Best dogfight gun?

Since this bit of the thread has drifted into whether or not a gun
should be fitted at all, these are my thoughts on the matter, from
'Flying Guns: the Modern Era' by Emmanuel Gustin and myself, due to be
published in March next year. First, in air-to-air use:

"Modern short-range missiles have minimum ranges as low as 300 m, well
within gun range, and are highly agile, with wide engagement
envelopes, which make them able to hit targets well off to one side of
the firing aircraft, especially when cued by a helmet-mounted sight:
in fact, the capabilities of most recent models are such that the
aircraft carrying them barely need to manoeuvre. This does not mean
that guns are useless for air-to-air work. They have a particular
value in modern 'policing' applications, as they enable warning shots
to be fired in front of suspect aircraft. They also provide an
economical way of engaging low-value targets such as unmanned
reconnaissance drones, transport and liaison aircraft, or
drug-smugglers. In a 'hot' war they still have certain advantages in
close-quarter fighting, for example in 'picking off' an enemy
attacking a wingman, who may be too close for a safe missile shot. The
ability of modern fighters to adopt extreme attitudes, pointing well
away from the line of flight, significantly assists gun aiming in
dogfights. Cannon projectiles have a shorter flight time than a
missile, a significant advantage in a dogfight.

Finally, the gun provides a last-ditch capability if the missiles run
out, or are defeated by advanced countermeasures or simply by
circumstances. The 1991 Gulf War revealed the deficiencies of modern
IR-homing missiles when faced with trying to pick up a low-flying
target against a hot desert background (helicopters being in any case
difficult for IR seekers to lock on to from above). USAF A-10
aircraft achieved two helicopter kills with the GAU-8/A (using 275 and
550 rounds respectively) in one case when the IR missiles failed to
lock on. Furthermore, the performance of even the best missiles cannot
always be guaranteed, for various reasons. In Kosovo, a US fighter
engaging a Serbian plane needed to fire three AMRAAMs to bring it
down. In other engagements in the late 1990s, USAF and USN fighters
fired a total of seven Sparrows, AMRAAMs, and Phoenix missiles against
Iraqi MiG-25s without scoring a single hit (although the Phoenix shots
were taken at extreme range).

In part, the low success rates are due to tactical considerations, in
that missiles may deliberately be launched outside the normal
engagement envelope to distract or scare off the enemy, and sometimes
two missiles are launched at one target to increase the hit
probability. Whatever the reason, this results in missiles being used
up at a high rate, making it more likely that they will run out during
a sortie. A cannon will typically carry enough ammunition for several
engagements, usefully increasing combat persistence at a minimal cost
in weight and performance.

One curious aspect to the use of AAMs in combat is that of the
approximately 1,000 kills achieved between 1958 and 1991, only a
handful were scored beyond visual range, which does raise questions
about the significance of the very long ranges of which some missiles
are capable. It is sometimes argued that modern short-range missiles
are so good that any aircraft with the benefit of long-range sensors
and missiles should use them to try to stay outside the envelope of
the enemy's short-range AAMs. However, it is not always possible to
dictate the terms of an engagement. The Iranians made good use of the
long-range AIM-54 in the war with Iraq, but the F-14s which carried it
still found themselves engaged in gunfights from time to time.

There is a continual battle between missile sensor and countermeasure
technology. In the future, stealth technology applied to aircraft may
considerably shorten target acquisition and combat ranges, putting
into question the worth of modern BVR (beyond visual range) AAMs. The
possible future use of anti-radar missile guidance as a way of
overcoming stealth characteristics may force fighters to make minimal
use of their own radars, further reducing acquisition and combat
distances. It may also prove increasingly difficult for either IR or
radar-homing missiles to lock on to their stealthy targets,
additionally protected by extensive electronic jamming and IR
countermeasures.

Of course, modern guns are usually aimed by the plane's radar which
could also be jammed (although less easily than the much smaller and
less powerful missile seekers) but laser rangefinders could make an
acceptable alternative in providing fire control data. If planes
eventually become 'laser-proof' as well, the possibility presumably
exists of linking variable magnification optical sights to a computer
which would be able to analyse the image, identify the plane,
calculate its distance, speed and heading and provide gunsight aiming
information accordingly, all without emitting any signals."

And in ground attack:

"The emphasis in the use of aircraft guns has now shifted more to
air-to-ground work, although even this is becoming increasingly
hazardous in a 'hot' war. With the proliferation of anti-aircraft gun
and missile systems, including MANPADS, even the specialist
ground-attack aircraft, fitted with powerful cannon, have found it to
be safer to rely on the long range of their air-to-ground guided
weapons rather than close to gun range, although as we have seen the
USAF's A-10s still made good use of their cannon against Iraqi targets
in 1991.

This trend is aided by the continued development of air-to-surface
missiles, with the latest ones having autonomous homing systems to
provide "fire and forget" capability over long ranges. Another current
development is the GD Advanced Precision Kill Weapon System, which
aims to achieve low-cost accuracy by fitted a laser homer to the
little 2.75 inch (70 mm) rocket. The target is to achieve a CEP of 1 –
2 m at ranges of up to 5 – 6 km at a price of US$ 8 – 10,000;
one-sixth the cost of a Hellfire anti-tank missile.

However, not all conflicts involve front-line opposition; in fact,
armed forces are now commonly engaged on police work, frequently
dealing with guerrilla forces. In these circumstances, rockets and
missiles may represent an inappropriate degree of destruction, with a
high risk of collateral damage. The RAF was embarrassed during
operations against insurgents in Sierra Leone in 2000 to find that
they had no suitable weapon for their gunless Harrier GR.7 aircraft to
attack small groups of rebels operating close to innocent civilians.
Another advantage of using cannon was demonstrated in the invasion of
Afghanistan in 2002. During an intense infantry battle at Takur Ghar
in late May, in which US forces were ambushed and in considerable
danger, air support was called for. The AC-130 was not permitted to
intervene in daylight due to its vulnerability, so USAF fighters were
sent to help. For a part of the battle the Afghan combatants were too
close to the Americans for rockets or bombs to be used, so the
fighters – F-16s and even F-15s – went in strafing with their 20 mm
cannon, as did the Navy's F-14s and F/A-18s on other occasions. Even
RAF Tornadoes were reported to have carried out gun strafing runs on
at least one occasion. It may logically be argued that it is foolish
to risk an extremely expensive aircraft, with its expensively trained
pilot, to being lost due to very low-tech ground fire, but sometimes
the risk needs to be taken to save friendly lives."

The case rests...

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum:
http://forums.delphiforums.com/autogun/messages/