Simulations are increasingly requested by en route and
approach control facilities in order to test and validate
new air traffic concepts. The development of new
concepts such as free-route and ASAS-spacing necessarily
include experimental phases on a simulator before they are put
into operation.

The OPAS fast-time simulators developed by Egis Avia
for DSNA, the French ANSP, overcome
limitations of previous simulators. The OPAS family has three simulators: OPASEn-
route and OPAS-TMA are specialised in en route
and approach traffic, and OPAS-Ground covers stands,
apron, taxiway, runway operations In addition OPAS-Coupled
unites the first two in one simulator that is capable of managing
traffic from the runway as far as en route and the reverse

Two tools complete this family: OPAS ESPRIT, an input
interface for approach area procedures (for OPAS-TMA), and
OPAS-ARTS, a tool for dynamic trajectory display. REGARDS, an independent tool for displaying aeronautical
data, enables the results of studies to be enhanced by
using coloured maps, among other things.

The strong points of the OPAS family are the realism of the
simulations and the flexibility of the code. The performance
model used and the flight management algorithms are key
factors in the level of precision reached by the simulators, and
particularly by OPAS-TMA.

Faithful reproduction of radar guidance and traffic flow in the approach area

OPAS-TMA is, as far as we know, the only simulator that can
faithfully reproduce the radar guidance and hence the flow of
traffic in the approach area. The realism of trajectories is also the
key input to realistic environmental studies, particularly noise
and air quality.