NASA began flight-testing the first “spiral” prototype radio from Rockwell Collins in late May on the NASA S-3 at the Glenn Research Center in Cleveland, accumulating 20 hr. of operating time on the first-generation radio communicating with a single ground station. The spiral one radio operates in the L-band only, but a follow-on test in Iowa on June 18 provided 4.5 hr. of flight time as a risk-reduction measure for the added C-band capability for the “second spiral” radio, due to be completed in September, with flight tests finished in March 2014.
The second spiral testing will include handoffs between two ground stations using the S-3. The third and final spiral radio is slated to be completed in 2015, followed by flight-testing that will include data-link security, multiple ground stations and multiple aircraft, using a UAV surrogate controlled by a pilot on the ground but also with a safety pilot on board.
During the first spiral flight tests, Griner says the S-3 flew at several different speeds and altitudes up to 10,000 ft., measuring the waveform at the edge of coverage area and how it degrades as the signal strength is reduced.
Moore says the use of L-band versus C-band will be a “big part” of the work in front of the RTCA committee, but one option might be using both spectrums simultaneously for a hot backup, in case one fails.
Noting the critical importance of the data link, Moore adds “The bar will be higher” for the safety and security attributes that will be required of the final product.