Ramon Lopez/WASHINGTON DC
The future of the US Federal Aviation Administration's work on the next-generation traffic-alert and collision- avoidance system (TCAS) hangs in the balance as agency officials prepare to present FAA administrator David Hinson with their findings on research into the TCAS 4.
Terminating the Congressionally mandated research work on the TCAS 4 in favour of additional TCAS 2 enhancements is among options which will be offered to Hinson.
Research shows that the TCAS 4 would only provide a marginal increase in safety, and FAA officials believe that tight research and development funding may be better spent in continuing to evolve the TCAS 2.
Passenger aircraft with more than 30 seats being operated in the USA must have the TCAS 2, which offers traffic advisories (TAs - a display/audio-alert system informing pilots of the relative positions of nearby aircraft) and resolution advisories (RAs - recommended climb-or-descend avoidance manoeuvres). The TCAS 4 would provide RAs in the horizontal, as well as the vertical plane.
The TCAS 2 with "Version 7" software will undergo flight testing early in 1997. The FAA estimates this, together with an earlier software update, will reduce the number of false RAs by nearly 75%. It is this promise which leads FAA officials to believe that the TCAS 4 may not be cost-beneficial.
A TCAS 4 flight demonstration was expected in late 1997 or early 1998, and certification has been projected for 1999-2000.
The FAA is rethinking the issue, however, because TCAS 4 research to date shows that "horizontal manoeuvre is only effective roughly 10-15% of the time in resolving a near mid-air collision," says Thomas Williamson, the FAA's TCAS programme manager.
As a result, Williamson says that the FAA is evaluating its future course of action over TCAS. He says that the new system may be unnecessary. "TCAS 2 has increased the level of safety for travellers well beyond our expectations. It is more than adequate in resolving a mid-air collision."
Another option would be to make the TCAS 4 a component of the FAA's "free-flight" concept. This would evolve air-traffic-management from today's rigid, largely-procedural ground-based system to a flexible, collaborative system utilising current and emerging technologies.
Source: Flight International
