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Aviation History
1953
1953 - 0736.PDF
730 The Canberra . . . predecessor, judging by the size of the bomb-bay; and if current American fighters can carry tactical atomic weapons, clearly so can a jet bomber. So, for that matter, could a Mitchell. All in all, therefore, great progress has been made in the years between the introduction of the two aircraft, and we now have a machine with nearly double the performance of the old which is none the less little more difficult to operate out of an adequate airfield, and which has superb power-plant reliability coupled with remarkable single-engined performance if one motor should for any reason be "lost." Everything cannot be gain, however, and against that we must offset the inability of all jet aircraft to hang- about low-down in bad weather, and the difficulty of applied instrument-nying under modern conditions. In this respect the Canberra pilot needs to reach and maintain a higher degree of skill than did his elder brother ten years ago. D.I.C. Production Testing THE Canberra is well-known for its versatility in combining high speed over great distances with manoeuvrability at high and low altitudes, in which respect it has been found more than a match for most fighter aircraft. These qualities are universally appreciated, but behind them— and far less publicized—is the fact that Canberras have been flowing out in large numbers from the factories to the Koyal Air Force during the past two years. This flow has necessitated further development of the existing organization for preparation, ground-testing, night-testing and despatch, because, although the largest part ot the night development of an aeroplane is completed in the extensive development testing of the first prototypes, it is always possible for defects to develop during assembly, or in ancillary equipment. Each production aircraft, therefore, needs careful testing over the whole of its performance range, followed by the correction of faults, before it is acceptable to the Ministry of Supply for delivery. It is not many years since even military aircraft were of sufficient simplicity as to necessitate their being flown only oace— or possibly twice—after rolling otf the production line and before being deemed in a fit state for delivery; but the range of speeds and altitudes to wnich the modern jet aircraft must be proved calls for considerably more Hying, and can naturally result in more minor defects which must be corrected and then re-checked inflight. In the case of the Canberra, it became apparent at an early stage that special provisions would need to be made to enable the test pilot to continue with flight-testing in adverse weather con ditions. Even as late as the last war, heavy bombers could be cleared after one or two short test nights round the airfield and below the cloud-base; but today a jet bomber must be tested to at least 45,000ft and dived to very high speeds. These conditions require either excellent flying weather, with little cloud and good visibility, or else some alternative aids to the pilot. For this reason Marconi AD.200 long-range V.H.F. direction-finding radio was installed at one of the English Electric Company's airfields, and, with its use, the test pilots have been able to continue production testing in weather which would otherwise have grounded them. In addition to die use of radio aids, a further change in test- flying practice has been needed in connection with weather res trictions, for although radio-homing enables the test pilot to take off, climb through cloud and carry out tests above cloud, with the sure knowledge that he can be brought back to base by radio bearings when he requires them, radio control does not help him in.testing where poor visibility is concerned. This can best be explained in the following terms. One of the most important phases of testing the Canberra— that of performance measurement—calls for hying level at full power at various points in the altitude range of the aircraft for long enough periods to stabilize the absolute maximum speeds. It naturally takes some minutes of flying at full throttle for an aircraft to settle down to its maximum speed at any given altitude and weight, and at the speeds of present-day jet aircraft very considerable distances are covered during these tests. For example, at the low end of the altitude range the maximum speed of a Canberra on production test has to be measured at 2,000ft. This condition is reached approximately four minutes after the beginning of the run, but during that time a distance of approxi mately 40 miles will have been covered. These and other trials at low and medium altitude are essential parts of the production test-schedule; so when, as frequently happens, weather conditions are only suitable for radio-controlled FLIGH1 flying at high altitude and, owing to mist, low cloud or smoke haze, quite unsuitable for these high speeds at the low altitudes, it has become necessary to develop the practice of using the speed-over-distance properties of the Canberra to fly in search of weather suitable for test purposes. This technique is quite at variance with established test-flying principles and tradition, as it has hitherto always been regarded as essential to remain within a 25-mile radius of the base aerodrome while carrying out test flights. With the Canberra, when weather conditions are unsuitable for specific tests in the Lancashire area, it is now the normal practice for the pilot to obtain weather information from various sources such as the local Airways Control Centre, other test pilots, or visiting pilots wbo have just landed; then he may set off for such areas as the East Coast from Newcastle to the Wash, the South Coast in the Isle of Wight- Portland area, or the North-West Coast from the Isle of Man to Glasgow—whichever seems to be most suitable. All these areas can be reached within half an hour by Canberra from Preston, and the necessary tests are then carried out whferevef suitable weather is found. The return flight W base is then made possible with safety in otherwise adverse weather con ditions by the Marconi radio homing equipment which can, and frequently do^s, st^er the aircraft back to the Preston area from more than 200 miles away. This type of operation, which might well be described as long- range test-flying, could not be carried out without increased risk to the aircraft if there were not adequate facilities for diversions or emergency landings near the areas selected for testing over. This aspect is covered by the radio-control networks and air fields of the British aircraft industry, in the London and South Coast regions; by the radio and airfield facilities of Bomber and Fighter Command on the East Coast; and by those of Main tenance and Coastal Command in the North-West. Thus, at no time during these flights, which frequendy cover more than 1,000 miles in two hours, are the Canberras out of range of adequate emergency radio and landing faculties. At first glance this may appear to be an undesirably complicated procedure, but in practice it has proved essential to the maintain ing of a steady flow of these jet bombers from the production line through the night-testing and acceptance stage to delivery to the Royal Air Force; and it is significant that the unusually inclement weather of the winter of 1952-3 has not resulted in any major interruptions of Canberra delivery. Apart from this weather question, and the measures taken to overcome it, there have been no unusual features in the general testing of production Canberras, as the type is a simple, straight forward and even docile aeroplane, lacking complication in its flying characteristics; the only factors which render its flight- testing in any way unusual are those of its performance. After some years of continuous work on it, test pilots still find it a strange experience to be flying well above 40,000ft, 200 to 300 miles from their base airfield, so soon after take-off. Re-equipping the R.A.F. On the Service side, it might be expected that Bomber Command would have re-equipped with Canberras at a rate roughly similar to the manufacturers' production rate, but initially this has not been so, for the following reasons. When the first prototype flew in 1949 there were no jet aircraft, in this country or elsewhere in the world, which were capable of flying continuously at altitudes gready in excess of 40,000ft for many hours at a time. Until then, all practical experience of flying at these heights had been limited to short-duration flights with jet- and piston-engined air craft at their absolute ceiling limits. By the end of 1949 there were many experimental and research establishments of the Air Ministry, the Ministry of Supply, and also of the aircraft industry, which were seriously hampered in their attempts to keep pace with the development of equipment for high-altitude flight by the lack of suitable aircraft in which to test it. So it came about that, as soon as the Canberra had proved its capabilities, the Ministry of Supply had very pressing reasons for diverting early Canberras to these establishments for high- altitude flight research. Because of this, by the time Bomber Command had received their first three squadrons of Camberras, a similar number of these jet bombers was already being employed on vital research work, in connection with the present generation of high-altitude, high performance military aircraft. Now, however, Canberra B.2s have been flowing to the Royal Air Force at a steady rate for many months. In this initial year of Service experience, much useful information has been accumu lated in the operation of their new jet bomber and, wherever possible, this information leads to modifications to the production fine so that the aircraft continues to be improved to meet the Services' changing requirements. During this re-equipment, Bomber Command had to face one of the biggest changes of maintenance, training, and operational philosophy in Service history, when, at a stroke, the piston-
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