The CAA has just announced its revised proposals for Mode S

The CAA is now proposing the following implementation phases for Mode S as detailed below: Phase One The existing requirements for aircraft to carry and operate a transponder would remain unchanged.  However, with effect from 31 March 2008 the technical means of compliance would be SSR Mode S instead of the ageing Mode A/C technology.To gain access to the current mandatory carriage airspace, all aircraft will need to be upgraded to Mode S from this date.  However, there will be a four year transition period from 31 March 2008 during which upgrades of existing transponders can be completed.  All new installations of SSR equipment, or where new aircraft are being brought into service with an SSR transponder already installed, will have to be Mode S compliant after 31 March 2008.  No further public consultation on this phase will take place.Phase Two The CAA intends to conduct further public consultation on its policy aim to expand the requirement to carry and operate SSR transponders.  This consultation will seek views on the following proposals: For all VFR flights conducted within controlled airspace to be equipped with SSR Mode S transponders. On a regulatory framework for the establishment of notified ‘Transponder Mandatory Zones’ (TMZs) within specific portions of uncontrolled airspace. The intention of TMZs would be to mitigate specific risks but with the minimum impact on uncontrolled airspace. For all international flights conducted by powered aircraft to operate with SSR Mode S The removal from the Air Navigation Order of the exemption for gliders from transponder carriage requirements. With the exception of TMZs, operations in Class G airspace below Flight Level 100 would be unaffected by Phase Two, and the use of Letters of Agreement (LOA) and airspace reservations would continue to be available in specific circumstances.  The proposed implementation date for this phase will be 31 March 2009, with a three year transition period to provide time for operators to install the necessary SSR Mode S capability.John Arscott, Director of Airspace Policy, said:  “A strategy to safely increase interoperability over time represents the best way to meet the future demands of all airspace users.  The increased carriage of Mode S transponders is a significant step towards airspace safety and meeting this objective.”Future Implementation Phases It is envisaged that the phased implementation will proceed beyond Phase Two with the aim of expanding SSR transponder carriage throughout all UK airspace and, where technically feasible, to all aircraft as user demand and airspace arrangements require.  However, depending on the timescales, the means of compliance for these additional phases will need to take into account new technologies and the need to be consistent with emerging European policy. Additional phases would also be subject to further separate consultation.Funding The CAA is investigating funding opportunities to support its policy proposals. These include encouraging an industry partnership for the development of a Low Power SSR Transponder (LPST). It is also investigating funding to offset institutional costs, such as certification, which could potentially benefit all affected operators.Further consultation A Full Regulatory Impact Assessment (RIA) and proposed amendments to the Air Navigation Order for Phase One will be submitted to Government for consideration by Autumn 2007.  It is expected that the public consultation on the proposals for Phase Two will start towards the end of 2007 and will take place over 16 weeks