first one (green) shows the total saving that could be obtained if there was 100 percent pilot engagement with ClearPath. The airline does not know how many of the actual engagements (gray) are because the ATC didn’t allow the pilot to perform the ClearPath profile so it’s a mix between pilot engagement and ATC restrictions. The most potential was for Costa Rica flights because they are longer flights so the cruise phase is longer and the results will be better. In the second column is the actual engagement potential but excluding the lack of data mentioned above. The column in purple shows the actual result that Volaris obtained for the three carriers. As you can see, there is a low engagement level but, as already stated, the airline cannot tell whether that is because the pilot didn’t want to use ClearPath or whether the ATC is putting some restrictions on the flight levels to which the aircraft is permitted to climb.

Finally, taking into account just the 40 percent of flights that were optimized, which was more than 26,000 flights, there was, as seen above, an average saving of 96kg per flight. The problem was that not all of those 40 percent of the flights were accepted by the pilot and here are the results for the two periods of the study, April and May, and June and July.

In the first period, the savings that ClearPath was giving to Volaris’ pilots were better than in the June and July period but it was important to discover why. Although the average savings that ClearPath was giving during the four months were 96kg per flight, taking into account that not all the ClearPath suggested flights were performed by the pilots, the final result obtained, the two columns show the actual results in purple with, in grey, the result if all of the OFPs had been passed to AVTECH. Finally, Volaris obtained a total result of 14 kg per flight better than the OFP. These are not the real results; they are taking into account that the baseline for these savings is the OFP.

Total pilot engagement was around 56 percent of the total number of flights that AVTECH optimized and here is more information about the routes that were most used and which ones were more optimized by base. There was a net saving result, the Volaris performance versus the FMS baseline.

This is not the FMS baseline itself but it’s the actual results versus the use of the FMS by the pilots. You know that when a pilot records the actual flight performance, they can know which is the optimal FMS flight level; so, some pilots might try to use this FMS flight level to tell ATC that they want to follow or try to follow this FMS performance. Volaris, compares similar conditions so uses the same month from last year but, as can be seen, for the first period, April and May, the actual altitude is greater than the OFP altitude and, obviously less than the optimal one that is given by the FMS. However, in the next period, June and July the summer period, last year the actual altitude was lower than the OFP altitude. And, with ClearPath, the trend has changed and now is almost greater than the OFP one. The net savings obtained versus the actual performance of Volaris pilots was 15kg for both periods; we said before that versus the OFP in the second period, the saving was 14kg but, in this case, the net saving versus the actual operation of Volaris pilots is 15kg in total.

Improvements, conclusions and next steps

Finally, the conclusions from the implementation and the challenges that Volaris faced during that time. The greatest challenge when the project started was that all Volaris aircraft had the FMS locked, the ACARS uplink. The calculations were being made with just the OFB data so there was a lack of data in terms of weight and the performance that the pilots were then using when they performed the calculation for the flight profile. Also, during that period, Volaris implemented the new ClearPath turbulence and temperature avoidance model in order to engage pilots to use the service more. And, finally, as ClearPath was comparing with the baseline of the OFP, the final savings would depend on flight planning accuracy or performance to make the most of the planned flight or to calculate the most of the optimized flight; it’s also related to the Zero Full Weight Error there could be. The FMS usage by the pilots, the ECON FMS profile used by the pilots, then ATC allowance to perform the ClearPath profiles and finally, the pilot engagement to use the service all have contributed to the success of the solution on Volaris.