April 8, 2015

After Dec. 31, 2017, all aircraft radios operated in Europe must be 8.33 kHz-capable, but for most business aircraft operators “it’s a non-event,” said John Tuten, chief pilot of Honeywell Flight Operations, and one of the European regional leads for the NBAA’s International Operations Committee.

“Most business aircraft coming from abroad are already 8.33-equipped and ready for the frequency expansion, added European co-lead Chris Duffek, who flies for JPMorgan Chase’s aviation department. Even though the United States still uses 25 kHz spacing, most aircraft radios sold in the past couple of decades have incorporated an 8.33 option.

Europe is the only region to adopt 8.33 channel spacing, which expands the potential available channels nearly fourfold to 2,280 (compared to 760 at 25 kHz) in the VHF “airband” between 118 and 137 MHz. Without the extra channels, the region would be about 30 percent short of future frequency requirements.

Currently, 8.33 channel spacing is required in Europe above FL195. Also, aircraft may not fly IFR in Class A, B or C airspace unless 8.33-capable. Since November 2013, manufacturers have not been allowed to market radios that are not 8.33-capable, and any upgrades to aircraft radios require 8.33 kHz capability.

“Some pilots leave their radio on 8.33 spacing all the time,” Tuten said. “Others switch it back to 25 kHz when flying in U.S. airspace.”

The original channel spacing for voice communications was 200 kHz until 1947, when it was halved to 100 kHz. It split again in 1954 to 50 kHz when the upper limit was extended from 132 to 136 MHz, and then to 25 kHz in 1972. Frequencies from 136 to 137 MHz were added in 1990.

Europe first introduced 8.33 standards (above FL245) in 1999.