Abstract:
Air transport has been a key component of the socio-economic globalisation. The ever
increasing demand for air travel and air transport is a testament to the success of the aircraft.
But this growing demand presents many challenges. One of which is the environmental impact
due to aviation. The scope of the environmental impact of aircraft can be discussed from many
viewpoints. This research focuses on the environmental impact due to aircraft operation.
Aircraft operation causes many environmental penalties. The most obvious is the fossil fuel
based fuel burn and the consequent greenhouse gas emissions. Aircraft operations directly
contribute to the CO2 and NOX emissions among others. The dependency on a limited natural
resource such as fossil fuel presents the case for fuel optimised operation. The by-products of
burning fossil fuel some of which are considered pollutants and greenhouse gases, presents
the case for emissions optimised operations. Moreover, when considering the local impact of
aircraft operation, aircraft noise is recognised as a pollutant. Hence noise optimised aircraft
operation needs to be considered with regards to local impacts. It is clear whichever the
objective is, optimised operation is key to improving the efficiency of the aircraft.
The operational penalties have many different contributors. The most obvious of which is the
way an aircraft is flown. This covers the scope of aircraft trajectory and trajectory optimisation.
However, the design of the aircraft contributes to the operational penalties as well. For example
the more-electric aircraft is an improvement over the conventional aircraft in terms of overall
efficiency. It has been proven by many studies that the more-electric concept is more fuel
efficient than a comparable conventional aircraft.
The classical approach to aircraft trajectory optimisation does not account for the fuel penalties
caused due to airframe systems operation. Hence the classical approach cannot define a
conventional aircraft from a more-electric aircraft. With the more-electric aircraft expected to
be more fuel efficient it was clear that optimal operation for the two concepts would be different.
This research presents a methodology that can be used to study optimised trajectories for
more-electric aircraft.
The study present preliminary evidence of the environmental impact due to airframe systems
operation and establishes the basis for an enhanced approach to aircraft trajectory optimisation
which include airframe system penalties within the optimisation loop. It then presents a suite of models, the individual modelling approaches and the validation to conduct the study. Finally
the research presents analysis and comparisons between the classical approach where the
aircraft has no penalty due to systems, the conventional aircraft and the more-electric aircraft.
When the case studies were optimised for the minimum fuel burn operation, the conventional
airframe systems accounted for a 16.6% increase in fuel burn for a short haul flight and 6.24%
increase in fuel burn for a long haul flight. Compared to the conventional aircraft, the more
electric aircraft had a 9.9% lower fuel burn in the short haul flight and 5.35% lower fuel burn in
the long haul flight. However, the key result was that the optimised operation for the moreelectric
aircraft was significantly different than the conventional aircraft. Hence this research
contributes by presenting a methodology to bridge the gap between theoretical and real
aircraft-applicable trajectory optimisation.