issues with pbn implementation and trajectory prediction in atc … · 2012-10-24 · issues with...
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Issues with PBN Implementation and Trajectory Prediction in ATC Operations
Hassan Shahidi MITRE - USA
Center for Advanced Aviation System Development (CAASD)
Director, Aviation Safety
Issue: Different Implementations of Standards Lead to Path Performance Variations
Due to Flight Management System (FMS) differences, planned and as flown paths vary, resulting in less predictability for controllers
Issue: FMS Performance Differences Flyby Waypoints, Speed Constraints and Wide Turns
• Turns at flyby waypoints – Turn anticipation differences varies
• Speed constraints at waypoints – Some FMSs require an altitude at a
speed constraint; some don’t
• Turns above FL195
– Some aircraft perform wider turns for shorter path length (fuel savings) resulting in bank angles of 5-15 degrees
Issue: FMS Performance Differences Lateral Offsets, Runway Transitions
• Lateral Offset – FMS’s perform Lateral Offset differently
• Some FMS’s may start and end a lateral offset at a waypoint and some cannot
• Runway transitions – Not all FMS’s automatically process
(non tailored) runway transitions • Limiting leg types off the runway
– Heading to Altitude (VA) vs. Heading to Intercept (VI)
– Direct to Fix (DF) vs. Course to Fix (CF)
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Under busy conditions, controllers take airplanes off the PBN procedure and the full benefits are not realized
Project title (Insert, Header & Footer)
Example: Path Prediction
KEPEC
Lateral path prediction impacted most fly-by turn variation
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Example: RF Legs Improve Trajectory Predictions
OAK arrivals (mixed) OAK arrivals (RNP AR)
KEPEC
0 0.5 1 1.5 2 2.50
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Point of Closest Approach (NM)
Flig
ht C
ount
Smal
l Rad
ius
Larg
e Ra
dius
The point of closest approach is defined as the distance from the fix to the point where the flight bisects the turn
Example: RF Legs Reduce Variability
• Unconstrained FMS planned descents lead to unpredictability and variability in vertical profiles
Example: FMS Vertical Profile
Potential mitigation – Applying constraints with possible impact to fuel burn and emissions.
Controllers find it difficult to manage CDAs through departure flows and other crossing traffic
The Way Forward Lessons Learned
• Incorporate new understanding of FMS performance into: – Procedure design tools – Improved standards &
criteria – Leverage Automation Aids – Best practices given current
fleet mix – Training (pilots/controllers)
Near Term Future • Improve FMS standardization
– RTCA SC 227 and EUROCAE Working Group 85
– Performance-Based Operations Aviation Rulemaking Committee (PARC)
– Flight Deck Automation Working Group
– CNS Task Force