- Home
- » Flight Phases
- » Flight Phase 3
Flight Phase 3: Enroute Cruise
Enroute Cruise involves the part of the flight in which the aircraft is operating on its flight-planned route at 'optimum' altitudes for the weight and engine configuration of the aircraft to enable it to fly between its departure and arrival points as efficiently and comfortably as possible.
This is the portion of the flight where the majority of emissions are produced. It is therefore not surprising that historically most of the aviation focus has been on implementing operating techniques that minimise the total costs in this phase. The principles of how to operate a jet aircraft to achieve minimum fuel burn have been known for decades. What has changed since the early 1980's has been the gradual increase in technology to assist airlines and pilots to operate at optimum speeds and altitudes. Today's modern jet aircraft, such as the B777, use a Flight Management Computer loaded with databases of the aircraft's performance coupled to a modern efficient autopilot and auto throttle systems.
Click here to learn more about the calculation of the flight's cost index
What used to happen?
Traditionally, this phase of flight involved the aircraft flying a fixed route between the departure and destination airports, with fixed waypoints in between, which the aircraft was required to fly over so that air traffic controllers could use the aircraft's speed and altitude information at each waypoint to ensure a safe separation from other aircraft. There was some ability for the pilot to avoid bad weather by deviating off track, but the complication for air traffic controllers was that this made calculating the aircraft's position difficult, to ensure its continued safe separation from other aircraft. Often this involved a flight level change for an aircraft to achieve such a route deviation to ensure separation was maintained, but could often mean that the aircraft was required to fly at its less than 'optimum' flight level.
What are we doing today?
Over New Zealand and US oceanic airspace, like most other aircraft flying the route today, Aspire 1 will take advantage of some of the most advanced and sophisticated air navigation services currently available to aircraft anywhere in the world, in order to reduce its emissions.
User Preferred Routes, or 'UPR's' as they are known, are individual routes in the sky specifically designed for each flight after taking into account forecast winds, and the weight and engine configuration of the aircraft.
UPR's are becoming increasingly effective as the aircraft are able to commence their 'preferred' optimum routing much closer to the departure and destination airport than previously. Outbound from Auckland, aircraft can now commence their UPR route right from the airport runway. Currently that UPR capability finishes as the aircraft enters domestic US airspace.
Click here to learn more about UPR's
Aspire 1 will also able to 'DARP' enroute. In other words, the pilot can elect to alter the User Preferred Route once updated wind and weather information becomes available during the flight. This is known as a Dynamic Airborne Reroute Procedure, and it is currently only available to aircraft flying within New Zealand and US oceanic airspace.
Click here to learn more about DARPs
Aircraft on this route between New Zealand and the US can also take advantage of the most efficient reduced aircraft separation standard currently available globally. This separation standard is 30 nautical miles longitudinally and 30 nautical miles laterally, and allows aircraft to safely fly with less separation between them than previously. This means that each aircraft's optimum flight level is more often available to them as they elect to fly their 'preferred route' through this airspace.
Click here to learn more about 30x30nm separation
Why are we doing it?
Air Navigation Services providers can have a significant impact on the emissions optimisation of a flight by allowing the aircraft to fly as close to its optimum flight profile as possible in terms of route and altitude, and by making changes to the profile as often and as quickly as possible to allow it to maintain its optimum flight profile. Over long distances the benefits of these procedures are significant as weather patterns that change along the route after the aircraft's departure can be incorporated into the aircraft's 'preferred' or optimum flight profile. The result is substantial savings in emissions for each flight.
What does this mean in terms of the bigger picture?
Where this combination of advanced ATC and Airline systems exist, it enables the aircraft in the enroute environment to be consistently operated at a speed and altitude which provides the greatest efficiency. When combined with a route that is unrestricted and can be planned to take full advantage of the weather forecasting available the aircraft can operate the most efficient profile and therefore the least environmental impact.
Click to see how these emissions savings contribute to savings across the entire flight
Flight Phase Information
Click on a Flight Phase to learn more.
In this section
What does this mean in terms of the bigger picture?
Useful Links for this Flight Phase
The calculation of the flight's cost index
Larn more about 30x30nm separation
See how emissions savings in this flight phase contribute to savings across the entire flight
