Convergence

Convergence is the practice, in Director Firing, of adjusting the training angle of the various turrets so that their firing is not parallel along the line of fire but instead converges on the targeted object.

Geometry

For any gun removed by a given base length along the centerline from the director on own ship, when firing on a target on a given relative bearing, the convergence correction will be:

convergenceAngle = arctan(sin(relativeBearing) * baseLength / range)

British Practice

The British director firing system calculated and applied convergence corrections in the Training Receivers. The design was fairly elegant, but each training receiver could only be made to work relative to one director^[Inference], and the operator had to provide the additional input of Gun Range. The instrument received its relative bearing input directly from the turret's orientation, and its base length from the director was reflected by the shape of spiral cams within the receiver.

See Also

• Dip

Bibliography

• Admiralty, Gunnery Branch (1917). The Director Firing Handbook. O.U. 6125 (late C.B. 1259). Copy No. 322 at The National Archives. ADM 186/227.