This is the first article of a series by former O.C. Flying at the Air Fighter Development Unit in which he will discuss the flying characteristics of modern aircraft.
During the war many types of fighter aircraft were produced out of the designers bag, some never even reached the prototype stage, others failed to reach Service requirements, but not a few made the grade and are now house hold words the world over. The best known in this country are, of course, the Hurricane and Spitfire, the Typhoon, Mustang and Thunderbolt, and latterly the Tempest and Meteor. Each came out in many guises and fulfilled many roles, some of which they were never designed for, but all did a grand job of work, and were at one time or another indispensable to the work of the R.A.F. Fighter Command.
What follows is intended to give the average non-technically minded reader some idea of how some of these aircraft compare with each other in the matter of performance and manoeuvrability. This is a big job and one which could fill the proverbial book, but in order to keep the subject within the limits of paper rationing and the readers interest, we shall deal with only five of these types namely, the Spitfire XIV, Mustang III, Tempest V, Thunderbolt II and Meteor III, although their performance in relation to other types, including the two best known major German fighters will be found in the accompanying diagrams.
In doing so each aircraft is compared as far as possible on the same basis, full war load but no external equipment such as bombs or r.p. Calculations for radius of action are, however, made with a compliment of external fuel tanks. These items, incidentally, are sometimes ignored by the well-meaning enthusiast who quotes maximum speeds of particular aircraft with complete disregard for the circumstances. Such quotations out of context can be very misleading to the layman, as external additions can account for 30-40 M.P.H. with the added disadvantage of a corresponding reduction in range and manoeuvrability.
The squadron pilot is sometimes the worst offender in this respect, as nothing delights him more than being able to prove that his squadron’s aircraft are superior in every respect to his rivals. In doing so, he commits a very forgivable sin and one, which only his unfamiliarity with another type can be blamed.
He is most naturally, far more concerned with what he can do with his own aircraft in the air, and his conviction that the Spitfire, for example is better than the Mustang is largely based on his own experiences. Moreover, his yardstick will be very different from a Mustang pilot, for example, who measures his aircrafts capabilities by its ability to carry out long range escort work, whereas a Spitfire pilot is more impressed by rate of climb and turning ability.
To build a fighter to meet every requirement is out of the question so, at best, every fighter is a compromise with emphasis on one particular quality. Speed may be sacrificed for range, and manoeuvrability for war load, depending on Service requirements and the role for which the particular design is expected to be suited. Generalization, therefore, is going to be difficult, but by making a comparison on “clean” aircraft at their individual rated altitudes considerable food for thought will materialize.
Comparison does not mean obtaining results from an indiscriminate dogfight between two fighter types, but a practical assessment of the information gained as a result of specific tests in specific circumstances. These circumstances are standardized by dividing the tests up into two categories, namely, Factual Comparison, which includes speed, rate of climb, range, endurance and acceleration, readily measured against the stop watch, and Competitive Comparison, such as turning circles, rates or roll and dive zoom climbs. Rates of roll an, of course be measured either way. The choice is a matter of opinion.
Altitude greatly affects the performance of aircraft, particularly its speed and climb, which means that comparison at any one height will give an erroneous impression of an aircrafts capabilities. A graphic presentation is, therefore, the only fair way of doing it, but for the purposes of this article we will take a selection of altitudes as shown in the diagram to illustrate the differences involved.
The Meteor III is the fastest of those depicted at all heights, followed by the Tempest V, up to 18,000ft when the Mustang III is slightly faster. Next comes the Spitfire, 30 mph slower than the Mustang III at sea level, but 10 mph faster at 30,000ft and nearly 30mph faster than the Tempest V at 25,000ft, which at sea level is 25mph faster than the Spitfire XIV. Finally comes the Thunderbolt II, easily bottom of the list at low altitudes but comfortably holding its own at 30,000ft.
Apart from the acknowledged superiority in this sphere of jet aircraft, therefore, it is not easy as some pretend it is to claim that any one particular fighter is the fastest, it probably isn’t. Providing it has a reasonable top speed; its other qualities are far more likely to make it a better fighter than the rest; speed is emphatically not everything.
First prize to the Meteor III.
To a lesser extent the same applies to rate of climb. Almost invariably the aircraft with the best power to weight ratio will have the best rate of climb. Here the Spitfire XIV comes into its own, followed by the Mustang III, the Tempest V and then the Thunderbolt II. This aircraft incidentally, is actually better than the Mustang and Tempest at around 28,000ft. The Meteor III does not show up quite so well, better than the Thunderbolt at low level, but slightly worse above 15,000ft.
First prize to the Spitfire XIV.
Basic design and operational requirements at the time of the original specifications are largely responsible for dictating the operational ceiling of an aircraft. By operational ceiling is meant, of course, the height at which the maximum rate of climb does not fall below 1,000 ft/min. It will be noticed that there is a comparatively large gap between the high altitude and the low altitude fighter. This is s it should be, and too much importance should not be attached to this quality, particularly for the low altitude fighter, as in all normal circumstances aircraft will be largely operated with a comfortable margin to spare.
First prize to the Spitfire XIV.
It is very difficult to arrive at a satisfactory and equitable method of measuring range and endurance on a common basis, but in order to compare one type with another, some sacrifice of individual performance must be made. Fuel consumption, capacity, throttle settings and altitude, particularly altitude, must all be taken into consideration. Detailed consideration of the method used is unnecessary, but it is important to have an appreciation of some of the major issues involved in arriving at accurate conclusions.
