This appears to be the latest model of mechanical antiaircraft director made by the Japanese. It has data receivers (selsyns) for azimuth, angle of site, and slant range, probably provided for use with radar equipment. Primary input data may also be obtained by optical tracking by means of telescopes attached to the director and a height finder.
Computation is based on angular rates. The transmitted data is future azimuth, future quadrant elevation, and future fuze. Data is transmitted to each weapon by means of selsyn motors and applied to the weapon by means of a match pointer system resembling that used with the American 90 mm, M1 antiaircraft fire control equipment. It is believed that this instrument is capable of furnishing data for three weapons. It is assumed the azimuth receiver will work with both the 8 cm and the 12 cm Japanese antiaircraft guns.
As compared with th her modern directors, it is felt that this instrument is deficient in both design and construction. An angular rate computer is considered too inaccurate for anything other than small or medium caliber automatic tracer controlled antiaircraft fire. Human error is permitted through the curve-following method of introducing time of flight, superelevation, and converting slant range into altitude. A great deal of backlash exists in various gear trains and in the mechanical linkage of the multipliers.
SPECIFICATIONS
| Limits as indicated by drums and dials | ||
| Slant range (dial calibration) | 40,000 meters | |
| Slant range (limit of movement w/ alt. converter) | 19,000 meters | |
| Horizontal range | 12,500 meters | |
| Altitude | 9,000 meters | |
| Quadrant elevation | -10° to + 90° | |
| Fuze | 35 seconds | |
| Dead fuze time | 10 seconds | |
| Wind velocity | 20 meters/sec. | |
| Azimuth | No limit | |
| Angular rate | Undetermined | |
| Electrical data | ||
| Cycles | 50 or 60 | |
| Volts | 50 or 60 | |
| Weapon with which used | 120 mm, 45 cals. A.A. gun and 80 mm, 40 cals. A.A. gun. | |
| Characteristics | ||
| Height | 44 1/4 ins. | |
| Length | 34 1/2 ins. | |
| Date of manufacture | Showa 18 (1943) | |
| Weapon data obtained from drums | ||
| Fuze types (120 mm gun) | M88 (1928), M89 (1929), M91 (1931) | |
| Muzzle velocity | 825 meters/sec. | |
| Fuze types (80 mm gun) | M89 (1929), 5th year type (1930) | |
| Muzzle velocity | 670 meters/sec. |
Japanese: p. 176 (March 1, 1945)