3rd ALIAS Conference Presentation 5-6 October

2. Application of legal case
to ACAS XA

3. Background in ACAS X
• Worked on TCAS II for 28 years
– SARPs for ACAS II
• Chairman of EUROCAE WG-75
• Currently under contract to the FAA
– developing ACAS XA and ACAS XU

4. User Group Experience
• Joined at quite a late stage
• Fascinating but not reassuring
– Undermined my confidence in legal process
– No longer trust it to reach sensible decisions

5. Results from test application
• For whom? Methodology or ACAS X?
• w.r.t. methodology, it demonstrated that
the process can indeed be applied to ACAS
– Determines the exposure of each actor to the
risk of being found liable for an accident
– but it does not evaluate the probability of the
accident, nor of the case being brought
– nor does it seek to determine who is liable

6. Use in Concept of Operations
• Already reported: ACAS XA =TCAS II
• There no possibility of use in ACAS X ConOps
• But that would be the best place to use
anything that can be used

7. Use in design of ACAS XA
• I agree it is essential to define procedures
– Saying procedures must be defined does not help
• We know it
• Deep prejudice in favour of providing information
• There are other systems that just show tracks
– Track and TA will aid visual acquisition
• In the USA pilots are expected to rely on visual evidence,
in Europe EASA warns against that

8. Use in design of ACAS XA
• So – give them an RA
– Again, I happen to agree
– Not going to happen because endangers timescale
– Significant work involved
– Comments about maturity and encryption misplaced
• The technology is mature
• We want ADS-B to be open – that is the point of it
• Design of ADS-B not under control of ACAS X team

9. Final comments
• The application of well-meaning disciplines is
not always beneficial
– “The road to Hell is paved with good intentions”
• Already required to be safe and effective
• The only use I can see for the Legal Case is to
help transfer the risk between actors
– to avoid litigation by ensuring that those against
whom there is a credible case cannot pay