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.
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.
Continuous Descent Operations with Controlled Times of Arrival (CTA) at one or several metering fixes could enable environmentally friendly procedures without compromising capacity. This type of flight operation requires advanced on-board systems not only able to compute a plan satisfying Required Times of Arrival (RTAs), but also to safely and efficiently guide the aircraft during the execution of the descent such that RTAs are accurately accomplished. The primary aim of this paper is to compare the performance (in terms of environmental impact mitigation and ability to fulfill operational constraints) of four guidance strategies: tactical, strategic, hybrid and Model Predictive Control (MPC). A high fidelity flight simulator has been configured, and several descents to Barcelona-El Prat airport (Spain) have been simulated in presence of weather forecast and aircraft performance modeling errors. Results show that MPC is the most robust in terms of energy and time deviation, providing at the same time excellent environmental impact mitigation.
State-of-the-art weather data obtained from numerical weather predictions are unlikely to satisfy the requirements
of the future air traffic management system. A potential approach
to improve the resolution and accuracy of the weather predictions
could consist on using airborne aircraft as meteorological sensors,
which would provide up-to-date weather observations to the sur-
rounding aircraft and ground systems. This paper proposes to use
Kriging, a geostatistical interpolation technique, to create short-
term weather predictions from scattered weather observations
derived from surveillance data. Results show that this method
can accurately capture the spatio-temporal distribution of the
temperature and wind fields, allowing to obtain high-quality local,
short-term weather predictions and providing at the same time
a measure of the uncertainty associated with the prediction.
Xu, Y.; Dalmau, R.; Prats, X. Transportation research. Part C, emerging technologies Vol. 81, num. August 2017, p. 137-152 DOI: 10.1016/j.trc.2017.05.012 Data de publicació: 2017-08-01 Article en revista
This paper introduces a linear holding strategy based on prior works on cruise speed reduction, aimed at performing airborne delay at no extra fuel cost, as a complementary strategy to current ground and airborne holding strategies. Firstly, the equivalent speed concept is extended to climb and descent phases through an analysis of fuel consumption and speed from aircraft performance data. This gives an insight of the feasibility to implement the concept, differentiating the case where the cruise flight level initially requested is kept and the case where it can be changed before departure in order to maximize the linear holding time. Illustrative examples are given, where typical flights are simulated using an optimal trajectory generation tool where linear holding is maximized while keeping constant the initially planned fuel. Finally, the effects of linear holding are thoroughly assessed in terms of the vertical trajectory profiles, range of feasible speed intervals and trade-offs between fuel and time. Results show that the airborne delay increases significantly with nearly 3-fold time for short-haul flights and 2-fold for mid-hauls to the cases in prior works.
Dalmau, R.; Alenka, J.; Prats, X. AIAA Aviation Technology, Integration, and Operations Conference p. 1-12 DOI: doi.org/10.2514/6.2017-4260 Data de presentació: 2017-06-09 Presentació treball a congrés
Continuous descent operations (CDO) with required times of arrival (RTAs) have been
identified as a potential solution to reduce the environmental impact without compromising
capacity. However, in high traffic scenarios RTAs may not suffice to maintain safe separa-
tion, and air traffic controllers may still need to use "open-loop vectors", disabling CDOs
by depriving on-board flight management systems of required knowledge about the remain-
ing distance to go. This paper proposes to face peaks of traffic without using open-loop
vectors by combining the assignment of RTAs and pre-defined routes, taking advantage of
the flexibility that procedures such as the tromboning provide in the lateral domain. The
concept is illustrated by means of a practical example using the tromboning procedure of
the Frankfurt airport. For each possible shortcut of this tromboning, the feasible RTA
windows for engine-idle CDOs and powered descents have been computed using numerical
optimisation. Results show that time windows up to 10 minutes could be achieved with
engine-idle CDOs. These time windows could be widened up to 18 minutes by allowing the
use of thrust and speed-brakes, at the expense of burning more fuel and producing more
noise. Results also demonstrate that, for a given RTA, very distinct shortcuts could be
assigned such that the RTA fits into the associated feasible RTA window.
