JVur»iri. Lead angle, aerial target.
T63. General a. The gunner Has no sighting devices for setting initial leads on the machinegun, cal .60, HB, M2, or on mount M68. The discussion in this section presents the magnitude of leads in antiaircraft firing.
6. Prior to opening fire, the gunner estimates the amount his gun will lead the target This estimate is based upon an understanding of the mag nitude of the lead required under varying conditions of target speed, target range, and angle of approach. For example, a target, traveling 600
milea per hour, flies a crossing course that causes it to pass at a midpoint range of 460 meters from the gun position. To hit the aircraft at this midpoint, the gunner aims and fires his weapon at a point on the target course line 165 meters ahead of the target (The time of flight for a caliber .50 round for a range of 460 meters is 0.6 second. A speed of 600 miles per hour is approximately 275 meters per second. During the time of flight of the projectile, the target will have traveled 0.6 x 275 or 165 meters.) Using the mil relation rule, with a range of 460 meters and 165 meters as the distance traveled by the aircraft, the lead required to hit the target at midpoint is 860 mils.
c. Lead for specific midpoint ranges may be calculated on the basis of target speed. For a midpoint range of 460 meters, the midpoint lead required is 60 mils or 27 meters for each 100 miles per hour of target speed. The length of the target is a convenient unit of measure in establishing initial leads. The estimated lead is divided by the length of the target to determine the number of apparent target lengths which the gunner ^111 lead the target. Midpoint leads expressed in meters, mils, and apparent target lengths for selected targets, target speeds, and midpoint ranges are contained in figure 172.
164. Effect of Angle of Approach on Lead a. As the angle of approach increases up to midpoint, the amount of lead necessary also increases. When the target passes midpoint and continues on the receding leg, the amount of lead decreases, while the angle of approach continues to increase. The amount of lead necessary at mid
MIDPOINT LEADS (BASED UPON FT 0.50 -H- 1)
AVERAGE LENGTH AIRCRAFT (METERS)
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