During 1917 “Signaling to aeroplanes did not occupy nearly as prominent place as in the Somme Offensive. The methods employed were again the ground sheet, the ground panel and the aeroplane dropping ground. The panel was cumbersome and slow and still unpopular; the latter was the most popular method and the most efficient. By this means valuable information was brought back by the aeroplane observers and a series of precis of the situation delivered regularly to the General Staff at Division and Corps. Signaling to kite balloons and aeroplanes by visual was again tried without success. Visual, generally, was much employed, but all other methods paled to insignificance beside the efficiency of the Lucas lamp. Flags were little used, discs were used only by very forward units, and by these less than in 1916, other types of lamps other than the Lucas were practically obsolescent, and were superseded as fast as the Lucas lamp came to hand. Very lights and rocket were laid down as part of the equipment of the normal Brigade forward party and were especially useful for the purpose of notifying sudden emergencies and for showing up the position of the front line and of particular posts. They were used also, as in the previous year, for acknowledging the receipt of D.D.D.D. visual messages.“ P220-221, Work of the RE in the European War, 1914-1919: The Signal Service (France)