By 1917, the Aldis gun sight, developed by the Aldis brothers in Sparkhill, Birmingham in 1915, had become the main gun sight in British scout (fighter) aircraft. Looking like a telescope, it was 32 inches long and had a diameter of 2 inches. The tube of the gun sight contained a series of lenses marked with two concentric rings, hermetically sealed to contain an inert gas to prevent the lens from fogging.
However, while the collimated tube of the Aldis sight was ideal for scouts making a diving hit-and-run attack, it was found to be less useful in close dog-fights. Captain ‘Mick’ Mannock’s ‘A’ Flight on No 74 Squadron favoured the close engagements and finding the Aldis sight not to their liking, replaced them with the standard Vickers machine gun sight mounted on the centreline of the fuselage of their SE 5a fighters. Mannock’s argument was that in close-in dog-fights the pilot’s eyes need be looking outside the cockpit and not looking down the telescopic Aldis gun sight.
AN EXAMPLE OF AN ALDIS GUN SIGHT IS MOUNTED ON THE MUSEUM’S SE 5a REPLICA COCKPIT IN THE MERSTON HALL