The critical "free-flight" evaluation in Hawaii and Alaska, planned for 1999-2000, will serve as the precursor for implementation of the USA's future air-traffic-management (ATM) system. The brain-child of George Donohue, the US Federal Aviation Administration's associate administrator for research and acquisition, the so-called Ha-laska Project was given added importance when the White House Commission on Aviation Safety and Security urged implementation of the National Airspace System (NAS) plan for 2005, seven years sooner than planned.
The ATM is a key element of the NAS plan, and US Vice-President Al Gore, who headed he Commission, believes that the Ha-laska demonstration "… is an important step towards full operational status" of the nation's satellite-based air-navigation system.
Free flight is an ATM system which allows pilots and airlines to set their own flightpaths. Under the system, air-traffic controllers would intervene only to prevent accidents. It would enable the ATM to evolve, from today's rigid, largely procedural, analogue and ground-based system, to a flexible, collaborative system using current and emerging technologies such as the global-positioning-system navigation satellites, two-ways datalinks, satellite-based navigation, the automated dependent surveillance-broadcast (ADS-B) system, and airborne collision-avoidance systems. New displays, in aircraft and at air-traffic-control stations, will be required for accurate, real-time, situational awareness.
PILOT IN CONTROL
It is the pilot, not the controller, who, under the free-flight concept, would choose the route, speed and altitude. The concept is based on two airspace zones: protected and alert. In principle, until the alert zone is breached, aircraft can be manoeuvred with autonomous freedom.
The two-year demonstration will involve all categories of commercial-transport aircraft and some military aircraft. General-aviation aircraft involvement is voluntary. The FAA will pay for necessary equipment, and 2,000-2,200 aircraft in both states will be involved. Hawaii and Alaska were chosen because of their controlled environment and affordable fleet size.
Donohue says that it is imperative to conduct the free-flight test on schedule. Only 10% of the 200,000 US-registered aircraft flying in 1% of US airspace will be involved. "If we can't do this by the year 2000, it will be virtually impossible to do the other 48 states by 2005," concludes the FAA research-and-development chief. "Anything of the magnitude of moving to free flight has got to have a significant demonstration of how it works before it will be accepted by the controller and pilot communities," he adds.
Donohue says that all the avionics needed to make free flight a reality are in place for the Ha-laska project, including the ADS-B. The only thing remaining is to set the frequency and message-format standard for the ADS-B. "This experiment will require us to make some system-level decisions that we have been unable or unwilling to make for a long time," he says.
ADS-B FAVOURED
The FAA has elected to scrap work on a stand-alone, next-generation traffic-alert and collision-avoidance system (TCAS 4), in favour of the ADS-B with cockpit display of traffic information. As envisioned, the TCAS 4 would have given resolution advisories (RAs) in the horizontal, as well as the vertical plane.
He says that the ADS-B is more accurate than the TCAS, will be cheaper to build than the TCAS 1 and the more-capable TCAS 2, which cost $100,000 and $200,000, respectively. He says that only the high-end ADS-B units might incorporate conflict-resolution capabilities. Donohue says that the FAA may not require horizontal RAs.
It is estimated that it will cost over $7 billion to equip US-registered aircraft for free-flight operations. An objective of the Ha-laska evaluation is to find ways to reduce significantly the cost of the avionics installations and of certificating this on-board equipment. Donohue hopes that a low-end free-flight installation will cost no more than $20,000. The high-end system, able to interface with flight-management computers, could cost as much as $100,000.
"We must change the way we develop and certify avionics. There are too few suppliers and too many barriers to entering the marketplace," he says. Donohue expects a Government/industry partnership and wants to qualify four or five vendors, each producing about 500 free-flight avionics sets.
Undetermined funding for the free-flight demonstration will be contained in the fiscal year 1999/2000 budget requests. In addition, "… industry is expected to provide their own nickel.. We have already received offers for fairly significant investments," he adds. Donohue expects to finalise details of the project soon.
He expects US President Bill Clinton's Administration to provide the needed funds. "Within the financial resources of the US Government we can do this experiment. We must find the specific allocations," he adds.
Source: Flight International
