Rockets fuzed with proximity fuzes may function prematurely if fired too close to trees or other intervening objects. There should be at least 250 feet clearance from objects short of the target.

The proximity fuze detonates the warhead at a distance from the target to produce optimum blast effect. It is essentially a radio transmitting and receiving unit and requires no prior setting or adjustment. Upon firing, after the minimum arming time, the fuze arms and continually emits radio waves. As the rocket approaches the target, the waves are reflected back to the fuze. The reflected waves produce a beat. When received by the fuze with a predetermined intensity, as on approaching close to the target, this beat operates an electronic switch in the fuze. This permits electric current to flow through an electric squib, initiating the explosive train and detonating the rocket. Proximity fuzes for rockets are of two types-one for ground-type rockets, the other for aircraft-type rockets. Proximity fuzes are physically interchangeable with other standard fuzes in ground-type rockets having deep fuze cavities.

c. The PIBD fuze detonates the rocket on impact with the target. The fuze consists of a nose assembly and a base assembly connected by a wire passing through a conduit in the rocket head. Pressure of impact on a piezoelectric crystal in the nose assembly generates a surge of electricity. This is transmitted to a low-energy detonator in the base assembly, detonating it. Some PIBD fuzes have a graze-sensitive element which will actuate the fuze if impact does not initiate the piezoelectric crystal.

d. Boresafe rocket fuzes are those in which the explosive elements are so separated as to prevent explosion of the warhead before the rocket leaves its launcher. Explosion is prevented even if the more sensitive elements (primer or detonator) should accidentally function.

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