This concept also known as Trajectory Based Operations (TBO) will provide the capabilities, decision-support tools, and automation to manage aircraft movement by trajectory. It will enable aircraft to fly negotiated flight paths necessary for full Performance Based Navigation (PBN), taking both operator preferences and optimal airspace system performance into consideration. TBO is a cornerstone of NextGen and SESAR; it is a major operational transformation for aviation, basing safe separation on much higher levels of automation that assesses the current aircraft positions, with respect to their future positions in time. TBO is a 2025 air traffic management system concept that manages aircraft through their Four-Dimensional Trajectory (4DT), gate to gate, both strategically and tactically to control surface and airborne operations. A 4DT includes a series of points from departure to arrival representing the aircraft’s path in four dimensions: lateral (latitude and longitude), vertical (altitude), and time. 4DTs will be used for planning, sequencing, spacing, and separation based on the aircrafts’ current and future positions. Separation duties will be performed by a combination of airborne and Ground Based Automation (GBA).
Historical perspective: On clearance-based ATC… and the drivers/enablers for TBO.
These functions integrate the traditional functions of navigation (defining a path and creating path guidance) and flight control (steering the aircraft to that path). It adds additional capabilities for NextGen, including conformance monitoring, trajectory negotiation (a traditional “communication” function), and some functions to support trajectory planning (weather data, traffic data, fuel optimization, etc). Strategic trajectory planning, or trajectory optimization (to optimize time or fuel within a given set of constraints such as aircraft performance and weather), may take place within the aircraft trajectory management function or may be accomplished in a ground system and the result communicated to the aircraft. A common operational concept of use for mid-term Tops is in development through RTCA, and a parallel activity in JPDo is defining the long-term Tops capabilities.
- Synchronous garble and False Replies Unsynchronized In Time preventing CPDLC messages from getting through.
- ADS-B ground system failure; ground based automation does not receive ADS-B message
- Inaccurate modeling of wake location and strength (drift, sink, persistence, severity)
- Ground based conflict resolution not calculated. With increasing levels of traffic, TCAS may not provide a robust defense.
- Safety critical input data are incorrect, late or missing
- Software processes are too slow to reliably fulfill the automation requirements
- Breakout maneuvers, go-arounds, or missed approaches are not conflict free
- Controller misunderstands what the automation is doing with other aircraft in his/her sector
- Excessive controller workload due to TBO complexity
- Excessive controller workload due to TBO automation failure
- Pilot distractions: pilot makes mistakes when performing TBO navigation due to distractions from TBO related distractions (conformance alerts, etc.) in cockpit. This distraction may become more likely, when the instruction requires the pilot to involve ‘knowledge based behavior’ (Rasmussen, 1983). This follows from very recent NLR research into improved angle of attack indications, where a ‘Rule Based Isomorphic’ display had the best results during stressful situations.
- Pilot performs traffic avoidance maneuver to clear aircraft not accounted for in the current 4D trajectory
- Pilot performs weather avoidance maneuver not accounted for in the current 4D trajectory
- Pilot decision making when presented with weather information may not be uniform.
- Aircraft emergency situations (off-nominal); aircraft has an emergency and must deviate from 4D trajectory
- Missed approach under TOB; unanticipated change to the 4D trajectory by the aircraft
- Received information from GPS incorrect or missing
- Unmanned Aircraft loses control link and is not visible to ground based automation/ANSP, Unmanned Aircraft is executing the predetermined flight plan from the point it lost link.
- Control link failure between UAS and ground station; equipment failure; intentional takeover
- Unauthorized aircraft or vehicle traffic; aircraft or vehicles not equipped with transponder or ADS-B