In all cases the range is given at the individual aircraft’s rated altitude, with full complement of drop tanks where applicable. Throttle settings are standardized in that five minutes are allowed for take-off at full power, climb at maximum throttle settings to rated altitude, five minutes combat at full throttle, 15 minutes at maximum cruising and the balance at economical cruising. This method is purely arbitrary, and should not be taken as representative of an operational sortie.
On these assumptions the Thunderbolt II and Mustang III easily head the list, followed by the Tempest V, Spitfire XIV and Meteor III. Comparison with the speed and rate of climb data shows how considerably the position of the aircraft is changed. The Mustang IV, incidentally, is even better than the Thunderbolt. The Spitfire XIV, which has no equal in the climb, is badly placed, whereas the Tempest V, one of the fastest fighter aircraft, is at something of a disadvantage for a really long-range sortie.
The superiority of the American aircraft is not so remarkable as it seems in that all the other aircraft were originally designed as interceptor fighters, and it was not until the later stages of the War, when offensive action became the major work of Fighter Command, that they had to be impressed.
First prize to the Thunderbolt II.
The ability to accelerate quickly is of paramount importance to fighters and the interceptor class has an obvious advantage in this respect. For comparative purposes it is impracticable to take into account maximum speed as acceleration is only operationally useful at the slower speeds when an interception suddenly has to be made from slow cruising.
For instance, the Tempest V, which is faster than the Spitfire XIV, takes less time to reach any given speed, but the Spitfire has the best acceleration, followed by the Mustang III, Tempest V, Thunderbolt and Meteor III. The unhappy position of the Meteor is accounted for by the natural sluggishness of early jets at the lower speeds. Here again, the power to weight ratio coupled with clean lines in design has considerable effect.
First prize to the Spitfire XIV.
In circumstances where the ability to turn quickly or tightly are infinitely variable, and where two aircraft are nearly the same, such as the Tempest V and Thunderbolt II, a great deal depends on the ability of the pilots. Speed must be taken into account if the results are going to be of any real value.
For example, if a Tempest dives on a Thunderbolt with an overtaking speed of only 50 mph, the Thunderbolt will easily be able to avoid the attack by turning, although at the same speed in the hands of equally competent pilots, the Tempest will outmanoeuvre the Thunderbolt. This advantage, however, is no by any means so apparent at high altitudes, due to the greater engine efficiency of the Thunderbolt above 25,000ft.
Similarly, where low-altitude and high-altitude fighters are compared any advantage shown by the former will be reduced as the high-altitude fighter gets nearer to its best operational altitude. After taking all these considerations into account, the position of the aircraft relative to each other will be seen from the diagram.
Once again, the Spitfire maintains top place, followed by the Mustang, Meteor, Tempest and Thunderbolt. Too much regard to this order should not be paid, particularly by the individual who will angrily recall the occasion when he out-turned a Meteor when flying his Tempest. This sort of thing is inevitable, but we can only repeat that where the circumstances are common to both aircraft, these positions are not far wrong.
First prize to the Spitfire XIV.
The ability to roll rapidly is vital to a fighter, and throughout the War continuous efforts were made to increase the rate of roll particularly at the higher speeds, where some aircraft tend to become unmanageable. Here again it is impossible to state categorically that any one particular type has the best rate of roll, as so much depends on the speed, and to a much lesser extent the altitude at which it is carried out.
For example, the Tempest V is not so good as the Spitfire between two and three hundred miles an hour, but above this speed, in common with the Thunderbolt it will out-roll anything, including the Thunderbolt, particularly at over 400mph. As will be seen from the diagram, the Meteor does not make a very good showing, and may cause some disappointment to jet enthusiasts. Far better results have been obtained from the Vampire class of jet and the Meteor IV.
First prize will have to be shared by the Spitfire and Tempest, depending on the speed at which the roll is executed.
Speed and acceleration in the dive is an essential quality to a successful fighter, but a decisive conclusion on the order of superiority is largely dependant on throttle settings, and the maximum speed in straight and level flight of the individual aircraft. Here again, however, by carrying out a number of tests under different conditions, it is reasonable to assume that the Meteor is well ahead of its rivals, followed by the Tempest, Thunderbolt, Mustang and Spitfire in that order.
Efficient streamlining and maximum speed both influence the dive, although a jet propelled aircraft will invariably have the advantage, particularly at the higher speeds, when the conventional fighter is progressively more handicapped by airscrew drag, and the accessory protuberances common to all conventionally powered fighters.
No account is taken in this order of Mach number limitations or altitude, as at around 500 mph the limitations imposed on the maximum permissible speeds for each type cause considerable change in the order, but it should be appreciated that these do not affect the diving qualities of the aircraft as opposed to maximum speed of which they are capable.
First prize to the Meteor.
The zoom climb is not so easy to assess. Duration of the dive, speed at the beginning of the dive, and throttle settings on the Zoom are amongst only a few of the problems that contribute to the difficulty of obtaining an equitable answer. Until some standard measurement of his quality has been generally agreed upon, the ability to zoom climb must remain one of the many bones of aeronautical contention.
That is the picture. What you make of it depends on the quality you consider most desirable in the modern fighter. Nobody has satisfactorily answered this question, but what ever you decide don’t try to sell it to a commercially minded test pilot, his aircraft invariably has just the qualities for which you have been looking.
The Aeroplane June 21st 1946.