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Aviation History
1944
1944 - 0290.PDF
148 FLIGHT FEBRUARY IOTH, 1944 THE WORLD'S BEST AIRCRAFT will want simplicity of construction so that it is easy to build. Thus, in assessing an overall "quality factor" we must take account of all requirements—which will vary according to the purpose of operation. Obviously, too, some factors are more important than others, and figure most prominently in the design. These are the qual ities which have been termed the " major factors" in setting out the 22 categories required: defence and range for the day bomber, bomb load and range for the night bomber, and so on. So far the problem is relatively straightforward. Now we come to the more detailed and the more complicated procedure. The thing to bear in mind is that we are attempting to make a fair and impartial assessment of the world's best aircraft in each of the categories specified—the aircraft best fitted to the job in hand. The principle is to compare the known perform ance and other qualities of each aircraft under review, against the best attainable in each particular. The approach should be made in a spirit of how much can be gained out of the formula in the way of eradicating biased opinion, and in checking judg ment and not in the spirit of how much one can outwit it and promote freaks. In this way some most interesting results can be gained and I belie\ e the method is reasonably foolproof. After much experiment and detailed thought on the subject, the most satisfactory sequence of assessment appears to work out as follows: — 1. Split the aircraft under review into their essential .categories. 2. Define the requisite qualities in each category from the points of view of C.-in-C, air crew, ground crew and production engineer. 3. Compare only like with like. Thus the Mosquito should not be assessed against the Clipper as a trnus- ocean transport, though both have flown the Atlantic. Nor should the FwifiO be assessed against the Lancaster as a night bomber, though both have been used for this purpose. 4. Compare only on a basis of consistent figures. Thus if a range is quoted with external fuel tanks the speed must be quoted for the machine equipped with the tanks, and so on. In making the detailed calculations 1 have been able to draw on restricted figures for various aircraft whose exact performance may not be published yet. Naturally those figures cannot be quoted here. If that puts into the estimate of results something of the atmosphere of the patent medicine whose prescription is a professional secret, then I must ask forgiveness and plead the unfortunate result of inevitable and essential wartime restriction. Never theless the results can be reached without telling the enemy any unknown facts because there are so many "unknowns" in each individual assessment that even the most brilliant German mathematician could not chase the missing "x"s. A "quality factor" of, say, 85 per cent, for the Spitfire IX could in no way reveal the exact top speed or rite of climb. Major Factors As a 'detailed example of the method of assessing the "quality factor" for any given aircraft, let us analyse the figures for an aircraft cl 1939, where all the relative qualities are known and can be quoted freely. The same methods are applied to today's aircraft, except that the optimum figures of 1939 are exchanged for those of 1943-44. ' As the illustration iet us take the Messerschmitt Me 109E single-seat dog-fighter (1939) for operation at low and medium heights. We proceed as follows: but low on other counts, would be unduly penalised, and vice- versa. In each category the major factors are those in which real superiority is required if the aircraft is to be any good. There fore the major factors should be assessed separately and, by a logical course, given twice the weight of any of the sub sidiary factors, thereby assuring that an aircraft with poor major factors, but superior subsidiary factors, will not be assessed unduly high. The procedure then becomes: 1. Determine and assess the major factors. 2. Determine, add up and average the subsidiary factors. 3. Add major factors plus major factors again, plus average of the sum of subsidiary factors and then take average for result. An Example Applying this procedure to the example of the Me 109E we see that the two major factors work out as 98 per cent, and 45.8 per cent. The average of the sum of the subsidiary factors works out as 63.5 per cent. Thus we have from (3) the sum, 98 per cent, plus 98 per cent, plus 45.8 per cent, plus 45.8 per cent, plus 63.5 per cent. ; all divided by five. The result— the quality lactor—thus works out as 70.2 per cent, for the Me 109E on the standards of 1939 One or two points require clarification. Fire-power is calcu lated on the basis of " muzzle horse-power" (see Flying, July, 1943, page 66). The maintenance factor is an effort to assess ease of servicing *r Major Factors 1. Max. speed at 15,000 ft. £ Manoeuvrability factor (wing-loading) SUBSIDIARY FACTORS 3. Duration (50 per cent. power) 4. Initial climb ... 5. Firepower <;. Maintenance factor ... 7. Production factor 8. Vulnerability factor ... Best of 1939 362 m.p.h. (Spitfire). 14.7 lb./ft.' (Gladiator). 4.2 hrs. (Severskv P-35) 4,800 ft./min. (CW-21) 616 m.h.p. (Hurricane) 16 (Curtiss Hawk " 75 ") 5,100 man hrs. (Gladiator) 3.0 (Hurricane) Me109E Figure 354 m.p.h. 32.1 lb./ft.» 2.4 hrs. 3,100 ft./min. 491 m.h.p. 11 6,600 1.0 MC109E Per cent, of bett 08.0 45.8 57.1 64.6 79.8 68.7 77.5 33.3 So much for the percentage calculations. But the mere addi tion and averaging of the percentages is not enough. By that means an aircraft supreme in the major factor for its category, Although given pride of place in the list of heavy night bombers, the Hercules engined Avro Lanchester II is only awarded 75.2 per cent, of marks. on a known background. A fair arrangement seemed to be to award points on the following system: Single-engine = four points ; Air-cooled engine = three points; Metal-stressed skin construction = five points; Wood-stressed skin => three points; Metal, fabric-covered = two points; Wood, fabric-covered = no points; ~<K Fixed undercarriage = two points; Fixed-pitch airscrew = two points ; General maintenance reputation=four points. Thus, from the point of view of maintenance the maximum possible points would be 20, equivalent to 100 per cent. The same general principle has been applied to gain a vul nerability factor. A maximum of ten points can be gained for the following contributions towards low vulnerability: Armour plate = up to two points, Protected fuel tanks = up to three points; Multi-engines = up to three points; Air-cooled motors = one point; General layout = one point. In practice this procedure and these details seem to give a fair appraisal of qualities. Applying these methods to the 22 categories against a standard of the highest obtainable figures of 1943-44, ano^ varying the desirable qualities to suit the demands made upon the different classes of aircraft, we arrive at the final result. Each category of aircraft is assessed on at least two major factors and not less than five—and sometimes as many as seven—subsidiary factors, which include all those shown in the Me 109E example and also bomb load, ceiling, climb at 20,000ft., defensive power emphasising turrets), -_ range, ton-miles per gallon and payload for a given range. i In the assessment of the world's best aircraft on this basis, only aircraft which are in operational service and about which general details may be published have been included for selec tion. Nevertheless, some of the "ideals" for 1944 have been
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