Continuous descent operations (CDO) with required times of arrival (RTAs) have been
identi ed as a potential solution to reduce the environmental impact without compromising
capacity. However, in high traffic scenarios RTAs may not suffice to maintain safe separa-
tion, and air traffic controllers may still need to use
Continuous descent operations (CDOs) with required times of arrival (RTAs) have been
identified as a potential solution to reduce fuel consumption and noise nuisance in the ma-
neuvering area and without compromising capacity. This paper assesses the feasibility of
replacing current air traffic control sequencing and merging techniques (mainly based on
radar vectoring) by a control based on RTAs over known and fixed arrival routes, aiming
to enable CDOs by ensuring flight management systems have an unerring knowledge about
the remaining distance to the runway threshold. The assessment has been performed for
Barcelona El Prat airport (Spain), using arrival traffic for several representative days gath-
ered from historical data. The earliest and latest trajectories at a metering fix for each
inbound aircraft have been computed assuming engine-idle CDOs. Given the attainable
RTA window for each aircraft, the feasibility of sequencing the arrival traffic with RTAs
has been assessed by solving an aircraft sequencing problem. Results show that low traf-
fic scenarios could be properly managed by only assigning RTAs. For certain scenarios,
however, with high traffic loads and late RTA assignments, radar vectoring would still be
necessary. The distance from the runway where inbound aircraft are expeced to receive
the RTA has been also subject of study, demonstrating that the assignment of RTAs well
before starting the descent would favor to remove radar vectoring and enable full CDOs.
TEMO (time and energy managed operations) is a
new concept that aims to optimise continuous descent operations,
while fulfilling with a very high accuracy controlled time of
arrival (CTA) constraints at different metering fixes. This paper
presents the results and main lessons learnt from two human-in-
the-loop experiments that aimed to validate the TEMO trajectory
planning and guidance algorithm: a full motion flight simulation
experiment and a flight testing campaign. Positive results were
obtained from the experiments, regarding the feasibility of the
concept and acceptance from the pilots. TEMO descents typically
showed lower fuel figures than conventional step-down descents.
Moreover, RTA adherence at the initial approach fix (IAF)
showed very good performance. Time accuracy at the runway
threshold, however, did not fulfil the (very challenging) time
target accuracies. Further work is needed to enhance the current
algorithm once the aircraft is established on the instrument
landing system glideslope.
From 9-26 October 2015 the Netherlands Aerospace Centre (NLR) in
cooperation with Delft University of Technology (DUT) has executed Clean Sky flight
trials with the Cessna Citation II research aircraft. The trials consisted of several
descents and approaches at the Eelde airport near Groningen, demonstrating the
TEMO (Time and Energy Managed Operations) concept developed in the Clean Sky
Joint Technology Initiative research programme as part of the Systems for Green
Operations (SGO) Integrated Technology Demonstrator.
A TEMO descent aims to achieve an energy-managed idle-thrust
continuous descent operation (CDO) while satisfying ATC time constraints, to
maintain runway throughput. An optimal descent plan is calculated with an advanced
on-board real-time aircraft trajectory optimisation algorithm considering forecasted
weather and aircraft performance. The optimised descent plan was executed using
the speed-on-elevator mode of an experimental Fly-By-Wire (FBW) system connected
to the pitch servo motor of the Cessna Citation II aircraft. Several TEMO conceptual
variants have been flown. It has been demonstrated that the TEMO concept enables
arrival with timing errors below 10 seconds. The project was realised with the
support of CONCORDE partners Universitat Politècnica de Catalunya (UPC) and
PildoLabs from Barcelona, and the Royal Netherlands Meteorological Institute
This paper describes a set of flight simulation
experiments carried out with the DLR’s Generic Cockpit
Simulator (GECO). A new concept named time and energy
managed operations (TEMO), which aims to enable advanced
four dimensional (4D) continuous descent operations (CDO), was
evaluated after three full days of experiments with qualified
pilots. The experiment focused to investigate the possibility of
using a 4D-controller on a modern aircraft with unmodified or
only slightly modified avionic systems. This was achieved by
executing the controller in an Electronic Flight Bag (EFB) and
using the pilot to “close the loop” by entering speed and other
advisories into the autopilot Flight Control Unit (FCU). The
outcome of the experiments include subjective (questionnaires
answered by pilots) and objective (trajectory logs) data. Data
analysis showed a very good acceptance (both in terms of safety
and operability of the procedure) from the participating crews,
only with minor suggestions to be improved in future versions of
the controller and the speed advisories update rates. Good time
accuracy all along the descent trajectory was also observed.
