Unmanned Aircraft Systems (UAS) Integration in the National Airspace System (NAS) Project: ACAS Xu HITL Overview

This presentation provides an overview of a recently completed human-in-the-loop simulation, conducted as part of the Unmanned Aircraft Systems (UAS) Integration in the National Airspace System (NAS) Project. This study examined how to present resolution advisories (RAs) issued by Airborne Collision Avoidance System (ACAS) Xu, which can be in the vertical dimension, the horizontal dimension, or both (i.e., "blended"). The study varied the location of the ACAS Xu traffic information - it was either presented within an 'integrated' display or a 'standalone' display, where the traffic information was separated from the vehicle control interfaces and navigational information. The presentation covers the test set-up, scenario design, and facilities utilized in this experiment. The primary dependent variables are listed, but no detailed results are included in this outbrief since data analysis is still underway.

Goal: assess ACAS Xu Run 5 in a HITL setting to measure pilot &
system performance
– RWC alerting and guidance
– RA alerting and guidance
• Horizontal-only, vertical-only, and blended RAs
• Strengthening RAs, reversals and added/removed RAs during blended
maneuvers
– Incorporate realistic sensor noise into the simulation environment
– Compare pilot and DAA system performance back to NASA’s Phase 1
DAA MOPS V&V HITL
• We leveraged the findings of an engineering analysis
conducted in March to help inform how to implement the Xu
logic
– Part 1 focused on how to display horizontal-only, vertical-only and
blended RAs
– Part 2 focused on how to display automated RA responses Xu Engineering Analysis Results Part 1 objectives:
– Characterize pilot responses to (canned) ACAS Xu RAs in a variety of
display configurations
• With vs. Without text accompaniment
• Simple vs. ‘Advanced’ aural alerting
• Results
– Pilots struggled to meet 5 seconds initial response requirement
• Particularly against horizontal and blended RAs
– Pilots failed to respond more quickly to secondary RAs
• Expected response time to subsequent RAs = 2.5 seconds No clear effect of the different alerting conditions on response
times
– Response times primarily driven by RA type
• Pilots demonstrated high level of compliance with RAs and
self-reported Xu alerting and guidance as being acceptable
– 1/5 reported text as being necessary
– 4/5 wanted the aural alert to retain the original RA sequence (i.e., issue
a follow-on RA second rather than first)
– 4/5 wanted to retain the “Maintain Heading/Vertical Speed” aural alert
in the event that the pilot reached their target response at the time of
secondary RA Based on these results, we decided on the following for the
HITL experimental design:
– Incorporated an ‘auto-fill’ feature in Vigilant Spirit that removes the
need for pilots to manually enter a heading or altitude for RAs
• Pilots only have to click ‘Send’ to upload the RA target heading/altitude
– Did not include an RA ‘text box’
• The auto-fill feature largely replaces the purpose of the text box
– Using a combination of the ‘Basic’ and ‘Advanced’ aural alerting
• In case of blended maneuvers will issue “Maintain Heading/Vertical Rate” if
pilot has reached 1st RA target at the time the 2nd RA is issued
• Integration and testing with Xu Run 5 also resulted in us adding
display logic to modify how horizontal RAs are presented
– Target heading was shown to update at approx. 1 Hz making it difficult
for pilots to implement
– Display logic limited horizontal RA strengthening to once every 5
seconds
• Did not impact timing of reversals, new RAs (i.e., blended), or CoC Engineering Analysis Results