CAA Outlines Mode S Implementation

June 18, 2007 // Published as a news service by IHS

According to CAA, a more gradual expansion than initially planned of the new technology will enhance safety by improving the technical interaction between disparate airspace users without the need for a wholesale expansion of controlled airspace.

CAA came to this conclusion after taking into consideration some 3,000 responses to a 2006 partial regulatory impact assessment and further discussions with representatives of general aviation (GA) associations, National Air Traffic Services (NATS) and the U.K. Ministry of Defence (MOD).

Phase One
While the existing requirements for aircraft to carry and operate a transponder would remain unchanged, beginning on March 31, 2008 the technical means of compliance would be SSR Mode S instead of Mode A/C technology.

To gain access to the current mandatory carriage airspace, all aircraft will need to be upgraded to Mode S as of the March 2008 date. There will, however, be a four-year transition period, 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 March 31, 2008. No further public consultation on this phase will take place.

Phase Two
The CAA intends to conduct further public consultation on its policy to expand the requirement to carry and operate SSR transponders. This consultation will seek views on the following proposals:

• For all visual flight rules (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 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 March, 31 2009, with a three-year transition period to provide time for operators to install the necessary SSR Mode S capability, CAA said.

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 U.K. 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, including 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, CAA said.

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. The public consultation on the proposals for Phase Two are expected to start towards the end of 2007 and will take place over 16 weeks, excluding the Christmas holiday.

The consultation documentation for Phase Two will be produced in conjunction with inputs and support from user group associations. The consultation period will be supported by a number of regional presentations.

CAA will post further details of the development of these policy proposals on the CAA Mode S homepage at http://www.caa.co.uk/modes as they become available. Specific enquiries can be e-mailed to mode.s@dap.caa.co.uk.

Proposed Phase 1 & 2 timetables:

Phase 1

• Autumn 2007 - CAA submission of Phase 1 proposals to government. March 2008 - Proposed implementation date for the Phase 1 proposals.
• March 2012 - End of the proposed transition period for Phase 1.

Phase 2

• Summer 2007 - Informal stakeholder workshops on the Phase 2 proposals.
• End 2007 - Public consultation on the Phase 2 proposals commences for 16 weeks.
• Autumn 2008 - CAA submission of Phase 2 proposals to government.
• March 2009 - Proposed Implementation date for Phase 2 proposals.
• March 2012 - End of the proposed transition period for Phase 2.

Source: U.K. Civil Aviation Authority (CAA).