Accounts of the Battle of Ushant describe the destroyers keeping their spacing by radar. An older directional display could monitor the enemy ahead or a neighboring ship to the side, but could not readily do both. PPI offers an explanation for the reported behavior. A motor could have moved the radar through a 180- or 270-degree arc without a complete rotation. A blind area astern would also fit occasions when ships lost an enemy directly behind them. This is the reasoning for a firm belief in significant crew modifications, although the proposed mechanism remains an inference.
Notable Point · 2:12:03-2:13:40
Why a limited radar sweep could support line-abreast tactics
Simultaneous forward searching and lateral station keeping support the inference that older destroyer radars had been adapted for PPI displays.