The US government must conduct an in-depth risk assessment of the planned satellite-based air-navigation system before it dismantles the current ground-based radio- navigation system, a White House report has warned.

The President's Commission on Critical Infrastructure Protection says that the use of the global-positioning system (GPS) as the sole source of navigation carries risk. Over the next 15 years, the US Federal Aviation Administration will move in three phases to satellite-based navigation throughout the national airspace system (NAS).

Of the threats facing the USA, "-the most significant projected vulnerabilities are those associated with the modernisation of the NAS and the plan to adopt the GPS as the sole basis for radio navigation in the USA by 2010," says the report.

It notes that total reliance on the GPS for landing aircraft "creates the potential for single-point failure and cascading effects". Furthermore, future systems for air-to-ground communications - such as the automatic dependent surveillance-broadcast (ADS-B) mode - are considered susceptible to interference and signal jamming.

Echoing criticism from GPS opponents, the report concludes that "-exclusive reliance on any single system creates inherent vulnerabilities; no single system can be guaranteed for 100% availability for 100% of the time".

The advisory group recommends that the US transportation secretary fully evaluate actual and potential sources of interference to, and vulnerabilities of, the GPS before a final decision is reached to eliminate all other radio-navigation and aircraft-landing systems.

"A federally sponsored thorough, integrated, risk assessment would lay a sound foundation for decisions on future courses of action," the report concludes.

Source: Flight International