A government/industry "tiger team" has concluded that aircraft separation standards will have to be reduced significantly if investment in the US Federal Aviation Administration's automatic dependent surveillance - broadcast (ADS-B) system is to be worth the money.

Speaking at the FAA's Flight Standards Service New Technologies Workshop in Washington last week, Ken Speir, head of a government/industry ADS-B advisory committee, said an avionics tiger team within his group determined that future aircraft-to-aircraft separation standards will have to be decreased to as small as 0.1 RNP - about 1,200ft (365m) in the terminal environment - for airlines to make an economic case to retool their entire fleets with the new radios. In-trail separation in the terminal area for instrument approaches is generally 3nm (5.5km) while en-route space is 5nm with today's radar surveillance systems.

While in-trail distances will probably be greater than 1,200ft due to technical or physical concerns, such as wake turbulence, the ability to fly lateral offsets as close as 1,200ft could allow airports to build new parallel runways between existing parallel runways, substantially boosting capacity with simultaneous instrument arrivals on all runways, says Speir. Currently, runways must be at least 4,300ft apart (laterally) for aircraft to fly independent instrument approaches.

The findings come as the FAA prepares to release a request for proposal in March for companies to operate the ADS-B system, to be followed by a contract award by July. The agency plans a notice of proposed rulemaking covering mandatory ADS-B equipage for certain airspace in September, and hopes to finalise the rule by 2010. Initial implementation would most likely be in the Gulf of Mexico.

The FAA has made ADS-B, combined with GPS navigation, the backbone of its national airspace modernisation plan, in part to reduce the costs of maintaining its terrestrial network of 450 radar systems, half of which the agency intends to phase out from 2020.

Source: Flight International