Continuous Descent Operations (CDO) with Con-
trolled Times of Arrival (CTA) at one or several metering fixes
could enable environmentally friendly procedures without com-
promising airspace capacity. Extending the current capabilities
of state-of-the-art Flight Management Systems (FMS), the Time
and Energy Managed Operations (TEMO) concept is able to
generate optimal descent trajectories with an improved planning
and guidance strategy to meet CTA. The primary aim of this
paper is to compare the performances of TEMO (in terms of fuel
consumption and time error) with respect to a typical FMS, that
is an FMS without re-planning mechanism during descent based
on time or altitude errors. The comparison is performed through
simulation, using an A320-alike simulation model and considering
several scenarios in presence of CTA and wind uncertainties.
Results show that TEMO is capable of guiding the aircraft
along a minimum fuel trajectory still complying with a CTA,
even if significant wind prediction errors are present. For a
same scenario, a typical FMS without re-planning capabilities or
tactical time-error nulling mechanism during the descent, would
miss the CTA in most cases.
Continuous descent operations (CDO) with con-
trolled times of arrival (CTA) at one or several metering fixes
could enable environmentally friendly procedures at the same
time that terminal airspace capacity is not compromised. This
paper focuses on CTA updates once the descent has been already
initiated, assessing the feasible CTA window (and associated fuel
consumption) of CDO requiring neither thrust nor speed-brake
usage along the whole descent (i.e. energy modulation through
elevator control is used to achieve different times of arrival at
the metering fixes). A multiphase optimal control problem is
formulated and solved by means of numerical methods. The
minimum and maximum times of arrival at the initial approach
fix (IAF) and final approach point (FAP) of an hypothetical
scenario are computed for an Airbus A320 descent and starting
from a wide range of initial conditions. Results show CTA
windows up to 4 minutes at the IAF and 70 seconds at the FAP.
It has been also found that the feasible CTA window is affected
by many factors, such as a previous CTA or the position of
the top of descent. Moreover, minimum fuel trajectories almost
correspond to those trajectories that minimise the time of arrival
at the metering fix for the given initial condition
High performance computing (HPC), both at hardware and software level, has demonstrated significant improve-
ments in processing large datasets in a timely manner. However, HPC in the field of air traffic management (ATM) can be much more than only a time reducing tool. It could also be used to build an ATM simulator in which distributed scenarios where decentralized elements (airspace users) interact through a centralized manager in order to generate a trajectory-optimized conflict-free scenario. In this work, we introduce an early prototype of an ATM simulator, focusing on air traffic flow management at strategic, pre-tactical and tactical levels, which allows the calculation of safety and efficiency indicators for optimized trajectories, both at individual and network level. The software architecture of the simulator, relying on a HPC cluster of computers, has been preliminary tested with a set of flights whose trajectory vertical profiles have been optimized according to two different concepts of operations: conventional cruise operations (i.e. flying at constant altitudes and according to the flight levels scheme rules) and continuous climb cruise operations (i.e., optimizing the trajectories with no vertical constraints). The novel ATM simulator has been tested to show preliminary benchmarking results between these two concepts of operations. The simulator here presented can contribute as a testbed to evaluate the potential benefits of future Trajectory Based Operations and to understand the complex relationships among the different ATM key performance areas
Speed reduction strategies have proved to be useful
to recover delay if air traffic flow management regulations are
cancelled before initially planned. Considering that for short-
haul flights the climb and descent phases usually account for
a considerable percentage of the total trip distance, this paper
extends previous works on speed reduction in cruise to the whole
flight. A trajectory optimization software is used to compute
the maximum airborne delay (or linear holding) that can be
performed without extra fuel consumption if compared with
the nominal flight. Three cases are studied: speed reduction
only in cruise; speed reduction in the whole flight, but keeping
the nominal cruise altitude; and speed reduction for the whole
flight while also optimizing the cruise altitude to maximize delay.
Three representative flights have been simulated, showing that
the airborne delay increases significantly in the two last cases
with nearly 3-fold time for short-haul flights and 2-fold for mid-
hauls with the first case. Results also show that fuel and time are
traded along different phases of flight in such a way the airborne
delay is maximized while the total fuel burn is kept constant.
