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Aviation History
1950
1950 - 2106.PDF
FLIGHT, 7 December 1950 535 FIGHTER ^ ARMAMENT The Natter rocket-propelled irtter- cepter carried a battery of 30 R4/M rocket tubes in its nose, covered by a jettisonable cap : they were intended to be fired as a salvo into the target formation. Part V: Lessons from the Luftwaffe By A. R. WEYL, A.FR.Ae S RATIONAL design of a fighter aircraft centres on thepotential target. It is the latter which should formthe focus of attention for those formulating opera- tional requirements; on the shape, properties and habits of the flying targets to be defeated almost the whole of the technical specification should be based. Hence the very obvious need for technical and scientific intelligence- gathering and analysis. The sooner the target can be destroyed, the better for theintercepting defender: there is less danger from defensive armament, less chance of the enemy taking evasive action; lesswaste of ammunition; a better chance of surprise; more scope for dealing with other targets; and better " turn-over " of menand equipment. As carriers of weapons present-day high-speed jet fightersare handicapped at high speed and high altitude, for the air- craft ceases to provide a steady gun- or launching-platform.At present and future speeds the time of " meeting " the enemy in a position favourable for opening fire is exceptionally short,and there is rarely an opportunity to repeat an attack which has failed in its purpose. Flying at great altitudes, the enemyaircraft is difficult to spot (and to recognize) at long distances, unless it forms vapour trails. Finally, the radii in which inter-cepters are able to turn have vastly increased, so the manceuvrability necessary for taking aim has become muchreduced. It is, therefore, obvious that, as a carrier of weapons requiring accurate aim. the modern intercepter is grossly inferiorto the original fighter with which the history of air combat began. This is, indeed, the main argument which is put for-ward in favour of the guided air-to-air missile with homing devices. Its fallacy is, however, the fact that such devices,of necessity rather large and complicated, will remain more or less one-shot weapons of a rather unreliable character, com-parable with yet always inferior to the marine torpedo—which, so far, has conspicuously failed to supersede the naval gun. Logical Train of Deduction.—From assumptions as to where,when and how the flying target shall be met, and from the target's dimensions, vulnerability, mobility and defensive power,the immediate means of destruction which is needed, i.e., the type of projectile, can be deduced. In turn, the determinationof this factor, and consequently of whether one or many hits are necessary, leads the designer to find the appropriate kindof weapon and its calibre. Once the weapon (or weapon com- bination, or weapon battery) is selected, an assessment of itspositioning in respect to the target, its aiming, and the prob- ability of its producing hits under combat conditions will resultin a specification for the intercepter in its absolute quality as a carrier of the specified weapon. The aircraft specificationdius deduced must include provision for ammunition storage and the fuel to be carried. Only by such a logical and methodicalmanner of approach can the aircraft designer visualize die most efficient intercepter The time has long passed when an inter-cepter was merely a good aircraft, with effective speed and climb, into which some bright " lads from the Ministry" putany guns which happened to be lying about. Adopting die " splinter" hypothesis (see Part IV), the lethalcone or sphere is calculated from the minimum density of shell splinters which have sufficient kinetic energy and size to causedecisive damage. War is not primarily a business with the purpose of killing people, and nor is air combat: the aim isto enforce one's own will upon the enemy—in air combat, to down the enemy aircraft, and usually to do so in the shortest In the first part of this article (August 24th) Mr. Weyl reviewedthe history of aircraft armament and showed how lessons ol the past had, in his opinion, been neglected by those responsiblefor developing British equipment in the Second World War, in the second instalment (September 21st) he discussed Germanequipment; in Part III (October 5th) he analysed the respective claims of guns versus rockets; and on November 23rd he dis-cussed the effectiveness of various types of shells and fuses, and explained principles of elementary ballistics in their relationto air armament. In the present instalment he analyses Luftwaffe combat experiences, particularly with the use ofthe R.4/M air-to-air Rocket missile. possible time. It is open to tactical assessment to decide ifthis objective is to be achieved by " shot" or by " shrapnel," i.e., by applying several hits with one burst, or by a singlehit with a larger proiectile. The latter is, of course, the more modern way, and preferable. The decision yields, in turn, thetechnical limits for minimum shell-weight splinter-formation, and the H.E charge required to produce the splinters. Since the calibre length of a shell is a quantity within practicallimits, determined by inner and outer ballistic experience, the smallest applicable calibre is easily ascertained. The target'smobility (in relation to the attacker) and the sighting aids 'vhich are available permit assessment of the widest range over whichfire must be effectual. This, again, is a tactical deduction based upon appropriate intelligence and experience. The range andthe target's defensive abilities determine, technically, the desirable trajectory, i.e., they define the lowest admissiblemuzzle-velocity. From the probability of achieving hits on the basis of average burst-dispersion the requisite number of roundsto be fired can be calculated. Of these data, the calibre, the shell weight, the muzzle-velocity, and the rate of fire are funda-mental for the design of a gun which will meet the operational requirements. Similarly, if reliance is placed primarily on blast effect, theminimum quantity of a given kind of high explosive that will guarantee destruction has to be found. This quantity of H.Emay be applied either in a single projectile or by a number of simultaneous or quickly successive hits (bursts lasting up to,say, two seconds). From the percentage of probable hits, the H.E. volume required per shell determines the calibre, assuminga practical section-density.* Next it must be decided how such a " mine " shell may best be conveyed to the target: thismay be accomplished either over a long range at high trajectorial velocity, or over a short range at lower velocity but with greaterdensity within a burst. The argument of splinter v. blast in predominant effect uponthe target is closely related to the problem of optimum calibre For action by blast, greater calibre is not only necessary butpracticable in aircraft-gun design. This fact justifies the policy of calibre increase which characterized Luftwaffe development.Russian fighters, too, occasionally carried guns of 32 mm calibre i as early as the spring of 1942, and used them in air combat. Superiority in flying speed was formerly the principal charac-teristic of the intercepter. Nowadays the case is altered, for there is litde difference in speed between a jet bomber and ajet fighter This will remain true so long as the interceptor has to avoid transgression into the transonic speed regime (which,most probably, will exclude aimed fire for all practical pur- *Section-density—Projectile mass divided by its maximum cross-sectional area (see Part IV).
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