Flying Triangles
I By OLIVER STEWART DELTA-WING aircraft carried the richest implications at the Society of British Aircraft Constructors' Flying Display and Exhibition at Farnborough this week. There were many other events of importance, such as the appearance of the big Saunders-Roe Princess flying-boat and the demonstrations of supersonic flying and of entirely new engines; but the delta-wing aircraft conjured up fascinating pictures of future possibilities. Two of these machines were seen by the public for the first time at Farnborough, the Gloster Javelin all-weather fighter, and the Avro 698 bomber. Both expressed vividly the essential characteristics of the delta configuration, and it is upon these characteristics that the future of the delta will be founded. They may be summarised thus : smooth, low-drag exterior envelope; low wing-loading; control simplicity; spacious interior accommodation. These arise from the triangular shape. Perhaps the dominant feature is the good .thickness-chord ratio, that is to say the thin- ?less of the wing in relation to its chord, or width from front to rear. Thickness-chord ratio goes with sweep-back to determine whether a wing is suitable for driving through the air at speeds near the speed of sound, or at speeds of the order of 600 to 650 miles an hour at heights of ten or twelve thousand metres. tf the triangular-plan form is studied it becomes apparent at once that in the delta the two seeming incompatibles are com- bined: the "thin" wing and the great-width and depth of wing near the centre line or body. It was this paradox of the delta Configuration that was -so well illustrated by the Avro 698 and the Gloster Javelin at.Farnborough.
These two aircraft must carry a vast amount of military equipment. The bomber must have room for an enormous bomb-load, the fighter must have room for all the radar and pother special automatic fighting equipment that has recently been developed. By using the delta shape room can be found for all these things without spoiling the aerodynamic smooth- ness of the machine. Thus in the bomber the four big Rolls- Royce Avon turbojet engines are completely buried in the wing roots, and yet bigger engines could be fitted without spoil- ing the exterior shape. And the inner parts of the wings of both aircraft are sufficiently large to accommodate the immense quantities of fuel demanded by ever-thirsty gas-turbines.
With this primary advantage, that there can be good thick- ness-chord ratio with roomy interior, there goes a secondary advantage. It is apparent to the eye without calculation or study of the dimensions that the delta configuration gives a low wing-loading; there is a large expanse of wing area for the total weight. Low wing-loading means a short take-off run and a short landing-run. It may also, in certain circum- stances, mean improved powers of manoeuvre at height. And finally there is simplicity of control. Here the new Avro bomber is the example, for the Javelin has a horizontal tail- 'plane. The bomber has no horizontal tailplane. It has a vertical fin and rudder only. And its control-surfaces for pitch and roll are simply parts of the trailing edge of the wings. In the middle is the elevator, in two sections, and out near the wing-tips are the ailerons. There are no wing-flaps nor-are they needed, because of the low wing-Loading. All this means that the delta configuration is the shape of the future. The aero- plane as we have known it since the beginning of flight, with body, wings and tail, will soon be obsolescent. For all high- speed flying the shape will be triangular.
If that is a true reading the importance to British manu- facturers is great. For they have proceeded farther with the development of delta aircraft than any others. Avro have been most persistent in this work—a tribute should be paid here to their test-pilot Wing Commander Falk—and have, as it appears, made the greatest progress. But other makers like Gloster, Fairey and Boulton Paul have worked on the delta and assembled a good deal of information about it. In the United States and in Sweden delta aircraft have been flown, but no large-size delta aircraft has appeared anywhere but in Britain, and the evidence is that our design-teams are now the- best- informed in this field.
Then there is the Saunders-Roe Princess flying-boat. This has ten Bristol Proteus turboprops, or gas-turbines driving air- screws, and is the largest passenger aircraft in the world. (I exclude the Hughes flying-boat because it has done no real flying.) The Princess with Proteus 2 engines as now fitted can work at an all-up weight of 1421 metric tons. When the Proteus 3 engines are fitted, which they will be as soon as they are ready, the weight will go up to 1561 metric tons. This compares with the all-up weight of the Brabazon at 132 metric tons.
The Princess is a courageous challenge to those who have decried flying-boats. It may yet prove that for very large-size aircraft we must turn to these machines. They can offer many advantages to the countries of a Commonwealth linked by oceans. They are almost certainly safer than land-planes, they do not make heavy demands on agricultural land for their runways, nor do they cause the kind of troubles that are now being experienced at the big airports, where people living in the district are continually bombarded by the noise of engines. The water runways are always and inevitably farther away from built-up areas than the land runways.
At present the intention is- to store the two other Princess flying-boats, both nearly complete, until engines can be released for them from duties which are considered to be " more impor- tant." Here the Ministry of Supply would do well to take stock of the situation. It might be worth while giving the other two Princess flying-boats their engines as a matter of priority. We in Britain must strive with all our might to derive the fullest benefit from the advanced thinking and courageous progressive- ness of our aircraft-construction companies. With three Prin- cesses flying the merits' of the big boat could be thoroughly tested. And they ought to be tested without delay.
The new Olympus turbojet made by Bristol was shown in an English Electric Canberra. Its rated thrust is 9,750 lb. but I have been at Bristol and watched the engine being ruin on the bench at a continuous rating of over 10,000 lb. It is probably the most powerful turbojet anywhere. And an important feature is that it is a " two spool ' engine with a high compres- sion ratio and a small overall diameter. It is only 40 inches in diameter—a slimmei engine therefore than some giving far less power.
Finally I would like to pay a small tribute to the test-pilots who did the flying at Farnborough. It was my duty on the guest-days to do the commentary from the top of the control tower and I found the quality of the flying a continual source of pleasure. The aircraft were beautifully demonstrated by men who were masters of their art.
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