Overview of NLR Free Flight Project 1997 -1999

Overview of NLR Free Flight Project 1997 -1999

Hoekstra, J.M.
Ruigrok, R.
van Gent, R.N.W.H.
Visser, J.
Gijsbers, B.

National Aerospace Laboratory NLR

2000-05-31

NLR has investigated the feasibility of Free Flight concepts with airbome separation during several years of research in collaboration with NASA, the FAA and the RLD (Dutch Civil Aviation Authorities). Issues that have been addressed are: • conflict detection & resolution methods • complex conflict geometries • pilot workload • pilot acceptability • display symbology • safety (both objective & subjective) • mixed equippage procedures • transition issues These issues have been investigated using different techniques, tools and simulations. Off-line traffic simulations comprising up to 400 aircraft simultaneously were used to validate several methods for conflict detection and resolution. This simulated traffic densities up to ten times today's average Western European density. The resolution method that proved to be most effective was based on a publication of Martin Eby of Lincoln Laboratories(MlT). Additionally, complex geometries and restrictions were used to test the robustness of the method. This method has been developed further into an Airbome Separation Assurance System. This ASAS includes a humanmachine interface that has been tested in several flight simulator trials. Air line pilots have been exposed to three times the Western European density and nine time the number of conflicts. No significant increases in workload were found during the cruise phase. The subjects' acceptability proved high and the subjective safety was rated equal or better when compared to today's situation. Further analysis indicated that using this co-operative airbome separation method decreases the collision risk significantly. All studies in the project made use of a resolution method based on exchanging position and velocity information only. No flight plan information, co-ordination procedures, priority mles or groimd based systems proved to be required in order to allow effective separation assurance in the scenarios that were tested. An extra conflict prevention system called predictive ASAS has been developed, which could alleviate a possible need for exchanging flight plan information in the cmise phase. Retrofitting aircraft with such a system is facilitated by the limited requirements for system integration. Because of the simplicity of the architecture and the resolution method, the system proved to be transparant to the crew, allowing a straightforward display design. The traffic display, which is integrated in the navigation display, depicts a horizontal and vertical resolution advisory to the pilot to choose from. Bands on the heading, vertical speed and speed scale show which maneuvers would cause a possible conflict alert. This report describes mainly the airbome perspective. Initial experiments with air traffic controllers in the loop indicated that controllers could collaborate with such a system in order to gain full gate-to-gate coverage. This aspect is described in separate publications. None of the studies could refute the feasibility of airbome separation using such a concept in the cmise phase, even under extremely dense and constrained traffic situations. More detailed information can also be found at the NLR Free Flight Web Site: http://www.nlr.nl/public/hostedsites/freeflight

http://resolver.tudelft.nl/uuid:f225898c-7e23-430f-a37e-9b159bc537eb

Nationaal Lucht- en Ruimtevaartlaboratorium

Campus only

NLR Technical Publication TP 2000-227

Aerospace Engineering Reports

report

(c)2000 National Aerospace Laboratory NLR