Fighter Combat - Tactics and Maneuvering

4 FIGHTER WEAPONS
some firing ranges. The "lethal bullet density" was increased by a method
known as "harmonization," which generally involved using one of two
techniques.
"Point harmonization" aligned the outboard guns slightly toward the
aircraft centerline so that the bullets met at a point that was assumed to be
the optimum combat firing range (normally 700 to 800 ft). This method
resulted in maximum lethal density near this particular range, but led to
wide dispersion at much longer ranges. Point harmonization was often
preferred by the pilots who had the best marksmanship and were confident
they could place this maximum density point on target.
For most pilots, another method, known as "pattern harmonization,"
yielded better results. This involved adjusting each gun individually
slightly up, down, left, or right to produce a fairly uniform bullet pattern of
a certain diameter at the harmonization range. Although maximum lethal
density was not achieved in this manner, the average fighter pilot had a
better chance of getting hits. The advantages of this method were much
like those of a shotgun over those of a rifle. More lethal projectiles also
favored this technique, as maximum density usually was not necessary.
Mounting guns such that their line of fire does not extend through the
aircraft center of gravity (CG) introduces other problems. Particularly
when wing-mounted guns are located large distances from the CG, failure
of a gun to fire on one side can cause the aircraft to yaw significantly,
greatly complicating aim. Aircraft designed with asymmetrical gun
mounts often require some automatic aerodynamic control coordination,
such as rudder deflection, to compensate for these effects.
The recoil action of heavy, rapid-fire guns can be considerable and can
often cause significant speed loss for the firing aircraft. At slow speeds,
especially under asymmetrical firing conditions, this recoil can cause a
stall and subsequent loss of control.
With the advent of jet aircraft, one further complication has arisen to
the mounting of guns. The gun gases produced must be exhausted in such a
manner that they are not ingested by the engine, as this can cause compressor
stalls and flameouts.
The next significant technical breakthrough in air-to-air guns appeared
following World War II. This was a new cannon, modeled from an experimental
German gun and built around a rotating cylinder similar to a
"revolver" handgun. This design, known as the M39 in the United States,
resulted in a great increase in rate of fire.
Even greater performance was obtained in the late 1950s with the
introduction of the "Gatling-gun" cannon. Rather than a revolving cylinder,
this weapon employed multiple rotating barrels. Designated the M61
in the United States, this gun could develop a tremendous rate of fire with
less barrel overheating and erosion. Additionally, this gun was usually
electrically, hydraulically, or pneumatically propelled; because it was not
dependent on the residual energy of the expended round, problems associated
with duds were eliminated.
During the 1950s and 1960s there was a definite trend away from the