Speed optimisation in NAVsystem

03. 04. 19

Speed optimisation is one of the airline operational efficiency areas where a potential for cost saving goes to double digits percentage-wise. The total absolute money savings every year are then hardly negligible. Several surveys have indicated that many airlines are still missing the full benefits of speed optimisation. That is why we decided to provide an overview of best practices and tools available in NAVsystem in this short article.

Basic idea of speed optimisation is to find a balance between fuel costs and flight time related costs (derived from maintenance, lease conditions, airline business model, crew costs, etc.) to minimise the overall cost of the mission/flight. A philosophy of Cost index (CI) was introduced for that purpose – simple formula combining fuel costs and time related costs. The CI allows to recalculate flight time to kgs of fuel and vice versa. Time related costs and fuel costs are typically confidential information, and using CI principle is allowing to use the benefits without actually disclosing the any financial data.

Speed optimisation techniques differ a little bit depending on aircraft (A/C) capabilities. Most modern A/C have the capability to operate in an „ECON“ speed mode in cruise (ECON may be called differently depending on the A/C manufacturer, but the principle remains the same). This ensures that the A/C is flying at an optimum speed at all times. Operations Control Centre (OCC) provides the CI for every given route/flight and the value is entered into Flight Management System (FMS) by flight crew. In NAVsystem, it is possible to track fuel prices on different airports and time related costs for each A/C separately. This allows dynamic calculation of CI for each flight. NAVsystem support ECON speeds in OFP calculation so that fuel uplift is also optimised.

For A/C that do not support ECON speed mode, the overall optimisation task gets a little more complicated. Even then NAVsystem allows you to easily calculate and compare overall cost per flight (considering both flight time and fuel burn costs) at different speeds. This allows you to select the optimum Mach speed (or other cruise mode) for given flight considering forecast wind & temperature, gross weight of the A/C and planned FL. Flight crew should be aware of the fact, that the speed is optimised for flight plan conditions, e.g. in case they are not able to fly at a planned FL (conflicting traffic or generally ATC interventions) they should adjust their speed accordingly. Giving the crew an optimum speed at 2000ft around the planned FL by OCC suddenly becomes really helpful. This maintains a very high level of operational efficiency even in crowded airspace where flying at an optimum FL is not always possible.

Nav flight services
Speed optimisation NAVsystem 1

The situation gets even more complicated when fuel tankering is desirable. An optimum CI for a given flight must then be the average cost of fuel, i.e. combining fuel cost at given airport with cost of tankered fuel including a cost to carry.

Nav flight services
Speed optimisation NAVsystem 2

Fuel tankering with accurate calculation of cost to carry is another efficiency feature of NAVsystem that significantly contributes to reduction of airline operational costs.