The CAA has introduced some realism to the proposed introduction of Mode S

The CAA appears to be moving away from a blanket introduction of Mode S next year to a phased approach which might not include all classes of aircraft for a number of years, particularly those which have little or no battery availability to power a transponder.It is envisaged that a first phase could be theintroduction of Mode S as the means of compliance in airspace wherethe carriage of transponders is already mandated, and subsequent phases couldthen expand the airspace in which the carriage and operation of transpondersis mandatory to include Class D and mandatory carriage zones. The CAA says this would specifically address identified safety concerns. Furtherproposals, says the authority, would consider the impact of airspace utilisation and userrequirements on interoperability requirements and transpondercarriage regulation.The CAA adds that until suitable Low Power SSR Transponder (LPST) products are available at a reasonable price, ‘any applicability criteria and transitional arrangements would take into account the operational, technical and financial barriers that would preclude certain aircraft from carrying and operating an SSR transponder. Aircraft will not be grounded in 2008, or beyond, if suitable LPST units cannot be brought to market.’