2.2.2 Environment
Efficiency and environment
The ANS related impact on the
environment is closely linked to
operational performance (fuel efficiency)
which is largely driven by inefficiencies in
the flight trajectory and associated fuel
burn (and emissions). The current best
estimate for 2019 is that ANS can
influence approximately 6% (11.6 Mt) of
the total gate-to-gate fuel burn (“benefit
pool”).
The overview below shows a
consolidated view of the main components
Horizontal en-route flight efficiency
The horizontal en-route flight efficiency indicator is computed for three different trajectories:
(1) the actual flown trajectory, (2) the planned trajectory according to the flight plan and (3)
the shortest constrained route provided by the Network Manager. It is expressed as a ratio of
distances and is therefore an average per distance within a given airspace (distance achieved
per distance flown).
The shortest constraint route (SCR) reflects the effect of the constraints imposed by
ANSPs (route structure, airspace availability, etc.) on flight planning. It is not influenced
by weather conditions or specific airline considerations, and it sets the limits within
which the airlines can optimise. The filed flight plan takes into consideration not only those constraints, but also other
factors which are linked to airlines’ preferences (including cost considerations and
trade-offs). The filed flight plan must always be at least as long as, if not longer than,
the SCR.
Finally, the actual flown trajectory is based on the flight plan but is influenced by
unforeseen or unplannable factors at the time of filing, including weather and tactical
ATC routings. Some of these modifications might lead to a lengthening of the
trajectory, while others will lead to a shortening of it.Horizontal en-route inefficiencies impact in terms of fuel burn and emissions. The lower the
efficiency, the higher the additional fuel consumption and emissions.