The expected growth in air traffic combined with an increased public concern for the
environment, have forced legislators to rethink the current air traffic system design. The
current air traffic system operates at its capacity limits and is expected to lead to increased
delays if traffic levels grow even further. Both in the United States and Europe, research
projects have been initiated to develop the future Air Transportation System (ATS) to
address capacity, and environmental, safety and economic issues. To address the
environmental issues during descent and approach, a novel Continuous Descent Operations
(CDO) concept, named Time and Energy Managed Operations (TEMO), has been
developed co-sponsored by the Clean Sky Joint Undertaking. It uses energy principles to
reduce fuel burn, gaseous emissions and noise nuisance whilst maintaining runway capacity.
Different from other CDO concepts, TEMO optimizes the descent by using energy
management to achieve a continuous engine-idle descent, while satisfying time constraints
on both the Initial Approach Fix (IAF) and the runway threshold. As such, TEMO uses timemetering
at two control points to facilitate flow management and arrival spacing.
TEMO is in line with SESAR step 2 capabilities, since it proposes 4D trajectory
management and is aimed at providing significant environmental benefits in the arrival phase
without negatively affecting throughput, even in high density and peak-hour operations. In
particular, TEMO addresses SESAR operational improvement (OI) TS-103: Controlled Time
of Arrival (CTA) through use of datalink .
TEMO has been validated starting from initial performance batch studies at Technology
Readiness Level (TRL) 3, up to Human-in-the-Loop studies in realistic environments using a
moving base flight simulator at TRL 5 (-).
In this paper the definition, preparation, performance and analysis of a flight test
experiment is described with the objective to demonstrate the ability of the TEMO algorithm
to provide accurate and safe aircraft guidance toward the Initial Approach Fix (IAF), and
further down to the Stabilization Point (1000 ft AGL), to demonstrate the ability of the TEMO
algorithm to meet absolute time requirements at IAF and/or runway threshold and to evaluate
the performance of the system under test (e.g. fuel usage).
The APACHE project proposes a new framework to assess European ATM performance based on simulation, optimization and performance assessment tools that will be able to capture complex interdependencies between KPAs at different modelling scales (micro, meso and macro). In this context, the purpose of APACHE is threefold:
- to evolve the Performance Scheme towards new methodologies and metrics capable of capturing with proportional detail the performance drivers of ATM to foster a progressive and performance-driven introduction of new operational and technical ATM concepts in line with SESAR;
- to make an (initial) impact assessment of long-term ATM concepts with the new APACHE Performance Scheme, to measure the impact on ATM KPAs under different assumptions in line with the SESAR ConOps 2020\; and
- to analyse the interdependencies between the different KPAs at the Pareto-frontier of the ATM performance, by finding the theoretical optimal limits for each KPA and assessing how the promotion of one KPA may actually reduce the performance of the other KPAs
An initial performance assessment of new concepts of operations will be required, covering the new concepts t: free-routing in 2D (2DFR) and in 3D (3DFR) for airline operators; dynamic airspace configuration (DAC) for air navigation service providers (ANSPs); and dynamic demand and capacity balance (dDCB) for the Network Manager (NM). All these concepts will be analysed at EU-wide and/or functional airspace block (FAB) level combined under different scenarios and case studies.
The optimization tools will be used to model the ATM performance drivers underpinning each of the the stakeholder’s business models, in particular regarding the optimization of processes for aircraft trajectory planning, sectorization planning and network safety planning. Assessment tools will be used to measure the level of KPA performances in the simulations. Tools will be provided by partners and initial versions are already available.
This paper estimates the benefits, in terms of fuel and time, which continuous climb operations can save during the cruise phase of the flights, assuming maximum range operations. Based on previous works, a multiphase optimal control problem is solved by means of numerical optimization and using accurate aircraft performance data from the manufacturer. Optimal conventional trajectories (subject to current air traffic management practices and constraints) are computed and compared with ideal continuous operations only subject to aircraft performance constraints. Trip fuel and time for both concepts of operations are quantified for two aircraft types (a narrow-body and a wide-body airplane) and a representative set of different trip distances and landing masses. Results show that the continuous cruise phase can lead to fuel savings ranging from 0.5% to 2% for the Airbus A320, while for an Airbus A340 the dispersion is lower and savings lie in between 1% and 2%. Interestingly, trip time is also reduced between 1% and 5%.
