This Attachment is based on the experience of redeployment at the regional level for the aeronautical mobile.

Communications for air-traffic control use the aeronautical mobile (R) between 117.975-137 MHz. The number of available VHF assignments was increased by optimizing frequency reuse (improved coordination and possibly confining VHF assignments to smaller areas), using more spectrum (118 to 132 MHz increased to 117.975-137 MHz), and splitting the radio spectrum into narrower bandwidths. This example shows the challenges associated with redeployment on a regional basis.

In 1947, VHF assignments for aeronautical mobile (R) in 118-132 MHz used 200 kHz spacing, providing just 70 channels. In 1958, the spacing was reduced to 100 kHz, doubling the number of channels to 140. In 1959 the upper limit of the aviation band was expanded to 136 MHz, giving another 40 channels, bringing the total to 180. In 1964, the channel spacing was halved again to 50 kHz, resulting in 360 channels being available. The channel spacing was further cut to 25 kHz in 1972, doubling the available channels to 720. Seven years later, in 1979, the upper limit of the aviation band was once again expanded to 137 MHz, bringing the total number of channels to 760.

In 1995, the proposal was made to reduce the channel spacing to 8.33 kHz, resulting in 2 280 channels. With each iteration of the improvements in number of channels by reducing the channel size, a much higher number of radios required replacement and the time-scales for the implementation also increased.

Following consultations with the stakeholders concerned, the European Commission, in January 2006, decided to address the scope of the mandate in two phases. The first phase, aimed at the deployment of 8.33 kHz channel spacing in the airspace above flight level 195 (FL195), was completed with the adoption and publication of Commission Regulation (EC) No. 1265/2007, with below FL195 (Second Phase) to be managed through a later amendment. Eurocontrol has published a Close-Out report (http://www.eurocontrol.int/vhf833/public/standard_page/above_fl195.html) detailing to what extent the original planning and assumptions have been satisfied by the actual execution of the above FL195 phase. The report discusses the lessons learned, with equal emphasis given to successes and failures.