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Fig. 8. Fokker Synchronized Machine Gun. The Gun Is Driven by the Motor in Such a Way That the Bullets Pass Between the Propeller Blades. "L’Aerophile."

"Spotting" for the guidance of the artillery is a duty usually performed by the reconnaissance type, or small bombing type, and is usually done under the escort of chasers. Their duty is to direct the battery as to the placing of shots. The ideal machine for such a purpose would be the direct lift type similar to a helicopter which could hover over one particular spot until its object had been accomplished in making measurements, and plotting enemy positions. Since no such machine is at present available, the duty must be performed by a low speed aeroplane, that is large enough to provide a fairly steady platform and at the same time has sufficient speed for a quick getaway. A dirigible has the necessary hovering qualities but lacks the speed necessary for avoiding attack from even the slowest of aeroplanes, and in addition is a magnificent target for anti-craft guns if kept at an altitude low enough for accurate observation. A large speed range is a desirable characteristic in such service.