Continuous descent operations with controlled times of arrival at one or several metering fixes could enable environmentally friendly procedures without compromising terminal airspace capacity. This paper focuses on controlled time of arrival updates once the descent has been already initiated, assessing the feasible time window (and associated fuel consumption) of continuous descent operations requiring neither thrust nor speed-brake usage along the whole descent (i.e. only elevator control is used to achieve different metering times). Based on previous works, an optimal control problem is formulated and numerically solved. The earliest and latest times of arrival at the initial approach fix have been computed for the descent of an Airbus A320 under different scenarios, considering the potential altitudes and distances to go when receiving the controlled time of arrival update. The effects of the aircraft mass, initial speed, longitudinal wind and position of the initial approach fix on the time window have been also investigated. Results show that time windows about three minutes could be achieved for certain conditions, and that there is a trade-off between robustness facing controlled time of arrival updates during the descent and fuel consumption. Interestingly, minimum fuel trajectories almost correspond to those of minimum time.Peer ReviewedPostprint (published version

A compromise solution to increase flight efficiency in cruise, but without penalising capacity (or even safety), would be perhaps to remove (or relax) the minimum rate of climb (ROC) constraint and/or to reduce the height of the step climbs in cruise. In this paper, the benefits (in terms of total operating costs) and the associated impact on the air traffic management (ATM) of such “relaxed cruise” operations are quantified for a representative medium-haul aircraft under different scenarios, by means of an in-house trajectory optimisation software. Results show that by reducing the minimum ROC from 500 to 300 ftmin-1, whilst keeping the step climb height according to current reduced vertical separation minima (RVSM) standard would give a good compromise between cost savings and impact on the ATM.Peer ReviewedPostprint (published version

Continuous descent operations (CDOs) with required times of arrival (RTA) have been identified as a potential solution for reducing the environmental footprint of aviation in the terminal maneuvering area without compromising capacity. This paper assesses the feasibility of replacing current air traffic control sequencing and merging techniques, mainly based on path stretching and air holding, by a control based on RTA over metering fixes on known and fixed arrival routes. Because the remaining distance to the runway threshold is always known by the aircraft crew, this would allow engine-idle CDOs that do not require speed-brake usage and where only elevator control is used to meet the RTA. The assessment has been performed for Barcelona-El Prat Airport (Spain) using historical traffic demand data. The earliest and latest trajectories at a metering fix for each inbound aircraft were computed assuming engine-idle CDOs. Given the attainable RTA window for each aircraft, the aircraft sequencing problem was solved. The results show that assigning RTA allows optimizing the landing sequence when air traffic is low. For scenarios with high-traffic loads and late RTA assignments, path stretching still was found to be necessary. The minimum distance from the runway where inbound aircraft should receive the RTA to fully remove any radar vectoring was also analyzed. It was demonstrated that the assignment of RTA well before starting the descent would favor to enable full CDOs.