Minutes of Evidence
APPENDIX 2
Supplementary memorandum submitted by the Defence Procurement Agency 00-01/62
QUESTIONS 264 AND 306. BACKGROUND TO THE DECISION NOT TO EQUIP EUROFIGHTER WITH A GUN
7. Since the introduction of air-to-air missiles, a gun has been used in an air-to-air role for very close range engagements where the target was inside a short-range air-to-air missile's minimum range. Notably during the early years of the Vietnam war, the probability of kill in short-range engagements of the air-to-air missiles then available proved so low that the very modest capability of gun systems added significantly to overall effectiveness. The probability of success with guns has advanced little over the years[12]. By contrast, the performance of air-to-air missiles has improved dramatically. Indeed, in short-range engagements, the minimum range capability and agility of the missiles that Eurofighter will carry, together with its planned helmet-mounted sight targeting system, offers the pilot a shot with a very high probability of success in almost every conceivable situation. A gun could be seen as a defence of last resort when all the aircraft's missiles had been fired. However, even then the gun's usefulness would be severely limited because of the possibility of engagement by missile armed aircraft from well outside the gun's range.
8. Firing "warning shots across the bow" with a gun is not an effective means of coercion in modern operations. The cockpit environment of modern aircraft is such that the pilot is extremely unlikely to hear such warning shots and would only see them if they were tracer rounds. The value of such a display against a civilian aircraft is dubious and against a military aircraft it may well be misconstrued.
9. Against some threats, missiles may be susceptible to counter-measures employed by the opposing aircraft. However, ASRAAM has already proven itself against typical current countermeasure doctrines and is designed to overcome extreme levels of countermeasures. Even should an advanced hostile aircraft have decoyed Eurofighter's air-to-air missiles successfully, there is again little benefit in adding a gun to Eurofighter's armament. If the UK pilot were then to close on that hostile target to within the range of the gun, he would be placing the aircraft—and himself—at unnecessarily high risk of being shot down by the hostile aircraft's own missiles. Moreover, gun systems are not completely invulnerable to countermeasures, not least because most depend on accurate radar range
10. As for air-to-ground combat, it is worth noting that the original European Staff Requirement, signed by the Chiefs of Air Staffs from the partner nations in December 1985, specifies the gun only in an air-to-air role. So, even then, experienced airmen in the partner nations did not regard the gun as a valuable weapon for ground attack. It remains the view of experts that it is difficult to justify using the gun in Eurofighter's offensive support role, owing to:
- the risk of collateral damage resulting from the relative inefficiency of gun firing from a fixed-wing aircraft, especially in this age of precision-guided munitions, with which Eurofighter will be armed; and
- the increased vulnerability of the aircraft because the gun's short range would leave the aircraft very exposed to surface-to-air missiles and anti-aircraft gunfire.
11. Overall, therefore, it is clear that the utility of a gun on an aircraft such as Eurofighter in modern operations is questionable. To perform its roles effectively, Eurofighter's armament should emphasise not the very short-range capability that a gun would offer, but the long-range capability to be offered initially by the Advanced Medium-Range Air-to-Air Missile (AMRAAM). and later by the Meteor beyond visual range air-to-air missile.
12. The minimal combat value that the gun does provide is more than outweighed by the support, fatigue and training cost penalties of retaining it. Specific disadvantages of the gun include:
- the damaging effects of the shock of its recoil on the electronics (approximately 4 tons recoil shock 30 times a second);
- the corrosive effects of its exhaust gas;
- the strain which it puts on the airframe, reducing the aircraft's useful life. (Even the weight of 80kg of ammunition can add well over half a tonne load at the wing roots of the aircraft when it is subject to high gravitational pull in manoeuvre. Each aircraft has a finite design fatigue life. Using up this life much more rapidly would require us to purchase a greater number of aircraft or to undertake a life extension programme, the cost and operational penalties of which cannot be justified by the minimal operational benefits of the gun.); and
- a range of training costs, including the provision of new targets, the increased demands on the Hawk aircraft towing the targets (which must shortly be replaced by new aircraft), and the cost of removing training rounds from the environment.
13. We understand that our partner nations currently intend to retain the gun on Eurofighter. The American F-14, F-15, F/A-18 all have internal guns, though the F-117 does not; and the F-22 is planned to have one. The Russian MiG-29 and the Su-27/31 also have guns as do Gripen and Rafale. Some of these aircraft types entered service many years ago when missile technology was far less advanced. However, it is not currently planned to fit an internal gun to the Short Take-Off and Vertical Landing variant of Joint Strike Fighter (JSF), although it will be able to carry an externally mounted gun which can be put on and removed from the aircraft for particular missions.
14. Our assessment remains that, in the future operational roles for which we require Eurofighter, the minimal value of a gun is more than outweighed by its considerable associated costs and disadvantages.