Arrivals Optimisation includes any one of several procedures available to aircraft operators and air navigation service providers to improve the fuel efficiency for aircraft during final descent phase of a flight. Qualifying arrivals optimisation procedures include, continuous descent arrivals, continuous descent approaches, optimised profile descents, tailored arrivals, and are generally referred to by ICAOas Continuous Descent Operations.
Optimum Profile Descents
An Optimum Profile Descent (OPD) is a cockpit-based flight technique where the vertical profile of an arrival is optimised to minimise undesired level flight segments so that the aircraft can be flown with engines at idle thrust from a high altitude, potentially from cruise, until touch down on the runway. Aircraft executing an OPD realise a far more efficient fuel burn profile and reduced emissions during the descent and arrival phases of flight, as compared to a traditional arrival path. A variety of OPD applications have been analysed and developed for fuel and emission efficiency improvements.
OPD via RNAV and RNP-AR Approaches
Where conditions will allow, arrival, departure and en route traffic flows will allow, descent profiles and airspace restrictions on published Area Navigation (RNAV) and Required Navigation Performance � Authorisation Required (RNP-AR) approaches are modified to provide more optimum arrival profiles. This optimisation reduces fuel burn and carbon emissions by taking advantage of the sophisticated navigational capability of modern aircraft that can fly closer to optimal tracks and altitudes.
For example, RNP-AR approaches are conducted using idle power, continuous descent from an optimally chosen top of descent point. In Australian RNP-AR implementations, this has typically saved around 200Kg of fuel per approach. This results in a reduction of 620Kg of CO2 emission per approach. During the first 18 months of implementing RNP-AR OPD, Airservices Australia estimates that 33 B737-800 aircraft have conducted more than 10,000 RNP-AR approaches. The estimated cumulative savings in jet fuel is 345,240 kg with estimated carbon dioxide emissions reductions of 1,151,280 kg.
OPD via Tailored Arrivals
Another application of OPD procedures, known as a Tailored Arrival (TA), is a procedure where trajectories are dynamically optimised for each aircraft to permit a fuel-efficient, low-noise descent profile that has imbedded compliance with arrival sequencing requirements and other airspace constraints.
Operational trials in Australia, New Zealand, and the United States have demonstrated that both types of OPD described above provide significant fuel and emissions savings. Although the successful execution of an uninterrupted OPD is greater during periods of light traffic, the INSPIRE partners are pursuing the use of OPD during congested traffic periods under the INSPIRE Work Program.