In this paper an initial implementation of
time aircraft trajectory optimization
. The aircraft trajectory
for descent and approach is
minimum use of thrust and speed brake in
support of a “green” continuous descent and
approach flight operation, while complying with
ATC time constraints for maintaining runway
throughput and considering realistic wind
conditions. The trajectory opti
mizer forms an
important part of a new integrated, planning
and guidance concept name
TEMO (Time and
Energy Managed Operations) developed in the
Systems for Green Operat
ions (SGO) Clean Sky
compared with a
performance and environmental impact.
Continuous climb, cruise and decent operations (referred
as continuous operations) may contribute to significantly
reduce fuel and emissions. Nevertheless, it is obvious that the
introduction of such procedures at large scale is not possible with
the current air traffic management concept of operations, since
flying at constant altitudes is one of the key aspects to strategically
separate flows of aircraft. This paper tries to quantify what would
be the potential savings of flying such optimised vertical profiles.
A multiphase optimal control problem is formulated and solved
by means of numerical optimisation. Optimal conventional trajectories
(subject to realistic air traffic management practices and
constraints) are compared with optimal continuous (and ideal)
operations, only subject to aircraft performance constraints.
Results show that the continuous cruise phase can lead to fuel
savings between 1% and 2% of the total trip fuel for an Airbus
A320. Interestingly, continuous operations show also a reduction
of trip times between 1% and 5% of the total trip time, depending
on the trip distance between origin and destination airports.
'According to ICAO Doc 9931, a Continuous Descent Operation is an operation, enabled by airspace design, procedure design and ATC facilitation, in which an arriving aircraft descends continuously, to the greatest extent possible, by employing minimum engine thrust, ideally in a low drag configuration, prior to the final approach fix.
One of the main drawbacks of CDOs is their negative impact in airport/airspace capacity if current separation procedures are used. Thus, at present CDOs are usually flown during hours of low traffic demand in order to minimize ATC instructions leading to trajectory deviations and consequently to non-optimal operations. The Multi Parameter Guidance with Time and Energy Managed Operations (MPG-TEMO) is a novel Flight Management System (FMS) function developed in the framework of CleanSky that proposes to introduce strict time constraints in the CDO trajectory in order to give the ATC a powerful tool to cope with separation issues.
As stated in the call for tenders, the aim of this activity is to help define, prepare, perform and analyse two flight simulator experiments, which will be a prerequisite to the Flight-Test. Furthermore, the partner is supposed to support the a7c integration process prior to the Flight Test and with the final test result analyis.
One of the key aspects of the proposed solution is to focus first efforts of the project in identifying the main changes that bring MTG TEMO to the CDO standard procedure, in order to early draft the main operational, safety and certification issues that must be taken into account during the project. To do so, the leader of this consortium has sought the participation of the UPC Department that has been involved in the previous MTG TEMO projects for the CSJU.
Extensive background of proposed engineers, researchers, as well as, Pilot Manager and flight crew ensure early identification of problems and valuable solutions proposition while fulfilling CSJU project objectives.'
'In the conventional aircraft approach the aircraft receives clearance from Air Traffic Control to descent from the bottom level of the holding stack to a given altitude where it would fly level until intercepting the 3 degree glidepath to the runway. In this flight level segment the aircraft requires additional engine power to maintain constant speed, resulting in an increase of fuel consumption and noise.
A new approach procedure called Continuous Descent Approach (CDA) has been developed and is becoming widespread. In CDA procedures the aircraft stays higher for longer and then descends continuously, avoiding level segments, to the intercept point of the 3 degree glidepath. The CDA approaches reduce fuel consumption, CO2 and NOx emissions as well as noise levels.
To take full advantage of CDA approaches, the continuous descent paths can be optimized to decrease even more the fuel consumption and noise and pollutant emissions. This proposal addresses an onboard fast optimiser for continuous descent approaches which calculates descent profiles minimizing the use of engine thrust and speed brakes while meeting ATC time requirements and maintaining airport landing capacity.
To ensure a successful development of the fast optimiser, the Fastop proposal has been written by a consortium with remarkable parties skills that cover all the mathematical, programming and management needs required by the topic.'