Sharing data could improve trajectory prediction
Sharing airline operational control (AOC) data with ATC could provide quick improvement to ground trajectory prediction, with limited investment. These are the conclusions raised by the SESAR project P5.5.2 in its final report to be delivered in May 2012.
Thanks to the involvement of NATS, EUROCONTROL and eight participating airlines (Air France, British Airways, FlyBe, Netjets, Novair, Swissair, United Airline and Virgin), SESAR P5.5.2 performed a series of exercises with the objective to:
- Assess ground ATC trajectory prediction (TP) improvements using AOC data (furnished prior to flight take-off) instead of assumed information (e.g. BADA);
- Evaluate the impact of the TP improvements on ATC medium term conflict detection tools, in terms of safety and efficiency;
- Provide a Cost-Benefit Analysis for ANSPs and Airspace Users.
In order to foster early implementation, only AOC data requiring minor modifications to ATC and AOC ground systems were considered. AOC data were supposed to be provided through point-to-point communications between FOC and ATC, rather than ATFN, or SWIM.
The evaluations were made on NATS operational system iFACTS using mass and speed from AOC flight planning systems, avoiding the need for airborne systems upgrade.
AOC data from the participating airlines (e.g. take-off mass and speed from flight planning systems) and ATC systems information (e.g. ATCO input, meteorological information) were collected for two days in the UK airspace.
This allowed comparison of the two following scenarios by replaying the traffic situation on iFACTS:
- Baseline scenario with ground trajectory predictions made using aircraft mass and speed assumptions (pre-determined information)
- "AOC data" scenarios using AOC mass and/or speed data, known by flight planning systems before take-off.
It was anticipated that TP accuracy improvements would result in reduced false and missed conflicts alerts rates from tools like MTCD (medium term conflict detection). This has been tested using both air traffic controllers‘subjective assessment and quantitative modelling.
Furthermore, two costs-benefits analysis workshops have been facilitated by EUROCONTROL to assess ANSP and Airspace users costs and benefits using the EMOSIA (European Model for Strategic ATM Investment Analysis) approach.
Main validation results
Objective 1: ATC trajectory prediction (TP) accuracy improvement
The analysis of ground TP altitude & time errors dataset showed that using AOC mass and speed information together minimizes altitude errors during the climb phase. The most frequent altitude error rate value (histogram peaks) reduced from about 350 ft/min in baseline scenario to about 100 ft/min in “AOC mass & speed” scenario.
It has been validated that AOC data usage can be added in a current/near-term TP algorithm (iFACTS) with small development effort, and provides improved ground trajectory prediction.
Objective 2: Operational benefits: Safety & Efficiency
Modelling work provided a comparison of false and missed conflict alerts rates at ECAC level (e.g. baseline vs. AOC data scenarios false conflict alert rates for cruise/climb conflicts.).
Both, missed and false conflicts alert rates due to TP errors reduced thanks to AOC data usage in TP calculations. These improvements were maximum (about a 10% reduction) for conflicts involving climbing aircraft using both mass and speed AOC data.
If only one AOC data item shall be used, mass provides the maximum benefit, also during the climb phase. Benefits in cruise are of smaller magnitude while benefits in descent were not statistically significant due to a reduced data set sample.
Subjective assessment validated that controllers preferred the MTCD output when iFACTS was connected to the "AOC" ground TP.
Objective 3: ANSP and Airspace Users Costs/Benefits Analysis (CBA)
The following two benefits for ANSPs have been acknowledged by the CBA working group:
- Safety benefit due to a reduction in the number of missed conflicts,
- Controller workload reduction thanks to the reduction of nuisance alerts.
Cost for software development was estimated at 1 FTE per industry ground supplier plus ANSPs who develop their own ground system. Other costs such as software maintenance or training were considered to be small enough to be covered by current planned budgets.
The communications costs are linked to the assumption that AOC data might be provided through point-to-point communications between FOC and ATC, rather than ATFN, or SWIM. This has been assumed to allow for early implementation.
Benefits for the airspace users have been assessed in terms of fuel economy linked to increased continuous climbs.
At ECAC scale, assuming 100% flights are sharing AOC data, airspace users net present value (benefit) is about 5 Millions € and benefit-to-cost ratio is estimated between 3.5 and 10. The probability that this project would lose money is only 10%.
It should be noted that more benefits can be expected (e.g. descent phase and arrival management, flow management) and that infrastructure costs could in principle be shared with other projects.
Most significant improvements were observed on trajectory predictions in climbing phase. Sharing AOC data should allow more continuous climb (Airspace user fuel economy) and fewer false and missed conflicts alerts (safety benefit).
Moreover, a high participation rate is not mandatory to obtain significant benefits. A 10% participation would be sufficient to balance costs and benefits.
Given the low cost of the project with a benefit-to-cost ratio significantly greater than 1, SESAR P5.5.2 recommends deployment in busy airspaces where the need for improved conflict alert rates is higher.
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