A distributed control system comprising an active array antenna system with at least one set of many transmit/receive, T/R, modules , each T/R module comprising a radiator element arranged in an array or subarray, a phase shifter element and a set of RF switch elements to set the T/R module to transmit or receive modes, the antenna system arranged to generate a transmit or receive array beam, the control system further comprising: a processor for controlling the at least one set of T/R modules , the processor configured to propagate command signals to set the T/R module elements to transmit or receive mode and to steer the array beam to a desired direction, and wherein the command signals to steer the array beam include phase slope data common to all T/R modules in said set; a beam steering control function implemented in each T/R module, configured to convert said phase slope data to phase data to set the phase shifter element associated with each respective T/R module to a phase shift setting for the beam direction associated with said phase slope data; and wherein the at least one set of T/R modules are arranged in a plurality of rows, and a first T/R module in each row is a master T/R module (440-1A) and the remaining T/R modules in each row are slave T/R modules (440-1B), wherein the master T/R module (440-1A) for each row receives the command signals from the processor and propagates the command signals on a bus to corresponding slave T/R modules (440-1B) in the row; wherein the plurality of rows are arranged as sets of even and odd rows, and wherein the master T/R module for each even row also propagates the command signals to slave T/R modules in a corresponding odd row on said bus; wherein the master T/R module for each odd row is normally disabled from propagating the command signals to the slave T/R modules connected on said bus, and includes logic circuitry to determine an error condition in which the command signals from the processor do not match the signals propagated from the corresponding even row master T/R module, and activates to propagate the command signals to the slave T/R modules on said bus in the odd row and in the corresponding even row. a processor for controlling the at least one set of T/R modules , the processor configured to propagate command signals to set the T/R module elements to transmit or receive mode and to steer the array beam to a desired direction, and wherein the command signals to steer the array beam include phase slope data common to all T/R modules in said set; a beam steering control function implemented in each T/R module, configured to convert said phase slope data to phase data to set the phase shifter element associated with each respective T/R module to a phase shift setting for the beam direction associated with said phase slope data; and wherein the at least one set of T/R modules are arranged in a plurality of rows, and a first T/R module in each row is a master T/R module (440-1A) and the remaining T/R modules in each row are slave T/R modules (440-1B), wherein the master T/R module (440-1A) for each row receives the command signals from the processor and propagates the command signals on a bus to corresponding slave T/R modules (440-1B) in the row; wherein the plurality of rows are arranged as sets of even and odd rows, and wherein the master T/R module for each even row also propagates the command signals to slave T/R modules in a corresponding odd row on said bus; wherein the master T/R module for each odd row is normally disabled from propagating the command signals to the slave T/R modules connected on said bus, and includes logic circuitry to determine an error condition in which the command signals from the processor do not match the signals propagated from the corresponding even row master T/R module, and activates to propagate the command signals to the slave T/R modules on said bus in the odd row and in the corresponding even row. <EOS>